EHP Library Malaria Bulletin, Dec 4 - Jan 4, 2001

Full Text Articles/Reports

Roll Back Malaria News - December 2000

WHO Bulletin - Malaria Theme Issue, Dec 2000

Social Sciences and Malaria 

1  Bull World Health Organ 2000;78(11):1352-7

Malaria in the United Republic of Tanzania: cultural considerations and health-seeking behaviour.

Oberlander L, Elverdan B

Department of General Practice, Institute of Public Health,|| University of Southern Denmark, Odense, Winslowparken 19, DK-5000 Odense C,|| Denmark.

Malaria is one of the biggest health problems in||| sub-Saharan Africa. Large amounts of resources have been invested to control||| and treat it. Few studies have recognized that local explanations for the||| symptoms of malaria may lead to the attribution of different causes for the||| disease and thus to the seeking of different treatments. This article||| illustrates the local nosology of Bondei society in the north-eastern part of||| the United Republic of Tanzania and shows how sociocultural context affects||| health-seeking behaviour. It shows how in this context therapy is best viewed||| as a process in which beliefs and actions are continuously debated and||| evaluated throughout the course of treatment.

2  J Commun Dis 2000 Mar;32(1):49-53

Impact assessment of IEC campaign during anti-malaria month,  June 1998 through KABP study.

Sharma SN, Saxena NB, Phukan PK, Anjan JK, Pandya AP, Lal S

Regional Office of Health & Family Welfare, Anmedabad.

To assess the IEC Campaign during anti malaria month (June, 98), a base line KABP study through pre-assessment and post-assessment was conducted in the State of Gujarat (four districts namely Ahmedabad, Dang, Panchmahal and Baroda). The study was carried out based on questionnaire (open and closed) developed by NAMP in the randomly selected population. A rapid assessment of the current level of KABP among a sample of population before and after the observance of anti-malaria month. The results of the KABP study revealed that there is definite impact (between 2.18 to 30%) and change in the KABP of the local people, where intensive and continuous I.E.C. activities are being undertaken. In order to achieve the desired change in knowledge, attitude, behaviour and practice of the respondents, it requires continuous I.E.C. campaign throughout the year. The attitude, behaviour and practice in the hard core areas need special efforts, where maximum efforts are required to bring a change in. It should be taken more intensively in the problematic and hardcore areas on priority basis.

3  Southeast Asian J Trop Med Public Health 2000 Jun;31(2):225-37

Status of malaria in Thailand.

Chareonviriyaphap T, Bangs MJ, Ratanatham S

Division of Biology, Faculty of Liberal Arts and Science, Kasetsart University, Nakhon Pathom, Thailand. Email: [email protected]

Despite decades of control success and a competent network of country-wide health infrastructure, malaria remains an important health threat in rural Thailand. All 4 known human malaria parasites have been reported present, with Plasmodium falciparum and Plasmodium vivax predominant. The expansion and intensity of multi-drug resistant Plasmodium falciparum is the most serious development to occur the last several decades. Members of 3 anopheline species complexes, Anopheles dirus, Anopheles minimus, and Anopheles manculatus, are considered to be primary malaria vectors in the country. Representatives within all 3 taxa are difficult or impossible to separate morphologically from one another, and insufficient information exists about population genetics between sibling species and vector status. Vector control in Thailand has been the primary means of malaria control, mainly by the use of routine residual insecticide spray inside houses. The use of DDT in vector control has resulted in measurable successes to interrupt malaria transmission in many parts of the country. Since 1949, DDT has been the predominant compound used: however, its public health use has continued to decline as a result of perceived operational difficulties, political issues and environmental concerns. The increased use of pyrethroids to impregnate bednets and for intradomiciliary spraying are generally more accepted by rural populations and are rapidly replacing the use of DDT. Organized malaria control activities have reduced malaria morbidity from 286/1,000 population in 1947 to 1.5/1,000 population by 1996. Despite encouraging trends in dramatically reducing malaria, the rates of disease may be re-emerging in the country as evidence from an increased annual parasite index from 1.78/1,000 in 1997 to 2.21 in 1998. The possible reasons for the apparent increase in incidence are discussed in terms of the technical, operational and social obstacles in malaria control in Thailand.

4  Trans R Soc Trop Med Hyg 2000 Jul-Aug;94(4):367-71

Risk factors associated with malaria infection in an urban setting.

Mendez F, Carrasquilla G, Munoz A

Instituto de Salud del Pacifico (INSALPA), Buenaventura, Colombia.

Incidence of malaria in urban settings is a growing concern in many regions of the world and individual risk factors need to be identified to appropriately adjust control strategies. We carried out a cross-sectional study in 1993/94 in an urban area of the largest port of the Pacific Coast of Colombia, where transmission has had an upward trend over the past 5 years. Prevalence of malaria infection was estimated in areas of the city with the highest incidence of disease, and the association between some characteristics of the population and the risk of malaria infection was assessed. Prevalence of malaria infection was 4.4% among the 1380 studied people and we found that it decreased with older age, and with knowledge of disease and preventive measures directed to elimination of breeding sites. In addition, the infection was positively associated with exposure to the forest (P < 0.05), although most of the cases (57/61, 93%) were likely to have been acquired in the urban area. We also found that individuals receiving antimalarial treatment in the previous month had around twice the risk of being infected as compared with those without treatment. In addition, our results suggest that use of bednets could not be a very effective protective measure in settings such as that of our study, and that environmental interventions may be needed to decrease the risk of infection.

5  Trop Med Int Health 2000 Nov;5(11):755-64

Using evidence to change antimalarial drug policy in kenya.

Shretta R, Omumbo J, Rapuoda B, Snow RW

Kenya Medical Research Institute/Wellcome Trust, Collaborative Programme, Nairobi, Kenya; National Malaria Control Programme, Ministry of Health, Nairobi, Kenya; Centre for Tropical Medicine, Nuffield Department for Clinical Medicine, Uni.

Chloroquine resistance was first detected in Kenya in 1978 and escalated during the 1980s. Chloroquine remained the treatment of choice for uncomplicated malaria infections until revised guidelines were launched in 1998 despite a plethora of scientific evidence on failure. This review analyses the range and quality of the evidence base that was used to change the drug policy in Kenya from chloroquine to SP and examines the process of consensus building and decision making. Our review illustrates the difficulties in translating sensitivity data with gross geographical, temporal and methodological variations into national treatment policy. The process was complicated by limited options, unknown adverse effects of replacement therapies, cost, as well as limited guidance on factors pertinent to changing the drug policy for malaria. Although > 50% of the studies showed parasitological failures by 1995, there was a general lack of consensus on the principles for assessing drug failures, the inclusion criteria for the study subjects and the relative benefits of parasitological and clinical assessments. A change in international recommendations for assessment of drug efficacy in 1996 from parasitological to clinical response further perplexed the decisions. There is an urgent need for international standards and evidence-based guidelines to provide a framework to assist the process by which decision-makers in malaria-endemic countries can make rational choices for antimalarial drug policy change.

6  Health Policy (Ireland) 17 NOV 2000, 54/2 (143-159) 

Economic burden of malaria illness on households versus that of all other illness episodes: A study in five malaria holo-endemic Nigerian communities 

Onwujekwe O.; Chima R.; Okonkwo P. O. Onwujekwe, Health Policy Research Unit, Dept. of Pharmacology/Therapeutics, University of Nigeria, PMB 01129, Enugu Nigeria 
Email: [email protected]

We compared the financial and economic costs of malaria attack to that of a combination of other illness episodes on households in five malaria holo-endemic rural communities. The data was collected from household heads or their representatives using pre-tested interviewer-administered questionnaire. Information was collected on the amount of money household spent to treat both malaria and other illnesses respectively, together with the time lost due to both the groups of illnesses within 1 month prior to the interview. The findings showed that the cost of treating malaria illness accounted for 49.87% of curative health care costs incurred by the households. Average malaria expenditure was $1.84 per household per month, while it was $2.60 per month for the combination of other illness episodes. The average person-days lost due to malaria and the combination of other illnesses were almost equal. If the financial costs of treating malaria and other illnesses are combined, this cost will deplete 7.03% of the monthly average household income, with treatment of malaria illness alone depleting 2.91%. Thus, malaria is a big contributor to the economic burden of disease, in malaria holo-endemic communities. Community-effective malaria control programs are needed to reduce this burden on the households. (C) 2000 Elsevier Science Ireland Ltd.

PubMed, December 4, 2000 - January 4, 2001

 
Clin Diagn Lab Immunol 2001 Jan;8(1):14-20
Naturally Acquired Antibody Responses to the C-Terminal Region of Merozoite Surface Protein 1 of Plasmodium vivax in Korea.

Park JW, Moon SH, Yeom JS, et al.

Korean Armed Forces Central Medical Research Institute, Yusong-gu, Daejeon, Chongno-gu, Seoul 110-744, Republic of Korea.

We expressed a protein in Saccharomyces cerevisiae in order to evaluate the humoral immune responses to the C-terminal region of the merozoite surface protein 1 of Plasmodium vivax. This protein (Pv200(18)) had a molecular mass of 18 kDa and was reactive with the sera of individuals with patent vivax malaria on immunoblotting analysis. The levels of immunoglobulin M (IgM) and IgG antibodies against Pv200(18) were measured in 421 patients with vivax malaria (patient group), 528 healthy individuals from areas of nonendemicity (control group 1), and 470 healthy individuals from areas of endemicity (control group 2), using the indirect enzyme-linked immunosorbent assay (ELISA) method. To study the longevity of the antibodies, 20 subjects from the patient group were also tested for the antibody levels once a month for 1 year. When the cutoff values for seropositivity were determined as the mean + 3 x standard deviation of the antibody levels in control group 1, both IgG and IgM antibody levels were negative in 98.5% (465 of 472) of control group 2. The IgG and IgM antibodies were positive in 88.1% (371 of 421) and 94.5% (398 of 421) of the patient group, respectively. The IgM antibody became negative 2 to 4 months after the onset of symptoms, whereas the IgG antibody usually remained positive for more than 5 months. In conclusion, indirect ELISA using Pv200(18) expressed in S. cerevisiae may be a useful diagnostic method for vivax malaria.

Korean J Parasitol 2000 Dec;38(4):263

Comparative study on longevity of Anopheles sinensis in malarious and non-malarious areas in Korea.

Ree HI, Hwang UW

Institute of Tropical Medicine and Department of Parasitology, Yonsei University College of Medicine, Seoul 120-752, Korea. Email:  [email protected]

An outbreak of vivax malaria has been occurring in northern part of Kyonggi-do and north-western part of Kangwon-do, where are located near the demilitarized zone, since 1993. For understanding of epidemiological features of malaria, the probability of daily survival of Anopheles sinensis, the vector species of malaria was compared in malarious and non-malarious areas in July-August, 2000. Total 915 females collected at three locations in malarious areas were dissected for ovaries, and 64.6% of the parous rate was found. Total 758 females collected at three locations in non-malarious areas were dissected, and 57.8% of the parous rate was observed. It was estimated from the parous rates that the probability of daily survival of An. sinensis females was 0.864 in malarious areas and 0.850 in non-malarious areas, which was not significantly different.


Mol Phylogenet Evol 2000 Dec;17(3):430-436

A Phylogenetic Study of the Anopheles punctulatus Group of Malaria Vectors Comparing rDNA Sequence Alignments Derived from the Mitochondrial and Nuclear Small Ribosomal Subunits.

Beebe NW, Cooper RD, Morrison DA, Ellis JT

Molecular Parasitology Unit, University of Technology, Sydney, New South Wales, 2065, Australia

A phylogenetic study of the members of the Anopheles punctulatus group was performed using structural and similarity-based DNA sequence alignments of the small ribosomal subunit (SSU) from both the nuclear and the mitochondrial genomes. The mitochondrial SSU gene (12S, approximately 650 bp) proved to be highly restricted by its secondary structure and displayed little informative sequence variation. Consequently, it was considered unsuitable for a phylogenetic study of these closely related mosquito species. A structural alignment of the nuclear ribosomal DNA SSU (18S, approximately 2000 bp) proved to be more informative than similarity-based alignments. Analyses showed the A. punctulatus group to be monophyletic with two major clades; a Farauti clade containing members displaying an all-black-scaled proboscis (A. farauti 1-3 and 5-7) and the Punctulatus clade containing members displaying extensive white scaling on the apical half of the proboscis (A. farauti 4, A. punctulatus, and An. sp. near punctulatus). Anopheles koliensis was positioned basal to the Farauti clade. Copyright 2000 Academic Press.

10  Trans R Soc Trop Med Hyg 2000 Sep-Oct;94(5):557-62

Immune response to Plasmodium falciparum liver stage antigen-1: geographical variations within Central Africa and their relationship with protection from clinical malaria.

Migot-Nabias F, Deloron P, Ringwald P, et al.

Centre International de Recherches Medicales de Franceville (CIRMF), Gabon. Email: [email protected]

Two populations of schoolchildren from Gabon and Cameroon were tested in 1995 for their immunological reactivity to synthetic peptides (LSA-Rep, LSA-J and LSA-CTL) from Plasmodium falciparum liver stage antigen-1 (LSA-1). The prevalence and levels of both cellular (lymphocyte proliferation, tumour necrosis factor alpha (TNF alpha), interferon gamma (IFN gamma), and interleukin-10 (IL-10)) and humoral (immunoglobulin G) responses were determined. Protection from clinical malaria, determined after a prospective 1 year study in both sites, was associated with elevated proliferative responses to LSA-Rep and LSA-CTL in the Gabonese children, as well as with higher antibody levels to both schizont extract and LSA-Rep. The prevalence of peptide-stimulated TNF-alpha secretion was higher in the Cameroonian group, but higher levels of antibodies to LSA-Rep and LSA-J were found in the Gabonese children. The immunological differences observed between children in the 2 study sites are discussed in the context of both epidemiological and individual host factors.

11  Trans R Soc Trop Med Hyg 2000 Sep-Oct;94(5):549-53

Intermittent sulfadoxine-pyrimethamine in pregnancy: effectiveness against malaria morbidity in Blantyre, Malawi, in 1997-99.

Rogerson SJ, Chaluluka E, Kanjala M, Mkundika P, Mhango C, Molyneux ME

Wellcome Trust Research Laboratories and Malaria Project, College of Medicine, University of Malawi, Blantyre, Malawi. Email: [email protected]

Plasmodium falciparum malaria in pregnancy predisposes to maternal and foetal morbidity. In 1993 Malawi adopted intermittent presumptive therapy with sulfadoxine-pyrimethamine (SP) as malaria prophylaxis for all pregnant women. To assess operational effectiveness of SP, we examined (in 1997-99) the relationship between number of doses of SP prescribed in antenatal clinic and indicators of malaria infection and morbidity at delivery, including peripheral and placental parasitaemia, maternal and neonatal anaemia, and birthweight. Among Malawian women delivering in a large urban hospital, SP prescription was associated with a decrease in placental malaria prevalence (from 31.9% with no SP prescription to 22.8% with > or = 2 doses SP) and density, decreased prevalence of low birthweight (from 23% in women not receiving SP to 10.3% in women given > or = 2 doses), and higher maternal haemoglobin concentrations. These effects were most marked in first and second pregnancies, in which malaria prevalence was highest. Maternal and cord blood malaria prevalence and mean cord blood haemoglobin concentrations did not differ with SP usage. Implementation of the SP administration policy was incomplete: 24% of women were not prescribed any SP, and only 30% were prescribed at least 2 doses as recommended. Intermittent presumptive treatment with SP is having a positive impact on some, but not all indicators of malaria infection and morbidity in Malawi. Improved implementation and continued surveillance are essential.

12  Trans R Soc Trop Med Hyg 2000 Sep-Oct;94(5):545-8

Artemether-lumefantrine for the treatment of multidrug-resistant falciparum malaria.

van Vugt M, Looareesuwan S, Wilairatana P, McGready R, Villegas L, Gathmann I, Mull R, Brockman A, White NJ, Nosten F

Shoklo Malaria Research Unit, Mae Sod, Thailand.

The efficacy and safety of the 6-dose regimen of artemether-lumefantrine were assessed in an open randomized trial in children and adults presenting with acute, uncomplicated Plasmodium falciparum malaria in Thailand between November 1997 and March 1998. 200 patients were enrolled in 2 centres: 150 received artemether-lumefantrine (i.e., a median total dose of 9.6 mg/kg [interquartile range 8.7-10.7] and 57.9 mg/kg of lumefantrine [52.4-64.0]) and 50 the standard combination of artesunate (12 mg/kg over 3 d) and mefloquine (25 mg/kg). All patients had rapid initial clinical and parasitological responses. The 28 d cure rates were high: 97.7% (95% confidence interval [95% CI] 93.5-99.5%) for artemether-lumefantrine and 100% (95% CI 92.5-100%) for artesunate-mefloquine. The 6-dose regimen of artemether-lumefantrine was better tolerated than, and as effective as, artesunate-mefloquine, the current standard treatment in this area of multidrug-resistant P. falciparum malaria.

13  Trans R Soc Trop Med Hyg
2000 Sep-Oct;94(5):537-44

Plasmodium falciparum antimalarial drug susceptibility on the north-western border of Thailand during five years of extensive use of artesunate-mefloquine.

Brockman A, Price RN, van Vugt M, Heppner DG, Walsh D, Sookto P, Wimonwattrawatee T, Looareesuwan S, White NJ, Nosten F

Shoklo Malaria Research Unit, PO Box 46, Mae Sot 63110, Tak, Thailand.

Following a marked decline in the efficacy in vivo of mefloquine between 1990 and 1994, a combination of artesunate (4 mg/kg/d for 3 d) and mefloquine (25 mg/kg) has been used as first line treatment of uncomplicated falciparum malaria in camps for displaced persons located along the north-western border of Thailand. Antimalarial drug susceptibility of fresh isolates of Plasmodium falciparum from this population was evaluated using a radioisotope microdilution assay between 1995 and 1999. In total, 268 isolates were collected, of which 189 were from primary infections and 79 from recrudescent infections. The geometric mean 50% inhibitory concentration (IC50) values from primary infections were: dihydroartemisinin 1.2 ng/mL, artesunate 1.6 ng/mL, artemether 4.8 ng/mL, atovaquone 0.4 ng/mL, lumefantrine 32 ng/mL, chloroquine 149 ng/mL, quinine 354 ng/mL, mefloquine 27 ng/mL and halofantrine 4.1 ng/mL. A significant positive correlation was found between the susceptibility in vitro to artesunate and quinine (r = 0.43, P < 0.001), mefloquine (r = 0.46, P < 0.001), and halofantrine (r = 0.51, P < 0.001). These levels of resistance in vitro are among the highest reported and confirm continuing high level multidrug resistance in this area. Despite intensive use of the combination between 1995 and 1999 there has been a significant improvement in mefloquine sensitivity (P < 0.001) and artesunate sensitivity (P < 0.001). This supports observations in vivo that the combination of artesunate and mefloquine has reversed the previous decline in mefloquine sensitivity.

14  Trans R Soc Trop Med Hyg 2000 Sep-Oct;94(5):477-83

Anaemia in pregnant Ghanaian women: importance of malaria, iron deficiency, and haemoglobinopathies.

Mockenhaupt FP, Rong B, Gunther M, Beck S, Till H, Kohne E, Thompson WN, Bienzle U

Institut fur Tropenmedizin, Medizinische Fakultat Charite, Humboldt Universitat zu Berlin, Germany. Email: [email protected]

In sub-Saharan Africa, anaemia in pregnancy results from multiple causes including malaria, iron deficiency and haemoglobinopathies. In a cross-sectional study among 530 pregnant women in Ghana in November-December 1998, red blood cell indices were analysed with respect to malaria, serum concentrations of ferritin and C-reactive protein (CRP), and the haemoglobin and alpha-globin genotypes. Anaemia (haemoglobin [Hb] < 11 g/dL) was found in 54% of the women; 63% harboured malaria parasites at predominantly low numbers. Ferritin levels were considerably influenced by malaria and inflammatory processes (CRP > 0.6 mg/dL). Depending on the definition applied, the prevalence of iron deficiency ranged between 5% and 46%. The HbAS trait was observed in 14%, HbAC and elevated HbF in 7% each, and sickle cell disease in 1%. Heterozygous beta-thalassaemia was present in 1% of the women and alpha(+)-thalassaemia in 33% (29% heterozygous, 4% homozygous). Women with HbAS had higher malaria parasite densities than those with HbAA. In individuals with highly elevated HbF (> 10%), parasitaemia occurred in 27% only. Low gravidity, second trimester of pregnancy, malaria, raised CRP levels, and homozygous alpha(+)-thalassaemia were independent risk factors for anaemia in multivariate analysis. alpha(+)-Thalassaemia, however, was associated with a lesser degree of malarial anaemia when compared to non-thalassaemic women. Iron deficiency appears not to be a major health problem in this population. Haemoglobinopathies are common but, except for homozygous alpha(+)-thalassaemia, do not substantially contribute to anaemia in pregnancy. alpha(+)-Thalassaemia ameliorates malarial anaemia in pregnant women.

15  Trans R Soc Trop Med Hyg 2000 Sep-Oct;94(5):472-6

Estimates of the infectious reservoir of Plasmodium falciparum malaria in The Gambia and in Tanzania.

Drakeley CJ, Akim NI, Sauerwein RW, Greenwood BM, Targett GA

MRC Laboratories, PO Box 273 Fajara, The Gambia. Email: [email protected]

Separate studies carried out in Farafenni, The Gambia and Ifakara, Tanzania in 1990-94 provided comparative data on population age structure, population gametocyte prevalences and gametocyte carrier infectivity. The percentage of the population estimated to be infective to mosquitoes was 5.5% and 3.8% in The Gambia and Tanzania, respectively. The age groups 1-4 years, 5-9 years, 10-19 years and 20 years or more comprised 17.5%, 21.7%, 22.2% and 37.9%, respectively, of the infectious population in The Gambia; the corresponding figures for Tanzania were 30.9%, 25.2%, 15.7% and 28.1%. These figures are in broad agreement with those from other published studies which estimated the infectious reservoir directly and suggest that adults contribute significantly to the infectious reservoir of malaria, particularly in areas of intense seasonal transmission. Control measures aimed at reduction of transmission may have only a limited effect in areas of moderate seasonal transmission if directed only at children.

16  Med Vet Entomol 2000 Dec;14(4):445-9

Disappearance of malaria vector Anopheles sundaicus from Chilika Lake area of Orissa State in India.

Dash AP, Hazra RK, Mahapatra N, Tripathy HK

Regional Medical Research Centre, Bhubaneswar, India. Email: [email protected]

Malaria has declined around Chilika Lake (85 degrees 20'E, 19 degrees 40'N) in Orissa State, India, from hyperendemicity in the 1930s to hypoendemicity during recent decades. Six decades ago, 21 spp. of Anopheles mosquitoes (Diptera: Culicidae) were recorded from this area, including the well known Indian malaria vectors An. culicifacies Giles, An. fluviatilis James, An. maculatus Theobald, An. stephensi Liston and An. sundaicus (Rodenwaldt), the last formerly regarded as the main vector locally. Surveys of Chilika area during 1995-96 found 8 spp. of culicine plus 14 spp. of anopheline mosquitoes, the latter comprising An. subpictus Grassi sensu lato, An. hyrcanus (Pallas) s.l., An. vagus Donitz, An. annularis van der Wulp s.l., An. culicifacies Giles s.l., An. aconitus Donitz, An. varuna Iyengar, An. barbirostris van der Wulp s.l., An. philippinensis Ludlow, An. ramsayi Covell, An. jeyporiensis James, An. pallidus Theobald, An. tessellatus Theobald and An. karwari James in decreasing order of abundance. Among indoor-resting female mosquitoes, the anthropophilic index was 4-7% and some species (An. culicifacies, An. subpictus, An. vagus) tended to enter houses for resting after blood-feeding outside. Females of potentially infective age (three-parous) were obtained for An. culicifacies (11%) and An. annularis (<2%), the more abundant established vector in this coastal area, but not for small samples of An. subpictus and An. vagus. Anophelines reported previously but not found in our survey were An. fluviatilis, An. jamesii Theobald, A. maculatus, An. splendidus Koidzumi, An. stephensi, An. theobaldi Giles and the former main vector An. sundaicus.

17  Med Vet Entomol 2000 Dec;14(4):441-4

Efficacy of three insect repellents against the malaria vector Anopheles arabiensis.

Govere J, Durrheim DN, Baker L, Hunt R, Coetzee M

Mpumalanga Department of Health, Nelspruit, South Africa.

Three commercial repellents marketed in South Africa: Bio-Skincare (BSC, oils of coconut, jojoba, rapeseed and vitamin E), Mosiguard towelletes with 0.574 g quwenling (p-menthane-3,8-diol, PMD) and the standard deet (15% diethyl-3-methylbenzamide, Tabard lotion), were compared against a laboratory colony of the mosquito Anopheles arabiensis Patton (Diptera: Culicidae), the predominant malaria vector in South Africa. Human forearms were treated with 1.2 g BSC, 0.8 g PMD towelette or 0.5 g deet and exposed to 200 hungry An. arabiensis females for 1 min, at intervals of 1-6 h post-treatment. Tests were conducted by three adult male volunteers (aged 30-45 years, crossover controlled test design for 3 consecutive days), using their left arm for treatment and right arm for untreated control. Biting rates averaged 39-52 bites/min on untreated arms. All three repellents provided complete protection against An. arabiensis for up to 3-4 h post-application; deet and PMD gave 90-100% protection up to 5-6h, but BSC declined to only 52% protection 6h post-treatment. These results are interpreted to show that all three repellent products give satisfactory levels of personal protection against An. arabiensis for 4-5 h, justifying further evaluation in the field.

18  Med Vet Entomol 2000 Dec;14(4):369-75

Diversion of Anopheles gambiae from children to other hosts following exposure to permethrin-treated bednets.

Quinones ML, Drakeley CJ, Muller O, Lines JD, Haywood M, Greenwood BM

Medical Research Council Laboratories, Fajara, Banjul, The Gambia. 
Email: [email protected]

Permethrin-treated bednets reduce mortality and morbidity from malaria in Gambian children. However, it is not certain how this effect is achieved, as neither mosquito numbers nor the human blood index of indoor-resting female Anopheles gambiae Giles sensu lato (Diptera: Culicidae) mosquitoes have been reduced when treated bednets were introduced into a community. One possibility is that insecticide-treated bednets divert mosquitoes from children to adults. To investigate this hypothesis, a cross-over trial with insecticide-treated bednets was undertaken in two small Gambian villages. To differentiate mosquitoes that had fed on children from those that had fed on adults, all children in the study villages were immunized with rabies vaccine before the trial. Using the detection of rabies antibody in a bloodmeal as an indicator that a mosquito had bitten a child, it was found that the percentage of blood-fed mosquitoes caught indoors that had bitten a child fell significantly from 30.8% to 9.2% and from 28.0% to 6.9% in each village after insecticide-treated bednets were introduced. To investigate the possibility that some diversion to animals had occurred, a PCR analysis for human beta-globin DNA was undertaken on selected samples. The results of this investigation were confusing, as some rabies-antibody positive bloodmeals were negative for human DNA. This may have been due to cross-reacting antibodies in animal sera and/or DNA degradation by digestion in the mosquito. Although good evidence for diversion of mosquitoes away from children was obtained, it remains uncertain whether diversion was mainly to adult humans, to animals or to both.

19  Med Vet Entomol 2000 Dec;14(4):345-54

Cost-comparison of DDT and alternative insecticides for malaria control.

Walker K

American Association for the Advancement of Science Fellow, US Environmental Protection Agency, Washington DC, USA.  
Email: [email protected]

In anti-malaria operations the use of DDT for indoor residual spraying has declined substantially over the past 30years, but this insecticide is still considered valuable for malaria control, mainly because of its low cost relative to alternative insecticides. Despite the development of resistance to DDT in some populations of malaria vector Anopheles mosquitoes (Diptera: Culicidae), DDT remains generally effective when used for house-spraying against most species of Anopheles, due to excitorepellency as well as insecticidal effects. A 1990 cost comparison by the World Health Organization (WHO) found DDT to be considerably less expensive than other insecticides, which cost 2 to 23 times more on the basis of cost per house per 6 months of control. To determine whether such a cost advantage still prevails for DDT, this paper compares recent price quotes from manufacturers and WHO suppliers for DDT and appropriate formulations of nine other insecticides (two carbamates, two organophosphates and five pyrethroids) commonly used for residual house-spraying in malaria control programmes. Based on these 'global' price quotes, detailed calculations show that DDT is still the least expensive insecticide on a cost per house basis, although the price appears to be rising as DDT production declines. At the same time, the prices of pyrethroids are declining, making some only slightly more expensive than DDT at low application dosages. Other costs, including operations (labour), transportation and human safety may also increase the price advantages of DDT and some pyrethroids vs. organophosphates and carbamates, although possible environmental impacts from DDT remain a concern. However, a global cost comparison may not realistically reflect local costs or effective application dosages at the country level. Recent data on insecticide prices paid by the health ministries of individual countries showed that prices of particular insecticides can vary substantially in the open market. Therefore, the most cost-effective insecticide in any given country or region must be determined on a case-by-case basis. Regional coordination of procurement of public health insecticides could improve access to affordable products.

20   Parasitology 2000 Nov;121 Pt 5:465-71

Commitment to the production of male and female gametocytes in the human malaria parasite Plasmodium falciparum.

Silvestrini F, Alano P, Williams JL

Laboratorio di Biologia Cellulare, Istituto Superiore di Sanita, Rome, Italy.

Commitment to the production of female and male gametocytes was studied in the NF54 line of the human malaria parasite Plasmodium falciparum. The development of sibling parasites derived from individual schizonts was followed, and 2 antisera against the female gametocyte-specific protein Pfg377 and the male gametocyte-specific protein alpha-tubulin II were used to determine the sex of sibling gametocytes. The experiment showed that individual cohorts of sibling gametocytes were stained in a mutually exclusive fashion by only one or the other antiserum, indicating that individual schizonts committed to yield sexual parasite progeny produce gametocytes of the same sex. This work suggests that in P. falciparum commitment to sexual differentiation occurs prior to schizont maturation, at the same moment when the sex of the resulting gametocytes is determined.

21  Southeast Asian J Trop Med Public Health 2000 Jun;31(2):238-45
Treatment of uncomplicated Plasmodium falciparum malaria in Myanmar: a clinical decision analysis.

Cho-Min-Naing, Saul A

Malaria and Arbovirus Unit, Queensland Institute of Medical Research, Brisbane, Australia. 
Email: [email protected]

This study was undertaken to compare cost-effectiveness of three drug regimes for treatment of uncomplicated falciparum malaria in Myanmar. The alternative regimens in this study were chloroquine (CQ), sulphadoxine-pyrimethamine (SP) and mefloquine (MFQ) along with their therapeutic efficacy in Myanmar. The study was performed by modeling a clinical decision tree based on a hypothetical 1,000 adult uncomplicated falciparum malaria cases. Key variables were (i) three drug regimes: CQ, SP and MFQ, (ii) three categories of therapeutic efficacy of each drug: adequate clinical response (ACR), early treatment failure (ETF) and late treatment failure (LTF) according to the 1996 WHO protocol, and (iii) compliance with each drug. In structuring the model, necessary assumptions were made. The cost effectiveness was measured as cost per case cured and cost per case prevented death related to the provided drug, from the provider's perspective. According to the present price and therapeutic efficacy, SP is the most cost effective drug for a case cured in all three categories of efficacy (US$ 0.12 per case cured in ACR, US$ 0.38 per case cured in ETF and US$ 0.54 per case cured in LTF). For a case prevented death, CQ is most cost effective in all three categories (US$ 0.58 per case prevented death in the ACR, US$ 2.14 per case prevented death in the ETF and US$ 2.51 per case prevented death in the LTF). The lowest cost effective regimen is MFQ for both indicators of effectiveness at the present price and therapeutic efficacy. A sensitivity analysis was performed for sensitive values.

22  Southeast Asian J Trop Med Public Health 2000 Jun;31(2):219-24

Malaria outbreak in a tribal area of Gujarat state, India.

Srivastava HC, Yadav RS

Malaria Research Center (ICMR), Field Station, Civil Hospital, Nadiad, Gujarat, India. 
Email: [email protected]

Malaria incidence in Gujarat state had been on a general decline since 1989. However in some tribal villages in forested areas of Valsad district, southern Gujarat, there was an outbreak of malaria in September 1995. Five children died in Ashlona village. During investigation conducted in October 1995 in affected villages, the malaria parasite rate was 26% (217/833) with >91% infections due to P. falciparum. A high proportion of P. falciparum infections had ring stages suggesting active transmission. Against a minimum norm of 10% annual blood examination rate, there was a major breakdown of active surveillance for malaria. In the absence of health agencies in or near affected villages, the malaria parasite load continued to build up leading to an outbreak towards the end of monsoon season. Indoor residual spraying with deltamethrin caused significant reduction in densities of malaria vector An. culicifacies. Measures to prevent malaria outbreaks in inaccessible areas have been discussed.

23  Trans R Soc Trop Med Hyg 2000 Jul-Aug;94(4):419-24

An integrated assessment of the clinical safety of artemether-lumefantrine: a new oral fixed-dose combination antimalarial drug.

Bakshi R, Hermeling-Fritz I, Gathmann I, Alteri E

Novartis Pharma AG, Basle, Switzerland. Email: [email protected]

Artemether-lumefantrine (A-L), a new fixed-dose oral antimalarial drug, combines the fast onset of action of artemether (an artemisinin derivative) in terms of parasite clearance with the high cure rate of lumefantrine in the treatment of acute uncomplicated Plasmodium falciparum malaria. The extensive clinical trial database of A-L has allowed a comprehensive evaluation of its tolerability and safety in a total of 1869 patients (including 243 children aged 5-12 years and 368 children aged < 5 years). The most commonly reported and possibly related adverse effects following A-L therapy involved the gastro-intestinal (abdominal pain, anorexia, nausea, vomiting, diarrhoea) and central nervous (headache, dizziness) systems. Pruritus and rash were reported by < 2% of patients. More than 90% of the reported adverse events, many of which overlapped considerably with the clinical symptomatology or evolution of acute malaria, were rated mild to moderate in intensity. Compared to A-L, significantly higher incidences of vomiting and pruritus were observed with chloroquine, dizziness, nausea and vomiting with mefloquine, somnolence with pyrimethamine + sulfadoxine, and vomiting and dizziness with quinine. There were no serious or persistent neurological side-effects related to A-L administration. A-L did not lead to any clinically relevant alterations of the laboratory parameters. Serial electrocardiographic data were available for 713 patients. The frequency of QT interval prolongations was similar to or lower than that observed with chloroquine, mefloquine, or artesunate + mefloquine; these changes were considerably less frequent than with quinine or halofantrine. All patients with QT prolongation remained asymptomatic and no adverse clinical cardiac events were reported. Artemether-lumefantrine can thus be expected to show, both in children and in adults, a favourable safety profile for the treatment of acute, uncomplicated, P. falciparum malaria; it could as well be a reserve treatment option for travellers to endemic countries.

24  Trans R Soc Trop Med Hyg 2000 Jul-Aug;94(4):413-8

Chloroquine prophylaxis, iron-folic acid supplementation or case management of malaria attacks in primigravidae in western Uganda: effects on maternal parasitaemia and haemoglobin levels and on birthweight.

Ndyomugyenyi R, Magnussen P

Vector Control Division, Kampala, Uganda.

The effects of weekly chloroquine prophylaxis, daily iron-weekly folic acid supplementation or passive case management on maternal haemoglobin and parasitaemia and on birthweight were examined in primigravidae in a randomized, double-blind placebo-controlled intervention trial in 1996-98 in Hoima District, western Uganda. Iron-folic acid supplementation significantly increased mean birthweight as compared to case management (P = 0.03). Low birthweight (< 2.5 kg) occurred in 2% of babies of women receiving chloroquine prophylaxis for > or = 8 weeks and in 9% in the case management group (RR = 0.36, 95% CI 0.13-1.00, P = 0.009). Parasitaemia at enrolment significantly correlated with low birthweight in the case management group as compared to the intervention groups (P = 0.02). Women in the case management group who were parasitaemia and had haemoglobin levels < 100 g/L at delivery had babies with lower mean birthweight as compared to babies in the other groups (P = 0.04). Low haemoglobin level at enrolment, irrespective of parasitaemia status, was a predictor of low birthweight in the case management group only (P = 0.04). Chloroquine prophylaxis and iron-folic acid supplementation significantly increased maternal haemoglobin levels during pregnancy as compared to case management (P = 0.01 and 0.007, respectively) and the increase correlated to the duration of the intervention.

25  Trans R Soc Trop Med Hyg 2000 Jul-Aug;94(4):399-403

Impact of subpatent multi-species and multi-clonal plasmodial infections on anaemia in children from Nigeria.

May J, Falusi AG, Mockenhaupt FP, Ademowo OG, Olumese PE, Bienzle U, Meyer CG

Institut fur Tropenmedizin und Medizinische Fakultat Charite, Humboldt-Universitat zu Berlin, Berlin, Germany. Email: [email protected]

Childhood anaemia in sub-Saharan Africa is often caused by Plasmodium falciparum malaria. The influence of subpatent, multi-species and polyclonal infections with malaria parasites on haematological parameters was assessed in 1996/97 in clinically healthy children in Nigeria. Of the 228 children studied, 64% were anaemic by the WHO age-dependent criteria. A univariate analysis of risk factors indicated that the prevalence of anaemia was dependent on the number of Plasmodium species detected by species-specific PCR (P < 0.0001). Furthermore, the prevalence of anaemia increased gradually with the complexity (P < 0.003) as well as with the extent of P. falciparum parasitaemia (P < 0.0001). A logistic regression analysis revealed that individuals with an enlarged spleen tended to be anaemic. The number of Plasmodium species by which an individual was infected was independently associated with anaemia (P < 0.03). ANOVA revealed that the age-corrected values for haemoglobin (Hb) and red blood cells (RBCs) were mainly influenced by the occurrence of mixed infections. Haematological parameters were also influenced by the number of different P. falciparum clones by which an individual was infected. Hb levels and RBC counts were further diminished by additional infections with P. malariae and/or P. ovale. However, the effect of multi-species infections on haematological parameters exceeded that of multi-clonal infections.

26  Trans R Soc Trop Med Hyg 2000 Jul-Aug;94(4):377-81

Distribution of Plasmodium vivax variants (VK210, VK247 and P. vivax-like) in three endemic areas of the Amazon region of Brazil and their correlation with chloroquine treatment.

Machado RL, Povoa MM

Laboratorio de Malaria, Servico de Parasitologia, Instituto Evandro Chagas/FUNASA, Av. Almirante Barroso 492, 66090-000 Belem, Para, Brazil.

The present study evaluated the glass fibre membrane (GFM)-polymerase chain reaction (PCR)-enzyme-linked immunosorbent assay (ELISA) technique for genotyping the Plasmodium vivax variants, to verify the distribution of P. vivax variants (VK210, VK247 and P. vivax-like) in parts of Brazil and their correlation with levels of parasitaemia, previous malaria experience and clearance of parasitaemia linked to different treatment schedules. The samples were taken from individuals living in Macapa, Porto Velho and Belem, all of which are endemic areas of vivax malaria in the Amazon region of Brazil. Blood samples were collected on GFMs. The gene that codes for the circumsporozoite proteins of P. vivax variants was amplified by PCR and the amplified fragments were hybridized to variant-specific, digoxigenin-labelled oligonucleotide probes by ELISA. The GFM-PCR-ELISA technique was shown to be accurate for epidemiological surveys of the vivax complex. All variants were detected in all 3 areas, but only P. vivax VK210 was found as a single agent of infection, while the other 2 occurred as mixed infections. The P. vivax-like variant was found to be associated with low parasitaemia and VK210 with the highest parasitaemia levels; none of the P. vivax variants was linked with a previous malaria experience. In all cases parasitaemia clearance was identical regarding the type of treatment and consequently it is not possible to confirm the previously reported correlation between P. vivax genotype and response to chloroquine.

27  Trans R Soc Trop Med Hyg 2000 Jul-Aug;94(4):357-60

Evidence for a mass community effect of insecticide-treated bednets on the incidence of malaria on the Kenyan coast.

Howard SC, Omumbo J, Nevill C, Some ES, Donnelly CA, Snow RW

Wellcome Trust Centre for the Epidemiology of Infectious Disease, Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3FY, UK. Email: [email protected]

The use of insecticide-treated bednets (ITBNs) has been shown to be effective in reducing mortality and morbidity from malaria. However, there is mixed evidence as to whether or not community-wide use of ITBNs engenders a 'mass effect', such that those not sleeping under bednets are offered protection from widespread ITBN use in the area in which they live. We have analysed data collected in Kilifi, Kenya, from a cohort of children followed from birth to investigate how the degree of net usage in the locality of a child affects the risk of developing malaria. This effect was explored using a Cox proportional hazards model. For those not using ITBNs, we found that an increasing level of ITBN usage within the area surrounding each child was associated with a decreasing risk of developing malaria, thus providing evidence in support of a mass community effect. The size and significance of this effect were found to decrease as non-overlapping areas of increasing distance away from a child's home were considered. The effect was significant for areas at distances of up to 1.5 km away from each child.

28  Trop Med Int Health 2000 Nov;5(11):805-10

Evaluation of clinical pallor in the identification and treatment of children with moderate and severe anaemia.

Muhe L, Oljira B, Degefu H, Jaffar S, Weber MW

Department of Paediatrics and Child Health, Addis Ababa University, Addis Ababa, Ethiopia; Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, UK; Department of Child and Adolescent Health.

BACKGROUND: Anaemia from malaria is a common problem in developing countries. Blood transfusion in developing countries is available in few hospitals. Children who are severely anaemic and may require urgent blood transfusion usually present to peripheral first-level health facilities from where they must be referred to hospitals. Since most peripheral facilities do not determine haemoglobin levels, the decision on referral has to be made on clinical grounds. OBJECTIVES: To evaluate the sensitivity and specificity of clinical pallor of the palms, nailbeds, conjunctivae, buccal mucosa or tongue against haemoglobin values and their reproducibility among health workers. METHODS: A total of 2540 children 2 months to 5 years of age presenting to a rural health centre in Ethiopia were enrolled. Clinically detected pallor was compared with measured blood haemoglobin concentrations. RESULTS: Any anaemia (haemoglobin < 11 g/dl) was found in 61% of the children. Severe anaemia (haemoglobin < 5 g/dl) was found in 4%. The presence of any pallor clinically correlated with moderate anaemia (haemoglobin level < 8 g/dl) could be detected with a sensitivity of 95% and a specificity of 64-68% when the palm and nailbeds were used and a sensitivity of 84% and a specificity of 81% when the conjunctivae were used. Severe anaemia was detected clinically as severe pallor in 50-56% of cases (with a specificity of 95-96%). Agreement between physicians was highest for conjunctivae and nailbed pallor (87%) and lowest for palm pallor (73%). Using multivariate analysis, identification of a systolic ejection murmur or altered sensorium, the presence of splenomegaly or malarial parasitaemia were independently predictive of severe and moderately severe anaemia. CONCLUSIONS: Moderate and severe anaemia can be identified clinically in most cases for treatment and referral purposes. A systolic ejection murmur, altered sensorium, the presence of splenomegaly or malarial parasitaemia may be used as additional tools in considering urgent referral for blood transfusion.
29  Trop Med Int Health 2000 Nov;5(11):765-70
Field evaluation of the ICT malaria P.f/P.v immunochromatographic test for diagnosis of plasmodium falciparum and p.vivax infection in forest villages of chhindwara, central india.

Singh N, Saxena A, Valecha N

Malaria Research Centre (Field Station), Jabalpur, India; Malaria Research Centre, Delhi, India.

A rapid new immunochromatographic test (ICT malaria P.f/P.v) for diagnosis of Plasmodium falciparum and P.vivax was evaluated against thick blood smears in forest villages of Chhindwara, Madhya Pradesh, where both Plasmodium falciparum and P.vivax are prevalent. 344 symptomatic patients (Gond ethnic tribe) in five villages were screened by field staff of the Malaria Research Centre in October 1999. For P.falciparum, the ICT was 97.5% sensitive and 88% specific, with a positive predictive value (PPV) of 87.6% and a negative predictive value (NPV) of 97.6%. For P.vivax the sensitivity was only 72%, the specificity 99%, with a PPV of 92% and an NPV of 96%. Although a negative test result was inadequate to exclude parasitaemia </= 300/&mgr;l for P.falciparum and </= 1500/&mgr;l for P.vivax, the test is potentially useful in remote areas.

30  Parasitol Today 2000 Dec;16(12):549-51

Automated malaria diagnosis using pigment detection.

Hanscheid T, Valadas E, Grobusch MP

Laboratorio de Bacteriologia, Piso 4, Patologia Clinica, Hospital de Santa Maria, P-1600, Lisboa, Portugal.

Several new methods of malaria diagnosis have recently been developed, but these all rely on clinical suspicion and, consequently, an explicit clinical request. Although some methods lend themselves to automation (eg. PCR), no technique can yet be used for routine clinical automated screening. Detection of birefringent haemozoin has been used to diagnose malaria since the turn of the 20th century. A new generation of full blood count analysers, used widely in clinical laboratories, have the potential to detect haemozoin in white blood cells and probably erythrocytes. Thomas Hanscheid, Emilia Valadas and Martin Grobusch here describe this novel technique for malaria diagnosis and discuss its potential applications.

31 Parasitol Today 2000 Dec;16(12):511-6
Why model malaria?

McKenzie FE

Maxwell Dworkin Laboratory, Harvard University, 33 Oxford Street, 02138, Cambridge, MA, USA.

The past 30 years have seen little tangible progress in alleviating the worldwide burden of malaria. Ellis McKenzie here discusses some of the history, problems and prospects of mathematical models of malaria, and the contributions that models might make towards progress. He argues that models can be powerful tools for integrating information from different disciplines, and that advances in computer modeling can complement and extend classic approaches.

32  Infect Immun 2001 Jan;69(1):129-36

Granulocyte-macrophage colony-stimulating factor-deficient mice have impaired resistance to blood-stage malaria.

Riopel J, Tam M, Mohan K, Marino MW, Stevenson MM

Centre for the Study of Host Resistance, McGill University and The Montreal General Hospital Research Institute, Montreal, Quebec, Canada.

The contribution of granulocyte-macrophage colony-stimulating factor (GM-CSF), a hematopoietic and immunoregulatory cytokine, to resistance to blood-stage malaria was investigated by infecting GM-CSF-deficient (knockout [KO]) mice with Plasmodium chabaudi AS. KO mice were more susceptible to infection than wild-type (WT) mice, as evidenced by higher peak parasitemia, recurrent recrudescent parasitemia, and high mortality. P. chabaudi AS-infected KO mice had impaired splenomegaly and lower leukocytosis but equivalent levels of anemia compared to infected WT mice. Both bone marrow and splenic erythropoiesis were normal in infected KO mice. However, granulocyte-macrophage colony formation was significantly decreased in these tissues of uninfected and infected KO mice, and the numbers of macrophages in the spleen and peritoneal cavity were significantly lower than in infected WT mice. Serum levels of gamma interferon (IFN-gamma) were found to be significantly higher in uninfected KO mice, and the level of this cytokine was not increased during infection. In contrast, IFN-gamma levels were significantly above normal levels in infected WT mice. During infection, tumor necrosis factor alpha (TNF-alpha) levels were significantly increased in KO mice and were significantly higher than TNF-alpha levels in infected WT mice. Our results indicate that GM-CSF contributes to resistance to P. chabaudi AS infection and that it is involved in the development of splenomegaly, leukocytosis, and granulocyte-macrophage hematopoiesis. GM-CSF may also regulate IFN-gamma and TNF-alpha production and activity in response to infection. The abnormal responses seen in infected KO mice may be due to the lack of GM-CSF during development, to the lack of GM-CSF in the infected mature mice, or to both.

33  Infect Immun 2001 Jan;69(1):123-8

Human resistance to plasmodium falciparum increases during puberty and is predicted by dehydroepiandrosterone sulfate levels.

Kurtis JD, Mtalib R, Onyango FK, Duffy PE

U.S. Army Medical Research Unit-Kenya and Kenya Medical Research Institute, Kisumu, Kenya.

Immunity to Plasmodium falciparum develops slowly in areas of endemicity, and this is often ascribed to poorly immunogenic or highly variant parasite antigens. However, among populations newly exposed to malaria, adults acquire immunity more rapidly than children. We examined the relationship between pubertal development and resistance to P. falciparum. During two transmission seasons in western Kenya, we treated the same cohort of young males to eradicate P. falciparum and then obtained blood smears each week for 4 months. We determined pubertal development by Tanner staging and by levels of dehydroepiandrosterone sulfate (DHEAS) and testosterone in plasma. In multivariate and age-stratified analyses, we examined the effect of pubertal development on resistance to malaria. In both seasons (n = 248 and 144 volunteers, respectively), older males were less susceptible than younger males. Age-related decreases in the frequency and density of parasitemia were greatest during puberty (15- to 20-year-olds). DHEAS and testosterone were significant independent predictors of resistance to P. falciparum parasitemia, even after accounting for the effect of age. Fifteen- to 20-year-old males with high DHEAS levels had a 72% lower mean parasite density (P < 0.01) than individuals with low DHEAS levels. Similarly, 21- to 35-year-old males with high DHEAS levels had a 92% lower mean parasite density (P < 0.001) and 48% lower frequency of parasitemia (P < 0.05) than individuals with low DHEAS levels. These data suggest that the long period needed to attain full immunity could be explained as a consequence of host development rather than as the requirement to recognize variant or poorly immunogenic parasite antigens.

34  Parasite Immunol 2000 Nov;22(11):535-43

Mimicking a conformational B cell epitope of the heat shock protein PfHsp70-1 antigen of Plasmodium falciparum using a multiple antigenic peptide.

Dat MH, Behr C, Jouin H, Baleux F, Mercereau-Puijalon O, Dubois P

Unite d'Immunologie Moleculaire des parasites, Pasteur Institute, 25-28 rue du Dr Roux, 75015 Paris, France.

The Pf72/Hsp70-1 antigen is a major target in the naturally acquired immunity against Plasmodium falciparum malaria. We carried out an extensive analysis of the responses to several epitopes on the least conserved C-terminal domain, according to the mode of sensitization: malaria infection or immunization with different immunogens. We found significant differences in the panel of B-cell epitopes recognized by animal models including primates, and by humans sensitized by natural infection. We focused the analysis on one epitope that is unique to Plasmodium species. It is specifically recognized by a monoclonal antibody that mediates the killing of infected hepatocytes in vitro. We produced a polymeric multiple antigenic peptide (MAP) form of this sequence, which enabled us to identify a new B-cell epitope not detected by ELISA with linear peptides. The polymer was strongly recognized by sera from monkeys or humans sensitized by natural infection, whereas the monomer was not. We modelled the three-dimensional structure of the Pf72/Hsp70-1 sequence, using known Escherischia coli DnaK structures as a template. This predicted that the corresponding region would form a loop in the native antigen. The results presented here suggest that the MAP strategy is also particularly useful as a means of obtaining suitable synthetic models for conformation-dependent epitopes.

35  Vaccine 2000 Nov 22;19(7-8):816-24

Differences in epitope recognition, isotype and titer of antisera to plasmodium falciparum merozoite surface protein 4 raised by different modes of DNA or protein immunization.

Wang L, Menting JG, Black CG, Stowers A, Kaslow DC, Hoffman SL, Coppel RL

Department of Microbiology, Monash University, Vic., 3800, Clayton, Australia.

Plasmodium falciparum merozoite surface protein 4 (MSP4) is being developed as a component of a subunit vaccine against asexual stages of malaria. Three DNA constructs were produced that induced expression of MSP4 either in the cytoplasm of transfected cells or secreted from cells under the control of the human tissue plasminogen activator (TPA) signal or the native P. falciparum MSP4 signal. Only the construct containing the TPA signal induced detectable antibodies in mice, although gene expression was demonstrated in all constructs and MSP4 was shown to be secreted using either signal by in vitro transient transfection of COS cells. Two recombinant MSP4 proteins that encoded the same sequence as the plasmid DNA were produced in E. coli (EcMSP4-His) and S. cerevisiae (yMSP4-His) and used to raise antibodies in mice. Comparison of the antibodies elicited by these various antigen formulations showed differences in titer, isotype and epitope recognition. The titer of antibodies induced by DNA vaccination was lower than that induced by yMSP4-His, which in turn was lower than that induced by EcMSP4-His. The isotype profiles of the antibodies were also different, the plasmid DNA induced predominantly IgG(2a) responses whereas the two proteins induced predominantly IgG(1) responses. The antibodies induced by DNA and yMSP4-His recognized predominantly the C-terminal epidermal growth factor (EGF)-like domain of the protein, whereas EcMSP4-His induced antibodies recognizing all domains of the protein equally. The antibodies induced by DNA vaccination were directed almost extensively to conformational epitopes so that reactivity with native MSP4 was abolished after disulfide bonds in the protein were disrupted. Antibodies induced by recombinant proteins recognized linear epitopes as well and reactivity to native MSP4 was preserved after reduction and alkylation of parasite proteins.

36  Proc Natl Acad Sci U S A 2001 Jan 2;98(1):271-276
From the Cover: Malaria parasite exit from the host erythrocyte: A two-step process requiring extraerythrocytic proteolysis.

Salmon BL, Oksman A, Goldberg DE

Howard Hughes Medical Institute, Departments of Molecular Medicine and Microbiology, Washington University School of Medicine, St. Louis, MO 63110.

Intraerythrocytic malaria parasites replicate by the process of schizogeny, during which time they copy their genetic material and package it into infective merozoites. These merozoites must then exit the host cell to invade new erythrocytes. To better characterize the events of merozoite escape, erythrocytes containing Plasmodium falciparum schizonts were cultured in the presence of the cysteine protease inhibitor, l-transepoxy-succinyl-leucylamido-(4-guanidino)butane (E64). This treatment resulted in the accumulation of extraerythrocytic merozoites locked within a thin, transparent membrane. Immunomicroscopy demonstrated that the single membrane surrounding the merozoites is not erythrocytic but rather is derived from the parasitophorous vacuolar membrane (PVM). Importantly, structures identical in appearance can be detected in untreated cultures at low frequency. Further studies revealed that (i) merozoites from the PVM-enclosed merozoite structures (PEMS) are invasive, viable, and capable of normal development; (ii) PEMS can be purified easily and efficiently; and (iii) when PEMS are added to uninfected red blood cells, released merozoites can establish a synchronous wave of infection. These observations suggest that l-transepoxy-succinyl-leucylamido-(4-guanidino)butane (E64) causes an accumulation of an intermediate normally present during the process of rupture. We propose a model for the process of rupture: merozoites enclosed within the PVM first exit from the host erythrocyte and then rapidly escape from the PVM by a proteolysis-dependent mechanism.

37  Int J Parasitol 2000 Nov 1;30(12-13):1395-1405

Effects of environmental change on emerging parasitic diseases.

Patz JA, Graczyk TK, Geller N, Vittor AY

Department of Environmental Health Sciences, Johns Hopkins University School of Hygiene and Public Health, 615 N. Wolfe Street, MD 21205-2179,., Baltimore, USA

Ecological disturbances exert an influence on the emergence and proliferation of malaria and zoonotic parasitic diseases, including, Leishmaniasis, cryptosporidiosis, giardiasis, trypanosomiasis, schistosomiasis, filariasis, onchocerciasis, and loiasis. Each environmental change, whether occurring as a natural phenomenon or through human intervention, changes the ecological balance and context within which disease hosts or vectors and parasites breed, develop, and transmit disease. Each species occupies a particular ecological niche and vector species sub-populations are distinct behaviourally and genetically as they adapt to man-made environments. Most zoonotic parasites display three distinct life cycles: sylvatic, zoonotic, and anthroponotic. In adapting to changed environmental conditions, including reduced non-human population and increased human population, some vectors display conversion from a primarily zoophyllic to primarily anthrophyllic orientation. Deforestation and ensuing changes in landuse, human settlement, commercial development, road construction, water control systems (dams, canals, irrigation systems, reservoirs), and climate, singly, and in combination have been accompanied by global increases in morbidity and mortality from emergent parasitic disease. The replacement of forests with crop farming, ranching, and raising small animals can create supportive habitats for parasites and their host vectors. When the landuse of deforested areas changes, the pattern of human settlement is altered and habitat fragmentation may provide opportunities for exchange and transmission of parasites to the heretofore uninfected humans. Construction of water control projects can lead to shifts in such vector populations as snails and mosquitoes and their parasites. Construction of roads in previously inaccessible forested areas can lead to erosion, and stagnant ponds by blocking the flow of streams when the water rises during the rainy season. The combined effects of environmentally detrimental changes in local landuse and alterations in global climate disrupt the natural ecosystem and can increase the risk of transmission of parasitic diseases to the human population.

38  Sante 2000 Jul-Aug;10(4):267-75

[Lagoonal and coastal malaria at cotonou: entomological findings].

Akogbeto M

Centre de recherche entomologique OCCGE, 06 BP 2604 Cotonou, Benin.

Nowadays, malaria control is planned according to the epidemiological context. Various aspects of malaria have been described in subSaharan Africa. We report here entomological data from the coastal area of Benin, West Africa, which has many lakes and lagoons. We carried out a longitudinal study in which we investigated the dynamics of populations of malaria vectors in various zones, the frequency of inoculation in these zones, the infestation rate of the Anopheles gambiae mosquitoes collected, the effect of urbanization on malaria transmission, the effects of inundation and of salinity at mosquito breeding sites. A total of 3, 342 identifications were made on a chromosomal basis. Two species of the Anopheles gambiae complex were detected in the coastal and lagoon areas of Benin: An. melas and An. gambiae ss. The density of the populations of these species was highly dependent on the level of urbanization. In traditional villages on the lagoons (such as Agbalilame, Djegbadji and Ketonou), the density of An. melas (86. 2%) was much higher than that in more urbanized areas (such as Ladji and Abomey-Calavi) (4.9%). We checked for chromosome polymorphism. We detected a 2Rn1 inversion in An. melas, similar to the 2Rn inversion found in mosquitoes in Gambia and Guinea-Bissau. The frequency of the n1 inversion and the density of An. melas populations were correlated and both seemed to depend on a single factor, salinity. The epidemiological situation with respect to malaria was very heterogeneous in the lagoon area of Benin. In the city of Cotonou, transmission was seasonal, sporozoite indices and the frequency of inoculation were high, in contrast to what would normally be expected in an urban area. In communities built on the beach, the level of transmission was markedly lower: about 5 infected bites per person per year versus 29 infected bites per person in the center of the city. In the traditional fishing villages, a paradoxical situation was observed in which the mosquitoes were very aggressive towards humans (4,502 bites per person per year) but the frequency of transmission was low (d = 0. 27%, CS+ = 0.57%). This was largely due to the high density in this area of An. melas, a poor malaria vector. If traditional villages become more urbanized, more freshwater breeding sites are created and the An. gambiae population increases, leading to an increase in malaria transmission. This is the reason for the higher level of malaria transmission at Ladji and Abomey-Calavi (h = 47 infected bites per person per year) than at Agbailame, Djegbadji and Ketonou (h = 12.1 infected bites per person per year)

EHP is sponsored by the Office of Health, Infectious Diseases and Nutrition, 
Bureau for Global Health,  of the U.S. Agency for International Development

Last modified April 02, 2002