Christopher C. Appleton

Choice of treatment for fever at household level in Malawi: examining spatial patterns

BackgroundAlthough malaria imposes an enormous burden on Malawi, it remains a controllable disease. The key strategies for control are based on early diagnosis and prompt treatment with effective antimalarials. Its success, however, depends on understanding the factors influencing health care decision making at household level, which has implications for implementing policies aimed at promoting health care practices and utilization.MethodsAn analysis of patterns of treatment-seeking behaviour among care-givers of children of malarial fever in Malawi, based on the 2000 Malawi demographic and health survey, is presented. The choice of treatment provider (home, shop, or formal hospital care, others) was considered as a multi-categorical response, and a multinomial logistic regression model was used to investigate determinants of choosing any particular provider. The model incorporated random effects, at subdistrict level, to measure the influence of geographical location on the choice of any treatment provider. Inference was Bayesian and based on Markov chain Monte Carlo techniques.Results and ConclusionSpatial variation was found in the choice of a provider and determinants of choice of any provider differed. Important risk factors included place of residence, access to media, care-givers age and care factors including unavailability and inaccessibility of care. A greater effort is needed to improve the quality of malaria home treatment or expand health facility utilization, at all levels of administration if reducing malaria is to be realised in Malawi. Health promotion and education interventions should stress promptness of health facility visits, improved access to appropriate drugs, and accurate dosing for home-based treatments.

The rat lung-worm Angiostrongylus cantonensis: a first report in South Africa

A study of the parasites of invasive rats in the eThekwini Municipality of KwaZulu-Natal has led to this first report of Angiostrongylus (Parastrongylus) cantonensis, commonly known as the rat lung worm, in South Africa. A. cantonensis is clearly endemic in this region and probably also in other areas of South Africa. There are a few reports of this nematode from Africa (excluding South Africa): in rats and snails in Egypt (Fouad and Abdulla, 1978), in snails in Nigeria (Sowemimo and Asaolur, 2004), and a human case from Ivory Coast (1980). As humans are accidental hosts, the parasite cannot complete its life cycle, and immature worms lodge in the central nervous system where they elicit a condition known as eosinophilic meningitis.

Modelling the effect of malaria endemicity on spatial variations in childhood fever, diarrhoea and pneumonia in Malawi

BackgroundCo-morbidity with conditions such as fever, diarrhoea and pneumonia is a common phenomenon in tropical Africa. However, little is known about geographical overlaps in these illnesses. Spatial modelling may improve our understanding of the epidemiology of the diseases for efficient and cost-effective control.MethodsThis study assessed subdistrict-specific spatial associations of the three conditions (fever, diarrhoea and pneumonia) in relation to malaria endemicity. We used data from the 2000 Malawi demographic and health survey which captured the history of childhood morbidities 2 weeks prior to the survey date. The disease status of each child in each area was the outcome of interest and was modelled using a trivariate logistic regression model, and incorporated random effects to measure spatial correlation.ResultsThe risk of fever was positively associated with high and medium malaria endemicity levels relative to low endemicity level, while for diarrhoea and pneumonia we observed marginal positive association at high endemicity level relative to low endemicity level, controlling for confounding covariates and heterogeneity. A positive spatial correlation was found between fever and diarrhoea (r = 0.29); while weak associations were estimated between fever and pneumonia (r = 0.01); and between diarrhoea and pneumonia (r = 0.05). The proportion of structured spatial variation compared to unstructured variation was 0.67 (95% credible interval (CI): 0.31–0.91) for fever, 0.67 (95 % CI: 0.27–0.93) for diarrhoea, and 0.87 (95% CI: 0.62–0.96) for pneumonia.ConclusionThe analysis suggests some similarities in subdistrict-specific spatial variation of childhood morbidities of fever, diarrhoea and pneumonia, and might be a result of shared and overlapping risk factors, one of which is malaria endemicity.

Geographical disparities in core population coverage indicators for roll back malaria in Malawi

BackgroundImplementation of known effective interventions would necessitate the reduction of malaria burden by half by the year 2010. Identifying geographical disparities of coverage of these interventions at small area level is useful to inform where greatest scaling-up efforts should be concentrated. They also provide baseline data against which future scaling-up of interventions can be compared. However, population data are not always available at local level. This study applied spatial smoothing methods to generate maps at subdistrict level in Malawi to serve such purposes.MethodsData for the following responses from the 2000 Malawi Demographic and Health Survey (DHS) were aggregated at subdistrict level: (1) households possessing at least one bednet; (2) children under 5 years who slept under a bednet the night before the survey; (3) bednets retreated with insecticide within past 6–12 months preceding the survey; (4) children under 5 who had fever two weeks before the survey and received treatment within 24 hours from the onset of fever; and (5) women who received intermittent preventive treatment of malaria during their last pregnancy. Each response was geographically smoothed at subdistrict level by applying conditional autoregressive models using Markov Chain Monte Carlo simulation techniques.ResultsThe underlying geographical patterns of coverage of indicators were more clear in the smoothed maps than in the original unsmoothed maps, with relatively high coverage in urban areas than in rural areas for all indicators. The percentage of households possessing at least one bednet was 19% (95% credible interval (CI): 16–21%), with 9% (95% CI: 7–11%) of children sleeping under a net, while 18% (95% CI: 16–19%) of households had retreated their nets within past 12 months prior to the survey. The northern region and lakeshore areas had high bednet coverage, but low usage and re-treatment rates. Coverage rate of children who received antimalarial treatment within 24 hours after onset of fever was consistently low for most parts of the country, with mean coverage of 4.8% (95% CI: 4.5–5.0%). About 48% (95% CI: 47–50%) of women received antimalarial prophylaxis during their pregnancy, with highest rates in the southern and northern areas.ConclusionThe striking geographical patterns, for example between predominantly urban and rural areas, may reflect spatial differences in provider compliance or coverage, and can partly be explained by socio-economic and cultural differences. The wide gap between high bed net coverage and low retreatment rates may reflect variation in perceptions about malaria, which may be addressed by implementing information, education and communication campaigns or introducing long lasting insecticide nets. Our results demonstrate that DHS data, with appropriate methodology, can provide acceptable estimates at sub-national level for monitoring and evaluation of malaria control goals.

Population Structure of an Invasive Parthenogenetic Gastropod in Coastal Lakes and Estuaries of Northern KwaZulu-Natal, South Africa

Background Estuaries and coastal lakes receive little attention despite being heavily invaded by non-indigenous invasive species (NIS). In these situations, studies of population dynamics in invaded habitats can provide valuable insights into how NIS interact with new environments. Tarebia granifera is a prosobranch gastropod from south-east Asia which has invaded other sub-tropical parts of the world. This study addresses whether a small number of key environmental factors influences gastropod communities, and specifically how the population density and size structure of T. granifera were influenced by environmental change in estuaries and coastal lakes in southern Africa. Methodology/Principal Findings T. graniferas density, number of brooded juveniles and size structure were measured at the St. Lucia Estuary, Mgobozeleni Estuary, Lake Sibaya and Lake Nhlange. Size structure was classified according to shell height (SH). All dissected individuals were found to be female and free from trematode infection. Salinity, water depth, temperature, and pH were the main factors correlated with population density of gastropod communities. T. granifera often reached densities well over 1000 ind. m−2, displacing indigenous gastropods and becoming a dominant component of the benthic community. T. granifera successfully invaded estuaries despite frequent exposure to high salinity and desiccation, which could together eliminate >97% of the population. The persistence of T. granifera was ensured due to its high fecundity and the environmental tolerance of large adults (20–30 mm SH) which carried an average of 158±12.8 SD brooded juveniles. Repeat introductions were not essential for the success of this parthenogenetic NIS. Conclusion/Significance There is a need for a broader study on the reproductive biology of T. granifera (including the previously overlooked “brood pouch ecology”), which affects population dynamics and may be relevant to other parthenogenetic NIS, such as Melanoides tuberculata and Potamopyrgus antipodarum.

A school-based helminth control programme successfully implemented in KwaZulu-Natal

The design of the school-based Parasite Control Programme (referred to below as a helminth control programme) run in the province of KwaZulu-Natal, South Africa, from 1997-2000 is described. Emphasis is given to the role of the Parasite Control Task Group which provided a forum for a wide variety of issues relating to the programme to be debated before they were agreed upon. The programme targeted the three common geohelminths (Trichuris trichiura, Ascaris lumbricoide and hookworm) and the urinary schistosomiasis (bilharzia) fluke, Schistosoma haematobium. It is expected that a national control programme will be setup in South Africa in the future. With this in mind, new opinions and experiences in several aspects of helminth control that have become available since 2000 are included so that they can be considered for any future programme.

Macro-invertebrate predators of freshwater pulmonate snails in Africa, with particular reference to Appasus grassei (Heteroptera) and Procambarus clarkii (Decapoda)

A range of African and alien macro-invertebrates has been reported preying on freshwater pulmonate snails, including those that serve as intermediate hosts for bloodflukes of the genus Schistosoma. Predation by five molluscivorous taxa is reviewed here: indigenous leeches (Glossiphoniidae), marsh fly larvae (Sciomyzidae), waterbugs (Belostomatidae), crabs (Potamonautidae) and invasive crayfish (Astacidae). Common features are a lack of prey specificity but clear prey-size specificity. Attention is drawn to the ability of invasive snail species (Physidae and Lymnaeidae) to avoid predation by several of these taxa. Evidence suggests that only the alien invasive crayfish Procambarus clarkii has potential as a snail biocontrol agent, but that its use should not be encouraged.

A Coprological Survey of Protozoan and Nematode Parasites of Free-Ranging Chacma Baboons (Papio ursinus) in the Southwestern Cape, South Africa

This study provides data on gastrointestinal parasite infections in the geographically isolated and locally fragmented Cape Peninsula baboon population and two troops from neighbouring populations in the Western Cape Province, South Africa. We obtained data on parasite diversity and prevalence from 616 faecal samples collected from over 350 individuals in eight troops between July 2006 and May 2008. We processed faecal samples using a modified formalin-ether sedimentation technique and identified nematode eggs and protozoan cysts. We recovered seven nematode genera (Trichuris sp., Oesophagostomum sp., Trichostrongylus sp., Physaloptera sp., Ascaris sp., an unidentified hookworm morphotype, and an unidentified spirurid) and eight protozoan species (Balantidium coli, Entamoeba coli, E. histolytica/dispar, E. chattoni, E. hartmanni, Iodamoeba butschlii, Endolimax nana and Chilomastix mesnili). The nematode and protozoan fauna of the Cape Peninsula baboon population was similar to both neighbouring and geographically distinct chacma baboon populations in South Africa. Parasite prevalence was variable across study sites and seasonality did not appear to have an effect on patterns of infection. The finding of the eggs of an ascarid, possibly Ascaris sp., in the Cape Peninsula baboon population represents the first report of this nematode genus in wild baboons in South Africa.This study provides data on gastrointestinal parasite infections in the geographically isolated and locally fragmented Cape Peninsula baboon population and two troops from neighbouring populations in the Western Cape Province, South Africa. We obtained data on parasite diversity and prevalence from 616 faecal samples collected from over 350 individuals in eight troops between July 2006 and May 2008. We processed faecal samples using a modified formalin-ether sedimentation technique and identified nematode eggs and protozoan cysts. We recovered seven nematode genera (Trichuris sp., Oesophagostomum sp., Trichostrongylus sp., Physaloptera sp., Ascaris sp., an unidentified hookworm morphotype, and an unidentified spirurid) and eight protozoan species (Balantidium coli, Entamoeba coli, E. histolytica/dispar, E. chattoni, E. hartmanni, lodamoeba butschlii, Endolimax nana and Chilomastix mesnili). The nematode and protozoan fauna of the Cape Peninsula baboon population was similar to both neighbouring and geogra...

Susceptibility of schistosome host snails to predation by sciomyzid flies (Diptera: Sciomyzidae) in South Africa

Afrotropical sciomyzids are predators of freshwater pulmonate snails. Studies have indicated that these flies may play a role in controlling medically important (target) snail populations, especially snail intermediate hosts of schistosomes. This study investigated the preferential feeding of Sepedon scapularis and S. neavei on four commonly-occurring molluscs in South Africa. The feeding behaviour of these flies was observed on a polyphagous diet consisting of Bulinus tropicus, Bu. forskalii, Bu. africanus and Biomphalaria pfeifferi. Laboratory experiments were set up with a constant number of 12 live snails per petri dish. Snail mortality was recorded daily for the duration of the larval period. Preliminary results show that both fly species fed preferentially upon Bu. africanus and Bi. pfeifferi. Overall, S. neavei killed more target snails than S. scapularis did. The preference of both fly species was Bi. pfeifferi, followed by Bu. africanus, Bu. tropicus and Bu. forskalii. These sciomyzid species are, therefore, potential candidates as biological control agents of medically-important snails. Whilst these findings are based on laboratory studies, they need to be validated by field trials.

Endo-parasites of public-health importance recovered from rodents in the Durban metropolitan area, South Africa

Background: Parasite infections of public health importance carried by Rattus spp. on the African continent (excluding toxoplasmosis) have not been adequately researched. The aim of this study was to investigate endoparasites of public health importance, particularly those associated with R. norvegicus, at different locations and seasons within the port-city, Durban.Methods: Four hundred rodents (379 R. norvegicus, 10 R. rattus and 11 Mastomys natalensis) were live-trapped at 60 sites in four locations, during wet and dry seasons in 2009. Rats were humanely euthanased, cardiac blood drawn (for blood smears and serology), ectoparasites removed and dissected. Each organ was separately processed to collect parasites. Binary logistic regression and four-way ANOVAs were used to test for the effects of location, season, rodent age and gender on parasite prevalence, richness and abundance.Results: Eight parasites of public health importance were detected: Gongylonema sp. (25.3%), Trypanosoma lewisi (22.8%), Hyme...