The distribution of <i>Schistosoma mansoni</i> in the Rusizi Plain (Burundi)

Gryseels, B.; Nkulikyinka, L

doi:10.1080/00034983.1988.11812294

Cited by 26 publications

(15 citation statements)

References 3 publications

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“…Future studies are needed to differentiate potential impacts of aquatic plants and macroinvertebrates on human schistosomes from those on non-human schistosome, hybrid and other cryptic species of forked-tailed cercariae emitted from the same snails in this study region. Moreover, the historically weak correlation between snail abundance and human schistosomiasis prevalence [ 13 , 14 ], and mismatch between snail and cercarial abundances [ 19 ], might be influenced by the considerable heterogeneity we observed in cercarial production among infected snails.…”

Section: Discussionmentioning

confidence: 99%

Aquatic macrophytes and macroinvertebrate predators affect densities of snail hosts and local production of schistosome cercariae that cause human schistosomiasis

et al. 2020

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Background Schistosomiasis is responsible for the second highest burden of disease among neglected tropical diseases globally, with over 90 percent of cases occurring in African regions where drugs to treat the disease are only sporadically available. Additionally, human re-infection after treatment can be a problem where there are high numbers of infected snails in the environment. Recent experiments indicate that aquatic factors, including plants, nutrients, or predators, can influence snail abundance and parasite production within infected snails, both components of human risk. This study investigated how snail host abundance and release of cercariae (the free swimming stage infective to humans) varies at water access sites in an endemic region in Senegal, a setting where human schistosomiasis prevalence is among the highest globally. Methods/Principal findings We collected snail intermediate hosts at 15 random points stratified by three habitat types at 36 water access sites, and counted cercarial production by each snail after transfer to the laboratory on the same day. We found that aquatic vegetation was positively associated with per-capita cercarial release by snails, probably because macrophytes harbor periphyton resources that snails feed upon, and well-fed snails tend to produce more parasites. In contrast, the abundance of aquatic macroinvertebrate snail predators was negatively associated with per-capita cercarial release by snails, probably because of several potential sublethal effects on snails or snail infection, despite a positive association between snail predators and total snail numbers at a site, possibly due to shared habitat usage or prey tracking by the predators. Thus, complex bottom-up and top-down ecological effects in this region plausibly influence the snail shedding rate and thus, total local density of schistosome cercariae. Conclusions/Significance Our study suggests that aquatic macrophytes and snail predators can influence per-capita cercarial production and total abundance of snails. Thus, snail control efforts might benefit by targeting specific snail habitats where parasite production is greatest. In conclusion, a better understanding of top-down and bottom-up ecological factors that regulate densities of cercarial release by snails, rather than solely snail densities or snail infection prevalence, might facilitate improved schistosomiasis control.

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Section: Discussionmentioning

confidence: 99%

Aquatic macrophytes and macroinvertebrate predators affect densities of snail hosts and local production of schistosome cercariae that cause human schistosomiasis

et al. 2020

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“…The area and epidemiologic details have been described by Gryseels and Nkulikyinka. 22 The study group consisted of 25 females and 25 males, who had been diagnosed as positive in a preliminary population survey based on single 25-mg Kato-Katz slides. Their ages ranged from seven to 70 years (median ϭ 18.5 years); 26 persons were less than 20 years old.…”

Section: Methodsmentioning

confidence: 99%

Day-to-day fluctuation of schistosome circulating antigen levels in serum and urine of humans infected with Schistosoma mansoni in Burundi.

Polman¹,

Engels²,

Fathers³

et al. 1998

The American Journal of Tropical Medicine and Hygiene

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Day-today fluctuations of both circulating anodic antigen (CAA) and circulating cathodic antigen (CCA) in serum and urine were examined simultaneously in a group of Schistosoma mansoni-infected individuals from Burundi and compared with each other and with fecal egg count fluctuations. Significant correlations were found between fecal egg counts and circulating antigens (CAA and CCA) and between circulating antigen levels in serum and urine samples. The cumulative percentage of positive results after three samplings was highest for urine CCA detection, followed by fecal egg counts, serum CCA, serum CAA, and urine CAA detection, respectively. It was demonstrated that circulating antigen levels in both serum and urine showed less fluctuation than fecal egg counts, except for urine CAA levels. The serum CAA detection assay in particular, although less sensitive in this low endemic area in Burundi, gave very constant measurements over a period of one week. Our results indicate that detection of circulating antigens in a single serum or urine sample provides a quantitatively more stable diagnosis of S. mansoni infection than fecal egg counts based on a single stool examination.

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“…At the time of the surveys, this area was thought to be a new focus of S. mansoni (Gryseels et al 1987). The population density in this areas was 150 inhabitants/km 2 .…”

Section: Study Populationsmentioning

confidence: 99%

Aggregation in schistosomiasis: comparison of the relationships between prevalence and intensity in different endemic areas

et al. 1994

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SUMMARYDistributions of the intensities of helminth infections within their host populations are invariably aggregated. In the case of the intestinal nematodes, the degrees of aggregation have been shown to be species specific, and constant for any given species despite geographical variation in study sites. This species-specific aggregation can be quantified and used as a tool in planning control interventions. One practical application is that the prevalence of infection can be used to predict the prevalence of heavy infection and thus the risks of morbidity. This paper investigates the patterns of aggregation in schistosome egg counts in different endemic areas in Africa (data sets were obtained from Burundi, Cameroon, Tanzania, Zambia and Zaire). The analysis demonstrates that the degree of parasite aggregation, for both Schistosoma mansoni and S. haematobium, differs amongst the different study localities. This is probably due to area-specific differences in host exposure and immunity. This implies that for these schistosome species, it is not possible to predict egg count distributions or morbidity levels from prevalence data alone.

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The distribution of Schistosoma mansoni in the Rusizi Plain (Burundi)

Cited by 26 publications

References 3 publications

Aquatic macrophytes and macroinvertebrate predators affect densities of snail hosts and local production of schistosome cercariae that cause human schistosomiasis

Aquatic macrophytes and macroinvertebrate predators affect densities of snail hosts and local production of schistosome cercariae that cause human schistosomiasis

Day-to-day fluctuation of schistosome circulating antigen levels in serum and urine of humans infected with Schistosoma mansoni in Burundi.

Aggregation in schistosomiasis: comparison of the relationships between prevalence and intensity in different endemic areas

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