Ecological studies on the intermediate host snails and the relevance to schistosomiasis control

Madsen, Henry

doi:10.1590/s0074-02761992000800039

Cited by 9 publications

(6 citation statements)

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“…Contrary to P. metidjensis, most sites colonized by B. truncatus were man-made dams and irrigation canals located in lowland plains, and this finding agreed with other reports on the distribution of this species in Morocco (Ghamizi 1998) or in other African countries (Greer et al 1990, Madsen 1992, Yousif et al 1998, Sturrock et al 2001. Most values noted for electric conductivity in running water (Table 2) agreed with the report by MeierBrook et al (1987) for which B. truncatus did not live in waters with a high electric conductivity.…”

Section: Discussionsupporting

confidence: 91%

Habitats of Bulinus truncatus and Planorbarius metidjensis, the intermediate hosts of urinary schistosomosis, under a semiarid or an arid climate

Yacoubi

Zekhnini

Rondelaud³

et al. 2007

Parasitol Res

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Since Bulinus truncatus and Planorbarius metidjensis are the intermediate hosts of Schistosoma haematobium in southwestern Morocco, five rivers were investigated to identify sites colonized by either of both species and determine the characteristics of their habitats via the study of 12 physicochemical parameters in running water. P. metidjensis was observed in the upper valleys of three rivers, whereas B. truncatus was found in sites of lower altitude. A component analysis demonstrated that altitude (from 4 to 1,380 m), water pH (from 5.9 to 9.2), and electric conductivity (from 120 to 6,020 microS/cm) were the main descriptors of environment. A multiple correspondence analysis showed that P. metidjensis was associated to Ancylus fluviatilis, high altitude, and possibly low electric conductivity. B. truncatus was associated to Melanoides tuberculata and was found in lower altitude sites with medium electric conductivity in water. Using logistic regressions, the main characteristics were altitude and dissolved oxygen for B. truncatus, and chlorides and CaCO3 for P. metidjensis. As the habitats of both S. haematobium intermediate hosts differed from each other by altitude and the frequency of snails, which cohabited with them, these findings may be used to detect the presence of either of both intermediate hosts in numerous spring heads which are present on the western slope of the Anti Atlas mountains and the corresponding valleys.

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Section: Discussionsupporting

confidence: 91%

Habitats of Bulinus truncatus and Planorbarius metidjensis, the intermediate hosts of urinary schistosomosis, under a semiarid or an arid climate

Yacoubi

Zekhnini

Rondelaud³

et al. 2007

Parasitol Res

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“…Infection in Bi. pfeifferi , while variable by month and year, was comparatively high overall, consistent with previous reports in the NRV [21, 44], and in the Niger River catchment in neighbouring Mali [63–65]. It is not clear why this is the case.…”

Section: Discussionsupporting

confidence: 85%

Freshwater snails of biomedical importance in the Niger River Valley: evidence of temporal and spatial patterns in abundance, distribution and infection with Schistosoma spp.

et al. 2019

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BackgroundSound knowledge of the abundance and distribution of intermediate host snails is key to understanding schistosomiasis transmission and to inform effective interventions in endemic areas.MethodsA longitudinal field survey of freshwater snails of biomedical importance was undertaken in the Niger River Valley (NRV) between July 2011 and January 2016, targeting Bulinus spp. and Biomphalaria pfeifferi (intermediate hosts of Schistosoma spp.), and Radix natalensis (intermediate host of Fasciola spp.). Monthly snail collections were carried out in 92 sites, near 20 localities endemic for S. haematobium. All bulinids and Bi. pfeifferi were inspected for infection with Schistosoma spp., and R. natalensis for infection with Fasciola spp.ResultsBulinus truncatus was the most abundant species found, followed by Bulinus forskalii, R. natalensis and Bi. pfeifferi. High abundance was associated with irrigation canals for all species with highest numbers of Bulinus spp. and R. natalensis. Seasonality in abundance was statistically significant in all species, with greater numbers associated with dry season months in the first half of the year. Both B. truncatus and R. natalensis showed a negative association with some wet season months, particularly August. Prevalences of Schistosoma spp. within snails across the entire study were as follows: Bi. pfeifferi: 3.45% (79/2290); B. truncatus: 0.8% (342/42,500); and B. forskalii: 0.2% (24/11,989). No R. natalensis (n = 2530) were infected. Seasonality of infection was evident for B. truncatus, with highest proportions shedding in the middle of the dry season and lowest in the rainy season, and month being a significant predictor of infection. Bulinus spp. and Bi. pfeifferi showed a significant correlation of snail abundance with the number of snails shedding. In B. truncatus, both prevalence of Schistosoma spp. infection, and abundance of shedding snails were significantly higher in pond habitats than in irrigation canals.ConclusionsEvidence of seasonality in both overall snail abundance and infection with Schistosoma spp. in B. truncatus, the main intermediate host in the region, has significant implications for monitoring and interrupting transmission of Schistosoma spp. in the NRV. Monthly longitudinal surveys, representing intensive sampling effort have provided the resolution needed to ascertain both temporal and spatial trends in this study. These data can inform planning of interventions and treatment within the region.

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“…The higher mean pH level recorded during the dry season could be due to higher transparency of the water bodies resulting in active removal of carbon (IV) oxide and consequently production of oxygen through photosynthesis. The concentration of hydrogen ions is rarely a factor conditioning the presence and distribution of the snails [26]. Therefore there were insignificant relationships between abundance of snails and pH level in our study.…”

Section: Discussioncontrasting

confidence: 58%

Effects of Abiotic and Biotic Factors on the Snail Predator, Procambarus clarkii, Girad (Decapoda: Cambaridae): Implications for Schistosomiasis Control in Kenya

Maina¹,

Jm²,

Mw³

et al. 2018

IJMBR

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Background & Objective: There is increasing interest not only in the control of schistosomiasis but also, the physico-chemical parameters responsible for seasonal variation in transmission of the disease and the effect they may have on both the predator, crustacean, and the snails. In Africa, one of the major challenges of studying these parameters is lack of equipment that can be used in-situ. In the present study, we sought to assess the effects of physic-chemical parameters of schistosomiasis transmitting snails and their natural predators, crayfish. Methods: Cross-sectional study design employing quantitative techniques for data and analysis collection. Study was conducted in Machakos-Kitui area of Kenya within the river Athi drainage basin. Study subjects include snails inhabiting the study streams. Results: 161 snail out of 2325 total sampled snails on shedding turned out to be positive for mammalian schistosomes representing a prevalence of 6.9%. The pH, water and temperature did not vary significantly in the different streams (P-value = 0.7524 at P < 0.05). Increase in water temperature showed significant positive correlations with B. pfeifferi (r 2 = 0.665; P < 0.01) and B. nasutus (r 2 = 0.0.665; P < 0.05), Lymneanatalensis (r 2 = 0.589; P < 0.010). The overall mean pH value was 7.8 ± 0.8 with values ranging from 7.34 in KwaMutanga River to 8.6 recorded in Kyanguli River. Interpretation & conclusion: While planning snail sampling and initiation of biological control strategies, abiotic and biotic factors should be borne in mind as they seem to play a key role in the success of schistosomiasis intervention, especially at the intermediate host level.

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Ecological studies on the intermediate host snails and the relevance to schistosomiasis control

Cited by 9 publications

References 0 publications

Habitats of Bulinus truncatus and Planorbarius metidjensis, the intermediate hosts of urinary schistosomosis, under a semiarid or an arid climate

Habitats of Bulinus truncatus and Planorbarius metidjensis, the intermediate hosts of urinary schistosomosis, under a semiarid or an arid climate

Freshwater snails of biomedical importance in the Niger River Valley: evidence of temporal and spatial patterns in abundance, distribution and infection with Schistosoma spp.

Effects of Abiotic and Biotic Factors on the Snail Predator, Procambarus clarkii, Girad (Decapoda: Cambaridae): Implications for Schistosomiasis Control in Kenya

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