Schistosomiasis in Ethiopia

Kloos, Helmut; Lo, Chin Tsong; Birrie, Hailu; Ayele, Teklemariam; Tedla, Shibru; Tsegay, Fekade

doi:10.1016/0277-9536(88)90174-8

Cited by 72 publications

(84 citation statements)

References 31 publications

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“…This is in line with empirical data, with studies reporting the existence of B. pfeifferi or other Biomphalaria populations at low temperatures with no or only seasonal schistosomiasis transmission occurring [28]–[30]. This band of temperatures is relatively narrow however, and it is therefore probable that the majority of cooler areas where B. pfeifferi snails are currently found will become suitable for schistosomiasis transmission over coming decades.…”

Section: Discussionsupporting

confidence: 86%

The Effect of Increasing Water Temperatures on Schistosoma mansoni Transmission and Biomphalaria pfeifferi Population Dynamics: An Agent-Based Modelling Study

McCreesh

Booth

2014

PLoS ONE

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IntroductionThere is increasing interest in the control and elimination of schistosomiasis. Little is known, however, about the likely effects of increasing water-body temperatures on transmission.MethodsWe have developed an agent-based model of the temperature-sensitive stages of the Schistosoma and intermediate host snail life-cycles, parameterised using data from S. mansoni and Biomphalaria pfeifferi laboratory and field-based observations. Infection risk is calculated as the number of cercariae in the model, adjusted for their probability of causing infection.ResultsThe number of snails in the model is approximately constant between 15–31°C. Outside this range, snail numbers drop sharply, and the snail population cannot survive outside the range 14–32°C. Mean snail generation time decreases with increasing temperature from 176 days at 14°C to 46 days at 26°C. Human infection risk is highest between 16–18°C and 1 pm and 6–10 pm in calm water, and 20–25°C and 12–4 pm in flowing water. Infection risk increases sharply when temperatures increase above the minimum necessary for sustained transmission.ConclusionsThe model suggests that, in areas where S. mansoni is already endemic, warming of the water at transmission sites will have differential effects on both snails and parasites depending on abiotic properties of the water-body. Snail generation times will decrease in most areas, meaning that snail populations will recover faster from natural population reductions and from snail-control efforts. We suggest a link between the ecological properties of transmission sites and infection risk which could significantly affect the outcomes of interventions designed to alter water contact behaviour – proposing that such interventions are more likely to reduce infection levels at river locations than lakes, where infection risk remains high for longer. In cooler areas where snails are currently found, increasing temperatures may significantly increase infection risk, potentially leading to new, high-intensity foci of infection.

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Section: Discussionsupporting

confidence: 86%

The Effect of Increasing Water Temperatures on Schistosoma mansoni Transmission and Biomphalaria pfeifferi Population Dynamics: An Agent-Based Modelling Study

McCreesh

Booth

2014

PLoS ONE

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“…Infections by the parasites usually occur in agricultural communities along small streams, irrigation schemes and lakes at altitudes ranging from 1300 to 2000 m above sea level (a.s.l) for S. mansoni and below 800 m a.s.l for S. haematobium [8–10]. Regarding distribution of the two schistosome species in Ethiopia, S. mansoni is widely distributed and S. haematobium is confined to the lowland areas of the country [9]. …”

Section: Introductionmentioning

confidence: 99%

“…Presence of humans carrying the parasites and fresh water bodies harboring the snail intermediate hosts coupled with the suitable climatic conditions contribute to endemicity of both S. mansoni and S. haematobium infections in several localities in Ethiopia [9–16]. Furthermore, population movement and expansion of water resource development projects are playing key roles in establishing the parasite transmission in new areas in the country [9–11].…”

Section: Introductionmentioning

confidence: 99%

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Epidemiology of intestinal helminthiasis among school children with emphasis on Schistosoma mansoni infection in Wolaita zone, Southern Ethiopia

et al. 2017

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BackgroundIntestinal helminth infections are major parasitic diseases causing public health problems in Ethiopia. Although the epidemiology of these infections are well documented in Ethiopia, new transmission foci for schistosomiasis are being reported in different parts of the country. The objective of this study was to assess the prevalence of Schistosoma mansoni and other intestinal helminth infections among school children and determine the endemicity of schistosomiasis in Wolaita Zone, southern Ethiopia.MethodsCross-sectional parasitological and malacological surveys were conducted by collecting stool samples for microscopic examination and snails for intermediate host identification. Stool samples were collected from 503 children and processed for microscopic examination using Kato-Katz and formalin-ether concentration methods. Snails collected from aquatic environments in the study area were identified to species level and Biomphalaria pfeifferi snails, the intermediate host of S. mansoni,, were individually exposed to artificial light in order to induce cercariae shedding. Cercariae shed from snails were used to infect laboratory-bred Swiss albino mice in order to identify the schistosome to species level.ResultsThe overall prevalence of intestinal helminth infections was 72.2% among school children. S. mansoni infection prevalence was 58.6%. The prevalence and intensity of S. mansoni infections varied among schools and sex of children. Swimming was the only factor reported to be significantly associated with S. mansoni infection (AOR = 2.954, 95% CI:1.962-4.449). Other intestinal helminth species identified were hookworms (27.6%), Ascaris lumbricoides (8.7%), E. vermicularis (2.8%), Taenia species (2.6%), T. trichiura (1.2%) and H. nana (0.6%). Only B. pfeifferi snails collected from streams shed schistosome cercariae and 792 adult S. mansoni worms were harvested from mice exposed to cercariae shed from B. pfeifferi on the 6th week post-exposure.ConclusionThe present study found high level of intestinal helminth infections in the study area. The study also confirmed autochthonous transmission and endemicity of S. mansoni as evidenced by both parasitological and malacological findings as well as by further establishing infections in lab-bred mice. Therefore, there is a need to include the area in the control programs with anti-helminth drugs and also consider other complementary measures including sanitation, provision of clean water supply, and snail control.

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“…Thus, intensity of infection is influenced considerably by the frequency, duration and intensity of human contact with infective water. Spatial studies of schistosomiasis, snail intermediate hosts and water resources have been carried out at both the macrogeographical (world-wide, regional, national and district) (Hunter 1981, Doumenge 1987, Kloos et al 1988, Bavia et al 1994) and microgeographical (community) levels (Kloos et al 1983, Lima e Costa et al 1985, Kloetzel 1989, Barreto 1991. Although they use data of different levels of aggregation and specificity, these two types of study can complement each other.…”

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confidence: 99%

Microgeographical patterns of schistosomiasis and water contact behavior; examples from Africa and Brazil

Kloos

Gazzinelli²,

Zuyle³

1998

Mem. Inst. Oswaldo Cruz

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Schistosomiasis in Ethiopia

Cited by 72 publications

References 31 publications

The Effect of Increasing Water Temperatures on Schistosoma mansoni Transmission and Biomphalaria pfeifferi Population Dynamics: An Agent-Based Modelling Study

The Effect of Increasing Water Temperatures on Schistosoma mansoni Transmission and Biomphalaria pfeifferi Population Dynamics: An Agent-Based Modelling Study

Epidemiology of intestinal helminthiasis among school children with emphasis on Schistosoma mansoni infection in Wolaita zone, Southern Ethiopia

Microgeographical patterns of schistosomiasis and water contact behavior; examples from Africa and Brazil

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