Abstract:
Background: Trematode infections, including schistosomiasis, are neglected tropical zoonotic diseases of significant medical and veterinary importance in Africa. Transmission cycles of these diseases involve an interplay between the definitive (human and livestock) and intermediate (snail) host of causative trematode parasites. The relative prevalence and spatial distribution of the parasites among and between definitive and intermediate hosts in northwestern Tanzania are poorly understood.
Methods: We conducted a cross-sectional survey on the prevalence and distributions of the parasites among and between the hosts in northwestern Tanzania to establish possible links or associations between the prevalence of the parasites and their respective hosts, with potential application in One Health approaches to control of trematode-associated diseases. We collected snail (Bulinus nasutus and Lymnaea natalensis) specimens from aquatic habitats (rivers, ponds, and wells) with or without vegetation and fecal and urine samples from humans (males, females, children, and adults) and fecal samples from livestock (cattle, sheep, and goats) across northwestern Tanzania in 2024. We separately induced shedding of trematode cercariae from the snail species and identified schistosome/Fasciola cercariae and species where possible, using their diagnostic morphology. We isolated trematode eggs from human fecal and urine samples using Kato-Katz and urine filtration techniques, respectively, and 2) livestock fecal samples using sedimentation and Mini-FLOTAC techniques, and identified the species of trematodes present through their diagnostic morphology.
Results: We collected 2013 B. nasutus and 626 L. natalensis snails respectively. Among these, 2.98% and 4.15 % of B. nasutus and L. natalensis respectively were infected with schistosomes and Fasciola parasites. The proportion of B. nasutus shedding schistosome cercariae did not significantly vary across regions, districts, villages, waterbody type or by waterbody usage. Unlike to L. natalensis, the proportion of Fasciola infections was higher in Sengerema district than Busega and Misungwi districts. Similarly, across villages, Kasungamile village had a higher proportion of Fasciola infections compared to other villages examined. We collected fecal and urine samples from 668 males and 686 female participants. Among these populations, the prevalence of Schistosoma haematobium was significantly higher in males than in female participants (χ² = 8.1465, df = 1, p-value = 0.004314). Adolescents aged 12-21 years had significantly higher S. haematobium infections than other age groups (χ² = 10.443, df = NA, p-value = 0.02999). Among the human fecal samples, the prevalence of S. mansoni infections among participants was very low, with no significant difference across study participants. We detected Schistosoma bovis, giant/large liver fluke (Fasciola gigantica), and stomach flukes or rumen flukes (Paramphistomes) in fecal samples from 828 cattle, 690 goats, and 662 sheep across the study sites. Among the trematodes, the paramphistome, Fasciola, and Schistosomes constituted about 64, 35, and 1 % of the trematodes detected. A Mann-Whitney U test showed that there was a significant difference between F. gigantica (W = 722092, p-value < 2.2e-16), Paramphistome (W = 810454, p-value < 2.2e-16), and schistosome W = 557566, p-value = 2.691e-16) trematodes detected using mini-FLOTAC and sedimentation techniques.
Conclusion: Schistosome infections in humans are predominant; in contrast to livestock and B. nasutus snails, the control measures should focus on preventing human contact with waterbodies harboring B. nasutus snails to break the human-snail-humans schistosome transmission cycle. A separate integrated control strategy in livestock for trematode infections is therefore warranted.
Biography:
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