Variable efficacy of praziquantel among <i>Schistosoma</i> -infected ruminants of northern Senegal—a drug trial and population genetic study across two contrasting epidemiological regions

While efforts to eliminate schistosomiasis as a public health problem gather momentum, the potential zoonotic risk posed by livestock Schistosoma species via viable hybridization in sub-Saharan Africa has only begun to be appreciated. Recent research revealed widescale use and misuse of praziquantel (PZQ) in livestock among subsistence farmers within West Africa, in response to the often high morbidities and mortalities, and hence socioeconomic impact, of animal schistosomiasis. Such findings raised policy discussion into the potential need to formalize livestock schistosomiasis treatments, balanced against the necessity to protect against PZQ resistance. Here, we present results of an anthelmintic efficacy trial in which 25 mg kg-1 of veterinary-formula PZQ was given orally to naturally Schistosoma spp-infected domestic ruminants of northern Senegal. Miracidial reduction rates revealed acceptable efficacy levels within cattle infected with S. bovis, but near zero efficacies in goats and sheep infected with S. curassoni and/or hybrids. Furthermore, increased miracidial output post-PZQ was observed among several individuals, particularly within sheep. There was a significant increase in body condition in both cattle and sheep post-PZQ. Microsatellite molecular markers of parasites from bovines indicated a greater level of population genetic differentiation between pre- and post-PZQ samples than between villages, with a genetic signature of inbreeding in one village with the lowest PZQ efficacy. We discuss our findings in terms of their implications and applications towards reaching the WHO elimination targets and the need for future One Health research. This article is part of the Royal Society Science+ meeting issue 'Parasite evolution and impact in action: exploring the importance and control of hybrid schistosomes in Africa and beyond'.