No barrier breakdown between human and cattle schistosome species in the Senegal River Basin in the face of hybridisation

Prevalence and distribution of schistosomiasis in human, livestock, and snail populations in northern Senegal: a One Health epidemiological study of a multi-host system

“…F1 hybrids accounted for a very low proportion of the hybrid miracidia isolated, suggesting that zoonotic spillover of S bovis is either very infrequent or only occasionally leads to patent infections. 26 , 27 This observation is consistent with the rare identification of S bovis being shed by humans (a single patient identified) in the Corsica outbreak. 17 However, even if zoonotic transmission from livestock occurs only infrequently, the impact of such rare events can be epidemiologically significant, and the number and impact of these events often increase under evolutionary pressure and as systems near elimination.…”

“… 10 Naturally occurring viable hybridisation and introgression (genetic flow from one species to another via repeated backcrossing) between and within human and animal schistosomes—particularly within the Haematobium group—are emerging as topics of major importance for global health and disease control. 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 Anthropogenic changes, such as dam construction, migration of people and their animals, and altered agricultural practices, are predicted to increase opportunities for interspecific exposure and co-infection, and therefore hybridisation. 20 , 22 A recent outbreak of human schistosomiasis in Corsica, France, was found to be caused by both S haematobium and S haematobium– S bovis hybrids (closely related to those found in Senegal); however, a local animal reservoir was not identified despite extensive sampling.…”

“… 29 By contrast, livestock schistosomiasis has received little attention in Senegal, with no recent, publicly available surveillance data. 25 , 26 The primary objective of this study was to elucidate the multi-host, multi-parasite transmission cycle of zoonotic schistosomiasis in sub-Saharan Africa, and the implications for human and animal health, by conducting systematic surveys across multiple potential definitive hosts (humans, cattle, sheep, and goats) and snail intermediate hosts in two putative hybrid hotspot areas of contrasting anthropogenic change in northern Senegal. This incorporated testing the hypothesis that S haematobium or S haematobium hybrids might be able to infect livestock species, and that (if present) they may be located in, and transmitted via, the urinary system—an aspect of transmission that has not previously been fully explored.…”

Interactions between Schistosoma haematobium group species and their Bulinus spp. intermediate hosts along the Niger River Valley

“…These hybrids appear to be introgressed forms, with parts of the S. bovis genome introgressed into S. haematobium, leaving two differentiated parental populations that are not panmictic or leading to hybrid speciation. This was also reported in recent studies in Senegal [58] and Niger [59], and indicates that more research is warranted to understand S. haematobium group species hybridisation, the effect of hybridisation on definitive host range [13] and the potential human and veterinary impacts [60].…”

Future schistosome hybridizations: Will all Schistosoma haematobium hybrids please stand-up!

“…Seminal field-based parasitological surveys in Senegal, molecularly characterizing schistosome populations [1], have questioned these assumptions, bringing to light novel genetic interactions of S. haematobium and S. bovis [11]. With increasing geographical sampling, broader interspecies interactions with S. curassoni have been revealed [12], although a recent microsatellite analysis of Senegalese S. haematobium and S. bovis populations has shown no genetic admixing [13]. Nevertheless, the S. haematobiumbovis hybrid has been recently flagged in autochthonous transmission of urogenital schistosomiasis on Corsica [8]; neither inspected livestock nor rodents appear to sustain transmission locally, which is most likely of human-origin(s) and imported input(s) alone [14].…”