Adult schistosomes have an epithelial bacterial population distinct from the surrounding mammalian host blood.

BACKGROUND: Schistosomiasis is a neglected tropical parasitic and chronic disease affecting hundreds of millions of people. Adult schistosomes reside in the blood stream of the definitive mammalian host. These helminth parasites possess two epithelial surfaces, the tegument and the gastrodermis, both of which interact with the host during immune evasion and in nutrient uptake. METHODS: Female ARC Swiss mice (4-6 weeks old) were infected percutaneously with Schistosoma japonicum cercariae freshly shed from Oncomelania hupensis quadrasi snails (Philippines strain). Fluorescent in situ hybridisation (FISH) was performed by using fresh adult S. japonicum perfused from those infected mice. Adult S. japonicum worms were processed to isolate the tegument from the carcass containing the gastrodermis; blood and bile were collected individually from infected and uninfected mice. Total DNA extracted from all those samples were used for microbiome profiling. RESULTS: FISH and microbiome profiling showed the presence of bacterial populations on two epithelial surfaces of adult worms, suggesting they were distinct not only from the host blood but also from each other. Whereas microbial diversity was reduced overall in the parasite epithelial tissues when compared with that of host blood, specific bacterial taxa, including Anoxybacillus and Escherichia, were elevated on the tegument. Minimal differences were evident in the microbiome of host blood during an active infection, compared with that of control uninfected blood. However, sampling of bile from infected animals identified some differences compared with controls, including elevated levels of Limnohabitans, Clostridium and Curvibacter. CONCLUSIONS: Using FISH and microbial profiling, we were able to demonstrate, for the first time, that bacteria are presented on the epithelial surfaces of adult schistosomes. These schistosome surface-associated bacteria, which are distinct from the host blood microenvironment, should be considered as a new and important component of the host-schistosome interaction. The importance of individual bacterial species in relation to schistosome parasitism needs further elucidation.

Schistosomiasis.

Schistosomiasis (bilharzia) is a neglected tropical disease caused by parasitic flatworms (blood flukes) of the genus Schistosoma, with considerable morbidity in parts of the Middle East, South America, Southeast Asia and, particularly, in sub-Saharan Africa. Infective larvae grow in an intermediate host (fresh-water snails) before penetrating the skin of the definitive human host. Mature adult worms reside in the mesenteric (Schistosoma mansoni and Schistosoma japonicum) or pelvic (Schistosoma haematobium) veins, where female worms lay eggs, which are secreted in stool or urine. Eggs trapped in the surrounding tissues and organs, such as the liver and bladder, cause inflammatory immune responses (including granulomas) that result in intestinal, hepato-splenic or urogenital disease. Diagnosis requires the detection of eggs in excreta or worm antigens in the serum, and sensitive, rapid, point-of-care tests for populations living in endemic areas are needed. The anti-schistosomal drug praziquantel is safe and efficacious against adult worms of all the six Schistosoma spp. infecting humans; however, it does not prevent reinfection and the emergence of drug resistance is a concern. Schistosomiasis elimination will require a multifaceted approach, including: treatment; snail control; information, education and communication; improved water, sanitation and hygiene; accurate diagnostics; and surveillance-response systems that are readily tailored to social-ecological settings.

[Bacterio-parasitic interactions. Enterobacteria and schistosomes (Salmonella - schistosome association)]. / Interactions bactério-parasitaires. Enterobactéries et schistosomidés (salmonello-schistosomo-synusies).

The description of a case imported from Chad of an association of Salmonella typhi - Schistosoma haematobium and, in this connection, a new revised general account. The association Salmonella-Schistomas is wide-spread. It corresponds to a salmonello - schistosomo - micro - association by the fixation of precise bacteria in the case of a bacteriemia on the cutaneous surface of male schistosomes in clearly defined places. These Salmonella constitute a permanent antigenic solicitation and they are capable of mobilization and rejection (bacteriuria after passage through the blood-stream) whereas bacteriosis remains asymptomatic. In fact, on the practical level, a clear and absolute distinction must be made between:--the bacteriemia with the concomitant bacteriuria, which are largely physiological in nature, very frequent and originating from various germs, connected with the emunctory function of the kidneys and which can be observed in any subject.--the schistosomal bacteriuria which are specific entities and evidence of a veritable micro-association of a symbiotic nature between the Salmonella and the schistosome, a micro-association which the bacteriuria reveals unexpectedly whereas the clinical symptoms are absent, not clearly discernible or totally misleading.