Phd Candidates

Thesis / Project  Title: Compatibility of Schistosoma mansoni and its intermediate host snails (Biomphalaria spp) in relation to transmission of intestinal schistosomiasis in Kenya

Thesis / Project  Abstract

Schistosomiasis afflicts an estimated 240 million people worldwide, with majority of the cases occurring in sub-Saharan Africa. In Kenya, Schistosoma mansoni, isthe most widespread among the Schistosoma spp and depends on the freshwater snails in the genus Biomphalaria for its transmission. In this study compatibility and vectorial competencies of 3 Biomphalariaspp were examined.

Reciprocal cross infection experiment using field derived B. pfeifferi from Kirinyaga county and B. sudanica  from Kisumu county in 3 categories based on age/size  was done using sympatric and allopatric S. mansoni and then, using lab-raised F1 generation of Lake Victoria derived B. sudanica and B. choanomphala snails with sympatric and allopatric combinations of S. mansoni in 3 different miracidia dose (1, 5 and 10). Abundance of B. sudanica and B. choanomphala, prevalence of S. mansoni in snail population, hyacinth intrusion, and acquisition of S. mansoni worms by sentinel mice were determined.

It was observed that S. mansoni had higher infection rates in B. pfeifferi (39.6-80.7%) than in B. sudanica (2.4-21.5%) regardless of parasite source or snail size/age.  Cercariae production was greater for B. pfeifferi compared to B. sudanica. B. choanomphala was more susceptible to S. mansoni than B. sudanica (12.7 - 80.8% versus 5.2 – 18.6%). B. sudanica did not differ in relative abundance or prevalence of S. mansoni infections between persistent hotspot and responding villages (P>0.05). B. choanomphala, was significantly more abundant in the persistent hotspot  villages than in responding villages (P<0.05).

Dogs are reservoirs and hosts for several zoonotic parasites of public health significance worldwide. This study established the prevalence and distribution of Echinococcus granulosus sensu lato, Taenia species and other zoonotic intestinal parasites in dogs from cystic echinococcosis endemic areas of Kenya.

Dog faecal samples collected from the environment in Turkana, Meru, Isiolo and Narokcounties were microscopically examined for the presenceof intestinal parasites. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and DNA sequencing were used to genotype hookworms, Echinococcus and Taenia spp.Of the 1,621 faecal samples, 43.24%contained at least one parasite and 11 parasites genera were identified. Ancylostoma caninum (n = 59), A. braziliense (n = 10) and A. cf. duodenale (n = 1) were detected in 70 faecal samples containing hookworm eggs. Eleven percent of faecal samples had taeniid eggs, 4.4% were Echinococcus spp. eggs. Four Echinococcus spp. were identified with E. granulosus sensu stricto and E. canadensis (G6/7) detected in 51 and 23 faecal samples, respectively. E. ortleppi and E. felidis were rare and only detected in 5 and 2 faecal samples respectively. Overall 4.9% faecal samples contained eggs of Taenia or Hydatigera. Taenia hydatigena and T. multiceps were the most frequent, found in 36 and 15 samples, respectively. Other eggs detected in the faecal samples belonged to T. serialis, T. madoquae, T. ovis, T. saginata and Hydatigera taeniaeformis.

This study identified zoonotic parasites in dogs that pose potential public health risk to humans and emphasizes the need toimplement public health control measures.