Prevalence and Molecular Characterization of Cystic Echinococcosis in Livestock, Echinococcus Infection and the Risk Factors in Dogs in Kajiado-West Sub-County, Kenya

Abstract

Cystic echinococcosis (CE) is a neglected zoonotic disease globally. In Africa CE is highly endemic in east Africa and northern Africa but rare or absent in central African and west African countries. CE is caused by the dog tapeworm Echinococcus granulosus sensu lato, and is more frequent in livestock rearing areas, where people live a nomadic lifestyle. The aim of this study was to establish the prevalence of cystic echinococcosis in cattle, sheep and goats and Echinococcus infection in dogs in Kajiado-West Sub-county. The study also identified Echinococcus species in livestock and dogs and assessed risk factors associated with Echinococcus infection in dogs. In total, 1,486 carcasses slaughtered in Kiserian and Keekonyokie slaughterhouses (388 cattle, 625 sheep and 473 goats) were examined for presence of hydatid cysts in various organs of the thoracic and abdominal cavities. Every cyst was separately preserved in 80% ethanol. Dog faecal samples were collected from the environment (ground) in three wards (Kiserian, Keekonyokie and Magadi) of Kajiado - West Sub county and preserved in 80% ethanol. Taeniid eggs were isolated using zinc chloride flotation-sieving technique and microscopically examined. Protoscoleces or tissue materials from cysts and eggs from faecal samples were picked under the microscope, lysed and genotyped by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and sequencing. The prevalence of CE was 15.2% (72/473) in goats, 14.9% (93/625) in sheep and 14.2% (55/388) in cattle). Out of the 421 cysts isolated, 389 were successfully characterized as E. granulosus sensu stricto (s. s.), 356/389 (91.5%), E. canadensis (G6/7), 26/389 (6.7%), or E. ortleppi, 7/389 (1.8%) respectively, while 32/421 (7.6%) could not be determined. Prevalence of taeniid infection (by microscopy) in dogs was 5.5% (19/345). However, by PCR taeniid eggs from only 8/19 faecal samples yielded PCR products. The prevalence of Echinococcus infection in dogs was 0.6% (2/345) by PCR. Two faecal samples contained a single egg of E. equinus (G4) and E. felidis each. Four Taenia species (1.2%) were identified in dogs; T. multiceps (3/345), T. ovis (2/345), T. hydatigena (1/345) and an unknown Taenia spp. (1/345) by sequencing. This is the first study to report E. equinus in dogs in Kenya. The detection of all the five species of E. granulosus s. l. in a single study is also reported for the first time in Kenya. This study confirms predominance of E. granulosus s. s. in livestock in Kajiado County. The importance of E. ortleppi and E. canadensis (G6/7) in our study was higher as compared to a previous study. More so, a high infection pressure for humans by E. granulosus s. s. based on its abundance could be speculated. The presence of T. hydatigena, T. multiceps and T. ovis in domestic dogs confirms the existence of ongoing transmission of cestodes from livestock to dogs even in absence of the major Echinococcus species (E. granulosus s. s., E. canadensis (G6/7) and E. ortleppi in dogs in this study. The presence of E. felidis and unknown Taenia spp. in faecal samples from dogs indicates a possibility that dogs are the link between the domestic and sylvatic cycles. Integrated control programs focusing on interrupting transmission from dogs to livestock and humans is recommended.