Seasonal transmission of Fasciola gigantica infections and the possibility of a strategic anthelmintic control in an endemic area of central Kenya

Abstract

A study to investigate the seasonality of infections with Fasciola gigantica was carried out in Mathira Division of Nyeri District, Kenya from June 1995 to August 1996. Six young Dorper lambs, each less than six months of age. were used as tracers every month for Fasciola infection as they grazed alongside a farmer’s flock. Four adult ewes, permanently grazed on pastures in the study area were also bought from farmers' flocks from the region. These two groups were necropsied after a three and six-week housing period respectively, under worm-free conditions, and the flukes from the livers and lungs were recovered and counted. The tracer lambs had) infections with F gigantica in II out of the 15 months of study with at least half of the group infected in eight months. There were two ' peaks of infections with F: gigantica; August to October 1995 and February to April 1996. The permanent grazers harboured infection in ten out of 15 months, with peak infections in April and July 1996. One ewe had exceptionally high parasite load in July total of 199, with 189 liver flukes in the bile ducts, six in the lungs and.four in the gall bladder). From the results of this study, It IS proposed that one main 'treatment with triclabendazolc instituted in October, when most tracer lambs were. Infected with many F gigantica, can significantly reduce the production losses associated with fasciolosis. Clinical cases could be treated individually whenever they occur during the other times of the year. This proposed treatment regime is intended for areas of the Kenya highlands where fasciolosis is endemic and with similar climatic conditions to the study area.