An Epidemiological Investigation of Ruminant Helminthoses in Smallholder Farms in Central Kenya

Nginyi, Joseph Mwangi (1999) An Epidemiological Investigation of Ruminant Helminthoses in Smallholder Farms in Central Kenya. PhD thesis, University of Glasgow.

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The aim of this study was to investigate the pattern of infection with gastrointestinal nematodes and liver flukes (Fasciola gigantica) in ruminants on smallholder farms in central Kenya and, based on the information gained, design and test strategic anthelmintic control strategies against current control practices in order to make recommendations for future helminth control in this and other similar areas of Kenya. The objective of the first part of the study was to gather together the available information from local farmers, veterinary extension staff and the local veterinary investigation laboratory. This was followed by a detailed epidemiological investigation of helminth infections in ruminants in Mathira division, Nyeri district. All ruminant livestock in 58 randomly selected smallholder farms were faecal sampled every month for nematode and trematode egg counts and pasture samples were collected from 8 communal grazing sites in the study area to assess pasture levels of nematode larvae. Six tracer lambs were introduced in the area and four local permanently grazed sheep were purchased every month for post mortem worm burden estimations. A strategic treatment programme was designed on the basis of this investigation and was compared with current helminth control practices in 80 smallholder farms for both small ruminants and cattle. During this period monitoring of the patterns of infections with nematodes and liver flukes continued. Interrogation of laboratory records over a 10 year period showed that infection with parasitic gastrointestinal nematodes was more often diagnosed in small ruminants whereas F. gigantica infection was more common in cattle. The majority of ruminants were at pasture permanently with a high proportion grazing on communal pastures. Local farmers relied on the use of anthelmintics alone for helminth control, treating small ruminants 1-4 times (mean 3.3) and cattle 1-8 times (mean 3.5) a year. Sheep and goats on smallholder farms had the highest level of infection with gastrointestinal nematodes during the two rainy seasons, especially in March, April and October. Haemonchus contortus was the most predominant nematode species found in the tracer lambs, but in the permanently grazed sheep Trichostrongylus spp. were more abundant. Based on these results, two strategic treatments annually, one in January and one in October, were suggested for the control of gastrointestinal nematodes in small ruminants. The mean prevalence of F. gigantica infections in sheep and cattle was 5.6(+/-3.2)% and 13.0(+/-6.2)% respectively and most infections were recorded during the rainy seasons. Periods of peak pasture infectivity with F. gigantica metacercariae were recorded during the dry season and early in the wet season. A single treatment in October with triclabendazole or three annual treatments in April, June and October using other fasciolicides were suggested for the control of fasciolosis in cattle. The strategic treatment for gastrointestinal nematodes in sheep and goats resulted in lower mean faecal egg counts in treated animals for most of the study period but overall, there was no significant effect of strategic treatment over existing treatments on FEC, birth weight and growth rate in lambs and kids. With regard to fluke treatments there were no significant variations in the proportions of cattle infected with liver fluke or in the daily weight gains in calves attributable to the strategic treatment over the study period. This study succeeded in generating valuable and new epidemiological information on helminth infections of ruminants in smallholder farms in the high potential areas of central Kenya. However, it failed to demonstrate significant advantages of the strategic treatments over the existing helminth control practices. The performance of these treatments, assuming a high adoption rate in specific localities, needs to be evaluated over a longer period of time. Results from such trials would form the basis for recommendations of the strategic treatments to many other areas of Kenya.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Adviser: J L Duncan
Keywords: Veterinary science, Animal diseases, Parasitology
Date of Award: 1999
Depositing User: Enlighten Team
Unique ID: glathesis:1999-75948
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 19 Dec 2019 09:15
Last Modified: 19 Dec 2019 09:15

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