An Overview of Gastrointestinal Nematode Parasitism in Goats in the Dry Zone of Sri Lanka
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Date
1997-11-22
Authors
Paranagama, W. D.
Journal Title
Journal ISSN
Volume Title
Publisher
University of Peradeniya
Abstract
Gastrointestinal nematode infection is recognised as one of the major constraints in the development of the goal industry in Sri Lanka, particularly in the dry and intermediate zones of the country where over 65 per cent of the total goat population is distributed. This paper reports on three investigations carried out simultaneously to obtain relevant epidemiological data to formulate an effective chemoprophylactic programme to control the infection.
A total of 218 gastrointestinal tracts of goats from the dry zone were examined at necropsy to determine the prevalence of the nematode infection and the species of nematodes, which affected the animals. Two hundred and seventeen (99%) of the animals examined were infected with at least one or more species of gastrointestinal nematodes. The species identified included Haemonchus contortus, Trichostrongylus colubriformis, Oesophagostomum columbianum, Trichuris ovis and Bunostomum phlebotomum. The most prevalent species was O. columbianum while H. contortus; a pathogenic nematode of the abomasum (glandular stomach) was present in 81% of the animals. Although. clear dry and wet seasons were evident in the areas from where the animals were brought, a seasonal pattern of the mean total worm burden was not observed.
The faecal egg counts (EPG), of 218 goats and the worm burdens of the tracer animals were used to investigate the pattern of the natural gastrointestinal nematode infection of goats of the North Central Province of Sri Lanka. In this study, the EPG increased significantly from August to reach a peak during November. The lowest counts were recorded in June. Further, the trend in EPG counts matched the rainfall pattern in the experimental area. This field study also showed a peak EPG during October/November and it coincided with the increase in gastrointestinal nematodes in tracer kids indicating a distinct seasonality in which high EPG occurred during October/November and low counts were present during the months from May to July when the climatic conditions were dry. This finding suggests that gastrointestinal nematode infection is related to the rainfall. Three genera of adult nematodes, namely H. contortus, T. colubriformis and O. columbianum, were present in the area under study. H. contortus was the predominated species.
Furthermore, the effectiveness of three commercially available anthelmintics belonging to benzimidazole and imidathiazole classes were evaluated in goats in order to select the most cost-effective anthelmintic for a chemoprophylactic programme. All anthelmintics tested were equally effective, but pyrantel pamoate was found to be most cost-effective.
These observations serve as a useful guide for the control of gastrointestinal nematodes in the goats in the dry zone of Sri Lanka. Based on these findings it is recommended that an effective anthelmintic treatment just prior to the beginning of the monsoons followed by 1-2 repeated anthelmintic administrations at 3-5 weeks interval during the monsoon would effectively control the infection and minimise the accumulation of infective larvae in the pasture.
Description
Keywords
Veterinary Medicine , Goats , Gastrointestinal , Parasitism
Citation
Proceedings and Abstract of the Annual Research Sessions, November 22, 1997, University of Peradeniya, Sri Lanka pp 141-150