Influence of age, grazing system, season and agroclimatic zone on the prevalence and intensity of gastrointestinal strongylosis in Ugandan goats

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Abstract

The influence of various factors on the level of strongyloid infection and worm-egg output of goats in Uganda was assessed. Faecal examination of 1661 goats was carried out in four different agroclimatic zones in Uganda between November 1996 and August 1997. Generally, grazing system, season and agroclimatic zone were the only factors found to have a significant (P<0.001) influence on the intensity of gastrointestinal nematode infections in goats, but age did not. Age, grazing system, season and agroclimatic zone were found to have a significant (P<0.001) influence on the level of risk of nematode infections. The results of this study indicate that epidemiological factors have significant influence on the level of risk of gastrointestinal nematode infections and on the worm-egg output in goats, under field conditions with very little helminth control practice in Uganda.

Introduction

The goat population in Uganda is currently estimated at 6.2 million goats. Goats are important in Uganda as producers of meat, as it is generally preferred over other meats. Socio-economically, goats play a traditional role as part of a dowry and as a financial asset (Okello and Obwolo, 1984). In addition, goats provide resource-poor farmers, especially women, with income, manure and needed animal protein in the form of meat and milk. However, the productivity of goats is constrained by parasitic infections, the most important of all being gastrointestinal nematode infections that cause production losses and death of infected animals.

Control of gastrointestinal nematode infections in goats in Uganda relies on anthelmintic treatments (Magona and Musisi, 1999). However, anthelmintic treatments are prohibitively costly to many smallholder goat farmers in Uganda. Moreover, present control strategies for ruminant parasitic nematodes worldwide are complicated by the problem of anthelmintic resistance, particularly in Haemonchus contortus in the southern hemisphere (Van Wyk and Malan, 1988, Waller et al., 1996). Designing and planning of alternative low-cost control strategies requires knowledge of the epidemiological factors that influence the risk of gastrointestinal nematode infections. However, little or no information has been documented about the epidemiology of gastrointestinal nematode infection in goats in Uganda. The objective of this study was to determine the most important epidemiological factors that influence the level of risk of gastrointestinal strongylosis and worm-egg output in goats in Uganda.

Section snippets

Study area

Goats were randomly sampled in four different districts, each of which represented one of the four distinct agroclimatic zones of Uganda, namely, humid high-altitude, semi-humid to semi-arid, sub-humid and semi-humid. The humid high-altitude zone receives an annual rainfall of 1500 mm and has daily mean temperatures ranging between 10 (minimum) and 28 °C (maximum). The semi-humid to semi-arid zone receives an annual rainfall of 875–1000 mm and has daily mean temperatures ranging between 17

Results

Table 1, Table 2 show the factors that influence the worm-egg output, while Table 3 shows the factor levels which have significant influence on worm-egg output. Generally, grazing system, season and agroclimatic zone were the factors that had a significant (P<0.001) influence on the intensity of gastrointestinal nematode infections in goats, but age did not.

Though young goats had higher mean worm-egg counts than adults, they were not significantly different. Goats kept under zero-grazing had a

Discussion

In the present study, grazing system, season and agroclimatic zone were found to have significant influence on worm-egg output in goats. As regards risk of nematode infection, all factors including age had a significant influence. Contrary to this study, age has been reported in other studies to have a significant influence on the worm-egg output (Assoku, 1981). A steady decline in worm-egg output is reported to occur during the first year of life and after which, the worm load stabilises and

Conclusion

Age, grazing system, season and agrolimatic zone are important factors that influence risk of gastrointestinal nematode infections, but only grazing system, season and agroclimatic zone significantly influence worm-egg output in goats in Uganda. A further study looking at goats of less than 1-year-old is recommended to define, if there is a change over this period in susceptibility to nematode infections.

Acknowledgements

We thank Messrs Joseph Muboli and Philip Jamugishanga for their technical assistance. This paper is published with the kind permission of the Director, Livestock Health Research Institute, Tororo, Uganda.

References (16)

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