Seasonal distribution of gastrointestinal nematode infections in sheep in a semiarid region, northeastern Brazil

Maria De Fátima De Souza,Manoel Pimentel-Neto,Albeísa Cleyse Batista Farias,Rízia Maria Da Silva,Marcos Pezzi Guimarães,André Luís Santos De Pinho

doi:10.1590/s1984-29612013000300006

Abstract

The objective of this study was to determine the seasonal distribution and gastrointestinal nematode parasite load in crossbred Santa Inês tracer lambs, and to correlate the rainfall during the study period with occurrences of parasitic infections. Sixty-four male tracer lambs between the ages of four and eight months were used in the study. Two tracer lambs were inserted into the herd every 28 days to determine the pattern of infective larvae available in the environment. Variation in the fecal egg count (FEC) of nematodes was observed at the study site, with many samples containing undetectable parasite loads during the dry season. The larvae identified in coprocultures were Haemonchus sp., Trichostrongylus sp., Cooperia sp., Strongyloides sp. and Oesophagostomum sp. The nematodes recovered at necropsy were Haemonchus contortus, Trichostrongylus colubriformis, Cooperia punctata, C. pectinata, Trichuris sp., Oesophagostomum sp. and Skrajabinema ovis. The total number of larvae and the total number of immature and adult forms recovered from the tracers showed seasonal distributions that significantly correlated with the amount of rainfall received that month (p value ≅ 0.000 in all cases ). The species H. contortus was predominant in the herd and should be considered to be main pathogenic nematode species in these hosts under these conditions.

Highlights

The sheep industry is a traditional activity comprising small farms and subsistence animal-rearing in the northeastern region of Brazil (JESUS-JUNIOR et al, 2010; SIMPLÍCIO et al, 2003), and 56.7% of the national sheep flock is found there (IBGE, 2010).This activity provides an alternative supply of meat and dairy products, contributing towards improving the food quality of the rural population and keeping people settled on the land (LEITE, 2004)
The nematodes recovered at necropsy were Haemonchus contortus, Trichostrongylus colubriformis, Cooperia punctata, C. pectinata, Trichuris sp., Oesophagostomum sp. and Skrajabinema ovis
The great variation in the fecal egg count (FEC) in tracer lambs was due to the occurrence of a few cases with high numbers of parasites (UENO; GONÇALVES, 1988) and the high frequency of samples in which parasite loads were not detected

Summary

Introduction

The sheep industry is a traditional activity comprising small farms and subsistence animal-rearing in the northeastern region of Brazil (JESUS-JUNIOR et al, 2010; SIMPLÍCIO et al, 2003), and 56.7% of the national sheep flock is found there (IBGE, 2010). This activity provides an alternative supply of meat and dairy products, contributing towards improving the food quality of the rural population and keeping people settled on the land (LEITE, 2004). With regard to sanitary management, one of the most important issues in connection with the sheep industry is infection by parasites of the sheep’s gastrointestinal tract (VIEIRA et al, 1997; SILVA et al, 1998), since these can cause metabolic and systemic changes that affect animal growth and milk and wool production (DARGIE; ALLONBY, 1975; HOLMES, 1987; FOX, 1997).

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