Ruminant Parasitic Gastroenteritis: Some Observations on Epidemiology and Control

The studies described in this thesis were carried out to assess the advantages and disadvantages of two well recognised means of gastrointestinal parasite control in cattle i.e. anthelmintic prophylaxis and grazing management. In addition studies were initiated to examine the role of Nematodirus battus in outbreaks of parasitic helminthiasis in calves

How hosts control worms

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Ostertagia spp., rumen fluke and liver fluke single- and poly-infections in cattle: an abattoir study of prevalence and production impacts in England and Wales

This study aims at investigating the occurrence, risk factors and production impacts on beef carcassparameters of three of the most important cattle helminth infections in England and Wales. Abomasa, reticulorumens and livers from healthy cattle were collected and examined post-mortem quarterly over a one year period in an abattoir in South-West England. Specific viscera from 974 cattle were collected,examined and scored for Ostertagia spp., adult rumen fluke and liver fluke lesions/presence. A total of89%, 25% and 29% of the carcasses had lesions/presence of Ostertagia spp., rumen fluke and liver fluke, respectively, and 39% had presence of helminth co-infection. Animal demographic and carcass parameters associated with helminth infections were investigated using multi level multinomial and multilevel linear mixed models respectively. After adjusting for other factors, significant differences in the distribution of helminth infections were observed among cattle by type of breed, animal category (cow, heifer, steer and young bull), age, season and concurrent helminth infections. Compared to carcasses free of helminths, carcasses presenting solely Ostertagia Spp. lesions or adult rumen fluke had significantly lower cold carcass weight (coef.: −30.58 [−50.92;−10.24] and −50.34 [−88.50;−12.18]) and fat cover-age (coef.: −3.28 [−5.56;−1.00] and −5.49 [−10.28;−0.69]) and carcasses presenting solely liver flukelesions had significantly lower conformation grade (coef.: −3.65 [−6.98;−0.32]). Presence of helminth poly-infections was negatively associated with cold carcass weight

Population study of bovine ostertagia spp infective larvae on herbage and in soil

Herbage and stratified soil samples from a previously grazed calf pasture were collected regularly over a 12 month period (October 1979 to September 1980). Infective larvae of cattle Ostertagia spp (OL3) were present on each occasion to a depth of at least 15 cm. Analysis of the vertical distribution of the OL3 suggested a possible downward migration during the winter, followed by an upward trend in the spring and summer. The number of OL3 present in the root mat in august 1980 was estimated as 6.4 x 10(6) per hectare, a similar figure to that estimated for the previous November (6.6 x 10(6)) despite the absence of contamination during this period

Prediction model for bovine ostertagiasis

A mathematical model based on development and mortality rates, and incorporating data on the infectivity, fecundity and migratory behaviour of Ostertagia ostertagi, was used to predict the level of pasture contamination and the occurrence of clinical ostertagiasis in grazing calves during 1975 and 1976. A comparison of the predicted and observed events showed a good correlation