Regional variations in the nematode worm populations of breeding ewes in New Zealand

Authors: Sykes AR, McAnulty RW, Herve M, Logan CM
Publication: New Zealand Veterinary Journal, Volume 51, Issue 4, pp 159-164, Aug 2003
Publisher: Taylor and Francis

Animal type: Livestock, Production animal, Ruminant, Sheep
Subject Terms: Alimentary system/gastroenterology, Biosecurity, Disease surveillance, Epidemiology, Nematode, Parasites - internal
Article class: Scientific Article

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Abstract: AIM: To determine whether the generic composition of nematode parasites in lactating ewes varies between geographic regions in New Zealand and whether age and fecundity of ewes affect nematode egg output.
METHODS: Four ram breeding properties in each of the northern (NNI) and southern (SNI) North Island and the northern South Island (NSI) regions, together with six properties in the southern South Island (SSI) were investigated. Faecal samples were obtained on one occasion, 2–6 weeks after lambing, from at least 60 ewes on each property, stratified according to age and reproductive status. Nematode eggs were counted and coprocultures prepared to identify genera present. Information on the history of anthelmintic use on each property was also collected.
RESULTS: Highest faecal egg counts (FEC) were observed from ewes in the NNI and SSI regions. Lambed hoggets and twin-rearing two-tooth ewes had higher FEC than their unlambed or single-lamb-rearing contemporaries, respectively. However, no significant effect of reproductive effort on FEC was demonstrated in mixed-aged ewes. Significant regional differences in generic composition of nematode parasites were observed: Teladorsagia spp (also referred to as Ostertagia spp) eggs made up 56% of total eggs shed from sheep in the SSI compared with14% in the NNI, and values for Haemonchus spp were 1%and 24% for these same regions, respectively. Trichostrongylus colubriformis and T. vitrinus together made up 7, 15, 13 and15% of eggs counted from sheep in the SSI, NSI, SNI and NNI, respectively.
CONCLUSIONS: More comprehensive epidemiological information may suggest regional-specific approaches to the management of nematode parasites in ewes should be devised in the future.
KEY WORDS: Lactating sheep, nematode epidemiology, New Zealand, geographical regions

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