Nematode parasites in young cattle: what role for unexpected species?

Abstract

AIMS

To investigate the timing of infection of beef calves with sheep nematode species on three sheep and beef farms, and to determine the prevalence of cross-infection in calves before weaning across a larger number of farms.

METHODS

Farms in the Far North, Gisborne and Tararua districts, in the North Island of New Zealand, were enrolled in 2014. Fresh faecal samples were collected from approximately 10 calves on each farm between birth and up to 5 months after weaning. In 2016, faecal samples were collected from calves before weaning from 22 farms across the upper North Island. For both trials faecal samples were assessed for faecal nematode egg counts and cultured to determine parasite genus. For samples from the three farms, larvae were identified to species using a multiplex PCR assay.

RESULTS

On the three farms, the median percentage of sheep nematode species detected in faecal cultures was 25 (min 3, max 77)%. The main sheep species detected were Cooperia curticei and Haemonchus spp. (putatively contortus). In faecal samples collected before weaning from 22 farms, Haemonchus spp. were present in 19/22 samples, and the median prevalence was 15 (min 0, max 73)% of the total larvae cultured.

CONCLUSIONS AND CLINICAL RELEVANCE

The implications of sheep nematode species being present in calves should be considered by farmers and veterinarians when undertaking anthelmintic efficacy testing, as they may contribute to false conclusions regarding anthelmintic efficacy. Pre-weaning calves may also be a possible source of contamination and/or refugia for Haemonchus spp. on farms and should be considered when developing parasite control plans for sheep.

KEY WORDS:

• Calves
• Haemonchus contortus
• sheep
• Cooperia species
• Ostertagia species

Acknowledgements

The authors thank the farmers and veterinarians who collected and sent in samples as part of the surveys, without their assistance there would be no data. Wendy Taylor and Barbara Adlington assisted with laboratory work, while Richard Shaw and Christian Sauermann along with two anonymous referees made helpful comments on an earlier manuscript. This work was funded by Beef + Lamb NZ.