A survey of the prevalence of Nematodirus spathiger and N. filicollis on farms in the North and South Islands of New Zealand

Aim: To compare the prevalence of Nematodirus spathiger and N. filicollis on a sample of farms in the lower South Island with the lower and central North Island of New Zealand by way of a presence/absence survey.

Methods: A presence/absence non-random survey was conducted in which pooled faeces from lambs from 50 farms in the lower and central North Island (n=22) and lower South Island (n=28) were cultured, with and without a post-culture period of chilling, to produce third-stage parasitic nematode larvae (L3). After recovery using the Baermann technique, individual L3 were identified to Nematodirus spp. using a PCR assay. This identified the species that were present on each farm that were then used to compare the regions.

Results: Nematodirus filicollis was present in 38/50 (76%) samples from which Nematodirus spp. larvae were cultured, compared with 50/50 (100%) in the case of N. spathiger. No regional differences were observed in the prevalence of either species (p=0.74). Of the Nematodirus spp. L3 recovered from the unchilled samples, 415/428 (97%) were N. spathiger and 13/428 (3%) N. filicollis. After chilling 594/695 (85%) of the Nematodirus spp. L3 were N. spathiger and 101/695 (15%) were N. filicollis.

Conclusion: Despite the non-random nature of the study, the evidence suggests that both these species are likely to occur sympatrically on most sheep farms throughout New Zealand. In general N. filicollis eggs did not hatch without a period of chilling and this has implications for the identification of these larvae using conventional culture methods.