Helminth parasites of economic importance in cattle in New Zealand

Abstract

Abstract New Zealand farmers are currently spending about $27.9 million/yr on anthelmintics to control helminth parasites in cattle. Productivity trials carried out over the last 30 years show that the benefit‐cost ratio of an effective drench programme is likely to be high, particularly in young animals in their first year, which tend to be very susceptible to infection. In New Zealand, cattle have been recorded as the definitive host of at least 27 nematode species, two trematode species, and one (possibly two) cestode species. Of these, three gastrointestinal nematode species/species complexes, Ostertagia ostertagi/O. lyrata, Trichostrongylus axei, and Cooperia oncophora/C. surnabada are generally considered to be of greatest and most widespread economic importance. In New Zealand, as overseas, bovine ostertagiosis occurs in two clinical forms, referred to as Type I and Type II. Type I ostertagiosis is the normal form of the disease seen in weaner cattle, while Type II ostertagiosis results from the ra...