The statistical distribution of trichostrongylid nematodes in grazing lambs

Barger I. A. 1985. The statistical distribution of trichostrongylid nematodes in grazing lambs. International Journal for Parasitology15: 645–649. Worm counts of the genera Haemonchus, Ostertagia, Trichostrongylus and Nematodirus from 104 naturally-infected lambs were found to follow negative binomial distributions. Although mean counts covered a 10-fold range, k values did not differ significantly among the four genera. It was concluded that all genera were equally overdispersed. Some implications of this overdispersion for flock productivity and for parasite control were examined