Worm burdens in cows: the effect of anthelmintic treatment on the parasite egg output

Abstract

The effect on the nematode egg output of anthelmintic treatment with levamisole after parturition was studied in a group of 298 cows on four farms in the province of Groningen, and three farms in the province of Noord-Brabant (The Netherlands). Two faecal samples were taken, the first within 48 h post partum, and the second 14 days later. Half the number of cows were treated after the first sampling. Faecal examinations were made by culturing a fixed amount of faeces, counting the larvae, calculating an LPG (number of larvae per g of faeces) and making a larval differentiation. From the first sampling it became clear that with some exceptions egg output was generally low (mean LPG 7.9). Most of the cows (87.9%) were positive for Ostertagia spp. Of the other species, Trichostrongylus spp. were found in 47.7% of the samples and Cooperia puncatata in 30.5%. Less frequent were Bunostomun phlebotomum (13.1%), Oesophagostomum spp. (9.4%), Cooperia oncophora/surnabada (8.7%) and Haemonchus contortus (7.7%). The latter species was only found on farms in Noord-Brabant and was related to the grazing of sheep on the cattle pastures. In more than 60% of the cows in both provinces with an LPG-value above 20, C. oncophora/surnabada larvae were present, while H. contortus larvae were found in 50% of those cows in Noord-Brabant. Highest counts were generally observed in cows lactating for the first time, but sometimes individual cows of older age showed a high egg output. The highest LPG-value found in this study was 228, in a first-lactating cow. The second sample of treated animals, 14 days after the first, showed that the LPG was significantly reduced from 7.6-1.4 ( P < 0.001), while in the non-treated cows the reduction of the LPG was from 6.7-6.1, which proved to be not significant. However, all species seen prior to treatment were still present after treatment.