Abomasal parasitism in dairy cows in Belgium.

Over a period of one year, from March 1984 to April 1985, the abomasa of 157 dairy cows in East Flanders (Belgium) were collected and examined for the presence of nematodes. Faeces and blood were also collected from the animals. No worms were recovered from 18 cows (11.5%), 118 cows (75%) had a low to moderate worm burden (10-10,000) and 21 cows (13.5%) a high worm burden (greater than 10,000). The geometric mean total number was 2171. Ostertagia ostertagi and Trichostrongylus axei were the main species involved, with the former accounting for 90% of all trichostrongyles recovered. For both worms a seasonal pattern was evident, with the highest worm counts in December-January. Between December and February greater than 97% of the Ostertagia spp. worm burden were EL4. For all animals the average pepsinogen level was 1391 +/- 494 mU tyrosine with no statistically significant relationship between pepsinogen levels and the total number of gastric nematodes. Only 45% of the faeces samples were positive for strongylid eggs with a mean of 43 eggs per gram. The percentage generic composition of L3 larvae collected from faeces was 62% Ostertagia, 18% Trichostrongylus, 6% Cooperia, 4% Oesophagostomum and 0.2% Bunostomum.