In utero egg counts in female Haemonchus contortus from experimentally infected lambs: implications for fertility...

Haemonchus contortus is a highly pathogenic gastrointestinal nematode of domestic and wild ruminants whose epidemiological success is closely linked to high reproductive capacity. For female daily egg output, however, direct observations remain limited, and published estimates vary widely, ranging from fewer than 20 to 10,000-15,000 eggs per female per day. This study assessed in utero egg counts in female H. contortus recovered from experimentally infected lambs in order to evaluate their implications for fertility relative to values commonly cited in the literature. Archived female nematodes from a previously published experiment were used to conduct the study. In total, 147 female worms recovered from 14 sheep were examined. It was found that the average in utero egg count was 345 (SD = 145) eggs per H. contortus female. Regression analysis provided no clear evidence that the experimental design substantially influenced this parameter. In addition, female body length was positively associated with egg counts, though the relationship was not strictly linear. Overall, the present study supports moderate rather than high estimates of female daily egg output for H. contortus.