Seasonal patterns of gastrointestinal nematode infection in goats on two Lithuanian farms

BACKGROUND: This study investigated seasonal changes in naturally acquired gastrointestinal nematode (GIN) infections on two Lithuanian goat farms with different parasite control practices. FINDINGS: On both farms, nematode faecal egg counts (FEC) and larval cultures were obtained from 15 adult and 10 young goats at bi-weekly intervals from April 2012 to April 2013. Goats on farm A were dewormed with ivermectin (0.3 mg/kg body weight) in October/November 2012, whereas the animals on farm B were left untreated. Thirteen young goats were slaughtered in August/November 2012 and April 2013 and worm burdens in the gastrointestinal tract were enumerated. In goats from both farms, Teladorsagia, Trichostrongylus, Oesophagostomum, Chabertia and Haemonchus were the dominant GIN genera. Herbage contamination with infective third-stage larvae (L(3)) peaked in July/August and resulted in high FEC in September/October. Parasitological examination at slaughter showed that Teladorsagia spp. and Haemonchus contortus survived the winter, both in the abomasal mucosa as adults and as early fourth-stage larvae (EL(4)). Deworming on farm A significantly reduced FEC, especially of H. contortus, at the start of the grazing period compared with the untreated farm B (P < 0.05). CONCLUSIONS: Goats were heavily infected with several GIN throughout the year. Strategic anthelmintic treatment during housing significantly reduced nematode egg output, in particular by H. contortus, at the start of the grazing season.