Seasonal dynamics of Ostertagia ostertagi infection in lactating Holstein-Friesian cows on a dairy farm in Hokkaido, Japan.

Gastrointestinal nematodes (GINs), such as Ostertagia ostertagi and Cooperia spp., are common in cattle worldwide. Although infected cattle are often asymptomatic, production is negatively affected. The present study investigated whether eggs per gram (EPG) of GINs in 32 lactating cows decreased during winter and increased as it became warmer. Larvae recovered by coprocultures mostly consisted of O. ostertagi in autumn, while three GINs, Ostertagia, Trichostrongylus and Meistocirrus, were collected in spring. Daily milk and bulk tank milk samples from cows previously infected with O. ostertagi contained O. ostertagi antibodies based on ELISA developed using SVANOVIER® O. ostertagi-Ab in all survey periods. Even if the faecal diagnosis was negative for GINs, infection was still possible. Therefore, the administration of anthelmintic drugs is recommended.