A case control study of Bovine Viral Diarrhea Virus (BVDV) Persistent Infection (PI) in Betsukai, Hokkaido, Japan.

Abstract

The Betsukai town office implemented bovine viral diarrhea virus (BVDV) preventive activities (i.e., vaccination and surveillance) in 2006. Using bulk tank milk screening followed by individual blood tests using a Reverse Transcription-Polymerase Chain Reaction (RT-PCR) method, persistent infection (PI) cattle were detected and eliminated from the population. Based on data for PI cattle detected between 2006 and 2007, we conducted a case control study to find risk factors associated with the presence of PI cattle. Significantly associated farm level factors for increasing risk of producing PI cattle include; 1) no recent purchase of cattle (between 2004 and 2007) and 2) no prevention of people/animals entering the premises. This study suggests that not only vertical transmission from dam to calf but also indirect contact with people and animals play an important role in transmitting BVDV infection and subsequent production of PI animals.