Risk factors for bovine viral diarrhea infection

Maria E Negron, Purdue University

Abstract

Bovine viral diarrhea virus (BLVD.) causes a wide range of clinical signs in both dairy and beef cattle including: infertility, abortions, decreased production and increased incidence of respiratory infections. Due to the economical losses caused by BVDV in many countries, several countries of the European Union have established successful control and eradication programs and recently BVDV was included on the OIE list of reportable diseases of cattle. Despite intense vaccination practices in the United States as in other parts of the world, BVDV still continues to be a significant economic burden. Due to different management practices, it is impractical to adopt successful control programs already established in other countries or regions. In fact, control programs should address the particular needs of those specific areas. Furthermore, recent findings suggesting the possibility of wildlife reservoirs present a threat for successful BVDV control and eradication. This thesis aims to elucidate some aspects of BVDV transmission in order to gather knowledge on how to control and potentially eradicate this disease. Our first goal was to better understand the BVDV transmission between cattle and whitetailed deer (WTD). For this study, we assessed the feasibility of BVDV type 1a transmission by direct contact between experimentally infected WTD fawns and naïve colostrum-deprived calves. Fawns were inoculated intranasally with a ncp BVDV-1a isolated previously from free-ranging WTD. Two days post inoculation; fawns were housed with naïve calves until the end of the study. All fawns were successfully infected with BVDV and were shedding the virus through nasal, oral or rectal swabs for up to 18 days post inoculation. Four of the six in-contact naïve calves became infected with BVDV after being housed with infected fawns. On necropsy, no gross lesions were observed and histopathological lesions of infected animals were characteristic of BVDV infection. Our results indicate that transmission of ncp BVDV type 1a from experimentally infected fawns to colostrum-deprived naïve calves is possible. Our second goal was to describe management practices of dairy farms in Indiana by mailing a survey to Indiana producers in order to highlight potential weaknesses in terms of disease control and/or prevention. For this study we wanted to describe management practices, already known to be associated with prevention of BVDV infection, in Indiana dairy farms and determine the distribution of BVDV vaccine use within Indiana dairy herds. All dairy producers under the Indiana Premise ID list (n = 1,600) provided by the Indiana Board of Animal Health were asked to participate in this study. Producers received a letter introducing our study along with a questionnaire and postage paid enveloped. Approximately 4 months after the initial questionnaire was mailed, a second questionnaire was mailed to producers that failed to respond the first time. Returned questionnaires were entered into a data base and descriptive statistics and univariate analysis were performed. A total of 208 questionnaires were eligible for analysis. Based on our results, herds of less than 100 heads comprised the majority of farms in our survey (60.4%), followed by herds with 100-499 heads (32.9%) and herds with more than 500 herds (6.8%). The majority of the farms acquire replacements from external sources (61.8%). Interestingly, a low number of farms perform biosecurity measures against BVDV relying mostly on the use of BVDV vaccines. Our results indicate an association between herd size and better disease prevention practices. Dairy producers should be aware that vaccination should be complementary to a comprehensive biosecurity program. This study, despite of using only a descriptive analysis of the gathered data, highlights the weak points of management practices of BVDV control on Indiana dairy farms.

Degree

M.S.

Advisors

Pogranichniy, Purdue University.

Subject Area

Veterinary services

COinS