Infection rates in reactors to an absorbed ELISA used in a test and cull program for bovine Johne's disease

Attitudes towards biosecurity practices relevant to Johne's disease control on beef cattle farms

The success of control programs can be improved when producers' attitudes towards these programs are positive. Implementation of control programs for chronic diseases are more challenging than those for acute diseases because of the absence of the "cues-to-action" that are associated with acute diseases. Johne's disease (JD) is a chronic diarrheal disease of ruminants, and national voluntary control programs exist in several countries. We used a mailed cross-sectional survey to describe the attitudes of producers towards biosecurity practices and veterinarians' beliefs relevant to the control of JD on beef farms. Another objective was to describe and compare the attitudes of producers and veterinarians towards specific measures recommended by the Texas Voluntary Johne's Disease Program (TVJDP) for cattle. Questionnaires were mailed to 1100 producers and 840 veterinarians in the state of Texas, USA. Two hundred and eighty-five producers (26%) and 153 veterinarians (18%) returned questionnaires for analysis. Fifty-nine percent of producers and 50% of veterinarians agreed that JD is responsible for substantial losses in beef cattle production. Sixty-four percent of veterinarians had educated producers on management strategies for the control or elimination of JD. However, only 36% had participated in the training program and 29% were certified to develop risk assessments and implement testing. Only 20% of producers reported that they were familiar with the TVJDP and 16% had considered participating in this program. There is a need for greater promotion of the control program among veterinarians and producers. Reasons for the apparent difference in opinions need to be understood to increase the likelihood of control measures adoption and to subsequently reduce the impact of JD on beef cattle operations.

Effects of Seasonal Climatic Conditions on the Diagnosis of Mycobacterium avium Subspecies paratuberculosis in Dairy Cattle

Validity of Johne's disease programs and control protocols that rely on established cut points [e.g., specified sample-to-positive (S/P) ratios] for ELISA serological tests depends on interpreted results that are not susceptible to variable test accuracy. It was hypothesized that seasonal variability exists in serological response to Mycobacterium avium subsp. paratuberculosis (MAP) infection. Further, a reciprocal response may occur, resulting in greater risk of fecal shedding in subclinically infected animals. A testing regimen was invoked that included multiple testing of individual adult cows during the 4 seasons. Serum was collected on a cyclic, monthly basis from 3 randomly selected cohorts of dairy cows, and fecal samples were collected from the 20% of cows with the greatest ELISA test S/P ratios. Staggered, quarterly sampling was continued for 1 yr, and at the conclusion, serum was analyzed en masse. The ELISA outcome values (i.e., S/P ratio) were treated both as categorical and continuous variables. The potential lagged effects of temperature-related seasonality on S/P ratio, as well as the potential for a change in test result caused by temperature were assessed. Results for fecal culture were analyzed on a categorical scale and compared with the ELISA results to explore the possibility of reciprocal fecal shedding. No significant seasonal effects on either S/P ratios or the proportion of cows seropositive to MAP were observed. Furthermore, no evidence was found linking temperature-related seasonality to a reciprocal increase in the risk of fecal culture positivity for MAP.