Survey description of down-cows and cows with progressive or non-progressive neurological signs compatible with a TSE from veterinary-client herds in 38 states

Abstract

The surveillance efforts to detect a potential transmissible spongiform encephalopathy (TSE) disease in US cattle have been in place since 1990. This monitoring programme is vital to US interests as it assures the American public and foreign governments of the freedom from TSEs in the US cattle population. The objective of this study was to collect data from practicing veterinarians that would describe non-ambulatory or "downer-cows" in the US cattle population. A second objective was to estimate rates for progressive central nervous system (CNS) conditions potentially compatible with a TSE and determine if affected by regional and herd-size differences. The design of this study was to survey veterinary members of the American Association of Bovine Practitioners (AABP) and compile the data from downer cows as reported from their clients' dairy and beef herds. For non-ambulatory dairy cows with non-progressive neurological signs (NANP), 85% of cases fell into three cause categories: injury/trauma, septicaemia/toxaemia or non-responsive milk fevers. For beef cows, injury/trauma, septicaemia/toxaemia and other known CNS disorders cases accounted for the majority (76%) of NANP cows. The profile of the progressive CNS cases in dairy cattle found that other known CNS conditions, septicaemia/toxaemia, unknown CNS conditions and non-responsive milk fever to be the most frequently reported causes. In beef cattle four case categories accounted for 88.4% of the total reported causes: injury/trauma, known infectious agent, septicaemia/toxaemia and known CNS conditions. There were regional and herd-size effects on the percentages and rates for unknown cases and non-recovered, progressive CNS rates. Non-recovery rates for progressive cases were >400/106 in the south central and northeast regions. Dairy cattle in the southeast had the highest incidence of progressive and unknown CNS disorders. The same was found for beef cows in the southeast. Results of the herd-size analysis showed that dairy herds with <50 cows and beef herds with <100 cows were at the highest risk for unknown non-progressive plus unknown and total progressive cases in this study. Suggested minimum numbers of tests for surveillance were constructed to account for regional and herd-size differences.