David W. Hird

Case-control study of papillomatous digital dermatitis in southern California dairy farms.

Abstract Data from 37 southern California dairy farms, with an annual average proportion of > 5% of cows affected by papillomatous digital dermatitis (PDD) (cases), were compared with those from 20 dairy farms with ≤ 5% cows affected (controls). Information on dairy environment, management and PDD occurrence was obtained from dairy managers, veterinarians and hooftrimmers, and by direct measurements at the farms. Odds of having a higher proportion (> 5%) of cows affected were about 20 times greater in dairy farms with muddier corrals than in drier dairy farms. Buying replacement heifers was associated with a 4.7-fold increase in the odds of higher PDD prevalence, compared to dairy farms that did not buy heifers. In addition, a positive association was found between risk and number of heifers purchased. Spatial analysis (used to examine distribution patterns of the study dairy farms) showed no evidence of clustering among case or control dairy farms. There was no association between case dairy farms and proximity to the major local river.

Papillomatous digital dermatitis on a commercial dairy farm in Mexicali, Mexico: Incidence and effect on reproduction and milk production

This retrospective study of papillomatous digital dermatitis (PDD) was performed using data for cows that calved between July 1993 and June 1994 on a Mexicali, Mexico, dairy farm in order to calculate incidence rates, and to compare milk yield and reproduction data between affected and nonaffected dairy cows. A total of 190 out of 577 (33%) cows were affected during lactation and six (1%) during the dry period. Fifty-two of 77 (68%) cows that had lesions in the previous lactation and were also present on the farm in the current lactation had lesions in the current lactation. The highest risk for PDD occurred during the first month of lactation (9%). The yearly estimated cumulative incidence risk was 35% and the incidence density rate was 44.6 cases per 1000 cow-months. More animals were affected in summer and fall than in winter and spring. Purchased animals were 3.4 times more likely to be affected than animals born on the farm. Survival analyses indicated healthy cows conceived 93 days after calving (median), but affected cows conceived 113 days after calving (median) (P < 0.01). PDD-affected animals produced less milk than healthy cows, but the difference was not statistically significant in the multiple regression.

Mortality, morbidity, case-fatality, and culling rates for California dairy cattle as evaluated by the National Animal Health Monitoring system, 1986-87.

Abstract During 1986 and 1987, mortality, morbidity, case-fatality, and culling rates were estimated for endemic disease conditions in 43 randomly selected California dairy farms. Data were collected mainly by farmer interview. Age-specific mortality rates were: calves 22.8 per 1000 calf-months at risk; young stock 1.2 and cows 2.0 per 100 animal-years at risk. No bulls died during the observational period. For calves, diarrhea/enteritis and pneumonia had the highest incidence rates, 115.8 and 76.5 per 1000 calf-months at risk, respectively. Average incidence rates per 100 cow-years for the five most commonly reported cow diseases were: mastitis 30.3; infertility 7.9; metritis 7.0; footrot 5.5; retained placenta 4.7. The highest case-fatality rate was 32% for cows with traumatic reticulitis (hardware disease). About 25% of all cows were culled. Low production, infertility, and mastitis accounted for 87.6% of all culled cows. Characteristics of participating herds and diagnostic criteria are presented. Limitations of the data and of the collection methods are discussed.

SEROPREVALENCE OF TOXOPLASMA GONDII INFECTION IN SHEEP AND ALPACAS (LLAMA PACOS) IN CHILE

Serum samples from 408 sheep from different regions of Chile and 447 alpacas (Llama pacos) from the north of the country were tested for Toxoplasma gondii antibodies. The indirect haemagglutination test (IHAT) was used in both species and the indirect immunofluorescence test (IIFT) was also used on the sheep samples in order to compare the performance of the tests in that species. In both tests, titers > or = 1:16 were considered diagnostically significant. Sera from 49 sheep (12%) were positive to T. gondii antibodies by the IHAT. When using the IIFT, 114 sheep sera (28%) were positive. The different results obtained in sheep sera between the tests were significant (p < 0.0001). No differences were observed between geographical locations or sex of the sampled sheep regarding serological detection of T. gondii antibodies in sheep. As expected, adult sheep showed higher T. gondii reactivity than young sheep (p = 0.0008). The corrected prevalence of toxoplasmosis in alpaca was 16.3% (32 positive out of 447). The rather low prevalence in alpacas may be associated with their extensive management as well as the extreme climatic conditions of The Andes which apparently would not be favorable for the transmission of the parasite.

An Outbreak of Equine Neonatal Salmonellosis

An outbreak of salmonellosis in foals occurred on a large Thoroughbred farm in California. Only foals <8 days of age exhibited clinical signs, which included depression, anorexia, and diarrhea. Three foals died from septicemia. The agent responsible was Salmonella ohio, which is rarely involved in salmonellosis in horses. During the course of the outbreak, S. ohio was isolated from 27 of 97 mares (27.8%) and 34 of 97 foals (35.1%). Mares were the presumed source of infection for foals. The absence of clinical signs in mares allowed for increased exposure of foals through environmental contamination. Although foals continued to become infected after strict control measures were adopted, none became ill. Salmonella serotypes of seemingly low virulence can produce serious disease outbreaks.

Economics of disease occurrence and prevention on California dairy farms: A report and evaluation of data collected for the national animal health monitoring system, 1986–87

Sischo, W.M., Hird, D.W., Gardner, I.A., Utterback, W.W., Christiansen, K.H., Carpenter, T.E., Danaye-Elmi, C. and Heron, B.R., 1990. Economics of disease occurrence and prevention on California dairy farms: a report and evaluation of data collected for the National Animal Health Monitoring System, 1986-1987. Prey. Vet. Med., 8: 141-156. A stratified random sample of 43 dairy herds in California was studied for i year as a component of the National Animal Health Monitoring System (NAHMS). Costs associated with clinical disease and disease prevention were determined and the resulting costs extrapolated to the entire California dairy industry. Cost of disease for herds in our study was

Pasteurella multocida in Wild Mammals and Birds in California: Prevalence and Virulence for Turkeys

1.749 million (U.S. dollars), or

Homogeneity of characteristics of Pasteurella multocida isolated from turkeys and wildlife in California, 1985-88.

111.68 per cowyear; 52% of the cost was the result of culling of affected animals, and 24% was due to animal death. Calf disease represented 4% of the cost of all disease. Diarrhea and pneumonia were responsible for 86% of calf disease costs. Cow disease accounted for 92% of the total disease costs. Clinical mastitis and infertility accounted for 53% of cow disease costs. Cost of disease prevention for the 43 herds in our study was

Dairy Cattle Abortion in California: Evaluation of Diagnostic Laboratory Data

171 616, or

Differentiation of field isolates of Pasteurella multocida serotype 3,4 from live vaccine strain by genotypic characterization.

10.72 per cow-year. Most of the prevention cost was due to purchase of drugs and biologics. The estimated cost of clinical disease and disease prevention extrapolated to all California dairies was