M. D. Salman

The association of cattle husbandry practices, environmental factors and farmer characteristics with the occurence of chronic bovine tuberculosis in dairy herds in the Republic of Ireland

Abstract A matched case-control study was undertaken to provide information on the role of farm management practices, environmental factors and farmer characteristics in the epidemiology of bovine tuberculosis. Eighty dairy herds with chronic tuberculosis were compared with the same number of herds which had been free of the disease for many years. A standardized questionnaire was used to obtain information from the farmers. the study was conducted from August to October 1990, in Counties Cork and Kilkenny, Republic of Ireland. Factors which were identified as possibly contributing to recurrent outbreaks of tuberculosis outbreaks included nutritional factors, cattle purchases (especially bulls), the presence of badgers, and the spreading of slurry. Overall, the findings suggested that intensively managed dairy herds were at greater risk of bovine tuberculosis outbreaks than were other herds. The study did not support some of the hypotheses which traditionally have been put forward as contributing to tuberculosis outbreaks. These included contact with neigboring cattle owing to movements to and from fragments or poor boundary fencing, presence of sub-standard cattle housing, movement of equipment or vehicles onto farms, and exposure to water supplies from rivers or streams. In the light of these findings, and in view of the lack of evidence in the scientific literature to support these hypotheses, we suggest that a general re-evaluation of their role in chronic tuberculosis is needed.

Ordinary versus random-effects logistic regression for analyzing herd-level calf morbidity and mortality data

Abstract The analysis of data from populations organized into groups is frequently complicated by cluster (herd) effects. When present, clustering effects influence the probability of a health-related event in a way that is not readily accounted for with classical fixed-effects models (including unconditional logistic regression). Clustering introduces an additional source of (extra-binomial) variation into a logistic regression model, violating the independence and identical-distribution assumptions, and leading to biased variance estimators and spurious statistical significance. One remedy is to treat herd effects as random effects, so that variation even from unmeasured and unmeasurable (but clustered) sources can be accounted for. The logistic-normal regression model is introduced as one such random-effects model; its application is demonstrated using data from a previously described study of calfhood morbidity and mortality in 25 New York dairy herds.

Risk factors for L. monocytogenes contamination of dairy products in Switzerland, 1990–1999

Our purpose was to identify the main hazards associated with the spread of Listeria monocytogenes in dairy products in Switzerland and to determine the changes in predominant serotypes of the isolates, using databases on dairy-processing and environments from the Swiss Dairy Research Station during the years 1990-1999. Overall, of 76,271 samples collected, 3722 (4.9%) were positive for the presence of L. monocytogenes. Cheese-ripening facilities had the highest proportion of positive samples (7.6%), followed by small-scale local dairies (4.4%). By sample type, the highest proportion of positive samples (9.5%) was observed in water samples used for cheese-washing, followed by cheese-surface swabs (5.0%). During the 10-year period, no positive samples were obtained from cream, ice cream, milk powder, yogurt, or fresh cheese. Of 3722 L. monocytogenes isolates, 1328 (35.7%) were serologically typeable. Serotypes 1/2a, 1/2b, and 4b accounted for 92.7% of the 1328 isolates. Until 1995, the most-prevalent serotype was 1/2b (annual proportional prevalence 39.3-72.2%)--whereas since 1996, 1/2a was the most prevalent (34.7-54.7%). During 1996-1999, serotype 1/2a increased by 88%, compared to the average of 1990-1995. In the final random-effect multivariable logistic model, the strongest predictor of a positive culture was samples from cheese-ripening plant (OR=1.54; 95% CI: 1.14, 2.08) and the second-strongest predictor was samples collected by someone who was employed by the plant (OR=1.48; 1.29, 1.71). Hard and semi-hard cheeses were more likely to be associated with serotype 1/2b and soft cheeses with serotype 1/2a.

International trade, animal health and veterinary epidemiology: challenges and opportunities

The link between international trade, animal health and epidemiology has been recognized for a long time and has taken an additional importance in the aftermath of the Uruguay Round of Multilateral Trade Negotiations of the General Agreement on Tariffs and Trade (GATT) and of the inception of the World Trade Organization. The Agreement on the Application of Sanitary and Phytosanitary Measures of the World Trade Organization demands that sanitary and phytosanitary measures be scientifically based, placing epidemiology at the center of decisions related animal health and trade. This paper analyses the interactions between international trade of animals (and animal products) and epidemiology with discussion on the inputs of epidemiology in surveillance, risk analysis and regionalization.

Individual animal and maternal risk factors for morbidity and mortality of neonatal beef calves in Colorado, USA☆

Abstract A prospective study was conducted to quantify the individual animal and maternal factors that affected morbidity and mortality of calves in Colorado beef herds. The study subjects were all calves born in ten participating herds during the 1990 and 1991 calving seasons. All 3666 calves born during the study period were individually identified at birth, and subsequent disease events were recorded by the producers. The disease outcomes of interest and their observed incidence rates were: perinatal (birth to 12 h) mortality, 2.5%; general neonatal (12 h to 45 days) mortality, 2.2%; general neonatal morbidity, 4.4%; neonatal diarrhea, 1.1%; neonatal respiratory disease, 1.0%; mothering problems/weak calves, 1.2%; and neonatal enterotoxemia/sudden death, 1.4%. Data analysis utilized multiple logistic regression. All analyses were adjusted for herd. Perinatal mortalily was greater ( P P P =0.06). General neonatal mortality was higher ( P

Impact of transportation and lairage on hide contamination with Escherichia coli O157 in finished beef cattle.

Transportation of cattle from the feedlot to the slaughter plant could influence hide contamination of Escherichia coli O157. A study was initiated to investigate the influence of transportation and lairage on shedding and hide contamination of E. coli O157. Fecal and hide samples were obtained from 40 pens of harvest-ready beef cattle at the feedlot prior to transport and again at the slaughter plant immediately after slaughter. Potential risk factors for hide contamination at the feedlot, during transport, and at slaughter were evaluated. A multilevel Poisson regression model was used to evaluate if transportation and lairage were associated with hide contamination by E. coli O157 in finished beef cattle. Lots of cattle held in E. coli O157-positive lairage pens had eight times greater risk of having positive slaughter hide samples compared with cattle held in culture-negative pens (relative risk, 8.0; 95% confidence interval, 1.6 to 38.8). Lots of cattle that were held in lairage pens contaminated with feces had three times greater risk for positive slaughter hide samples compared with cattle held in clean pens (relative risk, 3.1; 95% confidence interval, 1.2 to 7.9). Lots of cattle that were transported for long distances (> 160.9 km) had twice the risk of having positive hide samples at slaughter compared with cattle transported a shorter distance (relative risk, 2.4; 95% confidence interval, 1.1 to 5.1). These findings suggest that transportation and lairage should be considered in E. coli O157 control strategies.

Development of a syndromic surveillance system for detection of disease among livestock entering an auction market

OBJECTIVE To develop a syndromic surveillance system based on visual inspection from outside the livestock pens that could be used for detection of disease among livestock entering an auction market. DESIGN Cross-sectional study. ANIMALS All livestock (beef and dairy cattle, sheep, goats, horses, and pigs) entering a single auction market in Colorado during 30 business days. Procedures-Livestock were enumerated and visually inspected for clinical signs of disease by a veterinarian outside the pens, and clinical signs that were observed were categorized into 12 disease syndromes. Frequency of clinical signs and disease syndromes was then calculated. RESULTS Data were recorded for a total of 29,371 animal observation days. For all species combined, the most common disease syndrome was respiratory tract disease (218.9 observations/10,000 animal observation days), followed by thin body condition and abnormal ambulation or posture (80.7 and 27.2 observations/10,000 animal observation days, respectively). Together, these 3 disease syndromes accounted for 92.8% of all clinical signs of disease observed. The syndromes least commonly identified were non-injury-related hemorrhage, death, and injury-related hemorrhage (0.0, 0.3, and 0.7 observations/10,000 animal observation days, respectively). CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that a syndromic surveillance system based on visual inspection alone could be developed to identify possible disease conditions among livestock at an auction market. Further studies are needed to determine the sensitivity and specificity of visual observation in detecting disease.

The influence of neonatal health on weaning weight of Colarado, USA beef calves

The effect of morbidity during early life on the weaning weight of calves in Colorado beef herds was investigated as part of a prospective longitudinal observational study. A total of 2609 calves born in nine participating herds during the 1990 and 1991 calving seasons were monitored for disease events and subsequently weighed at weaning as a measure of performance. Morbidity outcomes of interest and their observed incidence rates were: general neonatal (to 45 days) morbidity, 2.6%; neonatal diarrhea, 1.0%; neonatal respiratory disease, 1.0%; and mothering problems/weak calves, 0.4%. Mean calf weaning weight was 244±46 kg. Weaning weight data were adjusted by multiple regression for the effects of the herd, year, age of the calf, age of the dam, calf sex, frame size of the dam, and twin birth. General morbidity during the neonatal period resulted in a 15.9 kg reduction (P<0.01) in calf weaning weight. When morbidity was investigated as more specific disease conditions, calves that were classified as mothering problems/weak calves (i.e. calves that experienced maternal neglect, abandonment, or starvation, and weak calves) weighed 24.4 kg less (P<0.01) at weaning than did non-afflicted calves. Respiratory conditions and diarrhea during the neonatal period resulted in 16.5 kg (P<0.01) and 10.7 kg (P<0.05) reductions in weaning weight, respectively. Thus, disease occurrence during the early life of the calf had a detrimental effect on weaning weight.

Energy expenditure in dogs with lymphoma fed two specialized diets

Background. Cancer‐caused cachexia has been reported to be caused in part by an increase in energy expenditure, and diets with nutrient profiles containing 30–50% nonprotein calories as fat instead of carbohydrate may exacerbate this state of inefficient energy utilization.

Stochastic modelling as a tool for planning animal-health surveys and interpreting screening-test results

Traditionally, the planning of surveys (in particular, sample-size calculations) has relied on assumptions including the assumption of perfect screening tests. This paper presents a novel approach that can be used for planning animal-health surveys and interpreting screening-test results in the context of these surveys. A stochastic simulation model developed to assess the properties of herd-level sampling schemes and surveys has been adapted for large surveys aimed at substantiating freedom from infection at a national or regional level. We use a Bayesian approach to derive the post-survey probability of freedom from infection from the pre-survey probability of freedom and the likelihood ratio that is associated with screening-test results. We applied the model to two consecutive surveys conducted in 1998 and 1999 in Switzerland to substantiate freedom from infectious bovine rhinotracheitis (IBR) in the cattle population of about 56000 herds (median herd size of 15 cattle > 2 yr of age in 1999). In 1998, serum samples were taken from five cattle > 2 yr in 4672 herds, and in 1999 from all cattle > 2 yr old in 648 herds; samples were analysed by ELISA. The survey of 1999 provided less evidence than that of 1998 to support a status of freedom from infection; also, the characteristics of both herd-level sampling schemes were similar. We argue that the rationale for survey planning depends on the pre-survey probability of freedom from infection (i.e. our level of confidence that the infection does not occur in the targeted animal population). In consequence, surveys should be tailored to individual populations in the respective countries or regions. The model has been developed in an Excel spreadsheet to allow flexibility of use, and adaptation to many other animal-health issues.