Pathological lesions of lambs infected in utero with bovine viral diarrhoea virus type 1c (BVDV-1c).

BACKGROUND: Acute bovine viral diarrhoea virus (BVDV) infections in sheep are largely sub-clinical although infections of pregnant ewes have shown to result in significant fetal losses and persistently infected lambs. However, the extent and severity of abnormalities in lambs infected with BVDV in utero is still largely unknown. METHODS: Twenty-two ewes were experimentally infected with BVDV-1c between 59 and 69 days of gestation. Fifteen lambs were submitted for pathological examination and the abnormalities observed in lambs and fetuses characterised. RESULTS: Six lambs were identified as BVDV negative, and nine were identified as BVDV positive. Anasarca and cholestatic hepatopathy was observed in four BVDV positive lambs and associated with ewes with early seroconversion. One BVDV positive lamb was born with muscular tremors and a hairy coat associated with primary follicular dysplasia, a developmental abnormality normally associated with border disease infected lambs. CONCLUSION: If similar lambing outcomes are identified in a commercial setting then BVDV should be considered, particularly in areas where sheep regularly come in to contact with cattle. In addition, as far as the authors are aware, this is the first reported case of a 'hairy shaker' lamb born as a result of an infection with BVDV-1c in Australia.

Natural transmission of bovine viral diarrhoea virus-1c from a persistently infected neonate lamb to naïve sheep and cattle.

This study investigated the transmission of bovine viral diarrhoea virus (BVDV)-1c from a persistently infected (PI) neonate lamb to naïve sheep and cattle using three treatment groups: four naïve ewes and their five lambs, which were copaddocked with the PI lamb; five steers, which were housed in a paddock adjacent to the PI lamb; and five steers, which had direct but limited exposure to the PI lamb. Serum samples were collected and tested for BVDV-specific antibodies. Serum samples from the PI lamb, from day of birth to eight weeks of age, were tested for BVDV-specific antibodies and antigen and submitted for quantitative PCR to determine the viral load present at each week of age. Only one lamb from the copaddocked group developed BVDV-specific antibodies following comingling while all the steers in both the cattle treatment groups remained BVDV antibody negative. Quantitative PCR results from the PI lamb showed lower viral loads from day of birth to six weeks of age, compared with the results at seven and eight weeks of age. This may reflect maternal colostral BVDV antibody concentrations in the neonate lamb or other viral properties.

The diagnostic performance of an antibody enzyme-linked immunosorbent assay using serum and colostrum to determine the disease status of a Jersey dairy herd infected with Mycobacterium avium subspecies paratuberculosis.

Colostrum may have the ability to improve the diagnostic accuracy of some tests when compared to serum for important livestock diseases because of the high concentrations of immunoglobulins present within this sample type. The ELISA for Johne's disease is one such test, as it suffers from low sensitivity when testing serum samples collected during the subclinical stage of infection. Blood and colostrum samples were collected from 34 Jersey dairy cows and tested for antibodies against Mycobacterium avium subspecies paratuberculosis (MAP) by ELISA. Fecal samples were also collected and tested by a high-throughput Johne's polymerase chain reaction (HT-J PCR) assay and fecal culture (FC), with the latter being used as the reference test. A receiver operating characteristic (ROC) analysis was performed, and the area under the curve (AUC) was calculated. The HT-J PCR and FC results were also compared. Of the 34 cows in this study, 4 had FC results consistent with MAP infection. The HT-J PCR did not identify any FC-positive cows. Using a 1:20 dilution and sample-to-positive (S/P) ratio cutoff threshold of 0.15, the relative sensitivity values of both serum (AUC 0. 56) and colostrum (AUC 0.63) were 0%. With lower sample dilutions, the relative sensitivity values of serum were 0% (1:2, AUC 0.62; 1:5, AUC 0.55); however, the relative sensitivity value of colostrum was 75% (95% confidence interval [CI]: 19-99%) at a dilution of 1:5, S/P ratio cutoff threshold of 0.15, and AUC of 0.73 (95% CI: 0.55-0.87). The testing of colostrum samples for MAP-specific antibodies by ELISA may provide improved identification of animals in the early stages of infection with MAP when compared with serum samples.

Erysipelothrix rhusiopathiae and Mycoplasma hyopneumoniae: the sensitivities of enzyme-linked immunosorbent assays for detecting vaccinated sows of unknown disease status using serum and colostrum, and the correlation of the results for sow serum, colostrum, and piglet serum.

Due to relatively high concentrations of immunoglobulins, colostrum has the potential to improve the sensitivity of diagnostic tests for diseases in pigs when compared with serum. It is possible that colostrum could improve the sensitivity of the antibody enzyme-linked immunosorbent assay (ELISA) compared with serum. Colostrum is also essential for piglets, providing protection against infections in the first few weeks and months of life. The sensitivity of 2 commercially available ELISAs, one for the detection of Erysipelothrix rhusiopathiae and the second for Mycoplasma hyopneumoniae antibodies, when used with sow colostrum in comparison with serum was investigated. The correlation of maternal E. rhusiopathiae- and M. hyopneumoniae-specific antibody levels with specific-antibody serum levels in the piglet was also determined. The sensitivity was defined as the proportion of vaccinated sows that were correctly identified as vaccinated at a given cutoff point. The true disease status of the sows with regard to the 2 infections was unknown. Blood and colostrum samples were collected from 20 sows, 10 primiparous and 10 multiparous, and blood samples were also collected from the piglets of each sow, 48-72 hr post-farrowing. The sensitivities of both ELISAs were significantly improved when using colostrum compared with serum. Sow serum and colostrum optical density (OD) values were significantly correlated. The mean sow OD values for serum for E. rhusiopathiae and M. hyopneumoniae and colostrum for E. rhusiopathiae were significantly correlated with piglet serum OD levels. If the improved sensitivity of colostrum can be demonstrated in infected animals, this will increase the ability of the test to identify infected animals using both individual and pooled colostrum. Testing serum and/or colostrum using ELISA can be useful predictors of piglet disease-specific OD values.

Optimizing the Measurement of Colostrum Antibody Concentrations for Identifying BVDV Persistently Infected Calves.

Colostrum contains substantially higher concentrations of immunoglobulins compared to serum, which may help to improve the utility of diagnostic tests. The aim of this study was to determine the diagnostic value of colostrum antibody concentrations in identifying Bovine Viral Diarrhoea Virus (BVDV) PI (persistently infected) calf carrying beef heifers following an experimental infection. Colostrum was collected within 12 hours of parturition and tested in undiluted, 1:5, 1:10, 1:100, 1:200, and 1:500 dilutions using an enzyme-linked immunosorbent assay (ELISA) for BVDV antibody. Cows were determined to be carrying a PI calf based on positive quantitative Real Time-Polymerase Chain Reaction and antigen ELISA result on pre-colostral serum and ear notch samples collected from their calf. The median ELISA sample-to-positive (S/P) ratio for colostrum collected from heifers that carried a PI calf were significantly higher than the median ELISA S/P ratio for colostrum collected from heifers that did not carry a PI calf at dilutions of 1:100, 1:200, and 1:500. This study provides further evidence for increased antigenic stimulation in utero by the BVDV viraemic PI calf, which can also be identified with 100% diagnostic sensitivity when using 1:500 dilution colostrum.

Twinning in Holstein-Friesian Dairy Cows: Proportion Carried to Term and Calf Sex Ratios.

The purpose of this study was to investigate the proportion of twins carried to term and the sex ratio of twin calves at birth in Holstein-Friesian dairy cattle kept on commercial farms in Devon and Cornwall, England. Ten farms were used in the study. Fifty four cows with twin pregnancies were identified using trans-rectal ultra-sonographic examination between 30 and 70 days of gestation. The farm records were subsequently used to derive the number of calves born. Farm records of 66 additional sets of twin births with the sex of the calves recorded were also identified. Of the 54 cows diagnosed with twin pregnancies, 16 cows (29.6%) aborted or absorbed both fetuses, 11 cows (20.4%) carried one calf to term and 27 cows (50%) carried both calves to term. In the calf sex analysis of the additional 66 sets of twins: 13♂♂ calves (19.7%), 18 ♀♀ calves (27.3%) and 35 ♂♀ calves (53.0%). There was no statistically significant difference from an expected ratio of 1♂♂:2♂♀:1♀♀ (p = 0.61). This study provides bench marks for the expected abortion/absorption rates following the early ultra-sonographic diagnosis of twin pregnancies in comparable populations and supports earlier observations that the expected sex ratio for twinning approximates to1♂♂:2♂♀:1♀♀.

Bacterial Loads on Skin of Unclipped Gluteal Sites Following Treatment with 70% Isopropyl Alcohol-Soaked Swabs in Dairy Cows.

The aim of this study was to compare the bacterial load of unclipped gluteal skin in dairy cows following either no treatment or treatment with a standard 70% isopropyl alcohol-based skin treatment protocol. Twenty Holstein-Friesian dairy cows from a commercial dairy herd in Cambridgeshire, England, were used in this randomised, blinded, controlled study. On each of the experimental cows an area of unclipped gluteal skin on one side of the pelvis was treated with swabs soaked in 70% isopropyl alcohol-based using a standard protocol and a contra-lateral area of skin was left untreated as a control. All the experimental skin sites were sampled using a swab followed by bacterial culture and quantitative analysis of bacterial load. There was a statistically significant decrease in the bacterial colony forming units per mL for the isopropyl-alcohol treatment group when compared to the control group (p ≤ 0.01). There was a 58% reduction in the median bacterial load of the treated sites when compared to the bacterial load of the untreated sites. This study has demonstrated that the treatment protocol will reduce the skin bacterial load.

Comparison of serum, ear notches, and nasal and saliva swabs for Bovine viral diarrhea virus antigen detection in colostrum-fed persistently infected (PI) calves and non-PI calves.

The diagnosis of neonatal and young calves persistently infected (PI) with Bovine viral diarrhea virus (BVDV) by antigen-capture enzyme-linked immunosorbent assay (ACE) may be complicated by interference from colostrum-derived specific antibodies. Ten calves, with 3 calves identified as PI and 7 as non-PI were used in the current study. All non-PI calves were shown to be seropositive for BVDV-specific antibodies by antibody enzyme-linked immunosorbent assay (Ab-ELISA) on serum. Serum samples, ear notch samples, and nasal and saliva swabs were collected from each calf from birth until 12 weeks of age and tested by ELISA for BVDV-specific antigen and antibodies. Following colostrum ingestion, Ab-ELISA sample-to-positive (S/P) ratios rose by a mean of 0.95 (95% confidence interval [CI] = 0.64-1.25) and 1.72 (95% CI = 1.55-1.89) in seropositive, non-PI calves and in PI calves, respectively. The mean S/P ratios then declined to approximately 1.1 in non-PI calves and 0.5 in PI calves at between 60 and 80 days of age. In PI calves, testing for antigen in serum and nasal and saliva swabs was subject to interference by colostrum-derived antibodies in calves up to 3 weeks of age. Nasal swabs were less affected than serum and saliva swabs. Ear notches maintained positive ACE corrected optical densities at all sample times, despite a drop in the signal following the ingestion of colostrum.

Clinical reasoning and decision analysis.

Decision analysis enables outstanding information needs to be correctly identified and ensures that all the options are accurately represented so that appropriate decisions can be made. The aim of this article is to provide an introduction to the use of decision analysis in the practice of evidence-based veterinary medicine. Decision trees using utilities and economic outcomes are presented. The diagnostic process, including the critical appraisal of clinical decision support systems that may be used in this process, is described.