Monitoring the bulk milk antibody response to BVDV: the effects of vaccination and herd infection status.

Bovine Viral Diarrhoea Virus (BVDV) is a pestivirus in the flaviviridae family which affects cattle worldwide. Bulk milk (BM) antibody testing is frequently used as a relatively quick method of assessing herd BVDV exposure; however, an understanding of the effects of vaccination and historic infection is essential for test interpretation. This study investigated the trends exhibited by monthly BM antibody analysis in 14 herds split into three categories. Category 1 herds (vaccinating/no persistently infected (PI) animals) began the study with mid-positive BM antibody titres and experienced an estimated increase of 0.007 optical density (OD) units per month (equating to a rise of 0.35 OD units in 50 months). Category 2 herds (not vaccinating/no PI animals) began the study with mid-positive BM antibody titres and experienced an estimated decrease of 0.005 OD units per month with antibody levels in one category 2 herd taking 1290 days to decrease from mid-positive to negative. Category 3 herds (vaccinating/PI animals present) began the study with high BM antibody titres which plateaued within this range throughout the 50-month observation period. Vaccination was observed to cause transient increases in BM antibody in a number of herds in categories 1 and 3.

Controlling tuberculosis in a llama (Lama glama) herd using clinical signs, tuberculin skin testing and serology.

An outbreak of tuberculosis (TB), caused by Mycobacterium bovis, was investigated in a small herd of llamas (Lama glama). Based on three ante-mortem diagnostic methods (clinical signs, tuberculin skin test reactions, and 'Rapid Test' serology), 12 llamas were selected for examination post-mortem. Grossly visible lesions suspicious of TB were observed in eight animals, four of which had exhibited clinical signs, one was a skin test 'reactor', and three had been seropositive. M. bovis was isolated from seven of these eight animals. Clinical signs combined with serology were found to be useful in identifying infected animals, but tuberculin skin testing had limited negative predictive value as four llamas that were subsequently confirmed as infected were not detected using this assay.

Congenital tremor and hypomyelination associated with bovine viral diarrhoea virus in 23 British cattle herds.

This paper presents data from 23 British herds investigated between 1991 and 2007 where neurological disease in calves was caused by bovine viral diarrhoea virus (BVDV) infection. A variety of clinical signs, most commonly tremor or trembling, were apparent in the calves from birth, and most were recumbent or unable to stand unsupported. Severe diffuse neuraxial hypomyelination was present in all of the calves, and immunohistochemistry revealed cerebral neuronal labelling consistent with congenital persistent pestivirus infection in each brain. BVDV was detected in peripheral blood samples from eight of 15 calves tested using an antigen ELISA, and was isolated in culture from samples of viscera, brain or blood collected from 17 of 24 affected calves. TaqMan RT-PCR for pestivirus RNA was positive for BVDV-1 in all six calves tested. Six of the virus isolates on which molecular classification was carried out, obtained from calves in four of the herds, were identified as BVDV-1a, while three isolates from one affected and two unaffected calves on a fifth farm were confirmed as BVDV-1b.

Prevalence of faecal excretion of verocytotoxigenic Escherichia coli O157 in cattle in England and Wales.

During the decade to 1999, the incidence of human infections with the zoonotic pathogen verocytotoxin-producing Escherichia coli O157 (VTEC O157) increased in England and Wales. This paper describes the results of a survey of 75 farms to determine the prevalence of faecal excretion of VTEC O157 by cattle, its primary reservoir host, in England and Wales. Faecal samples were collected from 4663 cattle between June and December 1999. The prevalence of excretion by individual cattle was 4.2 per cent (95 per cent confidence interval [CI] 2.0 to 6.4) and 10.3 per cent (95 per cent CI 5.8 to 14.8) among animals in infected herds. The within-herd prevalence on positive farms ranged from 1.1 to 51.4 per cent. At least one positive animal was identified on 29 (38.7 per cent; 95 per cent CI 28.1 to 50.4) of the farms, including dairy, suckler and fattening herds. The prevalence of excretion was least in the calves under two months of age, peaked in the calves aged between two and six months and declined thereafter. The phage types identified most widely were 4, 34 and 2, which were each found on six of the 29 positive farms.

Prevalence of antibodies to bovine virus diarrhoea virus and other viruses in bulk tank milk in England and Wales.

Bulk tank milk samples from 1070 dairy herds in England and Wales were tested by ELISA for antibodies to bovine virus diarrhoea virus (BVDV). A subset of 341 herds was tested by ELISA for antibodies to bovine herpesvirus 1 (BHV-1), bovine respiratory syncytial virus (BRSV) and bovine coronavirus (BCV). None of the herds had less than 40 dairy cows and none had been vaccinated against BVDV. The prevalence of BVDV antibody-positive herds in the national population was estimated at 95 per cent and approximately 65 per cent of the herds had a high level of bulk tank antibody suggestive of recent infection with BVDV. Dairy herds in East Anglia and the south-east of England had a significantly lower risk of being BVDV antibody-positive than herds in the rest of England and Wales. However, these regional differences tended to diminish with increasing herd size. Around 69 per cent of the herds were BHV-1 antibody-positive and all the herds were antibody positive to BRSV and BCV. Comparison with earlier serological surveys revealed that there had been little change in the prevalence and distribution of BVDV antibody-positive herds in England and Wales over the last 20 years, but that there had been an increase in the prevalence of BHV-1 antibody-positive herds.

An inherited congenital goitre in pigs.

A diagnosis of congenital goitre was confirmed histologically in piglets which were born hairless and swollen, and with significantly enlarged thyroid glands. The iodine content of the thyroid glands and the serum total thyroxine concentrations were very low. No evidence was found of iodine deficiency or significant goitrogenic activity in the diet fed to the sows. An investigation of the parentage of six affected litters revealed that they all had one or other of two boars as the sire, grandsire or great grandsire. The suspicion of an inherited disorder was confirmed when a test mating of a suspect carrier boar and sow resulted in the birth of two affected piglets. The ratio of the numbers of affected and unaffected piglets was statistically consistent with an autosomal recessive mode of inheritance.