Cattle
Enhanced surveillance for bovine viral diarrhoea (BVD) Type 2 virus was introduced during the year as the virus was isolated for the first time in Great Britain in a nine month old Holstein bull calf imported from North America as an embryo. Examination of contemporaries from this herd and animals derived from related embryos have to date revealed one further animal persistently infected with the virus, which has been removed from the herd. Further investigations are continuing to identify the most likely mechanism of introduction and to enable safeguards to be increased to prevent any similar occurrences. A research project looking at methods to improve the control of BVD has demonstrated that the RT-PCR technique is superior to the current diagnostic techniques in identifying persistent infection in young calves.

Visiting a farm to discuss sheep health problems

Examination of oocysts from clinical cases of coccidiosis throughout the year has revealed three main species Eimeria bovis, E.zuerni and E.alabamensis, with the latter establishing itself as an important pathogen affecting older calves.

Liver fluke infection has continued to cause losses in cattle. Analysis of epidemiological data gained from samples submitted by private veterinary surgeons has indicated that diarrhoea was the most common principal presenting sign. The condition was reported in most areas of the country including some where the disease was hitherto unknown. A small epidemiological survey of herds in East Anglia, carried out in partnership with Merial Animal Health, revealed that 19% of the beef and 25% of the dairy herds tested were infected.

Sheep
A milking flock of 150 ewes showed respiratory problems and a 50% fall in milk yield. Examination of nasal swabs confirmed Mycoplasma ovipneumoniae as the cause.

Liver fluke continued to cause losses in sheep as well as cattle. Numerous clinical signs were associated with the condition, but acute and subacute infections were seen over an extended period suggesting that the seasonality of the different forms of the disease may be changing. Parasitic gastro-enteritis also continued to cause losses with disease being observed in to the winter months. Anthelmintic resistance to benzimidazoles and levamisole was demonstrated in some affected flocks.

Chorioptes bovis was identified as the cause of skin disease in a West Country flock and the louse Bovicola ovis was commonly identified as a cause of pruritus and fleece loss. However, sheep scab remained the most common skin disease.

Pigs
Streptococcus suis serotype 25 was identified for the first time in England but post-weaning multisystemic wasting syndrome (PMWS) continued to be the single most important disease syndrome reported. It is now recognised in all parts of the UK and is responsible for significant post-weaning losses. Pneumonia was frequently reported as a symptom of the condition and co-infection with a number of pathogens including Pasteurella multocida, Actinobacillus pleuropneumoniae, Mycoplasma hyopneumoniae and hyorhinis, Streptococcus suis serotypes 2 and 3 and porcine reproductive and respiratory syndrome (PRRS) virus.
A research project to investigate the role of modulation of the immune system in the pathogenesis of the condition is progressing and a comparison of the immunological events occurring in affected and unaffected pigs is being monitored.

Birds
Dysbacteriosis in broilers (the current term used for the syndrome characterised by wet litter) has been prevalent which, together with an increase in necrotic enteritis and cholangiohepatitis, has been linked by some to a decline in the use of antimicrobial growth promoters. However, it is likely that various other factors, including nutrition, are also involved.
Vertebral osteomyelitis continues to be clinically recognised in young broilers by lameness and paresis. Lesions are also found in the fourth thoracic vertebra from which Enterococcus caecorum can be isolated.

Wildlife
Surveillance of wild birds was increased during the year to improve the UK coverage for West Nile Fever (WNF).
Specimens representing 61 different species were submitted but no WNF virus has been identified. Other significant findings from necropsy of these specimens have included botulism, tritrichomoniasis, salmonellosis and avian paramyxovirus 1 (pigeon).

Exotic Species
The number of South American Camelids, especially alpacas (approximately 10,000 kept in the UK) continues to increase and cases of interest included vitamin D deficiency in cria born late in the season, Johne’s disease and fasciolosis.