Emerging Diseases and Welfare
Graham David at VLA Shrewsbury
Emerging Diseases and Welfare Programme Manager
The aim of the Emerging Disease and Welfare Programme is the supply of high quality information to Government and other customers on the disease status of farmed livestock, birds and wildlife in England and Wales.
VLA Bury
St Edmunds
VLA Regional Laboratories and Surveillance Centres continued to attract large numbers of diagnostic submissions from veterinary practices throughout England & Wales. Approximately 43,000 submissions were received in 2006, an increase on the previous year.
The harmonisation of epidemiological data between VLA & Scottish Agricultural Colleges Veterinary Services facilitated the production of a pilot cattle disease surveillance report for Great Britain. This is intended as a precursor to developing GB reports as a standard surveillance output covering all the important livestock species. Epidemiological tools, developed at VLA, which enhanced scanning disease surveillance data analysis, were used to produce a detailed report to assist Defra’s International Animal Health Division in successfully defending the Bluetongue free status of the UK.
The development and validation of a number of important diagnostic tests was achieved during the year including RTPCR for Influenza in pigs, BVD virus, PRRS virus, Leptospira and Chlamydophila spp. An ELISA assay for Fasciola hepatica antibodies in bulk milk, developed at Liverpool University and a Liver Fluke egg counting technique for bulked faeces samples developed by VLA Aberystwyth were also validated.
Cattle
An immunohistochemical study on a series of non-louping ill encephalomyelitis cases in ruminants was reported. No evidence of Borna disease virus, West Nile virus, rabies virus, bovine coronavirus, teschovirus or Bovine Herpes Viruses 1&5 was detected.
A second strain of BVDV type 2 was isolated from cases of abortion in a herd in Cumbria. Genetically it differed from the previous BVDV-2 strains detected in the UK and was most closely related to a group of BVDV-2 strains causing severe acute BVD in Canada and USA in the early 1990s.
A limited study of Bovine Lymphotropic Herpes Virus (BLHV) infection was undertaken involving 13 dairy herds with non-responsive post parturient endometritis. BLHV was detected in samples from at least one animal in nine of the 13 herds. Bovine Herpes Virus 4 was also detected in one of the BLHV positive herds.
Small Ruminants
Nematodirosis caused significant disease problems in lambs, which was likely to have been the result of the cold spring and a dry April, delaying the hatching of eggs. Nephrosis was also commonly diagnosed and in most cases dehydration associated with nematodirosis, cryptosporidiosis or coccidiosis, was thought to be a predisposing factor.
There were fewer incidents of caseous lymphadenitis, Johne’s disease and arthritis in lambs associated with Streptococcus dysgalactiae subsp. dysgalactiae compared with 2005. The number of incidents of lamb dysentery and pulpy kidney disease was also lower continuing the fall seen since 2003. Improved vaccine uptake may explain this.
Unusual conditions investigated included kangaroo gait affecting ewes on several farms, ulcerative vulvovaginitis and balanoposthitis, abomasal emptying defect affecting individual sheep, compressive cervical myelopathy (‘wobbler syndrome’) in Texel ewe lambs, neuroaxonal dystrophy in Swaledale lambs and ovine botulism.
VIDA incidents of nematodirosis in sheep (as a percentage of diagnosable submissions) 1999-2006
Red squirrel
(Sciurus vulgaris)
Wildlife
The concern regarding wildlife transmission of highly pathogenic strains of avian influenza virus (HPAI) such as H5N1 prompted a large increase in wildlife surveillance submissions. More than 9,000 birds from England, Wales and Scotland were examined. A single H5N1 isolate was made from a dead Whooper swan found in the sea near Fife, Scotland. All other influenza virus isolates were low pathogenic avian influenza strains. Surveillance of wild birds for West Nile Virus continued but no isolates were found from 300 birds examined. Continuing losses due to garden bird oesophagitis were recorded and incidents of pox were identified in red squirrels from many areas in the North of England.
Birds
Two further outbreaks of Fowl Typhoid (Salmonella Gallinarum) were confirmed in unrelated flocks. Mareks disease continued to cause losses in both vaccinated and unvaccinated birds, most of the diagnoses being made in small backyard or hobby flocks. There was a continued decline in the incidence of Necrotic Enteritis in conventional broilers and of Blackhead in turkeys. Newcastle disease, caused by Pigeon Paramyxovirus type 1 infection was diagnosed following the examination of four Grey partridge (Perdix perdix) carcasses.
Pigs
Porcine Late Onset Mortality Syndrome (PLOM) continues to be recognised by pig veterinarians in the field and appears to be a consequence of PCV2, PRRS, and Mycoplasma hyopneumoniae infection. The results of a small survey of affected herds indicated only 22% had PRRSv, 87% were positive for PCV2 and only 10% were positive for both viruses. There was a further fall in diagnoses of PMWS continuing the steady downward trend in diagnoses of PMWS after 2001. This may reflect increased familiarity with the disease amongst farmers and practitioners and consequently a reluctance to further investigate typical pigs. There were no indications of new influenza strains in pigs. The classical strains of H1N1 and H3N2 are now less common than the avian virus wholly adapted to pigs. VIDA incidents of nematodirosis in sheep (as a percentage of diagnosable submissions) 1999-2006
Alpaca
(Vicugna pacos)
Miscellaneous and Exotic Species
The growing population of New World Camelids in England & Wales was reflected in the 329 alpacas and 49 llama submissions received. A further outbreak of disease caused by BVD virus was confirmed following PCR tests on tissues from a stillborn alpaca cria. The dam had had contact with alpacas on a farm where BVD virus had been previously identified. The large numbers of movements of alpacas between units, often for breeding purposes are likely to predispose to further spread of infections. A disease resembling Type 2 ostertagiasis caused by Camelostrongylus spp. was diagnosed in an adult alpaca submitted for postmortem.
Blood samples ready for testing at VLA Starcross
Welfare
The programme continued to support the Animal Health, RSPCA and local Trading Standards departments in implementing animal welfare legislation by the provision of forensic pathology services. This resulted in 7 successful prosecutions during the year. Animal welfare advice was given as a part of 34 farm investigations and disease incidents were reported where adverse welfare impact related to lack of training and expertise, economic factors and new and emerging diseases.