Selected highlights from other veterinary journals
Association between genotype and scrapie in goats in the UK
W. Goldmann, K. Ryan, P. Stewart, D. Parnham, R. Xicohtencati, N. Fernandez, G. Saunders, O. Windl, L. González, A. Bossers, J. Foster
ALTHOUGH the goat population in the UK is small compared with other European countries, there is a need for information on the susceptibility of goats to transmissible spongiform encephalopathies. This study investigated the genetics of scrapie susceptibility in goats.
Blood samples were collected from over 1100 goats on 22 holdings, representing all eight common breeds in the UK (a large proportion of animals were crossbreeds). DNA was extracted and subjected to PCR and sequencing to determine allele and genotype frequencies. Tissue samples from 150 scrapie-affected goats were collected over a period of approximately three years following passive (clinical cases) and active (fallen stock or research activity) surveillance. Scrapie was confirmed by the presence of PrPd (the disease-specific prion protein). To compare the results with those from goats of European descent but from a country officially free of scrapie, 166 Criollas goats from different areas of central Mexico were genotyped.
Eleven Prnp alleles (encoding the normal prion protein, PrPC) were found in over 30 genotypes. The study confirmed the association between the allele encoding Met142 and increased resistance to preclinical and clinical scrapie. It also revealed a novel association between the allele encoding Ser127 and a reduced probability of goats already positive for the accumulation of PrPd in the brain or periphery developing clinical signs. The allele encoding Met142 had a high overall frequency of 22.6 per cent, while the frequency of the allele encoding Ser127 was considerably lower at 6.4 per cent. In contrast, a well-known resistance associated allele encoding Lys222 was found to be rare (0.9 per cent). Nine Prnp alleles were found in Criollas goats, including a novel Phe to Leu substitution at codon 201, confirming that high genetic variability can be found in scrapie-free populations.
On the basis of their findings, the authors suggest that it should be feasible to lower scrapie prevalence in goat herds in the UK by genetic selection.
Syringomyelia in Cavalier King Charles spaniels
S. Loderstedt, L. Benigni, K. Chandler, J. M. Cardwell, C. Rusbridge, C. R. Lamb, H. A. Volk
THIS study aimed to define the anatomical distribution of syringomyelia in Cavalier King Charles spaniels clinically affected by the Chiari-like malformation and syringomyelia disease complex.
Forty-nine Cavalier King Charles spaniels (median age five years, range 1.2 to 10.8 years) were included in the study. To be included, dogs had to be showing clinical signs consistent with Chiari-like malformation and syringomyelia, such as neurological deficits, spinal hyperaesthesia on palpation, and phantom scratching. Dogs were placed in dorsal recumbency, and MRI of the entire spinal cord and brain was performed. The maximum dorsoventral syrinx size (≥2 mm) was measured over each vertebral body perpendicular to the longitudinal axis of the spinal cord. This and a number of other morphological parameters were determined and compared.
Syrinx formation was present in the C1-C4 region and in other parts of the spinal cord. The maximum dorsoventral syrinx size could occur in any region of the spinal cord, and the total syrinx size was found to be positively correlated with age. Seventy-six per cent of dogs with a cranial cervical syrinx also had a syrinx affecting more caudal spinal cord regions.
The authors conclude there is a high potential for Cavalier King Charles spaniels with clinical signs of Chiari-like malformation and syringomyelia to develop syringomyelia in more than one spinal cord region. They note that diagnostic imaging limited to the cervical spine in clinically affected dogs is likely to underestimate the degree and severity of syringomyelia, and hypothesise that syringomyelia has a progressive nature, which requires further characterisation.
Emergence of Culicoides species from indoor and outdoor breeding sites
C. Ninio, D. Augot, B. Dufour, J. Depaquit
Culicoides obsoletus is thought to be the main vector of bluetongue virus (BTV) in northern Europe, but little information is available about the species' breeding sites. This study examined the emergence of C obsoletus from soil samples collected on two farms in north-east France.
The initial farm studied (farm A) kept cattle and sheep, and was one of the first holdings to be affected by BTV type 8 at the end of August 2006. The second (farm B) kept cattle, and was located 16 km away from farm A. Soil samples, collected between August and September 2010, were obtained from both indoor and outdoor environments. Indoor samples were taken from old litter in the corners of dairy cow housing, while outdoor samples came from the bottom of cattle manure heaps left in pastures. Samples were stored in individual netted buckets at 22°C in the laboratory; tap water was added regularly to keep samples humid but not waterlogged. The volume of each sample was calculated. Emerging Culicoides were collected two to three times a week, over 11 weeks, and examined microscopically for identification according to morphological characteristics.
A total of 1924 adult Culicoides, together with other Diptera, were collected from the samples. All Culicoides were identified as C obsoletus. The ratio of females to males was 1.06. On farm A, 1584 C obsoletus emerged from indoor samples and 211 C obsoletus from outdoor samples. On farm B, the number of C obsoletus was significantly lower, particularly in indoor samples. Emergence of C obsoletus began one to four days after sample collection and lasted for more than two months, peaking between September 24 and October 8.
The authors discuss the possible impact of farming practices on the number of C obsoletus collected on each holding, and the differences in numbers between indoor and outdoor samples.
- British Veterinary Association