Elimination of transmissible gastroenteritis virus from a pig farm by culling and serological surveillance.

The first and only outbreak of transmissible gastroenteritis in pigs in Ireland occurred in 1984 in a 650-sow unit which was one of three such units owned by one enterprise which supplied pigs to a 12,000 head fattening unit in the same ownership. The depopulation of the clinically infected unit and extensive serological monitoring of pigs in the other units and in pig farms throughout the country has proved successful in the elimination of transmissible gastroenteritis infections from pigs in Ireland.

Morbidity and mortality in a large Irish feedlot; microbiological and serological findings in cattle with acute respiratory disease.

A survey of morbidity and mortality was undertaken in a slatted unit containing 6399 beef cattle over a 6 month period. The mortality rate was 0.78% and the morbidity rate was 12.7%. The interval from arrival to morbidity was 25.5 days +/- 0.9. Significantly more sick cattle were identified on either Mondays or Tuesdays than were seen on Saturdays or Sundays (P < 0.005). The mean interval to mortality (all diseases) was 48.5 days +/- 7.4. Respiratory disease was the most frequently recorded disease and was responsible for 62% of morbidity and 58% of mortality. Samples from 133 cattle, taken as they presented with acute onset respiratory disease, contained antibodies to Bovine Herpes Virus -1(BHV-1) (14.3%), Bovine Viral Diarrhoea Virus (BVDV) (78%), Bovine Respiratory Syncytial Virus (BRSV) (94%) and Parainfluenza type 1 Virus (P13V) (99%). When the same cattle were resampled 4 to 6 weeks later antibodies were found for BHV-1 (93.2%), BVDV (99.2%), BRSV (100%) and P13V (100%). Eleven of 27 bronchoalveolar lavage samples taken from the above group of cattle exhibited positive fluorescence for BHV-1 but all 27 samples were negative for BVDV, BRSV and P13V. Pasteurella multocida was isolated from eight of the 27 lavage samples and Pasteurella haemolytica from one sample.

Role of fomites and flies in the transmission of bovine viral diarrhoea virus.

The role played by contaminated hypodermic needles and nose tongs in the spread of bovine viral diarrhoea virus was investigated by using a persistently viraemic animal as a virus donor. Susceptible cattle were infected by using contaminated needles and tongs and in some instances they in turn infected animals kept with them. Non-biting flies which fed on the ocular secretions of a persistently viraemic animal were also shown to be contaminated with the virus.

Incidence of sarcocysts in skeletal muscles of horses.

The incidence of sarcocysts was examined in postural, propulsive and respiratory muscles from 74 horses ranging in age from mid-gestation to 14 years post-natal. Cryostat sections were stained for myosin adenosine triphosphatase (ATPase) at pH 9.5 and the type of muscle fibre containing sarcocysts was identified. Sarcocysts were found in muscles from three animals, all aged 1 year or more. Counts showed that they displayed no preference for any particular muscle. However, fibres with a high activity for myosin ATPase were preferentially colonized. Transverse sectional profiles of sarcocysts showed a wide variation in size, shape and wall thickness. Both the proportion of horses infected and the intensity of infection per animal were considerably lower than those reported in other studies.

Structural and biochemical changes in a spinal myelinopathy in twelve English foxhounds and two harriers.

Degenerative lesions in the spinal cord white matter of 12 English Foxhounds and two Harriers between 3 and 6 years old were associated with a diet composed mainly of ruminant stomachs. Lesions were present throughout the length of the spinal cord and were more severe in ventral and lateral columns than in dorsal columns. Degenerate fibers were accompanied by astrocytic proliferation. Changes suggestive of a primary myelinopathy included vacuolated myelin sheaths around apparently intact axons and thick-thin transitions in myelin sheath thickness. Mixed sensory and motor peripheral nerves and muscle histochemical fiber type profiles appeared normal. Similarities were noted with the changes described in subacute combined degeneration of the spinal cord in human beings, a neuropathy caused by methionine and methylation deficiency in patients with vitamin B12 deficiency. Mean serum methionine levels were significantly lower (P greater than 0.01) and mean liver methionine synthetase levels were significantly greater (P greater than 0.01) in affected dogs restored to a balanced diet than in age-matched controls maintained on the balanced diet. The elevated methionine synthetase levels possibly reflected compensatory reactions to the associated dietary change.

Heart weight and running ability.

The weight of the heart as determined by dissection techniques was compared with liveweight and total muscle weight in different types of horses and dogs as adults and during growth. With increasing body size both within and between species, heart weight forms a lesser proportion of liveweight and of total muscle weight. Heart weight forms a greater proportion of liveweight in Thoroughbreds and Greyhounds (breeds noted for high speed running) than in other less fleet members of their species and Greyhounds have greater heart weights relative to total muscle weight than other dogs.

Potential blood supply to muscles in horses and dogs and its relation to athletic ability.

A modification of the histochemical reaction to demonstrate myosin adenosine triphosphatase activity in skeletal (striated) muscle was used to define the density of capillaries in transverse sections of 3 muscles (semitendinosus, diaphragm, and pectoralis transversus) of horses and dogs. Thoroughbred horses and Greyhound dogs, breeds noted for their speed in running, were compared with other members of their respective species. Thoroughbred cross horses were grouped with non-Thoroughbreds for comparison with Thoroughbreds. The area of muscle supplied by a capillary was remarkably similar in muscles of all groups of animals, except at early stages of growth. Adult Thoroughbreds had a greater capillary/fiber ratio in semitendinosus and pectoralis transversus than did other adult horses. Intermuscular differences in capillary/fiber ratio and the area per capillary within adults and young of each type of horse were negligible with one exception: the capillary/fiber ratio was less in the pectoralis transversus than in the semitendinosus of young non-Thoroughbreds. There was little between-type difference in capillary density in adult dog muscles, although the capillary/fiber ratio was greater in the semitendinosus of Greyhounds. Although the capillary/fiber ratio increases with growth, the area per capillary did not alter markedly. Cessation of training increased the area per capillary in the pectoralis transversus of Greyhounds, In all adult dogs, capillary/fiber ratios in the diaphragm were less than they were in the semitendinosus and the pectoralis transversus. In adult Greyhounds, this was compensated by a smaller area per capillary in the diaphragm. Seemingly, the ability for high speed running by the Thoroughbred and Greyhound was not associated with an enhanced potential blood supply to skeletal muscle.

Total fibre numbers in cross sections of the semitendinosus in athletic and non-athletic horses and dogs.

The numbers of fibres in the complete cross section of the semitendinosus were estimated in 58 equines and 59 canines of differing types. Animals selected for swiftness--thoroughbred horses and greyhounds--have a greater number of fibres in a cross section of their semitendinosus than other members of their species, whether as neonates or as adults. The numbers of fibres in the cross section increases during growth in both types of animal in each species.

Differences in the histochemical properties of skeletal muscles of different breeds of horses and dogs.

Histochemical profiles of individual muscle fibres were established using myosin adenosine triphosphatase (myosin ATPase), succinate dehydrogenase (SDHase), and glycogen phosphorylase (GPase) reactions in three muscles (semitendinosus, diaphragm, and pectoralis transversus) of the horse and dog. The major histochemical difference between fibres lies in their myosin ATPase activity; fibres can be subdivided into those with a high and those with a low activity. In horse muscle, all fibres have a high activity of GPase. In the diaphragm and pectoralis transversus, all fibres have a high SDHase activity, but fibres with a low activity of SDHase are also present in samples of the semitendinosus. In dog muscle, all fibres have a high SDHase activity; myosin ATPase low-reacting fibres also have a low activity of GPase. There is a greater fractional area of myosin ATPase high-reacting fibres in the pectoralis transversus and semitendinosus of thoroughbred horses and greyhounds (breeds selected for high speed running) and in the diaphragm of greyhounds. In adults this feature does not appear to be due to training, as are the differences in aerobic and anaerobic capacity (shown in other studies). The preponderance of myosin Atpase high-reacting fibres suggests that there may be differences in the nervous systems of athletes and non-athletes. It is concluded that the proportions of fibre types in muscles are related to the functions of muscles and of their parts. No sex differences or detraining effects were apparent, although the value for the proportion of fibre types (as differentiated by the myosin ATPase reaction) in the limb muscles of thoroughbred crosses lies between those of thoroughbreds and non-thoroughbreds.

The mean fibre area of the semitendinosus, diaphragm and pectoralis transversus muscles in differing types of horse and dog.

The mean fibre areas of samples from m. semitendinosus, m. diaphragma and m. pectoralis transversus of thoroughbred horses and greyhounds have been compared with those in similar samples from other members of their species. Athletes (greyhounds and thoroughbreds) have larger fibres in the semitendinosus and diaphragm than their fellows. However, the mean area of pectoralis transversus is similar in the two types of animal within each species. During growth the mean fibre areas increase to a greater extent in athletes than in non-athletes. Detraining adult greyhounds for a period of one year did not signficantly alter the fibre area; nor were any sex differences detected. Although the mean fibre area of corresponding muscles is significantly larger in horses than in dogs, the difference is proportionately less than that of their live weights.

The proportions of muscle, bone and fat in two different types of dog.

This study compares the proportions of muscle, bone and fat (obtained by gross dissection) in greyhounds--a breed selected for high speed running--and other dogs, both at maturity and during growth. In adults the proportion of muscle is significantly greater in the 'athletic' greyhound. The proportion of muscle decreases but not significantly with detraining. Adult greyhounds have less fat (even when detrained) than other dogs, but the skeleton provides a similar proportion of liveweight in both types of dog when adult. The greater growth rate of muscle in athletes explains the difference in adult proportions.