A retrospective study of respiratory disease in a cohort of bacon pigs. I. Clinico-epidemiological analyses.

Previous studies of respiratory disease problems in pig herds have to a large extent relied on mortality data and slaughterhouse findings. The present report deals with simultaneously recorded clinical data and post mortem information for individual pigs from a large herd. Among other things, the results suggest that the commonly applied treatments of clinical cases have limited effect, that routine meat inspection is a fairly sensitive tool in monitoring the disease status, that productivity is affected relatively more by clinical episodes than by subclinical occurrence, and that respiratory disease and diarrhea are interrelated in more than one way.

Congenital ataxia and tremor with cerebellar hypoplasia in piglets borne by sows treated with Neguvon vet. (metrifonate, trichlorfon) during pregnancy.

In 1976--77 The State Veterinary Serum Laboratory received new-born pigs which had shown nervous disorders immediately after birth. In all the cases the sows had been treated with Nevugon vet. (metrifonate, trichlorfon) during pregnancy. In the majority of the affected litters the morbidity and lethality were 100 per cent. Analysis of the breeding data from some of the herds suggested that the period during which the fetuses are sensitive is rather narrow, i.e., approximately from day 45 to day 63. The disease was reproduced experimentally and it was concluded that oral treatment of pregnant sows with Neguvon vet. about the middle of the gestation period can result in severe nervous disorders in the piglets. Clinically the disease is characterized by ataxia and tremor, and corresponding to that there is a pronounced hypoplasia of the cerebellum and also a reduction in the size of the spinal cord.

Pleuropneumonia in swine caused by Haemophilus parahaemolyticus. A study of the epidemiology of the infection.

Haemophilus parahaemolyticus infection was studied in a herd with continuous production, i.e., continuous introduction of stock to replace animals delivered for slaughter. None of 30 seronegative pigs contracted the infection when exposed to contact with two pigs that were seropositive after inoculation with H. Parahaemolyticus three weeks earlier. After aerosol infection had been applied in the building an acute outbreak with a morbidity rate of 100 per cent developed in less than 24 hours. Following recovery the majority of the 16 pigs present became seropositive, and when 30 seronegative pigs were introduced 7 weeks later, antibody response occurred in three of them. The persistence of H. parahaemolyticus in pigs that had been infected during the acute outbreak was confirmed at slaughter, in that the organism was re-isolated from the tonsils of 2 of these pigs. Most serum titres persisted for several months, but some animals showed just a transient antibody response.

Lung lesions at slaughter: associations to factors in the pig herd.

A survey was made of available data files to gain a preliminary insight into the association between environmental factors and the prevalence at slaughter of lung lesions. Herd size was the factor that showed the most predominant association with the prevalence of lung lesions. This was largely independent of the recruitment system for weanlings. There was a moderate trend toward positive association between the prevalence of lung lesions and the prevalence of other lesions. Lung lesions were weakly but significantly associated with the occurrence of infectious diarrhoea in the herd. The investigation demonstrated the feasibility of and the need for continuous epidemiological studies to identify disease determinants. Studies of the nature reported here makes it possible to define essential health factors with an accuracy that could never be achieved through clinical observations in a few herds.