Isolation of adenoviruses and reoviruses from avian species other than domestic fowl.

Adenoviruses and reoviruses were isolated from pigeons and mallard ducks. In addition, adenoviruses were isolated from budgerigars and a bantam and a reovirus was isolated from a turkey. Primary identification of these viruses was by electron-microscope examination. It was further possible to assign the 4 adenoviruses to recognized fowl serotypes, and the reoviruses shared a common antigen with fowl reoviruses. These viruses were isolated from a variety of clinical conditions.

Ultrastructural features of experimental parainfluenza type 3 virus pneumonia in calves.

Ultrastructural changes observed in the acute and repair stages of experimental P13 virus pneumonia in young calves are described. In the early acute stage of the pneumonia, paramyxovirus replication was observed within epithelial cells of the respiratory tract and within alveolar macrophages. There was loss of cilia and of ciliated cells in small bronchi and bronchioli. Proliferation of non-ciliated bronchiolar cells (Clara cells) produced zones of hyperplastic bronchiolar epithelium and, within alveoli, widespread proliferation of Type 2 pneumomonocytes led to alveolar epithelialization. Necrosis was noted in both bronchiolar and alveolar epithelium. Early evidence of repair was the appearance of macrophages on the surface of damaged bronchiolar and alveolar epithelium. Organization of bronchiolar exudate involving fibroblasts and macrophages was widespread in calves killed between 7 and 12 days after infection and, in calves killed at 12 days and subsequently, bronchiolitis obliterans was widespread. Re-epithelialization of damaged bronchiolar mucosa and alveoli also occurred.

Rapid diagnosis of Aujeszky's disease in pigs by immunofluorescence.

Direct immunofluorescence on impression smears of brain and pharynx was compared with virus isolation in cell culture for the diagnosis of Aujeszky's disease in experimentally and naturally infected pigs. Pharyngeal impression smears were more sensitive than virus isolation in two pigs killed 10 and 12 days after experimental infection. Both methods were of similar sensitivity in the detection of virus from field cases of disease. Smears of brain and pharynx were more sensitive than virus isolation for tissue which had been stored at room temperature (approximately 20 degrees C) for up to 48 hours. Some reduction in the amounts of virus recovered from tissues and the intensity of fluorescent staining occurred in these samples.

Mycobacterium bovis in the anterior respiratory tracts in the heads of tuberculin-reacting cattle.

Twenty-five of 50 randomly selected tuberculin-reacting cattle were confirmed as tuberculous in the laboratory. All 25 cattle had macroscopic lesions in lymph nodes associated with the respiratory tracts but only one had lung lesions. M bovis was isolated from the anterior respiratory tracts in the heads of four of the 25 tuberculous animals and from a nostril lesion found in a fifth. For at least three of these five animals, the intervals between the final tuberculin test and their previously negative tests indicated that infection had established relatively rapidly. Four of them had been tuberculin tested solely because they were animals in contiguous 'at risk' herds. It would appear that although M bovis can be isolated from the anterior respiratory tracts in the heads of tuberculin-reacting cattle, it is unlikely that primary foci of infection exist in regions other than the lungs or associated tissues. The study demonstrates the potential for reactors with lesions to excrete M bovis and the continued importance of infected cattle in the epidemiology and eradication of the disease.

Pulmonary lesions and Mycobacterium bovis excretion from the respiratory tract of tuberculin reacting cattle.

Although it is generally recognised that tuberculous lesions are present in lymph nodes associated with the respiratory tract in approximately 90 per cent of reactors with confirmed infection, lung lesions are found in only 1 to 2 per cent of such cases during abattoir examination. When lung lesions are not detected, it has been claimed that such cattle are non-excretors and thus unimportant in the epidemiology of the disease. In this study the lungs of 55 reactor cattle were sliced into sections approximately 0.5 cm thick. Tuberculous lesions were evident in over 70 per cent of lungs from reactors with concurrent lesions in lymph nodes of the respiratory system. Further, M bovis was isolated from single samples of nasal and, or, tracheal mucus taken at slaughter in 19 per cent of confirmed cases. Several of these reactors had a clear tuberculin test less than six months previously indicating recent infection. This study confirms the continued importance of the infected bovine in the epidemiology and current eradication of bovine tuberculosis. It is suggested that all tuberculous cattle with lesions in respiratory lymph nodes, rather than being regarded as non-excretors, should be considered as possible excretors and thus important sources of infection for other cattle both within and between herds.

Vaccination against Aujeszky's disease: field experiences.

Twelve herds were investigated where outbreaks of clinical Aujeszky's disease had occurred. Clinical Aujeszky's disease was eliminated from all farms following vaccination. After vaccination was stopped in two of the six fattening herds virus was also apparently eradicated, judging from serological examination. These two herds were the smallest of the six fattening farms and size and the throughput of pigs may have contributed to apparent eradication of virus. In two of six breeding farms where controlled vaccination is still practised unvaccinated gilts and boars were seronegative. In this case possible eradication of infection may have resulted from either no excretion or insufficient production of virus from vaccinates to infect susceptible non-vaccinates. It is postulated that a properly controlled and monitored vaccination and culling programme may result in the eradication of disease and perhaps also infection from breeding herds experiencing Aujeszky's disease.

Rain and windchill as factors in the occurrence of pneumonia in sheep.

A computerised information retrieval system of abattoir pathology and meteorological data has been used to investigate the effect of prevailing weather conditions on the occurrence of pleurisy and pneumonia in the sheep population of Northern Ireland. Significant correlation coefficients were found between the percentage condemnations due to pleurisy and pneumonia in sheep and rainfall, windspeed, temperature and humidity. The most significant correlation was found with windspeed. The paper describes the calculation of a new meteorological variable, the rain/windchill factor. Very highly significant correlation coefficients were found between the percentage lung condemnations in sheep and the rain/windchill factor prevailing during the same month and both one and two months previously. The paper discusses the practical implications of these findings for sheep production and highlights the desirability of protecting sheep from adverse climatic conditions during the winter months.

Transmission of tuberculosis from experimentally infected cattle to in-contact calves.

Five of a group of six calves were inoculated with Mycobacterium bovis. Two more uninoculated calves were introduced to the group 84 days later. All the inoculated calves were subsequently shown to be excreting M bovis in nasal mucus. The uninoculated calf in the initial group of six became infected and subsequently excreted M bovis. The two uninoculated calves which were introduced later did not become infected. It was concluded that contact with nasal mucus from the infected cattle resulted in infection of the uninoculated calf and that the density of accommodation of animals excreting M bovis was an important factor in transmission of the disease.

Control, prevention and eradication of Salmonella enteritidis infection in broiler and broiler breeder flocks.

Salmonella enteritidis was identified by serological and bacteriological techniques in two clinically normal breeder flocks in an integrated broiler organisation in Northern Ireland. The organism was transmitted vertically to clinically affected progeny flocks. The infected breeder flocks were slaughtered and the infection throughout the organisation controlled and subsequently eradicated. A working group, consisting of the senior management of the broiler organisation and veterinary staff from the Veterinary Research Laboratories at Stormont, was formed to establish procedures to minimise the risk of the reintroduction of salmonella infection, by preventing vertical transmission from grandparent flocks, or lateral transmission from personnel, other animal species and fomites, or transmission through the feed. All feed was heated to a minimum of 70 degrees C for 12 minutes immediately before it was pelleted and subsequently transported to the flocks through a dedicated system of conveyor belts, bins and lorries. A comprehensive system for monitoring the efficacy of the preventive procedures was established and is now used throughout the poultry industry of Northern Ireland.

Excretion of Mycobacterium bovis by experimentally infected cattle.

Three groups, each of five calves, four to seven months old, were inoculated intranasally with different numbers of Mycobacterium bovis. Infection was established readily in the calves which received an inoculum containing either 10(6) or 10(4) colony forming units (cfu). After every infection there was a lag period during which the organisms could not be isolated from specimens of nasal mucus. All the animals excreted M bovis and the time of commencement, quantity and duration of excretion appeared to be related to the inoculation dose. Excretion continued for many weeks, and for two calves excretion became intermittent over many months. All the calves which were given inocula of 92 cfu failed to develop the disease and no immunological responses were detected; however, M bovis was isolated from nasal secretions from one of these animals 100 days after inoculation.

Experimental reproduction of the egg drop syndrome 1976 with a haemagglutinating adenovirus.

The experimental reproduction of an egg drop syndrome is described. Experimental oral infection of fowl with a haemagglutinating adenovirus resulted in the production of shell-less, soft-shelled and thin-shelled eggs in association with loss of egg shell colour and were similar to those changes seen in the egg drop syndrome 1976 (EDS 76). The first changes observed were 7 days post-inoculation when loss of egg shell pigmentation occurred. Colour patterns did not return to normal until 25 days post-inoculation. Thinning of egg shells was first seen 1 day after the loss of pigmentation and by 9 days post-inoculation soft-shelled and shell-less eggs were laid. From 13-16 days post-inoculation between 25 and 40% of eggs laid were either shell-less, soft-shelled or very thin-shelled. The majority of birds were laying normal eggs by 24 days post-inoculation. In spite of the marked egg shell changes the overall daily egg production remained at approximately 80% during the 17-week experimental period.

Experimental infection of chickens with rotaviruses: clinical and virological findings.

Specific-pathogen-free chickens were infected orally with two different isolates (Ch 1 and 132) of chicken rotavirus. Chickens aged 1, 14 and 28 days were equally susceptible to infection. Following infection with either virus, the clinical signs were mild. Coincident with the peak of virus excretion and for a period of 1 to 2 days, infected birds passed increased quantities of caecal droppings. At necropsy, the caeca were abnormally distended with gas and fluid. Immunofluorescence showed that for both viruses the principal site of replication was the mature villous epithelial cell of the small intestine. However, Ch 1 rotavirus grew best in the duodenum while 132 virus favoured the jejunum and ileum. Ch 1 rotavirus and 132 virus were detected by direct electron microscopy in the faeces from 2 to 5 days and 1 to 7 days respectively after infection.