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Biomedical subjects

S H Done

Publications and source records attributed to S H Done.

At least 19 recordsLinked to original sources
PubMed1997

Neuropathology of scrapie: a study of the distribution patterns of brain lesions in 222 cases of natural scrapie in sheep, 1982-1991.

Detailed neuropathological findings in 222 cases of naturally occurring scrapie from Great Britain are described. The material consisted of formalin-fixed brain from eight breeds of sheep submitted between 1982 and 1991. Paraffin-embedded histological sections were made from several specified brain areas, including the medulla oblongata, cerebellum, pons, mesencephalon, diencephalon, septal area, basal ganglia and frontal cortex. Sections were examined by conventional and polarised light microscopy and the type and distribution of the lesions were recorded. Histologically, the lesions included vacuolation of neuronal perikarya and grey matter neuropil, neuronal degeneration (especially "dark' neurons) and loss, a reactive glial (predominantly astrocytic) response and amyloidosis. Vacuolar lesions were present in the cerebral cortex of 37 per cent of cases, centred around the superior frontal gyrus. Vacuolar lesions were detected in the neocortex for as long as sections have been taken from the superior frontal gyrus and are thus probably not a new feature of the disease. The distribution of vacuolation in the grey matter neuropil could be classified into seven patterns. Data from individual breeds of sheep showed that in some breeds there were significant differences in the age at which animals with different patterns of vacuolation died from scrapie.

Age Factors↗
PubMed1996

Porcine reproductive and respiratory syndrome (PRRS): a review, with emphasis on pathological, virological and diagnostic aspects.

Despite early attempts to control the spread of the disease, porcine reproductive and respiratory syndrome (PRRS) has now become endemic in many countries including Britain. The occurrence of subclinical herd infections, the prolonged circulation of virus within herds and probable aerogenic virus spread all mitigated against the success of control measures. The origin of the disease is unknown but the causative agent has been shown to be an arterivirus with shared features to lactate dehydrogenase virus of mice. There is evidence of extreme genetic and antigenic variability between American and European isolates. PRRS virus has a predilection for alveolar macrophages and does not grow in most cell lines. In infected pigs, viraemia can persist for many weeks in the face of circulating antibodies and little is known about the mechanisms by which immunity to infection develops. A wide spectrum of disease has been reported from the field, accompanied in some cases by heavy economic losses. Reproductive and perinatal losses were most prominent when the disease first appeared. In the endemic phase, PRRS may be more significant as a contributory factor to a post-weaning respiratory syndrome of young pigs of 3-8 weeks. On-farm techniques have been developed to reduce the recycling of PRRS virus from older infected nursery pigs to the younger newly weaned pig. Vaccines are now marketed for the control of PRRS, but are not licensed for use in Britain. Improvements in knowledge of virion composition and antigenic stability and in the nature of the immune response of the pig should result in genetically engineered subunit vaccines becoming available. Diagnosis of PRRS is still difficult as many animals do not show clinical signs and may only be detected by serology and often only when other respiratory diseases are being investigated. Now that the infection is widespread, serological testing must be properly targeted and interpreted to give meaningful results about virus circulation. An increasing arsenal of diagnostic methods are becoming available to detect virus in both fresh and fixed specimens. The pathogenic mechanisms of PRRS remain poorly defined and more work is needed to reveal the nature of the interaction between PRRS virus and other factors in disease.

Animals↗
PubMed1995

Porcine reproductive and respiratory syndrome: clinical disease, pathology and immunosuppression.

Porcine reproductive and respiratory syndrome (PRRS) was first known as blue-eared pig disease in the United Kingdom and the causative agent as 'Lelystad virus'. The disease is characterised by very variable clinical signs, including reproductive failure and respiratory disease. The respiratory syndrome is often associated with severe infection with secondary bacterial agents including Pasteurella multocida, Haemophilus parasuis and Streptococcus suis. However, some seropositive herds show no clinical signs of disease. The secondary infections may be facilitated by the destruction of circulating lymphocytes, by the destruction of the mucociliary clearance system and, most importantly, by a large reduction in the numbers of alveolar macrophages. The clinical syndrome observed in a herd may therefore depend in part upon the other diseases present.

Animals↗
PubMed1994

Thrombocytopenic purpura in lambs given bovine colostrum.

Newborn lambs which had been given colostrum from a single cow developed thrombocytopenia and seven died. The clinical signs included purpura, haemoglobinuria, melaena, dullness and lethargy. The lambs died at one to two days old. Post mortem examination revealed widespread haemorrhages throughout the body. Lambs given small amounts of colostrum developed a transient thrombocytopenia but did not die.

Animal Feed↗
PubMed1994

Effect of sequential porcine reproductive and respiratory syndrome and swine influenza on the growth and performance of finishing pigs.

Sows and gilts on a breeding and finishing unit seroconverted to porcine reproductive and respiratory syndrome (PRRS) virus between February and March 1992. The signs of the disease progressed through the breeding herd to the piglets, weaners, growers and finally the finishing pigs. Forty-eight finishing pigs, on a nutritional experiment in which the individual pigs' food intake was recorded daily, showed signs of PRRS and later of swine influenza virus infection. Blood samples collected at slaughter from 47 of the pigs were seropositive to PRRS virus but seronegative to swine influenza virus. However, an immunocytochemical examination of a representative sample of the lungs of the pigs showed that swine influenza virus was present, despite the negative serological results. The infection of the finishing pigs with PRRS virus was associated with recurrent periods of inappetence and a decline in growth rate and performance. The total financial loss from the sequential infection with the two viruses, in a herd without high health status, was estimated at approximately 7 pounds per pig.

Animals↗
PubMed1994

Congenital infection of pigs with ruminant-type pestiviruses.

Congenital infections of pigs were induced with two ruminant-type pestiviruses isolated from pigs. One of the viruses was bovine viral diarrhoea virus-like and the other border disease virus-like. Both produced symptoms similar to those observed with low virulence strains of classical swine fever virus. A striking effect of persistent virus infection in post-natal life was stunting in viraemic animals. It was also shown that a congenitally infected pig shed virus for 2.5 years and in sufficient quantity to infect other pigs, even by indirect contact. Unlike ruminants, congenitally infected pigs sometimes had persistent viraemia but eventually eliminated the virus. Clearance of virus from the blood was related to the appearance of neutralizing antibodies. However, clearance from the tissues sometimes took as much as 5 months longer than from the blood.

Animals↗
PubMed1993

Pathogenicity of a swine influenza H1N1 virus antigenically distinguishable from classical and European strains.

An H1N1 strain of influenza virus (A/swine/England/195852/92) isolated recently from clinical epizootics in pigs was transmitted experimentally to six-week-old specific pathogen-free pigs. Between one and four days after inoculation the infected pigs developed pyrexia and showed signs of coughing, sneezing and anorexia. Seroconversion was detected seven days after infection. Virus was isolated from nasal swabs and tissues up to four days after infection, but was not recovered from faeces. Virus was isolated from serum samples taken from each infected animal for a period of only one day between one and three days after infection. The pathology was characterised by a widespread interstitial pneumonia for up to 21 days after infection, lesions in the bronchi and bronchioles for up to seven days after infection, and haemorrhagic lymph nodes. Epithelial damage in the bronchial generations as a result of the virus infection was demonstrated by immunocytochemistry and electron microscopy.

Animals↗
PubMed1993

Aleutian disease in domestic ferrets: diagnostic findings and survey results.

Aleutian disease was diagnosed as the cause of posterior ataxia and paresis in domestic ferrets. Six serologically positive animals (four clinically affected and two unaffected) were investigated in detail and seven other clinically affected ferrets were also identified. The diagnostic findings included hypergammaglobulinaemia, histological lesions in the central nervous system and parvovirus-like particles in mesenteric lymph nodes. A wider serological survey of 446 animals owned by members of a ferret club revealed an incidence of 8.5 per cent seropositive animals.

Aleutian Mink Disease↗
PubMed1993

Scrapie associated fibril detection on decomposed and fixed ovine brain material.

Samples of cerebral cortex from eight scrapie affected sheep and two unaffected control sheep were stored for up to nine days at temperatures ranging from 18 degrees C to 29 degrees C. Scrapie associated fibrils (SAF) could be detected in proteinase K treated brain extracts from all the eight scrapie affected animals after five days storage and in six out of the eight after nine days storage. SAF could not be detected in any brain extracts from the two control animals. Formol saline fixed brain material from a further six scrapie affected and two clinically normal sheep, were also subjected to an extraction technique used to detect fibrils. No characteristic SAF were observed in any of these fixed samples. Long filamentous structures were observed in four of the fixed scrapie affected brain extracts and in one of the fixed unaffected control brain extracts.

Animals↗
PubMed1993

Observations on anatomical aspects of the ureterovesical junction of the pig.

The paper reports the anatomy of the ureterovesical junction in pigs without urinary tract disease and the changes that occur with ageing. In comparison with other mammals the pig has a long intravesical ureter. Its length increases with age, from a mean length of 5 mm. at birth to 36 mm. at maturity. The width of the ureteric orifice also increases with age. The ureteric orifice was horseshoe shaped in 96.5% of cases, the remaining orifices were stadium shaped. The delineation of the anatomy of the porcine UVJ is important in the study of porcine and human pyelonephritis as the pig urinary tract is widely used as a human model.

Animals↗
PubMed1992

Infection of pigs and cattle with bovine viral diarrhoea virus on a farm in England.

Deaths within a litter of sucking pigs led to a suspicion of hog cholera, but pestiviruses isolated from both dead and live piglets appeared to be bovine viral diarrhoea virus. Persistent viraemia with bovine viral diarrhoea virus was demonstrated in living littermates and also in a bought-in calf, housed in a nearby pen on the same farm. Only two of the littermates survived, both of which had been virus negative and seropositive from the outset of testing. Porcine and bovine virus isolates grew well in calf testicular cells and were neutralised equally by sera collected at the farm from cattle and pigs. However, a comparison by means of their reactivity to monoclonal antibodies showed that they were similar but not identical, and only the porcine isolates grew well in a porcine kidney cell line.

Animals↗
PubMed1992

Natural scrapie in goats: neuropathology.

The brains of the 20 goats affected with natural scrapie received at the Central Veterinary-Laboratory, Weybridge, since 1975 were examined microscopically. Lesions of a spongiform encephalopathy were found in the brainstem, cerebellum, diencephalon, corpus striatum, and also in the neopallium or cerebral cortex. The lesions in the neopallium have not previously been reported in natural scrapie in goats. Deposits of amyloid were present in the thalamus in three of the 20 goats.

Animals↗