The occurrence and distribution of maedi-visna virus infection in lower Austrian sheep breeding establishments

In a period of one year blood samples of 374 sheep of Lower Austrian flocks were examined in intervals of two months for antibodies against Maedi-Visna (MV). Further on specific attention was paid to the prevalence of MV-infection in the flocks. The antibody-titers were determined by means of agar gel-immunodiffusion test. In 5 (23.8%) of 21 flocks 45 (12.0%) of the sheep were seropositive. Seroprevalence varied within the examined breeds: 19 (27.1%) of 70 Karakul-sheep, 18 (28.1%) of 64 East-Friesian milk-sheep, 7 (9.4%) of 74 Merino sheep and 1 (0.9%) of 111 mountain sheep. None of 55 black-headed sheep showed MV seropositive reaction. Clinical symptoms of Maedi-disease were especially observed in milk-sheep and for the first time in Austria in Karakul-sheep. Unfavorable housing conditions (insufficient room, bad climatic conditions), breed specific behavior patterns (crowding of Karakul-sheep) and a high prevalence of MV infections promote a high incidence the disease.     

Incidence of indurative lymphocytic mastitis in a flock of sheep infected with maedi-visna virus

Sheep in a flock in which 88 per cent of the ewes had antibodies to maedi-visna virus were clinically examined for udder induration during lactation and after drying off. On both occasions about half of the ewes had indurated udders. Histological examination revealed lymphocytic mastitis associated with maedi-visna virus infection, in the udders of six of 25 hoggs (24 per cent), 21 of 39 shearlings (53.8 per cent) and 42 of 67 ewes (62.7 per cent). Distinct lung lesions were found in 8 per cent of the hoggs, 12.5 per cent of the shearlings and 10 per cent of the ewes. The results of a clinical examination of dry udders were correlated with the histological findings.     

The cost of Border disease infection in a commercial flock

The performance of a flock of 203 crossbred ewes on a lowland farm was examined. Before lambing the ewes were run in two groups (A and B). Group A (124 ewes) produced significantly fewer marketable lambs as a consequence of neonatal and later losses. The associated clinical features were consistent with Border disease infection and the presence of the virus was demonstrated. These features were not evident in the progeny of group B (79 ewes). The market sale returns of both groups of sheep were compared and the flock performance was contrasted with that of the two previous years. The outbreak of Border disease resulted in a potential reduction of income in excess of 20 per cent. Such a loss supports the necessity for an effective control strategy for Border disease.     

Pulmonary adenomatosis and maedi-visna in Ethiopian central highland sheep: a microscopic study

Microscopic examination of pneumonic lungs of the Ethiopian highland sheep (n = 35) was made and compared with the pneumonic lungs from ten sheep and 66 goats from the lowlands. Lesions compatible with sheep pulmonary adenomatosis (SPA; 8/35, 22.8%), and maedi-visna (MV; 9/35, 25.7%) were recorded only in sheep from the central highlands. Interstitial pneumonia (43.2%), bronchopneumonia (35.1%), and verminous pneumonia (6.3%) were recorded in both sheep and goats from the high- and the lowlands. SPA was documented for the first time in sheep from Ethiopia in this report. We believe that MV and SPA were introduced into Ethiopia through importation of exotic sheep. These infections should be considered in dealing with the diagnosis of respiratory diseases in all the sheep breeds in the central highlands and in the exotic and the crossbred sheep in the other parts of the country.     

Maedi-visna and sheep pulmonary adenomatosis: a study of concurrent infection

The transmission of maedi-visna (MV) virus was studied within two groups of sheep, one of which was also affected with sheep pulmonary adenomatosis (SPA). Serological monitoring of sheep kept in contact with both groups indicated that MV virus replication occurred to a greater extent in the group with both diseases, three of five in-contact sheep being seropositive after 1 year's exposure compared with none of six held with MV-virus-only infected lambs.     

The effects of maedi-visna virus infection on productivity in ewes

A total of five data sets obtained from four separate sheep flocks were used to evaluate the effects of subclinical maedi-visna virus infection (as determined by serological procedures) on productivity in ewes. In general, infection with maedi-visna virus had a detrimental effect on productivity. Infection resulted in a reduction in conception rates, with the odds of an infected ewe conceiving being only approximately 0.67 times those of a non-infected ewe. For ewes which did conceive, there was no detrimental effect of infection on the number of lambs born. The birth weights of lambs born to middle-aged (3–4 years) infected ewes were 3–6% lower than the weights of lambs born to non-infected ewes of the same age. There was very little apparent effect of infection in younger (1–2 years) and older (5 + years) ewes: some factors which may have biased these results are discussed. Lamb weights at 25–50 days of age appeared to be reduced by maedi-visna infection in the ewe but the results were not statistically significant.     

Transmissible gastroenteritis in endemically infected breeding herds of pigs in East Anglia, 1981-85

Endemic infection was a common sequel to primary outbreaks of transmissible gastroenteritis in large breeding herds of pigs in East Anglia. The main clinical features of the disease were diarrhoea affecting sucking piglets aged about six days or more, diarrhoea among recently weaned pigs and brief episodes of overt clinical recrudescence in part of the herd. Post mortem and bacteriological findings were often more suggestive of colibacillosis than transmissible gastroenteritis. In some herds, endemic infection remained clinically mild or inapparent for long periods. Evidence of endemic transmissible gastroenteritis infection was found in 43 (50.6 per cent) of 85 herds of pigs studied prospectively between 1981 and 1983. There was a significant correlation with herd size; the disease recurred during the 12 months after primary outbreaks in 36 (65.5 per cent) of 55 herds with over 100 sows compared with seven (23.3 per cent) of 30 herds with less than 100 sows (P less than 0.001). In the larger herds it occurred more commonly where finishers were kept (P less than 0.05). Sow morbidity and management factors during the primary outbreak had no statistically significant effect on the incidence of recrudescence. Epidemiological aspects of the findings are discussed with emphasis on the difficulties associated with the diagnosis and control of endemic transmissible gastroenteritis infection.     

Seroepidemiological survey of maedi-visna virus infection in sheep and goat flocks in Quebec.

Maedi-visna, a chronic viral disease of adult sheep characterized by progressive dyspnoea or neurological manifestations, was first recognized and described clinically in Canada in 1970. Seroepidemiological study was conducted in sheep and goats in various areas of Quebec. Sera of 10% of the animals of selected flocks were collected and specific antibodies against maedi-visna virus were tested by a modified direct complement fixation test. Results show seropositive rate of 67.6% for Sherbrooke sheep; of 40.5, 41.1 and 47.1% for Quebec, Saint-Hyacinthe and Nicolet sheep respectively and only 29.2 and 20.0% positive sera in l'Assomption and Rimouski animals. Prevalence rate of positive goats varied according to geographic areas (0 to 36.8%). Statistical analysis of various factors, e.g. age, breed, mode of raising, origin and size of flock showed no relation between these factors and the geographic areas. But, some clinical problems in the sheep flocks such as cough, rapid breathing, mortality and abortion were associated with high infection rate (greater than or equal to 50%) to maedi-visna virus. In goats, no correlation was demonstrated between these clinical signs and serological results. Our results suggest that it is important to consider this disease in an adequate program of preventive medicine in Quebec.     

Concurrent malignant catarrhal fever and bovine virus diarrhoea virus infection in a dairy herd

An account is given of an outbreak of malignant catarrhal fever which occurred in a 98-cow dairy herd. Ten animals died or were slaughtered and the disease was confirmed by clinical and histological examination. Serological tests for malignant catarrhal fever virus were positive in three of four animals. The diagnosis of malignant catarrhal fever was complicated by the presence of bovine virus diarrhoea virus infection in three of the early cases. The initial cases of malignant catarrhal fever occurred in a group of nine-month-old calves which were housed in an old milking parlour with 19 pedigree Suffolk ewes at lambing time. Later cases occurred in two adult cows and in two heifers. Investigations of the remainder of the herd for evidence of bovine virus diarrhoea virus did not reveal the presence of any persistently infected cattle. Serological examinations for antibody to malignant catarrhal fever and bovine virus diarrhoea virus were carried out on the 19 Suffolk ewes. Six of them had neutralising antibody titres to malignant catarrhal fever virus and three were positive in the indirect immunofluorescence test. The possible roles of bovine virus     

Haemangiomas, leiomyosarcoma and myeloma caused by subgroup J avian leukosis virus in a commercial layer flock

An outbreak of simultaneously occurring haemangiomas, leiomyosarcoma and myeloma was observed in a commercial layer flock in China. The sick chickens were extremely thin and dehydrated. Scattered haemangiomas were found on the claws, breast and wings. At necropsy, haemangiomas and some other nodular tumours were also found in the internal organs. In addition, diffuse enlargement of the liver and spleen appeared in some birds. Histopathologically, haemangiomas were typically cavernous haemangiomas and haemangioendothelioma. In the diffusely swollen liver and spleen, multifocal or widespread marrow tumour cells filled with ball-like acidophilic particles in cytosol were observed, which are the characteristic pathological changes of avian myelocytomatosis. The nodular tumour cells formed by muscle bundles were of variable size, irregular shape, poorly differentiated and malaligned. Immunohistochemistry for vimentin, cytokeratin, actin (smooth muscle) and actin (sarcomeric) and Masson's staining confirmed the different cell lineage of the nodular tumour, thus leading to the diagnosis of leiomyosarcoma. The seroprevalence of avian leukosis subgroup J (ALV-J) antibodies was 13.46% (7/52), while ALV-A/B and reticuloendotheliosis virus (REV) antibodies were not detectable. The DF-1 cells inoculated by virus extracted from liver samples from 24 infected chickens were cultured and the group-specific antigen (GSA) was identified by ELISA. All samples were positive for ALV, which was further identified as ALV-J by immunofluorescence assay (IFA). PCR analysis revealed that three isolates of ALV-J proviral sequence were close to the HPRS-103 prototype strain and other Chinese field strains isolated in recent years, while one isolate (DP01) had a lower homology with them. This is the first report that ALV-J infection caused the simultaneous occurrence of haemangiomas, leiomyosarcoma and myeloma in a commercial layer flock.     

The effect of a natural maedi-visna virus infection on the productivity of South African sheep

A cohort study was conducted in order to measure the effect of the chronic indurative lymphocytic mastitis caused by the South African strain of maedi visna virus (MVV) on the pre-weaning growth of lambs born either of naturally infected or uninfected ewes kept under similar conditions. Fifty naturally infected ewes as well as another 40 from a maedi-visna-free source to be used as control animals, were purchased and kept in separate flocks which were managed in a similar way. All the ewes were of the same breed and 3-4 years old. During the adaptation period, and through the mating, pregnancy and lactation periods they were periodically monitored for the presence of MVV serum antibodies. The lambs were weighed at birth and thereafter every 2 weeks until the age of 90 days, when they were weaned. The ewes were then slaughtered, and their udders examined histologically and the number of lymphocytic follicles were counted and assessed. Although the calculated values indicated a correlation between the number of follicles in the udder and the reduction in the growth rate of the lambs, this was not statistically significant. Similarly, despite higher counts of lymphoid follicles in the udders of sero-positive ewes as compared to those that were sero-negative and the lower ewe productivity indexes in infected ewes, no statistically significant differences were found in the indexes of ewes in different follicle categories.     

Nesting and floor laying by domestic hens in a commercial flock

1. The nesting behaviour of broiler breeders was studied in a commercial flock of nearly 4000 birds kept on deep litter by tagging a sample of 200 hens. Use of nest boxes by tagged birds was recorded on 52 d over 34 weeks.

2. Forty hens were never observed in nest boxes and 33 others were recorded only in ground‐level boxes. These 73 birds were recorded significantly less often in nest boxes and more often apparently laying on the floor than others. Fewer of them perched during observations and they started doing so later than birds which used raised nest boxes.

3. These results suggested that there were consistent floor layers, which had difficulty reaching raised nest boxes, as found previously in experimental conditions. Many or all floor layers may, however, have used ground‐level boxes sometimes.

4. Hens were inconsistent in their use of particular nest boxes, and some even nested in two distinct areas.

5. Most individuals were, however, consistent in their reaction to one or more features of the nest boxes, including height, aspect and area. Individual choices for these features varied, so no boxes were used particularly heavily, with the exception of those at ground level.