Caprine arthritis-encephalitis virus infection of goats in South Australia

Case Report: A Case of Caprine Arthritis Encephalitis in Dairy Goat Farms in South Korea

One Saanen dairy goat (Capra aegagrus hircus) farm in Korea reported that some goats showed clinical signs such as arthritis, paralysis, carpal joint swelling, and even death. We monitored clinical signs and pathological lesions. In the laboratory, we confirmed caprine arthritis encephalitis virus (CAEV) infection by polymerase chain reaction (PCR). We examined all the dairy goats on the farm and found that many of them were positive. In conclusion, CAEV infection was detected in the majority of the goats in this farm, and it induced severe clinical signs impacting productivity and causing important economic shortfalls. We need to regularly investigate all dairy goat farms, and, more importantly, inspection of the quarantine stage should be required before importation. Interestingly, we found all negative results in Korean native black goats (Capra hircus linnaeus).

Achievements of an eradication programme against caprine arthritis encephalitis virus in South Tyrol, Italy

Small ruminant lentivirus infections in goats affect both production and animal welfare. This represents a threat to the qualitative and quantitative growth of goat farming, recently observed in mountainous regions such as the Autonomous Province of Bolzano – South Tyrol (Italy). To monitor and eradicate the caprine arthritis encephalitis virus in this goat population, a compulsory eradication campaign was launched, based on a strict census of small ruminants and yearly serological testing of all animals, followed by the consequent culling of seropositive individuals. The campaign succeeded in completely eliminating cases of clinical disease in goats, while drastically reducing the seroprevalence at the herd as well as individual animal level. The serological outcome of the introduced control measures was determined using commercially available ELISA kits, demonstrating their suitability for use in this type of campaign, aimed at reducing seroprevalence as well as clinical manifestations of these infections. However, this clear success is diminished by the failure to achieve a complete eradication of these viruses. The reasons leading to the observed tailing phenomenon and the occurrence of new infections in already sanitised flocks are discussed and implementation of further measures are proposed.

Immunohistochemical detection of the p27 capsid protein of caprine arthritis-encephalitis virus (CAEV) in bone-marrow cells of seropositive goats

Bone-marrow samples were collected from 48 CAEV-seropositive, symptomless goats (30 kids, 18 adults). The samples were formalin-fixed and processed for histological examination. In addition, all samples were examined immunohistochemically with a monoclonal antibody (1A7) against the p27 capsid protein of maedi-visna virus, an antibody which cross-reacts with the Ca-p27 of CAEV. Samples from 16 goats (10/30 kids, 6/18 adults) showed positive immunolabelling of bone-marrow stromal cells (fibrocytes, endothelial cells and adipocytes) and of scattered macrophages, whereas haematopoietic cells were negative. The detection of viral Ca-p27 protein in bone-marrow fibrocytes was consistent with previous in-vitro studies which indicated that such cells are semi-permissive for CAEV infection. It is speculated that bone-marrow stromal cells represent a viral reservoir in symptomless animals.

Clearance of a productive lentivirus infection in calves experimentally inoculated with caprine arthritis-encephalitis virus

Lentiviruses have long been considered host-specific pathogens, but several recent observations demonstrated their capacity to conquer new hosts from different species, genera, and families. From these cross-species infections emerged new animal and human infectious diseases. The successful colonization and adaptation of a lentivirus to a nonnatural host depends on unspecific and specific host barriers. Some of those barriers exert a relative control of viral replication (i.e., cytotoxic T-lymphocyte response, viral inhibitory factors), but none of them was found able to totally clear the infection once the retrovirus is fully adapted in its host. In this study we examined the evolution of the host-lentivirus interactions occurring in an experimental animal model of cross-species infection in order to analyze the efficiency of those barriers in preventing the establishment of a persistent infection. Five newborn calves were inoculated with caprine arthritis-encephalitis virus (CAEV), and the evolution of infection was studied for more than 12 months. All the animals seroconverted in the first 0.75 to 1 month following the inoculation and remained seropositive for the remaining time of the experiment. Viral infection was productive during 4 months with isolation of replication competent virus from the blood cells and organs of the early euthanized animals. After 4 months of infection, neither replication-competent virus nor virus genome could be detected in blood cells or in the classical target organs, even after an experimental immunosuppression. No evidence of in vitro restriction of CAEV replication was observed in cells from tissues explanted from organs of these calves. These data provide the demonstration of a natural clearance of lentivirus infection following experimental inoculation of a nonnatural host, enabling perspectives of development of new potential vaccine strategies to fight against lentivirus infections.

Prevalence, spread and control of caprine arthritis-encephalitis virus in dairy goat herds in New South Wales

A study of the prevalence, spread and control of caprine arthritis-encephalitis virus (CAEV) in dairy goat herds in New South Wales (NSW) during 1986-1988 found that 56.8% of 1484 goats in 14 dairy herds were infected with CAEV. The prevalence of CAEV infection within most herds not implementing control measures increased during the study. At the end of the study, 59.7% of 1322 goats were infected. The prevalence of CAEV increased with age. Differences between breeds were less apparent. Within seven herds with a high standard of identification of goats, 149 of 812 goats seroconverted in an ELISA. Of these newly infected goats, 142 (95.3%) were > 1 yr of age and 96 (64.4%) were > 2 yr suggesting lateral spread of the virus. Most of the goats > 2 yr of age had been in the milking herd for a minimum of 3 to 6 months. The high seroconversion rate within the milking herd suggested that factors other than the ingestion of infected colostrum and milk before weaning were important for the spread of CAEV. Observations indicated that behaviour of goats, particularly reproductive behaviour among lactating does, and milking herd management practices are important in the spread of CAEV. A high density of livestock, poor livestock control and contamination of feed, water, equipment and personnel were implicated in transmission. Poorly functioning milking machines may also be involved. CAEV was eradicated from 3 herds by the implementation of strict control measures.

Effect of caprine arthritis-encephalitis virus infection on milk cell count and N-acetyl-beta-glucosaminidase activity in dairy goats

Bacteriology, somatic cell counts (SCC) and N-acetyl-beta-glucosaminidase (NAGase) activity determinations were conducted on milk samples collected from does in three dairy herds with caprine arthritis-encephalitis virus (CAEV) infection. In two herds, CAEV-infected does were more likely to have a subclinical bacterial infection of the udder than CAEV-free does (P < 0.05). Does with CAEV but no bacterial udder infection had significantly greater mean SCC and NAGase activity than CAEV-free does without udder infection (P < 0.01). In two herds, changes in milk SCC and NAGase associated with CAEV infection were similar to those produced by coagulase-negative staphylococcal infections. The findings confirm that indirect indicators of bacterial mastitis infection may have reduced specificity in dairy goat herds with CAEV.

Ovine progressive pneumonia, caprine arthritis-encephalitis, and related lentiviral diseases of sheep and goats

History and syndromes of pneumonia, encephalitis, arthritis, and mastitis are reviewed. Occurrence, etiology, pathogenesis, transmission, diagnosis, treatment, and prevention of these diseases are discussed.