Congenital bovine epizootic arthrogryposis and hydranencephaly in Australia. Distribution of antibodies to Akabane virus in Australian Cattle after the 1974 epizootic

At the end of the 1974 epizootic of bovine congenital arthrogryposis and hydranencephaly in south-eastern New South Wales, an Australia-wide serological survey (about 4,000 serums) was made to determine the ditribution of cattle possessing serum neutralising antibodies against Akabane virus. Eighty per cent of the serums from cattle in northern Australia (Western Australia, Northern Territory, and Queensland) were positive. A detailed study in the epizootic area in New South Wales (particularly around Bega) showed that 80 to 100% of serums from cows in herds in this area possessed neutralising antibodies. The animals possessing antibodies extended as far south as Genoa in north-eastern Victoria, and as far west as Darlington Point on the Murrumbidgee River. There were no positive herds along the Murray River, where an outbreak of the mosquito-borne disease Murray Valley encephalitis occurred in 1974. Serums tested from cows in the rest of Victoria, South Australia, south-western Western Australia, and Tasmania were negative. Arthrogrypotic calves born in Tasmania and south-western Western Australia were not associated with the presence of Akabane virus. In Papua New Guinea, serums collected from cattle at Boroka, Lae, and Goroka did not possess neutralising antibodies. The distribution of cattle possessing antibodies in Australia would fit a spread of the virus by Culicoides brevitarsis, a biting midge from which Akabane virus had been isolated on three occasions. The possibility of other vectors, as well as C. brevitarsis, was suggested by the presence of cows possessing antibodies at Alice Springs, where this biting midge has not been found. Possibly most cattle in northern Australia become infected early in life. The epizootics in New South Wales could occur when seasonal conditions allow a southerly extension of virus-infected C. brevitarsis which feed on susceptible pregnant animals. C. brevitarsis also bites sheep, and both neutralising antibodies to Akabane virus and congenitally deformed lambs have been observed in the epizootic area. An understanding of the distribtuion of Akabane virus and C. brevitarsis, a possible Australian vector for bluetongue virus, may prove useful if bluetongue should enter Australia.

Epizootic congenital arthrogryposis-hydranencephaly syndrome in cattle: isolation of Akabane virus from affected fetuses

Previous serolgoical studies strongly suggested Akabane virus to be the etiologic agent of epizootic abortion and congenital arthrogryposis-hydranencephaly in cattle, and this view was further corroborated in this study by the isolation of the virus from an aborted fetus in an epizootic of the disease and from a fetus extracted froma cow which was suggested by serologic tests to have a recent infection with the virus. The latter fetus had histological changes of encephalomyelitis and polymyositis, and specific antigens of Akabane virus was shown by the immunofluorescent technique in brain tissues as well as skeletal muscular tissues. The virus was recovered from various fetal tissues and fluids, and in relatively large amounts from brain, spinal cord, cerebral fluid, skeletal muscles and fetal placenta. The intracranial inoculation of suckling mice, 1-2 days of age, was the most sensitive system for Akabane virus isolation and HmLu-1, a continuous cell line from hamster lung, seemed almost as sensitive as suckling mice.

Quantitative studies on adsorption, elution, and haemagglutination of vesicular stomatitis virus

Radioactively-labelled VSV, both Indiana and New Jersey serotypes, were rapidly and efficiently adsorbed onto goose erythrocytes, but only within a narrow range of pH and at low temperatures. Under optimal conditions for adsorption, both infectivity and haemagglutinating activity of VSV were reduced. A basic difference between the two serotypes was identified: adsorption and haemagglutination of the Indiana serotype were stable even at pH 9.0 and at 37 degrees C, whereas New Jersey serotype was eluted slowly at +0 degrees C and at pH 6.4 and rapidly at a higher temperature and pH. The rapid elution offers a useful method for purification of New Jersey serotype. Particle counting of VSV showed that 10 to 50 virus particles were required for one PFU. Haemagglutination was not a sensitive method for assaying small amounts of VSV; 3--20X10(7) virus particles or more than 10(7) PFU corresponded to one HAU.

Congenital anomalies in a neonatal white-tailed deer in Alberta

In September, 1973, a live male 2-3 day old white-tailed deer (Odocoileur virginianus) with multiple anomalies of the head and forelimbs was found near Lethbridge, Alberta. Notable gross findings inculded brachygnathia inferior, atypical incisor tooth alignment, medially folded ears, humero-radial arthrogryposis and bowing of the radius and ulna. Hematologic determinations indicated increased erythrocyte, hemoglobin and hematocrit levels. Histopathologic examination revealed mineralized spherites in the cerebellum and midbrain.

Serologic evidence for etiologic role of Akabane virus in epizootic abortion-arthrogryposis-hydranencephaly in cattle in Japan, 1972-1974

In the outbreak of abortions, premature births, stillbirths and congenital arthrogryposis-hydranencephaly (AH) syndrome in Japan during the summer through winter of 1972-73 and 1973-74, precolostral sera from calves with congenital AH syndrome and normal calves were tested for neutralizing antibodies against some arboviruses, i.e. Akabane, Aino, Getah and Japanese encephalitis (JE) viruses. The incidence of antibody for Akabane virus was very high in calves with AH syndrome (49/59 or 83 per cent) as compared with normal calves (3/11 or 27 per cent), indicating an intimate correlation between the AH syndrome and precolostral anti-Akabane antibody. Three stillborn fetuses also had anti-Akabane antibody. On the other hand, no precolostral serum antibody for the other viruses was detected in any of the calves tested. The mothers of these calves, normal and with AH syndrome, had anti-Akabane antibody in high percentages (44/52 or 85 per cent and 7/8 or 88 per cent), whereas a few of the mothers had antibodies for the other viruses. Serological surveys indicate a wide dissemination of Akabane virus in epizootic areas during the summer months of 1972 and 1973. Thus, 8 groups of cattle in epizootic areas showed high rates of seroconversion for Akabane virus during the 1972 or 1973 summer. Very high incidences of Akabane antibody were shown among cattle in epizootic areas but extremely low incidences in near-by non-epizootic areas. The geographic distribution of anti-Akabane antibody among cattle throughout the country in the 1973 spring generally agrees with the pattern of case distribution in the 1972--73 outbreak. All these findings strongly suggest that Akabane virus is the etiological agent of the outbreaks. Further studies are needed, particularly isolation of the virus, demonstration of infection with the virus in lesions by immunofluroescence and production of intrauterine infection by experimental infection of pregnant cows.