CONGENITAL BOVINE EPIZOOTIC ARTHROGRYPOSIS AND HYDRANENCEPHALY

SUMMARY Epizootics of congenital neurological defects in calves have been recorded at various intervals in south eastern New South Wales for over 40 years. In 1974 a particularly severe outbreak occurred. Field observations of the clinical entities, their time of appearance, distribution and incidence were recorded in an attempt to determine an epidemiological pattern. The neurological entities observed occupied different time spans in the opizootic, the order of appearance being polioencephalomyelltis, arthrogryposis, hydranencephaly and micrencephaly. The probable period of infection correlated well with the likely presence of Culiciodes brevitarsus in the epizootic area and the distribution and incidence of neurologic cases likewise correlated well with the expected geographical and climatic distribution of C. brevitarsus in this period. The probable association of Akabane virus infection and the outbreak of stillbirths and abortions which preceded the neurologic entities is discussed.     

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.     

PIROPLASMOSIS IN BUFFALOES AND ITS SEROLOGICAL DIAGNOSIS BASED ON A HOMOLOGY BETWEEN BUFFALO AND BOVINE IMMUNOGLOBULINS

Babesia argentina, Babesia bigemina and Theileria mutans were transmitted experimentally from water buffaloes (Bubalus bubalis) to splenectomised Bos taurus calves. Buffaloes were positive to an indirect fluorescent antibody test for B. argentina when reagents of bovine origin were used. The formation of similar patterns during immunoelectrophoresis suggested a homology of buffalo and bovine serum proteins, particularly IgG.     

IMMUNOGLOBULINS IN BLOOD SERUM OF FOETAL PIGS

A total of 1,147 samples of blood serum, collected from porcine foetuses, were examined for the presence of immunoglobulin. The foetuses, from 182 sows, were sampled at abattoirs in Queensland during 1975. For detection and measurement of immunoglobulins, rabbit anti-pig serum and monospecific anti-pig IgG, anti-pig IgM and anti-pig IgA were employed in immunoelectrophoresis, double diffusion and single radial immuno-diffusion assays. Twenty-four foetuses (from 7 litters) had detectable IgG or IgM. None of the samples were positive for IgA. Two of the serums (from siblings) had high antibody titres to porcine parvovirus but in the remainder of the immunoglobulin-positive serums no antibody activity was detected.     

ANOXIA IN THE BOVINE FOETUS

SUMMARY Laparohysterotomies were performed, under local analgesia, on 18 plurigravid Hereford cattle and the response of their foetuses to anoxia was examined. All control and 4 of 6 foetuses subjected to 4 minutes of anoxia survived whereas all others died when the umbilical cord was clamped for 6 or 8 minutes. Death mostly occurred just before or soon after delivery, which was undertaken immediately following release of the umbilical clamp. In 2 cases, however, the calves survived for at least 2 days before being slaughtered when death appeared imminent. During the intervening period both animals failed to suck although one was able to stand temporarily following the oral administration of glucose and milk.