Aetiology and epidemiology of malignant catarrhal fever in Indonesia and Australia

• Research Institute for Veterinary Science, Indonesia

Malignant caterrhal fever (MCF) affects cattle, deer, some wild ungulates and buffalo in many countries. Despite its usually low morbidity, its high mortality rate makes this herpes virus disease a serious economic problem. It appears to spread not from one victim to another but only from apparently healthy carriers such as wildebeest and possibly sheep. Indeed, its two recognised forms are knows as wildebeest-associated (WAMCF) and sheep-associated (SAMCF), which occurs world-wide, including Africa. Recent work has shown that infective WAMCF virus comes from the nasal cavities of wildebeest calves. However, research has failed to establish the etiology of SAMCF, although certainly this form occurs more frequently when cattle graze with sheep and especially when the animals are housed together.
The two forms have very similar clinical and pathological features in cattle, and examination of sera from Australian sheep and cattle using the African virus as antigen suggest a close antigenci relationship.
In Indonesia, both local and imported Bos taurus and B. indicus cattle suffer from SAMCF, but the disease causes much greater problems in the widespread swamp buffalo and especially in the Bali cattle, B. javanicus. Indonesian consider Bali cattle good beef-producers, so a large trade in the animals occurs between the islands. Moreover, transmigration programs move whole villages to other islands, with their livestock, and the incidence of MCF in these migrant populations seems to be high.

Research in this project will investigate the etiology of MCF in Indonesia and Australia, and its epidemiology in Indonesia, in order to devise potential means of rapid diagnosis and logical control measure. Keeping large ruminants separated from sheep can apparently prevent outbreaks in experimental environments and in management systems used in countries like Australia. However, for practical and social reasons it may not be generally feasible in the traditional systems in developing countries such as Indonesia. Accordingly, the project will place some emphasis on identifying possible periods of high risk, such as post-lambing.
Initially the research will fall into three main sections: contact transmission; antibody and antigen detection; and other sheep studies. All three will utilize the WC-11 strain of WAMCF. If these fail to identify the SAMCF agent, a fourth phase will employ molecular DNA techniques.
Contact transmission studies will include attempts to isolate virus or demonstrate antigen. Scientists in Indonesia will investigate transmission from sheep, especially during pregnancy and lambing, to swamp, to swamp buffalo, to Bos javanicus, to B. taurus and B. indicus and to other sheep. Concurrent Australian tests at Oonoonba will concentrate on sheep-to-sheep transmission.
In serological and immunological experiments to detect antibody, scientists in Indonesia will use the WC-11 strain in SN, IIF and ELISA procedures, and will test sera from the animals involved in the transmission studies. Antigen detection in both Indonesia and Australia will involve either the WC-11 strain of WAMCF or antisera from sheep known to transmit SAMCF or from clinically affected cattle.
Sheep consistently associated with SAMCF transmission have been shown to be antibody-positive to WC-11. Such animal will be used, together with antibody-negative sheep, and their foetuses and lambs, for tests to isolate free infectious virus (concentrating on nasal and throat washings) and for antibody conversion.
In needed, the molecular DNA techniques will be used to seek evidence of viral DNA resembling the genome of WC-11. Approaches would include gene mapping and, especially, hybridisation experiments.
It is hoped that the project will make significant advance towards establishing diagnostic procedures and defining epidemiological features and control measures. Establishment of rational control measure would benefit Indonesia, Australia and other countries.