Isolation of multiple serotypes of bluetongue virus from sentinel livestock in Malaysia.

Sixteen isolations of bluetongue virus (BTV) were made from the heparinised bloods of 4 groups of cattle and sheep in Peninsular Malaysia. These viruses were typed as BTV serotypes 1, 2, 3, 9, 16 and 23. Multiple serotypes of BTV are apparently endemic in Malaysia and in other countries in the region.

Infection of Culicoides brevitarsis and C. wadai (Diptera: Ceratopogonidae) with four Australian serotypes of bluetongue virus.

Field collected Culicoides brevitarsis Kieffer and C. wadai Kitaoka were fed on sheep that had been artificially infected with a field-isolate of either bluetongue virus serotype 3 (BLU3), BLU9, BLU16, or BLU23. Feeding rates averaged 11.9% but were variable. Survival of midges during incubation tended to be enhanced by the addition of antibiotics and fungicide to the diet. Attempts to transmit virus to sheep by the bite of these two species were unsuccessful. Both C. brevitarsis and C. wadai had infection rates of between 1.3 and 1.5% for BLU16 and BLU23. The infection rate for BLU3 in C. wadai was low at 0.07% whereas those for BLU3 in C. brevitarsis and BLU9 in both species could not be calculated because of insufficient virus isolations. The relatively high infection rates for BLU16 and BLU23 suggest that both C. brevitarsis and C. wadai are capable of circulating these viruses in the field.

Clinical pathology of Australian bluetongue virus serotype 16 infection in merino sheep.

Viraemic blood from an ox naturally infected with Australian bluetongue (BLU) virus serotype 16 was passaged twice in sheep. Twelve 2- to 4-years-old Merino ewes, negative in a bluetongue agar gel immunodiffusion test, were inoculated with viraemic blood from the second sheep passage. They were examined for 18 days and compared with a control group. Significant changes in haematological measurements, namely packed cell volume, total white cell count and lymphocyte count, and in plasma enzyme concentrations, namely aspartate transaminase and creatine kinase, occurred in the infected sheep. All infected sheep became sick. The antibody response, and clinical and necropsy findings were consistent with other reports of mild to moderate disease with Australian BLU serotypes.

Susceptibility of Bos indicus and Bos taurus to Anaplasma marginale and Babesia bigemina infections.

The reaction of Bos taurus and pure-bred Bos indicus heifers to infection with the intraerythrocytic parasites Anaplasma marginale and Babesia bigemina was studied. B. bigemina infection at 18 months and A. marginale infection at 13 or 24 months resulted in slightly less severe reactions in pure-bred Bos indicus cattle than in Bos taurus. In both breeds, the reaction to A. marginale infection was more severe in older cattle. The severity of B. bigemina infection was not affected by a previous infection with A. marginale.