SPATIAL-ANALYSIS OF SEROCONVERSION OF SENTINEL CATTLE TO BLUETONGUE VIRUSES IN QUEENSLAND

Objective To assess quantitatively the spatial distribution of serocon version of Queensland cattle to bluetongue viruses. Design A sentinel herd study. Sample population Sixty-nine sentinel herds at 30 location s. Procedure Spatial clustering of seroconversion to bluetongue viruse s was investigated during the period from 1990 to 1994. Results Seroco nversion to only two bluetongue virus serotypes, 1 and 21, was observe d. The 14 herds, in which seroconversion to bluetongue virus serotype 1 was detected, were located only along the eastern coastal and sub-co astal region of Queensland, and were significantly (P < 0.05) clustere d. Locations at which seroconversion to serotype 21 was detected, were not significantly clustered. The results generally agree with field o bservations, except for the failure to detect seroconversion to blueto ngue viruses in north-western Queensland. Conclusion Bluetongue infect ion of cattle in north-western Queensland may be temporally sporadic. The dominance of serotype 1 in the Queensland cattle population may be the result of differential transmission by potential vector species. Long-term surveillance programs are important for defining disease sta tus of animal populations.