Complete sequence of two tick-borne flaviviruses isolated from Siberia and the UK: analysis and significance of the 5' and 3'-UTRs.

The complete nucleotide sequence of two tick-transmitted flaviviruses, Vasilchenko (Vs) from Siberia and louping ill (LI) from the UK, have been determined. The genomes were respectively, 10928 and 10871 nucleotides (nt) in length. The coding strategy and functional protein sequence motifs of tick-borne flaviviruses are presented in both Vs and LI viruses. The phylogenies based on maximum likelihood, maximum parsimony and distance analysis of the polyproteins, identified Vs virus as a member of the tick-borne encephalitis virus subgroup within the tick-borne serocomplex, genus Flavivirus, family Flaviviridae. Comparative alignment of the 3'-untranslated regions revealed deletions of different lengths essentially at the same position downstream of the stop codon for all tick-borne viruses. Two direct 27 nucleotide repeats at the 3'-end were found only for Vs and LI virus. Immediately following the deletions a region of 332-334 nt with relatively conserved primary structure (67-94% identity) was observed at the 3'-non-coding end of the virus genome. Pairwise comparisons of the nucleotide sequence data revealed similar levels of variation between the coding region, and the 5' and 3'-termini of the genome, implying an equivalent strong selective control for translated and untranslated regions. Indeed the predicted folding of the 5' and 3'-untranslated regions revealed patterns of stem and loop structures conserved for all tick-borne flaviviruses suggesting a purifying selection for preservation of essential RNA secondary structures which could be involved in translational control and replication. The possible implications of these findings are discussed.

Plant-derived immunocontraceptive vaccines.

The use of transgenic or virus-infected plants to produce vitally needed vaccines for developing nations has been made possible by rapid advances in plant molecular biology and biotechnology during the last decade. Plant-based vaccines would be a welcome development for many impoverished countries that lack the capital-intensive infrastructure required to produce much-needed vaccines. The approach would also be ideally suited to the delivery of oral immunocontraceptive vaccines to a wide range of herbivore species. This review looks at the progress made to date in the use of plants for vaccine production, how this technology may be used in the future to deliver immunocontraceptive vaccines to free-ranging wildlife species, and the many problems that will have to be overcome if this promising approach is to ever 'bear fruit'.

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.

Coccidiosis associated with post-weaning diarrhoea in beef calves in a dry tropical region.

The roles of helminths and coccidia in post-weaning diarrhoea in beef calves in the dry tropics were investigated. Diarrhoea occurred approximately one month after weaning in both anthelmintic treated and untreated calves. The highest numbers of coccidial oocysts were seen 29 days after weaning and 3 necropsies confirmed Eimeria zuernii coccidiosis. In the absence of wet overcrowded conditions, disease may have been precipitated by environmental interactions leading to suppression of host immunity. Other Eimeria identified were E. bukidnonensis, E. wyomingensis, E. bovis, E. auburnensis, E. cylindrica, E. ellipsoidalis and E. subspherica. The last 5 species are believed not to have been previously documented in Australia. The presence of E. canadensis was strongly suspected.