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Several lyssavirus species occur in Africa (Rabies virus, Lagos bat virus, Mokola virus, Duvenhage virus, Shimoni bat virus and Ikoma lyssavirus), displaying a high sequence diversity between isolates belonging to the same species. There is limited information about comparative pathogenesis of these African lyssaviruses and this precludes authoritative opinion on the potential public and veterinary health impact. In this study, an analysis of representative African lyssaviruses attempted to correlate viral genomic sequence similarities and differences with the corresponding pathogenic profiles observed in mice. The study demonstrated that the virus isolates evaluated could be lethal to mice when introduced intramuscularly and that different isolates of the same lyssavirus species differ in their virulence. Using real-time polymerase chain reaction (PCR), viral RNA was detected in brain tissue, but no viral RNA was detected in the salivary glands or blood of mice that succumbed to infection. Comparison of known pathogenic domains indicated that pathogenicity is likely to be dependent on multiple domains. Cumulatively, our results re-emphasised the realisation that the pathogenicity of a lyssavirus species cannot be deduced based on studies of only a single isolate of the species or a single pathogenic domain.

A rapid immunodiagnostic test kit was evaluated against a selection of isolates of lyssavirus genotypes occurring in Africa. The test was carried out in parallel comparison with the fluorescent antibody test (FAT) and isolates representing previously established phylogenetic groups from each genotype were included. The specificity of the rapid immunodiagnostic test compared favourably with the FAT and was found to detect all representatives of genotypes 1, 2, 3 and 4 in brain samples of either field cases or suckling mouse brain inoculates.

Bovine babesiosis is responsible for serious economic losses in Uruguay. Haemovaccines play an important role in disease prevention, but concern has been raised about their use. It is feared that the attenuated Babesia bovis and Babesia bigemina vaccine strains may be transmitted by the local tick vector Boophilus microplus, and that reversion to virulence could occur. We therefore investigated the possibility that these strains could be transmitted via the transovarial route in ticks using a Babesia species-specific polymerase chain reaction (PCR) assay. DNA was extracted from the developmental stages of the tick vector that had fed on calves immunized with the haemovaccine. It was possible to detect Babesia DNA not only in adult ticks, but also in their eggs and larvae. In addition, it was shown that calves infested with larvae derived from eggs laid by ticks fed on acutely infected calves, were positive for Babesia using PCR. Caution should therefore be shown with the distribution of the haemovaccine in marginal areas. It is still advisable that suitable tick control measures be used to prevent transovarial transmission and the potential risk of attenuated Babesia reverting to virulence.

Diagnosis of Rift Valley fever (RVF) is based on serology and virus isolation. The disadvantages of the former include poor sensitivity, high cost, risks associated with using infectious virus as antigen, the lengthy duration of ELISA as well as cross-reactivity with other Phleboviruses. We developed, optimised and evaluated a one-tube reverse-transcription-polymerase chain reaction (RT-PCR) for the detection of Rift Valley fever virus (RVFV) in ruminants. The PCR primers for this assay were designed to anneal to a region within the M segment of the virus genome, encoding glycoproteins G1 and G2. A PCR amplicon of 363 bp was obtained. The sensitivity of the assay was determined to be 0.25 TCID50. This test should allow for the early and rapid detection of RVFV in both serum and whole blood. In addition, it could facilitate the quantification of antigen for the manufacture of current vaccines.

The 3A non-structural protein of foot-and-mouth disease viruses is a relatively conserved protein comprising 153 amino acids. Recent studies have demonstrated correlation between mutations in the 3A non-structural-protein-coding region, including a 10-amino acid deletion, and attenuation of the viruses in cattle. Although the 3A coding region of several type A, O and C isolates has previously been described, nucleotide sequence data of the 3A coding region of the South African Types (SAT) 1, 2 and 3 viruses are limited. Therefore, the 3A non-structural-coding region of different SAT serotypes was determined, analysed and compared to that of European, South American and Asian isolates. The 3A regions of the SAT isolates investigated differed markedly from that of types A, O, C and Asia-1, but were similar within the group.

Antigenic and nucleotide sequence analyses have shown that two distinct biotypes of rabies virus are circulating in South Africa. One of these typically infects members of the family Canidae, while the other comprises a heterogeneous group of apparently indigenous viruses, infecting members of the Viverridae family. In recent times, it has become evident that a considerable amount of cross-infection may occur and the manifestation of viverrid rabies in non-viverrid animals in particular appears to have become more commonplace. Consequently, the need to rapidly distinguish between rabies virus biotypes has become increasingly important in efforts to monitor the epidemiology of rabies in the southern African region. In this study, a nested polymerase chain reaction (PCR) assay was developed to distinguish between these two groups of rabies viruses. Consensus oligonucleotides were used to amplify the cytoplasmic domain of the rabies virus glycoprotein and the adjacent intergenic region. The resultant amplicon was subsequently used as template in second round heminested PCR in the presence of type-specific primers, thereby successfully generating amplicons of characteristic size for each biotype.

Nucleic acid sequence analysis was used to determine the phylogenetic relationships amongst rabies viruses isolated from typical canid hosts such as bat-eared fox, jackal and dog in South Africa (SA). Geographical factors were taken into account in the selection of isolates and three different regions within the genomes of the isolates were compared for their use as phylogenetic indicators. The three genome regions, being the cytoplasmic domain of the G-gene, the G-L intergenic pseudogene and the antigenic domain II of the N-gene were found to differ in terms of the of nucleic acid conservation, but produced similar results when analyzed phylogenetically. The SA canid isolates were found to be closely related and could clearly be distinguished from all other rabies virus groups for which sequence data is available. In addition four SA mongoose rabies isolates were studied which were shown to be distant from the SA canid rabies virus group as well as from any other rabies viruses (or group) for which sequence data is available. Our results also indicate that spillover between the distinct canid and viverrid host reservoirs may occur.