Abstract: Confirmed outbreaks of African horse sickness (AHS) occurred in the surveillance zone of the Western Cape in 1999 and 2004, both of which led to a two-year suspension on the export of horses. Light trap surveys in the outbreak areas showed that known vector competent Culicoides species, notably C. imicola, were abundant and present in numbers equal to those in the traditional AHS endemic areas. Isolations of AHS virus serotypes 1 and 7, equine encephalosis virus, and bluetongue virus from field-collected C. imicola in the surveillance zone demonstrated that this species was highly competent and could transmit viruses belonging to different serogroups of the Orbivirus genus. Molecular identification of recovered virus isolates indicated that at least two incursions of AHS into the surveillance zone had taken place in 2004. The designation of an AHS-free zone in the Western Cape remains controversial since it can be easily compromised, as evidenced by the two recent outbreaks. In light of the results reported in the present study, the policy of maintaining a large population of unvaccinated horses in the surveillance zone should be reconsidered, as it leaves them vulnerable to infection with AHS virus, which is the most pathogenic of all equine viruses.

Abstract: This is the introductory paper to a series on the ecology of arboviruses in Argentina. Epizootics of equine encephalitis have occurred since at least 1908, principally in the Pampa and Espinal biogeographic zones, with significant economic losses; human cases of encephalitis have been rare or absent. Both western equine and eastern equine encephalitis viruses have been isolated from horses during these epizootics, but the mosquitoes responsible for transmission have not been identified. A number of isolations of Venezuelan equine encephalitis (VEE) virus were reported between 1936 and 1958 in Argentina, but the validity of these findings has been seriously questioned. Nevertheless, serological evidence exists for human infections with a member of the VEE virus complex. Serological surveys conducted in the 1960s indicate a high prevalence of infection of humans and domestic animals with St. Louis encephalitis (SLE), and 2 SLE virus strains have been isolated from rodents. Human disease, however, has rarely been associated with SLE infection. Only 7 isolations of other arboviruses have been described (3 of Maguari, 1 of Aura, 2 of Una, and 1 of an untyped Bunyamwera group virus). In 1977, we began longitudinal field studies in Santa Fe Province, the epicenter of previous equine epizootics, and in 1980 we extended these studies to Chaco and Corrientes provinces. The study sites are described in this paper.

Abstract: REASONS FOR PERFORMING STUDY: Overstrain injuries to the superficial digital flexor tendon (SDFT) and suspensory ligament (SI) are among the most common musculoskeletal injuries which contribute to the considerable wastage of racing Thoroughbreds. Many epidemiological studies have demonstrated the prevalence of and risk factors for tendon injury when racing but have not included those injuries sustained during training. However, since tendon injury during training is seen commonly in clinical practice, it is appropriate to determine the overall prevalence of tendon injury sustained during both training and racing. OBJECTIVE: To determine the prevalence of overstrain injury to the SDFT and SL during training and racing among Thoroughbred flat racehorses in Japan in 1999. METHODS: A retrospective study was performed using a sample population of 10,262 Thoroughbred racehorses. The medical information database of Thoroughbred racehorses registered by the Japan Racing Association (JRA) in 1999 was analysed for SDFT and SL overstrain injury diagnosed by a veterinarian employed by JRA during training and racing. Jump racehorses were excluded from this study. RESULTS: The prevalence of forelimb SDFT tendonitis and SL desmitis was 11.1% (1130 cases) and 3.61% (370 cases) of the population, respectively. In the hindlimb, there were 0.06% (6 cases) and 0.14% (14 cases), respectively. Risks of SDF tendonitis in the forelimb in 3-year-olds or older horses were significantly higher than in 2-year-olds. In contrast, the risk of SL desmitis in the forelimb at age 3 and 4 years was 2.23 and 2.11 times higher, respectively, than in 2-year-olds, but this increased to 5.07 times in those age > or = 5 years. Entire males were at greater risk in comparison to females and geldings. CONCLUSIONS: The results suggest that the prevalence of SDF tendonitis and SL desmitis in the forelimb was associated with the horse's age and sex. The prevalence of SL desmitis increased further with age compared with SDF tendonitis, possibly reflecting a more rapid accumulation of degeneration in this structure. POTENTIAL RELEVANCE: The age-related risk demonstrated in this study provides further support that overstrain injuries are associated with accumulated degeneration. These data provide a valuable resource for further research into the aetiology of tendon injury in the racehorse.