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: Semireserves were created by the European Conservation Project for scientific research in preparation for reintroduction in the wilderness. They are defined as enclosures large enough to carry a group of Przewalski horses throughout the year without any additional feeding. The semireserve offers diverse opportunities for significant scientific research. As part of a general screening program, the hoof development in a group of Przewalski horses was investigated in the semireserve Schorfheide near Berlin. Since the foundation of this semireserve in 1992, veterinary treatment was not necessary with the exception of hoof trimming in two animals in 1993. However, major health problems were encountered in the spring of 1999, when three other mares showed signs of laminitis. The initial diagnosis by the authors and the local veterinary surgeon based on observation of behaviour, gait, stance, walk and trot of three mares whose initial weights were higher than those of the healthy mares. The initial diagnosis was confirmed by palpation and the occurrence of very deep horn rings on all hooves and a laminitic horn ring on the right front hoof of one mare. An adequate laminitic therapy was not possible under the conditions of a semireserve. The applied management aimed at two goals: 1. To reduce endotoxin production and acidosis in the horses by reducing the ingestion of carbohydrate rich food. 2. To reduce the mares level of activity and to prevent tearing of the suspensory apparatus of the coffin bone. To achieve these two goals it was decided to remove the three laminitic mares from the rich pasture in the main part of the semireserve and to confine them onto the poorer pasture of the small separately fenced area. All three affected mares had fully recovered from their laminitic condition. Prevention of grass laminitis can be achieved by the following measures: 1. Reduction in grass intake could be achieved by increasing the grazing pressure by an increase in stocking rate of the horses or mixed grazing with another species such as sheep. 2. A longer term solution to the problem may well be to sow specific varieties of grass with lower concentrations of water soluble carbohydrate.

Abstract: Field observations of 400 totally unmanaged feral horses on Sable Island, Nova Scotia, were complemented by oestrogen determinations in faecal samples from 154 identified females over a 4-year period (454 mare-years). Of mares that were sampled throughout the year and subsequently produced foals, 92.1% exhibited elevated faecal oestrogens between 15 October and 30 March. The results confirm that faecal oestrogens are a useful indicator of pregnancy after approximately 120 days gestation. Distribution of foaling resembled that seen in other feral populations, with 95% of births occurring from April through July. The foaling rate for mares aged 3 years or older was 62.0%, with 50.7% of mares foaling in 3 or 4 years. Foaling rates were low (4.1%) in mares bred as yearlings and rose with age to 70.8% in those bred as 4-year-olds. Fetal loss after Day 120 was deduced from faecal oestrogens to be 26.0% overall, with marked variation from year to year (9.6-37.3%) and with age (70.0% in those bred as yearlings, decreasing to 5.6% in those bred as 4-year-olds). Of 58 mares aged 2 years or older that were sampled every year, about half (49.6%) the barren years were attributable to fetal loss after 120 days gestation. All mares conceived in at least 2 of the 4 years, suggesting that pregnancy loss, even after Day 120, is as important as failure to conceive in causing barren years.