African horse sickness (AHS) was diagnosed for the first time in southern Portugal in autumn
1989, following outbreaks in Spain. AHS virus presence was confirmed by virus isolation and
serotyping. An eradication campaign with four sanitary zones was set up by Central Veterinary
Services in close collaboration with private organizations. Vaccination began on 6 October. In
February 1990, vaccination was extended to all Portuguese equines (170000 animals). There
were 137 outbreaks on 104 farms: 206 of the equidae present died (16%) or were slaughtered
(14%); 81·5% were horses, 10·7% were donkeys and 7·8% were mules. Clinical AHS occurred
more frequently in horses than donkeys and mules. In the vaccinated population, 82 animals
(62·2% horses and 37·8% mules and donkeys), died or were slaughtered due to suspected or
confirmed AHS. One year after ending vaccination, December 1991, Portugal was declared free
of AHS. Cost of eradication was US$1955513 (US$11·5/Portuguese equine).