African Horse Sickness (AHS) has been reported in six districts in Namibia and owners of horses and donkeys have been warned to take precautionary measures.
Although the viral disease is non-contagious, it can have a devastating effect on animals of the horse-family, which include horses, donkeys and mules, as well as zebra. The latter is believed to be carriers of the disease that is transmitted by flying biting insects including mosquitoes and especially midges.
According to Namibia’s Directorate of Veterinary Services, 25 cases have been confirmed in Otjinene, Windhoek, Okahandja, Omaruru, Gobabis, and Mariental.
Johannes Shoopala, Acting Chief Veterinary Officer’ in a recent public notice said authorities have implemented immediate control measures to prevent the spread of the disease.
These measures include that veterinary permits and a full vaccination report are required for animals leaving or entering affected areas and quarantine for these areas.
Owners are advised to vaccinate during the recommended period from June 1 to October 31. It is also recommended that horses be moved from low-lying wet areas and stabled from sunset to sunrise, and the use of insect repellents.
Horse racing and endurance events are discouraged and not imports from infected countries or export from affected areas are allowed.
African horse sickness is endemic in sub‐Saharan Africa, but it has spread worldwide. The disease is caused by a RNA virus of the genus Orbivirus, family Reoviridae, which is transmitted by arthropod vectors, or ticks, that belong to various species of Culicoides. AHS is often fatal. Four clinical forms exist, namely: pulmonary, cardiac, mixed and febrile.
Nine serotypes have so far been identified. Laboratory confirmation of a suspected outbreak is required to identify the serotype responsible for the outbreak. The vaccine contains seven of the nine viral serotypes and is administered in two separate doses 21 days apart.
The first dose consists of three serotypes and the second of four serotypes. Serotypes 5 and 9 are not included, as 5 was found to be insufficiently attenuated, while serotype 6 protects against serotype 9.
In Namibia, AHS vaccination is done with a live attenuated vaccine produced by Onderstepoort Biological Products in Onderstepoort, South Africa.
Recommendation for vaccinations and competition
Horses must once a year be vaccinated for African Horse Sickness with both vaccine 1 and 2.
Horses should be vaccinated during the low vector period (1 June – 31 October) of the year as this will help prevent Culicoides midge transmission of the vaccine virus.
If a horse was vaccinated during the high vector period, the horse will not be allowed to take part race or do endurance trips for 40 days after the two AHS vaccines.
They should not be vaccinated with any vaccine within seven days of a competition. This period is however extended to 21 days for as some horses can have a reaction to the vaccine for up to three weeks after being vaccinated.
Exposure to Culicoides midges must be limited from the date of administration of the first bottle until 40 days after administration of the second bottle of vaccine. The infective period for AHS in sick horses is considered by the World Organisation for Animal Health (WOAH) to be 40 days.
An AHS infected horse can potentially act as a source of AHS virus for midges for 40 days from becoming infected; high viral loads are already present up to two days before a horse starts showing clinical signs.
Common signs of the disease include fever, difficulty breathing, coughing, sweating, and frothy discharge from the nostrils; the mortality rate can be as high as 70 percent.
Source references
African horse sickness: a description of outbreaks in Namibia https://www.academia.edu/15293969/African_horse_sickness_a_description_of_outbreaks_in_Namibia
Kaseke, M. (2025) Namibia confirms outbreak of African horse sickness The Star
https://www.thestar.com.my/news/world/2025/05/03/namibia-confirms-outbreak-of-african-horse-sickness
Public Resources: African Horse Sickness Vaccinations
