Everything you need to know about African horse sickness
From time to time, the world records an epidemic of the African horse sickness (AHS). In sub-Saharan Africa, this insect-borne disease is common in horses, zebras, mules, donkeys, camels, and even dogs (especially if the dog eats infected horsemeat). In fact, the World Organization for Animal Health named it one of the most common equine diseases in the world.
Symptoms of African horse sickness
African horse sicknesshas different forms. Symptoms often depend on the strain of the ASHV. However, infected animals usually exhibit the following symptoms:
• Acute breathing symptoms: often characterized by lack of oxygen, hydropericardium and interlobular edema
• Cardiac form: characterized by fever, edema of the chest, head and neck, as well as congestive heart failure
• Pulmonary form: a more severe form of the disease characterized by fever, coughing, depression and severe dyspnea
• Horse sickness fever
Other signs include:
• Severe bleeding on the tongue, and colic
• bleeding eyes
• Infected animals may stand with parted legs and protracted heads
• Fitful coughing
• Expanded nostrils
Mortality rates are higher for animals infected with the pulmonary form of the disease. Statistics show that death occurs in 95% of reported cases where the animals showed symptoms of the pulmonary form of ASHV.
Mortality rates are slightly lower in animals that show symptoms of the cardiac form of the disease. Statistics show that approximately 50% of infected animals that display the cardiac symptom die.
Death is almost certain if the animal shows symptoms of both the cardiac and the pulmonary forms of ASHV.
What causes African horse sickness?
The African horse sicknessvirus (AHSV) is the primary cause of African horse sickness. The biting midge transmits this virus. This insect is most active in the rainy seasons especially when the rains alternate with warm and humid climatic conditions.
Important facts to note about African horse sickness
• It is of the species Orbivirus and in the family of Reoviridae
• Its diameter ranges from 55mm to 70 mm
• It is transmitted through the bites of infected Culicoides spp
• The virus comes in nine immunologically different serotypes
• AHSV is incapacitated by radiation, formalin and acetylethyleneimine byproducts.
Animals can also contract this disease from contact with infected sharp objects and other contaminated blood-feeding insects.
Treatment of the African horse sickness
The most common forms of treatment for infected animals is:
• Excellent husbandry
• Adequate rest
However, symptoms and complications can be treated with medications. Veterinarians usually treat it giving different medications that help to boost heart, and lung function.
How to control African horse sickness
When there are infected animals in a farm, the best way to control the disease is to :
• Restrict animal movement
• change the farming system
• make sure there are no vectors in the farm
The World Organization for Animal Health (OIE) encourages the adoption of the following preventive measures in the control of the African horse sicknessvirus
1) Notify relevant authorities
Every single case of AHS must be reported to relevant authorities. Often, farmers are unable to manage and contain the disease. The authorities will send someone to the area to ensure that the right treatment and control measures are put in place to prevent the spread of the disease.
2) Restrict animal movement
This control measure helps to prevent the spread of the AHSV from one farm to another. Restrict the movement of all infected animals to a safe stable.
3) Carve out safe areas
A hundred-kilometre protection zone should be set up around the farm where the infected animal is being quarantined. A 50-kilometre surveillance area should also be mapped out and set up. The idea is to prevent the spread of the disease.
4) Quarantine of all farm animals
When the vector is at its most active state, it is better to confine all animals to their stables or pens (depending on what animals there are).
During this confinement period, the farmer must employ vector control strategies. These include spraying safe insecticides, insect repellants. In extreme cases, the farmer may fumigate the entire farm.
It is important to note that fumigation works better when the animals are taken to a different pen before spraying. Do not use harsh chemicals while the animals are still in their pens.
4) Ask your veterinarian to recommend safe insecticides for animals
You can apply insecticides and insect repellents directly on animal fur, on the farm and in farm vehicles. This control measure is particularly effective on horses, cattle and sheep. But ask your veterinarian to recommend a safe and effective brand.
5) Vaccinate all animals
Take advantage of the vaccination programs in your area. Ensure that all your horses receive the African horse sicknessvaccine.
In the event of an outbreak, invite a vet to vaccinate all uninfected animals that are in the protection area. Below is a list of suggested African horse sicknessvaccines:
• Monovalent inactivated vaccines
• Live attenuated vaccine polyvalent or monovalent
• Recombinant subunit vaccines
6) Promote surveillance programmes
Surveillance programs increase the chances of early detection. ASHV is easier to treat when you detect it early.
Animals are more likely to survive this sickness if they receive the AHS vaccine and if the right control measures are applied on animal farms, conservation areas and zoos. If, however, there is an outbreak of the disease, it is best to notify relevant authorities and to call in a veterinarian.