African horse sickness is a highly contagious and fatal disease that affects horses, donkeys, and mules. It is caused by the African horse sickness virus, which is transmitted by biting midges. There are 9 different serotypes of the virus. The disease has an incubation period of 2 to 21 days on average. Symptoms vary in severity from sudden high fever and respiratory issues to slower developing fever and edema of the head and neck. The disease has high mortality rates, even in milder cases, and causes lesions such as hydrothorax, bronchopneumonia, and hemorrhages in organs. Diagnosis is made through observed symptoms and lesions, inoculating mice, and virus neutralization tests.

1. AFRICAN HORSE SICKNESS
Afnan Rashid

2. Introduction
• Equine plague
• Lapesteducheval
• It is a highly fatal disease of horses, mules and donkeys caused by
African horse sickness virus of the family Reoviridae of the genus
Orbivirus.
• There are 9 antigenically distinct serotypes of AHS virus.
• Virus seen in tissues and fluids in the body.
• Not contageous

3. Infection:
• 1. Bitting by gnat-culicoides.
• 2. Zebra is reservoir for the virus.
• Incubation period:
• Incubation period varies from 2 to 21 days. An average one is 6 days.

4. Symptoms:
• (A) Acute pulmonary form (DUNKOP):
• 1. Most common.
• 2. Sudden rise in temperature with concomitant respiratory
• symptoms.
• 3. Pulmonary oedema, nasal discharge, profuse swetting.
• 4. Death in few hours.

5. • (B) Sub-acute cardiac form (DIKKOP):
• 1. Fever develops slowly and lasts longer.
• 2. Characteristic oedema of head (temporal fossa), lips, eyelids,
• neck and chest.
• 3. Tongue swollen, cynotic with petchiae on the ventral
• surface.
• 4. Paralysis of oesophagus-difficulty in swallowing.
• 5. Cardiac failure-pulmonary edema-hydropericardium and
• endocarditis.
• 6. Mortality high due to pulmonary form.
• 7. Death due to cardiac failure.

6. • (C) Mild form
• 1. Initial rise of temperature which returns to normal within 1-3 days.
• 2. Anorexia, dyspnoea and mild conjunctivitis.
• 3. Mortality varies 25-90%.

7. Lesions
Pulmonary form
• Hydrothorax, usually accompanied by severe oedema of subplural,
interlobular stroma and fills alveoli in many lobes.
• There is leucocytosis with Bronchopneumonia.
Cardiac form:
• Hydropericardium with petechae and inflammatory oedema in
epicardium.
• Myocodial necrosis, haemorrhages.
• Lymphopoenia is evident in spleen and lymph nodes.

8. • Oedema around pharynx might be due to paralysis of oesophagus.
• Haemorrhages in gastric mucosa and pelvic fat of kidneys.
Diagnosis:
• 1. Based on symptoms and lesions
• 2. Intracerebral inoculation of mice.
• 3. Virus neutralisation test.