Systematic Veterinary Virology

HORSES

• The per-acute pulmonary form (also referred as dunkob) has a short incubation period of 3-5 days with 95 per cent mortality. The course of the infection is 3 days. The infection is characterized by fever (40-41°C)  lasting 1-2 days, congested ocular, nasal, and oral mucous membranes, increased respiratory rate, wide abnormal stance with head and neck extension, flared nostrils, forced expiration resulting in heave lines, profuse sweating, spasmadic cough and appearance of frothy and serofibrinous blood-tinged fluid from nostrils. The death of animals is due to anoxia.
• The sub-acute cardiac form (also referred as dikkob) has an incubation period of from 7-14 days and with a mortality rate of around 60 per cent. This form of the disease is characterised by fever (39-41°C) lasting 3-6 days, oedema of the supraorbital fossa, oedematous swellings over the head and eyelids, lips, cheeks and under the jaw, petechial hemorrhage of conjunctiva and ventral surface of tongue, depression and appearance of colic signs. Death results from cardiac failure. 
• The acute or mixed form is a combination of the previous two types with an incubation period of from 5-7 days and the disease shows itself initially by mild pulmonary symptoms followed by the typical oedernatous swellings of the cardiac form. 
• Horse sickness fever. This is the mildest form, characterised by a febrile (very active and nervous) reaction with low temperatures in the morning rising to a high peak in the afternoon. Other symptoms include slight congestion of conjunctivae, increased pulse rate, mild anorexia and mild depression