Hendra virus is fatal zoonotic disease caused by infection with the hendra virus (HeV), formally known as equine morbillivirus. It is a concern for horses living in Australia. HeV causes infection in mainly horses and, rarely, in humans and dogs. Hev is a paramyxovirus of the genus Henipavirus, subfamily Paramyxoviridae. HeV was first identified during an outbreak of acute respiratory disease in 21 Thoroughbred racehorses living in the Brisbane suburb of Hendra, Australia, in 1994. The trainer and stable hand also became infected and died. In 1995, a third human case occurred during a necropsy examination of two of the horses that had died as a result of the Hendra virus. Since then, there have been eleven outbreaks confined along the east coast of Australia, involving the death of at least 51 horses. Horses are the intermediate hosts for transmitting the infection to humans through close contact during care of sick horses or during necropsy and/or handling of dead infected horses.

Clinical signs of Hendra Virus

Hendra virus causes a wide range of clinical signs in horses. It should be considered a possible cause of any sick horse with an illness of an unknown origin, who has progressive signs leading to rapid deterioration in health. Signs of hendra virus in horses have a rapid onset and progressively worsen fast. They may be general at first and often include signs related to the respiratory tract and/or nervous system. General signs include:

• Depression
• Frequent weight shifting between legs
• Fever up to 41°C (105.8°F)
• Increased heart rate

Respiratory tract signs include:

• Rapid breathing
• Difficulty breathing
• Nasal discharge upon death which can be initially clear, progressing to stable white froth or stable blood-stained froth.

Nervous systems associated with Hendra virus include:

• Aimlessly walking in a dazed state
• Head tilting
• Circling
• Wobbly gait
• Apparent loss of vision in one or both eyes
• Muscle twitching
• Inability to rise
• urinary incontinence

How the Virus is Spread

Fruit bats (Pteropus species), also known as flying foxes, are the natural reservoir host responsible for spreading this virus. The exact mode of HeV transmission between flying-foxes, or flying-foxes to horses has not yet been definitely determined. Hendra virus is transmitted two ways:

• Infected flying foxes to horses - making it important that horse food and water containers are not placed under or near fruiting or flowering trees.
• infected horses to humans and other animals -

sick horses must be isolated.

Virus Life Cycle

Hendra virus has an 4-16 day incubation period. The clinical course of the disease is typically short, with most horses dying within 48 hours of initial onset of clinical signs. Hendra virus will not survive for longer than several hours to days outside of the animal host.