Conclusion
To put it all together- you have several horses affected with a severe, fatal respiratory disease that appears to have run its course in a matter of just a few days. Prominent clinical signs in the sick horses in the barn include depression, dyspnea, tachypnea, tachycardia, pyrexia, injected mucous membranes with a cyanotic border and nasal serosanguinous discharge, patchy sweating, ataxia and scleral icterus. The dead horse had a history of depression, dyspnea, and edema of the face, lips, and neck. According to the client, she appeared to improve slightly overnight after administration of an antihistamine, flunixin, and antibiotics. On necropsy you found a reddish colored frothy exudate within the airways and coming out of the nostrils, and severe pulmonary edema and congestion. Sound like any of your rule outs? What do you do next?
Is there a connection between an Australian cat, severe respiratory disease in horses, and a sick stable hand? You fear the worst and call state and federal authorities to look into the case. Diagnosticians at Plum Island find antibodies to Hendra virus in a rapid serologic test.
The farm is quarantined, you, the client, and her stable hand are sent to a hosptial for medical evaluation. Fortunately you and the client are fine, and the stable hand’s condition turns out to be a case of the flu, not Hendra. Noone else becomes ill in relation to this outbreak. Even though this disease is not very easily spread, you were wise to use many safety precautions during your necropsy!
While investigating this unusual and highly publicized foreign animal disease, diagnosticians from Plum Island succeed in isolating Hendra virus from hay samples you collected, so the diagnosis is confirmed. You really look like a hero! You inform them that an Australian cat was probably making a bed out of the hay bales in the barn. The client’s cats are caught and tested, and one is found to be positive.*
Apparently the cat that came from Australia was subclinically infected with the virus and urinated both on hay bales stored in the barn and probably in areas around the pasture as well. When the horses ingested feed contaminated with this urine, they became infected with Hendra virus. A team of wildlife biologists scour the farm and collect other wildlife species to determine if any are infected. Good work!
*Note: This is a hypothetical case and although cats have been shown to be infectable by Hendra virus under laboratory conditions, their role in the transmission of the disease is, in fact, still speculative. We do not have any information on the ability of cats to be subclinically infected and transmit the virus. However, many new emerging diseases begin in this manner, that is, introduction in a species that has not previously been thought to be a vector of the disease.
