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From dull to dead – a horse with Hendra virus

 Unusual presentation:

Horse depressed, breathing rapidly and sweating, with nasal discharge , and swollen eyelids and supraorbital fossae.

Above: Hendra-affected lung from CSIRO EAD Field Guide (Images on this page from file, not the case).

Time and location: Northern Queensland, year not specified.

Case definition: Horse with elevated temperature, nasal discharge and difficult breathing. Clinical signs developing over a few days.

Disease mapping: The sick horse was the only horse on this property. It had not moved from the property since it first arrived a few years ago. The property backs onto a national park and the owner had observed feral horses in the area. The horse spent a lot of time around the forest along the creek. The horse had been vaccinated against tetanus but not Hendra.

Gross findings: Clinical examination revealed a temperature of 40°C and petechiae of the conjunctivae – in addition to the difficult breathing, nasal discharge and facial swelling. The owners saw that the horse was dull and unwilling to move on Friday. Its condition worsened and the vet was called in on Sunday afternoon. Because Hendra virus infection was a plausible differential diagnosis, the vet wore PPE to collect samples and provide symptomatic treatment. The horse was found dead on Monday morning and buried on site on Tuesday with supervised decontamination of the site.

Differentials based on the history and signs included some EADs: Hendra, African horse sickness, infection with Australian bat lyssavirus and anthrax. Other non-EAD differentials considered included snake bite, toxic plants and chemicals, endotoxaemia, acute fulminating colitis or pneumothorax.

Laboratory findings: The samples submitted from the live horse were blood (plain & EDTA), and swabs (nasal, oral, rectal). Diagnostic tests were Hendra positive.

Animal / management / environment risk factors: Factors to consider when assessing the potential for a Hendra virus spill-over are not specific to this case and include: proximity of flying fox roosts; previous incidents in the area; and Hendra vaccination status of the horses (still use PPE even if vaccinated to protect human health).

Recommendations to the producer: For any horses on this property in the future – Hendra vaccination is a must, and exclusion of access to grazing beneath forest trees.