West Nile Virus Infection

Description

West Nile Virus (WNV) is a mosquito borne virus belonging to the genus Flavivirus. Subtypes of WNV, previously known as Kunjin virus (WNV_KUN) are endemic in parts of Australia and has been present for many years. These are infrequently associated with disease in humans.

Horses, people and a variety of other animals, especially birds, may become infected through a bite from an infected mosquito. Like most other arboviral infections the disease is expected to occur during late summer and autumn. In Australia, disease has been limited to horses, although several cases have been suspected (though not confirmed) in dogs and alpacas. Most animals infected with WNV do not develop any clinical signs. Unlike strains of WNV found in the Northern hemisphere, Australian strains of WNV have not caused disease in birds.

In 2011, there was a large outbreak of neurological disease in horses in south-east Australia caused by a variant of the Australian strain WNV_KUN.

The initial signs of disease can be non-specific and may be mistaken for colic as horses appear depressed and reluctant to move, however these signs are soon followed by neurological signs. The most commonly encountered signs are those of ataxia (including stumbling, staggering, wobbly gait, or incoordination) but a range of other CNS signs may also be observed. Most affected horses recover uneventfully within a few days to weeks; however the disease is fatal in about 10% of cases.

It is important to differentiate the illness from Hendra virus infection particularly in areas where flying foxes are abundant and to take appropriate precautions.

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Diagnosis and tests available

Diagnosis

Diagnosis in horses and domestic non-avian species is based on the history, clinical signs, serology and other diagnostic tests where appropriate.

Tests available

¹ Turnaround times are provided as a guide only. For specific information about your submission please contact Customer Service.

²The WNV IgM ELISA is only suitable for equine samples and is the preferred test for blood samples collected from horses within 2 weeks of the onset of clinical signs. The first sample should be collected as soon as possible after clinical signs have been observed.

³Collection of paired clotted blood samples in the acute and convalescent phases of the illness (approximately 3-4 weeks apart) is recommended to confirm recent infection in mammalian non-equine species.

Specimen requirements

Note

• The risk of Hendra virus should be considered prior to tissue collection
• West Nile virus in Australia (Primefact)

Customer Service Contact Details

Phone: 1800 675 623
Email: laboratory.services@dpi.nsw.gov.au

Operating Hours

8:30am-4:30pm Monday-Friday (excluding public holidays)

8:30am-12:00pm Saturday (for deliveries only)

Postal address

Private Bag 4008, Narellan NSW 2567

Submission Forms:

Equine Horse Export Submission Form

Veterinary Specimen Advice Form

Courier services and specimen delivery

For NSW submissions, please contact the relevant Customer Service team for courier account details and to order consignment notes.

For submitters outside of NSW, Couriers can be contacted directly to make bookings and arrange collection of packages at the submitters own cost.

Commercial couriers may use either road or air transport and specimens should therefore be packed in accordance with International Air Transport Association (IATA) requirements. Most submission sent by veterinarians to the SVDL for testing are defined as “Biological Substance Category B” and must be packed according to the IATA packing instructions 650 (Biological Substance Category B). As requirements for transport can change, customers should consult with their transport agent to obtain current requirements.

Samples may also be hand delivered to the site during normal business hours (8.30am - 4.30pm).