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.

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

Click on + in the tables below for sampling requirements and additional test information

Code	Name	Samples required	Species	Turnaround time	Price (excl. GST)	Notes	Test days
HIST_HE1	Histopathology – Preparation & Examination	Fixed Tissues- General Fresh tissues immediately placed in formalin Tissue pieces should not be greater than 1cm cubed to ensure proper fixation Submit fixed in neutral buffered formalin at a 10:1 ratio of formalin: tissue Fixed Tissues- Nervous tissues Submission of whole brain is required to ensure preservation of TSE target sites submit fixed in neutral buffered formalin at a ratio of 10:1 formalin: tissue Brains submitted for Nervous tissues are processed once a week, separate to general tissues to ensure consistent and reliable results. Urgent cases can be processed out of cycle if clearly marked on the Submission Form however this may reduce the quality of the brain histology results, so should only be requested in extremely urgent cases. Fresh Tissues Fresh tissues can be submitted following necropsy The quality of the tissues will be reduced due to the effects of autolysis so ideally fixed tissue should be submitted in neutral buffered formalin at a ratio of 10:1 formalin: tissue	All species	Up to 10D	$84.95	D (number of working days) and W (number of weeks). Test TAT does not include weekends and public holidays.	Monday - Friday
WNV_B_ABEL	West Nile Virus Blocking ELISA*	Clotted blood (Red top) 10ml clotted blood collected in a red top tube Submit chilled Cerebrospinal fluid (CSF) 5ml sterile vial or 10ml red top tube. Submitted chilled	Equine, other susceptible species	7-10D	$15.55	* Denotes analyses not covered by the NATA scope of accreditation. D (number of working days) and W (number of weeks). Test TAT does not include weekends and public holidays. NOTE: Collection 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.	According to demand
WNV_ABEL_M	West Nile Virus IgM ELISA	Clotted blood (Red top) 10ml clotted blood collected in a red top tube Submit chilled Cerebrospinal fluid (CSF) 5ml sterile vial or 10ml red top tube. Submitted chilled.	Equine	7-10D	$30.65	D (number of working days) and W (number of weeks). Test TAT does not include weekends and public holidays. Note: The WNV IgM ELISA is only suitable for equine samples only 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.	According to demand
WNV_PCR	West Nile Virus Real–time PCR*	Fresh Tissue: Brain stem Submit brain cut in half longitudinally to ensure that all representative areas are available for virus detection. Submitted chilled Cerebrospinal fluid (CSF) 5ml sterile vial or 10ml red top tube. Submitted chilled.	Equine	2-3D	$109.35	* Denotes analyses not covered by the NATA scope of accreditation. D (number of working days) and W (number of weeks). Test TAT does not include weekends and public holidays.	According to demand

Additional Histopathology Test & Specimen Requirements

Sample Type	Sample Description	Specimen Requirements	Test Turnaround Time	Additional Information
Fixed tissue	Brain and upper cervical spinal cord - in neutral buffered formalin	10:1 ratio, fixed. WNV is usually only detected in the brain stem and upper cervical spinal cord	Up to 2W for brain Up to 5D for other	WNV is usually only detected in the brain stem and upper cervical spinal cord

Note

The risk of Hendra virus should be considered prior to tissue collection

Additional Information

WNV Fact Sheet

West Nile virus in Australia (Primefact)

Customer Service

Contact Customer Service for enquiries relating to testing and results, quotations and pricing, couriers, sample submission and invoicing.

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CONTACT DETAILS
Phone	1800 675 623
Email	laboratory.services@dpird.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

Quotations

For Animal export, Plant health or Veterinary quotations, please complete the online quotation request

Submission Forms

Veterinary Specimen Advice Form

Please Note: These documents are not fully web accessible, please contact Customer Service (laboratory.services@dpird.nsw.gov.au) for more information.

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 APHL 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).

Sample Type	Laboratory	Street Address
Animal (including aquatic animals)	NSW Animal and Plant Health Laboratories (APHL)	EMAI, Woodbridge Road, Menangle NSW 2568