Department of Agriculture
West Nile Virus Information

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New Jersey Department of Agriculture
Division of Animal Health

2001 Preview, 2000 Review

Nancy E. Halpern, D.V.M.
PO Box 330
Trenton, New Jersey 08625
Fax 609-777-8395
May 2001

New Jersey's West Nile Virus Action Plan

In August and September 1999, WNV was recognized in the Western Hemisphere for the first time when it caused an unprecedented die-off of crows, an epidemic of human encephalitis and meningitis in the New York City metropolitan area, and an epidemic of equine encephalitis in the Riverhead area of Long Island. Intensive surveillance throughout the region estimated thousands of avian cases, fatally affecting mostly crows, 62 human cases including seven deaths identified in New York, and 25 equine cases on Long Island with nine deaths. Subsequent serological testing in asymptomatic humans age five or older demonstrated that the prevalence of WNV infection was approximately 2.6% in northern Queens (population 46,220). Testing of horses in New York has not been as extensive, but has demonstrated the number of asymptomatically infected horses exceeds that of those showing clinical signs when infected.

Significantly, despite the identification of infected crows in many NJ counties, the virus was only isolated from two mosquito pools in Hudson County during the 1999 New York outbreak. Seventy-three (45%) of 161 dead crows collected in NJ in September and October tested positive for WNV. No human or equine cases were identified in New Jersey. Forty-eight suspect human cases were found to be negative by the CDC and serological testing of 100 equine blood samples submitted to the Division's Animal Health Lab during the outbreak demonstrated no evidence of WNV infection. The only mammal affected by the virus in NJ was a juvenile stray kitten living in a mosquito-rich storm drain.

Since the outbreak of 1999, New Jersey's Departments of Agriculture, Health and Senior Services, Environmental Protection and the Rutgers University Mosquito Research and Control Unit have remained actively involved in plans to prevent or control the virus from re-entering or spreading throughout our state. Although there is evidence that the virus over wintered in some mosquitoes in New York, this does not mean, definitively, that the virus will become a problem for us, in New Jersey. The virus will first have to replicate, then circulate and become amplified in mosquitoes and birds before it poses an animal or public health concern. New Jersey's greatest asset is it's ongoing mosquito control network and arbovirus surveillance programs that have been maintained throughout the years, principally to keep mosquito populations low and identify and control mosquitoes carrying Eastern Equine Encephalitis. This year, as described below, these programs will be greatly enhanced throughout the state to provide New Jersey's human and animal residents maximum protection against infection from this virus.

Mosquito surveillance and control will be NJ's first line of defense and will be targeted to prevent virus amplification from occurring by eliminating mosquitoes in the environment before they become a threat. Surveillance will be enhanced by the utilization of sentinel chicken flocks placed strategically in each county and monitored for presence of the antibody; collection, antibody testing and release of sparrows and starlings; the use of crow morbidity/mortality and testing as additional surveillance. Physicians and veterinarians will be partnering with government agencies and departments to help educate and inform the public, identify any suspicious cases, and assist in the collection and submission of specimens for laboratory diagnosis.

Mosquito Surveillance and Control

Responsibilities of County Mosquito Agencies:
Mosquito surveillance:larval and adult populations
Source reduction:manage larval habitats
water management
advise individual property owners
Chemical control: larvicides
Biological control:predatory fish

Individual property owners, farmers, stable and show managers and racetrack personnel are encouraged to eliminate sources of standing water in their environment. County Mosquito Control Agencies should be contacted for assistance in identifying and eliminating these potential mosquito-breeding habitats.

Avian Surveillance

Sentinel Chickens: Each county will have at least one chicken flock, placed strategically, for surveillance of the virus through biweekly blood testing for presence of antibody. Blood will be tested at the NJ Department of Agriculture's Animal Health Lab.

Starlings/Sparrows: Areas will be targeted by the Rutgers Mosquito Research and Control Unit for capture, WNV testing and release of these avian species who may serve as the intermediate reservoir of the virus. The Animal Health Laboratory plans to run serology tests for these specimens.

Crow Morbidity/Mortality: Local Health Departments (LHD) will receive reports of crow deaths, or of crows with neurologic signs from the public and fill in a WNV Crow Death/Illness Report (see attached). These reports should be faxed to the Infectious and Zoonotic Disease Program, DHSS by health officers. Crows that have died and are in suitable condition will be submitted for testing. Laboratory results will be provided to the local health departments, Office of Mosquito Control Commissions and County Mosquito Control Agencies.

Wildlife: Report any neurologic signs/mortality involving hawks or falcons to your local health officer. They will obtain any necessary information and direct you to send the bird, if needed.

Equine Surveillance

The Animal Health Lab will select and store a portion of all equine serum samples submitted for Coggins tests beginning in May 2000. These samples will be tested for the presence of West Nile antibodies if:

  1. One mosquito pool is positive in the same county, or
  2. At least 4 West Nile positive crows have died in the county during 2000, or
  3. The sentinel chicken flock for that county seroconverts, or
  4. One mammal, determined to be a resident for that county either demonstrates recent infection and/or becomes clinically ill from infection, or
  5. After November 31, 2000.

Sample selection: Up to 50 samples will be saved from each county, targeting horses residing within a 5-10 mile radius of the equine facilities in that county utilized for competitions. If no such facility exists in a county for that purpose, samples will be saved randomly.

If no West Nile virus activity occurs in NJ during 2000, the Division may decide not to test the banked samples. However, if testing occurs and positive serology is identified, the Division, in coordination with private practitioners and the USDA/APHIS, may conduct subsequent epidemiological testing and investigation. These positive results will remain confidential except for the notification required by the NJ Mosquito Commission, which allows them to increase surveillance and control measures upon receipt of this information.

Testing of Human Specimens

Physicians and other medical care providers will be advised of the human testing protocol through regular notices sent through the Chief Executive Officer, Emergency Department, and Infection Control Practitioner of all NJ acute care hospitals. This information will also be posted on the NJDHSS web site.

Testing of Animal Specimens

Veterinarians will be essential to the Department of Agriculture for the identification of suspect cases, particularly in equine patients. We will assist you in every way we can.

Any neurological case should be handled with caution since the clinical signs of arboviral encephalitis may be indistinguishable from those of rabies.
Consider the following equine cases suspect: any case which exhibits anorexia, depression or listlessness plus any three of the following signs: weakness of hind limbs, flaccid paralysis of the lower lip, impaired vision, ataxia, head pressing, aimless wandering, convulsions, inability to swallow, circling, hyperexcitability, paresis, coma, death.

  1. Notification Notify the Division of Animal Health immediately 609-292-3965. Equine encephalitis is a reportable disease in NJ and must be reported to the Division within 48 hours.

  2. Data collection When reporting a suspect case and/or sending in any samples, the following information is essential:
    Owner name, address and phone number
    Patient information, signalment, travel history, clinical signs and onset
    Patient location
    Vaccination history (specifically Eastern/Western Equine
    Encephalitis and Rabies: there is no vaccine available for West Nile Virus)
    Date of most recent negative Coggins test

  3. Sample Submission
    1. Antemortem Sample Collection and Submission
      Collect two serum samples in 10 ml red top tubes (smaller volume for avian samples).

    2. Postmortem Sample Collection and Submission
      Submit head or brain on ice (not frozen) for mammalian species. Submit entire carcass of agricultural avian specimens. If these procedures cannot be performed on site, inform the carcass removal company and the Division so that the required specimens are not discarded!

      The specimens will be tested for all relevant equine encephalitis viruses, including rabies and WNV. The Animal Health Lab will also consider requests for dog or cat testing.

Recommendations to minimize the risk of West Nile Virus infection

For horse owners, managers and trainers

Eliminate the mosquitos' habitats:
Remove potential water collection sites or maintain in clean condition. Potential sites include:

Discarded tires
Clogged gutters and drains
Storm drains
Water troughs: traditional or automatic
Water/feed buckets
Wash stall drains
Stagnant ponds
Unwashed birdbaths
Plastic wading pools
Unused swimming pools
Consult with your County Mosquito Agency
Request a site visit to:
Identify areas of concern
Get suggestions for clean-up/treatment
Identify possible sites for mosquito collection and testing
Concentrate on the recommendations above instead of using methods which are minimally effective mosquito control measures: e.g., fly sheets and masks; repellents for long term control; fly misters; bug zappers.

Contact your veterinarian and request a farm visit if your horse is exhibiting any of the following clinical signs:

anorexia (off feed)
depression or listlessness
weakness of hind limbs
flaccid paralysis of the lower lip (droopy lip)
impaired vision
ataxia (difficulty moving or standing correctly)
head pressing
aimless wandering
inability to swallow
paresis (paralysis, complete or partial)

Immediate intervention may save your horse's life! Don't hesitate; call your vet!

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