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West Nile Virus

July 19, 2010

 

RE:  Availability of Eastern Equine Encephalitis and West Nile virus testing

 

Dear Vermont Veterinarian:

 

This summer, the Vermont Department of Health and the Vermont Agency of Agriculture, Food & Markets are beginning enhanced surveillance for the arboviruses Eastern Equine Encephalitis virus (EEEV) and West Nile virus (WNV). In previous years, surveillance was mostly limited to WNV and consisted of mosquito testing, bird testing, dead bird reporting, reports of human illness, and the occasional report of illness in animals.

 

As part of our increased efforts to detect EEEV, we are encouraging the testing of animals that are highly susceptible to the virus, including equids, camelids, and ratites. Diagnosing EEE in these species can be a sensitive indicator for the presence of this virus in our state. Because EEEV surveillance provides valuable information for public and animal health, the Department of Health and the Agency of Agriculture are offering testing of highly susceptible species, free of charge, now through November 15. Specimens that meet the criteria for testing for EEEV will also be tested for WNV.

 

EEEV has not been detected in Vermont, but the main mosquito vector, Culiseta melanura, is present in our state. In recent years, EEE has been diagnosed in horses in southeastern New Hampshire, southwestern and central Maine, Clinton County, New York and Quebec. EEEV has also been detected in emus and alpacas. Enhanced surveillance will help the Vermont Department of Health and the Agency of Agriculture determine the risk for infection in people and susceptible animal species.

 

Although EEEV is an uncommon cause of human illness, it can be a devastating disease. The mortality rate approaches 35 percent, and people who survive often have persistent neurologic deficits.

 

About EEEV in animals

EEEV is a mosquito-borne viral disease that causes a progressive neurologic condition in horses and other equids. Alpacas, llamas and emus are also known to be susceptible to illness. The mortality rate in horses is 75 to 90 percent. Clinical signs of EEEV in horses include fever, depression, loss of appetite, weakness, ataxia, chewing movements, head pressing, circling, “sawhorse” stance, paddling, seizures, irritability, excitability, blindness, and abnormal sensitivity to light and sound. Horses may die without showing any signs or symptoms.

 

However, the signs and symptoms are not unique to EEEV. Other conditions to consider include West Nile virus encephalitis, tetanus, rabies, equine herpesvirus-1, equine protozoal myeloencephalitis, and western or Venezuelan equine encephalitis.

 

In emus, infection typically results in a rapid onset of clinical signs, often resulting in death. Common manifestations include disseminated intravascular coagulation, severe hemorrhagic enterocolitis, and blood-tinged vomitus. It is interesting to note that emus develop high levels of viremia. Unlike horses and humans, they may not be dead-end hosts and may act as a reservoir for the virus. There is evidence that the vaccines available for horses will protect emus from infection with EEEV.

 

Tengelsen, LA et al., “Response to and efficacy of vaccination against eastern equine encephalomyelitis virus in emus” JAVMA Vol. 218, No. 9, 2001

Case finding:

Testing criteria:

Onset of illness: June 1st through October 31st (unless relevant travel history)

 

Species:

Equids

Camelids (ie. alpacas, llamas)

Ratites (ie. emus)

 

Clinical illness:

One or more of the following –

  • Attaxia or stumbling or uncoordination
  • Inability to stand
  • Acute paralysis or limb weakness
  • sudden d eath with no other diagnosis
  • Severe hemorhaggic enteritis (emus)

Note: All brain tissue samples from equids and camelids that are negative for rabies at the Vermont Department of Health Laboratory will automatically be sent for arboviral testing.

 

Procedure for submitting samples for laboratory testing:

Laboratory testing will be done by the Wadsworth Center, which is part of the New York State Department of Health in Albany, NY. Because testing of animals will be part of our surveillance system for EEEV and WNV, the Vermont Department of Health and Agency of Agriculture need to be informed of testing done through this program.

 

Animals that died or were euthanized:

  • Brain tissue is the preferred sample. Most of these animals will have to be tested for rabies first. Call State Public Health Veterinarian Robert Johnson, DVM, at 802-863-7240, as you normally would with suspect rabies in an animal.
  • Brain tissue samples collected for rabies testing can be used for arboviral testing as well. (Note: tissue samples should be refrigerated and kept cold during transport).
  • Brain tissue samples should be sent to the Vermont Health Department Laboratory with the rabies sample submission form.
  • If rabies is negative, the brain tissue sample will be sent to Wadsworth for testing for EEEV and WNV by viral isolation and PCR.

 

Animals that are alive:

  • Before submitting samples for arbovirus testing, please call the State Veterinarian’s office at 802-828-2421. If the testing criteria are met, please use the enclosed submission form to submit the sample to Wadsworth lab. The address is at the top of the form. In addition, please fax a copy of the completed sample submission form to the Vermont Agency of Agriculture at 802- 828-5983.
  • Serum samples
    • Submit ≥ 3 ml of serum. IgM and IgG testing for both EEEV and WNV will be done on this sample.
    • Serum should be collected within the first 14 days of illness.
    • Samples positive on the initial screening will be confirmed by PRNT.
    • Convalescent samples may be necessary and should be collected about 2 weeks later.
  • CSF
    • Submit ≥ 1 ml of CSF. IgM testing for both viruses will be done on this sample.

The following information must accompany the sample submission:

Date of onset of illness

Date of specimen collection

Address where animal is stabled/housed

Vaccination history

Travel history

Disease history

List of neurologic symptoms

 

Please remember that both WNV and EEE in animals are reportable diseases in Vermont. If you have any questions, please call the State Veterinarian’s office at 802-828-2421 or the Health Department’s Infectious Disease Epidemiology program at 802-863-7240.

 

For more information on arboviruses and mosquito control, please go to our websites: http://healthvermont.gov/prevent/wnv/wnv.aspx - or - http://www.vermontagriculture.com/ARMES/plantindustry/entomology/mosquito/index.html

 

Thank you for your help.

 

                  

 Kristin Haas, DVM                                             Robert Johnson, DVM

 State Veterinarian                                            State Public Health Veterinarian  

 Vermont Agency of Agriculture                       Vermont Department of Health

 

 

For Immediate Release: June 21, 2010

Media Contact: Communication Office

Vermont Department of Health

802-863-7281

BURLINGTON - Each year in Vermont, mosquitoes infected with West Nile virus feed on birds, and some birds become sick and can die. For the past 10 years, the Vermont Department of Health has conducted a statewide "Dead Bird Surveillance Program." Tracking the number and location of bird deaths, along with testing some birds for West Nile virus, helps to assess the risk for human infection from mosquito bites, and directs prevention efforts.

Again this year, report sightings of dead birds by calling the central dead bird reporting line at the Vermont Department of Health at 1-800-913-1139. Some of the birds will be tested for West Nile virus. The dead bird reporting line will remain active until the middle of October, when the mosquitoes begin to die off and the risk of disease transmission declines.

The West Nile virus season peaks in late summer and runs through October. The risk for infection with West Nile virus continues into late fall, or as long as mosquitoes remain active.

"Although human cases of West Nile virus infection are still rare in Vermont, we want everyone to be aware of the Health Department surveillance programs and to take precautions to avoid mosquito bites," said Erica Berl, an infectious disease epidemiologist with the Health Department, "For example, to reduce mosquitoes around your house, eliminate standing water where they might breed and drain areas where water can pool, such as rain gutters and wading pools."

Although Vermont's last reported human case of West Nile virus occurred in 2003, four positive birds were identified in 2009. Mosquitoes also tested positive last year, so the virus is still circulating in our state. In addition, the Health Department and the Vermont Agency of Agriculture, Food and Markets are on the lookout for

another mosquito-borne virus, Eastern Equine Encephalitis virus. This virus has not been detected in Vermont but has been found in neighboring states and Quebec.

Only one out of five people who are infected with the West Nile virus experience symptoms. The symptoms are most often mild and include fever, body aches, headache, nausea, vomiting and sometimes swollen lymph nodes or a rash. Fewer than 1 percent of people develop severe illness affecting the central nervous system. The severe symptoms can include high fever, headache, neck stiffness, disorientation, muscle weakness, numbness and paralysis.

The Department of Health is urging Vermonters to:

*        Wear long sleeves and pants and avoid outdoor activities at dusk and dawn when mosquitoes are active.

*        Reduce mosquito breeding habitats by getting rid of standing water; drain areas where water can pool such as rain gutters, wading pools and any other water-holding containers such as old tires.

*        Use effective mosquito repellents

*        Install or repair screens on windows and doors to keep mosquitoes out.

*        Horses are also susceptible to infection and should be vaccinated against the virus.

For more information on West Nile Virus visit healthvermont.gov.

 

August 27, 2009

Eastern Equine Encephalitis and West Nile virus

Message from Vermont State Veterinarian Dr. Kristin Haas and Vermont Assistant State Public Health Veterinarian Erica Berl

Dear Vermont Veterinarian:

The mosquitoes are biting, which means arbovirus season has begun. The Vermont Department of Health and the Vermont Agency of Agriculture are continuing surveillance for West Nile virus (WNV) in mosquitoes, humans and birds, and for Eastern Equine Encephalitis virus (EEEV) in mosquitoes and humans. Domestic animals, especially horses, can also be infected with these viruses. Detecting these viruses in animals is helpful for assessing the risk to the public and other animals. We encourage you to test animals that have clinically compatible illness and to report positive results to the State Veterinarian.

We are particularly interested in EEEV because it can cause devastating disease in humans and animals. Although EEEV has never been detected in Vermont, it has been found in nearby areas, and the main mosquito vector, Culiseta melanura, is present in our state. In recent years, EEE has been diagnosed in horses in New Hampshire, Maine, Clinton County, New York and Quebec. EEEV has also been detected in emus and alpacas. So far this year, an alpaca in New Hampshire and a horse in central Maine have died of EEE.

WNV has been detected in our state in almost every year since 2000. Eleven equine cases have been reported to us over that time, although activity has been low the past three years.

WNV should be considered in horses that develop neurologic symptoms without an alternative explanation. EEEV can cause severe neurologic symptoms or sudden death in horses, donkeys, llamas and alpacas. Emus are also susceptible to EEEV infection, but they usually present with a severe hemorrhagic gastroenteritis or sudden death.

The Vermont Department of Health and Agency of Agriculture can facilitate testing in some cases by sending brain tissue samples for arbovirus testing to Wadsworth Laboratory, which is part of the New York State Department of Health. Samples from horses, donkeys, alpacas and llamas that die or are euthanized with neurologic signs should first be tested for rabies. Those samples that are negative can then be forwarded to Wadsworth for arbovirus testing.

  

Please remember that both WNV and EEE in animals are reportable diseases in Vermont. To report animals diseases please call the State Veterinarian’s office at 802-828-2421. If you have any questions about arbovirus testing or arboviruses in general, please call the State Veterinarian’s office or the Health Department’s Infectious Disease Epidemiology program at 802-863-7240.

For more information on arboviruses and mosquito control, please go to our websites: http://healthvermont.gov/prevent/wnv/wnv.aspx - or - http://www.vermontagriculture.com/ARMES/plantindustry/entomology/mosquito/index.html

Thank you for your help.

Steps You Can Take To Avoid West Nile Virus

  • Wear long sleeved shirts and long pants whenever possible outdoors.
  • Limit the amount of time you spend outdoors at dawn and dusk since that is when mosquitoes are most active.
  • Use insect repellant that contains up to 30 percent DEET for adults and up to 10 percent DEET for children and apply sparingly. Be sure to follow the product directions. DEET can be harmful if used in large amounts or used incorrectly. Never use DEET on infants.
  • Regularly empty any outdoor containers that hold standing water including wading pools, trash cans, tires and empty flower pots. Turn them over or cover them when they are not being used.
  • Clean leaves and other debris out of clogged gutters.
  • Repair holes in screens and make sure they fit tightly to the window or door frame.

More information about West Nile virus, national and Vermont statistics, and others ways to protect yourself can be found on the Vermont Department of Health website: www.HealthyVermonters.com .

West Nile Virus and Horses

West Nile affects horses much more often than any other domestic animals. Many horses infected with West Nile do not develop any illness, but of horses that become ill about one-third die or need to be euthanized. Other livestock and poultry do not commonly show any illness if infected with West Nile.

Q. How do horses become infected with West Nile virus?
A. The same way humans become infected—by the bite of infectious mosquitoes. The mosquitoes become infected after feeding on an infected bird. Mosquitoes cannot get West Nile virus from an infected horse.

Q. Has West Nile virus caused severe illness or death in horses?
A. Following transmission by an infected mosquito, West Nile virus, may cause a mild transient self resolving fever or it may infect the brain causing inflammation or “encephalitis”. The vast majority of horses that are bitten by infected mosquitoes do not become ill, but those that develop severe encephalitis often die.

Q. Can I get infected with West Nile virus by caring for an infected horse?
A. West Nile virus is transmitted by infectious mosquitoes. The infected horse is not contagious to humans or to other horses. Normal infection control precautions should be followed when caring for a sick horse.

Q. Can a horse infected with West Nile virus infect horses in neighboring stalls?
A. No. There is no documented evidence that West Nile virus is transmitted between horses.

Q. My horse is vaccinated against Eastern Equine encephalitis, Western Equine encephalitis and Venezuelan Equine encephalitis. Will these vaccines protect my horse against West Nile virus infection?
A. No. These three viruses belong to another family of viruses for which there is no cross-protection.

Q. Can I vaccinate my horse against West Nile virus infection?
A. A conditionally licensed West Nile virus vaccine for horses is available. Contact your large animal veterinarian for more information.

Q. What is the treatment for a horse infected with West Nile virus? Should it be destroyed?
A. There is no reason to destroy a horse just because it has been infected with West Nile virus. Data suggest that most horses recover from the infection. Supportive care and time are all that most horses need to fully recover.

Q. How can I help protect myself and my family from West Nile Virus?
A. Horse owners should make sure that empty buckets and water troughs are not breeding sites for mosquitoes. Turn over buckets when they are not in use, and clean the water trough regularly. Make sure that faucets are turned off and do not drip.

The best way to protect you from West Nile virus, or any other mosquito-borne illness, is to reduce the number of mosquitoes around your home and neighborhood and to take personal precautions to avoid mosquito bites. These are some of the preventative steps that you can easily take:

  • Eliminate standing water where mosquitoes can breed. Check for items outside the home that collect water, such as cans, bottles, jars, buckets, old tires, drums and other containers.
  • Change water in flower vases, birdbaths, planters and animal watering pans at least twice a week.
  • Repair leaky pipes and outside faucets, and move air conditioner drain hoses frequently.
  • Avoid being bitten by mosquitoes when going outside at night by using insect repellent. Wear lightweight clothing that covers the arms and legs.

Q. Where can I get more information on horses and West Nile virus?
A. USDA’s Animal and Plant Health Inspection Service Web site at www.aphis.usda.gov/oa/wnv/.

Recent media reports have prompted many questions regarding West Nile virus (WNV) infection in species other than birds, horses, and humans. As an "emerging disease" in the United States, WNV has clinical and health effects on various animal species and populations that have yet to be described or fully reported. The following information is offered on the current knowledge of WNV infection in other species.

It is currently believed that any type of bird or mammal may be susceptible to WNV infection, but very few species appear to develop clinical illness due to infection. Since entering North America in 1999, WNV has been reported in thousands of birds, horses, and humans (over 2768 people and 146 deaths, as of Wed 9 Oct 2002). Before this year, WNV infection had been reported in several bat species, chipmunks, gray squirrels, striped skunks, a rabbit, and 3 cats. Laboratory trials had indicated that cats would become viremic and ill, but that dogs were relatively resistant to infection with WNV.

Serosurveys in New York following the 1999 outbreak revealed that 8-11 percent of dogs had antibody titers to WNV, but had not become ill. As WNV has moved across the country this summer, infection and illness have now been reported in a domestic sheep, a mountain goat, a dog, a 7-month-old wolf pup, a llama, and an alpaca. Serologically positive black bears and white-tailed deer have also been detected, but these animals did not develop clinical illness.

Some of the animals that became ill had another underlying health condition and/or a compromised immune system predisposing them to development of clinical disease. For instance, the one 8-year-old dog in Illinois was immune-compromised. From what is currently known, WNV does not appear to pose a significant health risk for species other than birds, horses, and humans. The extremely small number of cases in other species, the active surveillance conducted for the last 4 years, and reports from 42 states that have detected WNV suggest that most of these species are extremely resistant to developing clinical illness from infection. There is also no current evidence that any of these species are capable of serving as a reservoir for the virus.

It is likely more cases in other hosts will be found as WNV enters and becomes established in new areas. As additional information becomes
available, the relative health significance of WNV infection in these populations will become more clearly established.

Suggestions for protecting animals from the deadly West Nile Virus

The USDA is recommending that animal owners take several precautions to protect their animals from the West Nile virus. The following recommendations are based on current knowledge about the virus and the 1999 US outbreak.

Mosquito breeding sites:

Remove all potential sources of stagnant water where mosquitoes might breed.

Precautionary steps include the following:

  • Dispose of any water containers, including discarded tires.
  • Drill holes in the bottom of containers that are left outdoors
  • Clean clogged roof gutters annually.
  • Turn over plastic wading pools or wheelbarrows when not in use, and do not allow water to stagnate in birdbaths.
  • Ventilate ornamental pools or stock them with fish.
  • Clean and chlorinate swimming pools that are not in use.
  • Thoroughly clean livestock troughs monthly.

Insect repellents:
Use of insect repellents may be of some value in decreasing exposure of horses to adult mosquitoes. Repellents alone should not be relied on, however, to prevent mosquito exposure.

Screened housing:
Housing animals in structures with well-maintained insect screening can reduce exposure to adult mosquitoes. Be sure to eliminate mosquitoes from inside the structure first through the use of mosquito adulticides and fans.

Outdoor exposure:
The mosquitoes responsible for the transmission of the West Nile virus to horses and other mammalian species generally feed at dawn, dusk, and during the night. The USDA recommends caution when exposing animals to areas inhabited by mosquitoes during these times.

USDA's actions to protect agriculture:
The USDA-APHIS Veterinary Services has developed a diagnostic test for the West Nile virus and is on the lookout for virus activity along the Atlantic seaboard. The program surveillance investigates horses showing clinical signs of encephalitis, when other common causes such as rabies can be ruled out. APHIS' Wildlife Services program carries out wild bird specimen collection, initially focusing on East Coast states from Connecticut to Florida, for West Nile virus testing.