DOVER, Del. (October 26, 2023) – The Office of the State Veterinarian announced Delaware has had five confirmed cases and one suspected case of West Nile Virus (WNV) recently reported in Delaware horses. These are the first Delaware cases of WNV in horses in 2023, with the cases occurring between September 9 and October 16, 2023.

All of the recent cases involve horses that were not vaccinated, including:

• 1-year-old Standardbred mare, Kent County, confirmed case, recovered
• 3-year-old Standardbred mare, Kent County, suspected case, recovered
• 6-year-old Standardbred mare, Kent County, confirmed case, euthanized
• > 20-year-old Percheron mare, New Castle County, confirmed case, recovered
• 1-year-old Standardbred colt, Kent County, confirmed case, recovered
• 14-year-old Standardbred mare, Kent County, confirmed, outcome unknown

Signs of infection in horses include fever (although not always with WNV), anorexia, head pressing, depression or personality change, wobbling or staggering, weakness, blindness, convulsions, muscle spasms in the head and neck, or hind-limb weakness. If owners notice any of these signs in their horses, they should contact their veterinarian immediately.

Animal health professionals with formal training in diagnosing or recognizing animal diseases and pests of horses and livestock are required to report suspected or confirmed cases of WNV and EEE to the Office of the State Veterinarian within 24 hours. Examples of animal health professionals include, but are not limited to, veterinary medical professionals, diagnostic laboratorians, biomedical researchers, public health officials, animal health officials, trained technicians, zoo personnel, and wildlife personnel with such training.

WNV and Eastern Equine Encephalitis (EEE) are diseases transmitted to horses via the bites of mosquitoes. Humans can also be infected with WNV and EEE, but transmission requires a mosquito bite, and the virus cannot be directly transmitted between horses or between horses and people.

Most people infected with WNV do not develop symptoms, but about 20% can develop a mild illness, including fever, body and muscle aches, headache, nausea, vomiting, and rash symptoms. A small number of people can develop serious illness involving neurological problems, paralysis, and possibly death. The Division of Public Health Disease Prevention & Control Section reports that Delaware had four confirmed cases of neuroinvasive WNV this year.

The public is reminded to take precautions to avoid mosquito bites, including wearing light-colored clothing of long-sleeved shirts and long pants when outdoors in mosquito-prone areas; applying insect repellent containing 10 to 30% diethyltoluamide (DEET) in accordance with label instructions; and avoiding mosquito-infested areas and at times of peak mosquito activity around dusk, dawn and at night.

With the first hard freeze, the mosquito season should come to a close; however, the State Veterinarian is urging horse owners to contact their veterinarians to ensure they add the WNV and EEE vaccines to their annual vaccination schedule for 2024 to help protect their horses and other equines. Neither disease has a specific drug treatment, and EEE infections in horses are fatal in 70 to 90 percent of cases and WNV in 30 percent of cases.

Horse owners can take several additional steps in the barn and around the farm to help protect horses from mosquito bites. Horses should be kept inside during dawn and dusk, peak hours for mosquito activity. Topical insect repellents labeled for use on horses may be applied. The wind generated by fans installed in horse stalls can also help deter mosquitoes. Old tires and containers should be disposed of, and standing water should be eliminated. Water troughs or buckets should be emptied, cleaned, and refilled every 2-3 days, if possible, to remove any mosquito eggs or larvae.

For more information about WNV or EEE:

• To report suspected cases of human West Nile Virus, contact the DPH Office of Infectious Disease Epidemiology (OIDE) at 302-744-4990 during normal business hours from 8 a.m. – 4:30 p.m., Monday – Friday; 1-888-295-5196 outside of normal business hours; fax: 302-622-4194; or email reportdisease@delaware.gov.
• Animal health questions should be directed to the Delaware Department of Agriculture at 302-698-4500. Ask for the Poultry and Animal Health Section.
• Questions about the state’s mosquito control program or mosquito biology should be directed to the Delaware Department of Natural Resources and Environmental Control’s Mosquito Control Section at 302-739-9917.

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DOVER, DE (Aug. 31, 2022) – The Division of Public Health (DPH) is announcing this year’s first human case of West Nile Virus (WNV), in a 78-year-old Sussex County man. West Nile Virus is a mosquito-borne illness that can cause serious health problems.   

In addition to the first human WNV case, there also have been confirmed cases in a horse in New Castle County, and in 19 sentinel chickens in outdoor-caged and humanely tended stations maintained throughout the state by the Department of Natural Resources and Environmental Control (DNREC).  Delawareans should be aware that mosquitoes that cause WNV bite primarily during the evening and morning hours; or dusk and dawn. However, mosquitoes that cause other diseases such as chikungunya, dengue fever, and Zika can bite during the day. It is important to protect yourself by wearing insect repellent whenever you go outdoors. 

WNV is transmitted by mosquitoes, generally in summer and fall, with a peak period for disease transmission from mid-August to mid-October. Nearly 80 percent of people infected with WNV will not become ill. Less than 20 percent of those infected with the virus will develop mild symptoms such as fever, headache, body aches, a skin rash on the chest or back, and swollen lymph glands. Approximately one in 150 people infected will develop severe infection which may include headache, high fever, stiff neck, tremors or convulsions, muscle weakness, encephalitis or meningitis, all possibly leading to hospitalization and very rarely death. The elderly and those with weakened immune systems are most at risk to contract WNV from mosquitoes. Anyone who experiences any of these severe symptoms should immediately seek medical assistance.  

To avoid mosquito bites and reduce the risk of infection, individuals should: 

• Use Environmental Protection Agency (EPA)-registered insect repellents. Follow the manufacturer’s instructions for reapplication times. 
• If using sunscreen, apply it first and insect repellent second. 
• Adults taking precaution with children against biting mosquitoes should spray insect repellent onto their hands and then apply it to the child’s face. Do not apply insect repellent onto a child’s hands, eyes, mouth, or on cuts or irritated skin. 
• Do not use insect repellent on babies younger than two months of age. 
• When outside during periods of mosquito activity, wear light-colored long-sleeved shirts and long pants. 
• Dress children in clothing that covers arms and legs. 
• Consider using mosquito netting, which offers protection to the face and neck and also protects infants in carriages, strollers and playpens.

• Use permethrin (an insecticide) to treat clothing and gear (such as boots, pants, socks, and tents), but do not apply to the skin. 
• Prevent mosquitoes from entering the house by using screens and tightly sealed windows and doorways.  

DNREC’s Mosquito Control section announced WNV in sentinel chickens for the first time in July 2021. Mosquito-transmitted virus detections in DNREC’s sentinel chickens are unrelated to Delaware’s poultry industry. The possibility of contracting mosquito-transmitted diseases, including WNV and Eastern Equine Encephalitis (EEE), will continue until colder autumn temperatures in mid-October or later.  

• To report suspected cases of human WNV, call the DPH Office of Infectious Disease Epidemiology at 1-888-295-5156. 
• For more information about mosquitoes and mosquito-borne illnesses, use the following resources: 

• • For mosquito biology/ecology and control, contact the DNREC Mosquito Control section office in Dover at 302-739-9917. 
  • For requests for mosquito relief in upstate areas from Dover north, contact Mosquito Control’s Glasgow field office at 302-836-2555. 
  • For requests for mosquito relief in downstate areas south of Dover, contact Mosquito Control’s Milford field office at 302-422-1512. 
• Contact the Delaware Department of Agriculture’s Poultry and Animal Health Section for animal health questions at 302-698-4500. 
• To report suspected cases of human WNV, call the DPH Office of Infectious Disease Epidemiology toll-free at 1-888-295-5156. 

For more information on West Nile Virus or Eastern Equine Encephalitis, visit https://dhss.delaware.gov/dhss/dph/epi/wnv.html.

For more information on what you can do to prevent West Nile Virus, visit the Centers For Disease Control and Prevention’s website, www.cdc.gov/westnile/prevention/index.html.

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The Delaware Division of Public Health (DPH), a division of the Delaware Department of Health and Social Services, is a nationally accredited public health agency recognized by the Public Health Accreditation Board for its outstanding dedication to driving change through innovation. DPH is committed to improving the quality of the lives of Delaware’s citizens by promoting health and well-being, fostering self-sufficiency, and protecting vulnerable populations. 

Anyone who is deaf, hard of hearing, Deaf-Blind, or speech-disabled can contact DPH by first dialing 711 using specialized devices (i.e., TTY, TeleBraille, voice devices). The 711 service is free; to learn more about how it works, visit delawarerelay.com.

About DNREC

The Delaware Department of Natural Resources and Environmental Control protects and manages the state’s natural resources, protects public health, provides outdoor recreational opportunities, and educates Delawareans about the environment. The DNREC Division of Fish and Wildlife conserves and manages Delaware’s fish and wildlife and their habitats, and provides fishing, hunting, wildlife viewing and boating access on nearly 68,000 acres of public land. For more information, visit the website and connect with @DelawareDNREC on Facebook, Twitter or LinkedIn.  

Media contacts: Michael Globetti, michael.globetti@delaware.gov; Joanna Wilson, joanna.wilson@delaware.gov

DOVER – DNREC’s Mosquito Control Section within the Division of Fish & Wildlife is scheduled to begin its annual spring woodland pool spraying on Tuesday, March 19 to control immature aquatic mosquito larvae in wooded wetlands near select populated areas. Weather permitting, spraying will begin in southern Sussex County and expand into Kent and New Castle counties in the weeks ahead. In most years, about 10,000 wooded acres that would produce large numbers of early-season mosquitoes are strategically sprayed by helicopter using insecticides to control mosquito larvae.

Areas to be sprayed are determined by the location and size of woodland pools, which can vary from year to year based on precipitation levels from the past autumn, winter, and early spring. High precipitation levels have resulted in more extensive and above normal woodland pool habitat this year. It is not possible for logistical or budgetary reasons to spray all 100,000 or more acres of Delaware’s woodland mosquito-producing habitats, so wet woodlands near the state’s most populated areas are targeted to provide the best return-on-investment in providing mosquito relief to the most people.

Over the next several weeks, Mosquito Control will apply the bacterially-derived insecticide Bti, which, as with all registered insecticides used by Delaware Mosquito Control, the U.S. Environmental Protection Agency has determined can be applied in accordance with EPA-approved product label instructions as required by federal law without posing unreasonable risks to human health, wildlife, or the environment.

Aerial spraying of woodland pools must be completed before the forest canopy fills in, usually around mid-April, because foliage prevents the insecticide from reaching woodland pools and other wet spots on the forest floor harboring mosquito larvae. Control of larval stages of early-season woodland pool mosquitoes helps limit intolerable numbers of biting adult mosquitoes emerging in late April and lasting through mid-June that would affect quality of life and human health within one to two miles of their woodland pool origins.

The spring woodland spraying campaign for mosquito larvae marks the beginning of Delaware’s annual mosquito control season, which in most years continues until mid-October or early November, depending upon when the first killing freeze occurs. Control activities will be expanded starting in late April to adult and larval saltmarsh mosquitoes, other freshwater mosquitoes, and urban and suburban container-breeding mosquitoes, to include control of adult woodland pool mosquitoes that still emerge.

Residents are strongly encouraged to help reduce mosquito-producing sites by doing some outdoor “spring cleaning” by emptying or eliminating backyard artificial containers that hold water and produce mosquitoes later in the spring, such as the Asian tiger mosquito known to carry illnesses including West Nile virus. Backyard mosquito-producing standing water can be reduced by cleaning clogged rain gutters and downspout extenders, keeping fresh water in birdbaths, draining abandoned swimming pools, and preventing or emptying standing water from containers such as scrap tires, cans, buckets, flower pot saucers, unused water cisterns, children’s toys, upright wheelbarrows, uncovered trash cans, and depressions in tarps covering boats or other objects stored outside.

The public can learn about locations and times of spraying for mosquitoes via daily radio announcements, or by calling 800-338-8181 toll-free. Interested parties also may subscribe to receive email, text, or phone message spray announcements for their area by signing up on Mosquito Control’s Spray Zone Notification System at http://de.gov/mosquitospray.

To request localized mosquito control, please call Mosquito Control’s field offices:

• Glasgow Office, 302-836-2555, serving New Castle County and the northern half of Kent County, including Dover.
• Milford Office, 302-422-1512, serving the southern half of Kent County south of Dover and all of Sussex County.

For more information about Delaware’s Mosquito Control program, please call the Dover office at 302-739-9917.

Follow the Division of Fish & Wildlife on Facebook, https://www.facebook.com/DelawareFishWildlife.

Contact: Joanna Wilson, DNREC Public Affairs, 302-739-9902

Vol. 49, No. 57

DOVER, Del. – The Office of the State Veterinarian announced today Delaware’s fourth and fifth cases of West Nile Virus (WNV) found in horses in 2018. Three previous cases of WNV in horses were reported in 2018, two in August and one in September.

The fourth case of WNV confirmed in a Delaware horse occurred in a 1-year-old Standardbred mare residing in Kent County. The horse received veterinary care for loss of control of limbs and buckling over in the front limbs which began on October 11. Clinical signs progressed to inability to rise, muscle twitching, and stupor. The horse was euthanized on October 15 due to the severity of its illness. She had not been vaccinated for WNV. New Bolton Center Clinical Pathology Laboratory reported positive WNV results on October 19.

The fifth infected horse is a 6-year-old Belgian mare residing in Kent County that was evaluated by a veterinarian for whole body stiffness, acting sore, and abnormal mentation consisting of aggression with a date of onset of October 12, 2018. Diagnostic specimens were submitted to the National Veterinary Services Laboratory, which confirmed the diagnosis on October 23. The mare had never been previously vaccinated against WNV. She was treated supportively and her condition was improving as of October 18.

West Nile Virus and Eastern Equine Encephalitis (EEE) are diseases transmitted to horses via the bites of mosquitoes. Humans can also be infected with WNV and EEE, but transmission requires a mosquito bite and the virus cannot be directly transmitted between horses, or between horses and people. Signs of infection in horses include fever (although not always with WNV), anorexia, head pressing, depression or personality change, wobbling or staggering, weakness, blindness, convulsions, muscle spasms in the head and neck, or hind-limb weakness. If owners notice any of these signs in their horses, they should contact their veterinarian immediately. Two cases of WNV were confirmed in Delaware horses in 2017.

The Department of Natural Resources and Environmental Control’s (DNREC) Mosquito Control Section has seen an increase of WNV found in wild birds and sentinel chickens this year throughout the state. There have been a total of eight EEE-positive sentinel chickens and WNV has been detected in 66 sentinel chickens and 37 wild birds. So far in Delaware in 2018, eight cases of WNV have been found in humans.

Even though we are nearing the end of the mosquito season, the State Veterinarian urges horse owners to contact their veterinarians as soon as possible to have horses and other equines vaccinated against WNV and EEE. Neither disease has a specific drug treatment, and EEE infections in horses are fatal in 70 to 90 percent of cases, and WNV in 30 percent of cases.

Horse owners can take several additional steps in the barn and around the farm to help protect horses from mosquito bites. Horses should be kept inside during dawn and dusk, which are peak hours for mosquito activity. Topical insect repellents labeled for use on horses may be applied. The wind generated by fans installed in horse stalls can also help deter mosquitoes. Old tires and containers should be disposed of and standing water eliminated. Water troughs or buckets should be emptied, cleaned, and refilled every 2-3 days if possible to remove any mosquito eggs or larvae.

For more information about WNV or EEE:
• To report suspected cases of human West Nile Virus, call the DPH Office of Infectious Disease Epidemiology at 888-295-5196.
• Animal health questions should be directed to the Delaware Department of Agriculture at 800-282-8685 (Delaware only) or 302-698-4500. Ask for the Poultry and Animal Health Section.
• Questions about the state’s mosquito control program or mosquito biology should be directed to the Delaware Department of Natural Resources and Environmental Control’s Mosquito Control Section at 302-739-9917.

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Media Contact: Stacey Hofmann, 302-698-4500, stacey.hofmann@delaware.gov

Continued awareness and precautions encouraged

DOVER (Sept. 20, 2018) – The recent detection of Eastern Equine Encephalitis (EEE) in sentinel chickens monitored for mosquito-borne diseases by the DNREC Division of Fish & Wildlife’s Mosquito Control Section reinforces the fact that mosquitoes remain active and that precautions should continue to be taken to avoid mosquitoes whose bites could transmit EEE and other mosquito-borne diseases.

Test results reported to the Mosquito Control Section last week by the Delaware Division of Public Health Laboratory indicated EEE-positive chickens from three additional stations of the 20 stations monitored by the Mosquito Control Section throughout the state. Two of these positive stations were in New Castle County and one in Sussex County, increasing the total number of EEE-positive sentinel chicken stations this year to six: three in New Castle County and three in Sussex County. This higher-than-average detection rate for EEE suggests increased EEE activity and distribution in Delaware.

Eastern Equine Encephalitis is a rare, but potentially fatal, viral disease spread by mosquitoes, and is considered one of the more serious mosquito-borne illnesses. Although there is an EEE vaccine for horses, an EEE vaccine is not available for people. No human cases of EEE have been reported to date this year in Delaware.

Anyone in an area where the virus is circulating can be infected with EEE. The risk is highest for people exposed to high numbers of mosquito bites, including people who live in, visit, or work outside in areas with high mosquito populations where there is greater exposure to potentially infected mosquitoes. Those over age 50 and under age 15 appear to be at greatest risk for developing severe disease when infected with EEE.

While most patients infected with EEE have no apparent illness, severe cases of EEE (involving encephalitis, an inflammation of the brain) begin with the sudden onset of headache, high fever, chills, and vomiting. The illness may then progress into disorientation, seizures, or coma. Symptoms of EEE often appear four to 10 days after being bitten by an infected mosquito. Approximately 33 percent of EEE cases lead to death, and many of those who do survive experience significant brain damage. There is no specific treatment for EEE; care is based on symptoms. If you think you or a family member may have contracted EEE, it is important to consult your health care provider for proper diagnosis.

In response to DNREC’s recent EEE detections, along with ongoing West Nile virus activity, the Mosquito Control Section will increase mosquito population surveillance in areas where these detections have occurred and take mosquito control actions as warranted to include possible aerial spraying and/or fogging with a spray truck. However, the best protection to lessen the chance of contracting a mosquito-borne disease is to avoid mosquito bites by:

• Properly using insect repellent containing DEET whenever outdoors;
• Covering up exposed skin as much as possible by wearing long-sleeved shirts and pants; and
• Avoiding known high mosquito population areas or being outside during times of peak mosquito activity, typically dawn and dusk.

In addition to avoiding mosquito bites, the Mosquito Control Section advises residents to also reduce mosquito breeding habitat on their individual properties and communities/neighborhoods by draining or removing items that collect water, such as discarded buckets or containers, uncovered trash cans, stagnant birdbaths, unprotected rain barrels or cisterns, old tires, upright wheelbarrows, flower pot liners, depressions in tarps covering boats, clogged rain gutters, corrugated downspout extenders and unused swimming pools.

The Mosquito Control Section also encourages residents to report intolerable numbers of biting mosquitoes by calling the numbers below between 8 a.m. and 4 p.m. Monday through Friday. Callers after business hours or during weekends or holidays should leave their name, phone number, address and a brief message.

• Glasgow Office, serving New Castle County and northern Kent County including the Dover area: 302-836-2555
• Milford Office, serving Sussex and southern Kent counties: 302-422-1512

For more information about:

• Mosquito biology/ecology and control – Contact the Mosquito Control Section’s Dover office at 302-739-9917.
• Reporting WNV-suspect wild birds, or for requests for mosquito relief – For upstate areas from Dover north, contact Mosquito Control’s Glasgow field office at 302-836-2555; for downstate areas south of Dover, contact Mosquito Control’s Milford field office at 302-422-1512.
• WNV or EEE in humans and related medical issues – Contact the Delaware Division of Public Health at 888-295-5156.
• Animal health questions should be directed to the Delaware Department of Agriculture at 800-282-8685 (Delaware only) or 302-698-4500. Ask for the Poultry and Animal Health Section.
• For more information on West Nile Virus or Eastern equine encephalitis – Visit the CDC website, www.cdc.gov/ncidod/dvbid/westnile/index.htm.

Contact: Joanna Wilson, DNREC Public Affairs Office, 302-739-9902

Vol. 48, No. 253