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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The Delaware Public Health Laboratory (DPHL) has identified this year’s first human cases of West Nile Virus (WNV) in three men 50 years of age and older, all of whom reside in New Castle County. All three individuals who contracted WNV were hospitalized due to infection from the mosquito-borne illness. At this time, it appears that each WNV victim is likely to have contracted the disease locally, but a public health investigation is ongoing, the Delaware Division of Public Health (DPH) announced today.  

In response to the human WNV cases discovered this month, the DPH and Delaware Department of Natural Resources and Environmental Control (DNREC) will increase mosquito population surveillance efforts in the vicinity of the infected individuals’ residences. Dependent on further findings, DNREC’s Mosquito Control Section in partnership with DPH may also conduct local control operations to try and prevent further WNV human transmissions. The agencies also note that the occurrence of the state’s three human cases coincides with an increase in WNV activity in the Mosquito Control Section’s sentinel chicken monitoring program, with the uptick in infected chickens typical for this time of year.

WNV is a mosquito-borne illness that can cause serious health problems. WNV is transmitted by mosquitoes, generally in summer and fall, with a peak period for disease transmissions from mid-August to mid-October. Nearly 80 percent or four in five people infected with WNV will not become ill. While only a little less than 20 percent of those infected with the virus will develop West Nile fever with mild symptoms (fever, headache, body aches, a skin rash on the chest or back and swollen lymph glands), one in 150 people infected will develop severe infection (West Nile encephalitis or meningitis).   

Symptoms of severe WNV infection include headache, high fever, stiff neck, and/or tremors and muscle weakness. The elderly and those with weakened immune systems are most at risk. Anyone who experiences any of these severe symptoms should seek medical help immediately. Symptoms may progress to stupor, disorientation, coma, convulsions, paralysis and possibly death.  

The mosquitoes that cause WNV bite primarily from dusk (evening) to dawn (morning). However, other mosquitoes that transmit diseases such as chikungunya, dengue fever and Zika can bite during the day. Applying insect repellent for personal protection is important whenever going outdoors. Wearing light-colored, long-sleeved shirts and pants is also recommended as a deterrent against mosquito bites. DPH and the DNREC Mosquito Control Section also advise reducing outdoor activities that can cause heavy breathing or excessive perspiration, not wearing perfumes or colognes, and using mosquito repellents that may contain the ingredients DEET or Picaridin in accordance with product label instructions. Additionally, Delaware residents and landowners should eliminate an unneeded standing water on their property that might exist for four or more consecutive days and that acts as mosquito breeding habitat.

To report suspected cases of human WNV, call the Division of Public Health Office of Infectious Disease Epidemiology toll-free at 888-295-5156.   

For information on mosquito control operations in Delaware, including contact information to request residential control service for biting mosquitoes, visit https://dnrec.alpha.delaware.gov/fish-wildlife/mosquito-control/. 

For more information on West Nile Virus, 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. 

No Human Cases of WNV Reported to Date in State; Equine
Owners Urged by Department of Agriculture to Vaccinate Animals

West Nile Virus (WNV) has been detected in Delaware the first time for 2023 in a sentinel chicken, the Delaware Department of Natural Resources and Environmental Control announced today. This initial finding was from a sentinel chicken station near Wilmington sampled on July 31 by the DNREC Mosquito Control Section, and then tested and reported virus positive by the Delaware Public Health Laboratory on Aug. 4. While there have been no reported WNV cases in humans this year in the state, Delawareans are reminded that the possibility of contracting mosquito-transmitted diseases, including WNV and eastern equine encephalitis (EEE), will continue until colder autumn temperatures arrive in mid-October or later.

Blood samples are collected by the DNREC Mosquito Control section each week from early July into October from the state’s outdoor-caged sentinel chickens that are humanely housed and handled at 20 monitoring stations statewide. The blood samples are tested for WNV and EEE antibodies by the Delaware Public Health Laboratory. Sentinel chickens bitten by mosquitoes carrying WNV or EEE develop antibodies to these diseases but are otherwise unaffected. Mosquitoes can transmit both WNV and EEE to humans and horses.

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 one confirmed case of invasive WNV in 2022, and none so far this year. EEE is not as prevalent as WNV but can present more severe symptoms in humans and horses.

The public is reminded to take common-sense 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.

According to the Delaware Department of Agriculture (DDA), there were no equine cases of WNV or EEE in 2022. The State Veterinarian urges horse owners to contact their veterinarians to vaccinate horses and other equines against WNV and EEE. Both vaccines are highly effective in minimizing disease and may be the reason why Delaware had no equine cases in 2022. Horses that have been vaccinated in the past will need an annual booster shot. Neither disease has a specific drug treatment, and infections in horses are fatal in 70% to 90% of EEE cases and 30% of WNV cases.

Spraying to reduce mosquito populations in areas where WNV or EEE is detected may be initiated by the DNREC Mosquito Control Section as warranted, based on factors to include mosquito population levels and mosquito species present in affected areas. To reduce mosquito-breeding habitat and chances of disease transmission, residents should drain or remove outdoor items that collect water, such as discarded buckets or containers, uncovered trashcans, stagnant birdbaths, unprotected rain barrels or cisterns, old tires, upright wheelbarrows, flowerpot liners, depressions in boat tarps, clogged rain gutters, corrugated downspout extenders, and unused swimming pools.

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 at dawn and dusk, peak hours for mosquito activity. Topical insect repellents labeled for use on horses may be applied. Wind generated by fans installed in horse stalls can also help deter mosquitoes. Water troughs or buckets should be emptied, cleaned, and refilled every 2-3 days to remove mosquito eggs or larvae.

• 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.
• For animal health questions, contact the Delaware Department of Agriculture’s Poultry and Animal Health Section at 302-698-4500.
• To report suspected cases of human WNV, call the Delaware Division of Public Health Office of Infectious Disease Epidemiology toll-free at 888-295-5156.
  • For more information on West Nile virus or eastern equine encephalitis, visit cdc.gov/ncidod/dvbid/westnile/index.htm.

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 owned or managed by the Division of Fish and Wildlife. For more information, visit the website and connect with @DelawareDNREC on Facebook, Instagram,  Twitter or LinkedIn.

Media contacts: Michael Globetti, michael.globetti@delaware.gov; Nikki Lavoie, nikki.lavoie@delaware.gov
DDA: Stacey Hofmann, stacey.hofmann@delaware.gov

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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

Public Urged to Take Precautionary Measures Until Colder Weather Arrives in The Fall

Eastern Equine Encephalitis (EEE), a mosquito-transmitted disease, has been detected in Delaware the first time for 2022 in a sentinel chicken, the Delaware Department of Natural Resources and Environmental Control announced today. Mosquito-transmitted virus detections in DNREC’s sentinel chickens are unrelated to Delaware’s poultry industry.

The EEE finding in northern New Castle County was from a sentinel chicken station sampled by the DNREC Division of Fish and Wildlife Mosquito Control section and confirmed by the Delaware Public Health Laboratory Aug. 9. While there have been no reported EEE cases in humans this year in the state, Delawareans are reminded that the possibility of contracting mosquito-transmitted diseases, including EEE and West Nile Virus (WNV), will continue until colder autumn temperatures in late-October or later.

The first EEE-positive sentinel chicken for this year adds to five WNV-positive sentinel chickens found earlier at three other sentinel chicken arbovirus monitoring stations in New Castle and Kent counties – with the first WNV finding occurring in early July. No EEE or WNV human cases have been reported to date in 2022 by the Delaware Public Health Laboratory, nor have any EEE or WNV equine cases been reported by the Delaware Department of Agriculture.

Blood samples are collected by the Mosquito Control section each week from early July into October from the state’s outdoor-caged sentinel chickens that are humanely housed and handled at 20 monitoring stations statewide. The blood samples are tested for EEE and WNV antibodies by the Delaware Public Health Laboratory. Sentinel chickens bitten by mosquitoes carrying EEE or WNV develop antibodies to these diseases but are otherwise unaffected. Mosquitoes can transmit both WNV and EEE to humans and horses.

The public is reminded to take common-sense precautions to avoid mosquito bites, including wearing 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.

Spraying to reduce mosquito populations in areas where EEE or WNV is detected may be initiated by DNREC’s Mosquito Control section as warranted, based on factors to include mosquito population levels and mosquito species present in affected areas. To reduce mosquito-breeding habitat and chances of disease transmission, residents should drain or remove outdoor items that collect water, such as discarded buckets or containers, uncovered trashcans, stagnant birdbaths, unprotected rain barrels or cisterns, old tires, upright wheelbarrows, flowerpot liners, depressions in boat tarps, clogged rain gutters, corrugated downspout extenders and unused swimming pools.

While EEE is rarer than WNV, both EEE and WNV can adversely affect people and horses. Most people who become infected with EEE virus and WNV show either no or mild symptoms. Early symptoms in people contracting EEE or WNV can be similar, but EEE often becomes more pronounced and debilitating, manifested by meningitis or encephalitis typically resulting in hospitalizations. EEE has a higher human mortality rate of approximately 30%, with infants, children and the elderly most vulnerable, according to the U.S. Centers for Disease Control and Prevention. Symptoms in people infected with EEE usually start from four to 10 days after being bitten by a mosquito infected with EEE. Early EEE symptoms can include headache, high fever, stiff neck, tremors or muscle weakness, with more severe cases progressing to stupor, disorientation, coma, convulsions, paralysis and possibly death. 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 infected with WNV can develop serious illness involving neurological problems, paralysis and possibly death. There are no human vaccines for EEE or WNV. Anyone developing the symptoms described above should see their healthcare provider.

Horse owners should contact their veterinarian immediately if they suspect their horse may be showing signs of WNV or EEE. Symptoms of EEE in horses include fever (102.5-104.5°F), loss of appetite, head pressing, depression or personality change, wobbling or staggering, weakness, blindness, convulsions, muscle tremors in the head and neck or hind-limb weakness. These signs are also consistent with WNV, although a fever may or may not be present with WNV.

Additional information about mosquitoes and mosquito-transmitted diseases is available from the following resources:

• For mosquito biology/ecology and control, contact the 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.
• For animal health questions, contact the Delaware Department of Agriculture’s Poultry and Animal Health Section at 302-698-4500.
• To report suspected cases of human EEE or WNV, call the Division of Public Health Office of Infectious Disease Epidemiology toll-free at 888-295-5156.
• For more information on Eastern Equine Encephalitis or West Nile Virus, visit www.cdc.gov/ncidod/dvbid/westnile/index.htm.

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

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