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Mosquito

Mosquitoes are more than just a nuisance in the great outdoors — they can also spread harmful diseases to humans and animals alike. The MSU VDL tests for these harmful diseases to help veterinarians and public health officials identify and track cases.

Many people know that mosquitoes transmit heartworm infections, malaria and Zika virus but in Michigan, two mosquito-borne viral diseases — West Nile virus, or WNV, and Eastern equine encephalitis, EEE, — pose a fatal threat to humans and animals, especially horses. While EEE cases primarily occur in the Eastern U.S., WNV is found throughout the United States.

Please include vaccination status when submitting equine samples and use our equine submittal form. See our test catalog for information on sample type, collection protocol, shipping requirements, and other important information.

EEE Activity in Michigan for 2021 - Confirmed Cases

October 14, 2021 - Eighth Case of EEE in Equine

The Michigan Department of Agriculture and Rural Development is reporting one additional case of Eastern Equine Encephalitis (EEE) in a horse from Ingham County, bringing the total number of equine cases for 2021 to eight.

On October 2, 2021, a 17-year-old Arabian gelding became ill with neurologic signs, including ataxia, muscle fasciculations, fever, a reluctance to move, and circling. The horse’s condition rapidly deteriorated, and the gelding was humanely euthanized later that day.

The animal was vaccinated by the owner in the spring, but it is unclear if the vaccine for EEE was included in that treatment.

For more information, please visit the Equine Disease Communication Center or Michigan.gov/EEE.

October 12, 2021 - Eastern Equine Encephalitis Continues to Pose a Threat to Michiganders and Their Animals

For immediate release: October 12, 2021 | MDARD Media Contact: Chelsea Lewis-Parisio, 517-331-1151 | MDHHS Media Contact: Chelsea Wuth, 517-241-2112

LANSING, MI - Today, the Michigan Department of Agriculture and Rural Development confirmed the discovery of three new cases of Eastern Equine Encephalitis (EEE) in horses from Genesee and Shiawassee (2) counties. These findings highlight the mosquitoes carrying EEE are still alive and active, and Michiganders still need to take precautions to safeguard their animals and themselves.

EEE is a dangerous, zoonotic mosquito-borne disease which is typically seen in the state from late summer to early fall. Even though it is now October, the mosquitoes that carry EEE will continue to pose a threat until there has been at least one hard freeze where the temperatures fall below 28 degrees Fahrenheit for several hours. Due to this year’s mild fall temperatures, the mosquitoes are continuing to circulate in the environment and spread the virus.

With the addition of these newest cases, Michigan has experienced a total of eight cases of EEE in animals for 2021: one deer from Livingston County and seven horses from Barry, Genesee, Livingston (2), Otsego, and Shiawassee (2) counties. There was also the discovery of one EEE-positive mosquito pool in Barry County.

Fortunately, no human cases of the disease have been identified this year. Overall, while case numbers are down from the total seen in 2020 (41 animal cases and four human cases), there is still a need for Michiganders to actively protect their animals and themselves from EEE.

“When combatting EEE, the date on the calendar is not as important as the temperatures being experienced,” said State Veterinarian Nora Wineland, DVM. “Our current mild temperatures mean horse owners should not ease up on taking precautions, including vaccination. Since the mortality rate of EEE in horses can be as high as 90 percent, it is important for owners to work with their veterinarian to ensure their animals are properly vaccinated.”

To further protect horses and other domestic animals (such as dogs, sheep, and goats) from the mosquitoes that carry EEE, owners are encouraged to eliminate standing water on their property, place livestock in a barn under fans from dusk to dawn to avoid peak mosquito activity, use insect repellants that are approved for the species, and contact a veterinarian if an animal displays any sign of illness—fever and stumbling, which can progress to being down and struggling to stand.

“Michiganders need to continue taking precautions against mosquitoes as they take advantage of our current mild weather conditions and enjoy outdoor activities,” said Dr. Natasha Bagdasarian, chief medical executive at the Michigan Department of Health and Human Services. “People can also be infected with EEE from the bite of a mosquito carrying the virus, which can lead to serious health impacts and even death.”

Applying insect repellants, wearing long-sleeved shirts and long pants, maintaining window and door screening, and following other precautions can help Michigan residents avoid mosquito bites and stay healthy.

For more information about EEE, please visit Michigan.gov/EEE.

October 7, 2021 - Fourth Case of EEE in Michigan Horses

The Michigan Department of Agriculture and Rural Development (MDARD) is reporting a fourth case of Eastern Equine Encephalitis (EEE) in a 10-year-old Quarter Horse mare from Barry County.

On September 25, 2021, the mare became ill with neurological signs, including ataxia and a fast heartrate. The disease progressed to the mare being down with an inability to get up and shaking. The horse was then humanely euthanized. It is unknown if the mare was ever vaccinated against EEE.

For more information, please visit the Equine Disease Communication Center or Michigan.gov/EEE.

October 5, 2021 - New Cases of EEE and WNV

The Michigan Department of Agriculture and Rural Development (MDARD) is reporting two additional cases of Eastern Equine Encephalitis in horses for 2021, bringing the total number of cases for the year to three. One case occurred in a 14-year-old Thoroughbred mare from Livingston County, which is believed to be unvaccinated. This is the second case of EEE in a horse from Livingston County for 2021. The other case occurred in a one-year-old Quarter Horse colt from Otsego; this is the first ever report of the disease in a domestic animal from that county. Both animals were humanely euthanized due to the severity of their disease. For more details, please review the latest message posted by MDARD.

In addition, MDARD would also like to report three new cases of West Nile virus (WNV) in horses from Kent, Montcalm, and Sanilac counties, bringing the total number of WNV cases in domestic animals to four.

The Kent County case occurred in a vaccinated 31-year-old Quarter Horse gelding. On August 5, 2021, the gelding became ill with neurological signs, including ataxia and walking backwards/continually trying to back up. The horse’s condition deteriorated, and the animal was euthanized on August 20, 2021.

The Montcalm County case occurred in an unvaccinated eight-year-old Standardbred mare. The mare became ill on September 4, 2021, with neurological signs, including ataxia. As of September 15, 2021, the mare was still alive.

And, the Sanilac County case involved a three-month-old standardbred filly that became ill around September 18, 2021, with ataxia, which progressed to the horse being down, unable to get up, and paddling. The filly was unvaccinated and was euthanized due to the severity of her disease.

For more information on EEE, WNV, and other equine diseases, please visit the Equine Disease Communication Center.

August 27, 2021 - First Mosquitoes of 2021 Carrying Eastern Equine Encephalitis Virus Found in Barry County

FOR IMMEDIATE RELEASE: Aug. 27, 2021

CONTACT: Lynn Sutfin, 517-241-2112, SutfinL1@michigan.gov

LANSING, Mich. – Michigan residents are being reminded by the Michigan Department of Health and Human Services (MDHHS) to protect themselves from mosquito bites following the detection of the first Eastern Equine Encephalitis (EEE)-positive mosquito pool of the year in Barry County.

The discovery in Barry County follows a report by the Michigan Department of Agriculture and Rural Development of an EEE-positive horse from Livingston County and underscores the need for both Michigan residents and horse owners to take precautions.

“These discoveries indicate that the EEE virus is here in Michigan and provides warning that residents could also become infected by a mosquito,” said Dr. Joneigh Khaldun, MDHHS chief medical executive and chief deputy director for health. “Michigan residents are urged to take precautions and protect themselves from mosquito bites as EEE is one of the most dangerous mosquito-borne diseases in the U.S., with a 33 percent fatality rate among humans who become ill.”

EEE has a 90 percent fatality rate in horses that become ill, and infection in both people and animals occurs through the bite of an infected mosquito. EEE is not spread from person-to-person.

Signs of EEE include the sudden onset of fever, chills, and body and joint aches. Illness can eventually develop into severe encephalitis, resulting in headache, disorientation, tremors, seizures and paralysis. Permanent brain damage, coma and death may also occur in some cases.

This is the first year the MDHHS Bureau of Laboratories has been performing testing on mosquitoes collected by local health departments and academic partners. To date, over 43,000 mosquitoes have been tested.

Residents can stay healthy by following steps to avoid mosquito bites:

  • Apply insect repellents that contain the active ingredient DEET, or other U.S. Environmental Protection Agency-approved product, to exposed skin or clothing, and always follow the manufacturer’s directions for use.
  • Wear long-sleeved shirts and long pants when outdoors. Apply insect repellent to clothing to help prevent bites.
  • Maintain window and door screening to help keep mosquitoes outside.
  • Empty water from mosquito breeding sites around the home, such as buckets, unused kiddie pools, old tires or similar sites where mosquitoes may lay eggs.
  • Use nets and/or fans over outdoor eating areas.

“For horses, EEE is a serious but preventable disease,” said State Veterinarian Nora Wineland, DVM. “Positive mosquito pools can help to identify areas of risk. Horse owners should work with their veterinarian to develop a plan to protect their animals.”

To safeguard their horses, owners could take the following measures:

  • Talking to a veterinarian about vaccinating horses against EEE.
  • Placing horses in a barn under fans (as mosquitoes are not strong flyers) during peak mosquito activity from dusk to dawn.
  • Using an insect repellant on the animals approved for the species.
  • Eliminating standing water on the property-i.e., fill in puddles, repair eaves, and change the water in buckets and bowls at least once a day.
  • Contacting a veterinarian if a horse shows signs of the illness: mild fever and stumbling, which can progress to being down and struggling to stand.

Additionally, West Nile virus activity in Michigan has increased in wildlife and mosquito populations. Health officials have identified 11 positive mosquito pools and 10 infected animals in the Lower Peninsula. No human cases of West Nile virus have been reported to date; however, a case has been reported in a horse from Midland County.

Mosquito-borne illness will continue to be a risk in Michigan until late fall when nighttime temperatures consistently fall below freezing.

For more information about mosquito-borne diseases, visit Michigan.gov/emergingdiseases.

August 26, 2021 - State Confirms Eastern Equine Encephalitis in Livingston County Horse

For immediate release: August 26, 2021

Media contacts: Jennifer Holton, MDARD, 517-284-5724 | Lynn Sutfin, MDHHS, 517-241-2112

LANSING, Mich. — Today, Michigan Department of Agriculture and Rural Development State Veterinarian Dr. Nora Wineland confirmed Michigan’s first case of Eastern Equine Encephalitis (EEE) for 2021 in a two-year-old Standardbred filly from Livingston County. EEE is a zoonotic, viral disease transmitted by mosquitoes to both animals and people; it is typically seen in late summer to early fall each year in Michigan.

This discovery underscores the need for both horse owners and Michigan residents to take precautions. EEE is one of the most dangerous mosquito-borne diseases in the U.S. with a 90 percent fatality rate among horses that become ill and a 33 percent fatality rate among humans who become ill. Last year, Michigan experienced 41 cases of EEE in animals and four cases in humans.

“The Livingston County horse was never vaccinated against EEE, and it developed signs of illness—including fever, lethargy, and depression—which progressed to the animal exhibiting neurologic signs and being down on the ground with an inability to get up. The horse was euthanized due to her declining condition,” said Wineland. “It is critically important for horse owners to reach out to their veterinarian to discuss how to best protect their animals from this disease.”

To protect your animals, measures could include the following:

  • Talking to a veterinarian about vaccinating horses against EEE.
  • Placing horses in a barn under fans (as mosquitoes are not strong flyers) during peak mosquito activity from dusk to dawn.
  • Using an insect repellant on the animals approved for the species.
  • Eliminating standing water on the property—i.e., fill in puddles, repair eaves, and change the water in buckets and bowls at least once a day.
  • Contacting a veterinarian if a horse shows signs of the illness: mild fever and stumbling, which can progress to being down and struggling to stand.

People can also be infected with EEE from the bite of a mosquito carrying the virus. The disease is not spread by horse-to-horse or horse-to-human contact. In humans, signs of EEE include the sudden onset of fever, chills, and body and joint aches. The virus can also cause severe encephalitis, resulting in headaches, disorientation, tremors, seizures, and paralysis. Permanent brain damage, coma, and death may occur in some cases.

“This equine case indicates the EEE virus is here in Michigan and provides a warning that residents could also become infected by a mosquito,” said Dr. Joneigh Khaldun, MDHHS chief medical executive and chief deputy director for health. “Michigan residents are urged to take precautions and protect themselves from mosquito bites.”

Residents can stay healthy by following steps to avoid mosquito bites:

  • Applying insect repellents containing the active ingredient DEET (or other U.S. Environmental Protection Agency-approved products) to exposed skin or clothing, and always following the manufacturer’s directions for use.
  • Wearing long-sleeved shirts and long pants when outdoors. Applying insect repellent to clothing to further prevent bites.
  • Maintaining window and door screening to help keep mosquitoes outside.
  • Emptying water from mosquito breeding sites around the home, such as buckets, unused children’s pools, old tires, or similar sites where mosquitoes may lay eggs.
  • Using nets and/or fans over outdoor eating areas.

Overall, mosquito-borne illnesses, like EEE, will continue to pose a risk to both animals and humans until late fall when nighttime temperatures consistently fall below freezing.

For more information about mosquito-borne diseases, visit Michigan.gov/EmergingDiseases.

West Nile Virus Activity in Michigan for 2021 - Confirmed Cases

October 19, 2021 - Fifth Case of WNV

The Michigan Department of Agriculture and Rural Development (MDARD) is reporting a fifth case of West Nile virus (WNV) in a 13-year-old grade mare from Lenawee County.

On October 7, 2021, the mare became ill with neurological signs including ataxia, a reluctance to move, muscle fasciculations, muzzle tremors, and grinding of the teeth. While the horse was vaccinated by the owner, it is unclear if the horse was vaccinated against WNV. The horse is alive and recovering.

This is the first reported case of WNV ever in a domestic animal from Lenawee County, and this report brings the total number of WNV cases in equids for 2021 to five: Kent, Lenawee, Midland, Montcalm, and Sanilac.

For more information on EEE, WNV, and other equine diseases, please visit the Equine Disease Communication Center.

September 3, 2021 - First West Nile Virus Case of 2021 Detected in Oakland and Macomb County Residents

FOR IMMEDIATE RELEASE: Sept. 3, 2021

CONTACT: Chelsea Wuth, 517-241-2112, WuthC@michigan.gov

LANSING, Mich. – The first cases of West Nile virus (WNV) have been detected in residents in Oakland and Macomb counties. Michiganders are reminded that the best way to protect against West Nile virus and other mosquito-borne illnesses such as WNV and Eastern Equine Encephalitis (EEE) is to prevent mosquito bites.

In the past week, mosquitoes collected in the City of Detroit and Bay, Kent, Macomb, Midland, Oakland and Wayne counties have tested positive for WNV and Jamestown Canyon virus (JCV). Additionally, EEE virus was identified in a sick deer from Livingston County. The risk for mosquito-borne illness rises throughout the state over the course of the mosquito season, peaking in August and September.

“It only takes one bite from an infected mosquito to cause a severe illness, so take extra care during peak mosquito-biting hours, which are dusk and dawn,” said Dr. Joneigh Khaldun, MDHHS chief medical executive and chief deputy director for health. “As we head into the holiday weekend and beyond, we urge Michiganders to take precautions such as using insect repellant and wearing long-sleeve shirts and long pants when outdoors during those time periods.”

WNV is transmitted through the bite of a mosquito that has picked up the virus by feeding on an infected bird. Most people who contract the virus have no clinical symptoms of illness, but some may become ill three to 15 days after the bite of an infected mosquito. Symptoms of arbovirus infection, like WNV, typically include a high fever, confusion, muscle weakness and a severe headache. More serious complications include neurological illnesses, such as meningitis and encephalitis.

The best way to prevent West Nile disease or any other mosquito-borne illness is to reduce the number of mosquitoes around your home and to take personal precautions to avoid mosquito bites. Precautions include:

  • Using EPA registered insect repellents with one of the following active ingredients: DEET, picaridin, IR3535, oil of lemon eucalyptus or para-menthane-diol, and 2-undecanone; follow the product label instructions and reapply as directed.
    • Don’t use repellent on children under 2 months old. Instead dress your child in clothing that covers arms and legs and cover crib, stroller and baby carrier with mosquito netting.
  • Wearing shoes and socks, light-colored long pants and long-sleeved shirts when outdoors.
  • Making sure doors and windows have tight-fitting screens. Repair or replace screens that have tears or other openings.
  • Using bed nets when sleeping outdoors or in conditions with no window screens.
  • Eliminating all sources of standing water that can support mosquito breeding around your home, including water in bird baths, abandoned swimming pools, wading pools, old tires and any other object holding water once a week.

To date, 22 mosquito samples, eight birds, one squirrel and one horse have tested positive for WNV. EEE virus has been found in a horse and deer from Livingston County and a mosquito sample from Barry County.

For more information, visit Michigan.gov/WestNileVirus or CDC.gov/WestNile.

August 10, 2021 - First Cases of West Nile Virus for 2021 Underscores the Need for Michiganders to Take Steps to Protect Against Mosquito-Borne Diseases

For immediate release: August 10, 2021

Media contact: Jennifer Holton, 517-284-5724

LANSING, MI — Cases of West Nile virus (WNV) are being seen once again in Michigan’s animal and mosquito populations. These findings emphasize the need for Michigan residents to take precautions to safeguard not only their animals but also themselves from mosquito-borne illnesses.

WNV typically circulates between birds and mosquitoes, but mosquitoes can also transmit the disease to people and animals, especially horses and other equids. In Michigan, the disease is typically a concern every summer to early fall. The virus is spread through bites from an infected mosquito.

The Michigan Department of Agriculture and Rural Development (MDARD) recently confirmed the first case of WNV for 2021 in a 28-year-old Quarter Horse mare from Midland County. On July 15, 2021, the mare became ill with a sudden onset of neurologic disease and was humanely euthanized. The horse was undervaccinated against WNV.

“With the discovery of WNV in a Michigan horse, this signals that the virus is circulating again in the state,” said State Veterinarian Nora Wineland, DVM. “Its presence underscores the need to take all the necessary steps to protect animals from this disease.”

To combat the spread of this disease, animal owners can:

  • Talk to their veterinarian about vaccinating their horses against WNV and other mosquito-borne illnesses like Eastern Equine Encephalitis (EEE). There are highly effective, safe vaccines available.
  • House their livestock in a barn under fans (as mosquitoes are not strong flyers) during peak mosquito activity from dusk to dawn.
  • Use insect repellant on animals that is approved for the species.
  • Eliminate standing water on the property—i.e., fill in puddles, repair eaves, and change the water in buckets and bowls at least once a day.
  • Contact a veterinarian if an animal shows signs of the illness: mild fever, lack of appetite, lethargy, weakness, stumbling, tremors, and a droopy lip and/or head tilt. Please also note that various mosquito-borne diseases are reportable to MDARD. Cases can be reported by completing and submitting a Reportable Disease Form to MIReportableAnimal@Michigan.gov.

For context, while there were no reported cases of WNV in domestic animals in 2020, there was one case of the disease in a Lapeer County horse in 2019. Also, the state saw more significant WNV activity in 2017 with 15 cases reported in equids.

In addition to the case in a horse, WNV has also been detected in mosquito and wildlife populations this year. The virus has been identified in five wild birds from four Michigan counties (Berrien, Calhoun [2], Cass, and Ingham) and three mosquito pools from three counties: Calhoun, Kent, and Oakland.

“We urge Michiganders to continuously take precautions to protect themselves (in addition to their pets and livestock) against mosquitoes. It only takes one bite from an infected mosquito to cause a severe illness,” said Dr. Joneigh Khaldun, chief medical executive and chief deputy for health at MDHHS. “Steps like using an EPA-registered insect repellent when outdoors, avoiding areas where mosquitoes are present (if possible), and wearing clothing to cover arms and legs to prevent bites can help.”

For more information about WNV, please visit Michigan.gov/WNV.

Arbovirus Testing Funding for Michigan Animals

For 2021, the Michigan Department of Health and Human Services is again sponsoring a grant that will provide funding to cover the costs of testing suspect animals for Eastern Equine Encephalitis (EEE) and West Nile virus (WNV). The funding is open to anyone in Michigan provided:

  • The animal for testing resides in Michigan.
  • The animal is (or was recently) showing signs of neurological disease or suddenly died.
  • The testing is preapproved by the Michigan Department of Agriculture and Rural Development (MDARD).
  • The samples are submitted to Michigan State University’s Veterinary Diagnostic Laboratory.

Please see Arbovirus Testing information from the Michigan Department of Agriculture and Rural Development for complete details.