EEE and West Nile Virus Activity in Michigan for 2023 - Confirmed Cases

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.

For More Information

Testing for Michigan Animals: MDARD Funds Available to Cover Costs

The Michigan Department of Agriculture and Rural Development (MDARD) is excited to announce the continuation of funding to cover the costs of testing suspect animals for eastern equine encephalitis (EEE) and West Nile virus (WNV) for 2023. 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 pre-approved by MDARD.
  • The samples are submitted to the Michigan State University Veterinary Diagnostic Laboratory (MSU VDL).

The grant aims to test any Michigan animal suspected of having a mosquito-borne illness, especially equids.

Last year, there were four cases of mosquito-borne diseases found in domestic animals in Michigan—three EEE cases and one WNV case. The grant funding helped to identify all of these cases.

It is important to test animals for mosquito-borne diseases because it not only helps confirm the presence of these viruses but also monitors for change. This information is also used for communicating risk to the public and assessing abatement needs.

To take advantage of this funding opportunity:

  • When a neurologic animal is suspected of having EEE or WNV, collect and refrigerate the samples. Acceptable samples include brain and/or blood. Brain is always preferred as this allows for a more definitive diagnosis of arboviruses. With brain samples, rabies testing will also be performed at no cost. When submitting blood, please collect and submit both serum and whole blood.
  • Complete a Reportable Animal Disease Form and make a request for this testing in the “Additional Information” field on the form. Submit the completed form to MDARD at If any complications or questions arise during this process, please call MDARD at 800-292-3939. Typically, requests are reviewed and responded to within one business day.
  • If approved, MDARD will email the needed laboratory form(s) to complete and submit to MSU VDL.
  • Submit the completed form(s) and sample(s) to MSU VDL. Further directions for sending the sample can be found on the submittal forms. If submitting brain, an animal’s head can be sent to the laboratory; the brain does not have to be removed prior to the sample being sent. To help aid in testing, MDARD may be able to transport the packaged head and completed forms to MSU VDL. Contact MDARD at 800-292- 3939 for more information.

Once the testing is completed, MDARD will send notification of the results, including a copy of the laboratory results.

As a reminder, when submitting samples, it is crucial to collect a thorough vaccine history on the animal, particularly when submitting blood. If possible, please try to determine when the animal was last vaccinated against EEE and WNV. In addition, it is helpful to know if the animal completed an initial vaccine series and who last vaccinated the animal (e.g., owner, veterinarian).

Testing animals for mosquito-borne diseases provides valuable information to help further protect animal and public health. Please be sure to take advantage of this opportunity.

For more information on mosquito-borne diseases and detections in equine, please visit the Michigan Emerging Diseases website or the Equine Disease Communication Center.