Warming Climate May Increase EHDV Risk in New York

By Blake Jackson

An insect-borne disease called epizootic hemorrhagic disease virus (EHDV) remains uncommon in New York state. However, rising temperatures and changing weather patterns may increase the risk of future outbreaks. The disease causes high death rates among white-tailed deer and can make cattle sick. Its symptoms also resemble those of foot and mouth disease, a serious animal disease that is not present in the United States.

A research team from Cornell University’s College of Veterinary Medicine studied the presence of EHDV in New York livestock. The findings appear in the journal Transboundary and Emerging Diseases in research published September 28. The study is reported by Krisy Gashler of the College of Veterinary Medicine, who highlighted the disease risks for livestock producers and wildlife managers. Researchers examine thousands of animal samples to understand how widely the virus has spread across the state.

Study Finds Low Levels of EHDV Exposure

The researchers examined 5,698 samples from cattle, sheep, and goats submitted to the university’s Animal Health Diagnostic Center for other reasons. The results showed that only 34 samples tested positive for EHDV antibodies. These included 31 cattle and three sheep.

Overall, only about 0.6% of the samples showed antibodies against the virus. Antibodies indicate that an animal has encountered the virus and developed an immune response. However, their presence does not necessarily mean the animal is currently sick.

The low percentage suggests that EHDV exposure among the tested livestock remains limited in New York. While this may seem encouraging, it also raises concerns about how animals may respond to a future outbreak.

How the Virus Spreads

EHDV spreads through the bites of certain small insects called Culicoides biting midges. These insects carry the virus from infected animals to other animals. The disease does not spread directly from one animal to another.

Weather conditions play an important role in the spread of EHDV. Dry periods can leave shallow pools of water and exposed muddy areas, creating suitable breeding conditions for biting midges. When temperatures rise and summers become warmer and drier, these insects may become more active or increase in number.

EHDV is widespread in warmer parts of the southern and southeastern United States. New York lies near the edge of the region where the disease occurs regularly. As the climate warms, the state may experience more frequent outbreaks, especially during hot, dry summers.

Effects on Deer and Cattle

White-tailed deer are particularly vulnerable to EHDV. The disease can cause severe illness and death, especially in areas where animals have little previous exposure to the virus.

New York experienced its worst recorded EHDV outbreak in 2021, when the virus killed an estimated 1,500 to 2,100 white-tailed deer.

Cattle may also become sick after infection. Although cattle die from EHDV less often than deer, the disease can still cause serious problems for farmers. Common symptoms include high fever, painful sores in the mouth, excessive salivation and tiredness.

Painful mouth sores can make cattle less willing to eat. Dairy cows may produce less milk, while beef cattle may gain less weight. These effects can reduce farm productivity and increase the cost of caring for sick animals.

Similarities to Foot and Mouth Disease

One major concern is that EHDV symptoms can resemble those of foot and mouth disease. This highly contagious disease affects animals with split hooves, including cattle, sheep, and goats. It can cause fever, blisters and sores around the mouth, nose, teats and hooves.

Foot and mouth disease is not present in the United States. State and federal agencies take strict steps to prevent its entry and spread.

“In the Southern and Southeastern U.S. where it’s warmer, EHDV is widespread. We’re on the cusp of where this occurs endemically, so when we have warmer, drier summers, that creates the right conditions for outbreaks here in New York,” said Elisha Frye, DVM ’10, associate professor of practice of population medicine and diagnostic sciences in the College of Veterinary Medicine (CVM) and the paper’s first author.

“The fact that we found so few animals with antibodies can be good or bad. Good because we don’t want this disease here, we don’t want to see white-tailed deer deaths of course, and we don’t want our farms disrupted by foot and mouth disease testing,” Frye said. “And bad because when a population is naive like this, they have less herd immunity to protect themselves when we do have a hot, dry year and the midges come.”

When officials suspect foot and mouth disease, farms may face temporary shutdowns while animals are isolated and tested. These steps help protect the livestock industry but can cause major financial losses and delays for farmers.

Steps to Monitor and Manage the Disease

Farmers, veterinarians, hunters, and hikers can help identify possible EHDV cases and reduce the risk of wider problems.

• Report dead deer: People who find dead deer near water should report them to the New York State Department of Environmental Conservation. Officials can examine the animals to determine the cause of death.
• Watch for sick cattle: Dairy and beef farmers should contact a veterinarian if cattle show signs of illness, lose their appetite, or produce excessive saliva.
• Report suspected foot and mouth disease: Veterinarians who observe symptoms such as fever, excessive salivation or painful blisters on the mouth, nose, teats or hooves should contact the New York State Department of Agriculture and Markets.
• Follow official guidance: State and federal authorities oversee testing when a serious animal disease is suspected.

EHDV remains rare in New York, but changing weather conditions may increase future risks. Early reporting, veterinary testing, and close monitoring can help protect wildlife, support livestock health, and limit disruptions to farm operations.

Photo Credit: istock-heebyj