Ecology

Mild winter = ticks and biting insects

Anne Gageby
Strawberry Hill Nature Preserve

(6/2023) The last hard frost is finally behind us despite this year’s vacillating slide into spring. It’s been an interesting year, weather-wise. The deep freeze of December melted into a fairly mild winter overall. The lack of steady freezing temps creates a perfect opportunity for insect populations to endure and come back with a vengeance in spring.

Biting insects are already riding in on the tide of warmer weather. This is an unwelcome shift for anyone who enjoys the outdoors. Ticks, mosquitoes, midges, and other biting insects have come into their season after a winter spent buried beneath leaf litter and occasional snow. And what a season it will be.

By all accounts, we’re looking at a record year for ticks and biting insects. I found a tick on me back in the middle of March, far earlier than I would normally expect. And the mosquitoes have long since made their spring debut. These vector species can carry a wide array of diseases that affect human and animal populations alike. Not every disease is zoonotic though, meaning some diseases are not transmissible between animals and humans. Even still, plenty of animal-specific diseases are worrisome for other reasons.

Two viruses of concern within the deer population specifically are Bluetongue Virus and Epizootic Hemorrhagic Disease. Both are most common during the late summer and early fall and are spread via midges, also known as no-see-ums. Bluetongue Virus and Epizootic Hemorrhagic Disease are known to cause general Hemorrhagic Disease (HD) which brings a wide variety of symptoms and can have a mortality rate of up to 70 percent depending on the location and specific animal population. Fortunately, neither Epizootic Hemorrhagic Disease nor Bluetongue Virus are known to infect humans.

Back in September, the Penna. Game Commission put out information for hunters after an outbreak of Hemorraghic Disease in Lebanon and Lancaster counties. As we head toward summer, landowners and outdoor enthusiasts should be aware of both viruses that cause Hemorraghic Disease and keep an eye out for signs of them as the weather gets warmer. Signs of infection include fever, small hemorrhages or bruising in the nose and mouth as well as swelling of the head, tongue, neck, and lips. Deer may appear emaciated and have sloughing hooves. Deer infected with EHD may also appear dehydrated and will often seek out water sources. Multiple dead deer in one location, especially by water, should be reported to the Game Commission as this could be a sign of an outbreak.

Because of the mild winter, we can expect the midge population to explode this year, potentially bringing about higher cases of Hemorrhagic Disease. NaVve deer populations could be impacted due to their lack of prior infection. From a wildlife management perspective, vector control could be possible but would be a significant challenge. Climate change is adding additional pressure to wildlife management practices, making controlling vector populations that much more difficult. For these reasons, monitoring and tracking are critical to management.

If Hemorrhagic Disease is no threat to humans, then why should people keep an eye out for suspicious deer? Unfortunately, the answer to this question involves a much larger discussion about the state of deer populations in our area. Deer already face habitat loss, predation, and a number of other threats. When we calculate environmental stressors and add in deadly diseases such as Hemorrhagic Disease, the final result could be catastrophic for local herds. Here on the East Coast, Hemorrhagic Disease is one of the most common diseases in white-tailed populations. An outbreak can cause a significant number of deaths. And as we’ve seen numerous times over the last two centuries, when one species declines, others are significantly impacted. Our ecosystem is a delicate set of dominos in which every animal is important.

So what can average citizens do? It starts with monitoring. The public plays a vital role in the surveillance of wildlife. When incidents of sick, injured, or dead animals are reported, it provides the Game Commission an opportunity to collect and test samples for any number of wildlife diseases. Hemorrhagic Disease occurs with some regularity within Pennsylvania specifically and the Game Commission tracks it closely, both when and where exactly it’s occurring. Tracking also allows the Game Commission to identify which strains are predominant.

Hemorrhagic Disease has been found in most states except for areas in the Southwest and extreme Northeast. While there are a number of common animal hosts white-tailed deer are the most susceptible. Other host species include pronghorn antelope and bighorn sheep. While elk can be infected with Hemorrhagic Disease, they are not as susceptible as white-tailed deer. Of the two main viruses which cause Hemorrhagic Disease, Epizootic Hemorrhagic Disease is not common in domestic animals while Bluetongue Virus is well-known in cattle, sheep, and goats. Neither BTV nor EHD are transmissible to humans but BTV can be transmissible to some animals such as dogs.

Farmers and those who raise these animals would be right to be concerned about either virus infecting their animals. There is a limited risk if farm animals share the same space as infected deer. Domestic animal owners should keep this and many other wildlife diseases on their radar. When disease is spread by an insect vector, control is a challenge. Being smart and keeping wildlife away from domestic animals (and vice versa) reduces disease transmission risk.

Looking toward summer, the public should keep in mind that peak vector (midge) season is late summer into early fall. Outbreaks are more common during that time of year. However, as mild as the winter was, it’s a good idea to keep a careful eye on animals under your care or that you may encounter in the wild. Wildlife health incidents such as suspected cases of Hemorrhagic Disease should be reported to the Game Commission by calling 833-PGC-WILD (742-9453) or online through the Wildlife Health Survey tool.

Anne Gageby is the Environmental Education Manager of the Strawberry Hill Foundation. Strawberry Hill inspires stewardship of our natural world by
connecting the community with educational opportunities.
 Learn more by visiting StrawberryHill.org.