Tick threats rising across state as biodiversity declines

From 1999 to 2004, there were 31 cases of Lyme Disease reported in Ontario, but by 2022, there were 1,478.

SHARON – With the arrival of spring comes thoughts of flowers and gardens — and, unfortunately, ticks.

The disease-carrying arachnids were the focus of the latest Policy Potluck session hosted by Sharon Audubon on March 19.

The speaker was Dr. James Shepherd, an infectious disease physician at Yale School of Medicine and Yale New Haven Hospital, specializing in tuberculosis and other mycobacterial infections. He teaches climate change, biodiversity loss, and other global processes shaping infectious disease. Shepherd is also the owner of Smokedown Farm, which was once the largest hop grower in Connecticut, but is now transitioning to native and novel fruits.

Connecticut, said Shepherd, is one of the most tick-infested states. Ticks feed on the blood of mammals, birds, reptiles and amphibians and often transmit disease.

He named a variety of ticks, including the blacklegged, Lone Star, Asian longhorned, Gulf Coast and American dog ticks, noting they are transmitting a whole new set of diseases, besides the commonly known Lyme disease. “We’re seeing a wider biodiversity of pathogens,” he said.

Projecting maps on a screen, Shepherd displayed the types of ticks found in various sections of the United States, noting that incidences of Lyme disease are moving northward into Canada. In 2000, cases were largely concentrated in New England. From 1999 to 2004, there were 31 cases reported in Ontario, but by 2022, there were 1,478. The main reason is due to migratory birds, such as robins, along with mice and chipmunks.

Scientists believe the increase in Lyme disease is also linked to decreased biodiversity, driven in part by suburban expansion.

Researchers have linked the spread of tick-borne disease to declining biodiversity and habitat disruption across the Northeast. Shepherd spoke of the dilution effect, notably studied in Lyme disease, that concludes that high biodiversity reduces the transmission of pathogens to humans.

He presented a slide depicting the idea put forth by the Cary Institute of Ecosystem Studies in Millbrook, NY, that when many species exist in a community, vectors (like ticks) are more likely to bite hosts that are not good reservoirs for the disease, preventing the pathogen from spreading efficiently.

He said biodiversity is taking another hit from the rise of invasive species, which provide ideal habitats for ticks and their hosts. Japanese barberry is a prime example.

Climate change is also a major factor, as is habitat fragmentation, the process in which large, continuous natural habitats are divided into smaller patches, usually by such activities as road construction or urban development. This separation restricts wildlife movement, reduces population sizes, and disrupts ecosystems, acting as a major threat to biodiversity.

“We got problems,” Shepherd declared.

So what can people do? Shepherd asked. He then listed activities that often don’t work, such as excessive landscaping, deer fencing and spraying, which restricts biodiversity. He suggested having more respect for the environment by installing native plants, reducing habitat fragmentation, monitoring biodiversity and using personal protection.

Shepherd has worked in Nigeria, Botswana, India and Bangladesh, implementing national HIV and TB treatment programs and supporting COVID-19 treatment in refugee camps for both the U.S. government and the World Health Organization.