Lyme research targeting mice and birds

For studying strains of the bacteria
Thu, 10/03/2019 - 6:15pm
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Researchers from Columbia University have been catching mice and birds on Block Island to inform a research study focused on the impact of ecology on Lyme disease. The researchers have taken blood samples from the animals to study the strains of the bacteria.

The hope, as it has been for many years with other research studies regarding the debilitating disease, is to gather information, gain insight, and find a way to combat Lyme’s impact on the human body.

Matthew Combs, PhD, a postdoctoral research scientist at Columbia University, said, “If we find the strains that are the most specialized, that allow them to infect humans and mammals, then we might be able to target them with drugs and vaccines.” Combs, who is part of a research team, headed by Danielle Tufts, a Postdoctoral Fellow at Columbia University, has been conducting field research on Block Island for Dr. Maria Diuk-Wasser of Columbia University. The research is aimed at studying the role ecology plays in fostering Lyme disease and babesiosis.

“Lyme disease is the most important vector-borne disease, or zoonotic disease in the United States,” he said, during an interview at the Island Free Library. A zoonotic disease is a disease spread between animals and people. “Lyme has been around since before the ice age,” said Combs, who noted that from all of the research being conducted, “We know more about the system than we ever have, especially with the ecological approach we’re taking.” The goal: “We want to understand the ecological system so it can be controlled in some way.”

Diuk-Wasser echoed Combs’ sentiments: “We know from genetics that Lyme disease been around for thousands of years. The recent 100 years expansion is due to reforestation; the increase in deer populations; increase in human interaction with natural areas with ticks, and possibly climate change. I don't think we are close” to a solution, she said. “There don't appear to be any silver bullets, rather, we need combined methods to have an impact, and, for now, education of the public in methods to reduce their risk is essential.”

“With a genetic system like Lyme disease, the deeper you look, the more complicated it gets,” said Combs. He said what makes Block Island interesting is it doesn’t have many mammals living in its ecology. “The mice are the most important hosts on the island. They are really competent vectors.”

Diuk-Wasser has visited the island many times and explained the life cycle of the deer tick, involving its hosts. The mice transmit Lyme disease after a deer tick bites them, and then, in turn, spreads the disease by biting humans. The deer serve as hosts for the life cycle of the adult deer tick. The adult ticks take a blood meal from a deer, then fall off and lay eggs on the forest floor. When newly hatched larvae take a blood meal from infected mice, they become infected themselves. After molting into nymphs over the winter those ticks take a second blood meal, potentially infecting this new host, whether it is a mouse or a human.

“This is why nymphs are so dangerous,” said Combs. “They can be infected with Lyme and they are extremely small, making them easy to miss if you aren't careful.”

Combs and Alexandria Soldo, a Field Technician, arrived on the island in May and conducted research until the end of August, taking blood samples from mice and birds for testing. They set 110 to 120 traps per day at times to catch mice, and mist nets to capture birds to extract blood samples, which they freeze, preserving them in vials. Those vials are brought to the lab for research.

Combs said protocols for the treatment of animals have to be approved by an animal care committee at Columbia University. He also said, “Killing the mice we catch would not be effective” in curtailing disease.

Combs said his research team brings the samples containing the disease to the lab at Columbia University for testing. “We go in and pull out the DNA sequence that codes for a particular protein, and look at mutations in genes from different strains,” he said, adding that there are “specialist strains that infect certain types of animals.”

With the new technology, he said, “We can now grab whole chunks of DNA to study,” instead of being relegated to sampling small sequences. “We’re going to try and sequence the whole gene.”

One problem researchers have to contend with is the role that evolution plays in ecology. “There is a lot of evolution going on,” said Combs, noting that the animals’ immunity to the disease is constantly evolving, as well as the bacteria. It is something the researchers need to be aware of as their research continues, and their methods and technology advance.

Another problem is trying not to contract the disease while conducting field studies. “I’ve been bit about five times,” said Combs, who preaches vigilance in protecting oneself. “I got the bulls-eye after a bite when I was 12 years old. It was my first experience learning about the dangers of ecology. I’ve always been interested in public health and evolutionary biology.”

Combs said the research team could use more volunteers participating in the study through use of The Tick App, a free smartphone app, which examines how daily activities expose people to tick related diseases. The website can be found at www.thetickapp.org.

The researchers also had the good fortune of finding one of Eben Horton’s glass floats at Rodman’s Hollow while conducting their research. Combs said it was hidden inside of a tire sitting on the side of a trail.

Lyme testing results

Dr. Peter Krause of the Yale School of Medicine and Public Health told The Times that 21 percent of the 51 people who participated in his free Lyme disease testing held on May 26 at the Block Island Medical Center tested positive for Lyme disease. Six percent of the participants tested positive for babesia, he said.

“We had a small turnout. I’m not sure why,” said Krause, who noted that the date of the testing, Memorial Day weekend, might have played a role in the diminished number of participants. The testing typically sees about 125 to 150 participants annually at the Medical Center.

Krause said this year’s results were “pretty high” for people testing positive with Lyme disease. He noted in 2017 that 10 to 15 percent of the people who took the test, were found to have the disease, while approximately eight percent contracted babesiosis. 

The testing tells us that “these infections are still occurring on Block Island,” said Krause. “It’s still there” in Block Island’s ecology. “We’re not seeing evidence that it’s diminishing.”

Krause said the four deer that were brought to the island in 1967 for sporting activities led to an amplification of the number of Lyme disease cases on the island over the years. He also said he will be visiting Block Island “some time in the fall,” to discuss results from a student’s master thesis on the data collected and analyzed from the Lyme disease testing.