News Brief: Bio prof. sheds light on Lyme disease

Recent research by Penn biology professor Dustin Brisson suggests that chipmunks and two shrew species account for nearly three-quarters of carriers of ticks infected with Lyme disease.

The widely held belief was that mice were the main animal carriers of the disease.

The research was conducted in Hudson Valley with Daniel Dykhuizen of Stony Brook University and Richard Ostfeld of the Institute of Ecosystem Studies.

In a University press release Brisson said, "The majority of zoonotic diseases, those that can be transmitted from wild or domestic animals to humans, are generally assumed to have one natural animal host."

Though deer are often associated with transmitting Lyme-disease infected ticks to humans, the insects are rarely infected with the bacteria from the deer's blood.

Rather, ticks harbor the disease after they first drink the blood of a vertebrate, which Brisson's research shows is often from chipmunks and shrews in addition to mice.

Mice were originally thought to be the primary carriers because nearly 90 percent of ticks feeding on an infected mouse contract the disease.

Comments (2)

This is mis-leading because it looks at a tiny piece of the picture. Ticks have a 2 year life cycle. In the first year, during the larvae to nymph stage, ticks feed on small mammal hosts and become infected with the bacteria. In the second year, during the nymphal to adult stage, ticks (already infected) must migrate to large mammal hosts (predominately deer). Once the female ticks have engourged for a number of days, they drop off and lay egg sacks with between 2,000 and 18,000 eggs. If deer are reduced to 8 to 10 per square mile, and maintained at that level over time, after two years (once all the existing living ticks die off), Lyme Disease is effectively eradicated from the area as proven (and continues to be proven today) in the Mumsford Cove study. Why? Because the female ticks did not have adequate large mammal hosts to feed on, and die, which means they do not reproduce the tens of thousands of eggs/larvae - which would then repeat the cycle. If Block Island would reduce the deer population to 8 to 10 per square mile, their Lyme Disease rates would drop like Mumsford Cove (from approx 30 cases annually to approx 3 cases annually)

There are no shrews or chipmunks on Block Island, RI. yet there is a high incidence of Lyme disease and other known tick borne diseases including Babesiosis and Bartonella. So,this may account for some of the geographic differences. Martha Agricola Family Nurse Practitioner retired

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