New lab test
identifies increased prevalence of a tick-borne pathogen causing spike in
babesiosis cases in Suffolk County
Columbia University's Mailman School of Public Health
Researchers
developed and employed a method to simultaneously test for five common
pathogens carried by deer ticks: Babesia microti, the pathogen behind
babesiosis; Borrelia burgdorferi, the cause of Lyme
disease; as well as Anaplasma
phagocytophilum, Borrelia miyamotoi,
and Powassan virus -- pathogens responsible for other tick-borne infections.
The team collected and tested 318 adult and nymph ticks at five sites in Suffolk County (Southampton, Mannorville, Southold, Islip, Huntington) and three sites in Connecticut (Mansfield, Stamford, Greenwich). Nymphal ticks are about the size of a poppy seed, emerge in warmer months, and are responsible for the majority of tick-borne disease.
A Better Test
The
new test uses a DNA amplification technique called polymerase chain reaction or
PCR to test for tick-borne pathogens.
Most existing tests use this method to
test ticks for each agent individually. Even the tests that have the ability to
test for more than one agent typically only test for up to three, not five
agents, and never for Powassan virus, the rarest but most pathogenic of the
five.
The scientists say the technique has several advantages: it lowers costs,
facilitates testing for agents (B.
miyamotoi, and especially Powassan virus) that are rarely tested for, and
provides risk assessments for co-infections which may adversely affect the
course of disease.
What They Found
Tests
found B. microti present in a higher proportion of
ticks in Suffolk County than Connecticut, including 17 vs. 7 percent of nymphal
ticks. In both locations, B. burgdorferi,
the causative agent for Lyme disease, was the most frequently detected agent in
ticks tested while A. phagocytophilum, B. miyamotoi and Powassan virus were more rare.
One-quarter
of B. burgdorferi-positive nymphs were also
positive for B. microti suggesting a risk of co-infection with both agents from
a single tick bite. "Gathering data on co-infections is particularly
important in light of the fact that antibiotics used for Lyme disease may be
ineffective for babesiosis," says first author Rafal Tokarz, a research
scientist at CII.
Better Surveillance Needed
The
number of counties in the Northeast with high rates of Lyme disease has more
than tripled since the 1990s -- a sign that ticks that spread disease have
expanded their range.
Rates of tick-borne illness may be much higher than
reported: one study in Minnesota found 79 percent of cases were not reported to
health authorities. Symptoms include fever and headaches, and, more rarely,
neurological complications like encephalitis.
"This
new test can strengthen surveillance for tick-borne illnesses which are
underreported and growing rapidly," says W. Ian Lipkin director of CII and
John Snow Professor of Epidemiology at the Mailman School.