Invaders! Disease-carrying ticks hitchhike into US
on migratory birds
From: Smithsonian Science News
Researchers who examined thousands of migratory birds arriving in the United States from Central and South America have determined that three percent carry ticks species not normally present in the United States. Some of the birds, they say, carry disease-causing Ricksettia ticks.
Based on the total number of
migratory birds arriving in the U.S. each spring—in the billions—the
investigators estimated that more than 19 million exotic ticks hitchhike into
the U.S. with them, says Emily Cohen, a postdoctoral fellow at the Smithsonian
Migratory Bird Center in Washington, D.C.
Cohen is co-author of a recent article on this study in Applied and Environmental Microbiology, a journal of the American Society for Microbiology.
As yet there is no evidence
that any neotropical ticks have established themselves in the U.S. “It takes
the right combination of biotic and abiotic features for the neotropical ticks
to survive, reproduce and spread,” says co-author Sarah Hamer, Assistant
Professor in the Department of Veterinary Integrative Biosciences at Texas
A&M University.
The ticks typically take their first and second blood meals
on birds, but once they become adults, they seek out large mammals such as
sloths or anteaters, she explains, noting the absence of these mammals in the
U.S.
“Nonetheless, an adult
of one of the neotropical tick species we found on migrants, Amblymma longirostre, was
recently found crawling outside of a home in Oklahoma, in the fall,” says
Cohen. It “could represent a bird-imported nymph that arrived in the spring and
successfully molted.”
Precedent does exist for
implicating migratory birds in range expansions of ticks and disease. For example,
the range of African bont ticks and the livestock-infecting bacterial species
they carry,Ehrlichia ruminatium, expanded to the Caribbean, probably
after the ticks hitched a ride on migratory cattle egrets.
E. ruminantium, causes
heartwater disease, which reduces livestock productivity. Also, migratory birds
are responsible for expanding populations of Lyme disease ticks beyond their
northern distribution limit, into Canada.
Continue reading at Smithsonian Science News.