Migratory Birds Transport Disease-Carrying Ticks Into US, New Study Shows

Non-native pathogen-carrying ticks are making it past U.S. customs, hitching rides on migratory birds from Central and South America on migratory birds, according to a new study. 

After researchers examined thousands of migratory birds that had just entered the U.S., they found that three percent of the birds carried exotic ticks. Statistically speaking, that means 19 million exotic ticks arrive in the U.S. each spring.

There is some good news, however. Researchers noted that there is no evidence that suggests the ticks have not yet fully established themselves in the U.S., meaning they have not become widespread.

"It takes the right combination of biotic and abiotic features for the neotropical ticks to survive, reproduce and spread," Sarah A. Hamer, one of the study's researchers, said in a statement.

The ticks generally take their first and second blood meals on birds, but once they become adults, they seek out large mammals such as sloths or anteaters, Hamer explained. While these animals are not present in the U.S., the ticks could eventually accept other species as substitute hosts.

"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, which could represent a bird-imported nymph that arrived in the spring and successfully molted," Emily B. Cohen, a researcher from the Migratory Bird Center and Smithsonian Conservation Biology Institute, added.

Researchers also noted that warmer temperature could aid in ticks establishing themselves in the U.S.

To assess which animals could become potential hosts, Hamer has begun examining diverse wild mammals for neotropical ticks. Her study includes rodents, raccoons, coyotes, and feral hogs, which are abundant across Texas.

The study was recently published in the journal Applied and Environmental Microbiology. 

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