01/26/1994

Tick Paralysis Again Affecting Wild Birds

AUBURN, Ala. - A neighborhood watch for sick or dead birds is being requested by researchers at Auburn University who are trying to learn more about a tick-borne paralysis that is affecting wild birds.

According to Gary Mullen, professor in Auburn's Department of Entomology, several cases of this tick-induced illness have been reported recently in Lee County and surrounding areas, indicating that an outbreak is occurring.

"During the past few years, birds that were parasitized by ticks were observed showing signs of illness or found dead around feeders and homes. This is sort of an on-and-off phenomenon," said Mullen, who is well known for his Alabama Agricultural Experiment Station research on ticks and Lyme disease. "It pops up one year and may not be seen the following year or many years thereafter."

Mullen said there were no cases reported to him last year, though for three of the past four years there had been cases reported.

"This year we have had five or six birds brought to our attention," he said. "All of the local cases, with the exception of one chipping sparrow, have been house finches. We also got a call just before Christmas from a veterinarian in Memphis who had a client bring in two birds with ticks attached."

"In every case, the same tick species (Ixodes brunneus), commonly known as the bird tick, was found on the birds," said Mullen. "This tick has been reported in the past to cause death or pathological problems in birds, but those reports were very infrequent," Mullen continued.

According to Mullen, tick-induced paralysis occurs when a feeding tick introduces a substance through its saliva that disrupts the normal transmission of electrical impulses along nerves leading to the muscles.

The paralysis begins in the lower or hind limbs and moves upward or forward, eventually reaching the chest area, Mullen said. Death results from respiratory failure when the diaphragm muscles can no longer function effectively. Interestingly, removal of the tick usually results in complete recovery of the affected animal.

The outbreaks typically occur in late fall through early spring. From November to March 1987-88, six birds were found either partially paralyzed or dead in Lee County as a result of one or more engorged ticks attached to the head or neck. Six more functionally impaired or dead birds were reported from December to April 1990-91 in Chambers, Lee and Macon counties, each parasitized by the same tick species.

The reported cases have involved one or more of the following bird species: common grackle, chipping sparrow, yellow-rumped warbler, American goldfinch, house finch, dark-eyed junco, American robin and mourning dove.

Mullen noted that the bird tick poses no health threat to humans, but learning more about this phenomenon may result in medical advances for both humans and other animals. He noted that tick-induced toxicosis can occur in a number of animals, including cattle, sheep, goats, dogs and occasionally cats and humans. Knowing more about what causes this paralysis could be a boon to health professionals, and understanding the unique pharmacological properties of the toxin could be valuable in neuromedical research.

Scientists are unsure what causes these outbreaks and why certain ticks are capable of inducing paralysis and others are not. "If we can get enough live ticks, recovered from paralyzed birds, there is a possibility of working with a microbiologist to see what is causing this toxicosis," said Mullen.

Because these cases are infrequent and difficult to study in controlled experiments, Mullen hopes to gain more information through reports from citizens who notice strange behavior among birds.

"Most cases involve a single, conspicuous, fully engorged female tick attached to the head," he noted. "Typical behavior to look for in affected birds is staggering or difficulty walking, impaired flight or inability to fly at all, lethargy and puffed or fluffed-up feathers."

Anyone noticing birds that are exhibiting these characteristics may contact Mullen at (334) 844-2554. Mullen also requests that observers try to collect any visible ticks from affected birds.

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Auburn University College of Agriculture
Alabama Agricultural Experiment Station
3 Comer Hall, Auburn University
Auburn, AL 36849
334-844-4877 (PHONE) 334-844-5892 (FAX)

Contact Jamie Creamer, 334-844-2783 or jcreamer@auburn.edu
Contact Katie Jackson, 334-844-5886 or smithcl@auburn.edu

01/26/94