Ginsberg, Howard [faculty advisor, Department of Plant Sciences]
ticks; birds; diseases; Lyme disease
Lyme disease, a tick-borne bacterial illness, is the most common vector-borne infection in north temperate areas worldwide. Ticks, while minute in size, can be competent vectors of both human and animal diseases. Upon hatching, larvae must take a blood meal in order to transform into the next life stage. When taking this first blood meal, the larval tick may ingest blood containing pathogens. If this occurs, the newly emerged nymphal tick is capable of transmitting infection to the next host, which can become infected and, if reservoir competent, infective. When the pathogen carrying vector is attached long enough, a host can acquire the infection. Through this process, the disease is amplified and transmitted between several hosts.
While often not the first animals to be considered effective reservoirs of Lyme disease, wild birds do indeed serve as hosts to the Ixodes scapularis ticks that transmit the infection. Certain bird species, such as the American Robin, have been shown to sustain enough of the infectious agent, Borrelia burgdorferi bacteria, to be transmitters of the pathogen to subsequent feeding ticks. These black-legged ticks then feed on other hosts, such as domestic and wild animals and humans, and can infect susceptible hosts through saliva during feeding.
Although not well known, several factors can affect the associations between wild birds and ticks, influencing the likelihood of tick recruitment, attachment, and drop-off time. By compiling and analyzing data from field studies on Fire Island, NY, the dynamics of bird-tick associations were investigated here. The factors focused on in this research were the following: bird body temperature, bird body weight, and Lyme disease infection status. Several species were studied and comparisons made between birds of the same species and those with similar characteristics.
Through the available data and analyses, conclusions about the conditions surrounding successful tick attachment, feeding, and possible disease transmission can be made. Surprisingly, no correlation between tick recruitment and bird foraging habitat was found. Also, no concrete findings of the effects of bird body temperature and weight on tick attachment could be confirmed, possibly because of low power in the statistical analyses. However, there was a significant relationship between infection status in certain bird species, Gray Catbird and Song Sparrow, and tick drop-off time. Because of the transmission delay between tick attachment and host infection, this potentially has important implications for the spread of Lyme disease. Further investigation into the associations between wild bird species and infectious ticks is essential to a better understanding and improved control of the disease. Revealing the factors that influence this interaction has the potential to allow for new prevention techniques and a reduction in the number of Lyme disease cases in this endemic area.