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Birdscope Articles

Selected abstracts:

Risk factors associated with mycoplasmal conjunctivitis in house finches: Results from a citizen-based study.  Hartup, Barry K., Hussini O. Mohammed, George V. Kollias, and André A Dhondt. 1998. Journal of Wildlife Diseases 34(2): 281-288.

Density-dependent decline of host abundance resulting from a new infectious disease.   Hochachka, Wesley M. and André A. Dhondt. 2000. Proceedings of the National Academy of Sciences of the USA 97:5303-5306

Beginnings of an epidemic in the Northwest 

This year's data revealed unusually high numbers of House Finches with eye infections in the first widespread epidemic of House Finch eye disease recorded in the West.The data show that the disease began spreading epidemically in the Northwest in early 2004, 10 years after it began in the East. In February through April 2004, disease prevalence in the northwestern states was half again compared with the highest levels previously observed there (British Columbia, Alberta, Washington, Idaho, Montana, Oregon, and Wyoming). By February 2004, disease prevalence had reached 15 percent in the Norhtwest. No similar increases were detected in California or in the Southwest (see figure below).

House Finch eye disease in the West:
In 2004, reports of House Finch eye infections spiked in the Northwest, indicating an epidemic. No similar increases occurred in California or the Southwest. The graph includes only those months for which we had at least 25 participants in each region.

Avian pox is another disease that can affect a bird's eyes, and is fairly common in western North America.  While conjunctivitis causes red, swollen, and sometimes encrusted eyes, avian pox is characterized by wart-like growths. The two diseases cannot always be easily distinguished when the infection is in the early stage, but when warty lesions are present, it is likely to be avian pox.

We need your help!

Why was there a two-year lag between the time House Finch eye disease was detected in a small population of finches in Montana in April 2002 and when an epidemic broke out in the Northwest? In Montana and other inland areas where humans live farther apart, House Finch populations are more isolated from each other, perhaps slowing the spread of the disease. Another reason could be that House Finches are less susceptible to the diseas in their native range in the West than in the East, where the finches are descended from a small number of birds introduced in the 1940s. The makings of an epidemic also probably require an element of chance; in several midwestern states, the disease-causing bacterium had to arrive several times before it became established and caused an epidemic.

For us to study the prevalence and geographic range of mycoplasmal conjunctivitis, we need to know where it occurs as well as where it does NOT occur. Your participation is thus essential even if you never observe diseased birds. Otherwise, our estimates of disease prevalence will be biased by positive sightings.


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