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What's wrong with that bird's eyes One very noticeable sign of the House Finch disease we are studying is conjunctivitis. In case you’re not familiar with this term, conjunctivitis is the inflammation and swelling of the conjunctiva, the delicate membrane that lines the eyelids and covers the exposed surface of the eyeball. Conjunctivitis is a fairly common problem in captive birds and, to a lesser extent, free-living birds. The House Finch outbreak is caused by the microorganism Mycoplasma gallisepticum, but a variety of factors can cause conjunctivitis. The conjunctiva itself may become infected, or a secondary infection may develop after the conjunctiva is scratched, perhaps by a sharp bit of weed or seed. Conjunctivitis may also be a sign of a disease that affects the area around the eyeball, such as sinusitis (inflammation of the respiratory sinuses). In either case, some of the organisms that cause conjunctivitis include bacteria such as Chlamydia psittaci, Escherichia coli, and Pseudomonas aeruginosa; fungi such as Candida albicans; viruses; and nematodes and protozoa. Conjunctivitis can also be caused by exposure to aerosols such as cigarette smoke and chemical fumes, environmental toxins, and certain types of ultraviolet radiation. These irritating factors are not usually a problem for wild birds. If so many factors can cause conjunctivitis, why do we think that the crusty-eyed House Finches seen at feeders are indeed victims of Mycoplasma? Lab tests have confirmed the diagnosis in some locations. Also, most other diseases don’t usually cause such a severe infection. One that does, avian poxvirus, is transmitted by biting insects, so it’s not usually a problem for birds after the first hard freeze. George
V. Kollias |
