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Hello All,
My posting regarding mycoplasmal conjunctivitis in finch
populations has already generated some very good points and some
questions. Both of which I would like to address in this group email
format for efficiency's sake.
First there was an excellent point brought up regarding
avian pox. Avian pox is relatively common among wild birds and
the confusion of its symptoms with mycoplasmal conjunctivitis is very
possible. Both diseases can cause swelling and malformation of the
area around the eyes. The differences that do exist between the two
ailments exist within the cause and manifestation of the diseases.
Mycoplasmal conjunctivitis is caused by the bacterium Mycoplasma
gallisepticum (MG) and is a respitory disease. The outward symptoms
of MG infection are confined to the head; namely red, swollen, runny,
crusty eyes and nares. Conversely, avian pox is a virus and results in
warty growths on the unfeathered portions of the feet, legs, wings, and
face. As such, when you are watching a sick bird, pay special attentions
to the feet and legs to help identify the illness (if lumps are present it is
likely avian pox). In either case, report your findings.
Secondly, there was some question regarding the host
specificity of the MG pathogen. To date, it has been found in the
following wild bird species besides house finches:
American Goldfinch, Purple Finch, Evening Grosbeak, and Pine
Grosbeak. All members of the family Fringillidae. House finches are
far and away the most susceptible of the finches. Hypotheses
surrounding the house finch's high level of susceptibility stem from the
origination of the eastern house finch population. Originally only
found on the west coast, house finches were released in around New York City in
the 1940's and spread rapidly across the U.S. Because the Eastern
population was founded by such a small number of individuals,
which necessitated inbreeding, today's population exhibits low
genetic diversity. Combined with the characteristic to form large, mobile
flocks, genetic depression of the house finches has facilitated the spread of
the disease through the population.
Thirdly, there is some question of the consequences of this
disease with regards to the sustainability of finch populations. Using the
east coast as a template (they have had the disease in their wild finch
populations for 8 years now) to forecast what we can expect, leads us to be
conservative in the disease's effects. On the eastern seaboard
after the initial epidemic, mycoplasmal conjunctivitis infection rates
equilibrated at between 5% and 10%. Although there appears to be no
immediate threat of a dramtic population wide finch decline, gathering
information regarding the spread of the disease is still very important from the
perspective of human impacts on passerine species.
Finally, a note should be mentioned about feeder
hygiene. Although, feeders are reported to not have a net negative
effect the following guidelines from http://birds.cornell.edu/hofi/hofifaqs.html should
be followed to maintain healthy environment for the birds:
1) Space your feeders widely to discourage
crowding.
2) Clean your feeders on a regular basis with a 10% bleach solution
(1 part bleach and 9 parts water) and be sure to remove any build-ups of dirt
around the food openings. Allow your feeders to dry completely before rehanging
them.
3) Rake the area underneath your feeder to remove droppings and old,
moldy seed.
4) If you see one or two diseased birds, take your feeder down
immediately and clean it with a 10% bleach solution.
Happy birding!
Adam Kozlowski
Native Species Biologist Utah Division of Wildlife Resources, Northern Region 515 East 5300 South, Ogden UT 84055 Office: (801) 476-2740 Cell: (801) 510-2034 email: akozlowski@utah.gov |