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Host range and dynamics of mycoplasmal conjunctivitis among birds in North America
B K Hartup1, A A Dhondt, K V Sydenstricker
1Division of Wildlife Health, College of Veterinary Medicine, Cornell University, Ithaca, New York 14853, USA. hartup@savingcranes.org
Abstract:
An epidemic of conjunctivitis among house finches (Carpodacus mexicanus) caused by Mycoplasma gallisepticum (MG) bacterial infections was first described in 1994. The disease exhibits high primary host specificity, but has been isolated from a limited number of secondary avian hosts at various times and locations. We used records from the House Finch Disease Survey, a continent-wide, volunteer monitoring project, to document the host range of conjunctivitis in birds at feeding stations and to investigate how disease in house finches might influence the spread of conjunctivitis to other hosts. Between 1994 and 1998, participants recorded 675 cases of conjunctivitis in 31 species other than house finches in eastern North America. Seventy five % of these cases were observed among three species: American goldfinches (Carduelis tristis), purple finches (Carpodacus purpureus) and house sparrows (Passer domesticus). The proportion of sites with diseased wintering populations of the three species increased over the 4 yr study and coincided with range expansion of conjunctivitis in house finches. Sites with diseased house finches present were significantly more likely to report conjunctivitis in each of the three species during the same month. These observations are most consistent with transmission of an infectious agent (presumably MG) from house finches to these secondary hosts via spillover of localized epidemics, rather than sustained interspecific transmission.
Insights
Conjunctivitis, caused by Mycoplasma gallisepticum (MG), spread from house finches to other bird species at feeders. This spillover suggests localized epidemics, not sustained transmission, influenced disease spread.
Area of Science:
- Avian disease ecology
- Wildlife epidemiology
- Infectious disease transmission
Background:
- Conjunctivitis, caused by Mycoplasma gallisepticum (MG), emerged in house finches in 1994.
- While MG shows high host specificity, it has been detected in other avian species.
- Understanding MG transmission dynamics is crucial for avian conservation.
Purpose of the Study:
- To document the host range of conjunctivitis in birds at feeding stations.
- To investigate the influence of house finch disease on conjunctivitis spread to other hosts.
- To determine transmission patterns of Mycoplasma gallisepticum in wild bird populations.
Main Methods:
- Utilized data from the House Finch Disease Survey (1994-1998).
- Recorded conjunctivitis cases in 31 non-house finch species in eastern North America.
- Analyzed temporal and spatial correlations between diseased house finches and other species.
Main Results:
- 675 cases of conjunctivitis were recorded in 31 species.
- American goldfinches, purple finches, and house sparrows accounted for 75% of cases.
- Increased conjunctivitis in these species correlated with house finch epidemics and presence of diseased house finches.
Conclusions:
- House finches act as a significant reservoir for Mycoplasma gallisepticum.
- Transmission to secondary hosts likely occurs via epidemic spillover from house finches.
- Sustained interspecific transmission appears less probable based on current data.