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Response of black-capped chickadees to house finch Mycoplasma gallisepticum.

Dhondt AA, Dhondt KV, Hochachka WM - PLoS ONE (2015)

Bottom Line: All house finches developed severe eye lesions but none of the black-capped chickadees did.Modeling the Rapid Plate Agglutination test results of black-capped chickadees shows that the rate of false-positive tests would be not more than 3.2%, while the estimated rate of false negatives is 55%.We conclude that the proportion of wild-caught individuals in which we detect M. gallisepticum-specific antibodies using Rapid Plate Agglutination is, if anything, substantially underestimated.

View Article: PubMed Central - PubMed

Affiliation: Bird Population Studies, Laboratory of Ornithology, Cornell University, Ithaca, New York, 14850, United States of America.

ABSTRACT
Tests for the presence of pathogen DNA or antibodies are routinely used to survey for current or past infections. In diseases that emerge following a host jump estimates of infection rate might be under- or overestimated. We here examine whether observed rates of infection are biased for a non-focal host species in a model system. The bacterium Mycoplasma gallisepticum is a widespread pathogen in house finches (Haemorhous mexicanus), a fringillid finch, but an unknown proportion of individuals of other songbird species are also infected. Our goal is to determine the extent to which detection of M. gallisepticum DNA or antibodies against the bacteria in a non-fringillid bird species is over- or underestimated using black-capped chickadees Poecile atricapillus, a species in which antibodies against M. gallisepticum are frequently detected in free-living individuals. After keeping black-capped chickadees in captivity for 12 weeks, during which period the birds remained negative for M. gallisepticum, four were inoculated with M. gallisepticum and four were sham inoculated in both eyes to serve as negative controls. Simultaneously we inoculated six house finches with the same isolate of M. gallisepticum as a positive control. All inoculated birds of both species developed infections detectable by qPCR in the conjunctiva. For the 6 weeks following inoculation we detected antibodies in all M. gallisepticum-inoculated house finches but in only three of the four M. gallisepticum-inoculated black-capped chickadees. All house finches developed severe eye lesions but none of the black-capped chickadees did. Modeling the Rapid Plate Agglutination test results of black-capped chickadees shows that the rate of false-positive tests would be not more than 3.2%, while the estimated rate of false negatives is 55%. We conclude that the proportion of wild-caught individuals in which we detect M. gallisepticum-specific antibodies using Rapid Plate Agglutination is, if anything, substantially underestimated.

No MeSH data available.


Related in: MedlinePlus

Mean number of copies of M. gallisepticum DNA detected in response to inoculation with a house finch strain of M. gallisepticum in conjunctival swabs of 6 house finches (circles) and 4 black-capped chickadees (squares).The 4 control black-capped chickadees sham-inoculated with Frey’s medium remained negative throughout (not shown). The values on the y-axis are the means log-transformed counts from qPCR with their standard errors.
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pone.0124820.g001: Mean number of copies of M. gallisepticum DNA detected in response to inoculation with a house finch strain of M. gallisepticum in conjunctival swabs of 6 house finches (circles) and 4 black-capped chickadees (squares).The 4 control black-capped chickadees sham-inoculated with Frey’s medium remained negative throughout (not shown). The values on the y-axis are the means log-transformed counts from qPCR with their standard errors.

Mentions: All birds remained negative for antibodies on seven Rapid Plate Agglutination tests during the 81 days of the pre-inoculation period suggesting high test specificity. In none of the birds of either species did we detect M. gallisepticum DNA prior to inoculation. After sham-inoculation the negative control black-capped chickadees remained negative for M. gallisepticum by qPCR and Rapid Plate Agglutination test. After inoculation all four inoculated black-capped chickadees developed M. gallisepticum infections in the conjunctiva that were detectable by qPCR, but none developed physical signs. Upon necropsy none showed macroscopic lesions in any organ. Average black-capped chickadee M. gallisepticum load increased to day 7 and fluctuated to day 21 PI, after which it decreased to undetectable levels by day 42 PI (Fig 1). Even for birds in which bacterial DNA was detected, it was not consistently detected over the entire likely period of infection: we detected M. gallisepticum DNA on only 2 out of 6 sampling dates in three birds (days 3 and 7; 3 and 21; 7 and 21 PI), and in 4 consecutive dates in the fourth individual. (days 7, 14, 21, 28 PI) suggesting a low M. gallisepticum load in the conjunctiva of black-capped chickadees following experimental inoculation. M. gallisepticum DNA was no longer detected on day 42 PI. M. gallisepticum-specific antibodies were detected in only three of four black-capped chickadees, even though active infections by the pathogen were confirmed in all black-capped chickadees in our tests for presence of DNA, implying a low diagnostic sensitivity for the Rapid Plate Agglutination test in black-capped chickadees and/or a weak serological response.


Response of black-capped chickadees to house finch Mycoplasma gallisepticum.

Dhondt AA, Dhondt KV, Hochachka WM - PLoS ONE (2015)

Mean number of copies of M. gallisepticum DNA detected in response to inoculation with a house finch strain of M. gallisepticum in conjunctival swabs of 6 house finches (circles) and 4 black-capped chickadees (squares).The 4 control black-capped chickadees sham-inoculated with Frey’s medium remained negative throughout (not shown). The values on the y-axis are the means log-transformed counts from qPCR with their standard errors.
© Copyright Policy
Related In: Results  -  Collection

License
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getmorefigures.php?uid=PMC4400008&req=5

pone.0124820.g001: Mean number of copies of M. gallisepticum DNA detected in response to inoculation with a house finch strain of M. gallisepticum in conjunctival swabs of 6 house finches (circles) and 4 black-capped chickadees (squares).The 4 control black-capped chickadees sham-inoculated with Frey’s medium remained negative throughout (not shown). The values on the y-axis are the means log-transformed counts from qPCR with their standard errors.
Mentions: All birds remained negative for antibodies on seven Rapid Plate Agglutination tests during the 81 days of the pre-inoculation period suggesting high test specificity. In none of the birds of either species did we detect M. gallisepticum DNA prior to inoculation. After sham-inoculation the negative control black-capped chickadees remained negative for M. gallisepticum by qPCR and Rapid Plate Agglutination test. After inoculation all four inoculated black-capped chickadees developed M. gallisepticum infections in the conjunctiva that were detectable by qPCR, but none developed physical signs. Upon necropsy none showed macroscopic lesions in any organ. Average black-capped chickadee M. gallisepticum load increased to day 7 and fluctuated to day 21 PI, after which it decreased to undetectable levels by day 42 PI (Fig 1). Even for birds in which bacterial DNA was detected, it was not consistently detected over the entire likely period of infection: we detected M. gallisepticum DNA on only 2 out of 6 sampling dates in three birds (days 3 and 7; 3 and 21; 7 and 21 PI), and in 4 consecutive dates in the fourth individual. (days 7, 14, 21, 28 PI) suggesting a low M. gallisepticum load in the conjunctiva of black-capped chickadees following experimental inoculation. M. gallisepticum DNA was no longer detected on day 42 PI. M. gallisepticum-specific antibodies were detected in only three of four black-capped chickadees, even though active infections by the pathogen were confirmed in all black-capped chickadees in our tests for presence of DNA, implying a low diagnostic sensitivity for the Rapid Plate Agglutination test in black-capped chickadees and/or a weak serological response.

Bottom Line: All house finches developed severe eye lesions but none of the black-capped chickadees did.Modeling the Rapid Plate Agglutination test results of black-capped chickadees shows that the rate of false-positive tests would be not more than 3.2%, while the estimated rate of false negatives is 55%.We conclude that the proportion of wild-caught individuals in which we detect M. gallisepticum-specific antibodies using Rapid Plate Agglutination is, if anything, substantially underestimated.

View Article: PubMed Central - PubMed

Affiliation: Bird Population Studies, Laboratory of Ornithology, Cornell University, Ithaca, New York, 14850, United States of America.

ABSTRACT
Tests for the presence of pathogen DNA or antibodies are routinely used to survey for current or past infections. In diseases that emerge following a host jump estimates of infection rate might be under- or overestimated. We here examine whether observed rates of infection are biased for a non-focal host species in a model system. The bacterium Mycoplasma gallisepticum is a widespread pathogen in house finches (Haemorhous mexicanus), a fringillid finch, but an unknown proportion of individuals of other songbird species are also infected. Our goal is to determine the extent to which detection of M. gallisepticum DNA or antibodies against the bacteria in a non-fringillid bird species is over- or underestimated using black-capped chickadees Poecile atricapillus, a species in which antibodies against M. gallisepticum are frequently detected in free-living individuals. After keeping black-capped chickadees in captivity for 12 weeks, during which period the birds remained negative for M. gallisepticum, four were inoculated with M. gallisepticum and four were sham inoculated in both eyes to serve as negative controls. Simultaneously we inoculated six house finches with the same isolate of M. gallisepticum as a positive control. All inoculated birds of both species developed infections detectable by qPCR in the conjunctiva. For the 6 weeks following inoculation we detected antibodies in all M. gallisepticum-inoculated house finches but in only three of the four M. gallisepticum-inoculated black-capped chickadees. All house finches developed severe eye lesions but none of the black-capped chickadees did. Modeling the Rapid Plate Agglutination test results of black-capped chickadees shows that the rate of false-positive tests would be not more than 3.2%, while the estimated rate of false negatives is 55%. We conclude that the proportion of wild-caught individuals in which we detect M. gallisepticum-specific antibodies using Rapid Plate Agglutination is, if anything, substantially underestimated.

No MeSH data available.


Related in: MedlinePlus