Detection of Mycoplasma gallisepticum in house finches (Haemorhous mexicanus) from Arizona

Abstract

In 1994, an endemic poultry pathogen, Mycoplasma gallisepticum (Mg), was identified as the causative agent of a novel disease in house finches (Haemorhous mexicanus). Following an initial outbreak in Maryland, Mg spread rapidly throughout eastern North American house finches. Subsequently, Mg spread slowly through the northern interior of North America and then into the Pacific Northwest, finally reaching California in 2006. Through 2009, there were no reports of Mg in the southwestern United States east of California. In August 2011, following reports of house finches displaying conjunctivitis characteristic of Mg infection in Arizona, we trapped house finches at bird feeders in central Arizona (Tempe) and southern Arizona (Tucson and Green Valley) to assay for Mg infection. Upon capture, we noted whether birds exhibited conjunctivitis and collected choanal swabs to test for the presence of Mg DNA using PCR. We detected Mg in finches captured from Green Valley (in ~12% of birds captured) but not from Tucson or Tempe. Based on resampling of house finches at these sites in July 2014, central Arizona finches likely remain unexposed to Mg. We suggest that low urban connectivity between arid habitats of southern and central Arizona or a reduction in the prevalence of Mg following its initial arrival in Arizona may be limiting the spread of Mg from south to north in Arizona. We further suggest that the observed conjunctivitis-like signs in house finches that were negative for Mg by PCR may be caused primarily by avian poxvirus.