A total of 50 birds diagnosed with mycobacteriosis were examined for pathomorphological lesions, coinfections, and causative agents. Mycobacterial species were identified and isolates differentiated using multilocus sequence typing (MLST) and mycobacterial interspersed repetitive-unit variable-number of tandem-repeat (MIRU-VNTR) analysis. Possible associations between mycobacterial species, pathomorphological findings, coinfections, bird orders, and husbandry conditions were evaluated statistically. Mycobacteria were isolated from 34 birds (13 of 22 Psittaciformes, 12 of 18 Passeriformes, five of six Columbiformes, and four other orders) belonging to 26 species in total. Mycobacterium genavense (Mg) was cultured from 15 birds, Mycobacterium avium subsp. avium (Maa) from 20 birds, and Mycobacterium avium subsp. hominissuis (Mah) from three birds; hence, four birds had mixed infections. About equal numbers of psittacines and passerines were infected with Ma and Mg. The genetic diversity differed; Mg isolates belonged to one MLST type, Maa to six, and Mah to three combined genotypes. Several coinfections were detected; viruses and/or endoparasites affected 44%, fungi 38%, and bacteria 29% of the birds. Pathological findings and mycobacteriosis-affected organs were independent of coinfections. Overall, gross pathological findings were more often seen in mycobacteriosis caused by Ma (95%) compared with Mg (66%). Organ distribution of mycobacteriosis was independent of the mycobacterial species. Pathomorphological changes were seen in the small intestine of 71% and the lung of 65% of the birds, suggesting oral or pulmonal ingestion of mycobacteria. There were no associations between mycobacterial species and bird orders or bird husbandry conditions. Not only Mg, but also Maa and Mah, were clearly identified as primary cause of mycobacteriosis in pet birds. IMPORTANCE In this study, the causative agents and confounding factors of mycobacteriosis in a set of pet and some wild birds from Germany were examined. Not only Mycobacterium genavense, but also M. avium subsp. avium and M. avium subsp. hominissuis, contributed to mycobacteriosis in these birds. Various coinfections did not affect the manifestation of mycobacteriosis. Due to different gross necropsy findings, however, a different pathogenicity of the two species was assumed. New strains of M. avium subsp. hominissuis originating from birds were identified and characterized, which is important for epidemiological studies and for understanding the zoonotic role of this pathogen, as the subsp. hominissuis represents an increasing public health concern. The study provides some evidence of correlation between M. avium subsp. avium genotypes and virulence which will have to be confirmed by broader studies.
Keywords: Mycobacterium avium; Mycobacterium genavense; Passeriformes; Psittaciformes; birds; coinfections; genotyping; husbandry; mycobacterioses; pathology.