Comparison of cytology and histopathology for diagnosis of avian pox in wild turkeys

Avian poxvirus is a common cause of proliferative skin lesions in wild turkeys (Meleagris gallopavo); however, other etiologies such as neoplasia and bacterial infections may produce grossly indistinguishable lesions. The most... [ view full abstract ]

Avian poxvirus is a common cause of proliferative skin lesions in wild turkeys (Meleagris gallopavo); however, other etiologies such as neoplasia and bacterial infections may produce grossly indistinguishable lesions. The most common methods for diagnosis of avian pox are histopathology and polymerase chain reaction (PCR). While these methods are sufficient in most cases, both have limitations that restrict their use in some situations (e.g. antemortem testing, lack of tissue preservatives or laboratory support, etc.). Cytology is a cost-effective approach that may be useful when histopathology or PCR are not feasible. The objective of this study was to evaluate the performance of cytology relative to histopathology and PCR for avian pox diagnosis in wild turkeys. Thirty-seven wild turkeys were submitted for post-mortem examination due to proliferative lesions on the skin of the head. Of these, 5 had similar lesions on the skin of the legs and 19 had proliferative lesions in the upper gastrointestinal tract mucosa. Samples were collected from skin and upper gastrointestinal tract lesions for cytology, histopathology, and PCR (skin from head only). Twenty-seven of the 37 wild turkeys were diagnosed with avian pox based on histopathology and/or PCR. There were no significant differences between cytology and histopathology pox diagnoses for skin (p = 0.2482) or gastrointestinal tract (p = 0.1824) lesions. Relative to histopathology, cytology had a sensitivity of 90% and a specificity of 100% for skin lesions and a sensitivity of 61% and a specificity of 0% for gastrointestinal tract lesions. There were no significant differences between PCR and histopathology (p = 0.6171) or cytology (p = 0.2482) for skin lesions. Relative to PCR, cytology had a sensitivity of 89% and a specificity of 100%. These results suggest that cytology may serve as a useful tool for diagnosing avian pox in wild turkeys.