When conducting necropsies on birds from a flock suspected to have highly pathogenic avian influenza (HPAI), what finding is consistent with this disease?

When investigating a flock suspected of highly pathogenic avian influenza (HPAI), the finding of no significant gross lesions at necropsy can indeed be consistent with this disease, especially in the early stages or in subclinical infections. HPAI often presents with a variety of clinical signs, but it is important to note that in some cases, affected birds may not show overt lesions that are readily observable at necropsy despite being affected by the virus.

The manifestation of HPAI can vary significantly based on factors like the strain of the virus, the species of the bird, and the duration of the infection. Although birds may exhibit symptoms such as respiratory distress or other severe clinical signs, the absence of significant gross lesions can occur, particularly in cases where the birds have not progressed far enough in the disease process for lesions to develop.

In a practical diagnostic context, finding no significant gross lesions might prompt further testing, such as histological examination or molecular diagnostics, to confirm the presence of the virus or any associated lesions that might not be visible macroscopically. This highlights the need for a holistic approach to diagnosis, where clinical signs, necropsy findings, and laboratory results are all considered in the context of HPAI.