Submitted to: Avian Diseases
Publication Type: Research Notes
Publication Acceptance Date: June 8, 1998
Publication Date: N/A
Interpretive Summary: Aspergillosis, caused by infection with Aspergillus fumigatus, is a common respiratory disease of poultry that results in carcass condemnation at slaughter inspection. There is no vaccine or cost-effective treatment available. Experimental vaccine failures prompted this study to determine if natural recovery from aspergillosis would protect against re-exposure. In all other types of infectious disease, natural recovery (convalescence) induces a stronger protective immune response against the disease than does vaccination. The results of this study showed that although the majority of infected turkeys completely recovered, they were not protected against pulmonary aspergillosis subsequent to re-exposure. Therefore, convalescence from pulmonary aspergillosis does not confer protection against re-exposure but may, instead, decrease resistance to subsequent infection in turkeys. This indicates that conventional approaches to vaccination will not be helpful in preventing aspergillosis in poultry and illustrates the need to apply unconventional research strategies (i.e., nonspecific immunomodulators) to aspergillosis prevention.
Technical Abstract: Pulmonary lesions resulting from Aspergillus fumigatus inoculation were assessed in convalescent turkeys and compared to those in previously non- inoculated (control) turkeys. In addition, lesions observed in Small Beltsville White (SBW) were compared with those in Broad-Breasted White (BBW) turkeys challenged with the same inoculum. Turkeys were challenged by unilateral posterior thoracic air sac (PTAS) inoculation, rechallenged via the contralateral air sac after five weeks, and then necropsied one week later. Pulmonary lesions induced by the initial challenge had resolved in 6/10 SBW and 9/10 BBW turkeys. However, convalescence did not protect against pulmonary aspergillosis subsequent to rechallenge, as 10/10 SBW and 9/10 BBW developed granulomatous pulmonary lesions on the side of re-exposure. A greater proportion of control SBW turkeys developed pneumonia and airsacculitis following challenge as compared to the BBW breed, indicating possible increased susceptibility of SBW turkeys to aspergillosis. Lesions were limited to the lower respiratory tract in all turkeys and also were confined to the ipsilateral lung and PTAS in the singly-inoculated control turkeys. This study demonstrates that convalescence from pulmonary aspergillosis does not confer protection against rechallenge but may, instead, decrease resistance to subsequent infection.