Emily Martin and Joanne Rafuse

Animal Health Laboratory, University of Guelph, Guelph, ON (Martin);

Zorra Veterinary Service, Thamesford, ON (Rafuse)

AHL Newsletter 2021;25(3):19.

In early July 2021, 6-week-old meat turkeys presented with increased mortality and lameness. The birds had been moved a week prior to presentation.  The birds were raised on shavings in the brooder barn and were moved onto shavings in a clean and disinfected grower barn at 5 weeks of age. Three barns were affected.  Birds were submitted for postmortem examination from the most severely affected barn.

On postmortem examination, the birds were noted to have air sac lesions suspicious for fungal organisms (Fig. 1), as well as osteomyelitis and tibial dyschondroplasia.  Tissues were fixed in formalin and submitted to the AHL for histopathology.

On histopathology, the air sacs had mats of fungal organisms (Fig. 2), and the lungs had multiple tiny fungal granulomas (Fig. 3).  The bone section had a large abscess spanning the growth plate and articular cartilage, extending across 1/3 of the width of the growth plate (Fig. 4).  Fungal organisms were identified within the abscess, growth plate and infiltrating the articular cartilage (Fig. 5 and 6).  Air sac swabs were positive for E. coli (1+ and 4+), and the fungus was isolated and identified as Aspergillus fumigatus complex.  The reovirus PCR on tendons was negative.

Fungal osteomyelitis is an uncommon lesion and could be related to extension of infection from thoracic air sacs into bone air sac diverticula; however, the affected tibiotarsal bone in this case is not one of the aerated bones in birds.  Fungemia (fungal septicemia) may therefore be a possible route of infection.  Considering the air sac and lung lesions were mild, it is unclear why bone was affected in this case.  AHL

Figure 1. White nodule in air sac (arrow).	Figure 2. Mat of fungi over air sac nodule.  H&E.
Figure 3.  Pulmonary fungal granuloma. H&E.	Figure 4.  Abscess spanning growth plate and articular cartilage. H&E.
Figure 5. Fungal organisms (arrows). PAS.	Figure 6. Fungal hyphae (arrows). PAS.