Bacterial arthritis in broiler breeder chickens
Andrew Brooks, Emily Martin, Siobhan O’Sullivan, Tanya Rossi
Animal Health Laboratory, University of Guelph, Guelph, ON
AHL Newsletter 2022;26(4):15.
Lameness due to bacterial infection is a common problem in poultry. This article summarizes the features of bacterial arthritis in broiler breeder chickens in 55 postmortem submissions to the AHL in 2022.
The clinical histories frequently described leg problems, lameness and swollen hocks. Several submissions also reported ongoing or persistent lameness, foot lesions, increased mortality due to culling, and reduced production. The age of the affected birds varied from 1 day to 37 weeks, with an average age of 20 weeks. The clinical problems involved both roosters and hens in approximately half of the submissions.
At postmortem examination, severe arthritis and tenosynovitis were consistently observed in the hock joints. The affected joints typically contained turbid, yellowish inflammatory exudate that extended along the gastrocnemius tendons (Fig. 1A). The shoulder and stifle joints were affected less frequently. Many birds also had lesions indicating septicemia, such as splenomegaly. Less common findings included tendon rupture, osteomyelitis (e.g., tibiotarsal bone), femoral head necrosis, sternal bursitis, and pododermatitis. Histologically, the affected joints and tendons typically contained severe inflammation with exudates of fibrin, necrotic heterophils and colonies of bacteria (Fig. 1B). Amyloidosis of the joint capsule, tendon sheath or liver was noted in some submissions with chronic infections.
Staphylococcus aureus was the most frequent pathogen cultured from the joints in this case series (48 submissions), followed by E. coli (18 submissions), Enterococcus cecorum (4 submissions) and Pseudomonas aeruginosa (1 submission) (Fig. 2). Mixed infections, with two or more pathogens isolated from the joints, were present in 40% of the submissions. Although Pasteurella multocida was isolated occasionally, in each circumstance the flock had been vaccinated against fowl cholera.
S. aureus is a common cause of arthritis, tenosynovitis, septicemia, osteomyelitis, omphalitis and gangrenous dermatitis in poultry. The diagnosis of staphylococcosis is confirmed by culturing S. aureus from the typical lesions. Staphylococci are ubiquitous in the environment and frequently colonize the skin, therefore, damage to the skin barrier may permit entry of bacteria and systemic infection. Immunosuppression due to conditions such as infectious bursal disease or chicken infectious anemia may also predispose to staphylococcosis. Prevention strategies include management practices that enhance host immunity, minimize damage to the skin and feet, and minimize environmental contamination. Staphylococcus infection may also be treated with antibiotics based on the results of sensitivity testing. The antibiotic resistance profile of S. aureus isolated from broiler breeder chickens at the AHL from 2020 to 2022 is summarized in (Fig. 3). AHL
Figure 1. (A) Hock joint from a broiler breeder chicken with bacterial arthritis. The joint lumen contains a yellow, turbid inflammatory exudate. (B) Histopathology of the gastrocnemius tendon (*) with severe tenosynovitis due to S. aureus infection. The tendon sheath contains abundant inflammatory exudate composed of fibrin and necrotic heterophils (arrows). Inset: Colonies of coccoid bacteria (arrowheads) within the exudate. H&E.
Figure 2. Bacterial etiologies of arthritis identified in broiler breeder chickens submitted for postmortem to the AHL in 2022. *P. multocida isolates were from vaccinated flocks.
Figure 3. Antibiotic resistance profile of S. aureus isolated from broiler breeder chickens at the AHL from 2020 to 2022.
References
1.Andreason CB. Staphylococcosis. In: Diseases of Poultry, 14th ed. Wiley Blackwell, 2020:995-1003.
2.Shivaprasad HL. Staphylococcosis. In: Manual of Poultry Diseases. AFAS, 2015:374-375.