Abstract

Bumblefoot (pododermatitis), often described as the most significant environmental disease of captive penguins, is commonly due to excessive pressure or trauma on the plantar surface of the avian foot resulting in inflammation or necrosis and causing severe swelling, abrasions, or cracks in the skin.^2-6 Unnoticed lesions left untreated, can progress into severe bacterial infections resulting in lameness, abscesses, osteomyelitis, and septicemia.^1-2,4

Although not previously evaluated in penguins, contributing factors for bumblefoot are thought to be similar to those initiating the condition in raptors and poultry. These include substrate, body weight, and lack of exercise.⁴ The primary purpose of this retrospective study was to evaluate variables potentially contributing to the development and duration of plantar lesions in our population of African penguins (Spheniscus demersus) over the past eight years including: weight, age, sex, season, activity, and substrate. The acquired data will be utilized to generate recommendations for preventing the formation of clinical bumblefoot cases in aquarium-maintained penguins.

In our population of African penguins, there does not appear to be a significant relationship between the animal's age or time of year for the development of lesions, but penguins spending greater than 50% of their time swimming while on exhibit developed plantar lesions significantly less often than penguins primarily standing on the land portion of the exhibit or with inconsistent activity patterns (swim 21.2%, standing 34.2%, inconsistent activity patterns 41.5%).

Upon further investigation, a significantly higher percentage of the affected population were consistently observed standing on the smooth concrete portion of the exhibit compared to the metal grate portion (smooth concrete = 91.4%, grates = 6.52%, other = 2.08%). Additionally, penguins with a preference for smooth concrete sites versus grates on exhibit developed lesions that required treatment for a significantly longer duration of time despite identical treatment protocols (concrete = 43.6 days and grates = 32.8 days).

Results also indicate that male birds develop significantly more plantar lesions than females (males = 58.8%, females = 45.9%) in our population of African penguins. Penguins weighing between 3.51-4.0kg develop plantar lesions significantly more often than penguins weighing between 2.5-3.5kg (2.5-3.5kg = 54.9% and 3.51-4.0kg = 73.6%), and since male penguins ordinarily weigh significantly more than females (males = 3.5kg and females = 2.9kg), weight is likely a contributing factor in the development of lesions in males compared to females.

Recommendations for minimizing the formation of plantar lesions in African penguins include training penguins for monthly foot examinations, and replacing smooth surfaces on exhibit with surfaces that provide variable degrees of pressure and texture on the feet. For example, the African penguin exhibit at Mystic Aquarium was recently renovated replacing most of the smooth concrete with cobble stones, and although adequate sample size is currently lacking for these data, preliminary results reveal that a lower percentage of penguins are developing plantar foot lesions in the newly renovated exhibit at the same point in time as the previous year in the old exhibit (new exhibit = 25.9%, old exhibit 2008 = 88.5%).

Acknowledgements

The authors thank the penguin husbandry staff at Mystic Aquarium for their consistent hard work and dedication in the surveillance and treatment of foot lesions identified in the African penguin collection. The authors would also like to thank Amy Lakatos for her preliminary data which were utilized in this study and Aliya Wilson for her assistance in developing ideas for this study.

References

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3.  Redig PT. 1987. Treatment of bumblefoot and the management of aspergillosis and various other problems commonly seen in raptors. Proc. 1st Intl Conf Zoo & Avian Med; Pp 309-321.

4.  Reidarson TH, McBain J, Burch L. 1999. A novel approach to the treatment of bumblefoot in penguins. J Avian Med Surg 13:124-127.

5.  Remple JD. 2006. A multifaceted approach to the treatment of bumblefoot in raptors. J Exotic Pet Med 15:49-55.

6.  Stoskopf MK, Beall FB. 1980. The husbandry and medicine of captive penguins. Proc Am Assoc Zoo Vet; Pp. 81-96.