A bad taste in the mouth
Wednesday 15th December, 2010A bad taste in the mouth - avian diphtheria in hoiho chicks. Rarebits December 2010/YEPT Newsletter December 2010, prepared by Mel Young - Biodiversity Assets Ranger, Coastal Otago Area Office
In November 2010, routine nest checks for breeding yellow-eyed penguins/hoiho were carried out at locations within the Boulder Beach complex, southern Otago Peninsula. At the northern end of the breeding area, chicks were noticeably bald and lethargic and, on handling, many had diphtheritic lesions in the mouth (diphtheritic stomatitis, avian diphtheria). Using the protocol for disease management, chicks and the attending adult were swabbed in the mouth and samples were sent to the New Zealand Wildlife Health Centre at Massey University in Palmerston North. In addition, authorisation from the local vet was given to treat chicks with noticeable lesions inthe mouth using broad spectrum antibiotics. Rehydration was also given via a feeding tube to up to 10% of chick bodyweight. Given the aggression of attending adult birds at the nest, nests received varying levels of treatment to accommodate the level of disturbance that was deemed acceptable.
Additional requests for samples from New Zealand Wildlife Health Centre included cloacal swabs, sections of oral lesions in both formalin and in a plain vial for DNA. Viral swabs were also provided by ESR in Wellington to determine the viral agent in early cases. It is thought that the diphtheritic lesions are a secondary infection, striking after an unknown viral agent takes effect. Unable to eat, chicks often die from renal failure or starvation. Diphtheria has been known to affect hoiho chicks on the Otago Peninsula particularly since the disastrous season in 2002, again in 2004, and to a lesser extent in 2006. With a poor season also recorded in 2008 due to extreme weather events and poor foraging conditions, 2010 is shaping up to be yet another poor season and confirms that this biennial disturbance to breeding is not going away.
Populations of hoiho in the Catlins and in North Otago have also had some early losses of chicks, and diphtheria has been suspected in a few of these cases. At Boulder Beach, by early December approximately 30% of the chicks have died at this breeding location, with a further 30% responding to the treatments given. Reports of the disease have been received from other locations on the Otago Peninsula and treatments have been given by field staff with some success. Refinement of our field technique for treating chicks continues and current diagnostic results are pending.
Diphtheritic lesions in the mouth of a hoiho chick from the Otago Peninsula (Photos courtesty of Mel Young).