Protothecosis in four dogs in New Zealand

ABSTRACT

Case histories

Medical records of four dogs diagnosed with protothecosis in New Zealand were reviewed. The dogs were aged between 4 and 9 years and three of the four dogs were female. Breeds were one Labrador, one Miniature Schnauzer and two crossbreeds. The reasons for initial veterinary evaluation were a cough and opaque appearance of the right eye (Case 1), diarrhoea (Cases 2 and 3), and cutaneous disease (Case 4).

Clinical findings

The ocular signs were characterised by panuveitis, retinal detachment and secondary glaucoma. Gastrointestinal signs included chronic haemorrhagic diarrhoea due to colitis. Three cases had disseminated infection and developed both bilateral, blinding, ocular disease and chronic gastrointestinal disease. Cutaneous signs consisted of draining fistulae over the olecranon, multifocal cutaneous nodules, and ulceration and tracts of the foot pads. Disseminated protothecosis was confirmed by histopathology of biopsied ocular tissues in Cases 1 and 2 and by gastrointestinal biopsies in Case 3. Prototheca spp. were also identified in cytological specimens from Cases 1 and 4 and recovered by culture in Cases 2 and 4. Cutaneous protothecosis was diagnosed in Case 4 initially by cytology and histopathology of skin lesions, and Prototheca zopfii was confirmed by PCR of cultured organisms.

Treatment and outcome

Prior to diagnosis of protothecosis, a variety of treatments were prescribed to treat the gastrointestinal and ocular signs. After diagnosis, only Cases 2 and 4 received medication aimed at treating the protothecal infection, which was itraconazole in both cases. Following the progression of clinical signs and concerns about quality of life, all four dogs were euthanised.

Diagnosis

Disseminated protothecosis in three dogs, cutaneous protothecosis in one dog.

Clinical relevance

Canine protothecosis is rarely reported, despite the ubiquity of the causal algae, and the disease usually carries an extremely grave prognosis when infection is generalised. In New Zealand, protothecosis should be considered as a differential diagnosis in dogs with panuveitis, chorioretinitis or retinal detachment, colitis, or nodular, ulcerative or fistulating cutaneous lesions.

KEYWORDS:

• Prototheca
• protothecosis
• panuveitis
• chorioretinitis
• retinal detachment
• cutaneous nodules
• colitis
• foot pad ulceration

Acknowledgements

The authors thank veterinarians Felicity Morris, Estelle Louarduzzi, Ivan Aleksic, Peter Collinson, Amy O’Sullivan, David Kettles, Angela Schumacher and all veterinarians involved in the clinical care of dogs. The authors also thank the Ministry for Primary Industries, Massey University, Gribbles Veterinary and New Zealand Veterinary Pathology Ltd. for their diagnostic work, and Marnie Ford (Animal Eye Care, Melbourne, Australia) for the image reproduced in this article.

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes

1 R. Malik, University of Sydney, Sydney, Australia