What is your diagnosis? Systemic lymphadenopathy and blindness in a dog from Italy

Protothecosis in four dogs in New Zealand

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.

[Disseminated protothecosis with ulcerative granulomatous colitis in a Rhodesian Ridgeback from Germany]

A 10-month-old male Rhodesian Ridgeback was presented to the Clinic of Small Animal Medicine, LMU, Germany, with a 6-month history of chronic diarrhea and hematochezia. The dog lived in Germany and had never traveled abroad. Complete blood count and serum biochemistry performed by the referring veterinarian revealed neutrophilia, hyperkalemia, and hyponatremia, with a basal cortisol of 4.3 µg/dl, which excluded hypoadrenocorticism. Since antibiotic treatment had not resulted in any improvement, a 2 week course of prednisolone administration had been initiated, leading to a marked deterioration of intestinal signs and a significant weight loss of 6 kg. At the time of referral, the patient was markedly emaciated, dehydrated, hypovolemic and had a rectal temperature of 39.6 °C. Abdominal ultrasound showed a thickened and irregular colonic wall. On colonoscopy, an irregular colonic mucosa with ulcerations was observed. Histopathologic examination revealed an ulcerative granulomatous colitis, and on Periodic acid-Schiff reaction (PAS) numerous organisms consistent with Prototheca spp. were identified. Prototheca zopfii infection was confirmed by culture and MALDI-TOF MS. In order to test for an underlying immunodeficiency, immunoglobulin levels in serum were determined. IgM was decreased, while IgG and IgA levels were within the reference interval. Due to deterioration of general condition, grave prognosis and costs of a treatment trial, the patient was euthanized one week later, and necropsy was performed. Prototheca spp. were detected on histopathologic examination in the lymphnodes, however not in the eyes or the central nervous system. Protothecosis should be considered an differential diagnosis in dogs with chronic diarrhea and ulcerative granulomatous colitis even in dogs living in Germany. Histopathologic examination of colonic biopsies with special stains such as PAS is recommended in every dog with signs of chronic large bowel disease in order to avoid missing this rare infectious disease.

Evidence of a Prototheca Zopfii Genotype 2 Disseminated Infection in a Dog with Cutaneous Lesions

Protothecosis is a disease caused by saprophyte aerobic unicellular algae belonging to the genus Prototheca. In dogs, it mainly occurs as a disseminated form, with initial clinical manifestations often referable to the gastrointestinal tract, followed by typical ocular and neurological signs. So far, Prototheca zopfii genotype 2 infection has been reported in severe forms of disseminated protothecosis, while in dogs has never been associated with cutaneous forms. In this study, we describe a case of Prototheca zopfii genotype 2 infection in a dog characterized by nodular and ulcerative dermatitis and with evidence of dissemination. In December 2015, a 5-year-old unneutered male English Setter dog was presented with a 4-month history of footpads ulcerations and multifocal nodular lesions (3-5 cm diameter) on both front limbs. Cytological examination of the aspirated fluid collected from all nodules revealed the presence of sporangic forms compatible with Prototheca spp. organisms. Suspected Prototheca spp. colonies were isolated from the aspirated fluid and identified as Prototheca zopfii genotype 2 by molecular methods. Few days after the visit, the patient developed serious neurological and ocular signs, and the owners elected humane euthanasia. To the authors' knowledge, this case could represent the first report of a disseminated Prototheca zopfii genotype 2 infection associated with cutaneous lesions in a dog. This study underlines the importance of considering Prototheca zopfii genotype 2 infection in the differential etiological diagnosis of nodular and ulcerative dermatitis in dogs.