Ocular protothecosis in a dog

Hyphema: Considerations in the Small Animal Patient

Classification, diagnosis, and treatment of hemorrhage into the anterior chamber of the eye, or hyphema, can be a challenging and frustrating process for many practitioners, especially in emergency situations. This review outlines an inclusive list of causes, diagnostics, and treatments for traumatic and nontraumatic hyphema in both canine and feline patients. The review is tailored to small animal practitioners, especially in emergency practice, and is designed to provide concise but thorough descriptions on investigating underlying causes of hyphema and treating accordingly.

Algal Meningoencephalitis due toProtothecaspp. in a Dog

A 6-year-old Boxer was examined because of progressive neurologic signs, with severe hindlimb ataxia and head tilt on presentation. There was no history of diarrhea or vomiting. MRI of the brain revealed multifocal ill-defined T1-enhancing lesions affecting the cerebrum, brainstem, and cervical meninges, without associated mass effect. Meningoencephalitis was considered the most likely diagnosis. Multiple algae were observed on the cytology of the CSF and were most consistent withProtothecaspp. Antiprotozoal treatment was denied by the owners, and 5 weeks after diagnosis, the dog was euthanized due to progression of the neurologic deficits, and a necropsy was performed. Histological changes in the brain were compatible with severe multifocal protothecal meningoencephalitis. The specificProtothecaspecies was not identified. The gastrointestinal tract was unremarkable on histology. According to this report,Protothecaspp. should be included in the differentials for neurological deficits even in the absence of gastrointestinal signs.

Prototheca wickerhamii infection of a corneal graft

Algae are generally noninfectious agents in mammals, with few known pathogenic algae. Prototheca is an achlorophylic nonphotosynthetic algae, globally ubiquitous, and readily isolated from rivers, lakes, ponds, and soil. Although canine and bovine protothecosis have been reported more widely, infections in humans are rare, particularly in patients with an intact immune system. The majority of protothecal infections in humans is associated with Prototheca wickerhamii. We report an unusual case of P. wickerhamii infection in an immunocompetent corneal transplant patient.

Protothecosis in 17 Australian dogs and a review of the canine literature

Systemic protothecosis was diagnosed in 17 Australian dogs between 1988 and 2005. There was a preponderance of young-adult (median 4 years), medium- to large-breed dogs. Females (12/17 cases) and Boxer dogs (7 cases, including 6 purebreds and one Boxer cross) were over-represented. Sixteen of 17 dogs died, with a median survival of four months. A disproportionate number of cases were from coastal Queensland. In most patients, first signs were referable to colitis (11/17 cases), which varied in severity, and was often present for many months before other symptoms developed. Subsequent to dissemination, signs were mostly ocular (12 cases) and/or neurologic (8 cases). Two dogs had signs due to bony lesions. Once dissemination was evident, death or euthanasia transpired quickly. Prototheca organisms had a tropism for the eye, central nervous system (CNS), bone, kidneys and myocardium, tissues with a good blood supply. Microscopic examination and culture of urine (5 cases), cerebrospinal fluid (CSF;1 case), rectal scrapings (4 cases), aspirates or biopsies of eyes (5 cases) and histology of colonic biopsies (6 cases) as well as skin and lymph nodes (2 cases) helped secure a diagnosis. Of the cases where culture was successful, P wickerhamii was isolated from two patients, while P zopfii was isolated from five. P zopfii infections had a more aggressive course. Treatment was not attempted in most cases. Combination therapy with amphotericin B and itraconazole proved effective in two cases, although in one of these treatment should have been for a longer duration. One surviving dog is currently still receiving itraconazole. Protothecosis should be considered in all dogs with refractory colitis, especially in female Boxers.

Susceptibility and features of the ultrastructure of Prototheca zopfii following exposure to copper sulphate, silver nitrate and chlorexidine

One of the most important forms of the occurrence of protothecosis is bovine mastitis. Studies on the "in vivo" and "in vitro" susceptibility to antimicrobials have shown that the microorganism is resistant to most of them. Looking for alternative treatments this study aimed to study the susceptibility to copper sulphate (which has an important algicide effect) and silver nitrate (used in dairy cattle breeding for the cauterization of mammary glands) and also to chlorexidine (an important post-dipping anti-septic used in dairy practice), and the effect of these antimicrobials in the ultrastructure of Prototheca zopfii before and after the exposure to these drugs. The "in vitro" susceptibility tests to chlorexidine, silver nitrate and copper sulphate of the strains of Prototheca zopfii for the determination of their minimal microbicidal concentrations (MMC), were performed using the tube dilution method in Sabouraud dextrose broth and evaluation of colony growth after plating in Sabouraud dextrose agar. The MMCs of chlorexidine, copper sulphate and silver nitrate of the 50 strains tested were 0.01%, 0.1% and 0.3%, respectively. The tubes containing the material used in the antimicrobial susceptibility tests were prepared for the examination in an electron microscope. The untreated controls of P. zopfii showed a similar ultrastructural appearance with the typical characteristics of the microorganism. Cells exposed to silver nitrate showed changes suggesting thickness of the cell wall. Cells exposed to chlorexidine showed changes suggesting degradation of intra-cellular organelles present in the cytoplasm. P. zopfii treated with copper sulphate showed changes suggesting fibrilation of inner layer of cell wall.

Causes of uveitis in dogs: 102 cases (1989-2000)

Uveitis is one of the most common ocular diseases and one of the most common causes of blindness in dogs. The purpose of this retrospective study was to correlate the signalment, history, clinical signs and ophthalmic findings of dogs with uveitis with the underlying etiology. We conducted a retrospective study of 102 dogs presented to the NCSU-VTH from 1989 to 2000 with clinical signs of uveitis. Medical records of dogs presented for uveitis were reviewed. Dogs were included in the study only if a complete diagnostic work-up database was collected, if sufficient follow-up was documented, and if the uveitis was not secondary to trauma or a hypermature cataract. The mean age +/- SD of all dogs in this study was 6.2 +/- 3.6 years. There were 33 intact and 16 castrated males, and 14 intact and 27 neutered females. Fourteen breeds were represented, with the Golden Retriever (n = 14) most common. Fifty-nine dogs (58%) were diagnosed with idiopathic/immune-mediated uveitis, neoplasia was diagnosed in 25 dogs (24.5%) and 18 dogs (17.6%) were diagnosed with infectious causes of uveitis. Aqueous flare was the most common clinical sign, occurring in 88 dogs (86%). The most common infectious organisms associated with uveitis in the dogs of this study were Ehrlichia canis (n = 7). Lymphosarcoma (n = 17) was the most common neoplasm. In approximately 60% of dogs presenting for uveitis an underlying cause was not found, and a diagnosis of immune-mediated or idiopathic uveitis was made. However, approximately 25% of dogs had ocular and/or systemic neoplasia (with 17% of cases having lymphosarcoma) and 18% with an underlying infectious cause for uveitis. Because of the high percentage of systemic disease associated with uveitis in dogs, extensive diagnostic testing is recommended before instituting symptomatic anti-inflammatory therapy.

Clinical, cytologic and histopathologic manifestations of protothecosis in two dogs

Two cases of sudden onset of blindness associated with ocular protothecosis in dogs are reported. Both were adult, spayed female, mixed-breed dogs that lacked the usual clinical signs of systemic infection with Prototheca species. Physical abnormalities at the time of presentation were limited to the affected eyes which had serous discharge, hyperemic conjunctiva, and aqueous flare. The pupillary light reflexes were slow, and the menace reflexes were absent. Both dogs had glaucoma. Results of complete blood counts and serologic titres for antibodies to Blastomyces dermatitidis and Histoplasma capsulatum were within reference intervals. Protothecosis was diagnosed by cytologic analysis of vitreous humor and was confirmed at necropsy. These two cases were unusual because of their presenting signs and prolonged course of disease progression.

Canine protothecosis

Canine protothecosis remains a difficult condition to manage. The paucity of clinical cases hinders the development of successful treatment strategies. The clinical signs associated with the disease are nonspecific, and the course is so insidious that, by the time a definitive diagnosis is reached, the organism has often disseminated throughout the body. At this point, the condition is beyond treatment, and death occurs owing to failure of any number of organ systems, including the gastrointestinal, cardiovascular, renal, and central nervous systems. It is of some encouragement that the few patients that have undergone aggressive early treatment have survived longer than patients presenting late in the disease course. Nevertheless, the outlook for any dog with protothecosis is grave, and it remains to be determined whether early diagnosis can truly provide a better long-term prognosis. By including protothecosis as a consideration for dogs initially brought in with a history of chronic diarrhea or acute blindness and with a subsequent finding of exudative retinal separation, early diagnosis is possible. This recognition potentially affords the opportunity for an immune status work-up and intervention with increasingly better treatment options.

Metastatic protothecal retinitis in a dog. Electron microscopic observations

Disseminated protothecosis, due to Prototheca wickerhamii, was present in a two-year-old female dog with a nine-month history of hemorrhagic colitis and diarrhea. Shortly thereafter, the dog developed "acute blindness" of the left eye. Euthanasia was done after medical therapy failed to control the disease. Histologically, the eye had multiple microabscesses and necrotic foci containing myriad protothecal organisms under the detached retina. Numerous organisms also were present in the mucosa and walls of the colon. The identification of P. wickerhamii was confirmed by the histologic appearance and immunofluorescent studies. The ultrastructural features of P. wickerhamii also were studied.

Susceptibility of Prototheca species to antifungal agents

Twenty isolates of Prototheca filamenta, Prototheca moriformis, Prototheca stagnora, Prototheca wickerhamii, and Prototheca zopfii were tested for in vitro susceptibility to five commonly used antifungal agents: amphotericin B, 5-fluorocytosine, griseofulvin, miconazole, and nystatin. The results revealed resistance to griseofulvin of all the Prototheca isolates tested and an inhibitory effect on P. filamenta by high 5-fluorocytosine concentrations (minimal inhibitory concentration [MIC] = 12.5 to 100 mug/ml; minimal fungicidal or algacidal concentration [MFC/MAC] = 50 to 100 mug/ml). P. filamenta isolates were also susceptible to miconazole (MIC = 0.1 to 0.5 mug/ml, MFC/MAC = 0.5 to 1 mug/ml); isolates of the other Prototheca species varied in regard to miconazole activity from susceptible to resistant (MIC = 1 - >100 mug/ml, MFC/MAC = 5 - >100 mug/ml). The Prototheca isolates revealed an in vitro susceptibility to the polyene antifungal agents, amphotericin B, and nystatin (MIC = 0.09 to 3.12 mug/ml and 0.19 to 12.5 mug/ml, respectively; MFC/MAC = 0.19 to 25 mug/ml and 0.75 to 25 mug/ml, respectively).

[Generalized protothecosis in a fruit bat (Pteropus lylei)]

Prototheca organisms, histologically resembling Prototheca wickerhamii, were found in a fruit bat as a cause of a massive granulomatous lymphadenitis and splenitis and a widespread granulomatous meningoencephalitis. Focal lesions were also present in the myocardium, in skeletal muscles, and in the kidneys.