G.O. Fulgêncio; F.A.B. Viana
Ophthalmology Section, School of Veterinary Medicine, Federal University of Minas Gerais, Belo Horizonte City, Minas Gerais State, Brazil
Trypanosomiasis is a zoonotic disease caused by protozoans of the genus Trypanosoma that typically inhabit tropical and subtropical climates. Trypanosoma evansi infects only animals and causes a disease known as "surra". Infected dogs present primarily with lymphadenopathy, malaise, weight loss, hyperthermia and anemia. Conjunctivitis, blepharitis and uveitis have also been described. In this report we describe ocular lesions in two dogs naturally infected with T. evansi following thorough clinical and ophthalmic examinations. Both dogs presented with weight loss, lymphadenopathy, fever and lethargy. One dog developed bilateral uveitis with hyphema, hypopyon, and second one, corneal edema, vascularization and phthisis bulbus in both eyes. Funduscopic evaluation was complicated due to decreased ocular tissue transparency and impaired pupil dilation. Blood cell counts, determination of total plasma protein and renal profile were performed. Serologic exams common to leishmaniasis, babesiosis and ehrlichiosis were performed. Abdominal radiographs and ocular and abdominal ultrasonography were also obtained. One animal died and the second euthanized. Necropsy was performed on the euthanized dog and ocular bulbs and esophagus, heart, spleen, liver, kidney, lymph node and intestinal samples were examined histological. Although serological exams were negative, hypergammaglobulinemia, anemia and thrombocytopenia were diagnosed and the presence of flagellated organisms of Trypanosoma morphology were confirmed to be T. evansi. A generalized internal organ atrophy was observed in addition to atrophy of the ocular bulbs. Parasites were not identified histological in the myocardium, iris nor ciliary body tissues infiltrated by inflammatory cells. Blepharospasm and conjunctivitis were not observed. Severe inflammation associated with eye infections can also result in the cessation of aqueous humor production; frequently seen in endophthalmitis and chronic uveitis that can cause the development of phthisis bulbus. Fibrinous exudates also contribute to ocular bulb atrophy resulting in 'shrunken eye' which is common following trypanosome infections causing Chagas' disease, leishmaniasis, and ehrlichiosis, suggesting that these diseases should be included in a differential diagnosis of trypanosomiasis in dogs living or coming from endemic areas.