Background: Trypanosomosis is a disease caused by a flagellate protozoan known as Trypanosoma evansi, transmitted by
hematophagous insects. It parasites showed a large diversity of mammalian hosts. Dogs may show clinical changes such as
weight loss, progressive weakness, anorexia, anemia, intermittent fever, conjunctivitis, swelling of limbs and increased of
superficial lymph nodes. Treatment of trypanosomosis relies on the use of diminazene aceturate which is effective for the
treatment of disease in infected animals. However, a single dose of drug are not effective for horses, mules and dogs, since drug
neither cross the blood-brain barrier or has insufficient doses to control the T. evansi infection. Therefore, the present study
aimed to report the curative efficacy of a new therapeutic protocol, based on diminazene aceturate, for dogs infected with T.
evansi.
Case: The treatment against trypanosomosis was performed in a dog, male, two years old, from the municipality of Uruguaiana,
RS, Brazil.. The animal showing clinical signs such as apathy, vomit, increase of left submandibular lymph node, edema of the
left face and change of gait in the hind limbs when it was evaluated by veterinarians. The hematological and biochemical
parameters revealed normocytic-hypochromic anemia, thrombocytopenia, hyperglobulinemia and hypoalbuminemia.
Trypomastigotes of T. evansi were identified in blood smears stained by panoptic method. The parasitism by T. evansi was
confirmed by blood inoculation in two rats (xenodiagnosis) and by PCR T. evansi-specific. The canine was treated with
diminazene aceturate (intramuscular injection) using a dose of 3.5 mg kg-1 for 5 days at 24h of intervals. After treatment the dog
showed clinical signs of health improvement, and clinical signs disappeared after the seventh day of treatment. The parasite
was not found in blood smears after the third day of treatment and PCR was negative on days 30 and 50 post-treatment. During
the treatment signs of drug intoxication were not observed, as well as hepatic and renal functions were not affected. The animal
showed normal biochemical and hematological parameters after 30 days of treatment.
Discussion: In this study, the treatment tested was effective, leading to the cure of the disease. Previously, the same protocol
was used for cats experimentally infected with T. evansi, obtaining 85.7% (6/7) of curative efficacy. In a comparative study of
doses of diminazene aceturate in rats infected with T. evansi, inefficiency and death of rats treated with a single dose of 3.5 and
7.0 mg kg-1 were observed. In contrast, the cure in rats occurred when animals received a dose of 3.5 and 7.0 mg kg-1 during five
consecutive days. The return of the parasitemia after treatment may be related to the impossibility of the medicament pass
through the blood-brain barrier or the doses is insufficient. Our data reveal that five-dose protocol obtained higher efficiency
because it provided greater passage of drug molecules through blood-brain barrier, which could eliminate the parasite from
brain. After treatment, all clinical signs disappeared, biochemical and hematological parameters returned to normal levels,
allowing us to conclude that this new protocol tested was effective to cure of this disease in dogs.
