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Assessment of Parasitological Behaviour, Clinical Changes and Serology during Experimental Infection of a Calf with a Venezuelan Isolated of Trypanosoma evansi: A Preliminary Study

Marcello Salvatore Rossi Spadafora, Pedro María Aso and †Francisco García

Background: Trypanosoma evansi is the agent of trypanosomosis that affect domestic and wild animals causing anaemia, degeneration, necrosis and inflammatory processes. This disease is of great concern because it produces growth retardation, loss of body weight, low production of animal proteins and diminished fertility and traction power. On the other hand could be become in an emergent zoonosis affecting human beings as it has been recently described in India and Vietnam. Due in Venezuela experimental infections of cattle with T. evansi have been referred as "benign", the aim of this study was to assess the effect of T. evansi on parasitological, clinical and serological parameters during experimental infection of a bovine.
Methods: The evolution of the experimental infection of one bovine with T. evansi EcF1991 was assessed at parasitological, serological and clinical level for 30 days by measuring levels of parasitemia, IgG anti-T. evansi bovine antibodies by ELISA, body temperature, packed cell volume and levels of haemoglobin.
Results: Infected bovine developed a fluctuating low-level and often cryptic parasitaemia without fluctuations in body temperature. Parasitaemia was represented by four main peaks at days 1, 10 and 17. Although the two first parasitaemia peaks occurred with only a slight decreasing of haematocrit and increasing of IgG anti-T. evansi levels, beginning of third parasitaemia peak was accompanied by a marked decrease on haematocrit and haemoglobin values reaching levels 60% and 64% below of preinfection values respectively. The most marked diminution of haematocrit was observed after third parasitaemia peak (day 17). This decreasing trend of haematocrit was accompanied by a pronounced increasing on IgG levels against T. evansi during infection.
Conclusion: Results herein presented reports for the very first time the evolution of some clinical, parasitological and serological parameters during T. evansi infection of a bovine and confirm molecular studies about role of Venezuelan bovines as susceptible and natural hosts of T. evansi as it has been reported in Africa, Asia and South America. In addition presents an indirect ELISA technique for detection of bovine IgG antibodies to T. evansi suggesting that more research is needed to define the clinical, pathological and immunological profiles of these infections in bovines from Venezuela.