Serial heart rate changes in rats inoculated by conjunctival instillation of Trypanosoma cruzi obtained from bug...

The cardiac effects of experimentally induced myocarditis, when the parasite is obtained from mouse blood, are well known. However, the consequences of the infection when the parasites are obtained from bug faeces are less well defined. In the present investigation, we have used the "Y" strain of Trypanosoma cruzi, which was maintained in Rhodnius prolixus by repeated passages in mice. The faeces of 30 infected bugs were collected, the number of parasites counted and 4,000 parasites inoculated by the conjunctival route in 60 rats. Twenty-nine other rats received faeces from noninfected bugs (sham-inoculated controls) and 40 were used as normal controls. The heart rate of the three groups of animals was recorded under general anesthesia with ether. The heart rate, at day 0 pre-inoculation, was similar in the three groups of animals (

379 +/- 27 beats/min Mean +/- SD; Sham-inoculated: 366 +/- 31; Infected: 351 +/- 29) (p> 0.05). In the infected animals, the mean heart rate began to increase significantly by day 12 following infection (375 +/- 31), reaching the highest values between days 18 (390 +/- 33) and 21 (403 +/- 33) and returned to baseline by day 30 (359 +/- 28) (p< 0.05). The heart rate changes were statistically different from those observed in the sham-inoculated controls and in the control animals. Therefore, these heart rate changes were provoked by the Trypanosoma cruzi-induced infection. Thus, it appears that irrespective of the source of the parasite and route of inoculation, Trypanosoma cruziacute infection provokes a transient sinus tachycardia.