Chagas disease in a naturally-infected dog from Northeast Brazil: a case report.

Background: Dogs are the main domestic reservoir host of the parasite Trypanosoma cruzi, the causative agent of Chagas disease, and they are considered sentinel animals for the detection of new cases of human infection. Canis familiaris is also a well-established experimental T. cruzi infection model, but little is known about the progression of Chagas disease in naturally-infected dogs, especially during the acute phase in these hosts. Triatomine species infected with discrete typing units (DTUs) I, II and III of T. cruzi have been previously found in many of the municipalities of the state of Rio Grande do Norte. The current study describes the clinical, hematological, biochemical, cardiological and parasitological characteristics of a single dog during the acute phase of its naturally-acquired T. cruzi infection, and characterizes the isolate obtained from this individual host using biological, molecular and phylogenetic methods.
Results: A  juvenile dog exhibiting discomfort during defecation, itchy skin, and enlarged popliteal lymph nodes showed a prolonged period of patent parasitemia, with normocytic and hypochromic anemia. In addition, cardiac damage was suggested by high concentrations of the biomarkers cardiac troponin I and NT-ProBNP, as well as Doppler echocardiography, which showed qualitative segmental hypokinesia. The parasites isolated from this individual canine were genotyped, using three molecular markers and phylogenetic analysis, as the DTU TcIII. First detected in sylvatic environments, our current observations also demonstrate the presence of this DTU in domestic/ peridomestic locations.
Conclusions: The cardiac alterations that we observed in a naturally-T. cruzi-infected dog contribute to expanding our knowledge of both Chagas disease in Canis familiaris, and the epidemiological scenario in locations where Triatoma brasiliensis is the main triatomine vector of T. cruzi.
Competing Interests: Declarations. Ethics approval and consent to participate: This study was approved by Ethics Committee on the Use of Animals/UFRN, protocol no.134.062/2018 and no.138.066/2018. The dog owner was informed about the research and gave written informed consent before samples were collected. Consent for publication: Not applicable. Competing interests: The authors declare no competing interests.
(© 2025. The Author(s).)