DOGS AS SOURCE OF TRYPANOSOMA CRUZI INFECTION IN RURAL AREAS OF THE CHACO REGION (PLURINATIONAL STATE OF BOLIVIA)

INTRODUCTION: Chagas disease continues to be an important sanitary problem in the Americas, even if the risk of transmission in Latin American endemic countries has been reduced by safer blood transfusions and vector-control measures applied (WHO, 2010, 75-9). Trypanosoma cruzi, the etiological agent of this anthropo-zoonosis, has been detected in more than 100 mammal species (Barretto, 1968, Rev Brasil Biologia, 28:481-94), but the role played by each species in the dispersion/maintenance of the parasite in each area of its occurrence is not completely known (Cortez et al., 2006, Expl Parasitol, 14:305-13). This is true for Bolivia, where only few studies on this topic have been undertaken (Albarracin-Velzaga, 1999, Rev Saude Publica, 3:230-6; Medrano-Mercado, 2008, Mem Inst Oswaldo Cruz, 103:423-30), and where a serosurvey carried out in Chuquisaca and Santa Cruz Dep.s detected antibodies in ≈70% of people (Gabrielli et al., 2008, Parassitologia, 50:85). MATERIALS AND METHODS: Aim of this paper is to evaluate the role of dogs as source of infection for kissing bugs vectors and, indirectly, for humans living in two rural Bolivian communities (Ivamirapinta and Bartolo). By venepuncture, blood samples were drawn from 101 dogs living around people resident in study areas, and used to prepare Giemsa stained thick and thin smears, and to impregnate (300-500μL) filter papers. From these dried blood spots DNAs were extracted and a region of 330bp from kDNA was PCR-amplified (Enriquez et al., 2013, Acta Trop J, 126 (3): 211-217); amplicons were sequenced, and sequences were BLAST compared with available sequences to confirm the species. RESULTS: As expected, smears proved negative to the microscopic analysis whereas 24 blood spots (23.7%) were positive to T. cruzi (8/48 in Ivamirapinta and 16/53 in Bartolo). The presence of the parasite in the bloodstream of ≈24% examined dogs suggests that they can play an important role as source of infection for kissing bugs in endemic rural areas. CONCLUSIONS: This result disagrees with data collected in the city of Cochabamba (Medrano-Mercado et al., 2008, Mem Inst Oswaldo Cruz, 103:423- 30), but it is in total agreement with studies carried out in rural areas of N-W Argentina, where dogs proved to be a source of infection for bugs more important than cats, humans and chicken (Gurtler et al., 2007, Parasitology, 134:69-82). In rural areas, the environment offers more opportunity for kissing bugs to feed on dogs, and general conditions of dogs (as malnutrition) maybe contribute to poorly control the parasite reproduction in the bloodstream. So, this animal may be the main domestic reservoir of T. cruzi and a risk factor for parasite transmission, as demonstrated by the report in this host of all the discrete typing units of T. cruzi identified in humans (Ramírez et al., 2013, Vet Parasitol, 196:216-9). Therefore, improved detection of T. cruzi infections in dogs is relevant for risk assessment. Local veterinaries should pay attention to the problem, and check dogs regularly for this parasite.