Inter-relações entre os ciclos de transmissão do Trypanosoma cruzi no município de Bambuí, Minas Gerais, Brasil

Abstract

. This study examines recent relationships between domestic and sylvatic transmission cycles of T. cruzi in the county of Bambuí, MG, Brazil. In the late l930s, Panstrongylus megistus was found in 75% of houses. Subsequently, Triatoma infestans became the predominant species, found in 20% of urban households and in more than 60% of periurban homes. With intense insecticide control campaigns between l956 and l969, T. infestans was eradicated from the county, transmission of Chagas' disease to man was interrupted, and P. mesgistus appeared in rural residences. Samples of T. cruzi isolated by xenodiagnosis and hemoculture from 43 opossums (Didelphis albiventris) captured in both peridomiciliary and sylvatic areas were characterized by isoenzyme analysis and -regardless of isolation method -were found to present the Z1 zymodeme profile. Through the "Chagas' Disease Epidemiological Surveillance Program", from August l986 to December l988, 154 specimens of P. megistus were captured by the local population in both peridomiciliary and intradomiciliary environments, of which 9.8% were infected with T. cruzi. In isoenzyme analyses of l3 T. cruzi strains isolated from these triatomines, six were found to be of the Z1 zymodeme (sylvatic transmission cycles) and seven were found to be of the Z2 zymodeme (domestic transmission cycle). The capture of P. megistus specimens in intradomiciliary environments that were naturally infected with parasites of both cycle types indicates an overlap of transmission cycles of Chagas' disease in the county of Bambuí. Further evidence for the interrelationship of the two cycles was provided by the isolation of T. cruzi of the Z2 zymodeme from a cat and the participation of the dog as a reservoir of Z1 T. cruzi. The presence of P. megistus in the peridomiciliary environment represents an important link between the sylvatic and intradomestic environments serving as a carrier of Z1 T. cruzi and maintaining the transmission cycles of Z2 T. cruzi in the peridomestic and intradomestic environments thus providing the potential for a gradual reinfestation of the county if the "Epidemiological Surveillance" is interrupted. Key words: Chagas' Disease; Trypanosoma cruzi Infection; Transmission Cycles; Reservoirs; Zymodemes INTRODUÇÃOA infecção chagásica, inicialmente uma enzootia silvestre, transmitida na natureza entre animais e triatomíneos, transformou-se em uma antropozoonose com a intrusão do homem no

Long-term reduction of Trypanosoma cruzi infection in sylvatic mammals following deforestation and sustained vector surveillance in northwestern Argentina

“…Although parasite isolation methods may select for certain strains and lineages of T. cruzi, no lineage selection was recorded among 145 isolates from opossums in spite of using different methods (Fernandes et al, 1991). Experimental infections of Didelphis opossums with TCII were considered less persistent than infections with TCI (Fernandes et al, 1994). In addition, mixed infections with different lineages and sublineages contradict the hypothesis of strict sublineage selection by the host.…”

High-Resolution Melting (HRM) of the Cytochrome B Gene: A Powerful Approach to Identify Blood-Meal Sources in Chagas Disease Vectors

“…A third cycle associated with anthropic environments can occur in several places where domestic animals are kept in sheds near dwellings, called by some authors a peridomestic cycle [5]. However, the epidemiological scenario of Chagas disease is more complex because it can include overlapping cycles [6]–[10], intrusions of wild vectors into human dwellings [11], [12], colonization and re-infestation of new sylvatic vector species after spraying houses [4], [13]–[15], the regular intrusion of wild mammals inside houses [16], house infestation by two vector species [17], etc.…”

First report of Panstrongylus megistus sylvatic focus in municipality of Bambuí, state of Minas Gerais, Brazil

“…3). Although the opossums tested here were not infected, Fernandes et al (1991Fernandes et al ( , 1994 demonstrated that these reservoirs play an important role in the interaction of the parasite's domestic and sylvatic cycles in Bambuí.…”

“…The reduction in triatomine colonies in households is attributed mainly to the extensive vector control program that has been established for decades in Bambuí. However, unlike T. infestans, which is restricted to the household environment in Brazil, P. megistus has a wide distribution in nature and frequently moves between natural ecotopes and dwellings (Dias 1982, Fernandes et al 1994). The low rates of re-infestation (10%) and domiciliary colonies (20%) observed in residences evaluated between [2004][2005][2006][2007][2008][2009] suggest that the sylvatic environment is the main source of household recolonisation.…”