Dispersal patterns of Trypanosoma cruzi in Arequipa, Peru

Urban vectors of Chagas disease in the American continent: A systematic review of epidemiological surveys

BACKGROUND

Chagas is a complex and multidimensional socio-environmental health phenomenon, in which different components converge and interact. Historically, this disease was associated with insect vectors found in the rural environment. However, in the Americas, we are currently facing a new paradigm, in which different scenarios allow maintaining the vectorial transmission of the parasite through triatomine populations that either occasionally enter the dwellings or colonize urban environments.

METHODOLOGY/PRINCIPAL FINDINGS

Records of scientific reports available in the PubMed and LILACS search engines were retrieved, using three criteria according to the main triatomine genera of epidemiological importance and to the general scientific production on Chagas disease in urban contexts. Results showed that records on the occurrence of vectors in urban dwellings began to increase in the last three decades. Results also showed that the main species of triatomines collected inside dwellings (18 in total) belong mainly to the genera Triatoma and Panstrongylus, with most species (16/18, 88.8%) infected with the parasite, and that infestation of triatomine species occurs in all types of cities (small, medium and large, including megalopolises), from Argentina to the USA.

CONCLUSIONS/SIGNIFICANCE

Urban Chagas represents a new challenge that adds a different dimension to the problem of Chagas disease due to the particular characteristics of the lifestyle in urban agglomerates. The new scenario will require adaptations of the programs of control of vector to this shift from rural to urban settlements.

Microevolution and subspecific taxonomy of Trypanosoma cruzi

Trypanosoma cruzi, the agent of Chagas disease, is a highly polymorphic species, subdivided into 6 main evolutionary lineages or near-clades (formerly discrete typing units or DTUs). An additional near-clade (TC-bat) has recently been evidenced. This pattern is considered to be the result of predominant clonal evolution (PCE). PCE is compatible with occasional mating/hybridization, which do not break the prevalent pattern of clonal evolution, the main trait of it being the presence of Multigene Bifurcating Trees (MGBTs) at all evolutionary levels ("clonal frame"). The development of highly resolutive genetic (microsatellites*) and genomic (sequencing and multi-single nucleotide polymorphism {SNP}* typing) markers shows that PCE also operates at a microevolutionary* level within each of the near-clades ("Russian doll pattern"), in spite of occasional meiosis and hybridization events. Within each near-clade, one can evidence widespread clonal multilocus genotypes*, linkage disequilibrium*, Multigene Bifurcating Trees and lesser near-clades. The within near-clade population structure is like a miniature picture of that of the whole species, suggesting gradual rather than saltatory evolution. Additional data are required to evaluate the stability of these lesser near-clades in the long run and to evaluate the need for an adequate nomenclature for this microevolutionary level.

Molecular and Clinical Aspects of Chronic Manifestations in Chagas Disease: A State-of-the-Art Review

Chronic manifestations of Chagas disease present as disabling and life-threatening conditions affecting mainly the cardiovascular and gastrointestinal systems. Although meaningful research has outlined the different molecular mechanisms underlying Trypanosoma cruzi’s infection and the host-parasite interactions that follow, prompt diagnosis and treatment remain a challenge, particularly in developing countries and also in those where the disease is considered non-endemic. This review intends to present an up-to-date review of the parasite’s life cycle, genetic diversity, virulence factors, and infective mechanisms, as well as the epidemiology, clinical presentation, diagnosis, and treatment options of the main chronic complications of Chagas disease.

In the heart of the city: Trypanosoma cruzi infection prevalence in rodents across New Orleans

BACKGROUND

Trypanosoma cruzi - the causative agent of Chagas disease - is known to circulate in commensal pests, but its occurrence in urban environments is not well understood. We addressed this deficit by determining the distribution and prevalence of T. cruzi infection in urban populations of commensal and wild rodents across New Orleans (Louisiana, USA). We assessed whether T. cruzi prevalence varies according to host species identity and species co-occurrences, and whether T. cruzi prevalence varies across mosaics of abandonment that shape urban rodent demography and assemblage structure in the city.

METHODS

Leveraging city-wide population and assemblage surveys, we tested 1428 rodents comprising 5 species (cotton rats, house mice, Norway rats, rice rats and roof rats) captured at 98 trapping sites in 11 study areas across New Orleans including nine residential neighborhoods and a natural area in Orleans Parish and a neighborhood in St. Bernard Parish. We also assayed Norway rats at one site in Baton Rouge (Louisiana, USA). We used chi-square tests to determine whether infection prevalence differed among host species, among study areas, and among trapping sites according to the number of host species present. We used generalized linear mixed models to identify predictors of T. cruzi infection for all rodents and each host species, respectively.

RESULTS

We detected T. cruzi in all host species in all study areas in New Orleans, but not in Baton Rouge. Though overall infection prevalence was 11%, it varied by study area and trapping site. There was no difference in prevalence by species, but roof rats exhibited the broadest geographical distribution of infection across the city. Infected rodents were trapped in densely populated neighborhoods like the French Quarter. Infection prevalence seasonally varied with abandonment, increasing with greater abandonment during the summer and declining with greater abandonment during the winter.

CONCLUSIONS

Our findings illustrate that T. cruzi can be widespread in urban landscapes, suggesting that transmission and disease risk is greater than is currently recognized. Our findings also suggest that there is disproportionate risk of transmission in historically underserved communities, which could reinforce long-standing socioecological disparities in New Orleans and elsewhere.