Trypanosoma cruzi infection in Triatoma infestans and other triatomines: long-term effects of a control program in rural northwestern Argentina

Background Interruption of domestic vector-borne transmission of Trypanosoma cruzi is still an unmet goal in several American countries. In 2007 we launched a long-term intervention program aimed to suppress house infestation with the main domestic vector in southern South America (Triatoma infestans) and domestic transmission in Pampa del Indio, a resource-constrained, hyperendemic municipality with 1446 rural houses inhabited by Creole and indigenous people, in the Argentine Chaco ecoregion. Here, we assessed whether the 10-year insecticide-based program combined with community mobilization blocked vector-borne domestic transmission of T. cruzi to humans and dogs. Methods We carried out two municipality-wide, cross-sectional serosurveys of humans and dogs (considered sentinel animals) during 2016–2017 to compare with baseline data. We used a risk-stratified random sampling design to select 273 study houses; 410 people from 180 households and 492 dogs from 151 houses were examined for antibodies to T. cruzi using at least two serological methods. Results The seroprevalence of T. cruzi in children aged <16 years was 2.5% in 2017 (i.e., 4- to 11-fold lower than before interventions). The mean annual force of child infection (λ) sharply decreased from 2.18 to 0.34 per 100 person-years in 2017. One of 102 children born after interventions was seropositive for T. cruzi; he had lifetime residence in an apparently uninfested house, no outside travel history, and his mother was T. cruzi-seropositive. No incident case was detected among 114 seronegative people of all ages re-examined serologically. Dog seroprevalence was 3.05%. Among native dogs, λ in 2016 (1.21 per 100 dog-years) was 5 times lower than at program onset. Six native adult dogs born after interventions and with stable lifetime residence were T. cruzi-seropositive: three had exposure to T. infestans at their houses and one was an incident case. Conclusions These results support the interruption of vector-borne transmission of T. cruzi to humans in rural Pampa del Indio. Congenital transmission was the most likely source of the only seropositive child born after interventions. Residual transmission to dogs was likely related to transient infestations and other transmission routes. Sustained vector control supplemented with human chemotherapy can lead to a substantial reduction of Chagas disease transmission in the Argentine Chaco.

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Investigation regarding the presence of Trypanosoma cruzi in triatomines and humans in rural households in the State of Paraná, southern Brazil

Research Society and Development ◽

10.33448/rsd-v10i10.18366 ◽

2021 ◽

Vol 10 (10) ◽

pp. e54101018366

Author(s):

Ana Paula de Abreu ◽

Hevillyn Fernanda Lucas da Silva ◽

Marcella Paula Mansano Sarto ◽

Giullia Ferreira Iunklaus ◽

João Vitor Trovo ◽

...

Keyword(s):

Trypanosoma Cruzi ◽

Rural Households ◽

Etiologic Agent ◽

The State ◽

Molecular Techniques ◽

Triatoma Infestans ◽

Southern Brazil ◽

The North ◽

Intestinal Contents ◽

Cruzi Infection

Trypanosoma cruzi, the etiologic agent of Chagas disease (CD), is transmitted by hematophagous insects belonging to the subfamily Triatominae. After elimination of Triatoma infestans, the infestation of human dwellings by secondary species of vectors continues to pose a risk of transmission of the parasite. Our aim was to investigate the T. cruzi presence in triatomines and humans in rural households in the State of Paraná, southern Brazil. The capture of the insects was carried out by technicians of the municipalities after residents reported the outbreak. Five residents and 27 triatomines captured in four municipalities in the North and Midwest of the state were evaluated. The research of T. cruzi was carried out using parasitological, serological, and molecular techniques, in human blood, excreta, intestinal contents and insect macerate. Panstrongylus megistus, P. geniculatus and Triatoma sp. were identified. Ten specimens of P. megistus were captured in a house in Mandaguari with five residents and presented an infection rate of 70% for T. cruzi like. All residents tested negative for T. cruzi infection. Another 15 P. megistus were captured in the peridomicile in Janiópolis and had 100.0% positivity. The only adult specimen of P. geniculatus captured in the intradomicile in Amaporã, as well as the nymph of Triatoma in the peridomicile in Paiçandu, were negative. The finding of P. megistus naturally infected by T. cruzi in households in rural area of Paraná demonstrates a potential risk of vector transmission of CD in these regions.

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Elucidating the Mechanism of Trypanosoma cruzi Acquisition by Triatomine Insects: Evidence from a Large Field Survey of Triatoma infestans

Tropical Medicine and Infectious Disease ◽

10.3390/tropicalmed5020087 ◽

2020 ◽

Vol 5 (2) ◽

pp. 87

Author(s):

Aaron W. Tustin ◽

Ricardo Castillo-Neyra ◽

Laura D. Tamayo ◽

Renzo Salazar ◽

Katty Borini-Mayorí ◽

...

Keyword(s):

Trypanosoma Cruzi ◽

Regression Models ◽

Control Strategies ◽

Protozoan Parasite ◽

Etiologic Agent ◽

Triatoma Infestans ◽

Large Field ◽

Blood Sucking ◽

Triatomine Bugs ◽

Cruzi Infection

Blood-sucking triatomine bugs transmit the protozoan parasite Trypanosoma cruzi, the etiologic agent of Chagas disease. We measured the prevalence of T. cruzi infection in 58,519 Triatoma infestans captured in residences in and near Arequipa, Peru. Among bugs from infected colonies, T. cruzi prevalence increased with stage from 12% in second instars to 36% in adults. Regression models demonstrated that the probability of parasite acquisition was roughly the same for each developmental stage. Prevalence increased by 5.9% with each additional stage. We postulate that the probability of acquiring the parasite may be related to the number of feeding events. Transmission of the parasite does not appear to be correlated with the amount of blood ingested during feeding. Similarly, other hypothesized transmission routes such as coprophagy fail to explain the observed pattern of prevalence. Our results could have implications for the feasibility of late-acting control strategies that preferentially kill older insects.

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