Domestic host availability modifies human‐triatomine contact and host shifts of the Chagas disease vector <i>Triatoma infestans</i> in the humid Argentine Chaco

Ordóñez-Krasnowski, Paula; Lanati, Leonardo; Gaspe, María Sol; Cardinal, Marta Victoria; Ceballos, Leonardo A.; Gürtler, Ricardo E.

doi:10.1111/mve.12463

Cited by 13 publications

(14 citation statements)

References 43 publications

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“…Peri-urban and rural houses had similar frequencies of domestic bugs with mixed blood meals (19 and 22%) and HBI (62 and 65%), respectively. As expected, the proportions of dog-or cat-fed bugs (dog-cat blood index) and of chicken-fed bugs (chicken blood index) significantly decreased the HBI of domestic T. infestans [27,28,45]. These results further support the hypothesis that the occurrence of domestic animals indoors strongly affects human-vector contact rates and triatomine infection.…”

Section: Discussionsupporting

confidence: 85%

“…The main blood meal source detected in domestic bugs was humans, whereas chickens and dogs were the main blood meal sources in the peridomestic ecotopes, as in other settings [27,28,[44][45][46][47]. Domestic T. infestans collected in the Paraguayan Chaco nearly exclusively fed on humans [48], in a context of strong vector control activities.…”

Section: Discussionmentioning

confidence: 99%

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Trypanosoma cruzi infection in Triatoma infestans and high levels of human–vector contact across a rural-to-urban gradient in the Argentine Chaco

et al. 2021

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Background Peri-urban and urban settings have recently gained more prominence in studies on vector-borne transmission of Trypanosoma cruzi due to sustained rural-to-urban migrations and reports of urban infestations with triatomines. Prompted by the finding of Triatoma infestans across the rural-to-urban gradient in Avia Terai, an endemic municipality of the Argentine Chaco, we assessed selected components of domestic transmission risk in order to determine its variation across the gradient. Methods A baseline vector survey was conducted between October 2015 and March 2016, following which we used multistage random sampling to select a representative sample of T. infestans at the municipal level. We assessed T. cruzi infection and blood-feeding sources of 561 insects collected from 109 houses using kinetoplast DNA-PCR assays and direct enzyme-linked immunosorbent assays, respectively. We stratified triatomines according to their collection site (domestic or peridomestic), and we further categorized peridomestic sites in ecotopes of low- or high-risk for T. cruzi infection. Results The overall adjusted prevalence of T. cruzi-infected T. infestans was 1.8% (95% confidence interval [CI] 1.3–2.3) and did not differ between peri-urban (1.7%) and rural (2.2%) environments. No infection was detected in bugs captured in the urban setting; rather, infected triatomines were mainly collected in rural and peri-urban domiciles, occurring in 8% of T. infestans-infested houses. The main blood-feeding sources of domestic and peridomestic triatomines across the gradient were humans and chickens, respectively. The proportion of triatomines that had fed on humans did not differ between peri-urban (62.5%) and rural (65.7%) domiciles, peaking in the few domestic triatomines collected in urban houses and decreasing significantly with an increasing proportion of chicken- and dog- or cat-fed bugs. The relative odds ratio (OR) of having a T. cruzi infection was nearly threefold higher in bugs having a blood meal on humans (OR 3.15), dogs (OR 2.80) or cats (OR: 4.02) in a Firth-penalized multiple logistic model. Conclusions Trypanosoma cruzi transmission was likely occurring both in peri-urban and rural houses of Avia Terai. Widespread infestation in a third of urban blocks combined with high levels of human–triatomine contact in the few infested domiciles implies a threat to urban inhabitants. Vector control strategies and surveillance originally conceived for rural areas should be tailored to peri-urban and urban settings in order to achieve sustainable interruption of domestic transmission in the Chaco region.

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Section: Discussionsupporting

confidence: 85%

Section: Discussionmentioning

confidence: 99%

Trypanosoma cruzi infection in Triatoma infestans and high levels of human–vector contact across a rural-to-urban gradient in the Argentine Chaco

et al. 2021

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“…Nearly all of the dogs included in the study were treated with fluralaner, and roughly 50–65% of them were reportedly tied up to a target site for 3–4 weeks, with other treated dogs ranging freely throughout the compound and nearby areas. The local availability of alternative suitable hosts, especially chickens in some peridomestic habitats, most likely hampered local vector elimination by reducing dog-triatomine contact rates, as recorded previously in experimental and field settings [ 43 – 45 ]. In the present study, the four infested target sites that persisted as such until trial endpoint were occupied by chickens.…”

Section: Discussionmentioning

confidence: 99%

“…To determine host-feeding sources, third-instar nymphs and later stages collected by timed searches or householders were dissected, the blood meal extracted in microtubes containing phosphate-buffered saline with crystal violet and tested with a direct ELISA assay against human, dog, cat and chicken antisera with high sensitivity and specificity values [ 43 ]. These are the most frequent blood meal sources in the study ecotopes [ 44 , 45 ]. The tested samples included all triatomines collected in target sites by timed searches in domiciles and up to 20 triatomines per peridomestic site by survey and treatment group, plus 70 triatomines collected by householders and 12 triatomines collected from non-target sites.…”

Section: Methodsmentioning

confidence: 99%

Treatment of dogs with fluralaner reduced pyrethroid-resistant Triatoma infestans abundance, Trypanosoma cruzi infection and human-triatomine contact in the Argentine Chaco

et al. 2022

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Background Triatomine elimination efforts and the interruption of domestic transmission of Trypanosoma cruzi are hampered by pyrethroid resistance. Fluralaner, a long-lasting ectoparasiticide administered to dogs, substantially reduced site infestation and abundance of pyrethroid-resistant Triatoma infestans Klug (Heteroptera: Reduviidae) in an ongoing 10-month trial in Castelli (Chaco Province, Argentina). We assessed the effects of fluralaner on vector infection with T. cruzi and blood meal sources stratified by ecotope and quantified its medium-term effects on site infestation and triatomine abundance. Methods We conducted a placebo-controlled, before-and-after efficacy trial of fluralaner in 28 infested sites over a 22-month period. All dogs received either an oral dose of fluralaner (treated group) or placebo (control group) at 0 month post-treatment [MPT]. Placebo-treated dogs were rescue-treated with fluralaner at 1 MPT, as were all eligible dogs at 7 MPT. Site-level infestation and abundance were periodically assessed by timed manual searches with a dislodging aerosol. Vector infection was mainly determined by kDNA-PCR and blood meal sources were determined by enzyme-linked immunosorbent assay. Results In fluralaner-treated households, site infestation dropped from 100% at 0 MPT to 18–19% over the period 6–22 MPT while mean abundance plummeted from 5.5 to 0.6 triatomines per unit effort. In control households, infestation dropped similarly post-treatment. The overall prevalence of T. cruzi infection steadily decreased from 13.8% at 0–1 MPT (baseline) to 6.4% and subsequently 2.3% thereafter, while in domiciles, kitchens and storerooms it dropped from 17.4% to 4.7% and subsequently 3.3% thereafter. Most infected triatomines occurred in domiciles and had fed on humans. Infected-bug abundance plummeted after fluralaner treatment and remained marginal or nil thereafter. The human blood index of triatomines collected in domiciles, kitchens and storerooms highly significantly fell from 42.9% at baseline to 5.3–9.1% over the period 6–10 MPT, increasing to 36.8% at 22 MPT. Dog blood meals occurred before fluralaner administration only. The cat blood index increased from 9.9% at baseline to 57.9–72.7% over the period 6–10 MPT and dropped to 5.3% at 22 MPT, whereas chicken blood meals rose from 39.6% to 63.2–88.6%. Conclusion Fluralaner severely impacted infestation- and transmission-related indices over nearly 2 years, causing evident effects at 1 MPT, and deserves larger efficacy trials. Graphical Abstract

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“…Given the notorious dominance of chicken coop infestations and chicken blood meals throughout the Argentine Chaco (e.g. Alvedro et al, 2021;Ord oñez-Krasnowsky et al, 2020), administration of the existing formulations of fluralaner to dogs, chickens and cats may be required to fully suppress (peri)domestic triatomine foci in high-risk settings.…”

Section: Outcome Assessmentsmentioning

confidence: 99%

Control of pyrethroid‐resistant populations of Triatoma infestans, the main vector of Trypanosoma cruzi, by treating dogs with fluralaner in the Argentine Chaco

Laiño

Cardinal

Gaspe

et al. 2021

Medical Vet Entomology

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We assessed whether fluralaner administered to outbred healthy dogs reduced or supressed site infestation and abundance of pyrethroid‐resistant populations of Triatoma infestans Klug (Heteroptera: Reduviidae). We conducted a placebo‐controlled before‐and‐after efficacy trial in 28 infested sites in Castelli (Argentine Chaco) over 10 months. All 72 dogs initially present received either an oral dose of fluralaner (treated group) or placebo (control group) at month 0 posttreatment (MPT). Preliminary results justified treating all 38 control‐house dogs with fluralaner 1 month later, and 71 of 78 existing dogs at 7 MPT. Site‐level infestation and triatomine abundance were evaluated using timed manual searches with a dislodging aerosol. In the fluralaner‐treated group, infestation dropped significantly from 100% at baseline to 19% over 6–10 MPT whereas mean abundance fell highly significantly from 5.5 to 0.8–0.9 triatomines per unit effort. In the placebo group, site infestation and mean abundance remained stable between 0 and 1 MPT, and strongly declined after fluralaner administration from 13.0−14.7 ‐ triatomines at 0–1 MPT to 4.0–4.2 over 6–10 MPT. Only one of 81 noninfested sites before fluralaner treatment became infested subsequently. Fluralaner significantly reduced the site‐level infestation and abundance of pyrethroid‐resistant T. infestans and should be tested more widely in Phase III efficacy trials.

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Domestic host availability modifies human‐triatomine contact and host shifts of the Chagas disease vector Triatoma infestans in the humid Argentine Chaco

Cited by 13 publications

References 43 publications

Trypanosoma cruzi infection in Triatoma infestans and high levels of human–vector contact across a rural-to-urban gradient in the Argentine Chaco

Trypanosoma cruzi infection in Triatoma infestans and high levels of human–vector contact across a rural-to-urban gradient in the Argentine Chaco

Treatment of dogs with fluralaner reduced pyrethroid-resistant Triatoma infestans abundance, Trypanosoma cruzi infection and human-triatomine contact in the Argentine Chaco

Control of pyrethroid‐resistant populations of Triatoma infestans, the main vector of Trypanosoma cruzi, by treating dogs with fluralaner in the Argentine Chaco

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