Urban infestation by <i>Triatoma infestans</i> (Hemiptera: Reduviidae), an overlooked phenomena for Chagas disease in Argentina

Vector-borne transmission of Chagas disease in urban areas of Argentina has been an overlooked phenomena. We conducted the first comprehensive cross-sectional study of domestic infestation with Triatoma infestans and vector infection with Trypanosoma cruzi in a metropolitan area of San Juan, Argentina. Our results document the occurrence of T. infestans infected with T. cruzi in human sleeping quarters. In this urban setting, we also show that infestation was associated with construction materials, the presence of chickens, cats and a large number of dogs that can provide blood meals for the vector. Our findings reveal new challenges for vectorial control agencies.

Key words:
urban infestation; vector control; San Juan

Authorship

Yael Mariana Provecho

Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Departamento de Ecología, Genética y Evolución, Ciudad Universitaria, Buenos Aires, ArgentinaUniversidad de Buenos AiresArgentinaCiudad Universitaria, Buenos Aires, ArgentinaUniversidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Departamento de Ecología, Genética y Evolución, Ciudad Universitaria, Buenos Aires, Argentina

Consejo Nacional de Investigaciones Científicas y Técnicas, Instituto de Ecología, Genética y Evolución de Buenos Aires, Ciudad Universitaria, Buenos Aires, ArgentinaConsejo Nacional de Investigaciones Científicas y TécnicasArgentinaCiudad Universitaria, Buenos Aires, ArgentinaConsejo Nacional de Investigaciones Científicas y Técnicas, Instituto de Ecología, Genética y Evolución de Buenos Aires, Ciudad Universitaria, Buenos Aires, Argentina

Ministerio de Salud de la Nación, Dirección de Control de Enfermedades Transmitidas por Vectores, Buenos Aires, ArgentinaMinisterio de Salud de la NaciónArgentinaBuenos Aires, ArgentinaMinisterio de Salud de la Nación, Dirección de Control de Enfermedades Transmitidas por Vectores, Buenos Aires, Argentina

María del Pilar Fernández

Washington State University, Paul G Allen School for Global Animal Health, Washington, United StatesWashington State UniversityUSAWashington, USAWashington State University, Paul G Allen School for Global Animal Health, Washington, United States

Liliana Salvá

Ministerio de Salud de San Juan, Programa de Control de Vectores, San Juan, ArgentinaMinisterio de Salud de San JuanArgentinaSan Juan, ArgentinaMinisterio de Salud de San Juan, Programa de Control de Vectores, San Juan, Argentina

Sergio Meli

Florencia Cano

Paula Sartor

Universidad Nacional del Nordeste, Facultad de Ciencias Exactas, Naturales y Agrimensura, Corrientes, ArgentinaUniversidad Nacional del NordesteArgentinaCorrientes, ArgentinaUniversidad Nacional del Nordeste, Facultad de Ciencias Exactas, Naturales y Agrimensura, Corrientes, Argentina

Ministerio de Salud Pública del Chaco, Resistencia, Chaco, ArgentinaMinisterio de Salud Pública del ChacoArgentinaResistencia, Chaco, ArgentinaMinisterio de Salud Pública del Chaco, Resistencia, Chaco, Argentina

Ana Laura Carbajal-de-la-Fuente ⁺+ Corresponding author: analaura.carbajal@gmail.com

Consejo Nacional de Investigaciones Científicas y Técnicas, Buenos Aires, ArgentinaConsejo Nacional de Investigaciones Científicas y TécnicasArgentinaBuenos Aires, ArgentinaConsejo Nacional de Investigaciones Científicas y Técnicas, Buenos Aires, Argentina

Ministerio de Salud de la Nación, Centro Nacional de Diagnóstico e Investigación en Endemo-epidemias/Administración Nacional de Laboratorios e Institutos de Salud Dr Carlos Malbrán, Buenos Aires, ArgentinaMinisterio de Salud de la NaciónArgentinaBuenos Aires, ArgentinaMinisterio de Salud de la Nación, Centro Nacional de Diagnóstico e Investigación en Endemo-epidemias/Administración Nacional de Laboratorios e Institutos de Salud Dr Carlos Malbrán, Buenos Aires, Argentina

http://orcid.org/0000-0003-0809-3507

+ Corresponding author: analaura.carbajal@gmail.com

PS, LS, SM, FC, YP and ALCF - Conception and design; LS, SM and FC - field work; YP, MPF and ALCF - data analysis; ALCF, MPF and YP - manuscript writing. All authors read and approved the final manuscript.

SCIMAGO INSTITUTIONS RANKINGS

Figures | Tables

Figures (2)
Tables (3)

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Fig. 1:
location of the study area in Argentina; (A) Location of San Juan province; (B) Rawson Department in San Juan Province; (C) Metropolitan area of Rawson Department (gray) with study area (white rectangle) showing the proximity to the Capital Department (black); (D) Urban houses with access to the power grid, natural gas, asphalted roads, drinking water, sewage and trash disposal.

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Fig. 2:
map showing the 1,784 inspected houses (black dots) georeferenced in the 75 blocks selected as the study area, and the location of houses infested with Triatoma infestans (white circles) and the occurrence of vectors infected with Trypanosoma cruzi (gray star) in the Rawson Department, San Juan province, Argentina, 2017.

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TABLE I
Prevalence of Trypanosoma cruzi infection in Triatoma infestans collected in houses from metropolitan area of San Juan, June-December 2017. The infected bugs came from 17 houses.

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TABLE II
Prevalence of domestic and intra-domiciliary infestation with Triatoma infestans and unadjusted odds ratio (OR) and 95% confidence interval (CI) obtained from bivariate. Firth penalized logistic regressions, for variables associated with the infestation by T. infestans in urban domiciles in the Rawson Department, San Juan, Argentina, June-December 2017.

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TABLE III
Adjusted odds ratio (ORadj) and 95% confidence interval (CI) obtained from the multiple Firth penalized logistic regressions for domestic and intra-domiciliary infestation. Using a multi-model inference approach, one model (the full model) was identified as the best model for domestic infestation, while three competing models (delta AICc < 2) were averaged for intra-domiciliary infestation. Relative importance of a variable refers to the relative presence of the variable in the competing models (1 = present in all three models; 0 = absent in all three models).

Fig. 1: location of the study area in Argentina; (A) Location of San Juan province; (B) Rawson Department in San Juan Province; (C) Metropolitan area of Rawson Department (gray) with study area (white rectangle) showing the proximity to the Capital Department (black); (D) Urban houses with access to the power grid, natural gas, asphalted roads, drinking water, sewage and trash disposal.

Fig. 2: map showing the 1,784 inspected houses (black dots) georeferenced in the 75 blocks selected as the study area, and the location of houses infested with Triatoma infestans (white circles) and the occurrence of vectors infected with Trypanosoma cruzi (gray star) in the Rawson Department, San Juan province, Argentina, 2017.

TABLE I Prevalence of Trypanosoma cruzi infection in Triatoma infestans collected in houses from metropolitan area of San Juan, June-December 2017. The infected bugs came from 17 houses.

Infested houses	Stage	Nº of T. infestans examined by OM	Nº of infected (%)
Intradomicile	Third-fifth	134	12 (8.9)
Intradomicile	Adult	138	13 (9.4)
Peridomicile	Third-fifth	349	18 (5.2)
Peridomicile	Adult	217	15 (6.9)
Total		760	58 (7.6)

OM: optical microscopy (40x).

TABLE II Prevalence of domestic and intra-domiciliary infestation with Triatoma infestans and unadjusted odds ratio (OR) and 95% confidence interval (CI) obtained from bivariate. Firth penalized logistic regressions, for variables associated with the infestation by T. infestans in urban domiciles in the Rawson Department, San Juan, Argentina, June-December 2017.

Variable		Domestic infestation^*	OR (CI)	Intra-domiciliary infestation^**	OR (CI)
Variable	N	% (N inspected)		% (N inspected)
People per house
	1-2	7.0 (673)	1	3.6 (673)	1
	3-5	6.7 (856)	0.9 (0.6-1.4)	3.0 (856)	0.8 (0.5-1.5)
	≥ 6	8.9 (213)	1.3 (0.8-2.3)	5.2 (213)	1.5 (0.7-3.1)
No. of dogs
	0	7.7 (104)	1	2.9 (104)	1
	1	5.5 (454)	0.7 (0.3-1.5)	3.1 (454)	0.9 (0.3-3.1)
	2	8.0 (325)	1.0 (0.4-2.2)	4.6 (325)	1.5 (0.4-4.7)
	≥ 3	13.7 (285)	1.8 (0.8-4.0)	4.2 (285)	1.3 (0.4-4.4)
Cats
	No	6.9 (823)	1	2.7 (823)	1
	Yes	11.9 (345)	1.8 (1.2-2.8)^***	6.4 (345)	2.5 (1.4-4.5)^***
Chickens
	No	7.3 (1130)	1	3.7 (1130)	1
	Yes	42.1 (38)	9.3 (4.7-18.3)^***	5.3 (38)	1.8 (0.5-6.6)
Wall and roof with materials that could offer refuge for triatomines
Wall
	No	-	-	2.0 (1274)	1
	Yes	-	-	7.8 (463)	4.0 (2.4-6.7)^***
Roof
	No	-	-	7.3 (629)	1
	Yes	-	-	1.4 (1109)	5.3 (2.9-9.3)^***

*: domestic infestation refers to the occurrence of a live T. infestans in any domicile or peridomestic structure; **: intra-domiciliary infestation refers only to the presence of the vector inside the domicile; ***: p ˂ 0.05; N: number.

TABLE III Adjusted odds ratio (ORadj) and 95% confidence interval (CI) obtained from the multiple Firth penalized logistic regressions for domestic and intra-domiciliary infestation. Using a multi-model inference approach, one model (the full model) was identified as the best model for domestic infestation, while three competing models (delta AICc < 2) were averaged for intra-domiciliary infestation. Relative importance of a variable refers to the relative presence of the variable in the competing models (1 = present in all three models; 0 = absent in all three models).

	Domestic infestation^*	Intra-domiciliary infestation^**
Variable	ORadj (CI)	Relative importance	ORadj (CI)
Number of householders		0
1-2	1		-
3-5	0.68 (0.42 - 1.1)		-
≥ 6	0.89 (0.47 - 1.67)		-
No. of dogs		0.7
0	1		1
1	1.14 (0.5 - 2.86)		1.14 (0.34 - 3.81)
2	1.65 (0.73 - 4.15)		1.72 (0.52 - 5.7)
≥ 3	2.68 (1.22 - 6.59)^***		1.36 (0.4 - 4.66)
Cats		1
No	1		1
Yes	1.87 (1.19 - 2.9)^***		2.41 (1.32 - 4.4)^***
Chickens		0.2
No	1		1
Yes	8.77 (4.28 - 17.79)^***		1.16 (0.29 - 4.55)
Wall and roof with materials that could offer refuge for triatomines
Wall		1
No	-		1
Yes	-		0.24 (0.01 - 6.22)
Roof		1
No	-		1
Yes	-		1.06 (0.04 - 26.56)

*: domestic infestation refers to the occurrence of a live T. infestans in any domicile or peridomestic structure; **: intra-domiciliary infestation refers only to the presence of the vector inside the domicile; ***: p < 0.05.

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Urban infestation by <i>Triatoma infestans</i> (Hemiptera: Reduviidae), an overlooked phenomena for Chagas disease in Argentina

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[1] + Corresponding author: analaura.carbajal@gmail.com