RESUMEN
BACKGROUND: Chagas disease is a neglected tropical disease (NTD). Cost-effective strategies for large-scale implementation of diagnosis and etiological treatment are urgently needed to comply with NTD control goals. We determined the seroprevalence of Trypanosoma cruzi infection and associated risk factors in a well-defined rural population of Pampa del Indio municipality including creole and indigenous (Qom) households and developed two indices to identify houses harboring infected children. METHODS: We serodiagnosed and administered a questionnaire to 1337 residents (48.2% of the listed population) in two sections of the municipality (named Areas II and IV) 6-9 years after deploying sustained vector control interventions. Multiple logistic regression models were used to evaluate the relationship between human infection and a priori selected predictors. Two risk indices were constructed based on environmental and serostatus variables, and we used spatial analysis to test whether households harboring T. cruzi-seropositive children were randomly distributed. RESULTS: The global seroprevalence of T. cruzi infection was 24.8%. Human infection was positively and significantly associated with exposure time to triatomines, the household number of seropositive co-inhabitants, maternal seropositivity for T. cruzi, recent residence at the current house and the presence of suitable walls for triatomine colonization in the domicile. The pre-intervention mean annual force of infection (FOI) was 1.23 per 100 person-years. Creoles from Area IV exhibited the highest seroprevalence and FOI; Qom people from both areas displayed intermediate ones and creoles from Area II the lowest. Three hotspots of infected children were spatially associated with hotspots of triatomine abundance at baseline and persistent house infestation. No child born after vector control interventions was T. cruzi seropositive except for one putative transplacental case. Two simple risk indices (based on self-reported inhabiting an infested house and suitable walls for triatomines or maternal serostatus) identified 97.3-98.6% of the households with at least one T. cruzi-seropositive child. CONCLUSIONS: We showed strong heterogeneity in the seroprevalence of T. cruzi infection within and between ethnic groups inhabiting neighboring rural areas. Developed indices can be used for household risk stratification and to improve access of rural residents to serodiagnosis and treatment and may be easily transferred to primary healthcare personnel.
Asunto(s)
Enfermedad de Chagas , Trypanosoma cruzi , Animales , Niño , Humanos , Enfermedad de Chagas/epidemiología , Factores de Riesgo , Estudios Seroepidemiológicos , Triatoma , Pueblos Indígenas , ArgentinaRESUMEN
Pyrethroid-resistance is an emergent trait in populations of various insect species. For Triatoma infestans (Klug, 1834) (Heteroptera: Reduviidae), the major vector of Chagas disease in the southern part of South America, hotspot areas of pyrethroid-resistance have recently been found in the Chaco Province of Argentina. Resistant condition can reduce fitness of individuals in the absence of insecticide exposure, that is, fitness costs. We evaluated the existence of developmental and/or reproductive costs in T. infestans collected from two areas of pyrethroid-resistance in Chaco Province, Argentina. Three toxicological groups were defined from field-collected insects: susceptible (survival <20%), moderately resistant (survival between 20% and 80%) and highly resistant (survival >80%). Cohorts of the three toxicological groups were followed-up to study life cycle and reproductive parameters. Additionally, we parameterized matrix population growth models. First and IV nymphal stages of the resistant groups exhibited a longer stage duration than susceptible ones. The reproductive days and hatching success showed significant lower values revealing reproductive costs for the resistant groups. Matrix analysis showed lower population growth rates for the resistant groups. Our results support developmental and reproductive costs for pyrethroid-resistant individuals. This trait could be interpreted as lower population recovery ability for pyrethroid-resistant individuals compared to susceptible insects after alternative vector control actions.
Asunto(s)
Enfermedad de Chagas , Insecticidas , Piretrinas , Triatoma , Humanos , Animales , Argentina , Resistencia a los Insecticidas , Insecticidas/farmacología , Nitrilos , Enfermedad de Chagas/veterinaria , FertilidadRESUMEN
Domestic animals may affect human-vector contact and parasite transmission rates. We investigated the relationships between host-feeding choices, site-specific host availability, bug nutritional status, stage and abundance of Triatoma infestans Klug (Heteroptera: Reduviidae) in rural houses of Pampa del Indio during spring. We identified the bloodmeal sources of 865 triatomines collected in 70 sites from four main ecotopes. The main sources in domiciles were human (65.9%), chicken (23.4%) and dog (22.4%); dog (64.4%, 35.3%) and chicken (33.1%, 75.4%) in kitchens and storerooms, respectively; and chicken (94.7%) in chicken coops. Using random-intercept logistic regression clustered by domicile, the fraction of human-fed triatomines strongly decreased with increasing proportions of chicken- and dog-fed bugs, dropping from 96.4% when no chicken or dog slept indoors at night to 59.4% when both did. The fraction of dog-fed bugs significantly decreased with increasing human and chicken blood indices, and marginally increased with an indoor-resting dog. Mixed blood meals occurred 3.62 times more often when a chicken or a dog slept indoors. Host blood source did not affect mean body weight adjusted for body length and bug stage. Indoor-resting chickens and dogs greatly modified human-bug contact rates, and may be targeted with long-lasting systemic insecticides to suppress infestation.
Asunto(s)
Enfermedad de Chagas/transmisión , Pollos/parasitología , Perros/parasitología , Triatoma , Animales , Argentina/epidemiología , Enfermedad de Chagas/veterinaria , Conducta Alimentaria , Humanos , Control de Insectos , Insectos Vectores/parasitología , Insectos Vectores/fisiología , Características de la Residencia , Población Rural , Estaciones del Año , Triatoma/parasitología , Triatoma/fisiología , Enfermedades Transmitidas por VectoresRESUMEN
BACKGROUND: Trypanosoma cruzi, the protozoan agent of Chagas disease, is comprised of at least 6 genetic lineages (TcI-TcVI). Their geographical distribution, clinical associations and reservoir hosts are not fully elucidated, as genotyping is hampered due to the difficulty in isolating representative populations of organisms. Lineage-specific serological techniques may address these issues. METHODS: Trypanosoma cruzi lineage-specific serological assays were performed on human, canine, feline and armadillo sera from the Gran Chaco in northern Argentina, a region of ongoing transmission. Synthetic peptides representing lineage-specific epitopes of the trypomastigote small surface antigen (TSSA) were used in ELISA, and the TcII/V/VI shared epitope peptide (TSSApep-II/V/VI) was used in the Chagas Sero K-SeT rapid diagnostic test (RDT). RESULTS: Chagas Sero K-SeT RDT, using Protein G to detect human and canine IgG, was at least as sensitive as TSSApep-II/V/VI ELISA using specific secondary antibodies. For sera from humans TSSApep-II/V/VI seroprevalence by Chagas Sero K-SeT was 273/393 (69.5%), for dogs 48/73 (65.8%) and for armadillos 1/7 (14.3%); by ELISA for cats 5/19 (26.3%). The seroprevalence for humans was similar to that for Bolivian patients, amongst whom we previously observed an association of TSSApep-II/V/VI seropositivity with severity of cardiomyopathy. In humans, prevalence of TSSApep-II/V/VI recognition was associated with locality, and with increasing and decreasing age within the Qom and Creole populations, respectively. For dogs TSSApep-II/V/VI recognition was associated with being born before community-wide insecticide spraying (P = 0.05) and with Qom household (P < 0.001). CONCLUSIONS: We show here that Chagas Sero K-SeT RDT can replace ELISA for TSSApep-II/V/VI serology of humans and dogs; for humans there were statistically significant associations between a positive Chagas Sero K-SeT RDT and being resident in Area IV, and for dogs association with Qom household or with being born before the mass spraying campaign; we also show that with cats the TcII/V/VI epitope can be detected by ELISA. We assessed the lineage distribution in an unprecedented 83% of the human T. cruzi-seropositive population. These results form the basis for more detailed studies, enabling rapid in-the-field surveillance of the distribution and clustering of these lineages among humans and mammalian reservoirs of T. cruzi infection.
Asunto(s)
Anticuerpos Antiprotozoarios/sangre , Enfermedad de Chagas/epidemiología , Enfermedad de Chagas/veterinaria , Pruebas Diagnósticas de Rutina/métodos , Serogrupo , Pruebas Serológicas/métodos , Trypanosoma cruzi/clasificación , Animales , Argentina/epidemiología , Armadillos , Gatos , Enfermedad de Chagas/parasitología , Estudios Transversales , Perros , Ensayo de Inmunoadsorción Enzimática/métodos , Humanos , Estudios Seroepidemiológicos , Trypanosoma cruzi/genética , Trypanosoma cruzi/aislamiento & purificaciónRESUMEN
Dogs play an important role as reservoirs and hosts of multiple pathogens shared with humans and wildlife, which contribute significantly to the global burden of disease. Here, we assessed the occurrence of a broad range of zoonotic and non-zoonotic parasites in dogs from a rural area in the humid Chaco; determined the occurrence of polyparasitism; and explored its association with selected risk factors. In total, 212 dogs were examined serologically to determine Trypanosoma cruzi infection and 152 of them also were examined for Ehrlichia canis, Borrelia bugderfori, Anaplasma phagocitophylum, Dirofilaria immitis and Toxoplasma gondii. Fecal samples from 85 dogs were examined for intestinal parasites. Seventeen parasite species were seen, 77% of which are zoonotic. The most prevalent parasites were Ancylostoma caninum (68.2%), T. gondii (55.3%, first report for dogs in Argentina), Giardia sp. (25.9%), Cryptosporidium sp. (20.0%), T. cruzi (16.5%), trematodes (15.3%) and Toxocara canis (14.1%). Polyparasitism was found in 96% of the dogs, with up to six parasite species in a single dog, and was significantly associated with age of dog but not with host body condition or sex. The most frequent pair of parasites found together were T. gondii-A. caninum (46%), A. caninum-T. cruzi (34%) and T. gondii-T. cruzi (27%). The prevalence of anemia and leukocytosis was significantly higher in dogs showing the worst body condition. Our findings likely reflect structural poverty, poor sanitation and lack of a safe water supply. Importantly, many of the prevalent parasites seen are threats to human health. 243 words.
Asunto(s)
Enfermedades de los Perros/parasitología , Enfermedades Parasitarias en Animales/parasitología , Zoonosis/parasitología , Animales , Argentina/epidemiología , Enfermedades de los Perros/epidemiología , Enfermedades de los Perros/transmisión , Perros , Femenino , Parasitosis Intestinales/epidemiología , Parasitosis Intestinales/parasitología , Parasitosis Intestinales/transmisión , Parasitosis Intestinales/veterinaria , Masculino , Enfermedades Parasitarias en Animales/epidemiología , Enfermedades Parasitarias en Animales/transmisión , Prevalencia , Factores de Riesgo , Población Rural , Toxoplasmosis Animal/epidemiología , Toxoplasmosis Animal/parasitología , Toxoplasmosis Animal/transmisión , Enfermedades Transmitidas por Vectores/epidemiología , Enfermedades Transmitidas por Vectores/parasitología , Enfermedades Transmitidas por Vectores/transmisión , Enfermedades Transmitidas por Vectores/veterinaria , Zoonosis/epidemiología , Zoonosis/transmisiónRESUMEN
BACKGROUND: Rural populations in the Gran Chaco region have large prevalence rates of Trypanosoma cruzi infection and very limited access to diagnosis and treatment. We implemented an innovative strategy to bridge these gaps in 13 rural villages of Pampa del Indio held under sustained vector surveillance and control. METHODOLOGY: The non-randomized treatment program included participatory workshops, capacity strengthening of local health personnel, serodiagnosis, qualitative and quantitative PCRs, a 60-day treatment course with benznidazole and follow-up. Parents and healthcare agents were instructed on drug administration and early detection and notification of adverse drug-related reactions (ADR). Healthcare agents monitored medication adherence and ADRs at village level. PRINCIPAL FINDINGS: The seroprevalence of T. cruzi infection was 24.1% among 395 residents up to 18 years of age examined. Serodiagnostic (70%) and treatment coverage (82%) largely exceeded local historical levels. Sixty-six (85%) of 78 eligible patients completed treatment with 97% medication adherence. ADRs occurred in 32% of patients, but most were mild and manageable. Four patients showing severe or moderate ADRs required treatment withdrawal. T. cruzi DNA was detected by qPCR in 47 (76%) patients before treatment, and persistently occurred in only one patient over 20-180 days posttreatment. CONCLUSIONS AND SIGNIFICANCE: Our results demonstrate that diagnosis and treatment of T. cruzi infection in remote, impoverished rural areas can be effectively addressed through strengthened primary healthcare attention and broad social participation with adequate external support. This strategy secured high treatment coverage and adherence; effectively managed ADRs, and provided early evidence of positive therapeutic responses.
Asunto(s)
Enfermedad de Chagas/diagnóstico , Enfermedad de Chagas/tratamiento farmacológico , Accesibilidad a los Servicios de Salud , Administración de los Servicios de Salud , Tripanocidas/administración & dosificación , Argentina , Humanos , Atención Primaria de Salud , Población Rural , Participación SocialRESUMEN
Establishing the putative links between sylvatic and domestic transmission cycles of Trypanosoma cruzi, the etiological agent of Chagas disease, is of public health relevance. We conducted three surveys to assess T. cruzi infection in wild mammals from a rural and a preserved area in Misiones Province, Northeastern Argentina, which had recently been declared free of vector- and blood-borne transmission of human T. cruzi infection. A total of 200 wild mammals were examined by xenodiagnosis (XD) and/or polymerase chain reaction (PCR) amplification of the hyper-variable region of kinetoplast DNA minicircles of T. cruzi (kDNA-PCR). The overall prevalence of T. cruzi infection was 8%. Nine (16%) of 57 Didelphis albiventris opossums and two (7%) of 29 Desmodus rotundus vampire bats were positive by both XD and kDNA-PCR. Additionally, one D. rotundus positive for T. cruzi by kDNA-PCR tested positive by satellite-DNA-PCR (SAT-DNA-PCR). The T. cruzi-infected bats were captured indoors and in the yard of a vacant dwelling. All D. albiventris were infected with TcI and both XD-positive D. rotundus by TcII. Fifty-five opossum cubs within the marsupium were negative by XD. The mean infectiousness to the vector was 62% in D. albiventris and 50% in D. rotundus. Mice experimentally infected with a parasite isolate from a vampire bat displayed lesions typically caused by T. cruzi. Our study documents the presence of the genotype TcII in a sylvatic host for the first time in Argentina, and the occurrence of two transmission cycles of T. cruzi in a district free of domestic vector-borne transmission.
Asunto(s)
Enfermedad de Chagas/veterinaria , Quirópteros/parasitología , Reservorios de Enfermedades , Mamíferos/parasitología , Trypanosoma cruzi/aislamiento & purificación , Animales , Animales Salvajes/parasitología , Argentina/epidemiología , Enfermedad de Chagas/epidemiología , Enfermedad de Chagas/parasitología , Enfermedad de Chagas/transmisión , ADN Protozoario/genética , Vectores de Enfermedades , Zarigüeyas/parasitología , Reacción en Cadena de la Polimerasa , Prevalencia , XenodiagnósticoRESUMEN
Interactions among different species of parasites co-infecting the same host could be synergistic or antagonistic. These interactions may modify both the frequency of infected hosts and their infectiousness, and therefore impact on transmission dynamics. This study determined the infectiousness of Trypanosoma cruzi-seropositive dogs (using xenodiagnosis) and their parasite load (quantified by qPCR), and tested the association between both variables and the presence of concomitant endoparasites. A cross-sectional serosurvey conducted in eight rural villages from Pampa del Indio and neighboring municipalities (northeastern Argentina) detected 32 T. cruzi-seropositive dogs out of 217 individuals examined for infection. Both the infectiousness to the vector Triatoma infestans and parasite load of T. cruzi-seropositive dogs examined were heterogeneous. A statistically significant, nine-fold higher mean infectiousness was registered in T. cruzi-seropositive dogs co-infected with Ancylostoma caninum and a trematode than in T. cruzi-seropositive dogs without these infections. The median parasite load of T. cruzi was also significantly higher in dogs co-infected with these helminths. An opposite trend was observed in T. cruzi-seropositive dogs that were serologically positive to Toxoplasma gondii or Neospora caninum relative to dogs seronegative for these parasites. Using multiple logistic regression analysis with random effects, we found a positive and significant association between the infectiousness of T. cruzi-seropositive dogs and co-infections with A. caninum and a trematode. Our results suggest that co-infections may be a modifier of host infectiousness in dogs naturally infected with T. cruzi.
Asunto(s)
Enfermedad de Chagas/veterinaria , Coinfección/veterinaria , Enfermedades de los Perros/parasitología , Trypanosoma cruzi/aislamiento & purificación , Animales , Enfermedad de Chagas/complicaciones , Enfermedad de Chagas/parasitología , Perros , Helmintiasis Animal/complicaciones , Helmintiasis Animal/parasitología , Helmintiasis Animal/patologíaRESUMEN
We assessed the prevalence of infection with Trypanosoma cruzi, parasite genotypes (discrete typing units, DTUs), and the host-feeding sources of domestic and peridomestic Triatoma infestans Klug and Triatoma eratyrusiformis Del Ponte in eight rural communities of the subandean Calchaqui valleys in northwestern Argentina. We sought to analyze their epidemiological role in the context of routine vector surveillance and control actions. Infection with T. cruzi was determined by optic microscopy or polymerase chain reaction (PCR) amplification of the hypervariable region of kinetoplast DNA minicircles. Parasite genotypes were identified through a multi PCR-based strategy. Bloodmeal contents were tested with a direct ELISA assay against nine antisera. Human sleeping quarters (domiciles) and peridomestic dry-shrub fences concentrated most of the T. infestans and T. eratyrusiformis infected with T. cruzi, respectively. The most frequent host-feeding sources of T. infestans were chickens (73.1%) in peridomiciles and humans (73.3%) in domiciles, whereas T. eratyrusiformis fed more often on cavid rodents (92.6%), which thrived in the dry-shrub fences. The main T. cruzi DTU identified in both vectors was T. cruzi I (TcI). Triatoma eratyrusiformis was implicated in the local circulation of TcI among cavies and perhaps mice, but infection with other typically domestic DTUs (TcVI and TcII/TcV/TcVI) indicated overlap between (peri)domestic transmission cycles in both vector species. Because dry-shrub fences were not targeted for routine insecticide spraying, they may act as sources of (peri)domestic reinfestation. Triatoma eratyrusiformis is an emergent secondary vector of T. cruzi and plays a significant role in the local transmission of T. cruzi.
Asunto(s)
Enfermedad de Chagas/parasitología , Insectos Vectores/parasitología , Triatoma/parasitología , Trypanosoma cruzi/fisiología , Animales , Argentina , Enfermedad de Chagas/transmisión , Conducta Alimentaria , Humanos , Insectos Vectores/fisiología , Roedores/fisiología , Triatoma/fisiología , Trypanosoma cruzi/genética , Trypanosoma cruzi/aislamiento & purificaciónRESUMEN
Understanding the complex epidemiology of Trypanosoma cruzi transmission cycles requires comparative studies in widely different environments. We assessed the occurrence of T. cruzi infection in sylvatic mammals, their infectiousness to the vector, and parasite genotypes in a protected area of the Argentine Chaco, and compared them with information obtained similarly in a nearby disturbed area. A total of 278 mammals from >23 species in the protected area were diagnosed for T. cruzi infection using xenodiagnosis, kDNA-PCR and nuclear satellite DNA-PCR (SAT) from blood samples. The relative abundance and species composition differed substantially between areas. Didelphis albiventris opossums were less abundant in the protected area; had a significantly lower body mass index, and a stage structure biased toward earlier stages. The capture of armadillos was lower in the protected area. The composite prevalence of T. cruzi infection across host species was significantly lower in the protected area (11.1%) than in the disturbed area (22.1%), and heterogeneous across species groups. The prevalence of infection in D. albiventris and Thylamys pusilla opossums was significantly lower in the protected area (nil for D. albiventris), whereas infection in sigmodontine rodents was three times higher in the protected area (17.5 versus 5.7%). Parasite isolates from the two xenodiagnosis-positive mammals (1 Dasypus novemcinctus and 1 Conepatus chinga) were typed as TcIII; both specimens were highly infectious to Triatoma infestans. Fat-tailed opossums, bats and rodents were kDNA-PCR-positive and xenodiagnosis-negative. Desmodus rotundus and Myotis bats were found infected with T. cruzi for the first time in the Gran Chaco.
Asunto(s)
Animales Salvajes/parasitología , Enfermedad de Chagas/veterinaria , Reservorios de Enfermedades/parasitología , Mamíferos/parasitología , Animales , Argentina/epidemiología , Armadillos/parasitología , Enfermedad de Chagas/epidemiología , Enfermedad de Chagas/transmisión , Quirópteros/parasitología , Didelphis/parasitología , Mephitidae/parasitología , Zarigüeyas/parasitología , Enfermedades de los Roedores/epidemiología , Enfermedades de los Roedores/parasitología , Enfermedades de los Roedores/transmisión , Roedores , Trypanosoma cruzi/aislamiento & purificaciónRESUMEN
We review the epidemiological role of domestic and commensal hosts of Trypanosoma cruzi using a quantitative approach, and compiled >400 reports on their natural infection. We link the theory underlying simple mathematical models of vector-borne parasite transmission to the types of evidence used for reservoir host identification: mean duration of infectious life; host infection and infectiousness; and host-vector contact. The infectiousness of dogs or cats most frequently exceeded that of humans. The host-feeding patterns of major vectors showed wide variability among and within triatomine species related to their opportunistic behavior and variable ecological, biological and social contexts. The evidence shows that dogs, cats, commensal rodents and domesticated guinea pigs are able to maintain T. cruzi in the absence of any other host species. They play key roles as amplifying hosts and sources of T. cruzi in many (peri)domestic transmission cycles covering a broad diversity of ecoregions, ecotopes and triatomine species: no other domestic animal plays that role. Dogs comply with the desirable attributes of natural sentinels and sometimes were a point of entry of sylvatic parasite strains. The controversies on the role of cats and other hosts illustrate the issues that hamper assessing the relative importance of reservoir hosts on the basis of fragmentary evidence. We provide various study cases of how eco-epidemiological and genetic-marker evidence helped to unravel transmission cycles and identify the implicated hosts. Keeping dogs, cats and rodents out of human sleeping quarters and reducing their exposure to triatomine bugs are predicted to strongly reduce transmission risks.
Asunto(s)
Animales Domésticos/parasitología , Animales Salvajes/parasitología , Enfermedad de Chagas/transmisión , Vectores de Enfermedades , Interacciones Huésped-Parásitos , Triatoma/parasitología , Trypanosoma cruzi/parasitología , Animales , Gatos/parasitología , América Central/epidemiología , Enfermedad de Chagas/epidemiología , Perros/parasitología , Cobayas/parasitología , Humanos , Modelos Teóricos , Roedores/parasitología , América del Sur/epidemiologíaRESUMEN
BACKGROUND: The Gran Chaco ecoregion, a hotspot for Chagas and other neglected tropical diseases, is home to >20 indigenous peoples. Our objective was to identify the main ecological and sociodemographic determinants of house infestation and abundance of Triatoma infestans in traditional Qom populations including a Creole minority in Pampa del Indio, northeastern Argentina. METHODS: A cross-sectional survey determined house infestation by timed-manual searches with a dislodging aerosol in 386 inhabited houses and administered questionnaires on selected variables before full-coverage insecticide spraying and annual vector surveillance. We fitted generalized linear models to two global models of domestic infestation and bug abundance, and estimated coefficients via multimodel inference with model averaging. PRINCIPAL FINDINGS: Most Qom households were larger and lived in small-sized, recently-built, precarious houses with fewer peridomestic structures, and fewer livestock and poultry than Creoles'. Qom households had lower educational level and unexpectedly high residential mobility. House infestation (31.9%) was much lower than expected from lack of recent insecticide spraying campaigns and was spatially aggregated. Nearly half of the infested houses examined had infected vectors. Qom households had higher prevalence of domestic infestation (29.2%) than Creoles' (10.0%), although there is large uncertainty around the adjusted OR. Factors with high relative importance for domestic infestation and/or bug abundance were refuge availability, distance to the nearest infested house, domestic insecticide use, indoor presence of poultry, residential overcrowding, and household educational level. CONCLUSIONS AND SIGNIFICANCE: Our study highlights the importance of sociodemographic determinants of domestic infestation such as overcrowding, education and proximity to the nearest infested house, and corroborates the role of refuge availability, domestic use of insecticides and household size. These factors may be used for designing improved interventions for sustainable disease control and risk stratification. Housing instability, household mobility and migration patterns are key to understanding the process of house (re)infestation in the Gran Chaco.
Asunto(s)
Composición Familiar , Vivienda , Control de Insectos/estadística & datos numéricos , Insectos Vectores/crecimiento & desarrollo , Triatoma/crecimiento & desarrollo , Animales , Animales Domésticos , Argentina/epidemiología , Enfermedad de Chagas/epidemiología , Enfermedad de Chagas/prevención & control , Enfermedad de Chagas/transmisión , Enfermedades Transmisibles/epidemiología , Enfermedades Transmisibles/transmisión , Estudios Transversales , Ecosistema , Escolaridad , Emigración e Inmigración/estadística & datos numéricos , Femenino , Humanos , Control de Insectos/métodos , Insectos Vectores/parasitología , Insecticidas/administración & dosificación , Masculino , Oportunidad Relativa , Mascotas , Prevalencia , Población Rural/estadística & datos numéricos , Encuestas y Cuestionarios , Triatoma/parasitologíaRESUMEN
The competence of reservoir hosts of vector-borne pathogens is directly linked to its capacity to infect the vector. Domestic dogs and cats are major domestic reservoir hosts of Trypanosoma cruzi, and exhibit a much higher infectiousness to triatomines than seropositive humans. We quantified the concentration of T. cruzi DNA in the peripheral blood of naturally-infected dogs and cats (a surrogate of intensity of parasitemia), and evaluated its association with infectiousness to the vector in a high-risk area of the Argentinean Chaco. To measure infectiousness, 44 infected dogs and 15 infected cats were each exposed to xenodiagnosis with 10-20 uninfected, laboratory-reared Triatoma infestans that blood-fed to repletion and were later individually examined for infection by optical microscopy. Parasite DNA concentration (expressed as equivalent amounts of parasite DNA per mL, Pe/mL) was estimated by real-time PCR amplification of the nuclear satellite DNA. Infectiousness increased steeply with parasite DNA concentration both in dogs and cats. Neither the median parasite load nor the mean infectiousness differed significantly between dogs (8.1Pe/mL and 48%) and cats (9.7Pe/mL and 44%), respectively. The infectiousness of dogs was positively and significantly associated with parasite load and an index of the host's body condition, but not with dog's age, parasite discrete typing unit and exposure to infected bugs in a random-effects multiple logistic regression model. Real-time PCR was more sensitive and less time-consuming than xenodiagnosis, and in conjunction with the body condition index, may be used to identify highly infectious hosts and implement novel control strategies.
Asunto(s)
Enfermedades de los Gatos/diagnóstico , Enfermedad de Chagas/veterinaria , Reservorios de Enfermedades , Enfermedades de los Perros/diagnóstico , Triatoma/parasitología , Trypanosoma cruzi/aislamiento & purificación , Animales , Enfermedades de los Gatos/parasitología , Gatos , Enfermedad de Chagas/parasitología , ADN Satélite/genética , Enfermedades de los Perros/parasitología , Perros , Femenino , Humanos , Insectos Vectores/parasitología , Parasitemia/parasitología , Parasitemia/veterinaria , Reacción en Cadena en Tiempo Real de la Polimerasa , Trypanosoma cruzi/genética , Trypanosoma cruzi/patogenicidad , XenodiagnósticoRESUMEN
We conducted a cross-sectional survey of Trypanosoma cruzi infection of Triatoma infestans as well as dogs and cats in 327 households from a well-defined rural area in northeastern Argentina to test whether the household distribution of infection differed between local ethnic groups (Tobas and Creoles) and identify risk factors for host infection. Overall prevalence of infection of bugs (27.2%; 95% confidence interval = 25.3-29.3%), dogs (26.0%; 95% confidence interval = 23.3-30.1%), and cats examined (28.7%; 95% confidence interval = 20.2-39.0%) was similar. A multimodel inference approach showed that infection in dogs was associated strongly with the intensity and duration of local exposure to infected bugs and moderately with household ethnic background. Overall, Toba households were at a substantially greater risk of infection than Creole households. The strong heterogeneities in the distribution of bug, dog, and cat infections at household, village, and ethnic group levels may be used for targeted vector and disease control.
Asunto(s)
Enfermedades de los Gatos/epidemiología , Enfermedad de Chagas/veterinaria , Enfermedades de los Perros/epidemiología , Insectos Vectores/parasitología , Triatoma/parasitología , Trypanosoma cruzi/aislamiento & purificación , Animales , Argentina/epidemiología , Enfermedades de los Gatos/parasitología , Gatos , Enfermedad de Chagas/epidemiología , Estudios Transversales , Enfermedades de los Perros/parasitología , Perros , Composición Familiar , Femenino , Humanos , Masculino , Prevalencia , Factores de Riesgo , Población RuralRESUMEN
The role of rodents in the sylvatic transmission of Trypanosoma cruzi has seldom been investigated using parasitological and molecular methods. We assessed the occurrence of T. cruzi in wild small rodents from Pampa del Indio, in the Argentinean Chaco, and identified the taxonomic status of positive rodents by sequencing a fragment of cytochrome b gene (cytb) and performing BLAST searches and phylogenetic analyses. A total of 176 Sigmodontinae rodents was captured in six surveys using 5425 trap-nights in a wide range of sylvatic habitats between 2009 and 2011. Host infection was determined by xenodiagnosis and by polymerase chain reaction amplification of the hyper-variable region of kinetoplast DNA minicircles of T. cruzi (kDNA-PCR) from blood samples. None of the 176 rodents examined was xenodiagnosis-positive. The prevalence of infection determined by kDNA-PCR from blood samples was 16.2% (95% confidence interval, 10.1-21.9%). Half of the infections detected by kDNA-PCR were confirmed by nuclear satellite DNA-PCR or by kDNA-PCR of the rectal contents of xenodiagnostic bugs. The 24 positive specimens were assigned to eight species, providing the first records of T. cruzi in Akodon montensis, Akodon toba, Graomys chacoensis, and Oligoryzomys chacoensis. The occurrence of T. cruzi infection in Oligoryzomys nigripes, Calomys callosus, Necromys lasiurus and Oecomys sp. (most probably Oecomys mamorae) from the Gran Chaco is also reported for the first time. Although sigmodontine rodents were frequently infected, the intensity of bug rectal infection with T. cruzi was below the detection limit of xenodiagnosis (subpatent infectiousness to bugs), indicating they had a low reservoir host competence.
Asunto(s)
Enfermedad de Chagas/transmisión , Reservorios de Enfermedades/parasitología , Sigmodontinae/parasitología , Trypanosoma cruzi/aislamiento & purificación , Animales , Argentina/epidemiología , Enfermedad de Chagas/epidemiologíaRESUMEN
A four-year longitudinal study of the structure of sylvatic transmission cycles of Trypanosoma cruzi, reservoir host competence and parasite discrete typing units was conducted in a disturbed rural area of the humid Chaco in Argentina. Among 190 mammals examined by xenodiagnosis and polymerase chain reaction amplification, the composite prevalence of infection was substantially higher in Dasypus novemcinctus armadillos (57.7%) and Didelphis albiventris opossums (38.1%) than in Euphractus sexcinctus (20.0%), Tolypeutes matacus (12.5%), and Chaetophractus vellerosus (6.3%) armadillos. Trypanosoma cruzi was detected for the first time in Thylamys pusilla small opossums and in two unidentified small rodents. Infection was spatially aggregated only in armadillos. All Didelphis were infected with T. cruzi I and all armadillo species were infected with T. cruzi III, implying two distinct sylvatic cycles with no inputs from the domestic cycle. Dasypus armadillos and Didelphis opossums were much more infectious to vectors than other armadillos, small opossums, or rodents.
Asunto(s)
Animales Salvajes/parasitología , Enfermedad de Chagas/veterinaria , Reservorios de Enfermedades/parasitología , Árboles , Trypanosoma cruzi/aislamiento & purificación , Animales , Argentina/epidemiología , Armadillos/clasificación , Armadillos/parasitología , Enfermedad de Chagas/epidemiología , Enfermedad de Chagas/parasitología , Enfermedad de Chagas/transmisión , Insectos Vectores/parasitología , Estudios Longitudinales , Mamíferos/parasitología , Zarigüeyas/clasificación , Zarigüeyas/parasitología , Reacción en Cadena de la Polimerasa , Prevalencia , Triatoma/clasificación , Triatoma/parasitología , Trypanosoma cruzi/clasificación , Trypanosoma cruzi/genéticaRESUMEN
Domestic dogs and cats are major domestic reservoir hosts of Trypanosoma cruzi and a risk factor for parasite transmission. In this study we assessed the relative performance of a polymerase chain reaction assay targeted to minicircle DNA (kDNA-PCR) in reference to conventional serological tests, a rapid dipstick test and xenodiagnosis to detect T. cruzi infection in dogs and cats from an endemic rural area in northeastern Argentina. A total of 43 dogs and 13 cats seropositive for T. cruzi by an immunosorbent assay (ELISA) and an indirect hemagglutination assay (IHA), which had been examined by xenodiagnosis, were also tested by kDNA-PCR. kDNA-PCR was nearly as sensitive as xenodiagnosis for detecting T. cruzi-infectious dogs and cats. kDNA-PCR was slightly more sensitive than xenodiagnosis in seropositive dogs (91% versus 86%, respectively) and cats (77% against 54%, respectively), but failed to detect all of the seropositive individuals. ELISA and IHA detected all xenodiagnosis-positive dogs and both outcomes largely agreed (kappa coefficient, κ=0.92), whereas both assays failed to detect all of the xenodiagnosis-positive cats and their agreement was moderate (κ=0.68). In dogs, the sensitivity of the dipstick test was 95% and agreed closely with the outcome of conventional serological tests (κ=0.82). The high sensitivity of kDNA-PCR to detect T. cruzi infections in naturally infected dogs and cats supports its application as a diagnostic tool complementary to serology and may replace the use of xenodiagnosis or hemoculture.
Asunto(s)
Enfermedades de los Gatos/diagnóstico , Enfermedad de Chagas/veterinaria , Pruebas Diagnósticas de Rutina/métodos , Enfermedades de los Perros/diagnóstico , Parasitología/métodos , Trypanosoma cruzi/aislamiento & purificación , Medicina Veterinaria/métodos , Animales , Argentina , Enfermedades de los Gatos/parasitología , Gatos , Enfermedad de Chagas/diagnóstico , Enfermedad de Chagas/parasitología , Enfermedades de los Perros/parasitología , Perros , Técnicas de Diagnóstico Molecular/métodos , Sensibilidad y Especificidad , Pruebas Serológicas/métodos , Trypanosoma cruzi/genética , Trypanosoma cruzi/inmunologíaRESUMEN
The discrete typing units (DTUs) of Trypanosoma cruzi that infect domestic dogs and cats have rarely been studied. With this purpose we conducted a cross-sectional xenodiagnostic survey of dog and cat populations residing in 2 infested rural villages in Pampa del Indio, in the humid Argentine Chaco. Parasites were isolated by culture from 44 dogs and 12 cats with a positive xenodiagnosis. DTUs were identified from parasite culture samples using a strategy based on multiple polymerase-chain reactions. TcVI was identified in 37 of 44 dogs and in 10 of 12 cats, whereas TcV was identified in 5 dogs and in 2 cats -a new finding for cats. No mixed infections were detected. The occurrence of 2 dogs infected with TcIII -classically found in armadillos- suggests a probable link with the local sylvatic transmission cycle involving Dasypus novemcinctus armadillos and a potential risk of human infection with TcIII. Our study reinforces the importance of dogs and cats as domestic reservoir hosts and sources of various DTUs infecting humans, and suggests a link between dogs and the sylvatic transmission cycle of TcIII.
Asunto(s)
Enfermedades de los Gatos/parasitología , Enfermedad de Chagas/veterinaria , Enfermedades de los Perros/parasitología , Población Rural , Trypanosoma cruzi/clasificación , Trypanosoma cruzi/genética , Animales , Argentina/epidemiología , Enfermedades de los Gatos/epidemiología , Enfermedades de los Gatos/transmisión , Gatos , Enfermedad de Chagas/epidemiología , Enfermedad de Chagas/parasitología , Enfermedad de Chagas/transmisión , Reservorios de Enfermedades/parasitología , Enfermedades de los Perros/epidemiología , Enfermedades de los Perros/transmisión , Perros , Humanos , Insectos Vectores/parasitología , Triatoma/parasitología , Trypanosoma cruzi/aislamiento & purificación , XenodiagnósticoRESUMEN
We assessed the distribution of Trypanosoma cruzi Discrete Typing Units (DTUs) in domestic and peridomestic Triatoma infestans and Triatoma sordida specimens collected in a well-defined rural area in Pampa del Indio, northeastern Argentina. Microscopically-positive bugs were randomly selected with a multi-level sampling design, and DTUs were identified using direct PCR strategies. TcVI predominated in 61% of 69 T. infestans and in 56% of 9 T. sordida. TcV was the secondary DTU in T. infestans (16%) and was found in 1 T. sordida specimen (11%). Three T. sordida (33%) were found infected with TcI, a DTU also identified in local Didelphis albiventris opossums. Mixed DTU infections occurred rarely (5%) and were detected both directly from the bugs' rectal ampoule and parasite cultures. The identified DTUs and bug collection sites of T. infestans were significantly associated. Bugs infected with TcV were almost exclusively captured in domiciles whereas those with TcVI were found similarly in domiciles and peridomiciles. All mixed infections occurred in domiciles. TcV-infected bugs fed more often on humans than on dogs, whereas TcVI-infected bugs showed the reverse pattern. T. sordida is a probable sylvatic vector of TcI linked to D. albiventris, and could represent a secondary vector of TcVI and TcV in the domestic/peridomestic cycle.
Asunto(s)
Triatoma/parasitología , Trypanosoma cruzi/genética , Animales , Animales Domésticos/parasitología , Argentina , Perros , Ensayo de Inmunoadsorción Enzimática , Genotipo , Humanos , Insectos Vectores/parasitología , Reacción en Cadena de la PolimerasaRESUMEN
Little is known about the sylvatic transmission cycle of Trypanosoma cruzi in the Gran Chaco ecoregion. We conducted surveys to identify the main sylvatic hosts of T. cruzi, parasite discrete typing units and vector species involved in Pampa del Indio, a rural area in the humid Argentinean Chaco. A total of 44 mammals from 14 species were captured and examined for infection by xenodiagnosis and polymerase chain reaction amplification of the hyper-variable region of kinetoplast DNA minicircles of T. cruzi (kDNA-PCR). Ten (22.7%) mammals were positive by xenodiagnosis or kDNA-PCR. Four of 11 (36%) Didelphis albiventris (white-eared opossums) and six of nine (67%) Dasypus novemcinctus (nine-banded armadillos) were positive by xenodiagnosis and or kDNA-PCR. Rodents, other armadillo species, felids, crab-eating raccoons, hares and rabbits were not infected. Positive animals were highly infectious to the bugs that fed upon them as determined by xenodiagnosis. All positive opossums were infected with T. cruzi I and all positive nine-banded armadillos with T. cruzi III. Extensive searches in sylvatic habitats using 718 Noireau trap-nights only yielded Triatoma sordida whereas no bug was collected in 26 light-trap nights. Four armadillos or opossums fitted with a spool-and-line device were successfully tracked to their refuges; only one Panstrongylus geniculatus was found in an armadillo burrow. No sylvatic triatomine was infected with T. cruzi by microscopical examination or kDNA-PCR. Our results indicate that two independent sylvatic transmission cycles of T. cruzi occur in the humid Chaco. The putative vectors of both cycles need to be identified conclusively.