Author Correction: Surveillance of vector-borne pathogens under imperfect detection: lessons from Chagas disease risk (mis)measurement.

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Surveillance of vector-borne pathogens under imperfect detection: lessons from Chagas disease risk (mis)measurement.

Vector-borne pathogens threaten human health worldwide. Despite their critical role in disease prevention, routine surveillance systems often rely on low-complexity pathogen detection tests of uncertain accuracy. In Chagas disease surveillance, optical microscopy (OM) is routinely used for detecting Trypanosoma cruzi in its vectors. Here, we use replicate T. cruzi detection data and hierarchical site-occupancy models to assess the reliability of OM-based T. cruzi surveillance while explicitly accounting for false-negative and false-positive results. We investigated 841 triatomines with OM slides (1194 fresh, 1192 Giemsa-stained) plus conventional (cPCR, 841 assays) and quantitative PCR (qPCR, 1682 assays). Detections were considered unambiguous only when parasitologists unmistakably identified T. cruzi in Giemsa-stained slides. qPCR was >99% sensitive and specific, whereas cPCR was ~100% specific but only ~55% sensitive. In routine surveillance, examination of a single OM slide per vector missed ~50-75% of infections and wrongly scored as infected ~7% of the bugs. qPCR-based and model-based infection frequency estimates were nearly three times higher, on average, than OM-based indices. We conclude that the risk of vector-borne Chagas disease may be substantially higher than routine surveillance data suggest. The hierarchical modelling approach we illustrate can help enhance vector-borne disease surveillance systems when pathogen detection is imperfect.

Synanthropic triatomines as potential vectors of Trypanosoma cruzi in Central Brazil

Abstract INTRODUCTION: Chagas disease surveillance requires current knowledge on synanthropic triatomines. We analyzed the occurrence and Trypanosoma cruzi infection rates of triatomine bugs in central Brazil, during 2012-2014. METHODS: Triatomines were collected inside or around houses, and T. cruzi infection was determined by optical microscopy and conventional/quantitative polymerase chain reaction. RESULTS: Of the 2706 triatomines collected, Triatoma sordida was the most frequent species in Goiás State, whereas Panstrongylus megistus predominated in the Federal District. Parasites identified were T. cruzi, T. rangeli, and Blastocrithidia sp. CONCLUSIONS: P. megistus and T. sordida sustained the risk of T. cruzi transmission to humans in central Brazil.

Synanthropic triatomines as potential vectors of Trypanosoma cruzi in Central Brazil.

INTRODUCTION: Chagas disease surveillance requires current knowledge on synanthropic triatomines. We analyzed the occurrence and Trypanosoma cruzi infection rates of triatomine bugs in central Brazil, during 2012-2014. METHODS: Triatomines were collected inside or around houses, and T. cruzi infection was determined by optical microscopy and conventional/quantitative polymerase chain reaction. RESULTS: Of the 2706 triatomines collected, Triatoma sordida was the most frequent species in Goiás State, whereas Panstrongylus megistus predominated in the Federal District. Parasites identified were T. cruzi, T. rangeli, and Blastocrithidia sp. CONCLUSIONS: P. megistus and T. sordida sustained the risk of T. cruzi transmission to humans in central Brazil.

Vector-borne transmission of Trypanosoma cruzi among captive Neotropical primates in a Brazilian zoo.

BACKGROUND: Neotropical primates are important sylvatic hosts of Trypanosoma cruzi, the etiological agent of Chagas disease. Infection is often subclinical, but severe disease has been described in both free-ranging and captive primates. Panstrongylus megistus, a major T. cruzi vector, was found infesting a small-primate unit at Brasília zoo (ZooB), Brazil. ZooB lies close to a gallery-forest patch where T. cruzi circulates naturally. Here, we combine parasitological and molecular methods to investigate a focus of T. cruzi infection involving triatomine bugs and Neotropical primates at a zoo located in the Brazilian Savannah. METHODS: We assessed T. cruzi infection in vectors using optical microscopy (n = 34) and nested PCR (n = 50). We used quantitative PCR (qPCR) to examine blood samples from 26 primates and necropsy samples from two primates that died during the study. We determined parasite lineages in five vectors and two primates by comparing glucose-6-phosphate isomerase (G6pi) gene sequences. RESULTS: Trypanosoma cruzi was found in 44 vectors and 17 primates (six genera and eight species); one Mico chrysoleucus and one Saguinus niger had high parasitaemias. Trypanosoma cruzi DNA was detected in three primates born to qPCR-negative mothers at ZooB and in the two dead specimens. One Callithrix geoffroyi became qPCR-positive over a two-year follow-up. All G6pi sequences matched T. cruzi lineage TcI. CONCLUSIONS: Our findings strongly suggest vector-borne T. cruzi transmission within a small-primate unit at ZooB - with vectors, and perhaps also parasites, presumably coming from nearby gallery forest. Periodic checks for vectors and parasites would help eliminate T. cruzi transmission foci in captive-animal facilities. This should be of special importance for captive-breeding programs involving endangered mammals, and would reduce the risk of accidental T. cruzi transmission to keepers and veterinarians.

Occurrence of synanthropic triatomines (Hemiptera: Reduviidae) in the Federal District of Brazil.

INTRODUCTION: Entomological surveillance of Chagas disease in the Federal District of Brazil (DF), has recorded the following triatomine species: Panstrongylus megistus, P. geniculatus, P. diasi, Rhodnius neglectus, Triatoma pseudomaculata, and T. sordida. We aimed to analyze the spatial and temporal occurrence of triatomine species collected in DF, and their indices of natural infection with trypanosomes. METHODS: The Health State Secretariat of DF recorded triatomines between 2002 and 2010 in 20 administrative regions. This retrospective analysis considered the number of adults and nymphs of each species collected and infected in both intradomicile and peridomicile. RESULTS: A total of 754 triatomines were collected in 252 reported domiciles. Panstrongylus megistus was the most frequent species (65%), followed by T. pseudomaculata (14%). Of the 309 examined insects, only 3 (1%) specimens of P. megistus were infected with flagellates morphologically similar to Trypanosoma cruzi. The spatial occurrence indicated a higher diversity of triatomines and frequency of T. sordida in rural areas. Moreover, there was a predominance of P. megistus in urban areas. The number of records of P. megistus in the rainy season was two times higher than that during the dry season. The largest number of triatomines was collected in November. CONCLUSIONS: The presence of P. megistus specimens infected with trypanosomes in domiciles, shows the potential risk of human infection in DF. Thus, it is essential to continue entomological surveillance, intensifying it in the rainy season and in regions of greater occurrence.

Occurrence of synanthropic triatomines (Hemiptera: Reduviidae) in the Federal District of Brazil / Ocorrência de triatomíneos sinantrópicos (Hemiptera: Reduviidae) no Distrito Federal, Brasil

INTRODUCTION: Entomological surveillance of Chagas disease in the Federal District of Brazil (DF), has recorded the following triatomine species: Panstrongylus megistus, P. geniculatus, P. diasi, Rhodnius neglectus, Triatoma pseudomaculata, and T. sordida. We aimed to analyze the spatial and temporal occurrence of triatomine species collected in DF, and their indices of natural infection with trypanosomes. METHODS: The Health State Secretariat of DF recorded triatomines between 2002 and 2010 in 20 administrative regions. This retrospective analysis considered the number of adults and nymphs of each species collected and infected in both intradomicile and peridomicile. RESULTS: A total of 754 triatomines were collected in 252 reported domiciles. Panstrongylus megistus was the most frequent species (65 percent), followed by T. pseudomaculata (14 percent). Of the 309 examined insects, only 3 (1 percent) specimens of P. megistus were infected with flagellates morphologically similar to Trypanosoma cruzi. The spatial occurrence indicated a higher diversity of triatomines and frequency of T. sordida in rural areas. Moreover, there was a predominance of P. megistus in urban areas. The number of records of P. megistus in the rainy season was two times higher than that during the dry season. The largest number of triatomines was collected in November. CONCLUSIONS: The presence of P. megistus specimens infected with trypanosomes in domiciles, shows the potential risk of human infection in DF. Thus, it is essential to continue entomological surveillance, intensifying it in the rainy season and in regions of greater occurrence.

INTRODUÇÃO: As espécies de triatomíneos registradas pela vigilância entomológica da doença de Chagas no Distrito Federal (DF), Brasil, são Panstrongylus megistus, Panstrongylus geniculatus, Panstrongylus diasi, Rhodnius neglectus, Triatoma pseudomaculata e Triatoma sordida. Nosso objetivo foi analisar a ocorrência espacial e temporal das espécies de triatomíneos coletadas no DF, assim como seus índices de infecção natural por tripanosomatídeos. MÉTODOS: Os triatomíneos foram registrados pela Secretaria de Saúde do DF, entre 2002 e 2010, em 20 regiões administrativas. Esta análise retrospectiva considerou o número de adultos e ninfas coletados e infectados de cada espécie no intra e peridomicílio. RESULTADOS: Ao todo, foram coletados 754 triatomíneos em 252 unidades domiciliares notificadas. Panstrongylus megistus foi a espécie mais frequente (65 por cento), seguida de T. pseudomaculata (14 por cento). Dos 309 triatomíneos examinados, somente 3 (1 por cento) espécimes de P. megistus estavam infectados por flagelados morfologicamente similares a Trypanosoma cruzi. A ocorrência espacial mostrou que houve maior diversidade de triatomíneos e maior frequência de T. sordida em áreas rurais. Além disso, houve predominância de P. megistus nas áreas urbanas. O número de registros de P. megistus no período chuvoso foi duas vezes maior que no período seco, sendo o maior número de coletas observado no mês de novembro. CONCLUSÕES: A presença de espécimes de P. megistus infectados por tripanosomatídeos em domicílios evidencia o potencial risco de infecção humana no DF. Dessa forma, é fundamental que continue a vigilância entomológica, intensificando-a no período chuvoso e nas regiões onde há maior ocorrência.

Effects of climate and different management strategies on Aedes aegypti breeding sites: a longitudinal survey in Brasília (DF, Brazil).

OBJECTIVE: To determine the influence of climate and of environmental vector control with or without insecticide on Aedes aegypti larval indices and pupae density. METHODS: An 18-month longitudinal survey of infestation of Ae. aegypti immature stages was conducted for the 1015 residences (premises) of Vila Planalto, an area of Brasilia where the Breteau Index was about 40 before the study. This area was divided into five zones: a control zone with environmental management alone and four zones with insecticide treatment (methoprene, Bti, temephos). We tested for significant differences between infestation levels in the control and insecticide-treated areas, for relationships between climatic variables and larval indices, and to determine risk factors of infestation for certain types of premises and containers. RESULTS: Environmental vector control strategies dramatically decreased infestation in the five areas. No significant differences could be detected between control strategies with insecticide and without. Some premises and container types were particularly suitable for breeding. The influence of climate on the emergence of Ae. aegypti adults for the area is described. CONCLUSION: In a moderately infested area such as Brasilia, insecticides do not improve environmental vector control. Rather, infestations could be further reduced by focusing on residences and containers particularly at risk. The nature of the link between climate and larval population should be investigated in larger-scale studies before being used in forecasting models.

[Susceptibility of Aedes aegypti larvae to the insecticide temephos in the Federal District, Brazil]. / Suscetibilidade de larvas de Aedes aegypti ao inseticida temefós no Distrito Federal.

OBJECTIVE: To study the susceptibility status of Aedes aegypti to the organophosphate insecticide temephos. METHODS: Samples of Ae. aegypti larvae were obtained, using ovitraps, from eight cities of the Federal District, central Brazil, in 2000 and 2001. Larvae were submitted to the diagnostic dose of 0.012 mg/l temephos, as recommended by standard World Health Organization methodology. Field populations were tested in parallel with reference strains Rockefeller and DIVAL, from the Environmental Surveillance Directory (DIVAL) insectary. The concentration and purity of temephos solutions were verified by gas chromatography. Correlation calculations were performed using StatView - SAS Institute Inc., version 5. Student's t test was used for detecting differences in susceptibility, with significance levels of alpha=0.05. RESULTS: In 2000, Ae. aegypti larvae populations from Taguatinga, Guara, and Nucleo Bandeirante showed resistance to temephos, with mortality ranging from 54.1 to 63.4%. The populations from Gama, Planaltina, and Sobradinho showed altered levels of susceptibility (mortality ranging from 83.6 to 92.8%). The population from Ceilandia was the only susceptible one, with 98% mortality. In 2001, all populations tested were resistant (44.4 to 66.4% mortality). No significant correlation was found between the susceptibility of populations and the distance between the cities of origin, or the amount of insecticide applied in the years preceding the study. CONCLUSIONS: Ae. aegypti susceptibility to temephos is changing in the Federal District. It is essential to continue monitoring the resistance of this vector to insecticides in order to ensure the efficiency of programs aimed at vector control and at the protection of human health.

Suscetibilidade de larvas de Aedes aegypti ao inseticida temefós no Distrito Federal / Susceptibility of Aedes aegypti larvae to the insecticide temephos in the Federal District, Brazil

OBJETIVO: Estudar o padrão de suscetibilidade do Aedes aegypti ao inseticida organofosforado temefós. MÉTODOS: Amostras de larvas de Ae. aegypti foram obtidas com armadilhas para oviposição, em oito cidades do Distrito Federal, nos anos 2000 e 2001. As larvas foram submetidas à dose diagnóstica de 0,012 mg/l de temefós, segundo metodologia padronizada pela Organização Mundial da Saúde. As populações de campo foram testadas em paralelo com a cepa de referência Rockefeller e a cepa DIVAL, do insetário da Diretoria de Vigilância Ambiental. A concentração e a pureza das soluções de temefós foram analisadas por cromatografia gasosa. Os cálculos de correlação foram determinados pelo programa StatView - SAS Institute Inc., versão 5. Utilizou-se o teste t de Student para verificar diferenças de suscetibilidade, com níveis de significância, alfa=0,05. RESULTADOS: Em 2000, as populações de larvas de Ae. aegypti nas cidades de Taguatinga, Guará e Núcleo Bandeirante apresentaram-se resistentes ao temefós, com mortalidade de larvas entre 54,1 e 63,4 por cento. As populações do Gama, Planaltina e Sobradinho apresentaram alterações nos níveis de suscetibilidade (mortalidade de 83,6 a 92,8 por cento). A população de Ceilândia foi a única suscetível, com 98 por cento de mortalidade. Em 2001, todas as populações testadas mostraram-se resistentes (44,4 a 66,4 por cento de mortalidade). Nenhuma correlação significativa foi encontrada entre a suscetibilidade das populações e a distância entre essas cidades ou a quantidade de inseticida aplicado nos anos anteriores ao estudo. CONCLUSÕES: Os níveis de suscetibilidade do Ae. aegypti ao temefós vêm se alterando no Distrito Federal. É essencial a continuidade de programas de monitoramento da resistência desse vetor aos inseticidas para se garantir a eficiência dos programas de controle e a proteção da saúde humana.