Genetic diversity and Kdr mutations of natural Aedes (Stegomyia) aegypti (Diptera: Culicidae) populations of Brazil

ABSTRACT Aedes (Stegomyia) aegypti is an important vector of dengue, yellow fever, chikungunya and Zika virus. It is well known that resistance monitoring and genetic diversity data help designing the vector control programs. This study aimed to evaluate resistance to pyrethroids (PYs) through the frequency of kdr mutations Val1016IIe and F1534C, and the genetic variation of the mitochondrial gene ND4 in six natural populations of A. aegypti from Paraná - Brazil. Adults were obtained from eggs collected from Alvorada do Sul, Marilena, Maringá, Nova Londrina, Paranavaí and São Carlos do Ivaí. From these adults, 345 were used to identify the 1016 and 1534 sites, and 120 were used to perform the ND4 gene analysis. The studied populations from Paraná showed PYs resistance, low gene flow and genetic diversity. Additionally, a relationship was observed among the haplotypes of populations from the Amazon and Southeastern Brazil, Peru, Mexico, and North America.

Dispersion routes of the main vectors of human malaria in the Americas: Genetic evidence from the mitochondrial COI gene.

BACKGROUND AND OBJECTIVES: In America, of the 44 species of Anopheles, nine are main vectors of malaria and, of these, genetic information exists for seven. Hence, this study sought to know the gene flow and diversity of the seven principal vectors of malaria at the Americas level. METHODS: For the seven species and the sequences of the mitochondrial cytochrome c oxidase I (COI) gene obtained from the GenBank and Bold System, genetic analyzes of populations and genetic structure were performed and haplotype networks and phylogenetic trees were obtained. RESULTS: For the seven species, 1440 sequences were analyzed and 519 haplotypes were detected. The Hd and π values were higher within a continental context than by countries. Neutrality tests indicated positive and negative values with most of these being significant (p < 0.05). Phylogenetic analyses for all the species recovered three clades with no geographic pattern among them. INTERPRETATION & CONCLUSION: Studies suggest that native species of Anopheles from the Americas have greater haplotype diversity and low genetic differentiation due to the lack of physical barriers to impede gene flow among these populations. Moreover, all the species are interconnected by roadways. This scenario complicates the epidemiological picture of malaria in the Americas.

Gene Flow Patterns of the Aedes aegypti (Diptera: Culicidae) Mosquito in Colombia: a Continental Comparison Suggests Multiple Invasion Routes and Gene Exchange

ABSTRACT In Colombia Aedes aegypti is present in 80% of the country up to 2,300 m; however, little is known of its genetic relations within a country context and, hence, within a broader context, for example, America. The aforementioned, herein, analyzed the gene flow within a context of the Americas, its directionality and genetic diversity of the mitochondrial lineages in the A. aegypti populations for Colombia. This called for the use of the sequences for A. aegypti available of the mitochondrial ND4 gene in the GenBank for Colombia and the American continent. No presence was found of nuclear mitochondrial pseudogenes (NUMTs) for Colombia. It is estimated that in Colombia the gene flow of the A. aegypti populations is occurring from the southeast and northeast toward the center of the country. In comparison with the mitochondrial sequences for America, the vector's haplotypes in Colombia suggest connections between the populations of mosquitoes from the south with those from the north of the continent. The gene flow model at continental scale suggests bidirectional connections between the populations from the north of the continent with those from the south, while at South American scale it proposes the gene flow in all the directions with respect to the Colombian. The Colombian A. aegypti vector monitoring and control strategies must pay special attention to the vector's points of entry into Colombia related with Peru, Venezuela, Brazil, Mexico, and North America to avoid the entry of populations with characteristics like resistance to insecticides or vector competition.

Potential geographic distribution of the tiger mosquito Aedes albopictus (Skuse, 1894) (Diptera: Culicidae) in current and future conditions for Colombia.

In Colombia, little is known on the distribution of the Asian mosquito Aedes albopictus, main vector of dengue, chikungunya, and Zika in Asia and Oceania. Therefore, this work sought to estimate its current and future potential geographic distribution under the Representative Concentration Paths (RCP) 2.6 and 8.5 emission scenarios by 2050 and 2070, using ecological niche models. For this, predictions were made in MaxEnt, employing occurrences of A. albopictus from their native area and South America and bioclimatic variables of these places. We found that, from their invasion of Colombia to the most recent years, A. albopictus is present in 47% of the country, in peri-urban (20%), rural (23%), and urban (57%) areas between 0 and 1800 m, with Antioquia and Valle del Cauca being the departments with most of the records. Our ecological niche modelling for the currently suggests that A. albopictus is distributed in 96% of the Colombian continental surface up to 3000 m (p < 0.001) putting at risk at least 48 million of people that could be infected by the arboviruses that this species transmits. Additionally, by 2050 and 2070, under RCP 2.6 scenario, its distribution could cover to nearly 90% of continental extension up to 3100 m (≈55 million of people at risk), while under RCP 8.5 scenario, it could decrease below 60% of continental extension, but expand upward to 3200 m (< 38 million of people at risk). These results suggest that, currently in Colombia, A. albopictus is found throughout the country and climate change could diminish eventually its area of distribution, but increase its altitudinal range. In Colombia, surveillance and vector control programs must focus their attention on this vector to avoid complications in the national public health setting.

The Mayaro virus and its potential epidemiological consequences in Colombia: an exploratory biomathematics analysis.

BACKGROUND: Mayaro virus (Togaviridae) is an endemic arbovirus of the Americas with epidemiological similarities with the agents of other more prominent diseases such as dengue (Flaviviridae), Zika (Flaviviridae), and chikungunya (Togaviridae). It is naturally transmitted in a sylvatic/rural cycle by Haemagogus spp., but, potentially, it could be incorporated and transmitted in an urban cycle by Aedes aegypti, a vector widely disseminated in the Americas. METHODS: The Mayaro arbovirus dynamics was simulated mathematically in the colombian population in the eight biogeographical provinces, bearing in mind the vector's population movement between provinces through passive transport via truck cargo. The parameters involved in the virus epidemiological dynamics, as well as the vital rates of Ae. aegypti in each of the biogeographical provinces were obtained from the literature. These data were included in a meta-population model in differential equations, represented by a model structured by age for the dynamic population of Ae. aegypti combined with an epidemiological SEI/SEIR-type model. In addition, the model was incorporated with a term of migration to represent the connectivity between the biogeographical provinces. RESULTS: The vital rates and the development cycle of Ae. aegypti varied between provinces, having greater biological potential between 23 °C and 28 °C in provinces of Imerí, biogeographical Chocó, and Magdalena, with respect to the North-Andean Moorland (9.33-21.38 °C). Magdalena and Maracaibo had the highest flow of land cargo. The results of the simulations indicate that Magdalena, Imerí, and biogeographical Chocó would be the most affected regarding the number of cases of people infected by Mayaro virus over time. CONCLUSIONS: The temperature in each of the provinces influences the local population dynamics of Ae. aegypti and passive migration via transport of land cargo plays an important role on how the Mayaro virus would be disseminated in the human population. Once this arbovirus begins an urban cycle, the most-affected departments would be Antioquia, Santander, Norte de Santander, Cesar (Provinces of Magdalena), and Valle del Cauca, and Chocó (biogeographical province of Chocó), which is why vector control programmes must aim their efforts at these departments and include some type of vector control to the transport of land cargo to avoid a future Mayaro epidemic.

Effect of altitude on wing metric variation of Aedes aegypti (Diptera: Culicidae) in a region of the Colombian Central Andes.

In mosquitoes of medical importance, wing shape and size can vary with altitude, an aspect that can influence dispersion and, consequently, their vector capacity. Using geometric morphometry analysis, Aedes aegypti wing size and shape variation of males and females was studied in four altitudes in the second-smallest department in Colombia: 1,200 m (Tebaida), 1,400 m (Armenia), 1,500 m (Calarcá), and 1,700 m (Filandia). Wing shape in males (P < 0.001) and females (P < 0.001) was significantly different through the altitudinal gradient; in turn, wing size in males followed the altitudinal gradient males (R2 = 0.04946, P = 0.0002), females (R2 = 0.0011, P = 0.46). Wing allometry for males (P < 0.001) and females (P < 0.001) was significant. Likewise, the shape and size of the wings of males (P < 0.001) and females (P < 0.001) had significant fluctuating asymmetry. It is concluded that, in a small scale with an altitudinal variation of 500 meters, it is detected that the size and shape of the wings varied in A. aegypti, main vector the agents that cause dengue, chikungunya, and Zika. The fluctuating asymmetry is present in the individuals studied and could be associated with environmental effects caused by vector control campaigns present in some sampling locations.

Control de Aedes (Stegomyia) aegypti utilizando Bacillus thuringiensis var. israelensis en Armenia, Quindío, Colombia / Control of Aedes (Stegomyia) aegypti using Bacillus thuringiensis var. israelensis in Armenia, Quindío, Colombia

RESUMEN En Colombia, Aedes aegypti es resistente a la mayoría de insecticidas utilizados. Debido al lento desarrollo de resistencia a Bacillus thuringiensis var. israelensis (Bti), así como su alta especificidad e inocuidad ambiental, el uso de este larvicida, se torna una alternativa en el manejo de este vector. En este trabajo, se evaluó experimentalmente y describió por medio de un modelo matemático, la dinámica del control de poblaciones naturales de A. aegypti, utilizando Bti. Se determinó el perfil de susceptibilidad, a través de bioensayos dosis-respuesta con larvas colectadas de Armenia (Quindío, Colombia). Adicionalmente, con los datos de mortalidad de las localidades analizadas, un nuevo análisis fue realizado, para estimar el perfil de susceptibilidad del municipio de Armenia. Los datos de mortalidad fueron utilizados para calcular las concentraciones letales 50 y 95. Con éstas, se realizaron simulaciones hipotéticas del comportamiento del vector, obtenidas a partir de un modelo matemático, que describe la dinámica poblacional, usando aplicaciones sucesivas de Bti y diferentes intervalos de tiempo. Los bioensayos dosis-respuesta indican que las poblaciones del vector analizadas son susceptibles al Bti, por presentar una respuesta biológica similar a la obtenida en la cepa de referencia Rockefeller. Las simulaciones aplicando un control periódico sostenido, sugieren que el Bti es efectivo para controlar el vector; sin embargo, su eficiencia a largo plazo depende de la relación entre concentración letal y frecuencia de aplicación. Se concluye que la aplicación sostenida de Bti constituye una alternativa viable para el control de poblaciones de A. aegypti, a largo plazo.

ABSTRACT In Colombia, Aedes aegypti is resistant to most used insecticides. Due to the slow development of resistance to Bacillus thuringiensis var. israelensis (Bti) as well as its high specificity and environmental safety, the use of this larvicide becomes an alternative in the management of this vector. In this work, we evaluated experimentally and describe by a mathematical model the dyamics of control of natural populations of A. aegypti using Bti. The susceptibility profile to Bti was determined through dose-response bioassays with larvae collected in Armenia (Quindío, Colombia). In addition, in order to estimate the susceptibility profile, an analysis was carried out using the mortality data obtained from the four localities analyzed. The mortality data were used to estimate the lethal concentrations (LC50 and 95) from each locality. Using these LC, hypothetical simulations of vector behavior were carried out, obtained from a mathematical model that describes the population dynamics, using successive applications of Bti at different time intervals. The dose-response bioassays indicate tha the analyzed vector populations are susceptible to Bti since they present a biological response similar to the one obtained from A. aegypti Rockefeller strain. Computer simulations using sustained periodic inspection indicate Bti is effective for the vector control. Nevertheless, its long-term efficiency depends on relation between the LC and the frequency of application. It is concluded that the sustained application of Bti represents a long-term viable alternative for the control of A. aegypti populations.

How much is known about the genetic diversity of the Asian tiger mosquito? A systematic review / ¿Cuánto se conoce acerca de la diversidad genética del mosquito tigre? Una revisión sistemática

ABSTRACT Introduction: Aedes (Stegomyia) albopictus (Skuse, 1894) is a vector for dengue and chikungunya viruses in the field, along with around 24 additional arboviruses under laboratory conditions. Knowledge of the genetic diversity of insect vectors is critical for the effective control and elimination of vector-borne diseases. Objective: We determined the current scenario of the genetic diversity in natural populations of A. albopictus through a systematic review. Methodology: It was possible to establish the first reports and distribution of A. albopictus populations in the world, as well as its genetic diversity, population genetic structure and molecular markers used to determine its genetic diversity. Results: A. albopictus is distributed worldwide with genetically structured populations and low diversity; however, 89.5% of the genetic diversity known is based on the use of RFLP, allozymes, isozymes, and mtDNA molecular markers that exhibit significant problems according to the literature. After the results were obtained, a critical analysis was carried out and existing shortcomings were detected. Conclusion: The current knowledge of genetic diversity of A. albopictus is based on genetic markers that exhibit significant problems reported in the literature; therefore, vector control programs targeting A. albopictus populations, may be compromised.

RESUMEN Introducción: Aedes (Stegomyia) albopictus (Skuse, 1894) es un vector para los virus del dengue y chicunguña en la naturaleza, junto con cerca de 24 arbovirus en condiciones de laboratorio. El conocimiento de la diversidad genética de los insectos vectores es fundamental para el control eficaz y la eliminación de enfermedades transmitidas por estos. Objetivo: Aquí se determinó el escenario actual de la diversidad genética en poblaciones naturales de A. albopictus a través de una revisión sistemática. Metodología: Se pudieron establecer los primeros registros y distribución de las poblaciones de A. albopictus en el mundo, así como su diversidad genética, estructura genética poblacional y marcadores moleculares utilizados para determinar su diversidad genética. Resultados: A. albopictus se distribuye en todo el mundo con poblaciones genéticamente estructuradas y baja diversidad; Sin embargo, el 89,5% de la diversidad genética conocida se basa en el uso de RFLP, aloenzimas, isoenzimas y marcadores moleculares mitocondriales que presentan problemas significativos según la literatura. Una vez obtenidos los resultados, se realizó un análisis crítico y se detectaron deficiencias existentes. Conclusión: El conocimiento actual de la diversidad genética de A. albopictus se basa en marcadores genéticos que presentan problemas significativos reportados en la literatura; Por lo tanto, los programas de control de vectores dirigidos a las poblaciones de A. albopictus pueden verse comprometidos.

First report of the Phe1534Cys kdr mutation in natural populations of Aedes albopictus from Brazil.

BACKGROUND: Knockdown resistance (kdr), caused by alterations in the voltage-gated sodium channel (NaV), is one of the mechanisms responsible for pyrethroid (PY) resistance. In the Asian tiger mosquito, Aedes albopictus, at least four different mutations were described in the IIIS6 NaV segment in populations from Asia, North America and Europe. In contrast, in Aedes aegypti at least 12 non-synonymous mutations have been reported at nine different codons, mostly in the IIS6 and IIIS6 NaV segments. The Phe1534Cys kdr mutation in the IIIS6 NaV segment is the most prevalent in populations of Ae. aegypti worldwide, also found in Ae. albopictus from Singapore. Herein, we investigated the DNA diversity corresponding to the IIS6 and IIIS6 NaV segments in natural populations of Ae. albopictus from Brazil. METHODS: DNA from eight Brazilian Ae. albopictus natural populations were individually extracted and pooled by states of origin, amplified, cloned and sequenced for the corresponding IIS6 and IIIS6 NaV segments. Additionally, samples from each location were individually genotyped by an allelic specific PCR (AS-PCR) approach to obtain the genotypic and allelic frequencies for the 1534 NaV site. RESULTS: No non-synonymous substitutions were observed in the IIS6 sequences. However, the Phe1534Cys kdr mutation was evidenced in the Ae. albopictus NaV IIIS6 segment sequences from Paraná (PR) and Rondônia (RO) states, but not from Mato Grosso (MT) state. The 1534Cys kdr allele varied from 3% (Marilena/PR and Porto Velho/RO) to 10% (Foz do Iguaçu/PR). To our knowledge, this paper reports the first occurrence and provides distribution data of a possible kdr mutation in Ae. albopictus in South America. CONCLUSION: The emergence of a likely kdr mutation in Ae. albopitus natural populations is a signal of alert for vector control measures since PY are the most popular insecticides adopted by residents. Additionally, once the kdr allele is present, its frequency tends to increase faster under exposition to those compounds. Although the Asian tiger mosquito is not incriminated as an important vector of dengue, chikungunya and Zika viruses in South America, its importance in this regard has been extensively discussed since Ae. albopictus is rapidly spreading and can also migrate between sylvatic and urban environments. Therefore, insecticide resistance monitoring initiatives should also be extended to Ae. albopictus in Brazil in order to maintain chemical compounds as an efficient vector control tool when needed.

Contrasting patterns of insecticide resistance and knockdown resistance (kdr) in Aedes aegypti populations from Jacarezinho (Brazil) after a Dengue Outbreak

ABSTRACT After a dengue outbreak, the knowledge on the extent, distribution and mechanisms of insecticide resistance is essential for successful insecticide-based dengue control interventions. Therefore, we evaluated the potential changes to insecticide resistance in natural Aedes aegypti populations to Organophosphates (OP) and Pyrethroids (PY) after chemical vector control interventions. After a Dengue outbreak in 2010, A. aegypti mosquitoes from the urban area of Jacarezinho (Paraná, Brazil) were collected in 2011 and 2012. Insecticide resistance to OP Temephos was assessed in 2011 and 2012 by dose–response bioassays adopting WHO-based protocols. Additionally, in both sampling, PY resistance was also investigated by the Val1016Ile mutation genotyping. In 2011, a random collection of mosquitoes was carried out; while in 2012, the urban area was divided into four regions where mosquitoes were sampled randomly. Bioassays conducted with larvae in 2011 (82 ± 10%; RR95 = 3.6) and 2012 (95 ± 3%; RR95 = 2.5) indicated an incipient altered susceptibility to Temephos. On the other hand, the Val1016IIe mutation analysis in 2011, presented frequencies of the 1016Ilekdr allele equal to 80%. Nevertheless, in 2012, when the urban area of Jacarezinho was analyzed as a single unit, the frequency of the mutant allele was 70%. Additionally, the distribution analysis of the Val1016Ile mutation in 2012 showed the mutant allele frequencies ≥60% in all regions. These outcomes indicated the necessity of developing alternative strategies such as insecticide rotations for delaying the evolution of resistance.

ESTUDIO DEMOGRÁFICO DE Emilia sonchifolia (ASTERACEAE) EN UNA FINCA CAFETERA DE ARMENIA, QUINDÍO, COLOMBIA / Demographic study of Emilia sonchifolia (Asteraceae) in a coffee farm in Armenia, Quindío, Colombia.

Se realizó un estudio con el fin de determinar la estructura demográfica de Emilia sonchifolia (L.) DC en una finca cafetera del Municipio de Armenia, Quindío, Colombia, donde se recolectaron datos durante cuatro semanas, en tres sitios: exterior, borde e interior del cultivo. Usando parámetros calculados a partir de los datos de campo, se construyó un modelo logístico para describir el comportamiento poblacional de E. sonchifolia en el tiempo. Se encontraron diferencias significativas en las variables: número de individuos por estado etario en el tiempo, porcentaje de mortalidad, tiempo de cambio del estado plántula a juvenil y de juvenil a adulto, número de hojas y de ramas; no se encontraron diferencias significativas en la densidad poblacional, número de inflorescencias e infrutescencias en los sitios de estudio. En general, se puede atribuir este comportamiento a la estrategia de reproducción r que sigue E. sonchifolia. Finalmente, las simulaciones hechas a partir del modelo logístico sugieren que la especie tiende a desaparecer si alguno de los estados etarios no está presente inicialmente; así, una alternativa plausible para el control sería su eliminación en el estado juvenil. Los resultados ofrecen alternativas con respecto al manejo de poblaciones de arvenses.

A research study was conducted to determine the demographic structure of Emilia sonchifolia L. in a coffee plantation in Armenia, Quindío, Colombia. Data were collected over a period of four weeks on three sites: inside, at the border and outside a coffee farm. A logistic population model was built to describe the population behavior of E. sonchifolia over time. Statiscally significant differences were found between: number of individuals per life stage in time, mortality rate, transition time from seedling to juvenile and from juvenile to adult; and number of leaves and branches. There was no evidence for statistically significant differences in population density or in number of inflorescences and fruits between study sites. In general, the observed behavior may be attributed to the r strategy used by this species. Finally, our results suggest the survival of the species is conditioned by the presence of all life stages at the beginning of each simulation based on the logistic model; so, a potential strategy for its controlling would require the removal during the juvenile stage. The considerations offer alternatives regarding weed population management.