Updated Anopheles mosquitos abundance and distribution in north-eastern malaria-free area of Argentina.

Malaria is the most important parasitic disease worldwide. In 2019, more than 679,441 cases of malaria were reported in the American region. During this study, Argentina was in malaria pre-elimination autochthonous transmission phase with the aim of being declared as malaria-free country. The aim of this work was to assess the influence of remote sensing spectral indices (NDVI, NDWI) and climatic variables (temperature, relative humidity and precipitation) on the distribution and abundance of Anopheles mosquitoes, in four localities with different degrees of anthropogenic disturbance and with previous malaria cases records located , in a historical malarious area in northeastern of Argentina. Between June 2012 and July 2014, mosquitoes were collected. We collected 535 Anopheles adult mosquitoes. Anopheles strodei s.l. was the most abundant species. The greatest richness, diversity and abundance of species were registered in wild and semi-urban environments. The abundance of Anopheles presented a negative association with relative humidity and mean temperature, but positive with mean maximum temperature. The most important variables determining Anopheles total abundance and distribution were NDWI Index and distance to vegetation. The abundance of An. strodei s.l., was positive associated with water areas whereas the NDVI Index was negatively associated.

Cost-Effective Method to Perform SARS-CoV-2 Variant Surveillance: Detection of Alpha, Gamma, Lambda, Delta, Epsilon, and Zeta in Argentina.

SARS-CoV-2 variants with concerning characteristics have emerged since the end of 2020. Surveillance of SARS-CoV-2 variants was performed on a total of 4,851 samples from the capital city and 10 provinces of Argentina, during 51 epidemiological weeks (EWs) that covered the end of the first wave and the ongoing second wave of the COVID-19 pandemic in the country (EW 44/2020 to EW 41/2021). The surveillance strategy was mainly based on Sanger sequencing of a Spike coding region that allows the identification of signature mutations associated with variants. In addition, whole-genome sequences were obtained from 637 samples. The main variants found were Gamma and Lambda, and to a lesser extent, Alpha, Zeta, and Epsilon, and more recently, Delta. Whereas, Gamma dominated in different regions of the country, both Gamma and Lambda prevailed in the most populated area, the metropolitan region of Buenos Aires. The lineages that circulated on the first wave were replaced by emergent variants in a term of a few weeks. At the end of the ongoing second wave, Delta began to be detected, replacing Gamma and Lambda. This scenario is consistent with the Latin American variant landscape, so far characterized by a concurrent increase in Delta circulation and a stabilization in the number of cases. The cost-effective surveillance protocol presented here allowed for a rapid response in a resource-limited setting, added information on the expansion of Lambda in South America, and contributed to the implementation of public health measures to control the disease spread in Argentina.

First Detection of Madariaga virus in Mosquitoes Collected in a Wild Environment of Northeastern Argentina.

Madariaga virus (MADV), previously known as South American eastern equine encephalitis virus (SA EEEV; family Togaviridae, genus Alphavirus), is a mosquito-borne virus associated mainly with equine disease. In 2010, the first human outbreak by MADV was reported in Central America, but the mosquito vectors and vertebrate hosts involved in the outbreak were not identified. In Argentina, the first epizootic of MADV was in 1930, and since then, several epizootics by MADV have been reported. However, the potential vectors and hosts involved in the transmission cycle remain unknown. In the present study, MADV was detected in Culex (Culex) spp. mosquitoes and the phylogenetic analysis showed that the MADV fragment amplified grouped with the lineage/subtype III of the SA EEEV complex. Our results provide information about the natural infection with MADV in mosquitoes collected in a wild environment of Argentina and its genetic relatedness.

Flavivirus en Chaco / Flavivirus in Chaco

INTRODUCCIÓN Los Flavivirus (Flaviviridae), St. Louis encephalitis (VESL) y West Nile (VWN), son considerados generalistas, ya que en sus ciclos intervienen varios posibles hospedadores vertebrados y mosquitos vectores (Diaz et al. 2013). Estudios previos de nuestro grupo, realizados en la provincia del Chaco (2012-2013), detectaron Flavivirus en varias especies de mosquitos; Psorophora spp., Haemagogus spegazzini, Culex bidens, Culex spp., Hg. spegazzini, Oc stigmaticus, Oc. scapularis, Ps. cyanescens y Mansonia spp. y anticuerpos totales para estos virus en equinos y aves domésticas lo que coincide con un patrón de ciclo establecido por otros autores. Los primeros antecedentes de epizootias de VWN en Argentina son de 2006, cuando 3 caballos murieron de encefalitis en la provincia de Buenos Aires (Morales et al. 2006). Estos datos aportan al conocimiento de la actividad de estos virus en la provincia del Chaco y confirman la presencia de arbovirus en la región desde 1985 al presente. En el presente estudio se detectaron Flavivirus por técnicas moleculares en mosquitos y AcNT totales en hospedadores equinos y humanos de la Provincia del Chaco. OBJETIVOS Contribuir al conocimiento de aspectos epidemiológicos de Flavivirus en la provincia del Chaco. MÉTODOS Se procesaron pooles de mosquitos, homogeneizados y centrifugados a 13.300rpm. El ARN viral se obtuvo a partir del sobrenadante de cada pool mediante métodos comerciales (Roche). RESULTADOS De 191 Pooles de mosquitos conformados, 37 resultaron positivos para Flavivirus spp. En el caso de los equinos, de 133 muestras de sueros procesadas, 78 resultaron positivos (58,6%) para VSLE y 43 (32,3 %) para VWN; por último la prevalencia obtenida de un total de 125 muestras de suero humano fue de 40% para VSLE y 4,8% para VWN. DISCUSIÓN Los datos indican la presencia y circulación de estos agentes virales en la provincia del Chaco, durante el periodo estudiado; sumados a otros hallazgos del grupo de investigación y de otros investigadores del país, sugieren endemicidad de estos arbovirus en la región ya que los factores ambientales, aunque no profundizados en el marco de este estudio en particular, son propicios para el mantenimiento de los ciclos de transmisión entre vectores y hospedadores tanto en zonas rurales como urbanas. Es necesario instalar procesos de vigilancia epidemiológica y clínica por parte de las autoridades sanitarias para una detección temprana de posibles casos de las enfermedades que estos Flavivirus ocasionan y el monitoreo entomológico para la detección de sus posibles vectores desconocidos aún en la región

Venezuelan equine encephalitis viruses (VEEV) in Argentina: serological evidence of human infection.

Venezuelan equine encephalitis viruses (VEEV) are responsible for human diseases in the Americas, producing severe or mild illness with symptoms indistinguishable from dengue and other arboviral diseases. For this reason, many cases remain without certain diagnosis. Seroprevalence studies for VEEV subtypes IAB, ID, IF (Mosso das Pedras virus; MDPV), IV (Pixuna virus; PIXV) and VI (Rio Negro virus; RNV) were conducted in persons from Northern provinces of Argentina: Salta, Chaco and Corrientes, using plaque reduction neutralization test (PRNT). RNV was detected in all studied provinces. Chaco presented the highest prevalence of this virus (14.1%). Antibodies against VEEV IAB and -for the first time- against MDPV and PIXV were also detected in Chaco province. In Corrientes, seroprevalence against RNV was 1.3% in the pediatric population, indicating recent infections. In Salta, this was the first investigation of VEEV members, and antibodies against RNV and PIXV were detected. These results provide evidence of circulation of many VEE viruses in Northern Argentina, showing that surveillance of these infectious agents should be intensified.

New records of mosquito species in the provinces of Chaco and Formosa, Argentina.

Seven mosquito species are recorded for the 1st time for northeastern Argentina: Culex (Melanoconion) albinensis, Cx. (Mel.) elevator, Cx. (Mel.) intrincatus, and Cx. (Mel.) serratimarge for Formosa Province, and Sabethes (Peytonulus) undosus, Sa. (Sabethinus) melanoninphe, and Toxorhynchites (Lynchiella) theobaldi for Chaco Province. The geographical distribution of these species is extended to northeastern Argentina, and the number of species increases to 97 and 75 for the provinces of Chaco and Formosa, respectively.

[Seasonal fluctuation of Aedes aegypti in Chaco Province, Argentina]. / Fluctuación estacional de Aedes aegypti en Chaco, Argentina.

OBJECTIVE: To study the seasonal fluctuation of Aedes aegypti and to correlate its abundance with climate conditions. METHODS: Samples were weekly collected in ovitraps in the city of Resistencia, Chaco Province, Argentina, between October 2002 and November 2003. The number of eggs collected was correlated with temperature, relative humidity, evaporation and rainfalls recorded. Pearson's correlation test with the respective weekly climate data was used in single and multiple correlation analyses. RESULTS: The first record of eggs took place in the last week of October 2002 and continued irregularly up to the last week of June 2003, when no more eggs were seen until November 2003. The highest peak of abundance (70%) was observed in November-December 2002, which coincided with the season of high temperatures and rainfalls. A second less important peak was seen in April coinciding with autumn rainfalls. Significant correlations were found only for monthly accumulated rainfall (r=0.57; p<0.05). No ovipositions were recorded during the winter when temperature dropped below 16.5 degrees C. CONCLUSIONS: The results show a correlation between oviposition and rainfall, as the periods of high activity of Aedes aegypti were in the end of spring-beginning of summer, and beginning of fall. These are periods of major epidemiological risk if an infected person gets to Resistencia.

Fluctuación estacional de Aedes aegypti en Chaco, Argentina / Seasonal fluctuation of Aedes aegypti in Chaco Province, Argentina

OBJETIVO: Estudiar la fluctuación estacional de Aedes aegypti y correlacionar su abundancia con factores ambientales. MÉTODOS: Las colectas fueron realizadas entre octubre de 2002 y noviembre de 2003, en la ciudad de Resistencia, província del Chaco, Argentina. Fueron hechos muestreos semanales empleando ovitrampas. El número de huevos colectados fue correlacionado con la temperatura, humedad relativa ambiente, evaporación y precipitaciones registradas en dicha localidad. Se utilizó el test de correlación de Pearson con los respectivos datos climáticos semanales, realizándose correlaciones simples y múltiples. RESULTADOS: La ocurrencia de huevos fue registrada de manera discontinua, desde la última semana de octubre de 2002, hasta la última de junio de 2003, a partir de la cual no fueron encontrados hasta noviembre de 2003. Se observó un pico de abundancia (70 por ciento) en noviembre y diciembre, que coincidió con el período de temperaturas altas y mayores precipitaciones. Otro pico, aunque de menor importancia, fue observado en abril y coincidió con las lluvias de otoño. Las correlaciones fueron significativas solamente para las precipitaciones acumuladas mensuales (r=0,57; P<0,05). No se registraron oviposturas en invierno cuando la temperatura media semanal fue inferior a 16,5ºC. CONCLUSIONES: Los resultados muestran correlación entre la oviposición y las precipitaciones, pues los períodos de mayor actividad de Aedes aegypti ocurrieron en el final de la primavera, comienzos del verano y en el inicio del otoño. Estos serían los períodos de mayor riesgo epidemiológico especialmente ante la aparición de personas infectadas.

[Main breeding-containers for Aedes aegypti and associated culicids, Argentina]. / Principales criadero para Aedes aegypti y culícidos asociados, Argentina.

Breeding containers for Aedes (Stegomyia) aegypti were identified in two cities of Chaco Province (northeast Argentina): Presidencia Roque Saenz Peña and Machagai. All water-retaining recipients found in house backyards capable to retain water were classified according to their type and size, counted and checked. Aedes aegypti and Culex quinquefasciatus were the most frequently collected species, being also found Cx. maxi, Cx. saltanensis and Ochlerotatus scapularis. Tires and car batteries represented the most important type of container where immature forms of culicids could be found. Rain was an important factor for Ae. aegypti proliferation, as well as the widespread habit of the population of keeping useless containers at home, which allows the development of culicids.

Principales criaderos para Aedes aegypti y culícidos asociados, Argentina / Main breeding-containers for Aedes aegypti and associated culicids, Argentina

Se identificaron criaderos de Aedes (Stegomyia) aegypti en dos ciudades de la provincia del Chaco (Noreste de Argentina): Presidencia Roque Saenz Peña y Machagai. Los recipientes encontrados en los patios de las viviendas capaces de colectar agua se clasificaron según tipo y tamaño, se contaron y examinaron. Aedes aegypti y Culex quinquefasciatus fueron las especies mas abundantes, encontrándose además Cx. maxi, Cx. saltanensis y Ochlerotatus scapularis. Los neumáticos y cajas de baterías para autos fueron los recipientes que más aportaron a la producción de formas inmaduras de los culícidos colectados. Las lluvias fueron un factor importante para la proliferacion de Ae. aegypti, así como también el habito comun en la población de guardar recipientes en sus casas que permitan el desarrollo de estos culícidos