Detección de virus dengue, chikungunya y Zika, y variabilidad genética de larvas Aedes aegypti en Costa Rica
Archivos
Fecha
2023
Autores
Flores Núñez, Sonia Alejandra
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Editor
Universidad Nacional, Costa Rica
Resumen
Estudiar la diversidad de mosquitos en una región permite monitorear la aparición de
especies nuevas, brinda información sobre la composición de una comunidad de
insectos, y ayuda a monitorear la estabilidad de un ecosistema. Esto es importante para
la conservación del medio ambiente y el control de arbovirus, como los virus dengue
(DENV), chikungunya (CHIKV) y Zika (ZIKV), que son transmitidos principalmente por el
mosquito Aedes aegypti ocasionando un gran impacto a la salud pública. La transmisión
horizontal se considera la más importante en periodos de brote, sin embargo, se ha
reportado transmisión vertical que mantiene los virus durante periodos desfavorables,
por lo que es importante implementar medidas de manejo del mosquito vector esto. Para
esto, es indispensable conocer aspectos de la ecología de Ae. aegypti, entre ellos los
patrones de dispersión y propagación, como factores que facilitan la invasión y
adaptación a nuevos entornos. Se cree, que cambios genéticos en el insecto, podrían
facilitar la invasión y adaptación a nuevos entornos, por lo que resulta importante estudiar
la diversidad genética de estos mosquitos. El objetivo del primer trabajo fue estimar la
diversidad de culícidos y detectar la presencia de DENV, CHIKV y ZIKV en larvas Ae.
aegypti, mientras que el objetivo del segundo trabajo fue determinar la diversidad
genética de poblaciones de larvas Ae. aegypti en diferentes localidades de Costa Rica.
Se recolectaron, durante agosto a noviembre de 2021, larvas en 26 localidades de 19
distritos, que históricamente habían reportados casos de DENV, CHIKV y ZIKV (n=22) o
en los que se reportaron brotes durante la recolecta de muestras (n=4). Las larvas se
identificaron a nivel de especie (Aedes y Culex) o género (Limatus). Para cumplir con el
primer objetivo, se calcularon diversos índices de diversidad (riqueza especifica, similitud
de Jaccard, Margalef, Shannon-Weaver y Pielou). Las larvas de Ae. aegypti se
sometieron a análisis molecular para detectar la presencia de DEN, CHIKV y ZIKV. Se
encontraron dos especies de larvas de Aedes (Ae. aegypti, Ae. albopictus), cinco de
Culex (Culex coronator, Culex corniger, Culex quinquefasciatus, Culex nigripalpus y
Culex interrogator) y larvas del género Limatus, determinándose a Ae. aegypti como la
especie predominante en 20 de 26 localidades. El índice de Pielou demostró que el
distrito de Pavones fue el que presentó mayor equitatividad de distribución de las
especies. Los distritos de La Virgen y Guácimo presentaron mayor riqueza especifica y diversidad de especies, encontrándose seis de las ocho especies identificadas. En los
distritos de Jacó, La Suiza y Pital solamente se detectó una especie (Ae. aegypti). Del
total de 74 grupos de larvas de Ae. aegypti analizadas por RT-qPCR, ninguno resultó
positivo para DEN, CHIKV y ZIKV. Se recomienda realizar investigaciones sistemáticas
para determinar índices de diversidad tanto en estación lluviosa como estación seca, de
diferentes localidades, así como seguir recolectando larvas de Ae. aegypti en zonas con
brotes de arbovirosis para demostrar la transmisión vertical.
Para cumplir con el segundo objetivo, una larva por localidad se sometió a extracción de
ADN y análisis molecular (reacción en cadena de polimerasa convencional del gen
mitocondrial del citocromo oxidasa I y secuenciación). Aedes aegypti se encontró en 20
de las 26 localidades y en los 19 distritos muestreados. En total se determinaron tres
haplotipos (H1, H2 y H3). El haplotipo 1 fue el más abundante y el que presentó mayor
distribución, encontrándose en 16 localidades, mientras que los haplotipos 2 y 3 se
encontraron en una y tres localidades, respectivamente. Los tres haplotipos presentaron
15 sitios polimórficos, tres de los sitios polimórficos afectaron la secuencia de los
aminoácidos. El haplotipo 1 y 2 han sido reportados hasta la fecha solo en Centroamérica
y Panamá, mientras que el haplotipo 3 había sido encontrado previamente en Siquirres
y se ha reportado presente en Canadá, Nueva Caledonia y Alemania. Se recomienda
realizar estudios sistemáticos de haplotipos de Ae. aegypti con un mayor número de
muestras a analizar por distrito o localidad, y en diferentes estaciones climáticas, para
determinar el haplotipo más frecuente y establecer si el país muestra alta o baja
diversidad genética de Ae. aegypti.
Studying the diversity of mosquitoes in a region allows monitoring the appearance of new species, provides information on the composition of an insect community, and helps to monitor the stability of an ecosystem. This is important for environmental conservation and the control of arboviruses, such as dengue (DENV), chikungunya (CHIKV) and Zika (ZIKV) viruses, which are transmitted mainly by the Aedes aegypti mosquito, causing a great impact on public health. Horizontal transmission is considered the most important during outbreak periods; however, vertical transmission has been reported to maintain the viruses during unfavorable periods, so it is important to implement mosquito vector management measures. For this, it is essential to know aspects of the ecology of Ae. aegypti, including dispersal and propagation patterns, as factors that facilitate invasion and adaptation to new environments. It is believed that genetic changes in the insect could facilitate invasion and adaptation to new environments, so it is important to study the genetic diversity of these mosquitoes. The objective of the first study was to estimate the diversity of culicidae and detect the presence of DENV, CHIKV and ZIKV in Ae. aegypti larvae, while the objective of the second study was to determine the genetic diversity of Ae. aegypti larval populations in different localities of Costa Rica. Larvae were collected during August to November 2021 from 26 localities in 19 districts, which had historically reported cases of DENV, CHIKV and ZIKV (n=22) or where outbreaks were reported during sample collection (n=4). Larvae were identified to species (Aedes and Culex) or genus (Limatus) level. To meet the first objective, various diversity indices (specific richness, Jaccard, Margalef, Shannon-Weaver and Pielou similarity) were calculated. Ae. aegypti larvae were subjected to molecular analysis to detect the presence of DEN, CHIKV and ZIKV. Two species of Aedes larvae (Ae. aegypti, Ae. albopictus), five species of Culex (Culex coronator, Culex corniger, Culex quinquefasciatus, Culex nigripalpus and Culex interrogator) and larvae of the genus Limatus were found, with Ae. aegypti being determined as the predominant species in 20 of 26 localities. The Pielou index showed that the district of Pavones was the most equitable in terms of species distribution. The districts of La Virgen and Guácimo presented the greatest specific richness and diversity of species, with six of the eight species identified. In the districts of Jacó, La Suiza and Pital, only one species (Ae. aegypti) was detected. Of the total of 74 groups of Ae. aegypti larvae analyzed by RT-qPCR, none tested positive for DEN, CHIKV and ZIKV. Systematic research is recommended to determine diversity indices in both rainy and dry seasons, from different localities, as well as to continue collecting Ae. aegypti larvae in areas with arbovirosis outbreaks to demonstrate vertical transmission. To meet the second objective, one larva per locality was subjected to DNA extraction and molecular analysis (conventional polymerase chain reaction of the mitochondrial cytochrome oxidase I gene and sequencing). Aedes aegypti was found in 20 of the 26 localities and in the 19 districts sampled. A total of three haplotypes (H1, H2 and H3) were determined. Haplotype 1 was the most abundant and the most widely distributed, being found in 16 localities, while haplotypes 2 and 3 were found in one and three localities, respectively. All three haplotypes presented 15 polymorphic sites, three of the polymorphic sites affected the amino acid sequence. Haplotypes 1 and 2 have been reported to date only in Central America and Panama, while haplotype 3 had previously been found in Siquirres and has been reported present in Canada, New Caledonia and Germany. It is recommended that systematic studies of Ae. aegypti haplotypes be carried out with a greater number of samples to be analyzed per district or locality, and in different climatic seasons, to determine the most frequent haplotype and establish whether the country shows high or low genetic diversity of Ae. aegypti.
Studying the diversity of mosquitoes in a region allows monitoring the appearance of new species, provides information on the composition of an insect community, and helps to monitor the stability of an ecosystem. This is important for environmental conservation and the control of arboviruses, such as dengue (DENV), chikungunya (CHIKV) and Zika (ZIKV) viruses, which are transmitted mainly by the Aedes aegypti mosquito, causing a great impact on public health. Horizontal transmission is considered the most important during outbreak periods; however, vertical transmission has been reported to maintain the viruses during unfavorable periods, so it is important to implement mosquito vector management measures. For this, it is essential to know aspects of the ecology of Ae. aegypti, including dispersal and propagation patterns, as factors that facilitate invasion and adaptation to new environments. It is believed that genetic changes in the insect could facilitate invasion and adaptation to new environments, so it is important to study the genetic diversity of these mosquitoes. The objective of the first study was to estimate the diversity of culicidae and detect the presence of DENV, CHIKV and ZIKV in Ae. aegypti larvae, while the objective of the second study was to determine the genetic diversity of Ae. aegypti larval populations in different localities of Costa Rica. Larvae were collected during August to November 2021 from 26 localities in 19 districts, which had historically reported cases of DENV, CHIKV and ZIKV (n=22) or where outbreaks were reported during sample collection (n=4). Larvae were identified to species (Aedes and Culex) or genus (Limatus) level. To meet the first objective, various diversity indices (specific richness, Jaccard, Margalef, Shannon-Weaver and Pielou similarity) were calculated. Ae. aegypti larvae were subjected to molecular analysis to detect the presence of DEN, CHIKV and ZIKV. Two species of Aedes larvae (Ae. aegypti, Ae. albopictus), five species of Culex (Culex coronator, Culex corniger, Culex quinquefasciatus, Culex nigripalpus and Culex interrogator) and larvae of the genus Limatus were found, with Ae. aegypti being determined as the predominant species in 20 of 26 localities. The Pielou index showed that the district of Pavones was the most equitable in terms of species distribution. The districts of La Virgen and Guácimo presented the greatest specific richness and diversity of species, with six of the eight species identified. In the districts of Jacó, La Suiza and Pital, only one species (Ae. aegypti) was detected. Of the total of 74 groups of Ae. aegypti larvae analyzed by RT-qPCR, none tested positive for DEN, CHIKV and ZIKV. Systematic research is recommended to determine diversity indices in both rainy and dry seasons, from different localities, as well as to continue collecting Ae. aegypti larvae in areas with arbovirosis outbreaks to demonstrate vertical transmission. To meet the second objective, one larva per locality was subjected to DNA extraction and molecular analysis (conventional polymerase chain reaction of the mitochondrial cytochrome oxidase I gene and sequencing). Aedes aegypti was found in 20 of the 26 localities and in the 19 districts sampled. A total of three haplotypes (H1, H2 and H3) were determined. Haplotype 1 was the most abundant and the most widely distributed, being found in 16 localities, while haplotypes 2 and 3 were found in one and three localities, respectively. All three haplotypes presented 15 polymorphic sites, three of the polymorphic sites affected the amino acid sequence. Haplotypes 1 and 2 have been reported to date only in Central America and Panama, while haplotype 3 had previously been found in Siquirres and has been reported present in Canada, New Caledonia and Germany. It is recommended that systematic studies of Ae. aegypti haplotypes be carried out with a greater number of samples to be analyzed per district or locality, and in different climatic seasons, to determine the most frequent haplotype and establish whether the country shows high or low genetic diversity of Ae. aegypti.
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Palabras clave
MOSQUITOS, COSTA RICA, DENGUE, AEDES AEGYPTI, SALUD PÚBLICA, PUBLIC HEALTH, LARVAS,