Abstract:The geographic distribution of Aedes (Stegomyia) aegypti (L.) in South America has been expanding during the last decades. Herein we present two new distribution records that extend its southern limits towards localities with extremer environmental conditions than reported to date. San Antonio Oeste constitutes the southernmost finding for the continent (40º44'S), whereas Tandil is the infested locality with the coldest mean annual temperature in Argentina (14.17ºC). The projection of a previous distribution m… Show more
“…In recent decades, aided by global warming, urbanization, trade and human migration, Ae. aegypti has invaded many temperate areas of the world [ 1 , 2 ], reaching latitudes as south as 40° S [ 3 ]. This mosquito species is highly anthropophilic and it is fully adapted to thrive in urban areas, where it can fulfill all its ecological needs.…”
Aedes aegypti, the mosquito species transmitting dengue, zika, chikungunya and yellow fever viruses, is fully adapted to thrive in urban areas. The temporal activity of this mosquito, however, varies within urban areas which might imply different transmission risk. In this work, we hypothesize that temporal differences in mosquito activity patterns are determined by local environmental conditions. Hence, we explore the existence of groups of temporal patterns in weekly time series of Ae. aegypti ovitraps records (2017–2019) by means of time series clustering. Next, with the aim of predicting risk in places with no mosquito field data, we use machine learning classification tools to assess the association of temporal patterns with environmental variables derived from satellite imagery and predict temporal patterns over the city area to finally test the relationship with dengue incidence. We found three groups of temporal patterns that showed association with land cover diversity, variability in vegetation and humidity and, heterogeneity measured by texture indices estimated over buffer areas surrounding ovitraps. Dengue incidence on a neighborhood basis showed a weak but positive association with the percentage of pixels belonging to only one of the temporal patterns detected. The understanding of the spatial distribution of temporal patterns and their environmental determinants might then become highly relevant to guide the allocation of prevention and potential interventions. Further investigation is still needed though to incorporate other determinants not considered here.
“…In recent decades, aided by global warming, urbanization, trade and human migration, Ae. aegypti has invaded many temperate areas of the world [ 1 , 2 ], reaching latitudes as south as 40° S [ 3 ]. This mosquito species is highly anthropophilic and it is fully adapted to thrive in urban areas, where it can fulfill all its ecological needs.…”
Aedes aegypti, the mosquito species transmitting dengue, zika, chikungunya and yellow fever viruses, is fully adapted to thrive in urban areas. The temporal activity of this mosquito, however, varies within urban areas which might imply different transmission risk. In this work, we hypothesize that temporal differences in mosquito activity patterns are determined by local environmental conditions. Hence, we explore the existence of groups of temporal patterns in weekly time series of Ae. aegypti ovitraps records (2017–2019) by means of time series clustering. Next, with the aim of predicting risk in places with no mosquito field data, we use machine learning classification tools to assess the association of temporal patterns with environmental variables derived from satellite imagery and predict temporal patterns over the city area to finally test the relationship with dengue incidence. We found three groups of temporal patterns that showed association with land cover diversity, variability in vegetation and humidity and, heterogeneity measured by texture indices estimated over buffer areas surrounding ovitraps. Dengue incidence on a neighborhood basis showed a weak but positive association with the percentage of pixels belonging to only one of the temporal patterns detected. The understanding of the spatial distribution of temporal patterns and their environmental determinants might then become highly relevant to guide the allocation of prevention and potential interventions. Further investigation is still needed though to incorporate other determinants not considered here.
“…Minimum temperatures were found to act as barriers, which impede DENV to spread into new regions (Butterworth et al 2017; Lee et al 2021). In addition, Díaz-Nieto et al (2013) and Rubio et al (2020) described the new distribution records for Ae. aegypti in southern south América.…”
Section: Discussionmentioning
confidence: 99%
“…Records show that in 1986 the vector was found in only two provinces in the north of the country above 28° S latitude (Díaz-Nieto et al 2013). Currently, there are records of the species up to 40° S latitude (Rubio et al 2020) in 20 of the country’s 24 provinces. Climate conditions, especially temperature, influence the global spread of the vector, the species’ life history characteristics, and the acceleration of the virus transmission capacity (Boggs et al 2012; Bhatt et al 2013; Carrington et al 2013; Kraemer et al 2015; Caldwell et al 2021).…”
BACKGROUND: One of the most important consequences of climate change is the increased spread of dengue from tropical and subtropical regions to temperate areas around the world. Climate variables such as temperature and precipitation influence the dengue vectors biology, physiology, abundance, and life cycle. Thus, an analysis is needed of climate changes and their possible links with the growing occurrence of epidemics recorded in recent decades.
OBJECTIVES: To assess the increasing incidence of dengue driven by climate change at the southern limits of dengue virus transmission in South America.
METHODS: We analyze the evolution of climate, epidemiological, and biological variables, comparing a period without the presence of dengue cases to a more recent period with the occurrence of cases and, consequently, of important epidemics. Temperature and precipitation are the climate variables evaluated, the total number of cases and incidence of dengue are the epidemiological variables, and finally, the optimal temperature ranges for transmission of the dengue vector is the biological variable.
RESULTS: The presence of dengue cases and epidemic outbreaks are observed to be consistent with positive temperature trends and anomalies. Dengue cases do not seem to be associated with precipitation trends and anomalies. The number of days with optimal temperatures for dengue transmission increased from the period without dengue cases to the period with the presence of dengue cases. However, the number of months with optimal transmission temperatures was the same in both periods.
CONCLUSIONS: The higher incidence of dengue virus (DENV) and its expansion to different regions of Argentina seem to be associated with temperature increases in the country during the past decades. The active surveillance of both the vector and associated arboviruses will make it possible to assess and predict the occurrence of epidemics, based on the accelerated changes in climate. Such surveillance should go hand in hand with efforts to improve the understanding of the mechanisms driving the geographic expansion of dengue and other arboviruses beyond the current limits.
“…aegypti has expanded towards colder climate areas (fig. 1), including the provinces of Buenos Aires (Zanotti et al ., 2015), La Pampa (Rossi et al ., 2006; Diez et al ., 2014), Mendoza (Domínguez and Lagos, 2001), Neuquén (Grech et al ., 2013), San Luis (Visintin et al ., 2009), San Juan (Carrizo Páez et al ., 2016) and Río Negro (Rubio et al ., 2020). Figure 1.Location of the localities from which the Ae.…”
Section: Introductionmentioning
confidence: 99%
“…Within Buenos Aires province, the distribution has expanded to the south, currently covering localities such as Azul (Carbajo et al ., 2019), Tandil (Rubio et al ., 2020), Dolores and various cities on the Atlantic coast, including San Bernardo and Villa Gesell (Zanotti et al ., 2015). In several of the recently colonized localities, average winter temperatures (June–August) are lower than 9.5°C, and the period of monthly average temperatures below 12°C extends for 4–5 months.…”
In Argentina, the mosquito Aedes aegypti (L.) (Diptera: Culicidae) is distributed from subtropical to temperate climates. Here, we hypothesized that the expansion of Ae. aegypti into colder regions is favoured by high-phenotypic plasticity and an adaptive inhibition of egg hatching at low temperatures. Thus, we investigated the hatching response of eggs of three populations: one from a subtropical region (Resistencia) and two from temperate regions (Buenos Aires City and San Bernardo) of Argentina. Eggs collected in the field were raised in three experimental colonies. F1 eggs were acclimated for 7 days prior to immersion at 7.6 or 22°C (control eggs). Five immersion temperatures were tested: 7.6, 10.3, 11.8, 14.1 and 16°C (range of mean winter temperatures of the three localities). A second immersion at 22°C was performed 2 weeks later to assess the inhibition to hatch under favourable conditions. After the first immersion, we compared the proportions of hatched eggs and dead larvae among treatment levels, whereas after the second immersion we compared the hatching response among the three populations. The factors that most influenced the egg hatching response were the geographical origin of the populations and the immersion temperature, but not the acclimation temperature. The proportions of hatching and larval mortality at low temperatures were higher for Resistencia than for Buenos Aires and San Bernardo, whereas the hatching response at ambient temperature was lower for San Bernardo than for Buenos Aires and Resistencia. The results support the hypothesis that populations from colder regions show an adaptive inhibition of egg hatching.
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