Introducction

The Asian tiger mosquito, Aedes albopictus (Skuse, 1894), is an invasive species native is s an invasive exotic species with a strong genetic, physiological and ecological plasticity¹. This species is attributed characteristics and adaptive advantages over the other species, which make it a successful invader. One of its characteristics is that its eggs resists more or less to dry conditions, which allows them to survive in inhospitable environments, in addition to facilitating its transport by humans. Perhaps its greatest importance is its association with man, because the alterations caused by humans open new habitats, what benefits them, because they have characteristics of invasive species.

Ae. Albopictus has colonized all continents except Antarctica during the last 30-40 years³. It was first found in the continental U.S. in August, 1985, in Houston, Texas⁴, and is currently found in 866 counties in 26 states, and was recently reported in Southern California^5,6.

The first records of Ae. albopictus in Mexico were conducted in the state of Tamaulipas 1988⁷, Coahuila in 1994^8,9, later in 1994^8,9 the first infested states in the Gulf of Mexico Veracruz¹⁰, and Nuevo León 2001¹¹. In September 2003, larvae samples in Tapachula, Chiapas¹². The species was reported in the southern center of the countiy in Morelos¹³. In 2012, the presence of the species was confirmed in Cancún, Quintana Roo¹⁴. Currently, Ae. albopictus is registered in 12 states of Mexico (Chiapas, Coahuila, Hidalgo, Morelos, Nuevo León, Oaxaca, Puebla, Querétaro, Quintana Roo, San Luis Potosí, Tamaulipas and Veracruz)¹⁵. Recently the first record of Ae. albopictus in Tabasco reported in June 2018 in the Municipalities of Huimanguillo, Teapa, Tacotalpa and Villahermosa¹⁶.

The epidemiological importance of Ae. albopictus is that it can transmit, experimentally or naturally, at least 22 arboviruses, most of these are of importance in human health¹⁷. Among these, the transmission of the four dengue serotypes and eastern equine encephalitis viruses and Japanese, as well as the Zika, Chikungunya and West Nile virus are of particular interest. In addition, it has been documented that it can transmit the Yellow Fever virus, which constitutes it as a vector between the sylvatic and urban transmission cycles. Additionally, in endemic areas for dengue, in which cases of Yellow Fever occur, there is a potential risk that this disease will be urbanized¹⁸.

For some viruses such as Dengue, Yellow Fever, Potosí and La Crosse, it has been experimentally demonstrated that Ae. albopictus can transmit them via transovarial to their offspring. In particular, in the transovarial transmission of the Dengue virus it has been found that it can transfer the four serotypes in a more efficient way than the one exhibited by Ae. aegypti^19,20. Therefore, the objective of this work was to determine the presence and distribution of Ae. albopictus in Tabasco, Mexico in the period of January 2015- July 2018.

Material and methods

A transversal observational descriptive study with a quantitative component was carried out. From January 2015 to July 2018, a total of 4090 samples of Aedes sp. mosquito larvae were sent to the state public health laboratory for taxonomic identification. Each one from the 17 municipalities of Tabasco with 38 priority locations that included the municipal capitals and the main towns, which were collected from the state monitoring system of entomological surveillance using ovitraps (n = 6929), installed in the state.

The biological material collected from the ovitraps was selected according to a schedule ordered by municipality and locality, then in order to hat eggs, they were immersed in dechlorinated water at an average temperature of 27 ° C, 10 pellones in trays of 5L of volumetric capacity, from 1 to 3 days the larvae hatched to have a size of 2nd instar. They were placed in pooles of 50 larvae which tropical fish flakes of the brand BIOMAA® were added as food with the following content mínimum Protein 42.0%, mínimum Fat 5.0%, maximum Fiber 6.0%, maximum Ash 6.0%, maximum Humidity 8.0% and they were bred until the 4th instar for taxonomic identification in an average of 6 days. Methodology used for the immature stages was the guide for breeding and maintenance of colonies of Aedes sp. (DIPTERA: CULICIDAE :) under insectary conditions, in the entomological research unit²¹, samples were sent under the normative criteria of the state public health laboratory in 10 ml test tubes and preserved in 70% alcohol, for its taxonomic identification, a “HUND WETZALAR” optical microscope with 10-40X achromatic objective ranges was used, following the dichotomous keys for the taxonomic identification following the dichotomous keys for taxonomic identification of common mosquito larvae in urban and suburban areas of the Mexican republic²².

Results

The distribution of Ae. albopictus in the state of Tabasco, was identified in 17 localities (44.74%) of 9 municipalities representing 52.94% and at risk (figure 1). Of 4090 samples processed, 3882 (94.91%) correspond to Ae. aegypti and 208 (5.08%) to Ae. albopictus. In the municipality of Huimanguillo, it was detected in 4 localities (1.25%) followed by Cárdenas with 3 localities (1.15%) and Tacotalpa with 2 localities (1.37%). Table 1 shows the detection of Ae. albopictus in chronological order.

Source: Own elaboration based on the Entomological Research Unit of Tabasco.

Figure 1. Distribution of Aedes albopictus in the state of Tabasco, Mexico, 2015-2018, from entomological surveillance with ovitraps. 

Table 2 shows the samples collected and sent from the 17 municipalities and 38 localities with entomological surveillance with ovitraps in the period January 2015- July 2018.

Discussion

The present study shows the rapid dispersion and adaptation of Aedes albopictus, an invasive exotic species in the state of Tabasco. In a span of 3 years, it has been possible to establish in 52.94% of the municipalities that are part of the state and its arrival in the state is not surprising due to favorable factors for its reproduction; as the warm humid climate with abundant precipitation and prevalence of aquatic vegetation, as well as the proximity to the state of Chiapas¹², place where the vector is already present.

Aedes albopictus is a species native to the jungle that has been adapted to the urban environment, their preferential breeding places are the natural ones with extensive vegetation and humidity, which has taken advantage of the bamboo stumps, armpits of plants (bromeliads) and in hollows of trees and stones²³. When this species enters the urban environment, it can easily inhabit artificial deposits such as pots, vases, tires and cans²⁴.

The results are consistent with recently published by Ortega- Morales et al¹⁶ and includes the municipalities of Cardenas, Comalcalco, Cunduacán, Jalpa and Paraiso, where the species is already present, providing valuable information for prevention and control of arboviruses in the state of Tabasco.

Both species reported in this entomological surveillance, are considered important vectors and also as invasive species, because they have successfully colonized many places outside of their native environment²⁵.

Of the 4,090 identifications, Ae. aegypti was the species found in 94.7% of localities sampled and with a higher proportion (94.91%) compared to Ae. albopictus (5.09%). When both Aedes species share the same breeding sites, there is no scientific consensus about the displacement of one species with respect to the other. While studies conducted in Southeast Asia indicate that Ae. Aegypti can replace Ae. albopictus in urban areas. In the United States and Brazil, it has been observed that this species with more jungle characteristics, can reach drastically and quickly populations of Ae. Aegypti¹⁷. Since, a series of ecological principles states that two species cannot occupy the same niche, which leads to a reduction in the population of one of the species due to competition with the other²⁵.

Conclusion

The presence and distribution of Ae. Albopictus was destermined in 9 municipalities of Tabasco, so it is recommended to strengthen the entomological surveillance of the species, in order to generate information regarding densities in immature and imago states. Because Ae. albopictus is conferred anthropophilic and zoophilic capacity as a potential vector to intervene in the transmission cycles both of anthropozoonotic diseases and exclusive occurrence of human being and with an endemic or emergent behavior²⁶. The dispersion of Ae. albopictus in Tabasco is still in progress as it could colonize the 17 municipalities of the state. This poses new challenges in public health, in terms of the prevention and control of arboviruses and it requires us to generate knowledge in order to implement strategies considering the particularities of the species present.