(Asian) tiger mosquito

Type Description

Aedes albopictus, also known as the 'Asian tiger mosquito,' is a vector mosquito species native to the Asian continent, distinguished by its black and white pattern (Yılmaz, 2019). It ranges in size from 2 to 10 mm (Doğan, 2015). Females of this species are typically larger than males and have more receptors on their antennae. They can be distinguished from other Aedes species by the long white stripes on their scutum. This species is highly aggressive and actively feeds on potential hosts at all times of the day (Huang, 1968; Doğan, 2015). Species belonging to this genus have a rapid reproduction and dispersal ability, and are resilient to drought, cold, and prolonged starvation. They exhibit low host selectivity and are medically important for humans and animals due to their ability to vector many arboviruses (Doğan, 2015).

Habitat

Aedes albopictus is a mosquito species that primarily lays eggs in water collected in tree holes and is more commonly found in areas with dense vegetation. However, due to its ecological flexibility, it can also breed in urban areas close to humans (e.g., in pots, car tires, open water collection containers, sewage pits, water tanks, etc.). Organic matter such as fallen leaves and tree branches in these urban breeding sites create an ideal environment for larval development (Hawley, 1988). While it can be active year-round in warm and humid tropical regions, in temperate areas, it can spend the winter months in adult diapause. It has been reported that the eggs of populations settled in temperate regions are more resistant to cold than those of mosquitoes in tropical regions (Hawley, 1989; Doğan, 2015). Although the natural habitat of this species is South Asia and the surrounding Pacific islands, it has been observed to spread to all continents except Antarctica in the last 50 years. Its high adaptability to climate conditions and harsh weather has allowed it to spread invasively thousands of kilometers away from its native range, forming established populations (Doğan, 2015; Arat, 2019). First observed in Albania in Europe, A. albopictus has since spread to countries such as Brazil, Mexico, the United States, Belgium, France, and Italy. Most recently, its population was detected in Turkey in 2011, and by 2015, it was found to have established resident populations (Akıner et al., 2016). It poses a serious public health problem in regions where it rapidly spreads in Europe (Doğan, 2015). In Turkey, it has been observed to spread from the western regions, including Istanbul and Thrace, to the eastern Black Sea region, reaching as far as Giresun. It is predicted to spread to Central Anatolia within 5-7 years, reaching from Kocaeli in the west to Giresun in the east (Arat, 2019).

Reproductive Information

A female mosquito, after feeding on blood, mates and then seeks a suitable place to rest for about 2-3 days while digesting the blood. Afterward, she begins searching for potential places to lay her eggs, which are usually areas prone to water accumulation, such as rainwater or flooded areas. Depending on the water temperature, larvae typically hatch within about two days. Once hatched, the larvae molt three times and go through four stages before reaching adulthood (Becker et al., 2003). Female Aedes albopictus mosquitoes prefer to lay their eggs in places such as flowerpots, discarded tires, puddles, water tanks, and sewer pits (Aranda et al., 2006; Benedict et al., 2007; Doğan, 2015).

Lifecycle

The life cycle of Aedes mosquitoes consists of four stages: egg, larva, pupa, and adult. Unlike Culex and Culiseta mosquitoes, Aedes mosquitoes lay their eggs individually rather than in groups. Similarly, they lay their eggs not directly on the water but on surfaces near water that may later become flooded (Alten and Çağlar, 1998). This behavior has led to the eggs evolving to be resistant to drought. This species can adapt to almost any environment and can lay its eggs in many natural and artificial habitats. Common egg-laying sites for this species include tree holes, cut bamboo, plastic containers that can collect water, flowerpots, discarded tires, open water collection containers, sewer pits, water tanks, and more (Yılmaz, 2019). The larvae hatch from the eggs when they are flooded with water and feed on organic matter in the water, going through four larval stages (Hawley, 1988). The speed of transition between these stages is greatly influenced by the amount of food present in the environment and the ambient temperature (Aranda et al., 2006). The pupal stage is a resting stage during which Aedes species do not feed. Aedes mosquitoes typically become adults within 4-6 days, depending on the temperature. The adult stage is the most important stage for this species as it is when they are vectors of diseases and engage in biting activity. Adult Aedes mosquitoes feed on plant juices for carbohydrates and require protein for egg production. They obtain this protein by feeding on various hosts. Aedes albopictus feeds on both humans and animals. While their feeding activity is generally more active at dawn and dusk, they can feed at any time of the day. Sometimes, when entering forested areas, they attack people entering these areas, potentially transmitting diseases from their forest hosts to humans. Because of this behavior, they are also known as the "forest mosquito" (Hawley, 1988; Yılmaz, 2019). While they can be active year-round in warm and humid regions, they spend the winter as eggs in temperate regions (Alten and Çağlar, 1998).

Nutrition Information

Only female mosquitoes need to feed on blood for the development of their eggs, while they can also feed on nectar and other sugary plant fluids for carbohydrate sources, similar to male mosquitoes. Females locate their hosts using carbon dioxide, organic compounds, moisture, and their own optical receptors. Because they feed during the day in forests, they are also known as "forest mosquitoes." Depending on their habitat, they are active at different times of the day, but usually in the twilight zones. Aedes albopictus can feed on the blood of mammals and birds other than humans (Hawley, 1988; Doğan, 2015).

General Impact Information

"Aedes albopictus feeds on both humans and animals. Although its feeding behavior usually increases at twilight, it can occur at any time of the day. Sometimes, when entering forested areas, it attacks people entering these areas. This attack also causes the mosquito to transmit diseases from its forest hosts to humans. Because of this characteristic, it is also known as the ""forest mosquito"" (Hawley, 1988). Aedes albopictus has a very rapid reproduction and dispersal ability, and it is a species with high adaptability even in unsuitable climatic conditions. It is known to vector various disease pathogens. It is the primary and secondary vector of viral diseases such as Chikungunya, Dengue fever, Yellow Fever, and Zika Virus. Additionally, a study in 2010 revealed that it is a possible vector of the Usutu Virus. Cases of diseases vectored by this species are observed every year in many parts of the world. Furthermore, it has been reported to vector Dirofilaria immitis. Aedes albopictus differs from other vector species in that it can move from one host to another before completing its blood meal, which is an important factor in the transmission of pathogens and the spread of diseases (Gratz, 2004; Calzolari et al., 2010; Doğan, 2015).
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General Management Information

Cultural Control Method- For the vector control of integrated control, it is crucial that the personnel responsible for vector control have sufficient knowledge and that community support is obtained. Especially health and municipal workers, teachers, and students should be informed about vector-borne diseases and prevention methods. Training sessions and seminars should be organized, and informative posters and brochures should be designed and distributed to educate the public. Public service announcements should be made on radio/television and the internet to increase the community's knowledge and awareness of the issue (Alten and Çağlar, 1998; Ser and Çetin, 2016; Arat, 2019).Mechanical Control- The aim of this control method is to eliminate the habitats of mosquitoes. This method is implemented by destroying the larval habitats and breeding areas. For this purpose, wastewater accumulations near human habitats should be closed, and areas with water accumulations or potential water accumulation should be eliminated (Özcel and Daldal, 1997; Yılmaz, 2019).The best control measure that can be taken against adult mosquitoes is to arrange their resting areas. Especially, arranging the areas used by mosquitoes for hibernation is effective both in reducing the population level for the next year and in eliminating the diseases carried by mosquitoes (Yılmaz, 2019). To prevent mosquitoes from entering their habitats, areas such as doors and windows can be screened, and beds can be covered with mosquito nets to prevent mosquitoes from biting humans while sleeping. Additionally, wearing clothing that covers the body can minimize mosquito bites. Considering that mosquitoes can also feed through clothing due to their proboscis structure, spraying repellents on clothing can significantly prevent mosquito bites. Moreover, not staying outdoors in the evening helps prevent mosquito bites, especially from species like Aedes that prefer to feed in twilight or dark environments (Özcel and Daldal, 1997; Alten and Çağlar, 1998; Yılmaz, 2019).Biological Control- The main goal of biological control is to reduce the mosquito population using the natural enemies of the species. Living organisms that prey on mosquitoes, kill them with chemicals they release, repel them, or make them sick are used in this method (Demirtaş, 2017). Among the vertebrates used in mosquito control are fish, birds, and mammals such as bats. Among the invertebrates, hydras, flatworms, freshwater snails, leeches, spiders, and mites, crustaceans, and various insect groups are used. In addition, nematodes, bacteria, protozoans, fungi, and viruses that are pathogens of mosquitoes are also used (Becker et al., 2010). With the increase in malaria cases in our country towards the end of the 20th century, different methods have been sought for mosquito control. The mosquito fish (Gambusia affinis), which is compatible with the habitats of mosquito larvae and feeds on mosquito larvae, was brought to our country as a solution to this problem and released into various lakes and rivers. This fish species, which has high adaptability and wide ecological tolerance, can still be encountered in rivers in our country after years have passed (Aktürk, 2009). Bacteria have come to the rescue of humans in mosquito control, as in many other areas. After it was discovered in 1975 that cryotoxins obtained from the bacterium Bacillus thuringiensis var. israelensis were effective on mosquito larvae, mosquito control took on a different dimension. With the increase in studies related to the subject in subsequent years, it was found that other Bacillus species could also be used in control, and it was revealed that Bacillus sphaericus was effective in mosquito control (DeBarjac et al., 2012). Similarly, spinosad, isolated from Saccharopolyspora spinosa, and its synthetic derivatives, known as spinosin, have also taken their place in mosquito control (Romi et al., 2006). Plants are also used in mosquito control. It was discovered during this period that extracts obtained from plants have insecticidal effects. The neem tree (Azadiracta indica) is the most important plant known to have insecticidal activity (Yılmaz, 2019). Genetic Control- With the better recognition of living organisms, new methods have begun to be discovered for combating them. Essentially based on the release of sterile individuals raised in laboratory conditions into nature, genetic control dates back to the 1960s and 1970s. This method is based on rendering male individuals sterile by applying radiation or various chemicals and releasing them into nature (Özcel and Daldal, 1997; Doğan, 2015). Although this method is theoretically based on a logical foundation, it was limited to mosquito control when first developed. The main reason for this is that individuals raised under laboratory conditions have difficulty adapting to life in nature (Özcel and Daldal, 1997). With the increase in vector-borne diseases in recent years, studies on the method have been revisited (Yılmaz, 2019). Another method based on genetic control is the use of Wolbachia isolates that cause infertility in mosquitoes. This method involves rearing Wolbachia isolates in laboratory conditions and releasing them into nature (Werren et al., 2008). Chemical Control- Since ancient times, the most widely used method in combat has been chemical warfare. In relation to chemical warfare, sulfur was used by the ancient Greeks, arsenic was used in China, and in Roman times, the plant 'Hellebore' was used to combat human lice (Kılıç, 2015). In 1892, the first synthetic insecticide, Dinitro-O-Cresol (DNOC), was discovered and began to be used in insect groups. The discovery of DDT in 1939 was a milestone for insecticide use. It was used for many years, especially in the control of the malaria vector Anopheles and the typhus-causing louse and flea, but it was banned due to the resistance it caused (Berg et al., 2012). With the advancement of technology and the progress of chemistry, new insecticides and groups of insecticides have been discovered. The use of insecticides for mosquito control has been a process that has continued from ancient times to the present day. However, due to their negative effects on human and animal health and their adverse effects on the environment, the use of chemical-based insecticides has rapidly decreased in the last 10 years (Yılmaz, 2019).

General Pathway Information

"Aedes albopictus, with its aggressive and highly successful invasive nature, its rapidly increasing population size, and relative abundance, has become one of the most important vector mosquito species in the last twenty years. It has spread rapidly from its native tropical and subtropical regions to Europe, North and South America, the Caribbean, and the Middle East. It is now seen as one of the most successful invasive mosquito species in the world (Benedict et al., 2007; Scholte and Schaffner, 2007; Reiter and Sprenger, 1987). Their high phenotypic plasticity allows them to establish large populations in a short time in temperate regions with cold and dry climates. While they can be active year-round in warm and humid tropical regions, in temperate regions, they can spend the winter months in adult diapause. It has been reported that the eggs of lineages settled in temperate regions are more resistant to cold than those of mosquitoes in tropical regions (Hawley et al., 1989). Another key role of Aedes albopictus in the spread of diseases is the different feeding behavior of its females compared to other mosquito species. The vector strengthens its role as a bridge during the transmission of pathogens by moving to other hosts before completing its blood meal in one host (Doğan, 2015). Due to its ability to easily adapt to different environmental conditions, its high adaptability value, its close relationship with humans, and its reproductive rate giving it a greater competitive advantage over other closely or distantly related mosquito species, Aedes albopictus is a mosquito species that is very difficult to control (Doğan, 2015). Its high adaptability allows it to quickly enter new locations. The entry of the species into new locations occurs through non-wooden containers and packaging, household waste, vehicles, plants or plant parts, and ship structures on the waterline.


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Notes

The adult Asian tiger mosquito travels as a stowaway in vehicles and therefore is distributed along major traffic routes.

References