Asian Tiger Mosquitos (Aedes Albopictus) all over the place

Well now it seems they have moved on and we’ve got millions of the horrible black little vermin all over Lanjaron and the Alpujarras. They took huge chunks out of me a few days ago whilst clearing an irrigation channel. Big, black and nasty! Don’t remember getting bitten by them or even seeing them last year. This species has been nominated as among 100 of the “World’s Worst” invaders

Here is some info about them (source:www.invasivespecies.net)

Description Aedes albopictus is known as the Asian tiger mosquito due to the conspicuous black and white stripes on its body. There is also a distinctive single white stripe down the length of the back. The body length is about 4.75mm long. Like all mosquitoes, Asian tiger mosquitoes are small, fragile insects with slender bodies, one pair of narrow wings and three pairs of long, slender legs. They have an elongated proboscis with which the female bites and feeds on blood.

Occurs in: agricultural areas, coastland, natural forests, planted forests, range/grasslands, ruderal/disturbed, scrub/shrublands, urban areas, water courses, wetlands

** Habitat description** Aedes albopictus is a treehole mosquito in natural areas, however in urban areas, the mosquitoes breed around bush vegetation in gardens. Larval habitats are mostly in small containers. Its ecological flexibility allows it to colonise many types of man-made sites and urban regions. It may reproduce in flower pots, bird baths, soda cans and abandoned containers and water receptacles. Tyres are particularly useful for mosquito reproduction, as they are often stored outside and effectively collect and retain rainwater for a long period of time. The addition of decaying leaves from neighbouring trees produces chemical conditions similar to tree holes, which provides an excellent substrate for breeding. A. albopictus can also establish and survive throughout non-urbanised areas lacking any artificial containers, raising additional public health concerns for rural areas (Eritja et al. 2005).

** General impacts** Aedes albopictus is an aggressive outdoor day biter, that attacks humans, livestock, amphibians, reptiles and birds (Eritja et al. 2005). In one survey of biting rates a level of 30 to 48 bites per hour was recorded (Cancrini et al. 2003).

Mosquitoes are vectors of many human diseases, from malaria to filariasis (caused by Dirofilaria immitis) (Eritja et al. 2005). Aedes albopictus may be a matter of particular concern as a bridge vector for the West Nile virus because it inhabits rural areas and has a wide host range, including birds, so that it can readily pass enzootic cycles to humans. There are a total of four Flaviviruses, ten Bunyaviruses and seven Alphaviruses that A. albopictus is known to be receptive to in laboratory conditions. These include yellow fever, rift valley fever, chikungunya and sindbis (all of which are present in the Mediterranean). Of these A. albopictus is known to be receptive in field conditions to three Flaviviruses (dengue, West Nile and Japanese encephalitis), six Bunyaviruses (Jamestown Canyon, Keystone, LaCrosse, Potosi, Cache Valley and Tensaw) and one Alphavirus (EEE). Other circulating viruses in the Mediterranean that are pathogenic to humans (but which the receptivity of A. albopictus has not been observed or tested in the laboratory) include Israel Turkey virus, Tahyna and Batai.

Geographical range _ Native range_: Aedes albopictus occurs throughout the Oriental Region from the tropics of Southeast Asia, the Pacific and Indian Ocean Islands, north through China and Japan and west to Madagascar. _ Known introduced range:__ _The mosquito has been introduced in North and South America, with more recent introductions having occurred in Africa, Australia and Europe, where it is established in Albania, Italy and also France (Eritja et al. 2005). In the United States, it is established in most states east of the Mississippi River as far as Minnesota and Delaware (Source: Novak). In Europe, the patchy distribution is probably more related to specific transport incidents than to the climatic needs of the species (Roger Eritja, pers.comm., 2006); Spain (Aranda et al. 2006); Greece (Samanidou et al. 2005).


Introduction pathways to new locations _ Nursery trade: _Nurseries selling lucky bamboo (Dracaena spp.) in California were found to be infested by Aedes albopictus. The trade in lucky bamboo is increasing as it has cultural relevance within the Asiatic communities in the U.S. and elsewhere and it has also gained worldwide attention as a popular gift. (Madon et al. 2002, in Eritja et al. 2005). Similarly, large nurseries in the Guangdong province of China, where the climate is suitable for Aedes albopictus, should be kept under observation (Madon et al. 2002, in Eritja et al. 2005). _ Ship:_ During the summer of 2001, containerised shipments from China of lucky bamboo (Dracaena spp.) were found to contain Aedes albopictus on inspection by quarantine officers on arrival at Los Angeles, USA (Linthicum 2001, in Eritja et al. 2005). This route of spread only became an issue after traders changed from dry freight to low cost shipping routes (which required the plants to be shipped in standing water to preserve them for the longer voyage). _ Transportation of habitat material:_ Movement of moist vegetation, wet tyres or water containers that can hold eggs or larvae.

Local dispersal methods Garden escape/garden waste: Natural dispersal (local): The adult flight range is quite short, as expected for a scrub-habitat mosquito (Eritja et al. 2005). Road vehicles: May be spread in trucks transporting used tyres. Transportation of habitat material (local): Movement of moist vegetation, wet tyres or water containers that can hold eggs or larvae (Eritja et al. 2005). Management information Preventative measures: Starting in 1992, several countries in South America (Venezuela, Chile, Bermuda, Costa Rica, Argentina and Brazil) have dictated embargoes on used tyre importations in an attempt to prevent mosquito introduction, protect local industries and prevent dengue introduction into areas where a potential vector, Aedes aegypti, is already present (Eritja et al. 2005). A. aegypti is a mosquito that caused outbreaks of dengue and yellow fever in Spain centuries ago (Eritja et al. 2005). Local laws on the quarantining of used tyres have been passed in Italy, but no tyre legislation exists at the national level (Eritja et al. 2005). Source reduction strategies (such as larval or adult control within tyre dumps) have proven to be difficult and relatively inefficient due to the shape and abundance of the water surfaces (Eritja et al. 2005). Quarantine and inspection measures in Australia have allowed detection of larval introductions of the tiger mosquito (Eritja et al. 2005).

Predicting the potential spread of the tiger mosquito may be important in alerting the appropriate authorities to take preventative action. The species could become established in northern Europe; as far as the southern coast of Sweden and Norway (Eritja et al. 2005). Areas at risk in Europe would have mean winter temperatures higher than 0°, at least 500mm rainfall per year and a warm month mean temperature of 20°. It is believed that less than 300mm rainfall per year would make establishment extremely unlikely. While climate-based forecasts are simplistic and because micro-climates play major roles in species distribution, they should not be ignored (Eritja et al. 2005).

In cases where no tyre trade is involved, some other goods must be monitored, such as plant material (e.g. lucky bamboo). When infestation occurs in densely populated urban or suburban areas, public awareness must be raised via information campaigns, as only a collective action in suppressing water-retaining containers on properties can help in avoiding mosquito breeding (Roger Eritja, pers.comm., 2006).

Nutrition Aedes albopictus obtains energy by feeding on plant nectar. Females require blood to produce eggs.

** Reproduction** Female Aedes albopictus lay desiccation-resistant eggs above the surface of the water in treeholes, tyres or other water-holding containers. They rely on rainfall to raise the water level and inundate the eggs for hatching. 150 to 250 eggs are laid per ovipostion. There are 1 to 4 ovipositions per female (ISSG 2004). The active reproductive period occurs in Japan and southwestern US from late spring to early fall (autumn) (Eritja et al. 2005). In Rome (Italy), larvae are found from March to November, but some females are active until December (Eritja et al. 2005). The eggs from strains colonising temperate regions resist lower temperatures than those from tropical areas (Eritja et al. 2005). Additionally, in these strains, the combination of short photoperiods and low temperatures can induce the females to lay diapausing eggs which can hibernate (Hanson and Craig 1995, in Eritja et al. 2005). Overwintering is necessary north of the +10°C January isotherm (Eritja et al. 2005).

Written by:
Richard Hartley

Richard is an avid blogger and the founder of Spanish Highs Sierra Nevada. He is author of the Cicerone Guidebook Walking and Trekking in the Sierra Nevada