Anopheles, the Malaria Mosquitoes
Anopheles, the malaria mosquitoes
Malaria mosquitoes are mainly known as carriers of the malaria pathogens, the so-called plasmodia. Not everywhere in the world where Anopheles is found does the malaria pathogen occur.
The malaria mosquito is not a specific species like the yellow fever mosquito. In fact, one speaks of a very large group of different animals that can be found on all continents except Antarctica.
Distribution
Distribution of Anopheles
In order to understand the global risk of malaria infection, various health authorities and research institutes have conducted extensive studies to create databases and overview maps of the distribution of Anopheles mosquitoes.
Source: “Malaria Atlas Project”, a cooperation between Oxford University and the WHO — Presentation of 41 potential main vectors of the pathogen and their global distribution.
Source: Malaria Atlas Project / CDC
Source: World Malaria Report 2018
It should be noted that this map is only about the spread of potential transmission mosquitoes. Not in all distribution areas of Anopheles is the pathogen of malaria (Plasmodium spp.) found in mosquito populations. However, the map shows the high potential of the disease all over the world. Apart from a few islands in the Atlantic and Pacific Ocean including New Zealand, Fiji and New Caledonia, species of Anopheles can be found worldwide in the tropical, subtropical and temperate latitudes from China to Australia, from Canada to Argentina and from Finland to South Africa.
Identification
Characteristics
At first glance, Anopheles species differ from other mosquito species mainly by their typical posture. Other mosquito species at rest such as Aedes keep their body almost parallel to the ground. Malaria mosquitoes, on the other hand, show a clear inclination of 30 to 45 degrees to the front.
The body shape is very slim compared to other mosquitoes. It converges like an arrow to the front and does not show the clearly widened abdomen as found for example in house mosquitoes. Anopheles mosquitoes are usually much smaller. When magnified, one can see an evenly round dorsal shield (scutellum) and often scaly looking wings, which look like black and white shingles placed on top of each other.
The most obvious feature, however, are the so-called palps — a kind of tactile feeler which can be found on the left and right side of the proboscis. In malaria mosquitoes they are almost as long as the proboscis itself.
Anopheles (top) vs Aedes (bottom) resting posture. Photo: James Gathany, CDC
Larvae
The larvae also differ significantly from those of other mosquito species. While most mosquitoes seem to hang at an angle below the water surface, Anopheles larvae lie virtually flat on the underside of the water surface. This is due, among other things, to one of the most obvious physical distinguishing features: while other mosquito species carry a kind of snorkel (siphon) on their abdomen through which they breathe, Anopheles larvae have no comparable structure.
Behaviour
Behaviour of the malaria mosquito
In principle, malaria mosquitoes are active at dusk or at night. However, in recent years it has been observed that some populations can change their day-night rhythm in response to control measures. For example, Anopheles species have now been observed that have begun to seek their blood meals during the day in response to the widespread use of mosquito nets.
As a result of such and other adaptations, species of the genus Anopheles are now found in almost every habitat. Like all mosquitoes, malaria mosquitoes actually live on plant sap. However, the females also need certain nutrients from the blood of vertebrates to produce their eggs.
Life Cycle
The life cycle of the malaria mosquito
One to two days after the blood meal, the female lays the eggs on the edge of any water body. A puddle, a knothole, but also carelessly thrown away rubbish in which a little water has collected is enough for this.
Key difference from other species: Contrary to the genus Aedes, Anopheles mosquitoes lay their eggs directly on the water surface. Contrary to the genus Culex, the eggs do not form coherent boats but are clearly smaller and single in the water.
After one or two days the larvae hatch and live through the typical four larval stages in the following 10 days. This is followed by about 2 days in the final pupal stage before the adult mosquito hatches. In case of a female, the young animal is ready for its first blood meal after about 3 days.
Diseases Transmitted
What diseases does the malaria mosquito transmit?
As the name suggests, malaria mosquitoes are mainly known as carriers of the malaria pathogens, the so-called plasmodia. However, plasmodia are by far not the only pathogens that can be transmitted by a bite of Anopheles.
- Parasitic nematodes called filariae can also be carried by Anopheles from one host to another
- The O’nyong’nyong virus (ONNV), a relative of the Chikungunya virus, can be spread by Anopheles
- Different variants of equine encephalomyelitis can be spread by Anopheles
- Up to 51 different viruses can potentially be spread by Anopheles
However, as a vector for viruses they play a rather minor role compared to Aedes or Culex.
For detailed information on malaria including global statistics, transmission cycle, and prevention, see our Malaria page >
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See All Traps →References:
1) mosquito-taxonomic-inventory.info
2) ecdc.europa.eu – Malaria factsheet
3) Cell.com – Malaria research
4) BMC Genomics
5) Nature – Anopheles research
6) Malaria Atlas Project – malariaatlas.org
7) CDC – Anopheles distribution map
8) Developing Global Maps of the Dominant Anopheles (PDF)
9) Becker N, et al. Mosquitoes and their control. Second Edition. Berlin: Springer Verlag; 2010.
10) mosquito-taxonomic-inventory.info
12) Malaria Journal – Day-night rhythm adaptations