Why do certain mosquitoes carry certain viruses

The most dangerous diseases that mosquitoes transmit

West Nile fever

This virus can be dangerous to the elderly or to those with weakened immune systems. It can cause meningitis in them, but also heart muscle inflammation.

The virus is native to African and Asian countries, but scientists have also proven it in southern France, the USA and Canada. But it is also up to mischief in Southeastern European countries. At least 25 people fell ill in Greece this year - two of them died as a result.

The actual number of infected people is likely to be higher, however: Most of the sick have no or harmless symptoms such as headaches and body aches. Only about one in five suffers from chills, a high fever, headache and drowsiness, followed by a rash later. A vaccination? So far, there are just as few as preventive drugs.

Zika infection

Aedes aegypti - the yellow fever mosquito - and Aedes albopictus - the Asian tiger mosquito - transmit the Zika virus. It occurs in the tropical areas of Africa, in South and Central America, but also in Florida and Texas. Areas in Southeast Asia are also affected. These include, for example, Thailand, Vietnam and the Philippines.

In 2015, many children were suddenly born in Brazil with the worst disabilities - with a reduction in the size of the skull called microcephaly. Women in the first trimester of pregnancy are particularly at risk, especially since the transmission often goes unnoticed.

In adults, not every infected person develops symptoms, but only around one in five: rash, conjunctivitis, joint pain and fever. The symptoms usually go away again. Researchers are still working on an effective vaccine.

This child was born with Zika infection

Dengue fever

Aedes aegypti are also carriers of dengue fever. For example, in the popular holiday destination Thailand, the tiger mosquito is native and up to mischief there. The virus occurs in large parts of Southeast Asia - from Afghanistan to Northern Australia but also in Sub-Saharan Africa and in Central and South America and some southern US states.

If you are stung and infected, the symptoms range from muscle and joint pain to headache and fever. However, anyone who has survived an infection with dengue fever can by no means feel safe. A second infection is much worse than the first infection.

96 million people develop dengue fever every year. This makes it the disease that is most commonly transmitted by mosquitoes. There is now a vaccine. However, this is subject to some restrictions because a vaccination can also trigger fatal reactions in the body.

In endemic areas where there is a high transmission rate, only children from the age of nine should be vaccinated with it and only seropositive people - i.e. those who have already been infected. The WHO recommends using the vaccine only in countries in which more than 70 percent of the population have developed antibodies against dengue.

Leishmaniasis

Sand flies can hardly be seen with the naked eye. These mosquitoes are dangerous because they transmit the infectious disease leishmaniasis, also known as oriental bumps. They are particularly at home in southern countries, for example in the Mediterranean or the tropics. But they have also been spotted in Germany. It is only the fertilized females that suck blood. Unfertilized females and male mosquitoes pose no threat. There are 30 different species of Leishmania. Animals, such as dogs, are most often infected by the parasitic single-cell organisms, but ten of the Leishmania species can also cause disease in humans.

Leishmaniasis has dire effects

The fatal: The first symptoms sometimes only appear after weeks or even months. It starts with a fever and a headache. The lymph nodes swell. The infected person feels tired and weak, and may lose a lot of weight.

Leishmaniasis affects different parts of the body. The nasal and throat areas are affected by leishmaniasis of the mucous membrane. A skin ulcer usually develops at the beginning. If left untreated, the disease spreads to cartilage and connective tissue and destroys them. This can lead to holes in the nasal septum, for example. But it can get worse. Namely, when intestinal leishmaniasis develops. It attacks important internal organs, such as the liver and spleen.

Around 12 million people worldwide develop leishmaniasis every year. The disease is curable, but the patient should see a doctor as soon as possible with the symptoms described. Without appropriate therapy, leishmaniasis can lead to death. There is no such thing as an effective vaccine.

More on this: Small bite, great danger: When a "vector" makes you sick

Mosquitoes dig into their skin with their proboscis

Sindbis fever

The nocturnal mosquitoes of the genus Culex transmit the causative agent of the so-called Sindbis fever. The virus occurs in African regions. Scientists have also been able to detect it in mosquitoes and in humans in European countries.

Initially, the affected person has flu-like symptoms and a fever. In individual cases, the body temperature can rise to over 40 degrees. Encephalitis can develop. After the first phase, inflammation of the joints occurs, which is typical for this infection. They get worse in the course of the disease, occur mainly on the wrists, fingers and ankles and are later accompanied by rashes.

If not treated properly, the condition can become chronic. Constant joint pain is the result. These are extreme cases. Usually, however, the human immune system can cope with the virus. The symptoms of the disease subside after a few weeks without any after-effects. There is no vaccination.

Yellow fever

The tiger mosquito, as well as some other mosquitoes of the genus Aedes, are responsible for yellow fever - a so-called flavi virus. The risk of being caught by the mosquito and developing yellow fever exists in 34 countries in Africa and 13 countries in South and Central America.

Areas close to forests in tropical countries are ideal environments for yellow fever infections

Scientists differentiate between three different transmission routes: In so-called bush or jungle fever, people are infected more by chance - there the mosquitoes transmit the virus between monkeys. If a person becomes infected, they can carry the virus into the city.

This is how the second route of transmission occurs, known as urban yellow fever. In metropolitan areas, the virus is transmitted from person to person and settles there. The third yellow fever cycle affects people in the fringes between forest and savannah, where mosquitoes, monkeys and humans live. There, infections from animals to humans and back take place again and again.

First, you experience a fever and flu-like symptoms. Those affected feel sick and vomit. If yellow fever is not treated, it can lead to meningitis or to vital organs being severely damaged or failing completely.

But there is also good news: You can vaccinate yourself against yellow fever. Some affected countries allow entry only for vaccinated people, for example Uganda and Sierra Leone. The vaccination lasts a lifetime.

Chikungunya

Chikungunya viruses are widespread in southern and eastern Africa, but also on the Indian subcontinent, on the islands in the Indian Ocean and in Southeast Asia. Like many mosquito-borne diseases, this condition is accompanied by a fever.

However, this usually only lasts for about three days. It is different with the severe joint pain that follows. They last a week or two, but then subside. Some of the infected people develop itchy, punctiform skin bleeding, but also lighter mucosal bleeding, for example from the nose. There is no permanent damage. If the disease is over, the patient is immune for the rest of his life. There is no vaccination.

malaria

Malaria is probably the best known tropical disease. The Anopheles mosquito transmits the parasite, a single cell called Plasmodium. Around forty percent of all people worldwide live in areas prone to malaria.

The disease runs in bouts of fever. The symptoms can be a mix of different signs of illness. These include headaches and body aches, sweats and chills, but also diarrhea.

Serious damage to the nervous system can occur in the course of the disease. Every year around one million people die from the infectious disease. The Anopheles mosquito feels very comfortable in warm areas, because in order to be able to transmit malaria, it needs the warmth. Only the females are active. They are the dangerous bloodsuckers. Although research is in full swing, there is still no reliable vaccination. However, there are drug treatments that can prevent it.

Mosquito nets offer effective protection against mosquitoes

Protection against mosquitoes

The general recommendation: mosquito repellent in the form of sprays, so-called repellants. In warm regions, mosquito nets are a good measure and light-colored clothing that should cover the entire body. In most cases there is no one hundred percent protection, unless there is a vaccination against the respective pathogen, but unfortunately this is far from available for all diseases that mosquitoes transmit.

  • Ticks - disgusting parasites or useful?

    Attention tick!

    There are around 900 species of ticks worldwide. With their eight legs, the little crawlers do not belong to the insects, but to the acari, the mites. They live in bushes or in the grass, waiting for a meal of blood to pass by. The most common type of tick in Germany is the common wood tick (Ixodes ricinus).

  • Ticks - disgusting parasites or useful?

    With sucking and pricking

    The ticks dig through the skin of their host with their forelegs and mouthparts. To do this, they are looking for particularly thin places where the capillaries are close below the surface. In fact, the majority of their food does not consist of blood, but of the lymph fluid that leaks from the wound.

  • Ticks - disgusting parasites or useful?

    Cure from tick saliva?

    Many ticks transmit bacteria or viruses that can lead to disease. In Germany, for example, borreliosis or encephalitis. Nevertheless, they also have their good points: Scientists from Oxford recently discovered that a protein in the saliva of ticks can inhibit inflammatory processes. This makes it a potential cure for a specific heart disease.

  • Ticks - disgusting parasites or useful?

    A plague for the moose

    Despite the new discovery, the negative tick stories predominate. For example, that shorter and warmer winters mean that moose in the eastern United States are struggling with an increase in winter ticks. According to the University of New Hampshire, 70 percent of elk calves died last winter - ticks sucked them empty.

  • Ticks - disgusting parasites or useful?

    Symbiosis to protect against parasites

    In Africa there are birds that pick ticks and other parasites from the skin of mammals. Here, for example, a yellow-billed maggot chopper (Buphagus africanus) who is "delousing" a warthog. The relationship benefits both. The pig gets rid of the bloodsuckers and the bird gets a nutritious meal.

  • Ticks - disgusting parasites or useful?

    With cigarettes against ticks

    Birds have ticks too. The Mexican house bullfinch has therefore developed a special strategy. A study in the Journal of Avian Biology showed that brooding house bullfinches "impregnate" their nests with cigarette butts. The nicotine acts as a protection against parasites, but as a nerve poison it can also have negative effects on the chicks.

  • Ticks - disgusting parasites or useful?

    No prospect of improvement

    Exterminating the annoying suckers is currently not on any agenda - and it would not be so easy either. They are extremely robust and survive both the washing machine and a short stay in the freezer. Anyone who has a tick bite should observe the bite and check the vaccination status.

    Author: Sophia Wagner