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What Pests Carry Disease?

Last Updated: 27.09.20


Pests such as mosquitoes, bed bugs, fleas, or lice, as well as ticks, can transmit various diseases provoked by infectious agents like viruses (yellow and dengue fever, chikungunya virus), bacteria (plague, Lyme disease), or parasites (malaria, filariasis, leishmaniasis, or sleeping sickness). If you want to know more about these pests, you can check it out here.


The vectors

In case you were wondering why mosquitoes or ticks are called pests, it is because they like to bite us. The biggest problem is that they can provoke dangerous diseases through their bites. Some of them are life-threatening. 

In terms of disease analysis, these carriers are called vectors. Usually, these medical conditions thrive mostly in tropical environments, malaria being the dominant issue. In the next part of our article, we are going to present the vectors that carry diseases.



There are numerous types of mosquitoes all around the globe. Some of them are harmless when it comes to transmitting diseases, but some of them are really dangerous. For example, Anopheles, Culex, or Aedes, they all transmit various diseases and each species prefers different habitats, times when they are most active, and even types of bites. 

The larvae which produce the adults grow in areas of stagnant water such as reservoirs, lakes, ponds, or receptacles. They carry certain specific diseases according to the particular species, habitat, and climate. A few examples of such illnesses are malaria, dengue fever, yellow fever, chikungunya virus, lymphatic filariasis, or Japanese encephalitis. 

Moreover, their bites differ as well; some of them are painful, others are not. Their flight can be more or less noisy. It is also important to consider that half of all mosquito bites happen through clothing.



Flies and midges

Horse flies or Chrysops are the vectors for Loa Loa filariasis. Black flies or Simuliidae are responsible for transmitting onchocerciasis. Several members of the glossina genus, like the tsetse flies, carry the African trypanosomiasis, otherwise known as the sleeping sickness. 

Certain members of the phlebotominae family, such as the sand fly, transmit leishmaniasis. Furthermore, their bites are not felt all the times. Not only are flies responsible for transmitting harmful microorganisms, but they can also cause conditions associated with the growth and migration of their larvae beneath the skin. 

As an example, the Cayor worm is the larva of the Cordylobia anthropophaga fly that lays its eggs on the ground and also on linen and it can also infect humans. The contamination can happen either by laying or sitting down on the ground that is tainted with eggs laid by the fly or through clothes where flies have laid their eggs. 

This can happen while your clothes are outside drying, for example. There is an easy way to prevent this from happening by not sitting or laying down on the ground and also by not drying clothes in the open air. In areas populated by these flies, it is also recommended to iron the clothes in order to destroy any possible larvae presence. 


Bed bugs, lice, and fleas

The triatomines or Reduviidae, also commonly known as bed bugs can be found in various areas around the globe. It is a species that lives on the South American continent that can transmit the Chagas disease or American trypanosomiasis. These pests live in the walls of damp houses. Also, they are only active at night.

Lice, on the other hand, can transmit various bacterial infections such as bartonellosis or Trench fever, borreliosis or relapsing fever, as well as several types of rickettsiosis or typhus. The rat fleas are a vector for the plague.



There are many species of ticks and each one has its own specific habitat. They are worldwide-spread and are vectors for a lot of serious medical conditions such as Lyme disease, tick-borne relapsing fever, tick-borne meningoencephalitis, Crimean–Congo hemorrhagic fever, the tick-borne spotted fevers, Q fever, ehrlichiosis, tularemia, and babesiosis. 

Tick bites usually result from contact with grassland. The risk is regularly confined to certain regions that are well-defined. Once a tick is on your skin, it will usually migrate toward the major skin fold such as your armpits or groin, where it inserts itself. This is not a fixed rule, as ticks can fix on any part of your body. 

They do not start to feed immediately, but after 12 to 24 hours. That is why, if they are removed quickly, the risk of infection decreases. Besides the fact that serious diseases can be transmitted, the tick bite can cause local inflammation which can be highly pronounced in some cases. 



The frequency of the diseases mentioned previously is changing all the time. Thanks to the progress of vaccination measures and hygiene, some of these medical conditions have become rare. For example, cases of yellow fever, typhus, Japanese encephalitis, or plague have rarely been reported in the past years. 

There are others, such as trypanosomiasis, that have virtually disappeared but are now re-emerging. There are also diseases that are spreading, and the main reason is the continuous change in the climate. 

This also triggers changes in the ecology of the vectors. Such diseases, that are quite frequent in certain areas are dengue fever, Lyme disease, or chikungunya virus. In the next part of our article, we are going to describe some of these diseases. 




This disease represents the main health risk for travelers because it is very widespread in tropical and subtropical regions all around the world. Also, it can sometimes have a fatal outcome. 

The condition is caused by a unicellular blood-dwelling parasite of the Plasmodium genus, which is transmitted by the Anopheles mosquito. There are also various species that can transmit the disease.


Lyme disease

This is an infection caused by a species of bacteria from the Borrelia genus. Borrelia burgdorferi is carried and transmitted through the bite of ticks from the Ixodes genus. A percentage in the range of 10 to 15% of these ticks carry the bacteria. Furthermore, the risk of contamination by tick bite varies between 1% and 6%, mostly depending on the region. 

This disease is usually found in the northern hemisphere, in Eurasia and America especially during the active phase of the ticks, from May until October. The condition starts with a red skin lesion that is centered around the tick bite. It gradually spreads out and it usually disappears after a few days or even a few weeks. 

Other signs may appear after a few weeks or months that involve the joints and nervous systems, such as pain and paralysis, as well as heart rhythm abnormalities. Very rarely, there are other symptoms that can appear. 

Usually, this medical condition is more severe in Northern America than in Europe. The treatment for Lyme disease relies on antibiotics and admission to hospital may be necessary. 


Sleeping sickness

This condition is also known as Human African trypanosomiasis and it is a parasitic disease which is caused by the Trypanosoma protozoa. This is a unicellular blood-dwelling parasite, and there are several different species. The disease had virtually disappeared in the 1960s due to the action of the major disease mobile teams that were founded by Jamot. 

Unfortunately, the disease is now in full resurgence as a result of the issues disrupting the diverse health systems. This condition is transmitted by the tsetse fly through its bite. The insect is located only in Africa. These flies can often be found in the homes from the tropical and subtropical areas. 

The sleeping sickness affects rural populations, while the risk for travelers is limited. This disease advances in two stages. The first stage is the lymphatic or blood stage in which the parasite resides in the lymphatic system. The second stage is called the neurological stage when the central nervous system is affected. 

The development of the illness happens over a long period. If not treated, it will inevitably lead to death. The treatment consists of anti-parasite medication and it is very well-codified. However, it is also very hard to undergo. Fortunately, these drugs are very effective, provided they are administered in a timely fashion. 



Of course, these are only a few diseases out of the many that are transmitted by various pests. Some of them are confined to a certain area, and others can travel and spread all over the world. 

When you are about to travel, you should always inquire about possible pests and diseases that are common in that particular area. There are various preventive measures you can take in order to avoid returning with an unpleasant or even fatal disease.




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