What new things might mosquitoes carry in Poland?
Insects and their importance in the spread of diseases
Insects are the most numerous and diverse group of animals. They are of great importance in the environment, both positive, such as pollination of utility plants, but also negative, because they can transmit dangerous pathogens. In an era of climate change (warm winters, hot and rainy summers) around the world, more and more attention is being paid to bloodsucking insects that are vectors for pathogenic viruses, bacteria and parasites. They are having an increasing impact on human and animal health, and the number of cases is increasing every year. New outbreaks of transmitted diseases are also becoming more frequent, even in regions where they did not occur before.
Where do transmitted diseases come from?
Vectors of transmission diseases such as ticks, flies and mosquitoes occupy a special place in the current One Health approach, aimed at achieving optimal health outcomes in view of the links between humans, animals, plants and their common environment. It is mosquitoes as common insects that are an important vector for numerous pathogens, including protozoa (e.g. Plasmodium – the birthplace of malaria), nematodes (e.g. Dirofilaria) or viruses (e.g. Dengue, Zika, Chikungunya). Among several dozen species of mosquitoes occurring in Poland, several of them can reproduce in huge numbers and be carriers of serious but poorly understood and diagnosed human and animal diseases. Due to changes in the spread of these insects, there are more and more reports of new pathogens not previously occurring in a given area. It is worth mentioning here that, for example, in Poland, the first native case of dirofilariasis in humans was recorded in 2008 (the authors of the publication were, among others, employees of General Biology and Parasitology of the Medical University of Warsaw), and now many similar cases have been described, the number of which is constantly growing. This indicates that the nematode, which has not previously occurred in our country, has found the right conditions for development here and will stay with us for longer.
Rare pathogens transmitted by mosquitoes - Spiroplasma, West Nile virus, Usutu
Poorly understood, mosquito-borne pathogenic bacteria include Spiroplasma bacteria. It is a gram-positive bacterium, commonly found in bloodsucking arthropods. The ability of Spiroplasma to reproduce in rodents has been experimentally proven, and infections with this bacterium have also been reported in humans. The possibility of infecting humans and other vertebrates with Spiroplasma spp. under natural conditions is largely unknown, as is the possibility of transmitting these bacteria by ticks and bloodsucking insects. Similarly, its clinical relevance is still poorly understood, but it is known that it can cause systemic infections.
Mosquitoes can also be vectors of poorly understood viruses, posing a potential threat to human health and life. Viruses such as Usutu (USUV) and West Nile Virus (WNV) are worth mentioning. USUV is a pathogen dangerous to birds and mammals, including humans, that can lead to inflammation of the brain and meninges. By contrast, WNV infection, which was reported in Europe in 1996, can be mild, manifesting only flu-like symptoms. However, in some cases it can eventually lead to encephalitis. Studies on birds and horses in Poland for WNV and Usutu showed the presence of antibodies against these viruses in some animals. This indicates the presence of the virus in the environment. However, it is not known what vectors transmit it, what the risk of infection is or when it is at its greatest.
New vectors, new pathogens, new threats
Climate change and frequent travel are leading to the establishment of exotic mosquitoes, such as the tiger mosquito imported to Europe. As a result, the list of pathogens present on our continent and in Poland is constantly changing. New species of mosquitoes, along with new pathogens, can enter Europe, posing potential threats and challenges to health protection. For this reason, old and new vectors and the pathogens they carry should be constantly monitored. It is known from the experience of other countries that it is possible to prepare for upcoming threats.
Project assumptions
The Miniatura project entitled "Molecular studies of the occurrence of viral and bacterial pathogens dangerous to humans and animals in mosquitoes in Poland" will investigate the incidence of new pathogens transmitted by mosquitoes. The research hypothesis assumes that mosquitoes occurring in Poland are an active vector of rare bacterial and viral diseases posing a threat to human health and life. These pathogens can reach Poland even from distant regions of the world along with migratory birds and travelers, by means of transport or through transported animals and be transmitted by native mosquito species, posing a potential threat to human health. The aim of the study is therefore to determine whether mosquitoes present in the Mazovian Voivodeship are vectors of rare and dangerous pathogens for humans.
Scope of research
In the Miniatura project, it is planned to conduct molecular analysis geared towards bacterial pathogens – Spiroplasma and viral pathogens – WNV, USUV and to secure samples for further analysis geared towards determining other pathogens. Mosquitoes and their larvae will be collected from Warsaw and the surrounding area (places with different anthropological pressure and areas with different types of development), using traps and other methods designed to catch mosquitoes and their larvae. Samples will be collected at different times of spring and summer depending on meteorological conditions and temperature. Mosquito-borne viruses will be detected by RT-PCR reaction. The literature indicates the high sensitivity and specific nature of this research method in monitoring WNV, Usutu or Zika viruses. Spiroplasma will be detected by PCR reaction. At the same time, the collected samples and isolates will be secured for future testing for other pathogens. Molecular analysis of mosquitoes for carriers of the above-mentioned viral and bacterial pathogens has not been carried out in Poland so far. The project will allow to verify the hypothesis of the transmission potential of health-threatening bacteria and viruses by mosquitoes. These will be important epidemiological data that can help assess the risk of transmission. I hope that the results of these analyses will be the beginning of a wide-ranging, multi-center study of pathogens transmitted by bloodsucking insects in Poland. To this end, talks are already underway about possible cooperation with other research centres from Poland and Europe.
Expansion of research
In the future, I plan to expand my research with further pathogens transmitted by bloodsucking insects, which are appearing in Europe, and extend the range of occurrence. On the territory of our country, in addition to mosquitoes, there are numerous bloodsucking insects, which can be potential vectors of dangerous pathogens. Therefore, molecular analysis of pathogens occurring, for example, in wrens (Lipoptena) and bloodsucking flies is planned. These insects can be a vector for Anaplasma phagocytophilum, Bartonella spp., Borellia spp., Francisiella or Rickettsia spp etc. The data that can be obtained will help to increase awareness of the occurrence of transmission pathogens and will be used by epidemiologists and doctors to predict the risk associated with a stung by a bloodsucking insect. These results may be crucial for the development of infection prevention strategies and the preparation of medical personnel for emerging new threats caused by rare or previously non-existent pathogens in Poland. Among other things, the implementation of another project would indicate areas of greatest risk, seasons, habitats or outbreaks of pathogens. In the light of numerous reports from around the world, I see the need to learn and describe the threats that vectors of transmission diseases may pose in Poland, and the Miniatura project is an introduction to wide-ranging activities that will result in an effective assessment of the risks associated with rare diseases transmitted by bloodsucking arthropods.
The project entitled "Molecular research on the occurrence of viral and bacterial pathogens dangerous to humans and animals in mosquitoes in Poland" in November 2022 received funding from the National Science Centre in the sixth round of the MINIATURA 6 call.
Edited by: Communication and Promotion Office
Fot. Michał Teperek; Communication and Promotion Office