health

Can the tiger mosquito transmit the coronavirus?

The pandemic has paralyzed the world. With hundreds of thousands affected, Covid-19 has had a huge impact on the economy and has emptied public spaces across half the planet. The arrival of spring has found a large part of the population confined to their homes and with the cities practically empty. This time of year means that temperatures continue to rise and we have already had days of heavy rain. Conditions are ideal for mosquitoes to reactivate, and with its return, many people wonder if the tiger mosquito, or any other species of mosquito, can transmit the new virus.

Many people wonder if a mosquito can transmit SARS-CoV-2

The World Health Organization has made this clear: “to date, there is no information or evidence to indicate that COVID-19 can be transmitted by mosquitoes.” Furthermore, the WHO insists that “the new coronavirus is a respiratory virus that is spread mainly by contact with an infected person through the respiratory droplets that are generated when this person coughs or sneezes.”

If they transmit dengue, why not SARS-CoV-2, or the common cold?

The doubt is reasonable, because we know that some mosquitoes transmit viruses and other pathogens between people by biting them. If a tiger mosquito that bites a person infected with dengue can then transmit the virus to another person, can’t the same happen with the new SARS-CoV-2?

The same question arose in the late 1980s and early 1990s regarding HIV, until it was finally shown that the virus could not be transmitted by a mosquito. But HIV is not a rarity, viruses are the majority that cannot be transmitted by these insects. In fact, the rhinoviruses that cause the common cold belong to the Coronavirus family, and we will all agree that the cold is not transmitted by mosquitoes. Neither does the flu virus. Neither that of smallpox or Ebola.

It is common to think that if a mosquito has bitten a person infected with a virus, it can directly transmit the virus to its next victim. As if the mosquito was transfusing from one person to another, injecting the blood of its first victim into the next. But such a thing does not happen that way, because when a mosquito takes blood, it injects its saliva, but not the blood of its previous victim, who already digested days ago.

Puede un mosquito transmitir la COV-19

Fig. 1. Can a mosquito transmit COVID-19? There is no evidence of this, nor anything that suggests that this may be the case. Source: Mosquito Alert (CC-BY-NC-2.0)

 

The blood drawn by the sick person’s mosquito goes to their stomach, where digestion destroys viruses. This is the case, for example, with HIV, and with almost everyone else. For a virus to be transmitted by a mosquito, it must overcome a large number of barriers, which is not easy.

Arboviruses: viruses specialized in being transmitted by mosquitoes and ticks

The list of viruses that can be transmitted by mosquitoes may seem long, but it is very short when compared to the millions that cannot. Dengue virus (DENV), yellow fever virus (YFV), Zika virus (ZIKV), West Nile virus (WNV), Saint Louis encephalitis virus (SLEV), and chikingunya virus (CHIKV) stand out. ), the Ross River (RRV), Rift Valley fever (RVFV) among many other viruses. These mosquito-borne viruses are known as arboviruses, viruses carried by arthropods, mainly mosquitoes and ticks.

Viruses that can be transmitted by mosquitoes belong to a few families and are highly specialized. Not any virus can infect and be transmitted by a mosquito

Despite being enough, they represent a small proportion of the great diversity of viruses that exist. All arboviruses known to date belong to a few families of RNA viruses: Flaviviridae, Togaviridae, Bunyaviridae, Reoviridae, Rhabdoviridae, Orthomyxoviridae, and a single DNA virus from the Asfarviridae family. No virus in the Coronaviridae family, to which SARS-CoV-2 belongs, has ever been identified as an insect-borne virus.

The limited number of viruses that can be transmitted by mosquitoes is due to the ecological and evolutionary complexity that this implies from the point of view of the virus. It must not only be able to break through the immune system of a vertebrate organism (humans, for example), but also of the mosquito’s immune system.

Barriers that overcome arboviruses

In order to be transmitted by a mosquito, a virus must cross four main barriers. As it has already been said, the sucked blood, and the viruses that are in it, go to the mosquito’s digestive system (Fig. 2). The virus must survive in that hostile environment and be able to infect and replicate in the epithelial cells of the intestine. If you manage to overcome that barrier, then you still need to overcome the basal lamina that surrounds the intestine. Overcoming this second obstacle, the virus passes to the hemolymph and must be able to reach the salivary glands, which also pose a barrier to many viruses. Only if it can enter and replicate in the salivary glands can it be inoculated as soon as the mosquito bites another person. And it must replicate in large numbers because normally a few viruses are not enough.

Infección de un mosquito por virus

Fig. 2. The route of infection of a mosquito by a virus, showing the main barriers that it must overcome in order to transmit itself through its bite. (1) Survive the digestive system and replicate. (2) Overcome the basal lamina that surrounds the intestine. (3) Tackle the mosquito’s antiviral immune response without killing it. (4) Reach the salivary glands and overcome their barrier. Image modified from the original by Rückert & Ebel 2018, Trends in Parasitology 34: 310-321. Source: Mosquito Alert (CC-BY-NC-2.0)

 

Regardless of all these barriers, the virus must face the mosquito’s antiviral immune response, but without making it sick. The mosquito should not suffer consequences because if the pathogen it carries were to kill it, it could not be transmitted and the virus would harm itself. Only specialized viruses are capable of making this journey through the mosquito without succumbing to any of its defensive barriers.

As we can see, arboviruses are a group of highly specialized viruses that throughout their evolutionary history of millions of years have developed an intimate association, both with a vertebrate host and with a mosquito in order to perpetuate themselves. So this only happens between a few mosquitoes and a few viruses.

To date, none of the coronaviruses, such as SARS-CoV-2, SARS, or MERS, have been classified as arboviruses capable of infecting a mosquito and transmitted through its bites. Therefore there is no reason to think that the tiger mosquito or the common mosquito can transmit SARS-CoV-2.


References:

Ciota AT, Kramer LD. 2010. Insights into Arbovirus evolution and adaptation from experimental studies. Viruses 2: 2594-2617

Coronavirus Study Group of the International Committee on Taxonomy of Viruses. 2020. The species Severe acute respiratory syndrome-related coronovirus: classifying 2019-nCoV and naming it SARS-CoV-2. Nature Microbiology 5: 536-544

Hanley KA, Weaver SC. 2008. Arbovirus Evolution. In: Origin and Evolution of Viruses. pp: 351-391

Iqbal MM. 1999. Can we get AIDS from mosquito bites? The Journal of the Louisiana State Medical Society 151: 429-433

Kuno G, Chang GJ. 2005. Biological transmission of Arboviruses: reexamination of the new insights into components, mechanisms, and unique traits as well as their evolutionary trends. Clinical Microbiology Reviews 2005: 608-637

Rückert C, Ebel GD. 2018. How do virus-mosquito interactions lead to viral emergence? Trends in Parasitology 34: 310-321

Wolf YI, Kazlauskas D, Iranzo J, Lucía-Sanz A, Kuhn JH, Krupovic M, Dolja VV, Koonin EV. 2018. Origins and evolution of the Global RNA Virome. American Society for Microbiology 9: e02329-18

The tiger mosquito has been detected in Madrid for the second consecutive year

  • The General Directorate of Public Health of the Community of Madrid reports that tiger mosquitoes have been found in an urbanization within the framework of the actions of the “Entomological Surveillance Program and Sanitary-Environmental Control of Arbovirus Transmitter Vectors”.
  • These findings and those of the previous year confirm the suspicions sent by the citizens to Mosquito Alert since 2014 in the Madrid area.

 

On September 21st of 2018, the General Directorate of Public Health of the Community of Madrid confirmed the presence of a tiger mosquito in the Community after finding adult specimens in an urbanization of Velilla de San Antonio. The samplings have been made within the framework of the Regional Plan of Vigilance and Control of Vectors with interest in Public Health of the Community of Madrid with the collaboration of the Science Faculty of the Complutense University of Madrid. In this plan, there are 45 sampling points and 167 traps located in the main access roads to Madrid from Catalonia, Levante, and Andalusia. The most strategic points have been petrol stations, logistic and communication centers by road and rail, tire reuse centers, bus station, etc.

The Head of the Environmental Health Surveillance Area, Fernando Fúster, affirms that “it is still early to confirm that the tiger mosquito is established in the Community of Madrid and we lack many results, besides that the period of the year is no longer the most suitable for studies, but we believe that the insect could be quite localized “.

The professionals in charge of the samplings explain that the finding in the Velilla de San Antonio urbanization has been thanks to the notice of a neighbor who contacted the General Health Directorate sending a photo of the suspicious mosquito. The team traveled to the area to inspect the land and the surrounding houses, where they found larvae and adults of the tiger mosquito. From this positive sighting, two more areas of 150 and 400 m were established around the first house with traps that were also positive.

Citizen observations in Madrid.

 

This situation highlights the importance of citizen science for monitoring the tiger mosquito and how it can help follow-up programs. Between 2014 and 2016 the Mosquito Alert platform has already received several suspicious photos of tiger mosquitoes near Madrid, which probably corresponded to tiger mosquitoes but they did not get to check on the ground.

Since 2016, the Community of Madrid has established a collaboration agreement with Mosquito Alert to encourage the exchange of information between the platform and the Entomological Surveillance System of the Community of Madrid. It is expected to work together again and incorporate Mosquito Alert notices into the Program during the next 2019 season.

Pioneering UN Backed, Citizen Led Alliance against Mosquito Borne Diseases Joins Global Fight to Save 2.7 Million Lives Every Year

Initiative Empowers National Networks, Stakeholders and Governments to Generate and Access Real-time Data and Tools through UN Electronic Platform ‘Environment Live”.

Miembros participantes de la reunión a la sede de las Naciones Unidas (Ginebra).

Participants of the meeting at United Nations in Geneva. Frederic Bartumeus, John Palmer and Roger Eritja assisted as members of Mosquito Alert.

 

A new alliance of citizen-science organisations and UN Environment will be launched, Monday, in an effort to escalate the global fight against mosquito-borne diseases, responsible for killing close to 2.7 million people annually, mostly in Africa and Latin America. Overall mosquito borne cases are estimated at 500 million every year.

The new initiative, launched under the name ‘Global Mosquito Alert’, brings together thousands of scientists and volunteers from around the world to track and control mosquito borne viruses, including Zika, yellow fever, Chikungunya, dengue, malaria and the West Nile virus. It is the first global platform dedicated to citizen science techniques to tackle the monitoring of mosquito populations. The programme is expected to move forward as a collaboration involving the European, Australian and American Citizen Science Associations as well as the developing citizen science community in Southeast Asia.

Agreement to launch the initiative was reached at a two-day workshop that took place in Geneva earlier this month, organised by UN Environment, the Wilson Center’s Science and Technology Innovation Program (STIP), and the European Citizen Science Association (ECSA).

Director of Science at UN Environment, Jacqueline McGlade, said, “The Global Mosquito Alert will offer for the first time a shared platform to leverage citizen science for the global surveillance and control of disease-carrying mosquitos. It is a unique infrastructure that is open for all to use and may be augmented with modular components and implemented on a range of scales to meet local and global research and management needs.”

She added, “The programme will offer the benefit of the millions spent in developing existing mosquito monitoring projects to local citizen science groups around the world.  Opportunities to keep these citizen-led initiatives at the cutting edge of science will now depend on securing major funding to support the ongoing programme development and its promotion to millions of people world-wide.”

Los miembros de la iniciativa se reunieron durante dos días en Ginebra.

The members of the initiative were on a two-days meeting, lead by the Mosquito Task & Finish Group from ECSA.

 

The Global Mosquito Alert will be supported by a consortium of data and information providers, coordinated through Environment Live, the dynamic UN knowledge platform, designed to collect, process and share the world’s best environmental science and research. Built and maintained by UN Environment, the platform provides real-time open data access to policy makers and the general public, using distributed networks, cloud computing, big data and improved search functions.

The consortium includes: Mosquito Alert, Spain; MosquitoWEB Portugal; Zanzamapp in Italy; Muggenradar in the Netherlands; the Globe Observer Mosquito Habitat Mapper, USA/International and the Invasive Mosquito Project USA.

The information displayed on Environment Live will allow managers to mitigate risk and reduce health threats while opening up an opportunity for concerned citizens to contribute their mosquito observations and possible solutions.  Citizen data will augment information already available from Government public health sources.

The new consortium has agreed to share current approaches to monitor the spread of key mosquito species and their breeding sites, and to measure the nuisance value of the citizen mosquito experience to support health risk management.  The group also agreed to pool knowledge and experience on citizen science programmes to monitor mosquito species using the latest DNA identification techniques.

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