mosquito

When a mosquito bites!

When a mosquito bites us, an itchy welt usually appears where the female mosquito has pierced our skin to suck a little blood with which to feed. This welt usually disappears in a few days.

Sometimes, however, a mosquito bite causes inflammation, pain and irritation in a larger area that leads us to scratch and even cause small wounds. As a general rule, their bites do not cause excruciating pain, but we are all aware that when several mosquito bites come together at the same time they can make us have a bad day.

But why do their bites bother and irritate? Do we really understand what happens when a mosquito bites us?

In fact, mosquitoes are much more complex than most of us realize.

How do mosquitoes bite us?

To survive, mosquitoes, both male and female, feed on plants and flowers, they obtain sugars that provide them with enough energy to carry out their basic activities, but when it is time to reproduce, females need extra energy for the development of the eggs. This energy is obtained from the blood, rich in proteins that allows the development of their eggs. In this way, the taste system and, above all, the olfactory system are crucial for the survival of mosquitoes in the environment. They help them identify and locate their food sources.

Both to pierce the stem of a plant and to suck blood from an animal, mosquitoes have a system called a biting-sucker formed by a stylet or proboscis that allows them to pierce and then suck the fluids.

The stylet is normally kept within a sheath formed by the lip, which protects and hides the rest of the mouthparts. When the mosquito lands for the first time on its potential victim, its pieces are still completely protected, the individual palpates the skin with the tip of the lip several times until they find the most suitable place to bite. This is usually the closest to a blood vessel.

The tip of the lip remains in contact with the victim’s skin, acting as a guide for the rest of the mouthparts, and it folds as the rest of the mouthparts pass through the skin. In order to surgically pierce their prey, mosquitoes have 6 mouthparts: 2 jaws, 2 maxillae, the hypopharynx and the labrum.

Partesbucales

Fig 1. Young-Moo Choo, Garrison K. Buss, Kaiming Tan, Walter S. Leal Front Physiol. 2015; 6: 306. Published online 2015 Oct 29.

The jaws are used to pierce the skin. The jaws are pointed while the maxillae are leaf-shaped and serrated. To introduce them, mosquitoes move their heads back and forth.

The hypopharynx and labrum, on the other hand, are hollow, acting as a tube. Through the hypopharynx they inject saliva with a very powerful anticoagulant protein. This protein prevents platelets from forming a clot, thus ensuring that the blood does not stop flowing while they ingest it. The labrum is the channel through which they suck blood and, therefore, feed. In fact, the mosquito is able to filter the red cells from the plasma and get rid of the water, thus leaving more space to store the nutrients from the blood in the abdomen.

Once they have stung us, they sneak away. In fact, we do not become aware of its action until the itch of the bite begins. Its evolutionary success is based on biting unnoticed.

Why do mosquito bites sting?

The key is in the saliva that they inject us to which we develop an allergic reaction. Each person develops it that if, in a different way.

Mosquitoes, like all blood-feeding arthropods, have mechanisms to effectively block the coagulation system of the vertebrates on which they feed. They do this with their saliva which contains a mixture of proteins.

Saliva contains a variable mixture of products, some with a vasodilator and anticoagulant effect, in addition to other proteins, the function of which is still poorly understood, but is probably focused on modulating the innate and acquired immune response of the host or victim.

Mosquito saliva therefore acts to reduce vascular constriction, blood clotting, platelet aggregation, angiogenesis, and immunity, thereby creating inflammation.

If we have never been bitten by a mosquito, our immune system will not have developed the antibodies dedicated to fighting these strange chemicals in mosquito saliva and therefore we will not sting. Instead, once the mosquitoes have bitten us, the immune system responds with antibodies. What these antibodies do is stimulate mast cells, another type of cell in our immune system. Mast cells when activated produce histamines.

Fig 2. Mosquito bites

The histamines are directed towards the affected area to destroy the foreign substances and causing the cells of the blood vessels to separate, then the liquids seep into the skin causing a small lump in the skin. This lump activates at the same time other receptors that generate the itch.

Unexpected variety of immune responses

In a 2018 study conducted by researchers from the Baylos School of Medicine (Texas), they described the effect of mosquito bites on human cells. The study was carried out with mice in which an immune system similar to that of humans was replicated.

The idea was to study in detail what previous studies had observed: that mosquito saliva improves the pathogenicity of dengue virus, West Nile virus and other arbovirus infections. The scientists hypothesized that mosquito saliva modulates the host’s (human or mouse) immune system in a way that promotes arbovirus replication and transmission.

To do this, the study looked at cytokines, proteins involved in communication between cells when the human body has to prepare an immune response that regulates the number and activity of different types of cells.

“We found that the saliva supplied by the mosquitoes induced a varied and complex immune response that we did not expect,” said co-author Dr. Silke Paust, assistant professor of pediatrics at Baylor and Texas Children’s Hospital.

The results suggest that mosquito saliva alters the frequencies of various cells of the immune system, in multiple tissues, several hours and days after blood suction and saliva injection.

They found that cytokine levels increased dramatically even 7 days after the bite. The fact that these effects last up to a week is especially concerning in the context of allergic reactions. The long-lasting effects seen in the bone marrow and skin cells of altered mice could explain how some of the mosquito-borne viruses might be viable in these tissues, which in turn could serve as replication reservoirs and spread through of them to the rest of the body.

Mosquitoes and the diseases they transmit are a growing public health problem. Understanding how mosquito saliva interacts with the human immune system not only helps us understand the mechanisms of disease pathogenesis, but could also provide possibilities for its treatment.


References

Ribeiro JM, Francischetti IM (2003). “Role of arthropod saliva in blood feeding: sialome and post-sialome perspectives”. Annual Review of Entomology. 48: 73–88. doi:10.1146/annurev.ento.48.060402.102812. PMID 12194906.

Valenzuela JG, Pham VM, Garfield MK, Francischetti IM, Ribeiro JM (September 2002). “Toward a description of the sialome of the adult female mosquito Aedes aegypti”. Insect Biochemistry and Molecular Biology. 32 (9): 1101–22. doi:10.1016/S0965-1748(02)00047-4. PMID 12213246.

Vogt MB, Lahon A, Arya RP, Kneubehl AR, Spencer Clinton JL, Paust S, et al. (2018) “Mosquito saliva alone has profound effects on the human immune system”. PLoS Negl Trop Dis 12(5): e0006439. https://doi.org/10.1371/journal.pntd.0006439

Young-Moo Choo, Garrison K. Buss, Kaiming Tan, Walter S. Leal.  “Multitasking roles of mosquito labrum in oviposition and blood feeding”. Front Physiol. 2015; 6: 306. Published online 2015 Oct 29. doi: 10.3389/fphys.2015.00306

The art of catching mosquitoes

Mosquito sampling is a very complex task. But why are we interested in capturing mosquitoes?

One of the reasons is to carry out scientific studies, and the other, to try to reduce the amount and make us feel better at home (control method). In the second case, we have to achieve massive captures, why will we only notice an improvement if we eliminate most of the mosquitoes.

Adult mosquitoes can be captured in two ways: actively or passively. In the first case, we will move to the points where we think there are mosquitoes and we will try to capture them with special vacuum cleaners and normally, aspirating to the places where the mosquitoes rest during the day. It would be the equivalent of entomologists and entomologists who study butterflies, with their hose. This method does not allow to capture many specimens, since logically, they escape.

In passive captures, devices are used that are very attractive to mosquitoes, and thus make them come to a specific point where they can be captured and automatically absorbed by the machine, which keeps them alive in a space inside or not.

The attractiveness of these traps is the most important factor for them to be effective, especially if we want to eliminate a high number of mosquitoes from the environment. This attractiveness is achieved by knowing the stimuli that mosquitoes use, and also their biological cycle and what they need at all times.

How do mosquitoes find us?

To understand how mosquito traps work, we must first understand how mosquitoes search for and find humans. Mosquitoes use multiple senses to find their victims.

Most find humans through the carbon dioxide (CO2) we breathe out. It is a long-distance detection method that mosquitoes use to find their victims from afar. In contrast, when they are closer, mosquitoes can detect the heat and odor of our bodies, such as lactic acid. Some species of mosquito can even detect movements and colors.

respiración CO2 dióxido de carbono mosquito picadas

Fig. 1: The path that a mosquito makes to detect its host. Once it has detected a CO2 trail (a), it zigzags against the current (b) to detect where the trail is coming from (c). When he traces the trail, his visual field is activated (d), the closer he receives stimuli from other body odors (e) that he has just confirmed closer (f). Finally, thermal sensors allow you to locate a good area to land and bite into (g). Source: Mosquito Alert (CC-BY-NC-2.0)

If you want to know what makes some humans more attractive than others for mosquitoes, you can read it in this previous blog post: Why do mosquitoes bite me so much?

How do mosquito traps work?

Normally we are interested in catching mosquitoes before they bite us.

In order to capture hungry females, the traps simulate the presence of a person or an animal. The most effective devices are therefore those that best mimic this presence, incorporating chemical baits, such as extracts from human sweat odors, or carbon dioxide, which many mosquitoes use to locate the victim based on their breathing.

Now, although CO2 and sweat are effective in attracting mosquitoes that are hungry for blood, we must bear in mind that if we want to capture them at other times we will need different baits and traps. For example, a female that has already developed the laying of eggs in her abdomen will not bite us in any case because she is not looking for blood but a sheet of water where she can free herself from her eggs.

This water is located by the own odors that emanate when it has been stagnant for a long time, and it can also be done visually. Therefore, a trap that wants to capture females with eggs will be completely different. These traps will have another structure with water inside, and with the smell of wet organic matter.

All this is complicated if we consider that many species of mosquitoes have very different behaviors from each other.

A mosquito of daytime habits can be guided by sight to discover a prey, but a nocturnal one needs smells, because it cannot see us. That is why the diurnal ones such as the tiger mosquito (Aedes albopictus) tend to act preferably outdoors, while the nocturnal ones (such as the common mosquito, Culex pipiens) usually act inside the houses, where the enclosed air of the rooms allows them better orient yourself towards the body of the person who is in bed in the dark by following only the smell and the heat of the body.

Therefore and as a general rule, traps based on odors and on the emission of light are effective on nocturnal mosquitoes, while those that use visual attractions can work with diurnal species. Certain types of traps combine these tricks and are quite useful against various types of mosquitoes, especially adult tiger mosquitoes. The traps are most effective when carbon dioxide is added.

  • PASSIVE TRAPS

Passive traps are designed to attract female mosquitoes that have already bitten and are looking for a place to lay their eggs. Therefore, they must mimic the conditions of a breeding place that are suitable for mosquitoes.

Of these traps we can find simpler or more complex. The simplest consist of a plastic pot with a wooden stick where the females lay their eggs. In this case, the females can get out of the trap, they are not trapped. These are called oviposition traps since they allow to collect the substrate where the eggs have been laid and take it to the laboratory to be able to do the follow-up and monitoring.

Oviposicio sencilla

Fig.2: Oviposition trap scheme (Source: Mosquito Alert CC-BY 2.0)

The most complex ones have a black entrance tunnel that takes the mosquitoes to a chamber (which is usually light or transparent in color) and where they are captured. In this chamber we find an adhesive sheet where the females are stuck and die. This type of traps does not allow to collect the eggs of female mosquitoes since they usually stick together before laying them.

TrampaPasiva

Fig.3: Scheme of a passive trap to attract female mosquitoes (Source: Mosquito Alert CC-BY 2.0)

They can be used to detect the presence of Aedes aegypti, Aedes albopictus, or another huge variety of female Aedes mosquitoes.

Interpreting data from an oviposition trap requires some caution, as they compete with natural habitats for larvae and estimates from traps may not accurately reflect the number of female mosquitoes in the region.

  • ACTIVE TRAPS

Active traps are thought and designed to attract adult mosquitoes.

In general, these combine black and white colored structures to attract mosquitoes towards a central opening where suction takes place, with the emission of specific organic odors, and that reach their maximum effectiveness when carbon dioxide is added.


The gas is released through an opening in the upper part of the trap, thus adding a cloud of CO2 that is added to the column of aromas directed upwards inside the trap. This fact mimics the natural spatial distribution of human body odor and our breathing. This addition of carbon dioxide greatly improves the sensitivity of the trap for both Aedes albopictus and Aedes aegypti.

TrampaActiva

Fig.4: Active trap scheme for capturing adult mosquitoes (Fuente: Mosquito Alert CC-BY 2.0)

Factors that condition the effectiveness of traps

There has been a lot of debate as to whether mosquito traps are effective in limiting mosquito populations. The effectiveness of a mosquito trap depends on many factors, including:

  • Location. The location of the trap has a very important impact on the success or not of the capture. Mosquitoes are insects that need to protect themselves from dehydration. Therefore, most will avoid direct sunlight and wind. Shady, sheltered places with high humidity will be your favorites.
  • Weather conditions. Weather conditions also have a strong impact on the effectiveness of a trap, especially the wind.
  • Mosquito species. There are more than 3000 types of mosquitoes in the world. Each of them is attracted to different substances and stimuli. Some are more attracted to CO2, others to heat, and others to human and animal skin odors. This means that different attraction methods will be effective on different mosquitoes.
  • Trap type. There are many different mosquito traps on the market. Each differs in the way it attracts and traps mosquitoes. Some are of high quality and work well in most areas, while others can be almost useless.
  • Time. The time we have the trap installed is also a crucial factor for its effectiveness.

There is no absolute catch

The reality is that there are many commercial models available for all of these machines. However, as we can see, there is no absolute trap, but it depends on the species to which we direct it, the moment of its life that we want to capture, and the purpose of the sampling.

If you were thinking about the control of tiger mosquitoes in our garden, but, it must be said that the most effective method is still the suppression of the breeding points. That is, prevention.

PrevenirMosquito

Fig. 5: Objects that can accumulate water in our outdoor spaces where the tiger mosquito can reproduce. (A) Sprinkler. (B) Plates from the pots. (C) Truck. (D) Bottles and other cans in disuse. (F) Vases. Source: Mosquito Alert (CC-BY-NC-2.0)

Some of these traps – of a professional and high cost type – can relieve us of the mosquitoes that bite us, but it is always more definitive and economical to eliminate the problem from the source, right?


References

· Articles / guides:

World Health Organization. Efficacy-Testing of traps for control o Aedes Spp. mosquito vectors. WHO/CDS/NTD/VEM/2018.06. 42 pp.

Centers of Disease Control and Prevention (CDC). Surveillance and Control of Aedes aegypti and
Aedes albopictus in the United States. September 2017. 16 pp.

Mackay, A.J., Amador, M. & Barrera, R. An improved autocidal gravid ovitrap for the control and surveillance of Aedes aegyptiParasites Vectors 6, 225 (2013). https://doi.org/10.1186/1756-3305-6-225

Reiter, P., Amador, M.A. & Colon, N. Enchancement of the CDC ovitrap with hay infusions for daily monitoring of Aedes aegypti populations. Journal of the America Mosquito Control Association, Vol.7, Nº1 (1991).

Fay, R.W. & Donald, A.E. A preferred oviposition site as a surveillance method for Aedes aegypti. Mosquito News, Vol.26, Nº4 (1966).

· Web:

Bioagents AG. www.biogents.com. Consultada a fecha 20/08/2020.

AMCA, The American Mosquito Control Associaton. www.mosquito.org. Consultada a fecha 10/08/2020.

 

International demand for goods contributes to malaria risk

Previous studies have shown that deforestation and disturbance of tropical forests lead to increased transmission of malaria. The destruction of the jungle generates new environmental and ecological conditions in which mosquitoes thrive better. A new study links global demand for goods with deforestation and the risk of malaria.

The work is the first to directly relate global consumption to the increase in malaria cases in some regions. It is estimated that in these regions where cases are increasing, a fifth of deforestation is driven by international trade. Coffee, wood, soy, cocoa, palm oil, tobacco, calf meat and cotton are the main products demanded globally that stimulate deforestation.

Despite the fact that globally it seems that the number of cases has been decreasing since 2000, its increase is worrying in some regions. In 2018 there were 228 million cases worldwide and 405,000 deaths, of which seven out of ten were children under the age of five.

7 out of 10 deaths from malaria worldwide are children under the age of 5

90% of malaria cases occur in three tropical forest regions: the Congo Basin, the Amazon Basin, and the Greater Mekong Basin in Asia (Fig. 1). In these regions, the main mosquitoes that transmit malaria are: Anopheles gambiae, Anopheles funestus, Anopheles dirus, Anopheles minimus and Nyssorhynchus darlingi. All of them associated with deforestation, land use changes and human migration.

Distribución malaria Africa America asia

Fig. 1. Map of the regions with populations at risk of contracting malaria in yellow. Striped areas represent the areas that are suffering the most deforestation. Simplified map of Chaves et al. 2020. Nature Communications 11: 1258. Source: Mosquito Alert (CC-BY-NC-2.0)

Demand for basic products from rich countries increases the risk of malaria in other countries

The link between deforestation and the increase in malaria cases has been demonstrated in Indonesia, Nigeria and the Amazon. A work carried out in 795 municipalities of the Amazon during 13 years, concluded that clearing the forests by 10% leads to a 3.3% increase in malaria cases.

The new study reconnects the incidence of malaria with deforestation, but also establish a relationship between deforestation with the consumption of products globally. For this they used a detailed international database with the entry and exit of products by country. With it they were able to establish the global network of supplies, from the deforested area to produce, to the countries that consume the product.

Countries with an increased risk of malaria associated with deforestation are Nigeria, Tanzania, Cameroon, Uganda, the Democratic Republic of the Congo, India, Zambia, Burma, the Central African Republic and Burundi. Part of the increased risk in these areas is due to the demand for products from the richest countries, with Germany, the United States, Japan, China, the United Kingdom, France, Italy, Spain, the Netherlands and Belgium leading the list. The demand for wood, cocoa, tobacco and cotton are among the main causes of deforestation.

Populations most exposed to malaria are those that benefit the least economically from forest exploitation

The work is new evidence of the close relationship between the health of human populations and the environment, and shows, with numbers, that the problem is global. The authors hope that their results can be used to mitigate malaria cases, either by regulating supply chains or by labeling and certifying products.

Communities that are facing a greater transformation of their landscape to meet international demands are at the same time the most at risk as they are more exposed to mosquitoes that transmit malaria. In addition, the populations most exposed to the disease are those that benefit least from the exploitation of forests.


References

Austin K, Bellinger M, Rana P. 2017. Anthropogenic forest loss and malaria prevalence: a comparative examination of the causes and disease consequences of deforestation in developing nations. AIMS Environmental Science 4: 217-231

Berazneva J, Byker TS. 2017. Does forest loss increase human disease? Evidence from Nigeria. American Economic Review 107: 516-521

Chaves LSM, Fry J, Malik A, Geschke A, Salud MAM, Lenzen M. 2020. Global consumption and international trade in deforestation-associated commodities could influence malaria risk. Nature Communications 11: 1258

Garg T. 2019. Ecosystems and human health: the local benefits of forest cover in Indonesia. Journal of Environmental Economics and Management 98: 102271

MacDonald AJ, Mordecai EA. 2019. Amazon deforestation drives malaria transmission, and malaria burden reduces forest clearing. PNAS 116: 22212-22218

 

Mosquitos, zancudos, jejenes, cínifes y trompeteros. ¿Quién es quién?

Los entomólogos tenemos un problema de comunicación en ambos sentidos, tanto al hacer divulgación, como cuando recibimos consultas desde la ciudadanía. Al carecer de nombres comunes para muchos insectos, no es fácil ponernos de acuerdo acerca de quién estamos hablando realmente. Los nombres comunes tienen una utilidad práctica y el cuerpo de conocimientos que denominamos sabiduría popular es extensísimo, pero a  veces, es bastante inconcreto. Así, nos encontramos a menudo con que el término “mosquito” es usado para designar cualquier insecto pequeño y oscuro, especialmente si resulta ser picador.

 

No todo lo que nos pica es un mosquito

En el mundo académico, por su lado, la Taxonomía, la ciencia que se encarga de clasificar los organismos vivos, ordena los insectos bajo un sistema de nombres complejo, jerarquizado y basado en el latín, que lo hace todavía más incomprensible. Aquí, un mosquito pertenecerá al Phylum Arthropoda, Clase Insecta, Subclase Pterygota, Orden Diptera, Suborden Nematocera, Infraorden Culicomorpha, y Familia Culicidae. Finalmente, su denominación única será un apellido (que va delante) y un nombre de pila: algo así como Aedes geniculatus. Esto, obviamente, no es muy manejable para los usos comunes.

Sin embargo, cuando una especie tiene una gran relevancia social sí recibe un nombre común. Éste sería el caso del mosquito tigre, que se llama así en la mayoría de los idiomas del planeta. Otros mosquitos no han tenido esa suerte, como el Aedes aegypti, que es llamado “mosquito de la fiebre amarilla” en una solución de compromiso no muy usada por la ciudadanía, ni aceptada por la RAE. En estos casos, la solución más aceptada suele ser transliterar o usar directamente el nombre de especie en latín (“el aegypti”).

A nivel de diferenciar grupos es imprescindible mantener algún tipo de concreción. Y el problema es que hay varios grupos de insectos metidos en el mismo saco. Su variedad morfológica está ligada a la evolución y a sus relaciones de parentesco. Estas variaciones implican diferentes modos de vida, distintos lugares de cría, diferentes niveles de agresividad sobre nosotros, y variación en los métodos para combatirlos. Si el tamaño de esos bichos fuese suficiente como para verlos sin la ayuda de una lupa, entenderíamos la enorme variedad de formas que existe en ese mundo, al igual que sucede entre los grandes animales.

Nadie confundiría a un perro con un gato, ni a ninguno de ellos con una foca ¿verdad? Algunos grandes rasgos comunes agrupan a estos animales dentro de la Orden de los Carnívoros, el cual se inscribe a su vez en la Clase de los Mamíferos. Pero son tremendamente distintos entre sí, perteneciendo a las familias de los cánidos, félidos y fócidos, respectivamente.

Estas mismas diferencias existen entre las familias de pequeños insectos picadores, sólo que no las percibimos porque no nos resultan visibles por su pequeño tamaño. Vamos a intentar aclarar un poco a quién es quién entre los insectos picadores.

Para empezar, podemos descartar piojos, pulgas, chinches o garrapatas, que son picadores pero no voladores, y pertenecen a grupos muy diversos entre sí. Digamos que la mayoría de los insectos picadores que vuelan pertenecen al orden de los Dípteros, que agrupa a los insectos que sólo tienen dos alas, a diferencia del resto, que tienen cuatro. Necesitamos básicamente distinguir 4 familias: los Culícidos, los Psicódidos, los Simúlidos y los Ceratopogónidos.

Los mosquitos son culícidos

Los culícidos son los únicos que se pueden llamar mosquitos en sentido estricto, según el diccionario de la RAE. A veces se utiliza de forma local los términos “cínife” (del griego antiguo knipós, insecto picador) o “zancudo”, especialmente en América latina. Sus larvas son acuáticas pero necesitan aguas estancadas porque respiran oxígeno atmosférico. Los culícidos son transmisores de enfermedades humanas graves, como paludismo, dengue, Zika, chikungunya o fiebre amarilla.

Los flebótomos son psicódidos

Los psicódidos incluyen los flebotomos, que son los transmisores de la leishmaniosis a los perros y -esporádicamente en nuestras latitudes- también a los humanos. Se les suele denominar así por castellanización del nombre latín del género más importante (Phlebotomus, que de hecho significa “cortador de venas”), pero esta vulgarización no está aceptado por la RAE. Sin embargo el capitán Haddok en las aventurás de Tintín sí que utiliza flebótoma entre sus múltiples expresiones. En inglés se las conoce como Sandflies, o “Moscas de la arena”. Son bastante más pequeños que los mosquitos, peludos, y difíciles de ver por su vuelo rápido y saltarín. Pican muy rápido y a menudo de forma múltiple, en secuencia lineal sobre la piel. Sus larvas se desarrollan en suelos húmedos y ricos, así como en los excrementos de los animales. Demasiadas veces hemos oído hablar del “mosquito de la Leishmaniasis” lo que es un error grave: un culícido es incapaz de transmitir esa enfermedad, del mismo modo que los flebotomos no pueden transportar el dengue.

Las moscas negras son simúlidos

Los simúlidos son llamados moscas negras, en traducción del nombre inglés Blackflies. También son pequeños, y son rechonchos, oscuros y resistentes porque están blindados de quitina. Su picadura puede ser dolorosa, pues su saliva contiene potentes alérgenos que provocan reacciones dérmicas importantes. Sus larvas se crían en los ríos y otros cursos de agua, fijadas en el fondo; pero en este caso, a diferencia de los mosquitos, el agua tiene que estar, imperativamente, en movimiento. Los simúlidos son excelentes voladores y pueden afectar zonas urbanas muy alejadas de sus puntos de cría. Son transmisores de la ceguera de los ríos en África, pero no de leishmaniasis ni dengue, claro.

Los jejenes son ceratopogónidos

Finalmente, en América latina se llaman jejenes a los ceratopogónidos (de la palabra arahuaca Xixén). En este caso es un nombre reconocido por la RAE, que los describe con precisión y los diferencia expresamente de los mosquitos. Son más pequeños que ellos, muy moteados y pueden atacar en enjambres invasivos y muy molestos. Tienen un claro interés agropecuario, ya que son los transmisores de la peste equina africana y de la lengua azul de las ovejas, entre otros. Sus larvas las encontramos en los fangos de las granjas y sus abrevaderos.

Aquí tenéis unas imágenes ampliadas para que podáis daros cuenta de las diferencias morfológicas entre estos grupos, que como veis, tienen modos de vida muy distintos, desarrollan las larvas en lugares diferentes y pueden (o no) transmitir enfermedades específicas. Arriba a la izquierda un culícedo o mosquito (Aedes aegypti); arriba a la derecha un psicódido o flebótomo (Phlebotomus papatasi), abajo a la izquierda un simúlido o mosca negra, y abajo a la derecha un ceratopogónido o jejenes.

 

Como veis, para los profesionales es muy importante hacer la distinción, porque al igual que cualquier otro profesional, antes de aplicar una solución necesitamos una diagnosis correcta. Normalmente, la mejor forma de controlar las plagas es ir a la raíz del problema, es decir, eliminar las larvas. Y para estos cuatro grupos, deberíamos irlas a buscar a lugares y ambientes distintos. A los culícidos en charcos de aguas estancadas, a los flebotomos bajo el césped del jardín, a los simúlidos en un río caudaloso y a los ceraptogónidos en fangos cercanos al abrevadero.

Porque al igual que no es oro todo lo que reluce, ni nuestro gato es un perro… no todo lo que vuela y pica es mosquito.

“In Spain there are many mosquito species whose distributions are unknown because there aren’t many people studying them”

This March the journal Annals of Biology publishes an article documenting the first finding of the mosquito Aedes vittatus in Galicia, a finding made through citizen participation in the Mosquito Alert platform. This is a native mosquito which is known to exist in different areas of Spain, but up to now it had never been documented in Galicia.

For over three years the Mosquito Alert has continued in its mission to monitor and study the tiger mosquito in Spain with the help of citizens. Using the Mosquito Alert app, anyone can send photos of the mosquito and its breeding sites in order to improve its tracking and control.  The project has also added the yellow fever mosquito, not currently present in Spain with the exception of a few individuals recently found in the Canary Islands. Though tracking of other mosquitos is not the main focus of efforts, the project’s activity has however now led to the identification of a native mosquito species in an area where it had never been found before. The finding was made by a volunteer using the app thinking that they had found a tiger mosquito.

Roger Eritja is the head of a team of experts who validate the sightings sent to the citizen science platform Mosquito Alert, a project coordinated by CREAF, CEAB-CSIC, and ICREA. Entomologist at the Baix Llobregat Mosquito Control Service and nature photographer, Roger has worked in management and control of mosquitos for more than 35 years. In particular, he had a key role in finding and studying the tiger mosquito in Spain when it was found for the first time in 2004.

What does it mean to have found this mosquito, Aedes vittatus, in Galicia?

Finding species in new places without a doubt improves our knowledge of biodiversity. We could know a lot more about the distribution of mosquitos if only more people would work on this subject. Historically, this field has not been given much attention. In fact, it is very likely that this species in particular, Aedes vittatus, is much more widely distributed than thought, the problem is a lack of studies to document it. There aren’t many specialists searching for mosquitos, but that said the situation has improved over the past number of years.

Ejemplar de Aedes vittatus. Foto: El desinsectador - desinsectador.com

Aedes vittatus. Photo: El desinsectador – desinsectador.com

Why are there so few mosquito experts if it is exactly this group of organisms which is so deadly?

Mosquitos have been the cause of huge historical endemics; nevertheless, there have been many periods during which they have been forgotten. With the arrival of the epidemics a lot of work was done in the scientific and sanitary fields, but once the diseases disappeared interest was also lost. During the first half of the 20th century for example there were a lot of studies of mosquitos due to the occurance of malaria and since it became understood that the epidemics yellow fever and dengue experienced over the previous two centuries were caused by Aedes aegypti.  During this period we had classic experts including Pittaluga, Arias, De Buen, and Gil Collado, among many others.  Later, following the devastation of the post-war period, malaria was finally eradicated, and so then it wasn’t until the 1980s that a seminal book by Encinas Grandes was published, “Taxonomy and biology of the mosquitos of the Salamanca region (Diptera, Culicidae).” It was around that time that the first public services for mosquito control were established and that the topic was again given attention.

Currently, worldwide colonization by the tiger mosquito and the risks this poses to public health has led to increased studies on culicides.  That said, the potential health impacts of mosquitos in Europe is moderate since EU countries have resources for prevention and intervention.  Most efforts are focused in disadvantaged countries where these diseases are endemic and have higher human tolls.

Going back to Aedes vittatus in Galicia, tell us about this finding.

On September 12th 2017 we received a photo sent from Galicia via the Mosquito Alert app, specifically from the province of Pontevedra. At first the team of expert validators thought that it could be a female tiger mosquito, but it was a bit strange because it also seemed to have characteristics of another mosquito which had never been found in Galicia.  This is when we decided to open an invetigation in order to find out exactly what mosqutio species it was.  For this a photo wasn’t enough, we would have to get a well-preseved individual.

Screenshot of the report in the map.

How did you contact the person who sent the photo?

At that time we only knew that it had been sent by someone in Galicia but we didn’t know their name or any other personal information since the users of the app are kept in complete anonymity. However, the Mosqutio Alert app is equipped to send notifications to the mobiles of the users, so this is how we got in contact with this person who in fact repsonded immediately. We asked them to capture another mosquito of that type and send it to us by mail. And that’s what they did. In fact this person had some knowledge of biology and this was a great help since they followed the instructions quite well. For instance, they put it in the freezer to kill it without shaking the sample too much and this helped preserve the animal intact. Once it arrived to the laboratory I was able to examine it and confirm that it was not a tiger mosquito but rather another species which had never been found in Galicia, Aedes vittatus.

If this person sent the photo thinking that it might be a tiger mosquito they must have a very similar appearance.

Aedes vittatus is black and also has white lines on the abdomen and legs. This is the reason that someone may be mistaken to believe that it is a tiger mosquito. However, the thorax is what is different: the tiger mosquito has a white line and Aedes vittatus has between 4 and 6 white spots.

What is notable about this mosquito?

The mosquito Aedes vittatus is active during the day and especially when the sun is setting. It will suck the blood of any mammal. The habitat for its larvae are holes in rocks along streatms and rivers, where it lays its drought-resistant eggs in the mud just above the water line. These larval breeding places are characterized by their exposure to direct sunlight and for having fresh water, though the species can also tolerate some degree of brackishness. They are also occasionally found in artificial containers and in flooded tree cavities.

Images of some morphologic characters. Author: R.E./CC-by Mosquito Alert

 

This is the first time that this mosquito has been found in Galicia, but its presence in many other places in Spain has already been known for years. Is it an invasive species like the tiger mosquito?

Aedes vittatus is not an invasive species, you could say it has a “residence permit.” It was described for the first time in Corsica with the name Culex vittatus by the naturalist and entomologist Jacques-Marie-Frangile Bigot in 1861. Later the name was changed. The species has a Palaearctic distribution, very infrequent on the African continent and less common in Western Europe. Nevertheless, in Spain it has been found in the provinces of Alicante, Balearic Islands, Barcelona, Caceres, Castellón de la Plana, Ciudad Real, Cordoba, Girona, Jaén, Salamanca, and Segovia. Now I suppose that Pontevedra has to be added to the list. It’s important to keep in mind that Spain has 58 known native mosquito species, with the addition of two invasives: the yellow fever mosquito (Aedes aegypti) which was present from 1700 to 1939 and since then has disappeared, and the tiger mosquito (Aedes albopictus) which arrived in 2004 and has become established.

What will you do with the captured individual?

We have incorporated it into the entomological collection of the Mosqutio Control service of the Baix Llobregat County Council. In the observation map [of the Mosquito Alert platform] you can see the original photo of the mosquito found in Galicia.

There are studies that say that this species may also be able to transmit diseases such as Zika, Dengue and Chikungunya. Is this something to worry about?

It is true that in Africa the mosqutio has been associateed with some outbreaks of yellow fever, and in the laboratory it has been shown to have the capacity for transmitting this and other diseases. However, the real risk depends on other things such as the abundance of the mosquitos, the frequency of contact with people, and the presence of infected individuals. It is not a species which is found indoors since it does not seem to have adapted to breed in containers in urban areas like the tiger mosquito. Normally we don’t find Aedes vittatus very often, and when we do it is during short periods of the year in forested areas, so contact with people is limited. In this sense it is very different from the tiger mosquito and yellow fever mosqutio, which tend to be very abundant and living near large concentrations of people during the warmest times of the year. For these reasons it is not worth worrying too much about Aedes vittatus.

Some recent studies consider citizen science to be a great ally for the study of biodiversity. Do you think that it can also improve knowledge about the biodiversity of mosquitos?

Yes, obviously it can. Citizen science has a high potential since it it allows such specific tools as this one to be very useful, combining a community of motivated volunteers with a team of highly qualified entomologists. Our platform is geared towards detecting two specific mosquito species, but this case has shown that we also have the capacity to detect rare species. In fact, there are other citizen science projects studying mosqutio diversity, for example the german platform MuckenAtlas. However, that project requires the volunteers to physically send the found mosquitos in order to identify them in the laboratory. Our case has been quite relevant because we have detected a rare species based on only a photograph, something that requires a lot of experience.

Reference:

Roger Eritja, Marga Rubido-Bará, Sarah Delacour-Estrella, Mikel Bengoa, Ignacio Ruiz-Arrondo, & Comunidad Mosquito Alert (2018). Ciencia ciudadana y biodiversidad: primera cita de Aedes (Fredwardsius) vittatus (Bigot, 1861) (Diptera: Culicidae) en Galicia, mediante el proyecto Mosquito Alert. Anales de Biología, 40: 41-45.

Photo of Aedes vittatus: El desinsectador – www.desinsectador.com

The yellow fever mosquito is found in the Canary Islands

The news of this first sighting in the Caranry Islands was reported by region’s Ministry of Health in an official statement issued Tuesday December 12, after a several of the mosquitos were found on the island of Fuerteventura. As reported by the Ministry, this was considered an isolated sighting since at the moment there is no evidence that the species has become established.

Mosquito de la fiebre amarilla. Roger Eritja Copyright

Yellow Fever mosquito (Aedes aegypti). Roger Eritja Copyright

 

The yellow fever mosquito is very similar to the tiger mosquito and is capable of transmitting diseases such as Zika, Dengue and Chikungunya. The Canarian Government has already begun to place more traps and search for the mosquito’s breeding sites in order to eradicate it as soon as possible and prevent its proliferation. Since only a few individuals were found, the situation could be in a very initial, reversible phase, and more results are necessary in order to arrive at a final assessment. The Canary Archipelago is located in the subtropical zone, so unlike on the Iberian Peninsula mosquitos can be found throughout the year.

Given the current risk of the yellow fever mosquito (Aedes aegypti) being introduced into Spain – a worry of the Canary Islands government, which years ago established a local program for the detection of the species – the Mosquito Alert citizen science project coordinated by CREAF, CEAB-CSIC and ICREA and supported by the Obra Social la Caixa, included the yellow fever mosquito in its monitoring platform (together with the tiger mosquito) in January 2016.

Comparative of the tiger mosquito and the Yellow Fever mosquito. Pictures: J.Luis Ordóñez (CC BY NC)

 

The current state of alert has obliged scientists to regularly inform the public about about the possible arrival of the yellow fever mosquito, while simultaneously tracking and eliminating the tiger mosquito. Citizen participation in mosquito tracking using the Mosquito Alert app and the management platform, which uses expert validation and new digital and mobile techologies, has already proven to be a successful system for the detection and control of the tiger mosquito.  Mosquito Alert is open to all citizens and types of users, and its Canary Island participants are already indirectly supporting the mosquito control effort. This government-citizen collaboration could be bolstered if more volunteers send photographs through the app.

A brief background on the yellow fever mosquito

Entomologist Roger Eritja of the Baix Llobregat Mosquito Control Service of explains that “the appearance of Aedes aegypti is actually a return.” These mosquitoes were already present in the Mediterranean between 1700 and 1950, when they caused tens of thousands of deaths with epidemics of yellow fever and Dengue, beginning at ports. At that time ports were the crossroads of ships from the Americas laden with goods, but also water with mosquito eggs. Also arriving at the ports were sick passengers and mosquitos infected with the different viruses.  At that time the epidemics were so severe that sometimes the docking of ships with sick persons onboard was prohibitted, and were even repulsed with canon attacks.

Finally, in the second half of the 20th centry the yellow fever mosquito disappeared from Europe, though it is not well understood why.  “It may be because it was not able to hibernate,” says Eritja. Eritja also highlights a very important fact: the last sighting of the yellow fever mosquito in Spain was made in 1939 by the ecologist Ramon Margalef. But if the disease came to Europe from America, does that mean that it is also an endemic disease there? In fact, yellow fever was not present in the Americas at the moment that colonial explorers arrived in the 15th century, as attested by historical documents. The first yellow fever epidemic was not described until the mid-seventeenth century in the Yucatan region.

Johann Moritz Rugendas [Public domain, Public domain or CC BY-SA 4.0

Johann Moritz Rugendas CC BY-SA 4.0

 

It is believed that both the yellow fever mosquito and associated virus are of African origin and were brought to the New World through globalization, in this case through the infamous slave trade. The slave trade of West Africa emerged as a way to provide manpower for Central American plantations, but in addition to people it also brought diseases, mosquitoes and viruses from Africa to America. So, with the understanding that trade has played a key role in the dispersal of these two mosquitos – the tiger mosquito and yellow fever mosquito – it is horrible to think that human trafficing was in fact the precise cause.

This post was written in collaboration with Roger Eritja.

Spanish tv broadcasts “REPOR” program about the fight against mosquitos

Last Sunday 2nd July the “REPOR” program from Spanish television broadcast a documentary about the problem that are causing mosquitoes in the country. From affected neighbours to pest control professionals to new technologies like the Mosquito Alert app, reporters travelled miles to find out the keys and win the “Mosquito war”.

The Mosquito Alert app.

 

Mosquitoes are insects that are making life impossible for us. The neighbors from Guadalmar (Malaga) created the platform “Stop Mosquitos”, as they no longer know what steps to take to get rid of these annoying insects. Until a few years ago the problem was only by the common mosquito, but now the tiger mosquito has also been added.

The entomologists of the Baix Llobregat Mosquito Control Service, Dr. Carles Aranda and Dr. Roger Eritja, explain why some people are bitten by mosquitoes more than others. In addition, they teach us the characteristics to recognise tiger mosquitoes and yellow fever and what are the risks of having these species in Europe and Spain.

Carles Aranda y Roger Eritja. Servei de Control de Mosquits del Baix Llobregat.

Carles Aranda and Roger Eritja. Servei de Control de Mosquits del Baix Llobregat.

 

Cemeteries are one of the places where more breeding sites are concentrated, according to the ctl. Sanidad ambiental company. In some cases are beginning to use drones to detect the largest breeding sites in spaces such as urban parks or orchards. This is explained by the entomologist Dr. Rubén Bueno, from the Lokímica company, in collaboration with the Ccty of Murcia.

Ruben Bueno (Lokímica) y Eduardo González (Servicio Municipal de Salud Ayto. Murcia)

Rubén Bueno (Lokímica) and Eduardo González (Health Service of Murcia city council)

 

And the latest news is to control the mosquito with the mobile. Dr. Frederic Bartumeus shows the Mosquito Alert app, designed for citizens to collaborate with scientists and professionals. This app is used by the Barcelona Public Health Agency (ASPB) in its tiger mosquito control programs in the city of Barcelona.

Marina Torres y Frederic Bartumeus del equipo Mosquito Alert.

Marina Torres and Frederic Bartumeus, Mosquito Alert team.

 

Tomás Montalvo y técnicos de la ASPB.

Tomás Montalvo and ASPB team.

 

See the full documentary (only available in Spanish):

 

Link to the tv program

Aedes aegypti, the yellow fever mosquito

Aedes aegypti is the mosquito known as the yellow fever mosquito. Like the tiger mosquito (Aedes albopictus), it belongs to the Aedes genus, and these two are closely related. Entomologists are always prepared to remind us that in fact, both belong to an Aedes sub-genus called Stegomyia (derived from ancient Greek stegos: under the roof, and myria: fly).

aedes aegypti_mark yokoyama_(CC BY-NC-ND 2.0)_02

Yellow fever mosquito (Aedes aegypti). Credit: Mark Yokoyama (CC BY-NC-ND 2.0)

 

The yellow fever mosquito has white scales in the shape of a lyre on the thorax

Adult Aedes aegypti are small and dark brown colored with white lines covering the body and legs. Their appearance is similar to the tiger mosquito (Aedes albopictus) but are in fact a bit different. They are differentiated from other species by 4 lines of white scales in the shape of a lyre on the dorsal side of the thorax.

The following images serve to compare the thorax of Aedes aegypti (four lines in the shape of a lyre) with that of Aedes albopictus (a single white line on the thorax).

The behavior of the yellow fever mosquito is similar to that of the tiger mosquito

Izquierda: Ae.aegypti. Derecha: Ae.albopictus. Autor: Vincent Robert (CC BY 2.0)

Thoraxes of Aedes aegypti (left) and Aedes albopictus (right). Credit: incent Robert (CC BY 2.0)

The yellow fever mosquito generally bites during the day but may also bite at night. It has a high preference for people, even greater than the tiger mosquito, but it can also bite other mammals, usually domestic animals. Like other mosquitos, only the females bite, needing blood to develop eggs.

Its period of activity depends on location. For instance, in subtropical areas it is active during most of the year. In (mainland) Spain it is not known what its period of activity would be since no populations have been detected

Originally, the yellow fever mosquito (Aedes aegypti) lived in forested environments and used holes in trees with accumulated rainwater to breed. Just like its cousin the tiger mosquito, over the years it has adapted to urban areas and breeds in any microenvironment with stagnant water such as water drains, containers, or tires.

It is a vector of diseases

The yellow fever mosquito (Aedes aegypti) can transmit diseases between people or between animals and people, for this reason it is called a disease “vector.” Most of the diseases transmitted by this mosquito are caused by viruses. The most noteworthy of these are yellow fever, the dengue virus, the chikungunya virus, and the zika virus.

Where is Aedes aegypti found?

A species of African origin, its distribution has always been associated with human movement and trade. From Africa, it was introduced into the Americas around the XVI-XVII centuries with the slave trade. The trade of goods from the New World introduced the species into Europe numerous times, becoming established throughout the Mediterranean, and between 1700 and 1850 it caused severe epidemics of yellow fever and dengue, causing hundreds of thousands of deaths.

Distribución del mosquito de la fiebre amarilla (Aedes aegypti). Fuente: ECDC

Distribution of the yellow fever mosquito (Aedes aegypti) in Europe. Source: ECDC

Later, the mosquito somewhat spontaneously disappeared, but in the last 25 years its distribution has again increased due to globalization. It is now found in Africa and tropical or subtropical countries, especially in Northern Brazil and Southeast Asia including India. It is also found in the Southeast United States and in Northern Australia.

Unlike the tiger mosquito (Aedes albopictus), the yellow fever mosquito (Aedes aegypti) is not capable of entering into diapause to withstand winter while in the egg phase. This limits its ability to colonize northern temperate areas.

However, it could become established in European regions with a humid subtropical climate (parts of Mediterranean and Black Sea countries) such as the Sochi region (Black Sea coast), where it became established in 2001. In 2005 it also became established on the island of Madeira, where it has already caused a dengue epidemic, becoming a major source of worry for Spain and the Canary Islands. Recently, the Canarian Government has announced the finding of some individuals of yellow fever mosquito at the Fuerteventura island, according to the Entomological Surveillance System actions.

 

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