Contáctanos

Ecology

The Mosquito Team

While some insects are essential to the survival of humans on our planet, others are covert enemies that have done more to decimate the population than any other factor. Under the leadership of Dr. José R. Loaiza, an effort is being made in Panama to consolidate the legacy of more than one hundred years of research to create a group of scientists focused solely on preventing tropical diseases, particularly those transmitted by insects.

Text and Photos: Javier A. Pinzón

 

While some insects are essential to the survival of humans on our planet, others are covert enemies that have done more to decimate human populations than any other factor. Given that Panama has always been a global meeting point, the history of the country is a perfect example of what this insect can do. The European arrival in the Americas and the slave trade from Africa brought along the dreaded mosquito, which killed a significant number of people in this hemisphere, just as it had done, and continues to do, on other continents. The Aedes aegypti, which transmits yellow fever and dengue, was one of the causes of the failure of French efforts to build the Panama Canal in the 19th century.

As early as 1881, Cuban epidemiologist Carlos Juan Finlay suggested that these diseases were transmitted by mosquitoes. Nonetheless, his findings were not confirmed until twenty years later, when army doctor William C. Gorgas, upon being appointed Chief Sanitary Office in Havana, decided to test Finlay’s theory; he achieved extraordinary results in controlling these diseases on the island.

It was precisely this success that led to Dr. Gorgas being invited to Panama in 1904 to help eradicate these diseases by controlling the mosquitoes that transmit them. The work was exacting, but it left a healthy environment in which the United States was able to complete the Panama Canal. From that time on, Panama became ground zero for the study of tropical diseases and their vectors, thanks to the efforts of scientists from the Gorgas Memorial Laboratory.

Today, 114 years later, the battle against mosquitoes, and research into the diseases they transmit, continues. The Ministry of Science, Technology, and Innovation of Panama (SENACYT) recently gave Dr. José R. Loaiza, a researcher from the Institute of Scientific Research and High Technology Services (INDICASAT), a grant of nearly half a million dollars to build an insectarium and  carry out experimental research to test new methods of controlling insect vectors, such as the use of bacteria and fungi. It is a long-term vision that seeks to establish a multi-disciplinary research group called the Mosquito Team, consisting of young Panamanian and international scientists; it is supported by the Smithsonian Institute of Tropical Research and the University of Panama.

Fighting on various fronts, the Mosquito Team is collecting information on how the Wolbachia bacteria can be used to mitigate transmission via the Aedes aegypti vector. The bacteria occur naturally in some insects, but when injected into mosquitoes that transmit dengue, the virus no longer develops normally.

The aim of the Mosquito Team is to understand the ecological processes that have an impact on how the insect vector affects populations, with the end goal of creating effective disease-prevention programs. For example, it might be possible to prevent annual dengue epidemics if we knew the best time to attack the eggs and kill the mosquito larvae. To date, notes Loaiza, the strategy used when someone dies from dengue is to fumigate with synthetic insecticides in an attempt to kill the infected female mosquitoes that might continue to transmit the disease, but this cannot prevent the next outbreak.

If we add up all the deaths of the First and Second World Wars and other conflicts, they do not amount to even a third of the deaths caused by malaria and dengue, which is why the mosquito is considered one of the most dangerous animals in the world. Furthermore, explains Loaiza, Aedes aegypti is so well adapted to life with humans that it is practically a domestic animal: you may not have cats or dogs at home, but you may well have Aedes mosquitoes.

Panama is home to 260 of the world’s 3,600 known mosquito species. In addition to Aedes and Anopheles, the forests contain other mosquitoes that can transmit pathogens and viruses among wild animals, such as jungle yellow fever and Mayaro in monkeys.

Should an outbreak of any of these diseases occur in the forest, they could infect humans, making it necessary to study animals as well as people. Deforestation alters the equilibrium of the forests and induces mosquitoes that feed on wild animals to seek out human blood, thereby creating another avenue for the transmission of new diseases. Many viruses that lived a natural cycle in relatively untouched forests have made an ecological leap to being transmitted in deforested rural areas; these viruses include yellow fever, Oropouche, Mayaro, Venezuelan equine encephalitis, and West Nile fever.

Loaiza tells us that these harmful mosquitoes, which have adapted to life amongst us, are not native to the Americas.

Mosquito Team : Dr.  José R. Loaiza,  dra. Kelly L. Bennett, Madeleine Ducasa, José Rovira,  Jaime Cerro y Alejandro Almanza.

 

The first species to reach the Americas was Aedes aegypti, which got a head start on this evolutionary development when it spread beyond Africa in the 17th century by laying its eggs in water barrels on slave ships. It then spread to Asia and Europe.

A new invader has been sweeping across the planet since 1980: Aedes albopictus, or the Asian tiger mosquito, which began to spread via the export of used tires from Japan to the rest of the world. Both mosquitoes have been more successful than certain other species in expanding beyond their original ranges of distribution because their eggs can survive out of water. Aedes aegypti has wreaked the most havoc, which is why it is the most studied of the mosquitoes. However, Aedes albopictus has already sparked nearly as much interest. Other species, such as Aedes japonicus, are beginning to spread around the world as well.

How could they have colonized the Americas? Aedes aegypti and Aedes albopictus are urban mosquitoes found where human populations are concentrated. These mosquitoes use the roofs of our houses to protect themselves from the sun, since they dehydrate easily, and they lay their eggs in pools of water that collect outside; they feed on our blood and we help spread them by transporting their eggs in used tires.

Aedes aegypti has become adapted to living easily among us, since it needs to fly very little to meet its basic needs. When these mosquitoes lived in the forest and laid their eggs in the hollows of trees, they had to compete with other species. Now that they are urbanized, they take advantage of the clean water we provide, and they have no competition or natural predators.

But there is something odd about these two species of Aedes. Aedes aegypti needs a minimum number of people per house in order establish a foothold, since it feeds only on human blood. It cannot flourish in sparsely populated rural areas. Aedes albopictus, on the other hand, feeds on both human and animal blood, so it is not limited by the number of humans at hand.

Regardless, we need to look beyond Aedes aegypti and Aedes albopictus. The Loaiza Mosquito Team’s scope of study covers all the arthropods that transmit diseases to humans, including ticks, bedbugs, and sand fleas.

This group, which comprises around 5% of the class Insecta, is one of the best known and most studied owing to its impact on public health.

Loaiza emphasizes that we humans are now in a race against mosquitoes. In order to win, we need the help of not only entomologists, but also social scientists,

IT experts, epidemiologists, sociologists, anthropologists, systems engineers, statisticians, and more. We need to fight this battle using a multi-disciplinary, intersectoral approach that allows us to better understand the factors that facilitate the emergence of diseases. The work being done by the Mosquito Team in Panama is just the beginning. There remains much to study and, more importantly, people must be made aware of the problem and educated on how to help prevent fresh outbreaks of pathogens and diseases in Panama.

But there is something odd about these two species of Aedes. Aedes aegypti needs a minimum number of people per house in order establish a foothold, since it feeds only on human blood. It cannot flourish in sparsely populated rural areas. Aedes albopictus, on the other hand, feeds on both human and animal blood, so it is not limited by the number of humans at hand.

Regardless, we need to look beyond Aedes aegypti and Aedes albopictus. The Loaiza Mosquito Team’s scope of study covers all the arthropods that transmit diseases to humans, including ticks, bedbugs, and sand fleas.

This group, which comprises around 5% of the class Insecta, is one of the best known and most studied owing to its impact on public health.

Loaiza emphasizes that we humans are now in a race against mosquitoes. In order to win, we need the help of not only entomologists, but also social scientists,

IT experts, epidemiologists, sociologists, anthropologists, systems engineers, statisticians, and more. We need to fight this battle using a multi-disciplinary, intersectoral approach that allows us to better understand the factors that facilitate the emergence of diseases. The work being done by the Mosquito Team in Panama is just the beginning. There remains much to study and, more importantly, people must be made aware of the problem and educated on how to help prevent fresh outbreaks of pathogens and diseases in Panama.