Interference in the environment will cause ne

Publicação: 10 de January de 2013

Interferência no meio ambiente vai causar novas doenças, aponta especialista

The number of emerging diseases quadrupled during the last half century, largely due to human advancement into wild areas, especially in tropical regions

Diseases have always departed from the forests and fauna and arrived in human populations: the plague and malaria are two examples. This observation was made by Jim Robbins, in the New York Times and Folha de Sao Paulo.

Robbins says that according to scholars, the number of emerging diseases has quadrupled in the last half century, largely due to humans advancing into wild areas, especially in tropical regions. They argue that air travel and trafficking of wild animals increases the potential for serious outbreaks of disease in large population centers.

In order to discuss the impact of human interference on the environment and what can be done to diminish any problems, the Brazilian Society of Tropical Medicine (SBMT) invited Dr. Carlos Brisola, PhD in Entomology from the Federal University of Paraná (UFPR), who works in the field of Parasitology, with an emphasis on Entomology and Malacology of Parasites and Vectors, and is a professor at the Federal University of Santa Catarina (UFSC), to discuss this topic.

SBMT: Dr. Carlos, can we consider that the disturbance of an ecosystem can cause diseases? What would be considered a disturbance? How can mankind minimize this situation?
CB: Humans can disrupt the ecosystem in several ways, through deforestation, climate change and even by just going into natural environments or introducing new animals, such as domestic ones. There are several examples of this. Studies on forest residues in the north of São Paulo state found a concentration of vectors and reservoirs of Trypanosoma cruzi. By modifying the forest, humans can substitute the Leishmania species and its vectors. In better preserved forests, Psychodopygus sandflies transmit Leishmania braziliensis; with modification, this is transmitted by Nyssomyia whitmani. On the edge of the forest and in houses the transmission by the latter and by Nyssomyia intermedia and Nyssomyia neivai occurs, and if the modification is more acute there will probably be a proliferation of Lutzomyia longipalpis and transmission of Leishmania chagasi.
Plasmodia of monkeys can be transmitted to humans, which is even simpler due to the ease with which Anophles cruzii moves between the canopy of trees and the ground; this mosquito, although well adapted to primary forests, can leave the forest and bite at various times, which can increase the risk to humans. Numerous cases of human malaria are occurring in Southeast Asia, caused by Plasmodium knowlesi, a new species associated with monkeys. With the data available, it is difficult to recommend a single measure to minimize interference and reduce the risk of transmission of pathogens. The key is to analyze the potential for disease transmission and to understand the biology of vectors and reservoirs. One obvious measure to avoid problems, for example, is not to build near wetlands or other areas that are breeding grounds for midges (Ceratopogonidae), especially if nothing is known about the fauna of these insects in the area. However, with only half a dozen specialists inBrazil, to whom little attention is paid, there are likely to be many problems, as has occurred on theisland ofSanta Catarina, where Air Base residents and residents of several neighborhoods are being bitten.

SBMT: Doctor, a recent study by the International Institute of Animal Breeding Research found that more than two million people per year die from diseases transmitted to humans by animals. Why does this occur? What can be done to reverse this situation? What animals can be considered most dangerous because they are potential transmitters?
CB: There are hundreds of viruses, bacteria and protozoa, some hardly known about, which can be transmitted to domestic animals and humans, either through arthropod vectors or by rodent feces and urine. Jared Diamond suggests, in the book “Guns, Germs and Steel” that their long coexistence with livestock increased the immunity of the inhabitants of Eurasia, while the other continents suffered more when they first came into contact with these germs. However, in several places, environmental modifications may place pathogens in contact with humans, animals of various species and potential vectors. For example, the introduction of West Nile Virus (WNV) in theUnited States has caused serious health problems, and various wild animals are reservoirs. This has highlighted the need for training and for studies in several related areas. It is only possible to think about reversing this situation after much study, which includes training and plenty of resources.

The illusion that infectious diseases would become insignificant with the production of antibiotics was as false as that of “a world without flies” after the discovery of DDT’s effects. You cannot say which animals are more or less dangerous, because each infectious agent has its peculiarities.

SBMT: In your understanding, are tropical countries more prone to this type of problem?
CB: Tropical countries have a greater variety of environments, a greater biodiversity and more precarious living conditions. For example, in a reserve on the island of Santa Catarina, only studying phytotelmates (bamboos, bromeliads and tree holes) and collecting mosquitoes during the day, we found 56 species of mosquitoes (Reis et al., 2010), whereas in the whole of Canada, which is larger than Brazil, there are 74 species. Which of the 56 species may become dangerous? It is worth remembering, however, that there are many zoonoses in cold and temperate locations and Pavlovsky proposed in the first half of the twentieth century the theory of natural nidality of diseases based initially on the fact he had found encephalitis in desert regions of Central Asia.

An important factor that heightens the risk of new diseases in tropical regions is the increase in population and the demand for better living conditions, which are still precarious for the majority. This is inevitable and cannot be criticized, since humanity cannot continue to be divided between those who have homes with air conditioning, electric showers and cars, and those living with cows in houses and sewage running through the backyard.

SBMT: What might happen if humans continue to interfere with the environment? Is there a possibility of new diseases emerging?
CB: Human interference in the environment, often carried out ??on the basis of “let’s go ahead, it is those who come later that will suffer”, is certainly still going to cause many new diseases. It is scary when a large portion of supposedly intelligent and well informed people, such as the United States, thinks that global warming does not exist and that the burning of oil for enormous cars and to keep houses warm has nothing to do with it. We should interfere with caution, because prevention is better than cure.

In my classes I often quote John VI of Portugal: “If you do not know what to do, don’t do anything”. Many forms of life, each one trying to survive and multiply, surround us and we can no longer be “sorcerer’s apprentices”. We must try to predict the next aggressors, through much study, and work out what can be done. I am sure that the billions spent to send a jeep to Mars would be far more useful here on our badly treated planet. H. E. Evans says, at the beginning of his book on insects (“Life on a little known planet”): “man goes to the moon and the stars, but does not know what is in his own backyard”.

SBMT: Dr. Carlos, is the work developed by Project Predict, funded by USAID, which takes samples of blood, saliva and other species of wild animals at high risk, and aims to create an archive of viruses to facilitate quick identification of those that could infect humans, the best action to take? Could this prevent future diseases?

CB: It’s a very interesting initiative, and must be accompanied by many ecological studies of various environments. I’m not sure what “high risk” species would be because, as the distinguished entomologist (and friend) Pedro Linardi says, “an animal that is stupid now, could get smart next month.”

SBMT: Is there a way to prevent against possible epidemics? What can be done?
CB: I hope the above initiative is accompanied by training of researchers and support for those who are already struggling to produce knowledge. With poor wages, precarious infrastructure (try asking for a car to go to the countryside or for a repair at a university or research institute), support from agencies distributed randomly and discontinuously, it is difficult to prevent the emergence of new epidemics, which will certainly come. Prudence when it comes to interference in the environment is certainly also very important.