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Some ten years ago nobody could imagine that the Republic of Panama will be the most attractive in the region and will outperform many developed countries in terms of economic factors of development. After the transfer of the Panama Canal into their own country in 1999, the republic gained access to the funds received from the exploitation of channel counting billions of dollars. The country's population is a little more than three million people, so in a few years this country changed dramatically, becoming an oasis of Latin America. Today, Panama is compared with Hong Kong and the UAE, over 100 years the country uses one of the most stable currencies in the world, thereby protecting the Panama against inflation, currency crises and other problems. Over 80 countries have representations of their banks in Panama, favorable fiscal legislation and economic and political stability attract capital and investment in the country.
Study of clinical course of the epidemic process in the tropical regions of the globe is of practical importance and considerable theoretical interest. Specific climatic conditions, variety of flora and fauna, the socio-economic conditions have a significant influence on the formation of noso-complexes and noso-areas, the survival of pathogens in the environment, the spread of blood-sucking vectors of pathogens, conditions of transfer of pathogens from animals to humans, the course of human diseases and features of their prevention.
Wide-spread tropical diseases of Panama
Tropical diseases are a group of diseases occurring exclusively or predominantly in the equatorial, subequatorial and tropical zones. They include first of all infectious and parasitic diseases (mainly vector-borne diseases): virus, such as yellow fever; bacterial, for example pseudocholera; rickettsiosis, for example tsutsugamushi; spirochetal, for example, yaws; fungal, for example coccidiomycosis; caused by protozoa (malaria, leishmaniasis, sleeping sickness, etc.), helminthiasis (schistosomiasis, filariasis, etc.). They are characterized by mass destruction, the increased probability of simultaneous infection by several types of pathogens. The group of tropical diseases also includes diseases that are directly related to the influence of hot climate (e.g., dermatitis), caused by lack of food proteins and vitamins (such as kwashiorkor, beriberi, sprue), genetic abnormalities of blood (such as sickle cell anemia), destruction poisonous snakes, spiders, fish, etc. (Cooperation and progress on tropical disease in Panama, 2004).
The high incidence of tropical diseases in developing countries is due to both natural and socio-economic factors - the hangover of the colonial regime. Low level of sanitary culture among the population and the development of medical services, poor nutrition, and peculiarities of lifestyle determine clinical course of many diseases. Tropical diseases among local residents often develop on the background of protein deficiency, hypovitaminosis, chronic metabolic disorders of parasitic origin and anemia, the cause-effect relationship between them is often unclear. The characteristic of tropical hot and humid climate promotes rapid multiplication of pathogens of infectious tropical diseases, posing a potential threat to public health other countries.
High temperatures, a considerable humidity, the abundance of water, especially after the rainy season, favor a mass hatching of blood-sucking arthropods - vectors of diseases. Some arthropods are specific carriers of agents of one or two diseases, while others are involved in the dissemination of a dozen different diseases. Widely distributed in various parts of torrid zone mosquitoes play an important role in the spread of encephalitis, yellow fever and dengue fever, filariasis and other diseases; mosquitoes transmit pathogens of leishmaniasis, fever pappatachi, bartonellosis and so on (Read, 1978).
The development and accumulation of thermophilous pathogens occurs at a sufficiently high temperature. Temperature and humidity of the environment in which breeding is possible and the passage of certain stages of development of the pathogen in the body of a carrier have a great influence on the seasonality of tropical vector-borne diseases. In tropical areas, where arthropod vectors are active throughout the year, vector-borne diseases do not always show a distinct seasonality, and incidence during the year in some cases lasts about the same level.
In Panama, where under the influence of monsoon the climate is divided into wet and dry seasons, the maximum number of disease cases, the pathogens of which are carried by mosquitoes, usually occurs during the wet season or soon thereafter. In some cases, this periodicity is associated with the bird - mosquito cycle, and the centers of maximum number of disease cases are situated in areas where colonies have a large number of susceptible birds. In contrast, the viruses carried by ticks, in the same climatic regions cause the maximum number of diseases in the dry season (Read, 1978).
A significant proportion of natural foci diseases in tropical regions are made by arbovirus infection. Arbovirus infections are characterized by the fact that their agents - human and animal viruses - multiply in the body of blood-sucking arthropods and are transmitted while blood-sucking through saliva. All of arbovirus diseases are natural foci diseases, and their distribution is determined by the large number of natural factors, the presence of specific vectors, susceptible vertebrate, temperature, humidity and other factors. The vast majority of arbovirus diseases carried by mosquitoes, is of tropical origin. This accounts for their increased demand to temperature conditions.
For example, yellow fever virus in the mosquito Aedes aegypti at the temperature of 37Â°C reaches the infective dose in four days, at 36Â°C - in six days; at 25Â°C - in eight days; at 23Â°C - in 11 days; at 21Â°C - in 18 days; and at 18Â°C virus in mosquitoes is not detected even after 30 days. Similar results with respect to the virus were obtained in experiments with Haemagogus spegazzinii. Temperature is undoubtedly an important factor limiting the range of yellow fever, as carriers of the virus are spread much wider than the virus itself (Read, 1978). Within the torrid zone there are the temperature conditions for year-round circulation of different viruses. This corresponds to approximately the average isotherm of 16Â°C for the coldest climates.
Natural focal disease exists in two phases, the relationship of which varies widely across time and space: first is the circulation of the pathogen in the biotic components of natural foci; the second is the transition from nature to human beings and the possible spread of the disease in the susceptible group. An example of these phases is the epidemiology of yellow fever in Panama.
The most often infections in natural foci hit loggers, workers paving roads in the forest, and the soldiers. The virus obtained by the human in the future is distributed among the population of settlements by antropophilic mosquito Aedes aegypti. In these types of foci a sick man is the only source of the pathogen, that is, here yellow fever is a typical anthroponosis. Thus, yellow fever anthroponotic foci of settlements are the secondary foci. However, in epidemiological terms these centers have the greatest value. Infection of humans with yellow fever occurs in most cases in settlements, and only a few diseases occur as a result of infection in the jungle (Zetek, 1916).
Epidemics in the Panama Canal Zone: historical significance
In the 20th century it is even difficult to imagine the physical and mental suffering, which were brought o the population by epidemic diseases in the past. In medieval Europe they were the cause of death of every fourth person. Today, the epidemics in general are not so widespread and deadly, like centuries ago, and yet they continue to occur as a result of violations of balance between human populations, conditions of their existence and the presence of infectious agents.
The Panama Canal Construction
Panama Canal shortened the path from the Pacific to the Atlantic Ocean to nine hours. It connects the Gulf of Panama Pacific Ocean with the Caribbean Sea and the Atlantic Ocean. This reduces many of the sea routes and avoids the long and dangerous journey across the Drake Passage past Cape Horn. For example, the path from New York to San Francisco by this route would have been more than 22 thousand kilometers, while through the channel it is only 9.5 thousand. The Panama Canal is of vital strategic importance: it serves the 5% of all ocean shipments in the world. However, the construction of the Panama Canal is associated with waves of epidemics of tropical diseases, which greatly influenced the modern geopolitical space.
January 1, 1880, the ceremony of laying the first stone was held at the mouth of the Rio Grande. Maximum number of workers involved in construction amounted to 19,000 people. The work was done with a grand sweep, but in 1885 only one tenth of the target was completed. The main reasons for this were technical difficulties uncalculated by the project and the tropical climate. The closeness of malarial swamps caused outbreaks of disease among workers who lived in unsanitary conditions. Hundreds of people were also dying from yellow fever. Lack of timely medical care and necessary medicines led to huge casualties among builders (McCullough, 1978).
Tropical diseases and hardships claimed 22,000 lives of workers and engineers. The French quickly ran out of money. The company went bankrupt, and eight hundred thousand shareholders around the world lost their money. Noticeable, the idea of building a canal later served as fertile ground for the establishment of financial pyramids. The same models subsequently served basis for the biggest scams, and the word "Panama" became synonymous with big fraud (Parker, 2009).
Later, Theodore Roosevelt believed the construction of the canal was his main foreign policy achievement. In 1901, the U.S. signed a treaty with Great Britain about the exclusive right to build the canal, and in 1903 Theodore Roosevelt supported the separation of Panama from Colombia. In gratitude, the U.S. obtained land for construction, and the process was assigned to the War Department (McCullough, 1978).
In the 18-19th centuries among the epidemic diseases of the Western Hemisphere yellow fever occupied a prominent place in the U.S., as well as in Central America and the Caribbean. Doctors, assuming that the disease was transmitted from man to man, required isolation of the ill to combat the epidemic. Those who have linked the origin of the disease with air pollution insisted on sanitary measures (Parker, 2009).
In 1903 the works resumed and in 1905 Americans were exposed to yellow fever. But this time, the construction management did not allow people to die by the hundreds. They held researches, invited the best doctors and biologists of the time, who found that the perpetrators of the epidemic were not poisonous miasma of swamps, as previously thought, but quite real insects - mosquitoes. Back in 1881 the Cuban physician K. Finlay suggested that mosquitoes Aëdes aegypti were carriers of the previously discovered fever virus (Viscerophilus tropicus, akin to some viruses of encephalitis and dengue fever) (Zetek, 1916). Research was accelerated, as it often happens, by a short Spanish-American War in 1898, when the U.S. fought against the Spanish, supporting the insurgents of Cuba and Puerto Rico. The war ended quickly in favor of the United States, but among the American soldiers a fever burst out, which they called "Yellow Jack".
Evidence of Finlay's theory was provided in 1905 by Yellow Fever Commission headed by W. Reed that worked in Havana. Implementation of mosquito fighting programs developed by the Yellow Fever Commission in the next few years contributed not only to significant reduction of morbidity in Havana, but the completion of the Panama Canal, which nearly stopped due to yellow fever and malaria. To avoid new epidemics, it was decided to kill all the mosquitoes-transmitters of the disease along the way, and a kind of a "campaign against the mosquitoes" was arranged. It involved 1500 people, who dug 80 miles of ditches to drain the swamps, cut down 30 square kilometers of bush, and spattered 700 tons of kerosene. 190,000 liters of kerosene per month were spent on the treatment of housing, as well as 300 tons of sulfur, 1,200 receptacles for smoking and a countless number of brooms (Zetek, 1916).
Unprecedented for the time sanitary measures were taken, and within a few months, yellow death receded. Due to these measures, yellow fever was allegedly completely destroyed in Cuba and in Panama, where it previously raged mercilessly. There is a persistent opinion that without a victory over the disease the construction of the Panama Canal would be impossible.
In 1937 M. Tayler, a doctor from South Africa, developed an effective vaccine against yellow fever, more than 28 million doses of which were produced for tropical countries by Rockefeller Foundation from 1940 to 1947. Despite this, the yellow fever has not been finally eradicated yet. Panama itself, as part of Central America, is considered safe from yellow fever, but the areas south of Panama City, close to Colombia, are at risk (Parker, 2009).
The very construction of the Panama Canal took 10 years and 400 million dollars. The works involved 70,000 workers, of whom more than five thousand were killed. The first ship passed through the channel in 1914. The U.S. controlled the canal until the end of the 20th century, after which he was transferred to the Government of Panama. At the end of the 20th century over 4% of all world trade flows proceeded through this cargo artery. In 1998 alone, more than 13 000 ships passed through the channel and the net income amounted to about half a billion dollars (Parker, 2009).
Nevertheless, contrary to popular misconception, the Panama Canal had never been too profitable to the U.S.: the cost of its operation and maintenance of the Panamanian treasury were considerable. However, from the very beginning the U.S. Government relied not only on the economy, but on geopolitics too. Suffice it to say that until the end of 1990s in the Canal Zone was located the largest American military infrastructure outside the United States - eight bases with 4272 building, occupying an area of over 31,000 hectares. And since 1941 the headquarters of Southern Command of U.S. Army was placed there, which was holding the entire Latin American continent at gunpoint.
Epidemics of Neglected Tropical Diseases and new infections
Neglected tropical diseases is a group of infectious and parasitic tropical diseases, primarily affecting the poor and marginalized communities in the regions of Asia, Africa and Latin America. The main list of the World Health Organization includes 13 diseases, of which seven are caused by parasitic worms, three - by protozoal parasites and three more - by bacteria. These are the diseases with the highest morbidity rates. Twenty more diseases also related to the neglected ones are caused by fungi, viruses and parasites (filariasis, dracunculiasis, balantidiasis, Buruli ulcer, leprosy, dengue fever, scabies, myiasis, sarcopsyllosis, Chagas disease, etc.) (Hotez, 2008).
Some of these diseases are characterized by the fact that the methods of their prevention and treatment are known but not available in poorer countries, where they are most prevalent. Neglected tropical diseases affect more than a billion people and cause nearly half a million deaths annually. NTD's are opposed to "three great killers" - AIDS, tuberculosis and malaria, which attract considerable attention of world public opinion, and the preventive activities of which receive significant funding.
In addition, as a result of mutation of the virus new diseases appear characteristic of tropical climate. For example, in 2006 in Panama a danger of the epidemic was declared after at least six people died from a mysterious illness. According to medical specialists, the disease the causes of which remain unknown, progresses rapidly affecting nervous system and leading to failure of the kidneys. At least six people died from this disease, more than ten people were hospitalized with symptoms of a mysterious disease (Hotez, 2008). The government appealed to the international organizations in order to study the virus and develop means of counterbalancing vaccine.
The effects of evolution and mutations of tropical diseases
The result of the evolution of pathogens of natural foci diseases, caused by environmental adaptation to different natural and geographical and social conditions, is their geographical variability, change of their heterogeneity. The emergence of antigenic variants of pathogens is due to their prolonged circulation under different habitats in different evolutionary prevailing biocenoses. Some serovariants differ not only in antigenic structure, but in pathogenicity for humans and animals, vector susceptibility, as well as different sensitivity to chemical preparations and antibiotics (Cooperation and progress on tropical disease in Panama, 2004). Diseases specific to tropical and equatorial latitudes today are able to mutate and adapt to the mild climate.
Thus, in different geographical regions circulate various serological variants of Venezuelan and other equine encephalomyelitis. The various serological groups include strains of the American eastern equine encephalomyelitis, one of which includes viruses isolated in the United States, the other - in Panama, Argentina, Brazil and the island of Trinidad. In countries of South America circulate strains of Venezuelan equine encephalomyelitis virus serotypes IA, IB, IC, III and IV, in countries of North America - IE, II. Similarly, the viruses of the American western equine encephalomyelitis, isolated from mammals in Canada and California, are significantly different in antigenic composition from the viruses isolated in Florida, Massachusetts, from birds and mosquitoes (Cooperation and progress on tropical disease in Panama, 2004).
The emergence of antigenic variants of arboviruses is caused by their prolonged circulation under different habitats in different evolutionary prevailing biocenoses. Some serovariants differ not only in their antigenic structure, and pathogenicity for humans and animals. Thus, strains of Venezuelan equine encephalomyelitis virus type II isolated in Florida from mosquito, as well as strains of subtype IE isolated in Mexico from mosquitoes, horses, donkeys and human, differ from the Venezuelan equine encephalomyelitis virus isolated in South America by less pathogenicity and do not cause epizootics of horses, and epidemic outbreaks. In countries of Central and South America, mostly circulate strains of Venezuelan equine encephalomyelitis related to the subtype of IB, which may cause large epidemics and epizootics.
Thus, the diseases in people have different clinical course and different severity, because the circulation of the agent involves different strains of Leishmania, the types of mosquitoes and their hosts. Heterogeneity of strains of pathogens of vector-borne diseases circulating in different continents, determine the epidemiological risk of introduction of exotic variations of these agents in the area where evolutionally the circulation of other variants formed: collective immunity of the population to the local strains may not provide protection against imported exotic variants of pathogens.
Speaking about the microevolution of parasites, one should bear in mind the processes that occur in populations of not only the parasites, but as well as of their hosts (that is, microevolution of the whole parasite system). Changes in the nature of host populations can lead to changes in the population of parasites. Thus, the natural foci of diseases serve good natural models for studying general biological laws which determine the existence of pathogens in various ecological systems.
Socio-economic impact of tropical diseases on Panama region development
Demographical situation in Panama region and the role of tropical diseases
Tropical diseases greatly influence the population growth rate in the zone of Panama Canal. In 1963-1972, the population growth rate made about 3% per year, and the annual growth rate in 2000-2006 equaled to 1,6%. By the end of 1980s, the birth rate was 34,5 people per a thousand residents, the mortality rate made - 5,7; and the infant mortality rate (in 1971) made 37.6 per 1 thousand live births (Nájera, 2010). Average life expectancy reached 55.8 years, while the population mostly died because of infectious pathology. The main causes of death were coronary heart disease and other cardiovascular diseases, malignant neoplasms, enteritis and other intestinal diseases, childhood infections, tuberculosis, respiratory diseases (Cooperation and progress on tropical disease in Panama, 2004).
In 2002, the World Health Organization concluded that infectious diseases cause 22% of deaths in the world today. Most of them were theoretically preventable, since the most powerful outbreaks of epidemies happen in poor countries, with poorly educated population who does not have the resources necessary for fighting with infections. For example, according to the World Bank estimates, in Central and Latin America, infections are the cause of 50-52% of deaths, and only 5-10% - in the industrialized countries (Hotez, 2008).
Malaria, sexually transmitted diseases are still widely spread in Panama; every 5-6 years, there are the outbreaks of poliomyelitis in Panama. In the central provinces, ankylostomiasis and necatoriasis are distributed, as well as wuchereriasis, Chagas disease, arboviral infections. Most of the population suffers from protein-energy malnutrition (60,7% of children under the age of 5), vitamin A deficiency and endemic goiter (Purnell, 1999).
Nowadays, the average life expectancy in Panama makes 75 years (men - 72.7 years, women - 77,8 years), but per each 1000 residents 20.78 were born and 6.25 people died annually. At the same time, 92,6% of the adult population is properly educated; the Human Development Index in 2005 - made 0.812 and the Gini coefficient - 0.561 (Nájera, 2010).
Medical service and progress in treating tropical diseases
In Panama, medical services are provided by public hospitals and institutions of social insurance, which cover only about 7% of the population (insurance does not cover the areas of banana plantations, where the most of population works), and in private clinics. In 1972, there were 38 hospitals per 5.7 thousand beds (about 3 beds per 1 thousand inhabitants), including those in private hospitals - 450 beds. There were 1,2 thousand doctors (1 doctor for 1,2 thousand inhabitants), 155 dentists, 60 pharmacists and about 3 thousand of nursing staff (1972). Now, doctors are trained at Medical Faculty of the University of Panama. Expenditure on health amounts to 9,2% of the state budget (Purnell, 1999).
The level of medical institutions and the quality of services in Panama are high enough and are based on the U.S. standards. According to local legislation, the government of Panama provides medical care to all subjects to foreign countries, traveling through its territory. But medical insurance of international standard is strongly recommended (Nájera, 2010).
American scientists have found weaknesses in the genetic code of the parasite that causes three of worst tropical diseases in the world. The study conducted by these scientists reveals the possibilities for the development of effective treatments for sleeping sickness, Chagas disease and leishmaniasis (Cooperation and progress on tropical disease, 2004).
Great international consortium has spent 32 million dollars and 10 years for the study of genome of parasites trypanosomatids. These parasites are single-celled organisms that are transmitted to humans and animals through insects. The most efficient mean of treatment of sleeping sickness is now considered a drug Melarsoprol created on the basis of arsenic. But the drug itself causes the patient's death: it kills one patient out of twenty taking the drug.
Sleeping sickness is common in Northern Africa, its vector is the tsetse fly. Chagas disease is prevalent in Central and South America, its carriers are blood-sucking midges. Leishmaniasis, the most common of these three diseases, occurs in tropical countries and is carried by mosquitoes. Vaccines to protect against these diseases have not yet been developed. Genetic analysis showed that it would be extremely difficult to develop such a vaccine, as the parasites have developed the mechanism of resistance to the protective immune system of humans (Purnell, 1999).
According to scientists, the development of effective treatments for these diseases can take ten years or more. Additional research and resources for carrying them out will be inevitable. British scientists are hoping for the assistance of such international programs as the Drugs for Neglected Diseases Initiative.
Today, Panama is still an endemic area for malaria and yellow fever (that is, an area where one can catch these diseases), although in a very modest percentage. By the way, not only Panama, but most countries in South America, Asia, Australia and Oceania, Africa remain endemically dangerous. Mankind has tried many methods to combat malaria through the destruction of mosquitoes and their larvae, making it in a variety of ways - using insecticides, fish consuming mosquito larvae, through flowers, etc. Currently, a unique method of treatment of malaria in mosquitoes is being developed, and the end of this work is not far off (Nájera, 2010).
National and international economy in the context of tropical diseases spreading
Epidemies of diseases typically affect not only national, but also international economies. For example, the US National Intelligence Council estimated the damage from the atypical pneumonia epidemic which broke out in 2002-2003 at $ 10-30 billion. The epidemic, which resulted in a relatively small number of deaths (approximately 10% of the patients died out of about 7.2 thousand people in 28 countries of the world), affected agriculture, tourism and other business sectors. Many companies started to invest more resources in communications in order to minimize the number of trips of their employees in the areas affected by the epidemic (Hotez, 2008).
Every day, 2 million people cross the borders of the countries of the world, thus most of epidemics, including tropical ones, can spread almost immediately. With the development of international trade, many agents of dangerous diseases get into other countries with imported food. Local health systems are often not prepared to deal with exotic diseases, unusual for this area. As a result of global warming, the epidemics are spreading at an increasing rate, and tropical diseases now affect the residents of midlatitudes. The risk of infection also increases due to the spread of central air conditioning units, development of public transport, etc.
In general, the economic damage from infectious diseases is enormous, and professionals find it difficult even to name the approximate figures of global damage. The fact is that outbreaks cause both direct and indirect damage, which is most problematic for evaluation. For example, the American Academy of Pediatrics estimates that child's illness is causing economic losses of about $ 1235 (in 1999), taking into account the decrease of parents' productivity, additional expenditures and time for preventive measures, disinfecting toys, etc. (Purnell, 1999).
The positive results of controlling epidemics of tropical diseases in the early 20th century made the completion of construction of the Panama Canal possible. The overpass of the channel under the jurisdiction of Panama gave the country a powerful impetus to development. The unique geographical position of the Isthmus of Panama made it the center of the world trade, and the channel became the major factor in the economic activity of the country. Its future upgrade could improve the efficiency of the service sector, which will lead to an increase in living standards. Panama has created unique tax environment for investors, builders and people wishing to develop the tourism sector. The Legislation has been enacted that supports preferential loans for local developers, largest foreign construction companies have been attracted to the country. In ten years the country has made great strides forward, becoming a major financial and construction center in the region, and rightfully takes its place in the alignment of forces in the markets of Central and South America.
However, in spite of the fact that in 2005 Panama rose to the top spot in the global index of the most comfortable countries of the world, there is a risk of yellow fever, hepatitis A, rabies, cholera, typhoid and malaria. To finance the programs of the Ministry of Health the government resorted to large loans from the United States, the Inter-American Development Bank and World Bank. However, Panama has received the highest rating in the category of safety and health standards, which is famous for the high level of its organization, modern equipment and affordable prices.