Malaria in the World
Malaria is result of infection with one of four species of parasite of the genus Plasmodium. P. vivax, P. ovale, P. malariae, and P. falciparum, the most serious and lethal of the four, are all transmitted from human to human by Anopheles mosquitoes. The disease is present in 102 countries. It is estimated that between 1 and 2 million deaths occur annually due to malaria and the majority of these deaths are in children under 5 years of age. Almost all of these deaths are attributable to P. falciparum. This deadly parasite is prevalent in Africa and predominating in Southeast Asia. This is a fairly recent phenomenon. While malaria has been eradicated from many parts of many African and Southeast Asian countries, the proportion of infections with P. falciparum has increased to represent the majority. In addition, intensification and spread of resistance to antimalarial drugs among parasites has resulted in increased severity of disease and death. The reason for these changes in the epidemiology of malaria is largely attributable to changing environmental conditions in areas of intense economic development and the spread of malaria to areas previously free of the disease as millions of people move into malarious areas to claim land, seek wealth or to escape civil disturbances and war.
Social and Cultural Aspects
Despite advancements in biological and environmental technologies to control malaria, success has often been unobtainable. The reason for this is that for measures to reduce malaria infection and the duration and severity of disease to be s, social and cultural factors must be taken into consideration. An understanding of the roles of individuals and communities in the transmission, diagnosis, treatment and prevention of disease is of much significance, but often overlooked. The modern approach to malaria control is shifting from an empirical style to a social science perspective of the community.
Malaria varies from being unstable to stable in specific countries and regions. Unstable malaria is characterized by epidemics occurring several times every decade, but not annually. This implies that each time there is an outbreak of malaria it can quickly reach epidemic proportions due to a loss of immunity in the population. In this case, the morbidity rate is severe in all age groups, and when P. falciparum is involved, a high mortality rate may also be the case.
Stable malaria infers a regular presence of malaria in the population. In this case, mortality is highest in infants but drops off as the survivors of childhood develop a partial immunity, or tolerance, to the continual presence of malaria parasites in the bloodstream.
In Africa most malaria transmission takes place on the savannah as well as on the fringes of deserts and highlands. Life in the fringe habitats is frequently nomadic and characterized by cyclic climatic patterns (i.e. some years having exceptional rainfall). These factors can all lead to serious epidemics. Malaria in the savannah is typically stable.
In Southeast Asia, South America, and Africa, the forest has become an important malaria transmission area. Malaria transmission typically does not occur in urban areas, except in peri-urban areas where slums may simulate rural environments.
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Forest Malaria - A Border Problem
In many regions of the world malaria is in association with tropical forests. Deforestation has pushed malaria out of many regions in Southeast Asia, South America and Africa into each country's more remote forested regions. These areas are frequently in association with international boundaries and are home to tribal populations that are, not only of low education and poor economic status, but are often highly migratory due to transient employment opportunities (logging, mining, reforestation, road construction, etc.), hunting, gathering, gem mining, and illegal activities. Consequently, even though malaria is endemic in much of these forest regions, the nomadic nature of the people often brings them into areas of exposure to different genetic variants of the same species of Plasmodia, usually P. falciparum, resulting in epidemics due to lack of immunity. Subsequent cross-border transmission of malaria confounds the problems associated with malaria control programs in the individual countries.
The most famous example of migratory spread of malaria from forested areas of one country to other non-forested and forested areas of another nation is represented by the movement of gem miners from Borai province in Cambodia. For example, investigations at the malaria clinic in Mae Sod district in the province of Tak, Thailand, indicated that more than 80% of the infections were acquired in the Cambodian gem mining area. This district is located on the Thai-Myanmar border, approximately 1000 kilometers from Borai. Many of these Tak migrants are Burmese, Karen and Moung tribals which indicates a clear mode of transport for P. falciparum into Myanmar. There have even been reports of gem-miners coming from as far away as Bangladesh, on foot!
Southeast Asian countries that are currently trying to deal with the problem of forest malaria, typically in association with national borders, are Bangladesh, Cambodia, Yunnan province in China, Indonesia, Lao PDR, Malaysia, Myanmar, Thailand, and Vietnam. Even though these countries are all neighboring, collaborative efforts of the past have been, when implemented, difficult. The World Health Organization's delineation of Cambodia, Laos, Vietnam and China into the Western Pacific Region and the others into the Southeast Asia Region further confound the problem.
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It has been hypothesized that the gem mining area located on the Cambodian side of the border with eastern Thailand is the epicenter for multiple-drug resistance. It's generally presumed that chloroquine resistant P. falciparum evolved in this region in 1957. Administration of an alternative drug, a sulfadoxine-pyrimethamine combination, in 1973 for falciparum malaria was seen to have no effect in Cambodia. Resistance to this combination was reported to be widespread throughout Thailand by 1981. Mefloquine was then introduced into the drug combination and was highly effective at providing a 97-100% cure rate across Thailand. However, in just 7 years the cure rate declined to 21% in eastern Thailand (Trat and Chantaburi provinces).
The geographical spread of chloroquine then sulfadoxine-pyrimethamine resistance into Myanmar and then into Bangladesh supports the epicenter hypothesis. Furthermore, reports of mefloquine resistance in patients that were infected on the Thai-Myanmar border indicate that multi-drug resistant parasites are being transported by migrants from the central focus to be taken up by vectors and subsequently transmitted to the local population.
Recently new foci of drug resistance have been found in areas between Myanmar, Yunnan province in China, Laos and Thailand (Malaria in the Southeast Asia region, 50 commemorative series-1, WHO).
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Paradigm Shift - Who is sick? Where? Why?
Malaria is now being recognized as a local phenomenon that varies from region to region and sometimes village to village in a single district. Therefore, there is no single approach to controlling malaria that could be applied globally. What may be highly successful in one region, may not be in another region. One example of this is insecticide impregnated bed nets. Use of these nets in Africa has shown some good results to date. But in the border region of Myanmar and Thailand overnight tribal hunters and forest gatherers will not accept these nets due to the smell that is offensive to them as well as to the animals they are hunting, resulting in them vacating the area. In addition, the villagers complain about the high costs associated with impregnation of the nets. Consequently, promotion of insecticide bed nets in this region only leads to non-use of any bed net.
In addition, the disease is now being viewed as many diseases depending on the vast array of varying interactions, e.g. economical, social, cultural, ecological and biological. Accessibility of health services, economical status, immune status, behavioral practices, species of parasite all contribute to determining who will become infected, who will develop disease, severity of disease, and who will die. Distinction between infection, and associated heath risks of perennial infection, and disease is important. Contemporary control of malaria in terms of treatment is to cure the patient of disease rather than to reduce parasite reservoirs. Early diagnosis of disease and prompt adequate treatment will shorten the duration of disease and prevent the development of complications - the cause of death due to malaria. The referral process is an important step in this process that must be developed to work. For example, patients may not follow-up a referral in fear of extra associated costs. Access to early diagnosis and treatment is considered a fundamental right of all populations affected with malaria.
Malaria and poverty are too often hand in hand. Malaria tends to spread during attempts at agricultural development, colonization or exploitation of a natural resource. Consequently it strongly hinders socioeconomic development in underdeveloped countries and control measures have to be practical and cost-effective. WHO's Global Malaria Control Strategy 1993-2000 states that progress aimed at malaria control most importantly needs to be sustainable, even if slow. Selective use of preventive measures, wherever they can lead to sustainable results, minimizes wasteful use of limited resources.
Conversely, malaria management must respond to unexpected situations arising from social, economic, or political changes. To address this, local and national capabilities need to be strengthened and decentralization must follow even to the village level.
When the approach shifted from malaria eradication to malaria control many programs admitted their failures. This resulted in a loss of interest by donors and financial support for malaria diminished in favor of more current new issues. An analysis of the failures of previous programs suggests many reasons, e.g. indiscriminate use of insecticides, failure to deliver antimalarials to a population at risk, etc. However, one commonality seen between failures around the world is the unavailability of prompt and adequate treatment.
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