Health and Disease in the Tropics
Much of the work BawaHealth is focused on is built around combating the major health issues listed below. We have provided some detailed (but often incomplete) descriptions of the most prevalent of those diseases impacting the village of Bawa, Cameroon.
HIV & AIDS
Other Health Issues
Diseases of Children
HIV & AIDS
AIDS is an acronym for Acquired ImmunoDeficiency Syndrome. This disease is caused by Human Immunodeficiency Virus (HIV). Infection occurs through contact with body fluids of an infected individual, most commonly through sexual contact or the practice of sharing needles while using IV drugs. AIDS has received a stigma as being a disease primarily of homosexual males; however, it is more frequently infecting heterosexuals. In fact, in Africa heterosexual transmission is the most common means by which the virus is spread. HIV infection is extremely prevalent throughout most of Africa. In Cameroon, the prevalence is estimated by UNICEF to be about 7%.
As of 2003, AIDS has surpassed malaria as the leading cause of death in Bawa, being responsible for 41.5% of all deaths in the village in 2003 and 2004. Among the 21 to 50 year old age group, AIDS is responsible for 68.8% of all deaths. In Bawa, AIDS causes more deaths in women than in men (22 vs 13 for the past two years). This is probably a reflection of polygamous relations characteristic of family structuring in Bawa.
We do not currently have any data on HIV infection rates in the village of BAWA. The high mortality rate recorded suggests that the prevalence is extremely high. Determination of the actual prevalence and epidemiological profile of HIV infection is an important part of the health survey that we plan to conduct in December 2005 and January 2006.
If funds become available for medication, we plan to treat infected individuals. In any event, we are planning an aggressive education campaign aimed at minimizing further spread of the virus through the community.
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Malaria is a disease caused by protozoan parasites of the genus Plasmodium which occurs in the red blood cells of humans. World-wide about 800 million people are infected with malaria. Approximately 1.7 million African children die every year – an African child dies of malaria every 20 seconds. Malaria kills more children than any other disease, including AIDS.
This deadly disease that is transmitted from person to person by the “bite” of mosquitoes of the genus Anopheles is extremely prevalent throughout sub-Saharan Africa, including Bawa. Four species of the malarial parasite occur in humans: Plasmodium vivax, Plaxmodium ovale, Plasmodium malariae, and the most virulent of all, Plasmodium falciparum. While all four species occur in Cameroon, P. falciparum is the most common by far. Falciparum malaria is most deadly because of the condition known as cerebral malaria that is associated with the disease. This disease poses the greatest threat to young children and pregnant women.
In Bawa, malaria is the leading cause of death of children, account for 46.8% of all deaths of children under 11, and 64.7% of death attributable to infectious diseases. Many deaths may be prevented in the future by the distribution of insecticide-treated bednets to residents of the village, especially for children and pregnant women.
Likewise, malaria is a significant cause of death among the adult population, accounting for over 1 in 5 deaths in the village.
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Ascariasis is a disease caused by infection with the large human roundworm Ascaris lumbricoides. This is the most prevalent parasitic worms worldwide, infecting one in every four people (almost 1.5 billion people). Each year between 60,000 and 100,000 people, mostly children die as a result of infection with Ascaris lumbricoides. This nematode has a direct life cycle in which the definitive host becomes infected by ingesting the eggs in fecally contaminated food or water. Adult worms live in the small intestine where they feed on digested food material and epithelial cells.
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Hookworms are a very important parasite of humans. Hooksworms exhibit a direct lifecycle in which infective larvae living in fecally contaminated soil, penetrate the skin of the host. Infection usually occurs as a result of bare feet coming in contact with fecally contaminated soil. After penetrating the skin, the larvae gain entry into the circulatory system. They undergo a migration through the lungs and eventually end up in the small intestine. Hookworms feed on blood by severing intestinal blood vessels with their cutting plates or teeth depending on species. The species infecting humans are Necator americanus and Ancylostoma duodenale. Hookworm infection often leads to severe anemia. Worldwide 1.3 billion people are infected with hookworms, leading directly to 65,000 deaths per year.
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Schistosomes are a group of worms known as blood flukes that live in the mesenteric blood vessels of humans. Two species are prevalent throughout sub-Saharan Africa, Schistosoma mansoni, and Schistosoma heamatobium, which live in the mesenteric veins of the intestine and urinary bladder respectively. The worms lay eggs which burrow through the tissues of the urinary bladder or intestine where they may cause considerable damage. Eggs are ultimately passed in the urine of feces, depending on species. When passed into water eggs hatch releasing a free-swimming larval form that penetrates the snail intermediate host. Within the snail the parasites develop into the infective stage to humans, known as cercaria. The cercariae, that are shed by infected snails, enter the human host by penetrating the skin. Worldwide about 200 million people are infected with schistosomes, which cause 20,000 deaths per year. In addition, infection with schistosomes often leads to decreased absorption of nutrients in the intestine, leading to reduced physical and mental development.
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Lymphatic filariasis is a disease caused by infection with a group of worms called filarial worms. Adult worms live in lymphatic vessels where they block the vessels leading to the disease. One severe, often disfiguring form of the disease is known as elephantiasis. The two species of filarial worms causing lymphatic filariasis are Wuchereria bancrofti and Brugia malayi. It is estimated that worldwide 120 million people are suffering from lymphatic filariasis, with W. bancrofti being responsible for the majority of these infections. Wuchereria bancrofti infection is problematic throughout much of sub-Saharan Africa. This parasite is transmitted from person to person by mosquitos. In the severe form of the disease known as elephantiasis, the skin becomes disfigured with a loss of elasticity. Ultimate extremities may become greatly enlarged leading to gross disfiguration. The lower legs and scrotum are the most commonly affected regions.
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Onchocerciasis is disease caused by infection with filarial worms (Onchocerca volvulus). In humans the worms live in the subcutaneous tissue where they shed young known as microfilaria that enter the blood stream. The worms are transmitted from person to person through the bite of black flies (Simulium spp.). Over time the body’s immune response to the worms can lead to blindness; a condition known as river blindness, because this disease occurs primarily along rivers where the black flies live. Merck pharmaceutical company in conjunction with the World Health Organization and the Clark Foundation have undertaken a major attempt in Africa to eradicate this parasite. In many parts of Africa the prevalence of onchocerciasis has been reduced by 90%. Nevertheless it is estimated that 150,000 people in sub-Saharan Africa are still afflicted by onchocerciasis and it remains the fourth leading cause of blindness in the world.
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A number of tapeworms infect humans, but three are the most common; Hymenolepis nana, Taenia saginata, and Taenia solium. Hymenolepis nana is the most common tapeworms of humans, infecting an estimated 75 million people worldwide, mostly children. This tapeworm is also a common parasite of rodents. The parasite has an indirect life cycle in which the adult tapeworms mate in the small intestine. Eggs that are passed in the feces may infect another human or rodent host directly or may infect a grain beetle intermediate host. Humans may become infected by ingestion of the eggs in contaminated food or water, or by ingestion of infected beetle intermediate hosts.
Most intestinal tapeworm infections are light and are therefore asymptomatic. Symptomatic infection is typically mild and ill-defined. The most common symptoms of infection include diarrhea, abdominal discomfort, anorexia, and nausea. Intestinal tapeworm infections are easily treated with the drugs praziquantel or niclosamide, which result in a complete cure.
The beef tapeworm, Taenia saginata and the pork tapeworm Taenia solium are two tapeworms that occur in humans. Adult tapeworms live in the small intestine where they mate. Eggs are passed in the feces. The intermediate hosts in the life cycles of these tapeworms are cattle and pigs respectively. The intermediate hosts become infected when they ingest the eggs on pasture or food that is contaminated with human feces. Humans become infected by ingesting larval tapeworms that are in raw or poorly cooked beef or pork. Adult worms are quit large and may exceed 30 ft. in length. Worldwide about 77 million people are infected with the pork tapeworm and about 10 million people are infected with the beef tapeworm.
There is a unique component in the life cycle of the pork tapeworm, T. solium, that makes it a particularly dangerous parasite. In addition to serving as the definitive or final host in the life cycle, humans may also assume the role of intermediate host (that normally exhibited by the pig. In this instance, humans swallow the eggs, becoming infected with the larval tapeworms, called cysticerci. This serious disease, known as cysticercosis, may involve the eyes leading to blindness or the brain leading to neurological problems and even death.
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Protozoans are not animals. Animals by definition belong to the kingdom Animalia. Protozoans belong to the kingdom Protista. Protists are usually microscopic, single-celled organisms whereas animals and plants are multicellular. There are fungus-like protists, plant-like protists, and animal-like protists. The animal-like protists are called protozoans and although they are not animals, zoologists (scientists who study animals) have traditionally dealt with the protozoa.
Most protozoans are free-living and harmless to humans; however, some of the most serious diseases of humans, such as malaria, are caused by parasitic protozoa. Bacteria are also single celled organisms that are responsible for a plethora of human diseases such as anthrax, tuberculosis, cholera, plague, gonorrhea. Bacteria differ from protists in that they are prokaryotic cells, meaning they lack a true nucleus.
Protozoa are divided into groups based primarily on the nature of their locomotory structures, or those structures that they use to get around. The main groups include the amoebae who use pseudopodia, or false feet, to move, ciliates that use cilia to move, flagellates that have flagella, and apicomplexans which have no locomotory structures.
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A parasitic amoeba, Entamoeba histolytica is the cause of a serious type of dysentery (bloody diarrhea) in humans. Close to 500 million people are infected with it at any given time, and it kills 100,000 people each year (Roberts and Janovy, 2000). The amoebae live in the large intestine, where they invade intestinal tissue and cause ulcers. Before leaving with an infected human’s feces, the amoebae transform into cysts. The cyst is a stage that can live for several weeks in water or moist soil. Another person becomes infected by ingesting the cyst in fecally contaminated food or water.
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Giardiasis is a disease that is caused by infection with the intestinal flagellate, Giardia lamblia. The trophozoite of Giardia lamblia lives in the small intestine of humans and other mammals. Infection with G. lamblia is common worldwide and can result in severe diarrhea, though it does not cause dysentery.
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African trypanosomiasis is a disease that is caused by infection with flagellates of the species Trypanosoma rhodesiense or Trypanosoma gambiense. It is estimated that between 300,000 and 500,000 people have African trypanosomiasis. In human these parasites reside in the blood stream, then in the central nervous system in later stages of the infection, and this causes African sleeping sickness. This parasite is transmitted from host to host by the bite of a testse fly.
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Cryptosporidiosis is a disease caused by infection with an intestinal apicomplexan, Cryptosporidium parvum, a protozoan parasite in the same phylum as the ones that cause malaria. Cryptosporidiosis is usually a water-borne disease. In healthy hosts, infection with C. parvum causes a self-limiting diarrhea; however, in someone that is immunocompromised such as an AIDS patient the disease can be severe, even life-threatening. The prevalence of cryptosporidiosis tends to be high in areas were sanitation is inadequate of lacking. This is especially problematic in many developing countries, such as Cameroon, where there is a lack of sanitation in conjunction with a high prevalence of AIDS.
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Issues with Water
“Americans use 270 billion gallons of water on their 50 million lawns. This is enough water to give every person a shower for four days in a row.” (Burdick, 2003)
Bawa has no clean water or no sanitation system. Although it may be hard for you to imagine, this is a common problem throughout the world. Can you imagine not having water flowing from a tap in your home? What would life be like without that luxury? Less than 15% of the world’s population has adequate water supplies. The problem is particularly serious throughout much of Africa. In coming decades, water may become the most scarce and coveted natural resource, serving as an impetus for international hostility. The next world war may not be about religion or oil, but about water.
In Bawa, all drinking water is obtained from small rivers that are often heavily contaminated with human excrement. One major objective of BHI is to provide clean drinking water to the residents of Bawa and neighboring villages.
Typhoid fever is a disease caused by infection with the bacterium, Salmonella typhi. The bacterium is most commonly transmitted through fecally contaminated water, or less frequently food or other substances. The bacterium is also shed in the urine of infected individuals although feces is a more common source of infection. Initially after ingestion, the bacteria establish in the intestine; however, as the infection progress the bacteria leave the intestine and colonize the lymphatic system and blood. At this point 7 to 10 days after initial exposure, symptoms of infection begin to appear and include fever, the appearance of ìrose spotsî red lesions on the abdomen, and spleenomegaly (enlargement of the spleen). In severe cases perforation of the intestine and hemorrhage may occur. The fever usually persists for about a month in untreated cases with about a 20% mortality rate and an additional 10% of patients suffering from intestinal hemorrhage. Even after signs of the infection have passed, the convalescent individual may by passing infective bacteria in feces and urine for several more weeks.
Although typhoid fever is very treatable with antibiotics and preventable with vaccination, this disease ironically is the second most common fatal infectious disease of children in Bawa and is second only to AIDS as the leading cause of death in the 21-50 year old age group.
One of our highest priorities is to see all residents of Bawa vaccinated against this deadly disease. Additionally, the provision of clean drinking water will greatly reduce the risk of this disease.
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Other Health Issues in Bawa, Cameroon
At the outset, it is very difficult to assess the most urgent health issues in the village. No demographic data has ever been recorded in the history of the village. We have commissioned a census of all individuals residing in the village. We hope to have the census completed by August 1. We are fortunate in having mortality data for 1995-2004 acquired from the medical center in Dschang. Undoubtedly, this data under-reports mortality but it does provide a rough overview and basis for assessment of the health issues in the village. Estimates given are based on this data and assume a population of 500 full-time residents for the village. Estimates will be refined after the census is complete.
In the 10 year period 1995-2004, 189 deaths were recorded for the village of Bawa. In the 8 year period 1995-2002, on average 3.1% of the population died each year. Note that this number has more than doubled to an average of 6.5% for 2003 and 2004 with AIDS deaths beginning to appear.
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In the 10 year period 1995-2004, deaths of 47 children under the age of 11 have been recorded from Bawa. This accounts for 25.3% of total mortality in the village. All of these deaths were attributable to either infectious diseases (72.3%) or a form of malnutrition called kwashiorkor, that is caused by protein deficiency associated with dietary issues at weaning (27.7%). Of deaths associated with infectious diseases in children under 11, the 4 diseases responsible were malaria (64.7%), typhoid (14.7%), pneumonia (14.7%), and intestinal helminthiases (5.9%).
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