Parasitic Diseases (Neutropenia Definition), a diverse group of illnesses caused by more than 50 different protozoa and helminths. Protozoa are one-celled animal-like organisms (protists), and helminths are worms. The diseases they cause are transmitted by fecal contamination of food and water, by insects and other arthropods, and by eating uncooked or undercooked meat, fish, or shellfish. The illnesses produced by parasitic organisms are extremely varied and encompass many types of medical problems. Neutropenia definition includes a condition when the white blood cell count falls below optimum levels.
Parasitic diseases occur throughout the animal kingdom, but this article deals only with diseases of humans. Among the most common of the parasitic diseases of humans are malaria, amebiasis, schistosomiasis, ascaris (roundworm), and hookworm. One parasitic infection trichomonas vaginalis is spread among humans as a venereal disease.
Parasitic infections pose a significant health problem in many parts of the world, particularly in tropical and subtropical areas. For example, in villages of South America and Africa often 100% of the children are infected with a parasitic disease most commonly ascaris or hookworm. Parasitic diseases such as these can affect growth and development in children.
Their widespread occurrence in adults can affect many aspects of the life of a nation. Malaria is so important a cause of morbidity and mortality in certain areas that it has influenced the migration of people, the outcome of wars, and the genetic patterns of races.
For example, certain genetic abnormalities in the oxygen-carrying blood pigment hemoglobin have been perpetuated in the gene pool of peoples in certain malarious areas of Africa and the Mediterranean region because this abnormality is associated with a selective advantage for survival (a resistance to malaria) for these peoples. Sickle-cell anemia, in some blacks of tropical African origin, is one such condition.
Since the beginning of recorded history parasites have fascinated their human hosts. The attribution of rudimentary intelligence to tapeworms by the ancient Chinese, the description of the fiery serpent in the Bible, and the careful description of periodic fevers (referring to malaria) by Hippocrates all attest to this fascination. When the Dutch naturalist Antoni van Leeuwenhoek first used the microscope in 1682, he observed parasites “mobile animalicules” in his own stool.
Parasites also have been described in literature and art. Shakespeare referred to measled tongue (animal cysticercosis) in his writings, and the Belgian painter James Ensor used the intestinal tapeworm to describe the state of medical care in his painting the bad doctors. Neutropenia definition includes a condition when the white blood cell count falls below optimum levels.
Some of the most common parasitic diseases are confined primarily to humans, and their spread depends on inadequate disposal of human feces and incomplete water purification processes. Two protozoal diseases (amebiasis and giardiasis) and six helminthic diseases (ascaris, hookworm, strongyloidiasis, trichuriasis, pinworm, and cysticercosis) are spread in this way.
These diseases are common in many tropical countries, particularly where sanitation is poor and conditions exist for prolonged survival of the organisms in water or contaminated food. Neutropenia definition includes a condition when the white blood cell count falls below optimum levels.
Some parasites follow cultural patterns of eating and preparing food. For example, societies that ingest undercooked meat acquire the protozoan Toxoplasma gondii and the helminth Trichinella spiralis from pork, bear, or walrus meat and tapeworms from pork, beef, or fish. The custom of eating raw crabs allows for paragonimiasis; raw freshwater fish, clonorchiasis; and raw saltwater fish, anisakiasis—all due to helminths in their tissues.
Arthropods also are important vectors. Mosquitoes spread a protozoan disease—and a helminthic disease—filariasis. Ticks spread Babesia from rodent to humans. Flies spread several parasitic diseases.
The tsetse fly spreads trypanosomes sandflies transmit leishmania; and black flies (Simulium) spread the worm that causes onchocerciasis. Neutropenia definition includes a condition when the white blood cell count falls below optimum levels.
The frequency and distribution of the arthropod-carried diseases follow the habits of the vector more than any other factor. For example, malaria outbreaks occur when insecticide control of its mosquito vector fails, and babesiosis arises when the tick, rodent, and deer population increases. Even the site of infection may vary according to the vector habits.
For example, nodules caused by onchocerciasis occur on people’s scalp in Central America but on the thighs in Africa, reflecting the preferred biting sites of the black flies in these regions. Neutropenia definition includes a condition when the white blood cell count falls below optimum levels.