Parasites are organisms that obtain food and shelter by living on or within another organism. The parasite derives all benefits from association and the host may either not be harmed or may suffer the consequences of this association, a parasite disease. The parasite is termed obligate when it can live only in association with a host or it is classified as facultative when it can live both in or on a host as well as in a free form. Parasites which live inside the body are termed endoparasites whereas those which exist on the body surface are called ectoparasites. Parasites that cause harm to the host are pathogenic parasites while those that benefit from the host without causing it any harm are known as commensals.
Diseases caused by these organisms include amebic dysentary, sleeping sickness, malaria, river-blindness, elephantiasis and many more.
The chain of infection
What is a pathogen?
The first link in the chain of infection is the pathogen. A pathogen is anything that causes a disease. Pathogens include:
We come in contact with pathogens everyday. Most of the time our body’s immune system destroys them before they can cause harm.
Whether an exposure results in infection depends on three factors:
A pathogen (from Greek pathos, suffering/emotion, and gene, to give birth to), infectious agent, or more commonly germ, is a biological agent that causes disease or illness to its host.[1] The term is most often used for agents that disrupt the normal physiology of a multicellular animal or plant. However, pathogens can infect unicellular organisms from all of the biological kingdoms. The term pathogen is derived from the Greek παθογ?νεια, "that which produces suffering." There are several substrates and pathways where by pathogens can invade a host; the principal pathways have different episodic time frames, but soil contamination has the longest or most persistent potential for harboring a pathogen.
The body contains many natural defenses against some of the common pathogens (such as Pneumocystis) in the form of the human immune system and by some "helpful" bacteria present in the human body's normal flora. However, if the immune system or "good" bacteria is damaged in any way (such as by chemotherapy, human immunodeficiency virus (HIV), or antibiotics being taken to kill other pathogens), pathogenic bacteria that were being held at bay can proliferate and cause harm to the host. Such cases are called opportunistic infections.
Some pathogens (such as the bacterium Yersinia pestis, which may have caused the Black Plague, the Variola virus, and the Malaria protozoa) have been responsible for massive numbers of casualties and have had numerous effects on afflicted groups. Of particular note in modern times is HIV, which is known to have infected several million humans globally, along with Severe Acute Respiratory Syndrome (SARS) and the Influenza virus. Today, while many medical advances have been made to safeguard against infection by pathogens, through the use of vaccination, antibiotics, and fungicide, pathogens continue to threaten human life. Social advances such as food safety, hygiene, and water treatment have reduced the threat from some pathogens.
| Table of Contents |
| 1. Introduction |
| 2. How we contract parasites |
| 3. Common parasites in North America |
| 4. Periodicity and cyclic parasites |
| 5. Management of parasitic infections |
1. Introduction.
Many of us have heard about illnesses such as giardiasis or amoebiasis, but we tend to overlook the relationship between these parasites and digestive and systemic diseases and disorders. The common belief that people in the UK are free of parasites is a great illusion. Some estimate many millions of children are infected with worm parasites; only a small portion of which is detected and reported. This is particularly worrisome when one recognizes that microscopic (single-celled protozoans) make up about 90% of all parasitic infections. If existing parasitic infections are evenly distributed, there would be more than enough parasites for every living person to have one. The most recent statistics of the worldwide prevalence of certain selected parasites follows:
| Disease |
Human infections |
Annual deaths |
| Malaria |
489 million |
1-2 million |
| All worms |
4.5 billion |
|
| Ascaris |
1.0 billion |
20 thousands |
| Hookworms |
900 million |
50-60 thousands |
| Whipworms |
750 million |
|
| Filarial worms |
657 million |
20-50+ thousands |
| Schistosomes |
200 million |
0.5-1.0 million |
This is only a sample of the many parasitic diseases compromising human health worldwide. In temperate areas we are uneducated about the seriousness of parasitic diseases that reach their greatest impact in "tropical" countries from which many immigrate to the UK. Contributing factors to parasitic diseases in the UK, other than our own endemic parasites and immigration, include malnutrition, population density, economic conditions, sanitary practices, and life styles. Compounding factors in North Americinclude the lack of public/media awareness, educational materials/counseling and training of the public, as well as in some cases, the professional community. It is in this spirit that this educational pamphlet is offered to you.
2. How we contract parasites.
A parasite is a micro- or macro-organism that needs to satisfy its vital nutritional requirements by feeding off certain host tissues or body fluids that contain the specific biochemicals that it needs. There are parasites for every single tissue of the human body, once they gain access. An intestinal parasite has to gain access via the oral cavity with contaminated food or drink if it is to cause infection. Other portals of entry are irrelevant. Eight ways by which humans can contract parasitic infections are briefly summarized below.
2.1. Drinking water.
Some of the most common microscopic human parasites (Protozoa) are transmitted via drinking water contaminated with fecal material from infected persons. This simple cycle occurs in water from running streams as well as from tap water in homes in large US and Canadian cities served by surface water treatment plants. Parasites transmitted in this manner include Cryptosporidium and Giardia.
2.2. Skin contact with contaminated water.
This is the only method of infection available to certain parasites such as the schistosomes, some of the deadliest fluke (trematode) parasites of mankind. After emerging from the snail host, the infective larvae (cercariae) penetrate the skin of a person (swimmer, agricultural worker, children playing, etc.) and migrate in the human body ending up as adults in blood vessels (hepatic portal system). To get infected, one has to be exposed in an endemic area, ex., Africa, China, Mexico, Puerto Rico. At PCI, we have identified eggs in fecal samples from an isolated area near a stream in California nearby where a population of Vietnamese immigrants have settled.
2.3. Food.
Food intake is perhaps one of the most common ways of transmission of parasitic infections caused by microscopic (Protozoa) and macroscopic (worm, helminth) parasites alike. For example, Blastocystis and the cysts of the amoebas (both are protozoans) are infective when swallowed with contaminated food via the fecal-oral route. This can occur in a household setting or a restaurant. Similarly, the ingestion of the eggs of the human roundworm, Ascaris, readily occurs when fresh vegetables, ex., lettuce, grown in farms fertilized with infected human waste, are eaten without proper washing.
2.4. Insects.
Most blood sucking insects are capable of transmitting infectious agents via their bite as they attempt to feed on human blood. In the US, ticks transmit lyme disease, Rocky Mountain spotted fever, relapsing fever, Colorado tick fever, babesiosis, and rabbit fever; fleas transmit plague and endemic typhus, mosquitoes transmit malaria and dog heartworm, Triatoma (kissing) bugs transmit Chagas disease, and head lice can transmit epidemic typhus. If a person has had a history of a recent insect bite in any temperate or tropical part of the world, his/her blood should be tested for parasites. Insect-borne pathogens normally cause no harm to their natural (reservoir) hosts, ex., rodents, but become highly pathogenic in humans (their unnatural hosts).
2.5. Air.
Air-borne viruses, bacteria, and fungi are usually eliminated with the feces (occasionally orally) of a natural reservoir (usually wildlife) host but infect humans upon accidental inhalation. Examples in North America include histoplasmosis, Valley fever, and Hanta virus. These diseases are associated with bat guano, dust, and rodent feces, respectively.
2.6. Pets.
Despite what you may have been told, dogs, among other pets, are not man's best friend, parasitologically speaking. Dogs carry an intestinal tapeworm, Echinococcus, whose eggs spread all over their fur from the anal orifice during grooming. Unhealthy human contact with infected dogs, e.g., by kissing, brings the eggs into the human intestine which they penetrate as larvae and encyst in the body cavity, e.g., the liver or even the brain, as the life threatening hydatid cysts. Other worm parasites (helminths) are also readily transmitted from pets and other animals to man. Most notable are the beef and swine tapeworms, Taenia, by the consumption of beef and ham contaminated with larvae of these tapeworms.
2.7. People.
Close human-to-human contact is conducive to transmission of quite an assortment of sexually transmitted diseases including AIDS and herpes as well as other viruses causing cold and flu. Eating food in a restaurant or at home that may have been contaminated with Taenia eggs or Entamoeba cysts from the servers fecal through improper sanitary practices will surely produce infections with cysticercosis (appearing as lumps in the body or nerve organs) or amoebiasis (causing severe gastrointestinal distress, etc.), respectively. A recent inspection of an expensive restaurant in Los Angeles showed that 100% of all employees (not just servers) had fecal matter under their nails.
2.8. Soil.
Certain roundworm (nematode) parasites spend their transitional stages between one host and another as immature larvae in warm moist soil. Walking bare-footed or sitting on such fecally contarninated "seeded" soil in a wooded area or by a lake side, etc. will invite the larvae of hookworms or Strongyloides to penetrate the exposed skin and migrate in the body to finally become adults in the intestinal tract where the damage is done.
3. Common Parasites in North America and their Health Implications.
The most common parasites identified from North American patients at the Parasitology Center, Inc. (PCI), Tempe, Arizona are listed below in order of their prevalence from high to low:
Protozoa (rnicroscopic single-celled organisms)
Blastocystis hominis
Endolimax nana
Cryptosporidiuin parvum
Entamoeba histolytica
Entamoeba coli
Entamoeba hartmanni
Giardia lamblia
Chilomastix mesnili
Cyclospora cayetanensis
Helminths (macroscopic multicellular worms)
Ascaris lumbricoides (human roundworm)
Strongyloides stercoralis (threadworm)
Ancylostoma duodenale/Necator americanus (hookworms)
Enterobius vermicularis (pinworm)
Trichuris trichiura (whipworm)
In the USA, one-third of about 6,000 fecal specimens tested at PCI were positive for 19 species of intestinal parasites (Amin, 0. 2002.Seasonal Prevalence of Intestinal Parasites in the United States during 2000.
All the protozoan parasites listed above cause various degrees of gastro-intestinal (enteric) and systemic (extra-intestinal) symptomology and pathology, with Endolimax causing the mildest infections, and all are transmitted via contaminated food/drink. Enteric symptoms usually include bloating, diarrhea, flatulence, constipation, cramps, and maldigestion/malabsorption. Less frequent enteric symptoms include bleeding, irritable bowel, leaky gut, and excess mucus secretion. Extra-intestinal symptoms include allergies, fatigue, nausea, nervous-sensory disorders (ex., brain fog, memory loss, poor coordination), skin rashes and disorders, pain, and muscle problems. Less frequent extra-intestinal disorders include fever, headache, immune deficiencies, insomnia, and weight changes. Some of these symptoms are probably related to parasite toxic metabolic byproducts particularly in immune compromised patients. Some of the above protozoans are sufficiently invasive to become blood-borne, e.g., Entamoeba histolytica, that it may cause serious liver or brain damage.
Helminths:
Worm parasite damage depends largely on which tissues are invaded by the migrating larvae or the type of intestinal damage caused by adults. For example, after the ingestion and hatching of Ascaris eggs in the intestine of a new host, the emerged larva will migrate through the intestinal lining, lymphatic/blood vessels, the hepatic portal system, liver, right heart, lungs, then get re-swallowed and establish as one-foot long adult in the small intestine. Allergic responses to the metabolic byproducts of adult worms are known to cause asthma, insomnia, eye pain, and rashes. Aberrant larval migration can cause inflammatory reaction in the spleen, liver, lymph nodes, and brain. Pulmonary hemorrhagic sites may be accompanied by coughing, fever, and breathing difficulties. Fatal pneumonitis is a possible complication. Mechanical blockage may be caused by a large number of adults in the intestinal tract leading to toxemia and death. Adult worms occasionally penetrate the intestinal wall or appendix causing local hemorrhage, peritonitis, and/or appendicitis.
See Section 2 above (food, pets, people, soil) for methods of contracting worm parasites.
4. Periodicity and Cyclic Parasites.
4.a. A number of patients testing positive for parasites had subclinical infections and showed no overt intestinal or extra-intestinal symptoms. Those patients have been treated and their overall health has improved.
4.b. Another group of patients was symptomatic but no parasites were detected from fecal samples provided. These latter cases are related to one or both of the following factors:
Factor # 1. Other pathogenic organisms, ex., pathogenic bacteria, can cause symptoms comparable to those produced by typical parasites. These include enterotoxigenic Escherichia coli, Salmonella, Shigella, or Campylobacter. Like the typical parasites, these bacterial parasites are also amenable to successful treatment with herbal products.
Factor # 2. Because of the heterogeneous distribution and the cyclic nature of some of the most common human parasites, infections may not be detected in fecal sample if collected when parasites are not running in the main fecal flow. For instance, intervals of many days may intervene between amebic "runs" which may make the microscopic examination of multiple stool specimens necessary to confirm a positive Entamoeba histolytica infection. The sarne kind of periodicity and/or adherence to the intestinal lining are also known to occur in Giardia lamblia and Cyclospora cayetanensis. This explains the intermittent shedding and cyclic recovery of these parasites in fecal samples collected for testing. It is important to test for cyclic parasites when they are "running
5. Management of Parasitic Infections.
Parasites will compromise the host immune system as well as his state of physical, mental, and emotional well-being to various degrees. The tapeworm Diphyllobothrium latum will deplete the body of half its vitamin B 12 resources, which are essential for proper central nervous system function, propagation of nerve impulse, muscle coordination, and recall. When this 30 foot long worm is expelled after proper treatment, above functions will be restored to normality. Host-parasite relationships causing physical or psychological trauma, may be operative at the subclinical level or go undetected since early childhood years. Progressive or sudden overt disease outcome may occur later on in life. This reactivation of infection is usually related to depressed
immune status, age, hormonal changes, and physical or psychological pressures.
Considering the above, it is absolutely important to achieve well being by the elevation of ones physical, mental, emotional, and intuitive energies to a state of balanced and functional equilibrium. Experience demonstrates that antibiotics depress host immunity, kill off beneficial intestinal flora, and enhance fungal growth, e.g., Candida, which subsequently competes with/excludes good bacteria.
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