Trichinosis (or trichinellosis) is caused by eight different species of round worm in the genus Trichinella. These parasites can be found in animals on all continents but Antarctica. Artic bears harbor a species of Trichinella that is resistant to freezing for reasons yet to be discovered. Recently a species of Trichinella has been discovered in East African reptiles, notably crocodiles. Carnivorous animals and humans acquire these nematodes (flat worms) by eating raw or undercooked meat and meat products of other animals, particularly pigs, horses, and wild game. The most reliable method of prevention is to cook meat thoroughly before eating.
Once consumed from the diet, the worms migrate from the intestines to the muscles. Symptoms are usually so mild that the diagnosis is missed, but they can include stomach upset, diarrhea, constipation, eyelid swelling, and fever. Muscle pain due to the inflammation caused by chemicals the worms secrete can appear as early as one to two days after ingestion of contaminated meat. Later symptoms appear within two to eight weeks, when the worms have migrated into the muscles. Breathing may be difficult if the diaphragm muscle is involved. The heart, brain, eyes, and lungs may be involved in more serious infections. Most symptoms disappear within three months, but vague muscle pains may last for longer periods of time. Severe infections may cause death.
The interaction of the Trichinella organism and its infected host is highly complex. The worm secretes a variety of chemicals that induce changes in the host cells. Some of these changes allow the worm to migrate from the gut to the muscles. Other chemicals cause the muscle cells to produce a capsule around the worm. Still others cause an inflammatory reaction in muscles. Discovering these chemicals will help researchers in understanding disease mechanisms in other infections as well.
According to the World Health Organization, the global prevalence of trichinosis is about 10 million infected individuals. Most of these are in the developing world where meat inspection and controls are absent and cooking practices are less standardized. In the United States, there has been an average of 12 cases per year. Despite a century of veterinary public health efforts to control and eradicate it, however, trichinosis has experienced a dramatic re-emergence worldwide over the past 10 to 20 years. The reasons for this re-emergence are diverse and include human interference with ecosystems, war and political turmoil, rapidly changing food distribution and marketing systems, and rising affluence in developing countries.
Individuals who eat raw or undercooked meats, particularly bear, pork, wild feline (such as a cougar), fox, dog, wolf, horse, seal, or walrus are at risk for trichinosis. Meat from developing countries should be considered suspect and should be thoroughly cooked.
North Americans generally need not be too concerned about trichinosis beyond cooking meats thoroughly. This practice alone will reduce the increasing threat of contaminated meats from foreign suppliers. However, nations such as China that are experiencing new affluence and consuming more meat in their diets need to be very cautious to avoid this disease.
Worldwide prevalence of trichinosis is about 10 million infected individuals. Most of these are in the developing world where meat inspection and controls are absent and cooking practices are less standardized. In the United States, there has been an average of 12 cases per year. During the last 10 to 20 years, however, trichinosis has experienced a dramatic re-emergence worldwide due to human interference with ecosystems, war and political turmoil, rapidly changing food distribution and marketing systems, and rising affluence in developing countries.
Trichinosis is caused by eight different species of round worm in the genus Trichinella. These parasites can be found in animals on all continents but Antarctica. Artic bears harbor a species of Trichinella that is resistant to freezing for reasons yet to be discovered. Recently a species of Trichinella has been discovered in East African reptiles, notably crocodiles. Carnivorous animals and humans acquire these nematodes (flat worms) by eating raw or undercooked meat and meat products of other animals, particularly pigs, horses, and wild game.
SIGNS AND SYMPTOMS
Once consumed from the diet, the worms migrate from the intestines to the muscles. Symptoms are usually so mild that the diagnosis is missed. Initial symptoms may include nausea, diarrhea, vomiting, fatigue, fever, and stomach upset. Later symptoms may include diarrhea or constipation, headache, cough, aching joints, muscle pains, itchy skin, and eyelid swelling.
Muscle pain due to the inflammation caused by chemicals the worms secrete can appear as early as one to two days after eating contaminated meat. Later symptoms appear within two to eight weeks, when the worms have migrated into the muscles. Breathing may be difficult if the diaphragm muscle is involved. The heart, brain, eyes, and lungs may be involved in more serious infections.
Most symptoms disappear within three months, but vague muscle pains may last for longer periods of time. More serious infections may cause patients to have difficulty with coordination as well as heart and breathing problems. Fatigue, weakness, and diarrhea may last for months. Severe infections may cause death.
Diagnosis of trichinosis is generally made based on the presence of classic signs and symptoms, including swelling around the eyes, muscle inflammation, and fever. Many different diseases have symptoms similar to those for trichinosis, so doctors must be careful in order to achieve the correct diagnosis.
Trichinosis can be diagnosed by several types of blood tests that identify antibodies to Trichinella as well as an increase in a certain type of blood cell (eosinophil).
A muscle biopsy can identify the presence of the worms. In a biopsy, a piece of tissue is surgically removed from the body and examined for Trichinella larvae under a microscope in a laboratory.
The interaction of the Trichinella organism and its infected host is highly complex. The worm secretes a variety of chemicals that induces changes in the host cells. Some of these changes allow the worm to migrate from the gut to the muscles. Other chemicals cause the muscle cells to produce a capsule around the worm. Still others cause an inflammatory reaction in the muscle. Discovering these chemicals will help researchers in understanding disease mechanisms in other infections as well.
Treatment for trichinosis should begin as soon as possible. Treatment with thiabendazole, mebendazole, or albendazole eliminates only the intestinal infection. No drug yet developed affects the worms in muscles. These drugs are effective for many different types of worms. They work by inhibiting the ability of the worms to utilize glucose and essentially starve them. The drugs currently used to treat trichinosis have generally been found to be safe. Rare side effects include gastrointestinal upset and allergic reactions.
Note: Currently there is insufficient evidence available on the safety and effectiveness of integrative therapies for the prevention or treatment of trichinellosis. The therapies below have been studied for their effect on infections in general, should be used only under the supervision of a qualified healthcare provider, and should not be used in replacement of other proven therapies.
Good scientific evidence:
Probiotics: Probiotics are beneficial bacteria (sometimes referred to as "friendly germs") that help to maintain the health of the intestinal tract and aid in digestion. Limited evidence with day care children suggests that supplementation with Lactobacillus GG may reduce the number of sick days, frequency of respiratory tract infections, and frequency of related antibiotic treatments. Fermented milk (with yogurt cultures and L. casei DN-114001) may reduce the duration of winter infections (gastrointestinal and respiratory), as well as average body temperature, in elderly people. Probiotics are generally considered safe and well-tolerated. Avoid if allergic or hypersensitive to probiotics. Use cautiously if lactose intolerant.
Unclear or conflicting scientific evidence:
Oregano: Early study shows that taking oregano by mouth may help treat parasites. Further research is needed to confirm these results. Avoid in individuals with a known allergy or hypersensitivity to oregano. Based on historical use, it appears that oregano is well tolerated in recommended doses. However, reliable clinical trials demonstrating safety or efficacy of a particular dose or for a recommended treatment duration are currently lacking in the available literature. Oregano may lower blood sugar levels. Caution is advised in patients with diabetes or hypoglycemia, and in those taking drugs, herbs, or supplements that affect blood sugar. Serum glucose levels may need to be monitored by a healthcare provider, and medication adjustments may be necessary. Oregano is not recommended at doses above those normally found in food during pregnancy and lactation due to a lack of available scientific evidence.
Prayer: Prayer can be defined as a "reverent petition," the act of asking for something while aiming to connect with God or another object of worship. Prayer on behalf of the ill or dying has played a prominent role throughout history and across cultures. Prayer may help reduce the length of hospital stay as well as the duration of fever in patients with infections. However, early study is controversial and additional study is needed before a conclusion can be drawn. Prayer is not recommended as the sole treatment approach for potentially serious medical conditions, and should not delay the time it takes to consult with a healthcare professional or receive established therapies. Sometimes religious beliefs come into conflict with standard medical approaches, and require an open dialog between patients and caregivers. Based on one clinical study, patients certain that they were receiving intercessory prayer had a higher incidence of complications following cardiac bypass surgery than those who did not know they were being prayed for.
Propolis: Bees create propolis, a natural resin, to build their hives. Propolis is made from the buds of conifer and poplar trees, beeswax, and other bee secretions. Animal and laboratory studies suggest that propolis may help treat various types of infections. Initial human research reports possible benefits against bacteria in the mouth, genital herpes, urine bacteria, intestinal giardia infections, or H. pylori. Additional research is needed before a recommendation can be made. Avoid if allergic or hypersensitive to propolis, black poplar (Populas nigra), poplar bud, bee stings, bee products, honey, and Balsam of Peru. Severe allergic reactions have been reported. Use cautiously with asthma or gastrointestinal disorders. Avoid if pregnant or breastfeeding because of the high alcohol content in some propolis products.
Selenium: Selenium is a trace mineral found in soil, water, and some foods. It is an essential element in several metabolic pathways. Preliminary research reports that selenium can be beneficial in the prevention of several types of infection, including recurrence of erysipelas (bacterial skin infection associated with lymphedema), sepsis, or Mycoplasma pneumonia. Selenium may help prevent infection by stimulating immune function. Further research is needed to confirm these results before a clear recommendation can be made. Avoid if allergic or sensitive to products containing selenium. Avoid with history of nonmelanoma skin cancer. Selenium is generally regarded as safe for pregnant or breastfeeding women. However, animal research reports that large doses of selenium may lead to birth defects.
Trichinosis is easily prevented by eating only well-cooked meat. Meat should be cooked until the juices run clear or to an internal temperature of 170o. Freezing meat less than 6 inches thick for three weeks at 5oF or for six days at -20oF may, but is not guaranteed to, kill all worms.
Meat from wild game should be cooked thoroughly. Freezing meat from wild game may not kill all worms. All meat fed to pigs or other wild animals should be thoroughly cooked.
Meat grinders should be cleaned thoroughly. Curing, drying, smoking, or microwaving meat does not necessarily kill all worms.
Agricultural inspectors in many countries routinely inspect for Trichinella in meat products so that it is not distributed to grocery stores. The standard method is to examine muscle tissue from an animal under a microscope and look for the worms. It may not be long before genetic methods are used, but they are not in commercial use at the present time. Not very long ago the practice of feeding farm animals uncooked animal products was outlawed. This was done to prevent mad cow disease more than to prevent trichinosis.
Very little is currently known about the molecular interactions between Trichinella species and human or animal hosts. What chemicals the worms secrete and how they cause changes in the host tissues are appropriate subjects for study with new techniques in molecular biology. Uncovering this data will help to create a greater understanding of many infectious and immune processes.
Researchers hope that further understanding of the molecular basis of Trichinella infection will lead to development of new drugs, including drugs that will treat the muscle phase, but nothing has yet appeared. Molecular biology may also uncover new tools to identify patients who have the disease. These will take the form of more specific and easier-to-use laboratory tests for molecules unique to the Trichinella species or to the body's immune reaction to the infection.
On a less technologic basis, researchers also seek to identify social and economic trends that spread the disease, such as increasing affluence in developing countries that allows people to consume more meat products.
Future research will proceed along current directions, which include identifying the chemicals secreted by Trichinella and how they affect host tissues, identifying target molecules in Trichinella that may be susceptible to pharmaceutical interventions, and seeking ways to interrupt the worm's life cycle in host animals before they enter the food chain. Efforts are currently in progress to map the entire genome (all the genes) of Trichinella species as a database from which to explore its functions.
Transcriptomics, proteomics, and genomics are new techniques in molecular biology whereby the precise nature of genes, enzymes, and other molecules in cells are identified and their actions are better understood. Every infectious organism is in some way unique in how it damages its host and causes disease and currently, little is known about the mechanics of infection. Future research aims to develop new diagnostic tools to gain a better understanding in this area.
This information has been edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (www.naturalstandard.com).
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