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Trichinosis, also known as trichinellosis, is a parasitic disease caused by roundworms of the '' Trichinella'' type. During the initial infection, invasion of the intestines can result in
diarrhea Diarrhea, also spelled diarrhoea, is the condition of having at least three loose, liquid, or watery bowel movements each day. It often lasts for a few days and can result in dehydration due to fluid loss. Signs of dehydration often begin w ...
,
abdominal pain Abdominal pain, also known as a stomach ache, is a symptom associated with both non-serious and serious medical issues. Common causes of pain in the abdomen include gastroenteritis and irritable bowel syndrome. About 15% of people have a m ...
, and
vomiting Vomiting (also known as emesis and throwing up) is the involuntary, forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose. Vomiting can be the result of ailments like food poisoning, gastroenter ...
. Migration of
larvae A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. T ...
to muscle, which occurs about a week after being infected, can cause swelling of the face, inflammation of the whites of the eyes,
fever Fever, also referred to as pyrexia, is defined as having a temperature above the normal range due to an increase in the body's temperature set point. There is not a single agreed-upon upper limit for normal temperature with sources using val ...
, muscle pains, and a
rash A rash is a change of the human skin which affects its color, appearance, or texture. A rash may be localized in one part of the body, or affect all the skin. Rashes may cause the skin to change color, itch, become warm, bumpy, chapped, dry, c ...
. Minor infection may be without symptoms. Complications may include inflammation of heart muscle,
central nervous system The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all p ...
involvement, and inflammation of the lungs. Trichinosis is mainly spread when undercooked meat containing ''Trichinella''
cysts A cyst is a closed sac, having a distinct envelope and division compared with the nearby tissue. Hence, it is a cluster of cells that have grouped together to form a sac (like the manner in which water molecules group together to form a bubble) ...
is eaten. In North America this is most often bear, but infection can also occur from pork, boar, and dog meat. Several
species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriat ...
of ''Trichinella'' can cause disease, with ''T. spiralis'' being the most common. After the infected meat has been eaten, the larvae are released from their cysts in the stomach. They then invade the wall of the
small intestine The small intestine or small bowel is an organ (anatomy), organ in the human gastrointestinal tract, gastrointestinal tract where most of the #Absorption, absorption of nutrients from food takes place. It lies between the stomach and large intes ...
, where they develop into adult worms. After one week, the females release new larvae that migrate to voluntarily controlled muscles, where they form cysts. The diagnosis is usually based on symptoms and confirmed by finding specific antibodies in the blood, or larvae on tissue biopsy. The best way to prevent trichinosis is to fully cook meat. A food thermometer can verify that the temperature inside the meat is high enough. Infection is typically treated with antiparasitic medication such as albendazole or mebendazole. Rapid treatment may kill adult worms and thereby stop further worsening of symptoms. Both medications are considered safe, but have been associated with side effects such as bone marrow suppression. Their use during pregnancy or in children under the age of 2 years is poorly studied, but appears to be safe. Treatment with steroids is sometimes also required in severe cases. Without treatment, symptoms typically resolve within three months. Worldwide, about 10,000 infections occur a year. At least 55 countries including the United States, China, Argentina, and Russia have had recently documented cases. While the disease occurs in the tropics, it is less common there. Rates of trichinosis in the United States have decreased from about 400 cases per year in the 1940s to 20 or fewer per year in the 2000s. The risk of death from infection is low.


Signs and symptoms

The great majority of trichinosis infections have either minor or no symptoms and no complications. The two main phases for the infection are enteral (affecting the intestines) and parenteral (outside the intestines). The symptoms vary depending on the phase, species of ''Trichinella'', quantity of encysted larvae ingested, age, sex, and host immunity.


Enteral phase

A large burden of adult worms in the intestines promotes symptoms such as
nausea Nausea is a diffuse sensation of unease and discomfort, sometimes perceived as an urge to vomit. While not painful, it can be a debilitating symptom if prolonged and has been described as placing discomfort on the chest, abdomen, or back of th ...
,
heartburn Heartburn, also known as pyrosis, cardialgia or acid indigestion, is a burning sensation in the central chest or upper central abdomen. Heartburn is usually due to regurgitation of gastric acid (gastric reflux) into the esophagus. It is the ...
, dyspepsia, and
diarrhea Diarrhea, also spelled diarrhoea, is the condition of having at least three loose, liquid, or watery bowel movements each day. It often lasts for a few days and can result in dehydration due to fluid loss. Signs of dehydration often begin w ...
from two to seven days after infection, while small worm burdens generally are asymptomatic.
Eosinophilia Eosinophilia is a condition in which the eosinophil count in the peripheral blood exceeds . Hypereosinophilia is an elevation in an individual's circulating blood eosinophil count above 1.5 x 109/ L (i.e. 1,500/ μL). The hypereosinophilic sy ...
presents early and increases rapidly.


Parenteral phase

The severity of symptoms caused by larval migration from the intestines depends on the number of larvae produced. As the larvae migrate through tissue and vessels, the body's inflammatory response results in
edema Edema, also spelled oedema, and also known as fluid retention, dropsy, hydropsy and swelling, is the build-up of fluid in the body's tissue. Most commonly, the legs or arms are affected. Symptoms may include skin which feels tight, the area ma ...
, muscle pain, fever, and weakness. A classic sign of trichinosis is periorbital edema, swelling around the eyes, which may be caused by
vasculitis Vasculitis is a group of disorders that destroy blood vessels by inflammation. Both arteries and veins are affected. Lymphangitis (inflammation of lymphatic vessels) is sometimes considered a type of vasculitis. Vasculitis is primarily caused ...
.
Splinter hemorrhage Splinter hemorrhages (or haemorrhages) are tiny blood clots that tend to run vertically under the nails. Splinter hemorrhages are not specific to any particular condition, and can be associated with subacute infective endocarditis, scleroderma, tri ...
in the nails is also a common symptom.John D. and William A. Petri. Markell and Voge's Medical Parasitology. 9th ed. Philadelphia: Saunders, 2006. They may very rarely cause enough damage to produce serious neurological deficits (such as
ataxia Ataxia is a neurological sign consisting of lack of voluntary coordination of muscle movements that can include gait abnormality, speech changes, and abnormalities in eye movements. Ataxia is a clinical manifestation indicating dysfunction of ...
or
respiratory paralysis Respiratory failure results from inadequate gas exchange by the respiratory system, meaning that the arterial oxygen, carbon dioxide, or both cannot be kept at normal levels. A drop in the oxygen carried in the blood is known as hypoxemia; a ri ...
) from worms entering the
central nervous system The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all p ...
(CNS), which is compromised by trichinosis in 10–24% of reported cases of
cerebral venous sinus thrombosis Cerebral venous sinus thrombosis (CVST), cerebral venous and sinus thrombosis or cerebral venous thrombosis (CVT), is the presence of a blood clot in the dural venous sinuses (which drain blood from the brain), the cerebral veins, or both. Sympt ...
, a very rare form of stroke (three or four cases per million annual incidence in adults). Trichinosis can be fatal depending on the severity of the infection; death can occur 4–6 weeks after the infection, and is usually caused by
myocarditis Myocarditis, also known as inflammatory cardiomyopathy, is an acquired cardiomyopathy due to inflammation of the heart muscle. Symptoms can include shortness of breath, chest pain, decreased ability to exercise, and an irregular heartbeat. Th ...
,
encephalitis Encephalitis is inflammation of the brain. The severity can be variable with symptoms including reduction or alteration in consciousness, headache, fever, confusion, a stiff neck, and vomiting. Complications may include seizures, hallucinations ...
, or
pneumonia Pneumonia is an inflammatory condition of the lung primarily affecting the small air sacs known as alveoli. Symptoms typically include some combination of productive or dry cough, chest pain, fever, and difficulty breathing. The severit ...
.


Cause

The classical agent is ''T. spiralis'' (found worldwide in many carnivorous and omnivorous animals, both domestic and sylvatic (wild), but seven primarily sylvatic species of ''Trichinella'' also are now recognized:


Species and characteristics

* ''T. spiralis'' is most adapted to swine, most pathogenic in humans, and is cosmopolitan in distribution. * ''T. britovi'' is the second-most common species to infect humans; it is distributed throughout Europe, Asia, and northern and western Africa, usually in wild carnivores, crocodiles, birds, wild boar, and domesticated pigs. * ''T. murrelli'' also infects humans, especially from black bear meat; it is distributed among wild carnivores in North America. * ''T. nativa'', which has a high resistance to freezing, is found in the Arctic and subarctic regions; reservoir hosts include polar bears, Arctic foxes, walruses, and other wild game. * ''T. nelsoni'', found in East African predators and scavengers, has been documented to cause a few human cases. * '' T. papuae'' infects both mammals and reptiles, including crocodiles, humans, and wild and domestic pigs; this species, found in Papua New Guinea and Thailand, is also nonencapsulated. * ''T. pseudospiralis'' infects birds and mammals, and has demonstrated infection in humans; it is a nonencapsulated species. * ''T. zimbabwensis'' can infect mammals, and possibly humans; this nonencapsulated species was detected in crocodiles in Africa.


Taxonomy

* Kingdom: Animalia * Phylum: Nematoda * Class: Adenophorea * Order: Trichurida * Family: Trichinellidae * Genus: ''Trichinella''


Lifecycle

The typical lifecycle for ''T. spiralis'' involves humans, pigs, and rodents. A pig becomes infected when it eats infectious cysts in raw meat, often porcine carrion or a rat ( sylvatic cycle). A human becomes infected by consuming raw or undercooked infected pork (domestic cycle). In the stomach, the cysts from infected undercooked meat are acted on by pepsin and hydrochloric acid, which help release the larvae from the cysts into the stomach. The larvae then migrate to the small intestine, and burrow into the intestinal mucosa, where they molt four times before becoming adults. Thirty to 34 hours after the cysts were originally ingested, the adults mate, and within five days produce larvae. Adult worms can only reproduce for a limited time, because the immune system eventually expels them from the small intestine. The larvae then use their piercing mouthpart, called the "stylet", to pass through the intestinal mucosa and enter the lymphatic vessels, and then enter the bloodstream. The larvae travel by capillaries to various organs, such as the retina, myocardium, or lymph nodes; however, only larvae that migrate to
skeletal muscle Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of m ...
cells survive and encyst. The larval host cell becomes a nurse cell, in which the larva will be encapsulated, potentially for the life of the host, waiting for the host to be eaten. The development of a capillary network around the nurse cell completes encystation of the larva. Trichinosis is not soil-transmitted, as the parasite does not lay eggs, nor can it survive long outside a host.


Diagnosis

Diagnosis of trichinosis is confirmed by a combination of exposure history, clinical diagnosis, and laboratory testing.


Exposure history

An epidemiological investigation can be done to determine a patient's exposure to raw infected meat. Often, an infection arises from home-preparation of contaminated meat, in which case microscopy of the meat may be used to determine the infection. Exposure determination does not have to be directly from a laboratory-confirmed infected animal. Indirect exposure criteria include the consumption of products from a laboratory-confirmed infected animal, or sharing of a common exposure with a laboratory-confirmed infected human.


Clinical diagnosis

Clinical presentation of the common trichinosis symptoms may also suggest infection. These symptoms include eye puffiness,
splinter hemorrhage Splinter hemorrhages (or haemorrhages) are tiny blood clots that tend to run vertically under the nails. Splinter hemorrhages are not specific to any particular condition, and can be associated with subacute infective endocarditis, scleroderma, tri ...
, nonspecific
gastroenteritis Gastroenteritis, also known as infectious diarrhea and gastro, is an inflammation of the gastrointestinal tract including the stomach and intestine. Symptoms may include diarrhea, vomiting, and abdominal pain. Fever, lack of energy, and dehydr ...
, and muscle pain. The case definition for trichinosis at the European Center for Disease Control states, "at least three of the following six:
fever Fever, also referred to as pyrexia, is defined as having a temperature above the normal range due to an increase in the body's temperature set point. There is not a single agreed-upon upper limit for normal temperature with sources using val ...
, muscle soreness and pain, gastrointestinal symptoms, facial
edema Edema, also spelled oedema, and also known as fluid retention, dropsy, hydropsy and swelling, is the build-up of fluid in the body's tissue. Most commonly, the legs or arms are affected. Symptoms may include skin which feels tight, the area ma ...
,
eosinophilia Eosinophilia is a condition in which the eosinophil count in the peripheral blood exceeds . Hypereosinophilia is an elevation in an individual's circulating blood eosinophil count above 1.5 x 109/ L (i.e. 1,500/ μL). The hypereosinophilic sy ...
, and subconjunctival, subungual, and retinal hemorrhages."


Laboratory testing

Blood tests and
microscopy Microscopy is the technical field of using microscopes to view objects and areas of objects that cannot be seen with the naked eye (objects that are not within the resolution range of the normal eye). There are three well-known branches of micr ...
can be used to aid in the diagnosis of trichinosis. Blood tests include a complete blood count for eosinophilia, creatine phosphokinase activity, and various immunoassays such as
ELISA The enzyme-linked immunosorbent assay (ELISA) (, ) is a commonly used analytical biochemistry assay, first described by Eva Engvall and Peter Perlmann in 1971. The assay uses a solid-phase type of enzyme immunoassay (EIA) to detect the presen ...
for larval antigens.


Prevention


Legislation

Laws and rules for food producers may improve food safety for consumers, such as the rules established by the
European Commission The European Commission (EC) is the executive of the European Union (EU). It operates as a cabinet government, with 27 members of the Commission (informally known as "Commissioners") headed by a President. It includes an administrative body ...
for inspections, rodent control, and improved hygiene. A similar protocol exists in the United States, in the
USDA The United States Department of Agriculture (USDA) is the federal executive department responsible for developing and executing federal laws related to farming, forestry, rural economic development, and food. It aims to meet the needs of comme ...
guidelines for farms and slaughterhouse responsibilities in inspecting pork.


Education and training

Public education about the dangers of consuming raw and undercooked meat, especially pork, may reduce infection rates. Hunters are also an at-risk population due to their contact and consumption of wild game, including bear. As such, many states, such as New York, require the completion of a course in such matters before a hunting license can be obtained.


Meat testing

Testing methods are available for both individual carcasses and monitoring of the herds. Artificial digestion method is usually used for the testing of individual carcasses, while the testing for specific antibodies is usually used for herd monitoring.


Food preparation

Larvae may be killed by the heating or irradiation of raw meat. Freezing is normally only effective for ''T. spiralis'', since other species, such as ''T. nativa'', are freeze-resistant and can survive long-term freezing. * All
meat Meat is animal flesh that is eaten as food. Humans have hunted, farmed, and scavenged animals for meat since prehistoric times. The establishment of settlements in the Neolithic Revolution allowed the domestication of animals such as chic ...
(including pork) can be safely prepared by cooking to an internal temperature of or higher for 15 seconds or more. * Wild game: Wild game meat must be cooked thoroughly (see meat preparation above) Freezing wild game does not kill all trichinosis larval worms, because the worm species that typically infests wild game can resist freezing. *
Pork Pork is the culinary name for the meat of the domestic pig (''Sus domesticus''). It is the most commonly consumed meat worldwide, with evidence of pig husbandry dating back to 5000 BCE. Pork is eaten both freshly cooked and preserved ...
: Freezing cuts of pork less than 6 inches thick for 20 days at 5 °F (−15 °C) or three days at −4 °F (−20 °C) kills ''T. spiralis'' larval worms; but this will not kill other trichinosis larval worm species, such as ''T. nativa'', if they have infested the pork food supply (which is unlikely, due to geography). Pork can be safely cooked to a slightly lower temperature, provided that the internal meat temperature is at least as hot for at least as long as listed in the
USDA The United States Department of Agriculture (USDA) is the federal executive department responsible for developing and executing federal laws related to farming, forestry, rural economic development, and food. It aims to meet the needs of comme ...
table below. Nonetheless, allowing a
margin of error The margin of error is a statistic expressing the amount of random sampling error in the results of a survey. The larger the margin of error, the less confidence one should have that a poll result would reflect the result of a census of the e ...
for variation in internal temperature within a particular cut of pork, which may have bones that affect temperature uniformity, is prudent. In addition, kitchen thermometers have measurement error that must be considered. Pork may be cooked for significantly longer and at a higher uniform internal temperature than listed below to be safe. Unsafe and unreliable methods of cooking meat include the use of microwave ovens, curing, drying, and smoking, as these methods are difficult to standardize and control.


Pig farming

Incidence of infection can be reduced by: * Keeping pigs in clean pens, with floors that can be washed (such as concrete) * Not allowing hogs to eat carcasses of other animals, including rats, which may be infected with ''Trichinella'' * Cleaning meat grinders thoroughly when preparing ground meats * Control and destruction of meat containing trichinae, e.g., removal and proper disposal of porcine diaphragms prior to public sale of meat The US
Centers for Disease Control and Prevention The Centers for Disease Control and Prevention (CDC) is the national public health agency of the United States. It is a United States federal agency, under the Department of Health and Human Services, and is headquartered in Atlanta, Georg ...
make the following recommendation: "Curing (salting), drying, smoking, or microwaving meat does not consistently kill infective worms." However, under controlled commercial food processing conditions, some of these methods are considered effective by the USDA. The USDA Animal and Plant Health Inspection Service (APHIS) is responsible for the regulations concerning the importation of swine from foreign countries. The Foreign Origin Meat and Meat Products, Swine section covers swine meat (cooked, cured and dried, and fresh). APHIS developed the National Trichinae Certification Program; this is a voluntary "preharvest" program for U.S. swine producers "that will provide documentation of swine management practices" to reduce the incidence of ''Trichinella'' in swine.USDA Animal and Plant Health Inspection Service APHIS – Veterinary Services. Retrieved February 11, 2009, The CDC reports 0.013% of U.S. swine are infected with ''Trichinella''.


Treatment

As with most diseases, early treatment is better and decreases the risk of developing disease. If larvae do encyst in skeletal muscle cells, they can remain infectious for months to years.


Primary treatment

Early administration of anthelmintics, such as mebendazole or albendazole, decreases the likelihood of larval encystation, particularly if given within three days of infection. However, most cases are diagnosed after this time. In humans, mebendazole (200–400 mg three times a day for three days) or albendazole (400 mg twice a day for 8–14 days) is given to treat trichinosis. These drugs prevent newly hatched larvae from developing, but should not be given to pregnant women or children under two years of age. Medical references from the 1940s described no specific treatment for trichinosis at the time, but intravenous injection of calcium salts was found to be useful in managing symptoms related to severe toxemia from the infection..


Secondary treatment

After infection,
steroids A steroid is a biologically active organic compound with four rings arranged in a specific molecular configuration. Steroids have two principal biological functions: as important components of cell membranes that alter membrane fluidity; and ...
, such as prednisone, may be used to relieve muscle pain associated with larval migration.


Vaccine research

Researchers trying to develop a vaccine for ''Trichinella'' have tried using either "larval extracts, excretory–secretory antigen, DNA, or recombinant antigen protein." Currently, no marketable vaccine is available for trichinosis, but experimental mouse studies have suggested possibilities. * In one study, microwaved ''Trichinella'' larvae were used to immunize mice (orally or intraperitoneally), which were subsequently infected. Depending on the dosage and frequency of immunization, results ranged from a decreased larval count to complete protection from trichinosis. * Another study used extracts and excretory–secretory products from first-stage larvae to produce an oral vaccine. To prevent gastric acids from dissolving the antigens before reaching the small intestine, scientists encapsulated the antigens in microcapsules. This vaccine significantly increased CD4+ cell levels, and increased antigen-specific serum IgGq and IgA, resulting in a statistically significant reduction in the average number of adult worms in the small intestines of mice. The significance of this approach is that, if the white blood cells in the small intestine have been exposed to ''Trichinella'' antigens (through vaccination), when an individual does get infected, the immune system will respond to expel the worms from the small intestine fast enough to prevent the female worms from releasing their larvae. * A DNA vaccine tested on mice "induced a muscle larva burden reduction in BALB/c mice by 29% in response to ''T. spiralis'' infection".


Epidemiology

About 11 million humans are infected with ''Trichinella''; ''T. spiralis'' is the species responsible for most of these infections. Infection was once very common, but this disease is now rare in the developed world, but two known outbreaks occurred in 2015. In the first outbreak, around 40 people were infected in Liguria, Italy, during a New Year's Eve celebration. The second outbreak in France was associated with pork sausages from
Corsica Corsica ( , Upper , Southern ; it, Corsica; ; french: Corse ; lij, Còrsega; sc, Còssiga) is an island in the Mediterranean Sea and one of the 18 regions of France. It is the fourth-largest island in the Mediterranean and lies southeast of ...
, which were eaten raw, affecting 14 people in total. The incidence of trichinosis in the U.S. has decreased dramatically in the past century from an average of 400 cases per year mid-20th century down to an annual average of 20 cases per year (2008–10). The number of cases has decreased because of legislation prohibiting the feeding of raw meat garbage to hogs, increased commercial and home freezing of pork, and the public awareness of the danger of eating raw or undercooked pork products. China reports around 10,000 cases every year, so is the country with the highest number of cases. In China, between 1964 and 1998, over 20,000 people became infected with trichinosis, and more than 200 people died. Trichinosis is common in developing countries where meat fed to pigs is raw or undercooked, but infections also arise in developed countries in Europe where raw or undercooked pork, wild boar and horse meat may be consumed as delicacies. In the
developing world A developing country is a sovereign state with a lesser developed industrial base and a lower Human Development Index (HDI) relative to other countries. However, this definition is not universally agreed upon. There is also no clear agreeme ...
, most infections are associated with undercooked pork. For example, in
Thailand Thailand ( ), historically known as Siam () and officially the Kingdom of Thailand, is a country in Southeast Asia, located at the centre of the Indochinese Peninsula, spanning , with a population of almost 70 million. The country is b ...
, between 200 and 600 cases are reported annually around the
Thai New Year Songkran ( th, เทศกาลสงกรานต์, ) is the Thai New Year's national holiday. Songkran is on 13 April every year, but the holiday period extends from 14 to 15 April. In 2018 the Thai cabinet extended the festival ...
. This is mostly attributable to a particular delicacy, '' larb'', which calls for undercooked pork as part of the recipe. In parts of Eastern Europe, the
World Health Organization The World Health Organization (WHO) is a specialized agency of the United Nations responsible for international public health. The WHO Constitution states its main objective as "the attainment by all peoples of the highest possible level o ...
reports, some swine herds have trichinosis infection rates above 50%, with correspondingly large numbers of human infections.


United States

Historically, pork products were thought to have the most risk of infecting humans with ''T. spiralis''. However, a trichinosis surveillance conducted between 1997 and 2001 showed a higher percentage of cases caused by consumption of wild game (the sylvatic transmission cycle). This is thought to be due to the Federal Swine Health Protection Act (Public Law 96-468) that was passed by Congress in 1980. Prior to this act, swine were fed garbage that could potentially be infected by'' T. spiralis''. This act was put in place to prevent trichinella-contaminated food from being given to swine. Additionally, other requirements were put in place, such as rodent control, limiting commercial swine contact with wildlife, maintaining good hygiene, and removing dead pigs from pens immediately. Between 2002 and 2007, 11 trichinosis cases were reported to the CDC each year on average in the United States, and 2008–10 averaged 20 cases per year; these were mostly the result of consuming undercooked game (sylvatic transmission) or home-reared pigs (domestic transmission).


Religious groups

The
kashrut (also or , ) is a set of dietary laws dealing with the foods that Jewish people are permitted to eat and how those foods must be prepared according to Jewish law. Food that may be consumed is deemed kosher ( in English, yi, כּשר), fr ...
and halal dietary laws of
Judaism Judaism ( he, ''Yahăḏūṯ'') is an Abrahamic, monotheistic, and ethnic religion comprising the collective religious, cultural, and legal tradition and civilization of the Jewish people. It has its roots as an organized religion in th ...
and
Islam Islam (; ar, ۘالِإسلَام, , ) is an Abrahamic monotheistic religion centred primarily around the Quran, a religious text considered by Muslims to be the direct word of God (or '' Allah'') as it was revealed to Muhammad, the ...
prohibit eating pork. In the 19th century, when the association between trichinosis and undercooked pork was first established, this association was suggested to be the reason for the prohibition, reminiscent of the earlier opinion of medieval
Jewish Jews ( he, יְהוּדִים, , ) or Jewish people are an ethnoreligious group and nation originating from the Israelites Israelite origins and kingdom: "The first act in the long drama of Jewish history is the age of the Israelites""The ...
philosopher
Maimonides Musa ibn Maimon (1138–1204), commonly known as Maimonides (); la, Moses Maimonides and also referred to by the acronym Rambam ( he, רמב״ם), was a Sephardic Jewish philosopher who became one of the most prolific and influential Torah ...
that food forbidden by Jewish law was "unwholesome". This theory was controversial, and eventually fell out of favor.


Reemergence

The disappearance of the pathogen from domestic pigs has led to a relaxation of legislation and control efforts by veterinary public health systems. Trichinosis has lately been thought of as a re-emerging
zoonosis A zoonosis (; plural zoonoses) or zoonotic disease is an infectious disease of humans caused by a pathogen (an infectious agent, such as a bacterium, virus, parasite or prion) that has jumped from a non-human (usually a vertebrate) to a human. ...
, supplemented by the increased distribution of meat products, political changes, a changing climate, and increasing sylvatic transmission. Major sociopolitical changes can produce conditions that favor the resurgence of ''Trichinella'' infections in swine and, consequently, in humans. For instance, "the overthrow of the social and political structures in the 1990s" in Romania led to an increase in the incidence rate of trichinosis.Blaga, R., Durand, B., Antoniu, S., Gherman, C., Cretu, C.M., Cozma, V., Boireau, P. (2007). "A dramatic increase in the incidence of human trichinellosis in Romania over the past 25 years: impact of political changes and regional food habits." ''American Journal of Tropical Medicine and Hygiene'', 983–86.


History

As early as 1835, trichinosis was known to have been caused by a parasite, but the mechanism of infection was unclear at the time. A decade later,
American American(s) may refer to: * American, something of, from, or related to the United States of America, commonly known as the "United States" or "America" ** Americans, citizens and nationals of the United States of America ** American ancestry, pe ...
scientist Joseph Leidy pinpointed undercooked meat as the primary vector for the parasite, and two decades afterwards, this hypothesis was fully accepted by the scientific community.


Parasite

The circumstances surrounding the first observation and identification of ''T. spiralis'' are controversial, due to a lack of records. In 1835, James Paget, a first-year medical student, first observed the larval form of ''T. spiralis'', while witnessing an autopsy at St. Bartholomew’s Hospital in London. Paget took special interest in the presentation of muscle with white flecks, described as a "sandy diaphragm". Although Paget is most likely the first person to have noticed and recorded these findings, the parasite was named and published in a report by his professor,
Richard Owen Sir Richard Owen (20 July 1804 – 18 December 1892) was an English biologist, comparative anatomist and paleontologist. Owen is generally considered to have been an outstanding naturalist with a remarkable gift for interpreting fossils. Ow ...
, who is now credited for the discovery of the ''T. spiralis'' larval form.


Lifecycle

A series of experiments conducted between 1850 and 1870 by the German researchers
Rudolf Virchow Rudolf Ludwig Carl Virchow (; or ; 13 October 18215 September 1902) was a German physician, anthropologist, pathologist, prehistorian, biologist, writer, editor, and politician. He is known as "the father of modern pathology" and as the founder ...
, Rudolf Leuckart, and
Friedrich Albert von Zenker Friedrich Albert von Zenker (13 March 1825 – 13 June 1898) was a German pathologist and physician, celebrated for his discovery of trichinosis. He was born in Dresden, and was educated in Leipzig and Heidelberg. While in Leipzig, he worked fo ...
, which involved feeding infected meat to a dog and performing the subsequent necropsy, led to the discovery of the lifecycle of ''Trichinella''. Through these experiments, Virchow was able to describe the development and infectivity of ''T. spiralis''.


Research

The International Commission on Trichinellosis (ICT) was formed in Budapest in 1958. Its mission is to exchange information on the epidemiology, biology, pathophysiology, immunology, and clinical aspects of trichinosis in humans and animals. Prevention is a primary goal. Since the creation of the ICT, its members (more than 110 from 46 countries) have regularly gathered and worked together during meetings held every four years: the International Conference on Trichinellosis.


See also

* List of parasites (human) * Nurse cell


References

* ''The text of the original version of this article was taken from the public domain resource at https://www.cdc.gov/ncidod/dpd/parasites/trichinosis/factsht_trichinosis.htm'' *
Centers for Disease Control and Prevention The Centers for Disease Control and Prevention (CDC) is the national public health agency of the United States. It is a United States federal agency, under the Department of Health and Human Services, and is headquartered in Atlanta, Georg ...
. Trichinosis Surveillance, United States, 1987–1990, MMWR 1991;40:(SS-3)35-42. *
USDA regulations – Title 9 – Chapter 3 – Part 318 – includes "Prescribed treatment of pork and products containing pork to destroy trichinae."


External links





* {{Helminthiases Parasitic infestations, stings, and bites of the skin Conditions diagnosed by stool test Foodborne illnesses Rodent-carried diseases Helminthiases Zoonoses Animal diseases Parasitic nematodes of humans Parasitic nematodes of mammals Parasitic diseases associated with beef and pork consumption Wikipedia medicine articles ready to translate Wikipedia infectious disease articles ready to translate