View source for Trichinosis

{{short description|Parasitic disease caused by roundworms}}
{{cs1 config|name-list-style=vanc}}
{{about|the disease|the parasite|Trichinella}}
{{distinguish|Trichomoniasis|Trichuriasis}}
{{Infobox medical condition (new)
| name            = Trichinosis
| image           = Trichinella HBb.jpg
| caption         = Trichinella [[larvae]] in pressed bear meat, partially digested with [[pepsin]]. The classic coil shape is visible.
| field           = [[Infectious disease (medical specialty)|Infectious disease]]
| synonyms        = Trichinellosis, trichiniasis
| symptoms        = '''Initially''': [[diarrhea]], [[abdominal pain]], [[vomiting]]<ref name=CDC2013DP/><br />'''Later''': [[edema|swelling]] of the face, [[conjunctivitis|inflammation of the whites of the eyes]], [[fever]], [[myalgia|muscle pains]], [[rash]]<ref name=CDC2013DP/>
| complications   = [[myocarditis|Inflammation of heart muscle]], [[pneumonitis|inflammation of the lungs]]<ref name=CDC2013DP/>
| onset           =
| duration        =
| types           =
| causes          = ''[[Trichinella]]'' from eating undercooked meat<ref name=CDC2013DP/>
| risks           =
| diagnosis       = [[serology|Antibodies in the blood]], larvae on [[tissue biopsy]]<ref name=CDC2013DP/>
| differential    = [[Measles]], [[dermatomyositis]], [[gastroenteritis]]<ref>{{cite book|last1=Ferri|first1=Fred F.|title=Ferri's differential diagnosis : a practical guide to the differential diagnosis of symptoms, signs, and clinical disorders|date=2010|publisher=Elsevier/Mosby|location=Philadelphia, PA|isbn=978-0323076999|chapter=Chapter T|edition=2nd}}</ref>
| prevention      = Fully cooking meat<ref name=CDC2013Pre/>
| treatment       =
| medication      = [[Albendazole]], [[mebendazole]]<ref name=CDC2013Tx/>
| prognosis       = Low risk of death<ref name=Mason2014/>
| frequency       = ~10,000 cases a year<ref name=CDC2012Epi/>
| deaths          =
}}
<!-- Definitions and symptoms -->
'''Trichinosis''', also known as '''trichinellosis''', is a [[parasitic disease]] caused by [[nematodes|roundworms]] of the ''[[Trichinella]]'' genus.<ref name=CDC2013DP/> During the initial infection, invasion of the [[intestines]] can result in [[diarrhea]], [[abdominal pain]], and [[vomiting]].<ref name=CDC2013DP/> Migration of [[larvae]] to muscle, which occurs about a week after being infected, can cause [[edema|swelling]] of the face, [[conjunctivitis|inflammation of the whites of the eyes]], [[fever]], [[muscle pains]], and a [[rash]].<ref name=CDC2013DP/> Minor infection may be [[asymptomatic|without symptoms]].<ref name=CDC2013DP/> Complications may include [[myocarditis|inflammation of heart muscle]], [[central nervous system]] involvement, and [[pneumonitis|inflammation of the lungs]].<ref name=CDC2013DP>{{Cite web|title = CDC – DPDx – Trichinellosis – index|url = https://www.cdc.gov/dpdx/trichinellosis/index.html|website = www.cdc.gov|access-date = 2015-07-19|url-status = live|archive-url = https://web.archive.org/web/20150704215541/http://www.cdc.gov/dpdx/trichinellosis/index.html|archive-date = 2015-07-04}}</ref>

<!-- Cause and diagnosis -->
Trichinosis is mainly spread when undercooked meat containing ''Trichinella'' [[Microbial cyst|cysts]] is eaten.<ref name=CDC2013DP/> Wild meat is more likely to contain the parasite.<ref>{{cite journal | pmc=2620635 | date=2009 | title=Epidemiology, Diagnosis, Treatment, and Control of Trichinellosis | journal=Clinical Microbiology Reviews | volume=22 | issue=1 | pages=127–145 | doi=10.1128/CMR.00026-08 | pmid=19136437 | vauthors = Gottstein B, Pozio E, Nöckler K }}</ref><ref>{{Cite web |title=Trichinosis Fact Sheet |url=https://www.health.ny.gov/diseases/communicable/trichinosis/fact_sheet.htm |access-date=2025-01-17 |website=www.health.ny.gov}}</ref> In North America this is most often bear, but infection can also occur from pork, boar, and dog meat.<ref>{{cite book|last1=Cook|first1=Gordon Charles|last2=Zumla|first2=Alimuddin|title=Manson's Tropical Diseases|date=2009|publisher=Elsevier Health Sciences|isbn=978-1416044703|page=325|url=https://books.google.com/books?id=CF2INI0O6l0C&pg=PA325|language=en}}</ref> Several [[species]] of ''Trichinella'' can cause disease, with [[Trichinella spiralis|''T. spiralis'']] being the most common.<ref name=CDC2013DP/> After the infected meat has been eaten, the larvae are released from their cysts in the stomach.<ref name=CDC2013DP/> They then invade the wall of the [[small intestine]], where they develop into adult worms.<ref name=CDC2013DP/> After one week, the females release new larvae that migrate to [[Striated muscle tissue|voluntarily controlled muscles]], where they form cysts.<ref name=CDC2013DP/> The diagnosis is usually based on symptoms and confirmed by finding specific [[serology|antibodies in the blood]], or larvae on [[tissue biopsy]].<ref name=CDC2013DP/>

<!-- Prevention and treatment -->
The best way to prevent trichinosis is to fully cook meat.<ref name=CDC2013Pre/> A [[food thermometer]] can verify that the temperature inside the meat is high enough.<ref name=CDC2013Pre>{{Cite web|title = CDC – Trichinellosis – Prevention & Control|url = https://www.cdc.gov/parasites/trichinellosis/prevent.html|website = www.cdc.gov|access-date = 2015-07-25|url-status = live|archive-url = https://web.archive.org/web/20150924143550/http://www.cdc.gov/parasites/trichinellosis/prevent.html|archive-date = 2015-09-24}}</ref> Infection is typically treated with antiparasitic medication such as [[albendazole]] or [[mebendazole]].<ref name=CDC2013Tx/> Rapid treatment may kill adult worms and thereby stop further worsening of symptoms.<ref name=CDC2013Tx/> Both medications are considered safe but have been associated with side effects such as [[bone marrow suppression]].<ref name=CDC2013Tx/> Their use during pregnancy or in children under the age of 2 years is poorly studied but appears to be safe.<ref name=CDC2013Tx/> Treatment with steroids is sometimes also required in severe cases.<ref name=CDC2013Tx>{{Cite web|title = CDC – DPDx – Trichinellosis – Treatment Information|url = https://www.cdc.gov/dpdx/trichinellosis/tx.html|website = www.cdc.gov|access-date = 2015-07-25|url-status = live|archive-url = https://web.archive.org/web/20150822005717/http://www.cdc.gov/dpdx/trichinellosis/tx.html|archive-date = 2015-08-22}}</ref> Without treatment, symptoms typically resolve within three months.<ref name=Mason2014/>

<!--Epidemiology and history -->
Worldwide, about 10,000 trichinosis infections occur a year.<ref name=CDC2012Epi/> At least 55 countries including the United States, China, Argentina, and Russia have had recently documented cases.<ref name=Mason2014/> While trichinosis does occur in the tropics, it is actually less common there.<ref name=Mason2014/> 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.<ref name=CDC2012Epi>
{{cite web|url=https://www.cdc.gov/parasites/trichinellosis/epi.html|title=Trichinellosis Fact Sheet – Division of Parasitic Diseases|publisher=Centre for Disease Control, US Government|date=August 2012|access-date=2016-06-05|url-status=live|archive-url=https://web.archive.org/web/20160522054953/http://www.cdc.gov/parasites/trichinellosis/epi.html|archive-date=2016-05-22|quote=During 2008–2010, 20 cases were reported to CDC each year on average.}}</ref><ref name=ElevenCases>{{cite web |url=https://www.cdc.gov/parasites/trichinellosis/epi.html |title=Trichinellosis Epidemiology & Risk Factor |access-date=2020-03-06 |url-status=live |archive-url=https://web.archive.org/web/20101220112222/http://www.cdc.gov/parasites/trichinellosis/epi.html |archive-date=2010-12-20 |quote=During 2002–2007, 11 cases were reported to CDC each year on average.}}</ref> The risk of death from infection is low.<ref name=Mason2014>{{cite book|last1=Farrar|first1=Jeremy|title=Manson's tropical diseases.|date=2013|publisher=Saunders [Imprint]|location=Philadelphia|isbn=978-0-7020-5101-2|pages=791–94|edition=23}}</ref>
{{TOC limit|3}}

==Signs and symptoms==
The great majority of trichinosis infections have either minor or no symptoms and no complications.<ref>{{cite web |url=http://www.medicinenet.com/trichinosis/page3.htm |title=11 Symptoms of Trichinosis, Transmission, Treatment, Life Cycle & Cure |access-date=2008-12-25 |url-status=live |archive-url=https://web.archive.org/web/20081218073239/http://www.medicinenet.com/trichinosis/page3.htm |archive-date=2008-12-18 }}</ref> 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'', the quantity of encysted larvae ingested, age, sex, and host immunity.<ref name="five"/>

===Enteral phase===
A large burden of adult worms in the intestines promotes symptoms such as [[nausea]], [[heartburn]], [[dyspepsia]], and [[diarrhea]] from two to seven days after infection, while small worm burdens generally are asymptomatic. [[Eosinophilia]] presents early and increases rapidly.<ref>{{cite journal |vauthors=Bruschi F, Murrell KD |year=2002 |title=New aspects of human trichinellosis: the impact of new ''Trichinella'' species |journal=Postgraduate Medical Journal |volume=78 |issue= 915|pages=15–22 |doi=10.1136/pmj.78.915.15|pmid=11796866 |pmc=1742236}}</ref>

===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]], muscle pain, fever, and weakness. A classic sign of trichinosis is [[periorbital edema]], swelling around the eyes, which may be caused by [[vasculitis]]. [[Splinter hemorrhage]] in the nails is also a common symptom.<ref name=eight>John D. and William A. Petri. Markell and Voge's Medical Parasitology. 9th ed. Philadelphia: Saunders, 2006.</ref>

They may very rarely cause enough damage to produce serious neurological deficits (such as [[ataxia]] or [[respiratory paralysis]]) from worms entering the [[central nervous system]] (CNS), which is compromised by trichinosis in 10–24% of reported cases of [[cerebral venous sinus thrombosis]], a very rare form of stroke (three or four cases per million annual incidence in adults).<ref name=sixteen>{{cite journal |last1=Evans |first1=R. W. |last2=Patter |first2=B. M. | year = 1982 | title = Trichinosis associated with superior sagittal sinus thrombosis | journal = Annals of Neurology | volume = 11 | issue = 2| pages = 216–17 | doi=10.1002/ana.410110225 | pmid=7073258|s2cid=32598996 }}</ref> Trichinosis can be fatal depending on the severity of the infection; death can occur 4–6 weeks after the infection,<ref name="two"/> and is usually caused by [[myocarditis]], [[encephalitis]], or [[pneumonia]].<ref name="three">{{cite journal | author = Pozio E | date = Dec 2002 | title = Trichinella zimbabwensis n.sp. (Nematoda), a new non-encapsulated species from crocodiles (Crocodylus niloticus) in Zimbabwe also infecting mammals | journal = Int J Parasitol | volume = 32 | issue = 14| pages = 1787–99 | pmid = 12464425 | doi=10.1016/s0020-7519(02)00139-x|display-authors=etal}}</ref>

==Cause==
[[Image:Trichinella larvaeD.jpg|thumb|''Trichinella spiralis'' [[larvae]] in muscle tissue]]
[[File:Trichinella Spiralis x.s. & l.s. 40x.png|thumb|Animal tissue infected with the parasite that causes the disease trichinosis: Most parasites are shown in cross-section, but some randomly appear in long section.]]

The classical agent is ''T. spiralis'' (found worldwide in many carnivorous and omnivorous animals, both domestic and [[sylvatic]] (wild),{{citation needed|date=January 2023}} but seven primarily sylvatic species of ''Trichinella'' also are now recognized:

===Species and characteristics===
* [[Trichinella spiralis|''T. spiralis'']] is most adapted to swine, most pathogenic in humans, and is cosmopolitan in distribution.{{citation needed|date=January 2021}}
* [[Trichinella britovi|''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.{{citation needed|date=January 2021}}
* ''T. murrelli'' also infects humans, especially from black bear meat; it is distributed among wild carnivores in North America.<ref>{{Cite journal|last1=Scandrett|first1=Brad|last2=Konecsni|first2=Kelly|last3=Lalonde|first3=Laura|last4=Boireau|first4=Pascal|last5=Vallée|first5=Isabelle|date=June 2018|title=Detection of natural Trichinella murrelli and Trichinella spiralis infections in horses by routine post-slaughter food safety testing|journal=Food and Waterborne Parasitology|volume=11|pages=1–5|doi=10.1016/j.fawpar.2018.06.001 |pmc=7033993|pmid=32095599}}</ref>
* [[Trichinella nativa|''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.<ref>{{cite book |doi=10.1006/rwfm.1999.1595 |chapter=Trichinella |title=Encyclopedia of Food Microbiology |date=1999 |pages=2181–2186 |isbn=978-0-12-227070-3 | vauthors = Gamble HR }}</ref>
* ''T. nelsoni'', found in East African predators and scavengers, has been documented to cause a few human cases.
* ''[[Trichinella papuae|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.<ref name=":0">{{Cite web|title = CDC – DPDx – Trichinellosis – index|url = https://www.cdc.gov/dpdx/trichinellosis/index.html|website = www.cdc.gov|access-date = 2015-07-25|url-status = live|archive-url = https://web.archive.org/web/20150704215541/http://www.cdc.gov/dpdx/trichinellosis/index.html|archive-date = 2015-07-04}}</ref>
* ''T. pseudospiralis'' infects birds and mammals, and has demonstrated infection in humans;<ref>{{cite journal | author = Jongwutiwes S | date = Jan 1998 | title = First outbreak of human trichinellosis caused by Trichinella pseudospiralis | journal = Clin Infect Dis | volume = 26 | issue = 1| pages = 111–15 | doi=10.1086/516278| pmid = 9455518 |display-authors=etal| doi-access = free }}</ref> it is a nonencapsulated species.
* ''T. zimbabwensis'' can infect mammals, and possibly humans; this nonencapsulated species was detected in crocodiles in Africa.<ref name=CDC2013DP/>

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

===Lifecycle===
[[File:Trichinella LifeCycle.gif|thumb|upright=1.4|Lifecycle of ''Trichinella spiralis'']]

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 [[cyst]]s from infected undercooked meat are acted on by [[pepsin]] and [[hydrochloric acid]], which help release the larvae from the cysts into the [[stomach]].<ref name=five>{{cite journal |author1=Capo, V. |author2=Despommier, D. D. |date=1996 |title=Clinical Aspects of Infection with ''Trichinella spp.'' |journal=Clinical Microbiology Reviews |volume=9 |issue=1 |pages=47–54 |doi=10.1128/cmr.9.1.47|pmid=8665476 |pmc=172881 }}</ref> The larvae then migrate to the [[small intestine]], and burrow into the [[intestinal mucosa]], where they molt four times before becoming adults.<ref name=five/>

Thirty to 34 hours after the cysts were originally ingested, the adults mate, and within five days produce larvae.<ref name="five"/> Adult worms can only reproduce for a limited time because the [[immune system]] eventually expels them from the small intestine.<ref name="five"/> The larvae then use their piercing mouthpart, called the "stylet", to pass through the [[Gastrointestinal wall|intestinal mucosa]] and enter the [[lymphatic vessel]]s, and then enter the [[Circulatory system|bloodstream]].<ref name="four"/>

The larvae travel by [[Capillary|capillaries]] to various organs, such as the [[retina]], [[Cardiac muscle|myocardium]], or [[lymph node]]s; however, only larvae that migrate to [[skeletal muscle]] cells survive and [[Microbial cyst|encyst]].<ref name="two"/> 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 [[Parasitism|parasite]] does not lay eggs, nor can it survive long outside a host.<ref name=Mason2014/><ref>{{cite journal |title=Epidemiology, diagnosis, treatment, and control of trichinellosis |journal=Clinical Microbiology Reviews |date=January 2009 |pmc=2620635 |pmid=19136437 |pages=127–45, Table of Contents|volume=22 |issue=1 |doi=10.1128/CMR.00026-08 |first1=Bruno |last1=Gottstein |first2=Edoardo |last2=Pozio |first3=Karsten |last3=Nöckler}}</ref>

==Diagnosis==
Diagnosis of trichinosis is confirmed by a combination of exposure history, clinical diagnosis, and laboratory testing.{{citation needed|date=January 2021}}

===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.<ref name=two>{{cite journal | author = Gottstein B | year = 2009 | title = Epidemiology, Diagnosis, Treatment, and Control of Trichinellosis | journal = Clinical Microbiology Reviews | volume = 22 | issue = 1| pages = 127–45 | doi=10.1128/cmr.00026-08|display-authors=etal | pmid=19136437 | pmc=2620635}}</ref>

===Clinical diagnosis===
Clinical presentation of the common trichinosis symptoms may also suggest infection. These symptoms include eye puffiness, [[splinter hemorrhage]], nonspecific [[gastroenteritis]], and muscle pain.<ref name="two"/> The case definition for trichinosis at the European Center for Disease Control states, "at least three of the following six: [[fever]], muscle soreness and pain, [[gastrointestinal symptom]]s, facial [[edema]], [[eosinophilia]], and subconjunctival, subungual, and retinal [[hemorrhages]]."<ref name="two"/>

===Laboratory testing===
Blood tests and [[microscopy]] 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]] for larval antigens.<ref name="two"/>

In some cases, muscle biopsies are performed, where "0.2 to 0.5 grams of human or animal skeletal muscle tissue is collected and examined for Trichinella larvae via artificial digestion or histological analysis."<ref>{{Cite web |last=CDC |date=2024-05-22 |title=Clinical Overview of Trichinellosis |url=https://www.cdc.gov/trichinellosis/hcp/clinical-overview/index.html |access-date=2025-01-17 |website=Trichinellosis (Trichinosis) |language=en-us}}</ref>

==Prevention==

===Legislation===
Laws and rules for food producers may improve food safety for consumers, such as the rules established by the [[European Commission]] for inspections, rodent control, and improved hygiene.<ref name="two"/> A similar protocol exists in the United States, in the [[USDA]] guidelines for farms and slaughterhouse responsibilities in inspecting pork.<ref>United States Department of Agriculture – Food Safety and Inspection Service. "NSS NRTE/RTE Establishment Responsibilities." (2006).</ref>

===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 bears. As such, many states, such as New York, require the completion of a course in such matters before a hunting license can be obtained.<ref>New York State Department of Environmental Conservation – Hunting Licenses <www.dec.ny.gov/permits/6094.html></ref>

===Meat testing===
Testing methods are available for both individual carcasses and monitoring of the herds.<ref name=MIAC>{{cite book |title=Meat Inspection and Control |editor1=Thimjos Ninios |editor2=Janne Lundén |editor3=Hannu Korkeala |editor4=Maria Fredriksson-Ahomaa |date=2014 |publisher=Wiley Blackwell |page=210 |url=https://books.google.com/books?id=yTNuDwAAQBAJ&pg=PA210|isbn=9781118525869 }}</ref> Artificial digestion method is usually used for the testing of individual carcasses, while the testing for specific antibodies is usually used for herd monitoring.<ref name=MIAC/>

===Food preparation===
Larvae may be killed by the heating or [[Food irradiation|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.<ref name="two"/>
* All [[meat]] (including pork) can be safely prepared by cooking to an internal temperature of {{convert|165|F}} or higher for 15 seconds or more.<ref>{{Cite web |title=Trichinosis Fact Sheet - MN Dept. of Health |url=https://www.health.state.mn.us/diseases/trichinosis/trichinosis.html#dx |access-date=2025-01-17 |website=www.health.state.mn.us}}</ref>
* 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.{{citation needed|date=January 2023}}
* [[Pork]]: Freezing cuts of pork less than 6&nbsp;inches thick for 20 days at 5&nbsp;°F (−15&nbsp;°C) or three days at −4&nbsp;°F (−20&nbsp;°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).<ref>{{Cite web |title=Trichinosis Fact Sheet - MN Dept. of Health |url=https://www.health.state.mn.us/diseases/trichinosis/trichinosis.html#NaN |access-date=2025-01-17 |website=www.health.state.mn.us}}</ref>

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]] table below.<ref name="USDA Title 9 section 318.10 Table">{{Cite web|url=https://www.govinfo.gov/content/pkg/CFR-2001-title9-vol2/pdf/CFR-2001-title9-vol2-sec318-10.pdf|title=USDA Title 9 section 318.10 Table}}</ref> Nonetheless, allowing a [[margin of error]] 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 errors that must be considered. Pork may be cooked for significantly longer and at a higher uniform internal temperature than listed below to be safe.<ref>{{Cite web |last=Hendrick |first=Bill |title=USDA Revises Cooking Temperatures for Pork |url=https://www.webmd.com/food-recipes/news/20110525/cooking-temperatures-for-pork |access-date=2022-05-06 |website=WebMD |language=en}}</ref>

{| class="wikitable"
|-
! Internal Temperature
! Internal Temperature
! Minimum Time
|-
|-
! (°[[Fahrenheit|F]])
! (°[[Celsius|C]])
! (minutes)
|-
| 120
| 49
| 1260
|-
| 122
| 50.0
| 570
|-
| 124
| 51.1
| 270
|-
| 126
| 52.2
| 120
|-
| 128
| 53.4
| 60
|-
| 130
| 54.5
| 30
|-
| 132
| 55.6
| 15
|-
| 134
| 56.7
| 6
|-
| 136
| 57.8
| 3
|-
| 138
| 58.9
| 2
|-
| 140
| 60.0
| 1
|-
| 142
| 61.1
| 1
|-
| 144
| 62.2
| Instant
|}<ref name="USDA Title 9 section 318.10 Table"/>

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.<ref name="two"/>

===Pig farming===
Incidence of infection can be reduced by:{{citation needed|date=January 2021}}
* 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 before public sale of meat

The US [[Centers for Disease Control and Prevention]] makes the following recommendation: "Curing (salting), drying, smoking, or microwaving meat does not consistently kill infective worms."<ref>In addition, out of the reports of trichinosis in the United States, all have been a result of mass production, particularly in large venues, such as cafeterias and mall food courts.
{{cite web| url = https://www.cdc.gov/ncidod/dpd/parasites/trichinosis/factsht_trichinosis.htm| title = Parasitic Disease Information – Trichinellosis| author = [[Centers for Disease Control and Prevention]], Division of Parasitic Diseases| date = 2004-07-15| access-date = 2007-01-28| url-status = live| archive-url = https://web.archive.org/web/20070128070459/http://www.cdc.gov/ncidod/dpd/parasites/trichinosis/factsht_trichinosis.htm| archive-date = 2007-01-28}}</ref>
However, under controlled commercial food processing conditions, some of these methods are considered effective by the USDA.<ref>
{{cite web| url = http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr&sid=f9361ee66063187dffee4c083c24b6a7&rgn=div5&view=text&node=9:2.0.2.1.19&idno=9#9:2.0.2.1.19.1.21.9| title = Electronic Code of Federal Regulations; Title 9: Animals and Animal Products; Part 318 – Entry into Official Establishments; Reinspection and Preparation of Products; § 318.10 Prescribed treatment of pork and products containing pork to destroy trichinae| author = United States Department of Agriculture| access-date = 2007-01-28| url-status = dead| archive-url = https://web.archive.org/web/20060929115037/http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr&sid=51d274787de185a8f3e56500af8649ca&rgn=div5&view=text&node=9%3A2.0.2.1.19&idno=9#9:2.0.2.1.19.1.21.9| archive-date = 2006-09-29| author-link = United States Department of Agriculture}}</ref>

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, 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.<ref name=fifteen>USDA Animal and Plant Health Inspection Service APHIS – Veterinary Services. Retrieved February 11, 2009, {{cite web |url=http://www.aphis.usda.gov/vs/trichinae/ |title=Trichinae Herd Certification Pilot |access-date=2009-08-23 |url-status=dead |archive-url=https://web.archive.org/web/20090814134507/http://www.aphis.usda.gov/vs/trichinae/ |archive-date=2009-08-14 }}</ref> The CDC reports 0.013% of U.S. swine are infected with ''Trichinella''.<ref name="fifteen"/>

==Treatment==
As with most diseases, early treatment is better and decreases the risk of developing the disease. If larvae do encyst in skeletal muscle cells, they can remain infectious for months to years.<ref name="two"/>

===Primary treatment===
Early administration of [[anthelmintics]], such as [[mebendazole]] or [[albendazole]],<ref>{{Cite web |title=Trichinosis Fact Sheet |url=https://www.health.ny.gov/diseases/communicable/trichinosis/fact_sheet.htm |access-date=2025-01-17 |website=www.health.ny.gov}}</ref> decreases the likelihood of larval encystation, particularly if given within three days of infection.<ref name="eight"/> However, most cases are diagnosed after this time.<ref name="two"/>  In humans, mebendazole (200–400&nbsp;mg three times a day for three days) or albendazole (400&nbsp;mg twice a day for 8–14 days) is given to treat trichinosis.<ref>{{cite web|url=http://www.medscape.com/druginfo/monograph?cid=med&drugid=4254&drugname=Mebendazole+Misc&monotype=monograph|title= Monograph – Mebendazole|publisher=medscape.com|access-date=2009-02-24}}</ref> These drugs prevent newly hatched larvae from developing, but should not be given to pregnant women or children under two years of age.<ref name="five"/>

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.<ref>{{cite journal  |author=<!--Staff writer(s); no by-line.-->  | title=Clinical Aspects and Treatment of the More Common Intestinal Parasites of Man (TB-33) | journal=Veterans Administration Technical Bulletin 1946 & 1947 | year=1948 | volume=10 | pages=1–14 | url=https://books.google.com/books?id=uJWxEzwqRiMC }}</ref>

===Secondary treatment===
After infection, [[steroids]], such as [[prednisone]], may be used to relieve muscle pain associated with larval migration.{{citation needed|date=January 2021}}

===Vaccine research===
Researchers trying to develop a vaccine for ''Trichinella'' have tried using either "larval extracts, excretory-secretory antigen, DNA, or recombinant antigen protein."<ref name="thirteen"/> 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.<ref>{{cite journal|last1=Ali|first1=S.M.|last2=El-Zawawy|first2=L.A.|last3=El-Said|first3=D.|last4=Gaafar|first4=M.R.|title=Immunization against trichinellosis using microwaved larvae of Trichinella spiralis |journal=Journal of the Egyptian Society of Parasitology|date=2007|volume=37|issue=1|pages=121–33|pmid=17580572}}</ref>
* Another study<ref>Dea-Ayuela et al. (2006)</ref> used extracts and excretory-secretory products from first-stage larvae to produce an oral vaccine.<ref name=twelve>{{cite journal |author1=Dea-Ayuela M. A. |author2=Iniguz S.R. |author3=Fernandez F.B. | year = 2006 | title = Vaccination of mice against intestinal Trichinella spiralis infections by oral administration of antigens microencapsulated in methacrilic acid copolymers | journal = Vaccine | volume = 24 | issue = 15| pages = 2772–80 | doi=10.1016/j.vaccine.2006.01.006 | pmid=16446017}}</ref> 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.{{citation needed|date=January 2023}}
* A DNA vaccine tested on mice "induced a muscle larva burden reduction in BALB/c mice by 29% in response to ''T. spiralis'' infection".<ref name=thirteen>{{cite journal |author1=Gu Y. |author2=Li J. |author3=Zhu X. |author4=Yang J. |author5=Li Q. |author6=Liu Z. |author7=Yu S. |author8=Li Y. | year = 2008 | title = Trichinella spiralis: Characterization of phage-displayed specific epitopes and their protective immunity in BALB/c mice | journal = Experimental Parasitology | volume = 118 |issue=1 | pages = 66–74 | doi=10.1016/j.exppara.2007.06.014|pmid=17707815 }}</ref>

==Epidemiology==
[[File:Parasite160031-fig1 Figatelli (pork sausages) with inadequate labelling.tif|thumb|right|Pork sausages eaten raw by consumers caused an outbreak of trichinellosis in 2015 in France.]]
About 11 million humans are infected with ''Trichinella''; ''T. spiralis'' is the species responsible for most of these infections.<ref>{{Cite journal |last=Dupouy-Camet |first=Jean |date=December 2000 |title=Trichinellosis: a worldwide zoonosis |url=https://linkinghub.elsevier.com/retrieve/pii/S0304401700003411 |journal=Veterinary Parasitology |language=en |volume=93 |issue=3–4 |pages=191–200 |doi=10.1016/S0304-4017(00)00341-1|pmid=11099837 |url-access=subscription }}</ref> Infection was once very common, but this disease is now rare in the [[First World|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.<ref>{{Cite web|url=http://www.ilsecoloxix.it/p/genova/2015/05/12/AReWQ0PE-intossicati_allarme_capodanno.shtml|title=Relazione dei nas – Genova, allarme carne cruda: decine di intossicati dopo Capodanno|access-date=2016-09-16|url-status=live|archive-url=https://web.archive.org/web/20160918192914/http://www.ilsecoloxix.it/p/genova/2015/05/12/AReWQ0PE-intossicati_allarme_capodanno.shtml|archive-date=2016-09-18}}</ref><ref>{{Cite news|url=http://www.salute.gov.it/relazioneAnnuale2015/stampaDettaglioRA2015.jsp?id=1062|title=Relazione annuale al PNI 2015 Trichine – Prevenzione e controllo|via=Ministero della Salute www.salute.gov.it|url-status=live|archive-url=https://web.archive.org/web/20160923010228/http://www.salute.gov.it/relazioneAnnuale2015/stampaDettaglioRA2015.jsp?id=1062|archive-date=2016-09-23}}</ref> The second outbreak in France was associated with pork sausages from [[Corsica]], which were eaten raw, affecting 14 people in total.<ref name="RuetschDelaunay2016">{{cite journal|last1=Ruetsch|first1=Caroline|last2=Delaunay|first2=Pascal|last3=Armengaud|first3=Alexis|last4=Peloux-Petiot|first4=Françoise|last5=Dupouy-Camet|first5=Jean|last6=Vallée|first6=Isabelle|last7=Polack|first7=Bruno|last8=Boireau|first8=Pascal|last9=Marty|first9=Pierre|title=Inadequate labeling of pork sausages prepared in Corsica causing a trichinellosis outbreak in France|journal=Parasite|volume=23|year=2016|pages=27 |doi=10.1051/parasite/2016027|pmid=27317463|pmc=4912683}} {{open access}}</ref>
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).<ref name=ElevenCases/> 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.<ref>
{{cite web|url=https://www.cdc.gov/ncidod/dpd/parasites/trichinosis/factsht_trichinosis.htm|title=Trichinellosis Fact Sheet – Division of Parasitic Diseases|publisher=Centre for Disease Control, US Government|year=2004|access-date=2008-02-25|url-status=live|archive-url=https://web.archive.org/web/20080224154958/http://www.cdc.gov/ncidod/dpd/parasites/trichinosis/factsht_trichinosis.htm|archive-date=2008-02-24}}
</ref>

China reports around 10,000 cases every year and is the country with the highest number of cases.<ref name="two"/>{{Dubious|date=October 2024|reason=This number doesn't appear in the citation, and is equal to the global caseload in the article lead}} In China, between 1964 and 1998, over 20,000 people became infected with trichinosis, and more than 200 people died.<ref name="thirteen"/>

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.<ref name="two"/>

In the [[Third World|developing world]], most infections are associated with undercooked pork. For example, in [[Thailand]], between 200 and 600 cases are reported annually around the [[Thai New Year]]. This is mostly attributable to a particular delicacy, ''[[larb]]'', which calls for undercooked pork as part of the recipe.{{citation needed|date=January 2021}}

In parts of Eastern Europe, the [[World Health Organization]] reports, some swine herds have trichinosis infection rates above 50%, with correspondingly large numbers of human infections.<ref>{{cite web |url=http://www.emedicine.com/emerg/topic612.htm |title=EMedicine - Trichinosis : Article by L Kristian Arnold, MD |access-date=2006-01-27 |url-status=live |archive-url=https://web.archive.org/web/20060128060606/http://www.emedicine.com/emerg/topic612.htm |archive-date=2006-01-28 }}</ref>

=== 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. Before this act, swine were fed garbage that could potentially be infected by'' T. spiralis''.{{Citation needed|date=January 2025}} 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.<ref>Roy, Sharon, Adriana Lopez, and Peter Schantz. "Trichinellosis Surveillance – United States, 1997–2001." Morbidity and Mortality Weekly Report: Surveillance Summaries (2003): 1–8. JSTOR. Centers for Disease Control & Prevention (CDC). Web. 1 Dec. 2014.</ref>

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;<ref name=ElevenCases/> these were mostly the result of consuming undercooked game (sylvatic transmission) or home-reared pigs (domestic transmission).{{citation needed|date=May 2022}}

===Religious groups===
The [[kashrut]] and [[halal]] dietary laws of [[Judaism]] and [[Islam]] 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 philosophy|Jewish]] philosopher [[Maimonides]] that food forbidden by Jewish law was "unwholesome". This theory was controversial and eventually fell out of favor.<ref>{{cite book|last1=Harris|first1=Marvin|title=Good to Eat: Riddles of Food and Culture|date=1985|publisher=Simon and Schuster|location=New York|isbn=0-671-50366-9|pages=67–70|chapter=4|chapter-url-access=registration|chapter-url=https://archive.org/details/goodtoeatriddles00harr}}</ref>

===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]], supplemented by the increased distribution of meat products, political changes, a changing climate, and increasing [[sylvatic]] transmission.<ref>{{cite journal |pmid=11113259 |date=2000 |last1=Murrell |first1=K. D. |last2=Pozio |first2=E. |title=Trichinellosis: The zoonosis that won't go quietly |journal=International Journal for Parasitology |volume=30 |issue=12–13 |pages=1339–1349 |doi=10.1016/s0020-7519(00)00132-6 }}</ref>

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.<ref name=seven>{{cite journal |pmid=17488927 |date=2007 |last1=Blaga |first1=R. |last2=Durand |first2=B. |last3=Antoniu |first3=S. |last4=Gherman |first4=C. |last5=Cretu |first5=C. M. |last6=Cozma |first6=V. |last7=Boireau |first7=P. |title=A dramatic increase in the incidence of human trichinellosis in Romania over the past 25 years: Impact of political changes and regional food habits |journal=The American Journal of Tropical Medicine and Hygiene |volume=76 |issue=5 |pages=983–986 |doi=10.4269/ajtmh.2007.76.983 }}</ref>

==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, [[United States|American]] scientist [[Joseph Leidy]] pinpointed undercooked meat as the primary vector for the parasite, and two decades afterward, this hypothesis was fully accepted by the scientific community.<ref>{{cite web |url=http://www.ansp.org/museum/leidy/other/parasitology.php |title=Academy of Natural Sciences - Joseph Leidy - Parasitology |website=www.ansp.org |access-date=13 January 2022 |archive-url=https://web.archive.org/web/20061008191244/http://www.ansp.org/museum/leidy/other/parasitology.php |archive-date=8 October 2006 |url-status=dead}}</ref>

===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 a 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]], who is now credited for the discovery of the ''T. spiralis'' larval form.<ref name=four>{{cite journal | author = Cook GC | year = 2001 | title = Outbreak of trichinosis (trichiniasis) – contracted in London in 1879 | journal = Postgraduate Medical Journal | volume = 77 | issue = 903| pages = 62–63 | doi=10.1136/pmj.77.903.62| pmid = 11123411 | pmc = 1741881}}</ref><ref>Richard Owen (1835) [https://books.google.com/books?id=Bh0zAQAAMAAJ&pg=PA315 "Description of a microscopic entozoon infesting the muscles of the human body,"] {{webarchive|url=https://web.archive.org/web/20160426160457/https://books.google.com/books?id=Bh0zAQAAMAAJ&pg=PA315 |date=2016-04-26 }} ''Transactions of the Zoological Society of London'', '''1''' :  315–24.  Paget is mentioned on pp. 315 and 320.</ref>

===Lifecycle===
A series of experiments conducted between 1850 and 1870 by the German researchers [[Rudolf Virchow]], [[Rudolf Leuckart]], and [[Friedrich Albert von Zenker]], 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''.<ref>{{cite journal | author = Blumer G | title = Some remarks on the early history of Trichinosis (1822–1866) | journal = Yale Journal of Biology and Medicine | volume = 1 | issue = 6| pages = 581–88 }}</ref>

==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]].{{citation needed|date=January 2021}}

==See also==
* [[List of parasites (human)]]
* [[Nurse cell]]

==References==
{{Reflist | 2}}
{{Refbegin}}
* ''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]]. Trichinosis Surveillance, United States, 1987–1990, MMWR 1991;40:(SS-3)35-42.
* {{cite journal |vauthors=Moorhead A, Grunenwald PE, Dietz VJ, Schantz PM | year = 1999 | title = Trichinellosis in the United States, 1991–1996: Declining but not gone | journal = Am J Trop Med Hyg | volume = 60 | issue = 1 | pages = 66–69 | doi = 10.4269/ajtmh.1999.60.66 | pmid = 9988325 | doi-access =  | s2cid = 23888211 }}
* [https://web.archive.org/web/20060225104215/http://www.cfsan.fda.gov/~lrd/9CF318.html USDA regulations – Title 9 – Chapter 3 – Part 318 – includes "Prescribed treatment of pork and products containing pork to destroy trichinae."]
{{Refend}}

== External links ==
{{Commons category|Trichinosis}}
* [http://www.med.unipi.it/ict/welcome.htm International Commission on trichinellosis web pages] {{Webarchive|url=https://web.archive.org/web/20070823170537/http://www.med.unipi.it/ict/welcome.htm |date=2007-08-23 }}
* [https://www.cdc.gov/ncidod/dpd/parasites/trichinosis/default.htm CDC Department of Parasitic Diseases – Trichinosis]
* {{cite journal | pmid = 22244535 | doi=10.1016/j.vetpar.2011.12.026 | volume=187 | issue=1–2 | title=Farmed wild boars exposed to Toxoplasma gondii and Trichinella spp | date=June 2012 |vauthors=Jokelainen P, Näreaho A, Hälli O, Heinonen M, Sukura A | journal=Vet. Parasitol. | pages=323–27}}

{{Consumer Food Safety}}
{{Helminthiases}}
{{Medical resources
|   ICD11          = {{ICD11|1F6E}}
|   ICD10          = {{ICD10|B|75||b|65}}
|   ICD9           = {{ICD9|124}}
|   ICDO           =
|   OMIM           =
|   DiseasesDB     = 13326
|   MedlinePlus    = 000631
|   eMedicineSubj  =
|   eMedicineTopic =
|   MeshID         = D014235
}}
{{Authority control}}

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