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==Learning resources==
*旋毛虫 in Japanese
*[https://www.trichinella.org/home THE TRICHINELLA PAGE]
*[https://www.cdc.gov/dpdx/trichinellosis/index.html Trichinellosis - DPDx by US CDC]
*[http://www.ichiryusha.com/book/index.php?main_page=product_info&cPath=23&products_id=1154 Illustrated ''Trichinella'' written by Yuzo Takahashi] (not for sale)
==Pathogen and Taxonomy==
*The genus ''Trichinella'' has '''genetically distinguished''' but '''taxonomically still undetermined''' genotypes other than usual species
*The biggest morphological classification is based on the presence/absence of collagen capsule surrounding the pathogen in cysts in infected muscles
{|class="wikitable"
|-
!style="width:50%"|Encapsulated
!style="width:50%"|Non-encapsulated
|-style="text-align:center"
|Infect only mammals
|Infect birds and mammals
|-style="vertical-align:top"
|
*''Trichinella spiralis''
*''Trichinella nativa''*旋毛虫''Trichinella nelsoni''*''Trichinella britovi''*''Trichinella murrelli''*''Trichinella patagoniensis''*''Trichinella'' genotype T6*''Trichinella'' genotype T8*''Trichinella'' genotype T9|*''Trichinella pseudospiralis''*''Trichinella papuae''*''Trichinella zimbabwensis''|} ※Manson's Tropical Infectious Diseases 24th ed. (published in 2023) describes that ''T. spiralis'' has several subspecies but according to [https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Undef&id=6333&lvl=3&keep=1&srchmode=1&unlock '''NCBI Taxonomy Browser'''] and the following articles subspecies written in Manson's are classified as species. {{quote|content=Pozio, E., Rosa, G. la, Murrell, K. D., & Lichtenfels, J. R. (1992). Taxonomic Revision of the Genus Trichinella. The Journal of Parasitology, 78(4), 654. https://doi.org/10.2307/3283540}} {{quote|content=Zarlenga, D., Thompson, P., & Pozio, E. (2020). Trichinella species and genotypes. Research in Veterinary Science, 133, 289–296. https://doi.org/10.1016/j.rvsc.2020.08.012}} ==Epidemiology==*Since ''Trichinella'' infections often cause asymptomatic or mild disease and no serological tests with high performance is available, true epidemiology of human trichinellosis is thought still underestimated.*Trichinellosis distributes '''worldwide''' from '''arctic region''' through '''the tropics'''.*Human trichinellosis in developed countries has been dramatically decreased due to improvement of farming and slaughtering of domestic pigs and shrinkage of backyard pig farming in private facilities. {{quote|content=Yayeh, M., Yadesa, G., Erara, M., Fantahun, S., Gebru, A., & Birhan, M. (2020). Epidemiology, diagnosis and public health importance of Trichinellosis. Journal of World’s Poultry Research, 10(3), 131–139. https://doi.org/10.36380/scil.2020.ojafr18}} *Distribution of species (directly linked from [https://www.trichinella.org/home THE TRICHINELLA PAGE]) https://images.squarespace-cdn.com/content/v1/5adf9528f93fd46f6d3ddb95/1533145049330-8G0LCIZZ85UXA9J9CYP2/geodistribution.gif ==Life cycle and Transmission==*Life cycle is maintained amongst host mammals and birds.**Pigs and rats (domestic cycle) or wild bores, wild bears, polar bears, rats and birds (sylvatic cycle).**Humans are '''accidental (deadend) hosts''' for ''Trichinella''**'''Only humans develop clinical symptoms by ''Trichinella'' infection'''*Refer to [https://www.cdc.gov/dpdx/trichinellosis/index.html DPDx - Trichinellosis]https://www.cdc.gov/dpdx/trichinellosis/modules/Trichinella_LifeCycle.gif *Transmission to human occurs by ingestion of raw or undercooked meat including '''pigs''', '''wild bores''', '''horse''', '''dog''', '''bear''', '''polar bear''', '''badger''' and '''soft-shelled turtle (スッポン)'''.*Transmission to horse (obligate grazer) is speculated that pasture or hay may be accidentally contaminated by infected carcass (rodents etc.). {{quote|content=Rostami, A., Gamble, H. R., Dupouy-Camet, J., Khazan, H., & Bruschi, F. (2017). Meat sources of infection for outbreaks of human trichinellosis. Food Microbiology, 64, 65–71. https://doi.org/10.1016/j.fm.2016.12.012}} *'''The world-first report''' of trichinellosis originated from '''soft-shelled turtle''' was published in Japan in 2009 (but only in Japanese and neglected from English literature).*The transmission route is speculated that soft-shelled turtles were fed by carrions of pigs dead by diseases and contaminated through the carrions. {{quote|content=前田卓哉, 藤井毅, 岩本愛吉, 長野功, 呉志良, & 高橋優三. (2009). スッポンを感染源とする旋毛虫症例. 病原微生物検出情報, 30(10), 272–273. https://idsc.niid.go.jp/iasr/30/356/kj3563.html}} *Report of trichinellosis outbreak through game bear meat in Japan.{{quote|content=海野友梨, 中本有美, & 深谷節子. (2017). 茨城県内で発生した旋毛虫による食中毒事例について. 茨城衛生研究所年報, 55, 37–41. https://www.pref.ibaraki.jp/hokenfukushi/eiken/kikaku/annualreport/documents/32_senmoutyu.pdf}} ==Human disease==*Humans are '''accidental (deadend) hosts'''.#Ingestion of larvae-infected meat#'''Enteric phase'''##In 2-7 days incubation, larvae penetrate duodenal and jejunal mucosa##Nausea, vomitting, abdominal colic, fever###Maculopapular skin rash and pneumonitis may accompany#'''Migration (invasion) phase'''##Larvae invade blood vessels and migrate toward striated muscle cells in '''diaphragm''', '''masseters''', '''intercostals''', '''laryngeal''', '''tongue''' and '''ocular muscles'''##Severe myalgia, difficulty of mastication, difficulty of breathing, dysphagia, periorbital edema, paralysis of extremities, high fever, petechiae in nails and conjunctivae##Eosinophilia arises but subsides in a week###In some case myocardial complication, neurological complication occurs#'''Encystment phase'''##Weeks after infection, larvae encyst in striated muscles they arrived##Cachexia, edema, extreme dehydration##In 6 months calcification of cysts takes place##Inside calcified cysts, '''<nowiki>'</nowiki>nurse cells<nowiki>'</nowiki>''' which is transformed from normal striated muscle cells by larvae secretion encapsulate and nourish larvae##'''Encapsulated larvae can survive months to decades in human striated muscles'''*The larger number of larvae infect, the more severe symptoms are**<10 larvae: asymptomatic to mild**50-500 larvae: moderate**<1000 larvae: severe to fatal ===Nurse cell===*Refer to [https://www.trichinella.org/the-nurse-cell Nurse cell formation in THE TRICHINELLA PAGE] or the following article{{quote|content=Wu, Z., Sofronic-Milosavljevic, L., Nagano, I., & Takahashi, Y. (2008). Trichinella spiralis: nurse cell formation with emphasis on analogy to muscle cell repair. Parasites & Vectors, 1(1), 27. https://doi.org/10.1186/1756-3305-1-27}} ==Diagnosis=={|class="wikitable" style="width:800px"|+Case definitions by ECDC|-!style="width:33%"|Clinical!style="width:33%"|Laboratory!style="width:33%"|Epidemiological|-style="vertical-align:top"|At least 3 of*Fever*Myalgia*Gastrointestinal symptoms*Facial edema*Eosinophillia*Subconjunctival, sublingual and retinal hemorrhage|At least 1 of*''Trichinella'' larvae in muscle biopsy specimen*''Trichinella''-specific antibody by ELISA or Western blot|At least 1 of*Ingestion of laboratory-confirmed contaminated meat*Ingestion of potentially contaminated meat from laboratory-confirmed infected animal*Epidemiological link to laboratory-confirmed human case with the common source|}{{quote|content=Gottstein, B., Pozio, E., & Nöckler, K. (2009). Epidemiology, Diagnosis, Treatment, and Control of Trichinellosis. Clinical Microbiology Reviews, 22(1), 127–145. https://doi.org/10.1128/CMR.00026-08}} *'''Trichinoscopy'''**Encystment phase begins 1 week after infection at the shortest**Muscle biopsy specimen is thin-sliced and pressed between two slides without any stain and cysts are observed*ELISA for antibody detection is common*Multiplex PCR is also used ===Differential diagnoses===*Trichinellosis is a great mimicker**Typhoid, encephalitis, myositis, tetanus, Katayama syndrome, hookworm infection, strongyloidiasis, periarthritis nodosa, rheumatoid arthritis ==Treatment==*Albendazole and mebendazole ==Prevention and Control=={|class="wikitable"|-!style="width:50%"|Heat!style="width:50%"|Freezing|-|rowspan="2"|*Meat core temperature '''≥71°C '''for''' ≥1 min'''**Color to gray, muscle fibers separated|Up to '''15cm thickness''' meat block*'''≤-15°C '''for''' ≥3 weeks'''|-|Up to '''50cm thickness''' meat block*'''≤-15°C '''for''' ≥4 weeks'''|-||※'''Applicable only to ''T. spiralis'' in pork'''|} ※Other species are more resistant to cold temperature*''T. britovi'' in pork survived for 3 weeks at -20°C*''T. spiralis'' in horse survived for 4 weeks at -18°C*Game meat like bear harbors freeze-resistant ''Trichinella''**5 years in bear meat
