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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) ==Pathogenand 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
}}
==TransmissionHuman 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
==Life cycle and human disease=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
