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Encephalitozoon cuniculi is a eukaryotic organism belonging to the phylum Microsporidia, in the kingdom Fungi. An obligate intracellular parasite, E. cuniculi occurs in laboratory mice and rabbits, monkeys, dogs, rats, birds, guinea pigs, and other mammals including humans. At various early times it was thought it was the cause of rabies and polio. This parasite may be transmitted in body exudates or transplacentally. Although damages are minimal, an infection can be fatal, especially in immunocompromised individuals such as AIDS patients.^1,2

Life cycle

The infective form of microsporidia (E. cuniculi) is a resistant spore which can survive for a long time in the environment. The spore extrudes its polar tubule and infects the host cell. The spore injects the infective sporoplasm into the eukaryotic host cell through the polar tubule. Inside the cell, the sporoplasm undergoes extensive multiplication. This multiplication occurs either by merogony (binary fission) or schizogony (multiple fission). Microsporidia develop by sporogony to mature spores in the cytoplasm or inside parasitophorous vacule. . During sporogony, a thick wall is formed around the spore. The thick wall formed provides resistance to adverse environmental conditions. Once the spores increase in number and completely fill the cytoplasm of the host's cell, the cell membrane is disrupted and releases the spores to the surroundings. These free mature spores can infect new cells thus continuing the cycle.

Transmission

The majority of rabbits seem to become infected with E. cuniculi from their mothers. Infection can also occur when something contaminated by urine containing E. cuniculi spores has been ingested. Approximately one month after the rabbit is infected it begins to shed E. cuniculi spores via its urine. Spores continue to be shed for approximately 3 months, but can be shed throughout the rabbit's life.

Neurological impairment

E. cuniculi is a fungus that commonly parasitizes rabbits. The majority of the time, these organisms do not cause any obvious clinical disease. In fact, most often, E. cuniculi remains dormant within rabbits, never causing any problems upon initial infection. These parasites rarely migrate to nervous tissue or other organs. On occasions when E. cuniculi do reach nervous tissue, rabbits can experience neurological impairment, characterized by partial or complete paralysis, loss of coordination, seizures, and head tilting. Neurological impairment is thought to occur when E. cuniculi multiply within the rabbit's body inducing the development of granulomas, which are believed to travel through the body via white blood cells. The only way to expel these parasites is via urine. Something to note, however, is that it is still unknown if the damage is incurred by E. cuniculi directly, through natural growth and replication, or by the immune response itself. This uncertainty arises because there have been many well documented diseases in which humans and animals' own immune systems react to a non-threatening pathogen, but the immune response itself is responsible for the disease.

Detection

Antibodies to E. cuniculi can be detected through a blood test called a titer test. A rabbit who has been exposed to E. cuniculi in its lifetime will produce antibodies as a result of this exposure. A titer test is used to detect the level of the antibody to the organism in the blood. A positive titer tells you that the rabbit has been exposed to this parasite at some point in its life. Note that this does not allow one to differentiate between simple exposure and an active infection. By doing two titer tests (with an interval of time in between) and comparing the results, it is possible to determine if the rabbit is mounting an immune response to an active infection or if he was previously infected. However, even with a rising titer, one can't determine for certain that a particular health problem is being caused by E.cuniculi or something else. Head tilt, for example, has many causes other than E. cuniculi, including bacterial or viral infections, trauma and toxicity. A false negative titer may also result if an infected animal produces an inadequate amount of antibodies.

History

Microsporidia are obligate intracellular parasitic fungi infesting many animal groups. Lacking mitochondria and peroxysomes, these unicellular eukaryotes were first considered a deeply branching protist lineage that diverged before the endosymbiotic event that led to mitochondria. The discovery of a gene for a mitochondrial-type chaperone combined with molecular phylogenetic data later implied that microsporidia are atypical fungi that lost mitochondria during evolution. Its genome consists of approximately 2.9-megabases (Mbs) in 11 chromosomes, with a total of 1,997 potential protein-coding genes. Genome compaction is reflected by reduced intergenic spacers and by the shortness of most putative proteins relative to their eukaryote orthologues. The strong host dependence is illustrated by the lack of genes for some biosynthetic pathways and for the tricarboxylic acid cycle. Phylogenetic analysis lends substantial credit to the fungal affiliation of microsporidia. Because the E. cuniculi genome contains genes related to some mitochondrial functions (for example, Fe-S cluster assembly), we hypothesize that microsporidia have retained a mitochondrion-derived organelle.

References

Katinka MD, Duprat S, Cornillot E, Méténier G, Thomarat F, Prensier G, Barbe V, Peyretaillade E, Brottier P, Wincker P, Delbac F, El Alaoui H, Peyret P, Saurin W, Gouy M, Weissenbach J, Vivarès CP. (2001). "Genome sequence and gene compaction of the eukaryote parasite Encephalitozoon cuniculi.". Nature 414 (6862): 401–2. doi:10.1038/35106579. PMID 11719806.
Mertens, R.B., E.S. Didier, M. C. Fishbien, D.C. Bertucci, L.B. Rogers, and J. M. Orenstien. (1997.). "Encephalitozoon cuniculi ,microsporidiosis: Infection of the brain, heart, kidneys, trachea, adrenal glands, and urinary bladder in a patient with AIDS.". Mod. Pathol. 10 (1): 68–77. PMID 9021729.
Shadduck, J.A., W.T. Watson,S.P. Pakes, and A. Cali. (1979). "Animal infectivity of Encephalitozoon cuniculi.". J. Parasitol. 65 (1): 123–129. doi:10.2307/3280216. JSTOR 3280216. PMID 109602.
Suter C., Muller-Doblies U.U., Hatt J-M., Deplazes P. (2001). "Prevention and Treatment of Encephalitozoon cuniculi in rabbits with fenbendazole.". Veterinary Record 148 (15): 478–80. doi:10.1136/vr.148.15.478. PMID 11334074.

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1. 微胞子虫症 microsporidiosis
2. 下痢を伴うHIV感染患者の評価 evaluation of the hiv infected patient with diarrhea

English Journal

SWP5, a Spore Wall Protein, Interacts with Polar Tube Proteins in the Parasitic Microsporidian Nosema bombycis.

Li Z, Pan G, Li T, Huang W, Chen J, Geng L, Yang D, Wang L, Zhou Z.SourceAddress correspondence to Zeyang Zhou, zyzhou@swu.edu.cn.
Eukaryotic cell.Eukaryot Cell.2012 Feb;11(2):229-37. Epub 2011 Dec 2.
Microsporidia are a group of eukaryotic intracellular parasites that infect almost all vertebrates and invertebrates. The microsporidian invasion process involves the extrusion of a unique polar tube into host cells. Both the spore wall and the polar tube play an important role in microsporidian pat
PMID 22140229

Microsporidia as emerging pathogens and the implication for public health: A 10-year study on HIV-positive and -negative patients.

Lobo ML, Xiao L, Antunes F, Matos O.SourceGrupo de Protozoários Oportunistas/VIH e Outras Protozooses/Unidade de Parasitologia Médica, CMDT, Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa, Lisboa, Portugal.
International journal for parasitology.Int J Parasitol.2012 Feb;42(2):197-205. Epub 2012 Jan 8.
Despite recent advances in the understanding and diagnosis of emerging microsporidian pathogens, more research is necessary to elucidate their complex epidemiology. In fact, studies that reflect true human-infecting microsporidian prevalence are still inadequate. The present 10-year study was undert
PMID 22265899

Japanese Journal

Surveillance for an Outbreak of Encephalitozoon cuniculi Infection in Rabbits Housed at a Zoo and Biosecurity Countermeasures

FUKUI Daisuke,BANDO Gen,FURUYA Koji,YAMAGUCHI Masanori,NAKAOKA Yuji,KOSUGE Masao,MURATA Koichi
Journal of Veterinary Medical Science, 2012
… Of 38 rabbits examined to detect specific antibodies against Encephalitozoon cuniculi, 71.1% (n=27) were found seropositive; … cuniculi. …
NAID 130001879695

Identification of Encephalitozoon cuniculi genotype III and two novel genotypes of Enterocytozoon bieneusi in swine

REETZ Jochen,NOCKLER Karsten,RECKINGER Sabine,VARGAS Maria Margarida,WEISKE Wolf,BROGLIA Alessandro
Parasitology international : official journal of the Japanese Society of Parasitology 58(3), 285-292, 2009-09-01
NAID 10027669859

日本国内のペットウサギにおけるウサギエンセファリトゾーン(Encephalitozoon cuniculi)感染に関する血清疫学調査

大橋英二,藤本智,五十嵐慎 [他]
Clinic note 5(8), 72-75, 2009-08
NAID 40016784066

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リンク元	「新興感染症」「エンセファリトゾーン・クニクリ」
関連記事	「Encephalitozoon」「cuniculi」

「新興感染症」

Encephalitozoon cuniculi
Scientific classification
Kingdom:	Fungi
Phylum:	Microsporidia
Family:	Unikaryonidae
Genus:	Encephalitozoon
Species:	E. cuniculi
Binomial name
	Encephalitozoon cuniculi;

　　[★]

英: emerging infectious disease
関: 感染症、再興感染症

「これまで知られていなかったが、1973年以降に見いだされた病原体」
http://www.mext.go.jp/a_menu/shotou/clarinet/004/004/003.pdfより

新たにヒトでの感染が証明された疾患、あるいはそれまでその土地では存在しなかったが新たにそこでヒトの病気として現れてきたものなどとされています。原因が不明であった疾患のうち病原物質が明らかとなり、地域あるいは国際的に多くの人の健康に対して問題となるものも新興感染症の概念の中に含まれます。

一覧

年	病原微生物	種類	疾患
1973	Rotavirus	ウイルス	小児下痢症
1975	Parvovirus B19	ウイルス	伝染性紅班
1976	Cryptosporidium parvum	寄生虫	下痢症
1977	Eboravirus	ウイルス	エボラ出血熱
	Legionella pneumophila	細菌	レジオネラ症
	Hantaanvirus	ウイルス	腎症候性出血熱
	Campylobacter jejuni	細菌	下痢症
1980	Human T-lymphotropic virus-1	ウイルス	成人T細胞白血病
1980	Hepatitis D virus	ウイルス	D型ウイルス肝炎
1981	TSST-1-producing Staphylococcus aureus	細菌	毒素性ショック症候群
1982	Escherichia coli 0157:H7	細菌	腸管出血性大腸炎、溶血性尿毒症症候群
	Human T-lymphotropic virus-2⁽¹⁾	ウイルス	白血病
	Borrelia burgobrferi	細菌	ライム病
	Rickttsia japonica	細菌	日本紅斑熱
1983	Human immunodeficiency virus	ウイルス	後天性免疫不全症候群
1983	Helicobacter pylori	細菌	胃炎(胃潰瘍、十二指腸潰瘍、胃癌、MALTリンパ腫)
1985	Enterocytozoon bieneusi	寄生虫	持続性下痢症
1986	Cyclospora cayetanensis	寄生虫	持続性下痢症
1986	Prion⁽²⁾	プリオン	牛海綿状脳症
1988	Human herpesvirus-6	ウイルス	突発性発疹症
1988	Hepatitis E virus	ウイルス	E型肝炎
1989	Ehriichia chaffeensis	細菌	エールリキア症
	Hepatitis C virus	ウイルス	C型肝炎
	Clamydia pneumoniae	細菌	肺炎、気管支炎
1991	Guanarito virus	ウイルス	ベネズエラ出血熱
	Encephalitozoon heilem	寄生虫	結膜炎
	Newspecis of Babesia	寄生虫	非定型性バベシア症
1992	Vibrio choerae 0139	細菌	新型コレラ
1992	Bartoneiia henselae	細菌	猫ひっかき病
1993	Sin Nombre virus	ウイルス	ハンタウイルス肺症候群(成人呼吸窮迫症候群)
1993	Encephalitozoon cuniculi	真菌	ミクロスポリドーシス
1994	Sabia virus	ウイルス	ブラジル出血熱
1994	Hendra virus	ウイルス	ウイルス性脳炎
1995	Human herpesvirus-8	ウイルス	カポジ肉腫
1995	Hepatitis G virus	ウイルス	G型肝炎
1996	TSE causing agent	プリオン	新型クロイツフェルト・ヤコブ病
1996	Australian bat lyssavirus	ウイルス	ウイルス性脳炎
1997	Influenza A/H5N1	ウイルス	トリ型インフルエンザのヒト感染
1999	Nipa hvirus	ウイルス	急性脳炎
2003	SARS coronavirus	ウイルス	重症急性呼吸器症候群(SAR)