oocyst

オーシスト

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2014/04/05 09:32:04」(JST)

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Cellular structure of a typical, generalised Apicomplexan: 1-polar ring, 2-conoid, 3-micronemes, 4-rhoptries, 5-nucleus, 6-nucleolus, 7-mitochondria, 8-posterior ring, 9-alveoli, 10-golgi apparatus, 11-micropore.

Apicomplexans, a group of intracellular parasites, have life cycle stages evolved to allow them to survive the wide variety of environments they are exposed to during their complex life cycle. Each stage in the life cycle of an apicomplexan organism is typified by a cellular variety with a distinct morphology and biochemistry.

Not all apicomplexa develop all the following cellular varieties and division methods. This presentation is intended as an outline of a hypothetical generalised apicomplexan organism.

Methods of asexual replication

See also: Fission (biology)

Apicomplexans (sporozoans) replicate via ways of multiple fission (also known as schizogony). These ways include gametogony, sporogony and merogony, although the latter is sometimes referred to as schizogony, despite its general meaning.

Merogony is an asexually reproductive process of apicomplexa. After infecting a host cell, a trophozoite (see glossary below) increases in size while repeatedly replicating its nucleus and other organelles. During this process, the organism is known as a meront or schizont. Cytokinesis next subdivides the multinucleated schizont into numerous identical daughter cells called merozoites (see glossary below), which are released into the blood when the host cell ruptures. Organisms whose life cycles rely on this process include Theileria, Babesia, as well as the malaria parasite Plasmodium.

Sporogony is a type of sexual and asexual reproduction. It involves karyogamy, the formation of a zygote which is followed by meiosis and multiple fission. This results in the production of sporozoites.

Other forms of replication include endodyogeny and endopolygeny.

Endodyogeny is a process of asexual reproduction, favoured by parasites such as Toxoplasma gondii. It involves an unusual process in which two daughter cells are produced inside a mother cell, which is then consumed by the offspring prior to their separation.

Endopolygeny is the division into several organisms at once by internal budding.

Glossary of cell types

An ookinete (motile), a sporozoite (motile) and a merozoite (non-motile) of Plasmodium falciparum.

Infectious stages

A sporozoite (G. sporos, seed + zōon, animal) is the cell form that infects new hosts. In Plasmodium, for instance, the sporozoites are cells that develop in the mosquito's salivary glands, leave the mosquito during a blood meal, and enter liver cells (hepatocytes) where they multiply. Cells infected with sporozoites eventually burst, releasing merozoites into the bloodstream. Sporozoites are motile and they move by gliding.

A merozoite (G. meros, part [of a series], +zōon, animal) is the result of merogony that takes place within a host cell. In coccidiosis, merozoites form the first phase of the internal life cycle of coccidian. In the case of Plasmodium, merozoites infect red blood cells and then rapidly reproduce asexually. The red blood cell host is destroyed by this process, which releases many new merozoites that go on to find new blood-borne hosts. Merozoites are non-motile.

A gametocyte (G. gametēs, partner + kytos, hollow) is a name given to a parasite's gamete-forming cells. A male gametocyte divides to give many flagellated microgametes, whereas the female gametocyte differentiates to a macrogamete.

An ookinete (G. ōon, egg + kinētos, motile) is a fertilised zygote capable of moving spontaneously. It penetrates epithelial cells lining the midgut of mosquitos to form a thick-walled structure known as an oocyst under the mosquito's outer gut lining. Ookinetes are motile and they move by gliding.

A trophozoite (G. trophē, nourishment + zōon, animal) is the activated, intracellular feeding stage in the apicomplexan life cycle. After gorging itself on its host, the trophozoite undergoes schizogony and develops into a schizont, later releasing merozoites.

A bradyzoite (G. bradys, slow + zōon, animal) is a sessile, slow-growing form of zoonotic microorganisms such as Toxoplasma gondii, among others responsible for parasitic infections. In chronic (latent) toxoplasmosis, bradyzoite microscopically presents as clusters enclosed by an irregular crescent-shaped wall (a pseudocyst), in infected muscle and brain tissues.

A tachyzoite (G. tachys, fast + zōon, animal), contrasting with a bradyzoite, is a form typified by rapid growth and replication. Tachyzoites are motile forms of coccidians that form tissue cysts, such as Toxoplasma and Sarcocystis. Typically infecting cellular vacuoles, tachyzoites divide by endodyogeny and endopolygeny.

An oocyst (G. ōon, egg + kystis, bladder) is a hardy, thick-walled spore able to survive for lengthy periods outside a host. The zygote develops within the spore, which acts to protect it during transfer to new hosts. Organisms that create oocysts include Plasmodium, Cryptosporidium and Toxoplasma.

• Lifecycle of the Babesia parasite

• Lifecycle of the Eimeria parasite

• Erythrocytic lifecycle of the Plasmodium parasite

• Lifecycle of the Toxoplasma parasite

See also

• Trematode lifecycle stages

References

UpToDate Contents

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• 1. クリプトスポリジウム症の治療および予防 treatment and prevention of cryptosporidiosis
• 2. シクロスポラ感染症 cyclospora infection
• 3. クリプトスポリジウム症の疫学、臨床症状、および診断 epidemiology clinical manifestations and diagnosis of cryptosporidiosis
• 4. イソスポーラ感染の疫学、臨床症状、および診断 epidemiology clinical manifestations and diagnosis of cystoisospora infections
• 5. 先天性トキソプラズマ症：臨床的特徴および診断 congenital toxoplasmosis clinical features and diagnosis

English Journal

• Prevalence of anti-Toxoplasma gondii antibody in domestic horses in Japan.

• Masatani T1, Takashima Y2, Takasu M3, Matsuu A4, Amaya T5.
• Parasitology international.Parasitol Int.2016 Apr;65(2):146-50. doi: 10.1016/j.parint.2015.11.006. Epub 2015 Nov 30.
• The present study is the first report that investigated the seroprevalence of Toxoplasma gondii infection in domestic horses in various prefectures of Japan and analyzed risk factors for seropositivity. We performed a latex agglutination test for riding/racing horses from 11 prefectures in Japan (78
• PMID 26593178

• Use of aerobic spores as a surrogate for cryptosporidium oocysts in drinking water supplies.

• Headd B1, Bradford SA2.
• Water research.Water Res.2016 Mar 1;90:185-202. doi: 10.1016/j.watres.2015.12.024. Epub 2015 Dec 17.
• Waterborne illnesses are a growing concern among health and regulatory agencies worldwide. The United States Environmental Protection Agency has established several rules to combat the contamination of water supplies by cryptosporidium oocysts, however, the detection and study of cryptosporidium ooc
• PMID 26734779

• Evaluating the Transport of Bacillus subtilis Spores as a Potential Surrogate for Cryptosporidium parvum Oocysts.

• Bradford SA1, Kim H2, Headd B1, Torkzaban S3.
• Environmental science & technology.Environ Sci Technol.2016 Feb 2;50(3):1295-303. doi: 10.1021/acs.est.5b05296. Epub 2016 Jan 13.
• The U.S. Environmental Protection Agency has recommended the use of aerobic spores as an indicator for Cryptosporidium oocysts when determining groundwater under the direct influence of surface water. Surface properties, interaction energies, transport, retention, and release behavior of B. subtilis
• PMID 26720840

Japanese Journal

• Molecular characterization of Cryptosporidium parvum detected in Japanese black and Holstein calves in Iwate Prefecture and Tanegashima Island, Kagoshima Prefecture, Japan

• AITA Junya,ICHIKAWA-SEKI Madoka,KINAMI Aiko,YAITA Seiko,KUMAGAI Yoshihiro,NISHIKAWA Yoshifumi,ITAGAKI Tadashi
• Journal of Veterinary Medical Science advpub(0), 2015
• … The DNA fragments of 18S ribosomal RNA (18S rRNA) gene were amplified by a nested PCR from 43 oocyst-positive as well as one oocyst-negative samples. … parvum oocyst-positive calves ranged in age from 6 to 13 days old and significantly have watery diarrhea (P<0.05). … Sequences of the gene encoding the 60-kDa glycoprotein (GP60) in 43 Cryptosporidium oocyst-positive samples were identical to that of the zoonotic IIaA15G2R1 subtype. …
• NAID 130005061000

• Seroprevalences of Toxoplasma gondii and Neospora caninum in Pet Rabbits in Japan

• SALMAN Doaa,OOHASHI Eiji,MOHAMED Adel Elsayed Ahmed,ABD EL-MOTTELIB Abd El-Raheem,OKADA Tadashi,IGARASHI Makoto
• Journal of Veterinary Medical Science 76(6), 855-862, 2014
• … caninum in pet rabbits in Japan as an indicator of the possible oocyst contamination in the environment surrounding human beings. … The results of this study indicate low seroprevalences of toxoplasmosis and neosporosis in pet rabbits in Japan, suggesting low oocyst contamination in the human environment. …
• NAID 130003391296

• Seroprevalences of Toxoplasma gondii and Neospora caninum in Pet Rabbits in Japan

• SALMAN Doaa,OOHASHI Eiji,MOHAMED Adel Elsayed Ahmed,ABD EL-MOTTELIB Abd El-Raheem,OKADA Tadashi,IGARASHI Makoto,五十嵐 慎
• Journal of Veterinary Medical Science 76(6), 855-862, 2014
• … caninum in pet rabbits in Japan as an indicator of the possible oocyst contamination in the environment surrounding human beings. … The results of this study indicate low seroprevalences of toxoplasmosis and neosporosis in pet rabbits in Japan, suggesting low oocyst contamination in the human environment.https://www.jstage.jst.go.jp/article/jvms/76/6/76_13-0632/_article/-char/ja/ …
• NAID 120005590224

Related Links

• オーシスト（Oocyst）

宿主体内に排泄されたoocystは一般に強い耐性をもつ。 ザイゴートはこの中で分裂して スポロシスト およびスポロゾイト （sporozoite）を形成する。 分裂前の単細胞の状態を スポロント、 スポロシストを形成する前の分裂してできた細胞の 集合体をスポロブラスト ...

Related Pictures

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★リンクテーブル★

リンク元	「100Cases 33」「オーシスト」
拡張検索	「sporulated oocyst」

「100Cases 33」

　　[★]

☆case33　頭痛と混乱

■glossary

accompany

vt.

(人)と同行する、(人)に随行する。(もの)に付随する。～と同時に起こる。～に加える(添える、同封する)(with)

slurred n. 不明瞭

強直間代痙攣 tonic-clonic convulsion

　意識消失とともに全身の随意筋に強直痙攣が生じ(強直痙攣期tonic convulsion)、次いで全身の筋の強直と弛緩とが律動的に繰り返される時期(間代痙攣期clonic convulsion)を経て、発作後もうろう状態を呈する一連の発作。

■症例

28歳、女性　黒人　南アフリカ　手術室看護師　ロンドン住在

主訴：頭痛と混乱

現病歴：過去3週間で頭痛が続いており、ひどくなってきた。現在も頭痛が持続しており、頭全体が痛い。友人曰く「過去六ヶ月で体重が10kg減っていて、最近、混乱してきたようだ」。発話は不明瞭。救急室にいる間に強直間代痙攣を起こした。

・診察 examination

やせている。55kg。38.5℃。口腔カンジダ症(oral candidiasis)。リンパ節腫脹無し。心血管、呼吸器系、消化器系正常。痙攣前における神経検査では時間、場所、人の見当識無し。神経局所症状無し(no focal neurological sign)。眼底両側に乳頭浮腫有り。

・検査 investigation

血算：白血球増多

血液生化学：ナトリウム低下

CT：供覧

■キーワード＆着目するポイント

・口腔カンジダ症(oral candidiasis)

・頭痛、精神症状、強直間代痙攣

・眼底両側に乳頭浮腫

・CT所見

・低ナトリウム血症は二次的なもの

■アプローチ

・口腔カンジダ症(oral candidiasis)　→　細胞免疫低下状態(DM、免疫抑制、AIDSなど) or 常在細菌叢の攪乱(長期の抗菌薬の使用)

　・The occurrence of thrush in a young, otherwise healthy-appearing person should prompt an investigation for underlying HIV infection.(HIM.1254)

　・More commonly, thrush is seen as a nonspecific manifestation of severe debilitating illness.(HIM.1254)

・精神症状、強直間代痙攣　→　一次的、あるいは二次的な脳の疾患がありそう

・頭痛　→　漠然としていて絞れないが、他の症状からして機能性頭痛ではなく症候性頭痛っぽい。

・眼底両側に乳頭浮腫　→　脳圧亢進の徴候　→　原因は・・・脳腫瘍、ことにテント下腫瘍と側頭葉の腫瘍、クモ膜下出血、脳水腫など、そのほか、眼窩内病変、低眼圧などの局所的要因、悪性高血圧、血液疾患、大量出血、肺気腫などの全身的要因 (vindicate本のp342も参考になる)

　・頭痛と脳圧亢進　→　頭蓋内圧占拠性病変、脳炎(IMD.274)

・CT所見　→　ringformの病変、脳浮腫、脳圧亢進

・低ナトリウム血症　→　脳ヘルニアに続発して起こることがあるらしい。実際には下垂体にトキソプラズマによる病変が形成されることにより起こりうる。

・そのほか出身地、体重減少もHIVを疑わせる点

パターン認識でHIV + 精神症状 + てんかん発作(強直間代痙攣) + 脳圧亢進 + CT所見 = 一番ありそうなのはToxoplasma gondiiによるトキソプラズマ脳症 cerebral toxoplasosis (トキソプラズマ脳炎 toxoplasmic encephalitis)

■Toxoplasma gondii

　原虫　胞子原虫類

(感染予防学 080521のプリント、CASES p,92、HIM p.1305-)

・疫学：西洋では30-80%の成人がトキソプラズマの感染の既往がある・・・うぇ(CASES)。日本では10%前後(Wikipedia)。

・生活環

　・終宿主：ネコ：ネコの小腸上皮細胞で有性・無性生殖　糞便にオーシストの排泄

　・中間宿主：ヒト.ブタを含むほ乳類と鳥類：無性生殖で増殖、シストの形成

　　　急性期の増殖盛んな急増虫体tachyzoiteとシスト内の緩増虫体bradyzoite

・病原、病因 phathogenesis

　・緩増虫体(bradyzoite)、接合子嚢(oocyst)

・感染経路

　1. オーシストの経口摂取

　2. 中間宿主の生肉中のシストの経口摂取

　3. 初感染妊婦からの経胎盤感染。既感染なら胎盤感染しないらしい(HIM.1306)

　(4)移植臓器、輸血。確率は低い(at low rate)(HIM.1306)

・病態

　1. 先天性トキソプラズマ症　congenital toxoplasmosis

　　　①網脈絡膜炎、 ②水頭症、 ③脳内石灰化、 ④精神・運動障害

　2. 後天性トキソプラズマ症　acquired toxoplasmosis

　　(1) 健常者

　　　・多くは不顕性感染。発熱、リンパ節腫脹、皮疹(rash)

　　　・(少数例)筋肉痛、暈疼痛、腹痛、斑状丘疹状皮疹(maculopapular rash)、脳脊髄炎、混乱(HIM.1308)

　　　・(まれ)肺炎、心筋炎、脳症、心膜炎、多発筋炎

　　　・網膜、脈絡叢に瘢痕や、脳に小さい炎症性の病変を残すことあり(CASES)。

　　　・急性感染の症状は数週間で消失　筋肉や中枢神経系に緩増虫体が残存

　　(2)HIV感染者、臓器移植例、がん化学療法例

　　　シスト内緩増虫体→急増虫体→播種性の多臓器感染

　　　AIDSでは、トキソプラズマ性脳炎が指標疾患 AIDS-defineing illness(CASES)

・治療

　(日本)アセチルスピラマイシン、ファンシダール(感染予防学 080521)

■トキソプラズマ脳炎 toxoplasmic encephalitis、トキソプラズマ脳症 cerebral toxoplasosis

・症状

　発熱、頭痛、混乱ｍ、痙攣、認知の障害、局所神経徴候(不全片麻痺、歯垢、脳神経損傷、視野欠損、感覚喪失)(CASES)

・画像検査

　(CT,MRI)多発性、両側性、ring-enhancing lesion、特に灰白質-白質境界、大脳基底核、脳幹、小脳が冒されやすい(CASES)

・鑑別診断(臨床症状・画像診断の所見で)

　リンパ腫、結核、転移性脳腫瘍(CASES)

・病歴と画像所見からの鑑別診断

　リンパ腫、結核、転移性腫瘍

？

このCTがcerebral toxoplasmosisに特徴的かは不明

□最後に残る疑問

　AIDSでWBC(leukocyte)の数はどうなるんだろう？？？AIDSの初診患者ではWBCが低い人が多いらしいし()、HIVはCD4+ T cellとmacrophageに感染して殺すから、これによってB cellは減るだろうし、CD8+ T cellも若干減少するだろうからWBCは減るんじゃないか？！好中球はAIDSとは関係ない？好中球は他の感染症に反応性に増加している？ちなみに、好酸球は寄生虫(原虫)の感染のために増える傾向にあるらしい(HIMのどこか)。

スルファジアジン

sulfadiazine

ピリメタミン

pyrimethamine

葉酸拮抗剤である。

サルファ剤と併用され、抗トキソプラズマ薬、抗ニューモシチス・カリニ薬として相乗的に働く。

ST合剤

SMX-TMP

スルファメトキサゾール・トリメトプリム合剤 sulfamethoxazole and trimethoprim mixture

□AIDSの定義(http://en.wikipedia.org/wiki/CDC_Classification_System_for_HIV_Infection_in_Adults_and_Adolescents)

• According to the US CDC definition, one has AIDS if he/she is infected with HIV and present with one of the following:

A CD4+ T-cell count below 200 cells/μl (or a CD4+ T-cell percentage of total lymphocytes of less than 14%).

or he/she has one of the following defining illnesses:

• 01. Candidiasis of bronchi, trachea, or lungs
• 02. Candidiasis esophageal
• 03. Cervical cancer (invasive)
• 04. Coccidioidomycosis, disseminated or extrapulmonary
• 05. Cryptococcosis, extrapulmonary
• 06. Cryptosporidiosis, chronic intestinal for longer than 1 month
• 07. Cytomegalovirus disease (other than liver, spleen or lymph nodes)
• 08. Encephalopathy (HIV-related)
• 09. Herpes simplex: chronic ulcer(s) (for more than 1 month); or bronchitis, pneumonitis, or esophagitis
• 10. Histoplasmosis, disseminated or extrapulmonary
• 11. Isosporiasis, chronic intestinal (for more than 1 month)
• 12. Kaposi's sarcoma
• 13. Lymphoma Burkitt's, immunoblastic or primary brain
• 14. Mycobacterium avium complex
• 15. Mycobacterium, other species, disseminated or extrapulmonary
• 16. Pneumocystis carinii pneumonia
• 17. Pneumonia (recurrent)
• 18. Progressive multifocal leukoencephalopathy
• 19. Salmonella septicemia (recurrent)
• 20. Toxoplasmosis of the brain
• 21. Tuberculosis
• 22. Wasting syndrome due to HIV

People who are not infected with HIV may also develop these conditions; this does not mean they have AIDS. However, when an individual presents laboratory evidence against HIV infection, a diagnosis of AIDS is ruled out unless the patient has not:

• undergone high-dose corticoid therapy or other immunosuppressive/cytotoxic therapy in the three months before the onset of the indicator disease
• OR been diagnosed with Hodgkin's disease, non-Hodgkin's lymphoma, lymphocytic leukemia, multiple myeloma, or any cancer of lymphoreticular or histiocytic tissue, or angioimmunoblastic lymphoadenopathy
• OR a genetic immunodeficiency syndrome atypical of HIV infection, such as one involving hypogamma globulinemia

AND

• the individual has had Pneumocystis carinii pneumonia
• OR one of the above defining illnesses AND a CD4+ T-cell count below 200 cells/μl (or a CD4+ T-cell percentage of total lymphocytes of less than 14%).

□AIDSのステージング

• Revised World Health Organization (WHO) Clinical Staging of HIV/AIDS For Adults and Adolescents (2005)

• http://en.wikipedia.org/wiki/WHO_Disease_Staging_System_for_HIV_Infection_and_Disease_in_Adults_and_Adolescents

■参考文献

HIM = Harrison's Principles of Internal Medicine 17th Edition

CASES = 100 Cases in Clinical Medicine Second edition

IMD = 内科診断学第2版

「オーシスト」

　　[★]

英

oocyst

同

接合子嚢、胞嚢体

「sporulated oocyst」

　　[★]

sporulate oocyst

• スポロゾイト形成オーシスト、スポロゾイト形成接合子嚢