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犬と猫のジアルジア症に関する研究
https://az.repo.nii.ac.jp/records/3208
https://az.repo.nii.ac.jp/records/32089bd02bdc-4eeb-44b7-9b53-c290f5be29ea
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diss_dv_otsu0285 (4.9 MB)
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diss_dv_otsu0285_jab&rev (290.5 kB)
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diss_dv_otsu0285_jab.pdf (204.5 kB)
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| Item type | 学位論文 / Thesis or Dissertation(1) | |||||||||
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| 公開日 | 2013-02-05 | |||||||||
| タイトル | ||||||||||
| タイトル | 犬と猫のジアルジア症に関する研究 | |||||||||
| タイトル | ||||||||||
| タイトル | Studies on canine and feline giardiasis | |||||||||
| 言語 | en | |||||||||
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| 言語 | jpn | |||||||||
| 資源タイプ | ||||||||||
| 資源タイプ | thesis | |||||||||
| 著者 |
菅野, 紘行
× 菅野, 紘行
× Sugano, Hiroyuki
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| 抄録 | ||||||||||
| 内容記述タイプ | Abstract | |||||||||
| 内容記述 | ジアルジア症はヒトを始めとして各種動物に広く発生するが，病原となる原虫の種の異同については，色々と論議があり，定説となるものはない。また動物からヒトへのジアルジアの感染の可能性も示唆されており，動物に寄生するジアルジアに関する研究は人畜共通寄生虫症と言う観点からも重要である。 わが国では，ヒトのジアルジア症の報告は多数見られるが，動物に関しては，セキセイインコの症例報告を除けば疾病との関連を示唆する報告があるにすぎない。現実には犬と猫，特に幼犬にジアルジア症が頻発しているにもかかわらず，ジアルジア原虫の生物学的研究，あるいは本症の臨床的研究が系統的に行われているとはいえない。 著者はまず，犬と猫由来のジアルジアの栄養型とシストの比較形態的な観察を行い，さらに感染性の株差を知るために交差感染実験を行った。また，ジアルジア感染は不顕性であることが多いため，実験的に発症要因の特定を試みるとともに，疫学的観察結果に基づいて要因の推定を行った。また，本症の症状として最も普通にみられる下痢の発生機序を明らかにする目的で，腸の病理組織学的検索を実施した。本症の確定診断が糞便中の虫体検出以外にないことから，簡便で確実な虫体検出法を確立する目的で，各種の原虫検査法について比較検討を行った。さらに，本症の治療法の開発を試み，また予防的見地からシストの抵抗性について実験を行った。得られた結果は以下のとおりである。 虫体の形態 ジアルジア原虫には，鞭毛をもち運動性のある栄養型と，被膜に包まれ卵円形で鞭毛も運動性もないシストの2つの型がある。栄養型は無性的に分裂増殖するが感染力はなく，シストは休眠形で増殖はしないが感染力がある。この2型について，犬と猫に寄生している原虫を形態的に比較した。 犬と猫由来の栄養型を染色標本について観察すると，虫体は前方が丸く，後方が尖った逆ラッキョウ形を呈し，体は左右相称で2個の核があり，鞭毛は左右に計8本認められた。シストは卵円形あるいは楕円形で光を屈折する嚢に包まれ，虫体内部には2個または4個の核が認められた。光学顕微鏡的所見では，犬と猫の虫体は，栄養型とシストのいずれにおいても宿主による形態的な差が認められず，その計測値にも差はみられなかった。 感染性と発症 種々の宿主から得られるジアルジア属の種の異同については不明な点が多く研究者により説が分れ，また，相互の感染性についても過去の研究結果は必ずしも一致しない。今回，犬株と猫株を用いて同種宿主間および異種宿主間の感染実験を行ったところ，同種宿主間では比較的容易に感染が成立したが，異種宿主間では感染の成立しない場合が多く，株により感受性に差が見られた。また，猫では犬に比べて異種，同種宿主間共に感染が成立しにくかった。 ジアルジア症は幼獣に発生が多いことから，発症と年齢の関係について調査を行った。発症例はほとんどがブリーダーまたはペットショップから購入された4カ月齢以下の幼獣で，購入後3～6日目に発症したものであった。これらの幼獣を生産したブリーダーの繁殖用親獣の糞便検査を行ったところ，発症した子犬や子猫を産んだ母獣全部からジアルジアのシストが検出された。ジアルジア感染は多くは不顕性で，成獣は感染しても無症状でキャリアーとなり，シストを排出する。幼獣は同居時に母獣から感染をうけるが発症せず，畜主に購入されて母獣から分離され新しい環境に移された場合に発症すると考えられる。このことは，免疫低下をもたらす副腎皮質ホルモンの投与により，実験的に臨床症状の悪化と排出原虫数の増加をきたすことからも裏付けられた。 ジアルジアの病原性については，ヒトでは下痢や急性胃腸炎，胆道・胆嚢の疾患を引き起こすとされているが，犬，猫に関しては意見がわかれている。著者の観察では幼獣ほど下痢が激しく，幼獣の激症例には，粘液や血液を混じた重篤な下痢症状を示すものが見られた。また，感染犬の腸の病理組織学的所見では，原虫の腸粘膜上皮細胞への侵入は認められなかったが，絨毛上皮の杯細胞の増数が著明であった。すなわち，原虫は絨毛間で増殖し腸の粘膜を刺激して炎症をうながし，そのため下痢が発生すると考えられた。 診断法と治療法 ジアルジア感染は多くの場合不顕性で，有症の場合でも特徴的な症状はなく，確定診断は糞便中の原虫の検出によるしかない。そこで検出の際の操作にともなう栄養型とシストの形態的な変化の有無および検出手技の簡便さを基準として，既存の消化管原虫検査法の中から，臨床に応用出来るジアルジアの検査法を検討した。その結果，最も簡便で確実な方法は，栄養型とシストのいずれの場合もヨード染色改良法であった。種々のヨード染色法のうちで，生理食塩液で希釈した糞便をスライドグラスに塗抹し，まず蠕虫卵を検査したのち少量のヨード液を滴下して染色する方法が最も検出に適していた。一方，診断の際に虫体検出をより確実にするため，糞便中に排出される原虫数の経時的な変動を調べた。その結果，糞便中への原虫の排出は非常に不規則に変動することが明らかになった。したがって診断の確実さを期するには，糞便検査は2～3日おきに数回行う必要がある。 本症の治療法に関しては，外国ではヒトをはじめ犬，猫など各種動物について多くの報告がある。わが国ではヒトの治験例は多数報告されているが動物の報告例は少なく，セキセイインコの1例だけである。また，犬のジアルジア寄生例は報告されているが，猫の寄生例や犬，猫での発症例の報告はみられない。著者は犬と猫における本症を確認し，治療法の開発を目的として実験を行った。現在，ジアルジア症の治療にはキナクリン，フラゾリドン，メトロニダゾールなどが使用されているが，キナクリンはわが国では入手出来ず，フラゾリドンは薬効にやや問題がある。そこでヒトの本症で最も多く使用されているメトロニダゾールを用いて最適投与量および投与法を検討した。その結果メトロニダゾールは犬，猫共に60mg/kg，1日1回，6～7日間の投与で臨床症状の改善と原虫の永久的な陰転が認められた。 シストの抵抗性 ジアルジアの感染はシストによって行われる。したがって，本症の予防はシストの殺滅によって達せられる。そこでシストの抵抗力を知る目的で実験を行った。犬株と猫株のシストを2%オルソ剤液，2%複合ヨードホール剤液，65℃温湯，100℃熱湯に入れた場合と乾燥状態に放置した場合におけるシストの生死を0.5%エオジン染色により判定した結果，オルソ剤と複合ヨードホール剤では，30分後に50～70%が死滅したにすぎなかったが，65℃の温湯では5分，100℃の熱湯では2分でほとんどが死滅した。また，乾燥処置では処置後2分で78．8%，30分後ではほとんどが死滅した。したがって感染予防には，動物の飼育場所や飼育舎などを熱湯で洗浄したのちよく乾燥させるのがよい。 |
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| Abstract | ||||||||||
| 内容記述タイプ | Other | |||||||||
| 内容記述 | Giardiasis occurs in a variety of animals including man, but the results have been divergent by different authors on the taxonomy of the causative agent, Giardia species, from different host animals. Giardiasis is one of the important zoonoses because the transmission of the agent from animals to man has been suggested. In Japan, some human cases of giardiasis have been reported, whereas no report has been published on the clinical disease of animals except that of budgerigars and those which suggested the involvement of Giardia parasites with some diseases. However, clinical cases of giardiasis occur frequently in dogs and cats especially puppies, nevertheless no studies have been done on the biology of and disease by the agent, Giardia species. In this study, the canine and feline strains of Giardia were compared to each other in morphology and infectivity. Giardia infections are usually subclinical and occasionally develop symptoms under some physical and environmental conditions. Experiments were done to know the causative factors for the infections to become symptomatic in addition to epidemiological observations. Furthermore, the intestinal lesions of infected dogs were examined pathohistologically in order to know the pathogenic mechanisrn by which Giardia infections become symptomatic. Giardiasis can be certainly diagnosed only by detection of the causative agents in the feces, so that the most simple and effective detection technique must be developed for diagnosis of Giardia infections. Many techniques for the detection of intestinal protozoan parasites were examined on the basis of technical simplicity and effectiveness for the detection of Giardia trophozoites and cysts. Furthermore, an attempt was made to find the most effective treatment and determine the resistance of cysts in the laboratory to know the preventive measures of giardiasis. Comparative morphology of Giardia of canine and feline origins Giardia species have two developmental stages, pyriform trophozoites with eight flagella and ovoid or subelliptical cysts which are non-motile and surrounded by a wall but have no flagella. Trophozoites proliferate asexually by longitudinal binary fission and are not infective to animals, whereas cysts, a resistant and inactive form, do not proliferate but is infective. The canine and feline strains of Giardia were compared to each other in the morphology of trophozoites and cysts. Observation of iodine-stained specimens by light microscopy revealed that trophozoites are pyriform to ellipsoidal, bilaterally symmetrical, and have one nucleus and four flagella on each side; and the anterior and the posterior ends are broadly rounded and attenuated, respectively. Cysts are ovoidal or subelliptical, with two or four nuclei according to development and are enveloped by a wall which refracts light. No difference was found in the morphology and measurements of trophgozoites and cysts between the canine and feline strains. Infectivity of Giardia and development of symptoms With the taxonomy of Giardia species obtained from many species of hosts and the infectivity to different species of hosts, the results have been divergent by authors. In this study, experimental cross and non-cross infections with canine and feline strains of Giardia showed that each strain easily infected the definite host but hardly infected the indefinite host: that is, each strain was fairly host-specific. Furthermore, cats were more resistant to the challenge infection with both Giardia strains, compared with dogs. This will endorse that clinical cases occur in smaller number in cats than in dogs. Futhermore, the relation between diseased animals and their age was surveyed because giardiasis generally occurs in younger animals. Almost all the animals that developed symptoms were under four months old, and symptoms developed 3 to 6 days after the animals were purchased by owners and removed to different environment. Fecal examination of the breeding adult animals of the farms where the diseased young animals were produced revealed that most of the adult animals shed Giardia cysts in the feces and all the dams that bore the diseased young animals shed cysts. Giardia infections are usually subclinical and adult animals become the carrier of the protozoan parasite and shed cysts when they are infected with the parasite. It is likely that young animals are infected with cysts from their mothers without any symptoms while they live with their mothers, but they develop symptoms when separated from their mother and removed to different environment of owners. This was endorsed by the experiments that the subclinical infections became symptomatic and Giardia organisms excreted in the feces increased in number by treatment of infected animals with adrenocortiotropic hormone, an immunosuppressive agent. As the symptoms of human Giardia infections, diarrhoea, acute gasteroenteritis, cholangitis and cholecystitis have been reported, whereas the opinions are widely diverse by authors in canine and feline infections. According to the present observations more severe diarrhoea developed in younger animals and grave diarrhoea with mucous and blood occurred in fulminating cases of young animals. Pathohistological observation of intestinal lesions of infected dogs showed that no parasites were observed to invade into the epithelium of small intestine, but that the number of goblet cells markedly increased in the mucous membrane of villi. Accordingly, it is likely that Giardia parasites propagate among the villi and stimulate the intestinal mucous membrane to cause inflammation and consequently to develop diarrhoea. Diagnosis and treatment Giardiasis is generally subclinical and, even in symptomatic cases, shows no characteristic clinical signs, so a diagnosis must be made by detection of trophozoites and/or cysts in feces. In order to find the optimum technique for detection of Giardia parasites, some technical methods reported for detection of human intestinal protozoan parasites were examined on the basis of technical simplicity and effectiveness and of deformation of trophozoites and cysts. Consequently, some iodine-staining techniques were the most simple and effective for detection of Giardia trophozoites and cysts. Among these iodine-staining techniques, the best was that in which a small amount of feces was put in a drop of physiological saline on a slide glass and examined for eggs of helminth parasites without staining and after that for Giardia organisms after stained with the iodine-solution. To diagnose Giardia infections more accurately, the daily fluctuation in the number of Giardia trophozoites and/or cysts excreted in the feces was determined with the result that the organisms were excreted irregularly in the feces. Accordingly, the more accurate diagnosis of Giardia infections will be attained by repeated fecal examinations every 2 or 3 days. Many studies have been done on the treatment of giardiasis of man and animals including dogs and cats in other countries, whereas in Japan no report has been published on the treatment of animal giardiasis except a clinical case of budgerigars although the treatment of some human cases has been reported. Furthermore, in Japan no clinical cases have been reported in cats although some reports have been published on canine cases. Quinacrine, furazolidone and metronidazole preparations are prescribed for human giardiasis, but quinacrine preparations are not on the market in Japan and furazolidone is not so effective to the infection. In this study, experiments were carried out for the treatment of giardiasis of dogs and cats. A metronidazole preparation, which is widely prescribed for human trichomoniasis and giardiasis, was determined for the optimum dose against giardiasis of dogs and cats. As the results, metronidazole was efficacious against canine and feline giardiasis in a dose of 60 mg/kg body weight, when orally administered once a day for consecutive 6 to 7 days, to result in the improvement of clinical manifestations and permanent eradication of the agents from the feces. Resistance of cysts Giardia infection is transmitted to host animals only with cysts, so that the prophylaxis of the infection can be attained by killing cysts. Consequently, experiments were performed to know the resistance of cysts: that is, cysts of canine or feline origin were put in 2% orthodichlorobenzene and 2% povidone-iodine solutions and in hot water of 65 C and 100 C and were dried by leaving them on a glass-slide in the laboratory. When the viability of cysts was judged by staining with 0.5% eosin solution, 50 to 70% of the cysts were killed 30 minutes after treated in the antiseptic solutions, whereas almost all the cysts lost their viability 5 minutes after immersed in the host water. When left dry on a slide, 78.8% and almost all the cysts were inactivated 2 and 30 minutes later respectively. Consequently, the transmission of cysts among animals will be best prevented by washing the breeding site of animals with plenty of hot water and after that by drying sufficiently. |
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| 学位名 | ||||||||||
| 学位名 | 獣医学博士 | |||||||||
| 学位授与機関 | ||||||||||
| 学位授与機関名 | 麻布大学 | |||||||||
| 学位授与年月日 | ||||||||||
| 学位授与年月日 | 1990-04-12 | |||||||||
| 学位授与番号 | ||||||||||
| 学位授与番号 | 乙第285号 | |||||||||
| 著者版フラグ | ||||||||||
| 出版タイプ | AM | |||||||||
| 出版タイプResource | http://purl.org/coar/version/c_ab4af688f83e57aa | |||||||||
