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豚のゲタウイルス感染症に関する研究
https://az.repo.nii.ac.jp/records/3215
https://az.repo.nii.ac.jp/records/3215dd90c215-64c6-414d-860c-a5291679b1d7
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diss_dv_otsu0302 (7.9 MB)
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diss_dv_otsu0302_jab&rev (297.8 kB)
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diss_dv_otsu0302_jab.pdf (186.8 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 | 豚のゲタウイルス感染症に関する研究 | |||||
| タイトル | ||||||
| タイトル | Studies on getah virus infection in swine : pathogenicity of the virus in piglets | |||||
| 言語 | en | |||||
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| 言語 | jpn | |||||
| 資源タイプ | ||||||
| 資源タイプ識別子 | http://purl.org/coar/resource_type/c_46ec | |||||
| 資源タイプ | thesis | |||||
| 著者 |
矢後, 啓司
× 矢後, 啓司× Yago, Keiji |
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| 抄録 | ||||||
| 内容記述タイプ | Abstract | |||||
| 内容記述 | ゲタウイルスはいわゆるアルボウイルスの一つで，わが国では主としてキンイロヤブカに媒介されて伝播し，豚もかなり高率に感染するが，その発症例は全く知られていなかった。著者は神奈川県下で発生する豚の主要疾病の原因調査に従事してきたが，同腹の初生豚に，顔面の腫脹と神経症状を主とした疾病が集中的に発生し，死亡する症例に遭遇し，その原因がゲタウイルス感染によることを初めて明らかにした。また，抗体調査からみた感染の動向に基づいて，その発生要因についても考察した。 1. 病性鑑定からみた神奈川県下の豚疾病の発生動向 1983～1987年の5年間にわたり，養豚経営上重要な疾病の病性鑑定を行なった。当時，神奈川県では県央地区を中心に16万余頭の豚が繁殖，育成，肥育の一貫経営を主軸に飼養されていたが，経営の障害となる疾病としては，急性伝染病は減少し，慢性疾病が増加の傾向にあり，また，異常産に関するもの(10～33%)や哺乳中の子豚に関するもの(17～38%)が多かった。その原因としては，オーエスキー病，ヘモフィルスやパスツレラによる肺炎，大腸菌症，日本脳炎，豚パルボウイルス感染症，伝染性胃腸炎，トキソプラズマ病等が主なものであった。その中で1985年および1987年に，同腹初生豚に集中的に発生した2件の症例がゲタウイルス感染に基因することが確認された。 2. 豚ゲタウイルス感染症の発生の確認 発生状況:1985年10月，藤沢市の兼業養豚場で生まれた1腹12頭の初生豚が生後間も無く元気を喪失し，ふるえ等の神経症状を呈して起立不能にいたり，3日目までに8頭が死亡，残り4頭もかなり重症であったが徐々に回復した(発生症例 1)。 また，1987年10月，秦野市の兼業養豚場で1腹，11頭が分娩されたが，うち2頭は死産胎子であった。残り9頭は順調に発育したが生後23日から全頭，顎下部など顔面が腫脹し，ふるえ，歩行異常等の神経症状を示し，翌日2頭が死亡，ひん死の1頭は検査のため殺処分された。残りの子豚は徐々に回復した(発生症例 2)。 発生症例1，2とも，母豚と周囲の豚には全く異常は認められなかった。 病理学的所見:発生症例1，2を通じて，皮下の膠様浸潤が目立ったが，他には肺，肝，脾，腎，リンパ節等の軽度の水腫性病変以外，特記すべき病変は認められなかった。 原因学的検査所見:発生症例1の死亡子豚5頭の諸臓器および発生症例2の2頭の子豚の諸臓器について細菌学的に検査したが，病原的に意義のある細菌は検出されなかった。次いで，発生症例1の諸臓器(脳，扁桃，肝，脾，腎，腸管)の乳剤および発生症例2の諸臓器(脳，扁桃，肺，肝，脾，腎)の乳剤を，ハムスター由来のHmLu-1細胞培養に接種したところ，検査したどの臓器からも明瞭な細胞変性効果を示す一種のウイルスが検出され，その感染価は発生症例1では10^3.0-10^6.25/g，発生症例2では10^2.5-10^4.5/gの範囲であった。 発生症例1および発生症例2から分離されたウイルスは，その細胞変性効果の類似性から同一性状のものと推定され，また，回復血清を用いた中和試験でも区別できなかった。両発生症例の急性期および生残子豚の回復期(発生症例1で53日後，発生症例2では44日後)の血清について分離ウイルスに対する中和抗体価の変動を調べたところ，急性期血清はすべて陰性，回復期血清はすべて陽性(発生症例1では320-490倍，発生症例2では160-320倍)であり，どの豚もこのウイルス感染を経験したことを示した。以上の成績からこれらの発生症例は分離ウイルスの感染によって起こったことが確認された。 3. 分離ウイルスの諸性状 まず，発生症例1および発生症例2の分離ウイルスの物理化学的性状を検査した。メンブランフィルターによる沪過試験(50-100nm)，DNA合成阻害剤(IUDR，50μg/ml)の存在下での増殖試験，クロロホルムやエーテルによる不活化試験等の結果から，このウイルスはトガウイルス科のアルファウイルス属に属することが示唆された。各種血球での赤血球凝集性ではpH6.0-6.2の狭いpH域でガチョウ赤血球をよく凝集した(10^7.0 TCID_50/mlで凝集価128倍)。この結果から，ゲタウイルスの疑いが濃くなったので，その標準株とされるハルナ株との間で交差中和試験を行って，その免疫学的性状を比較した。明瞭な差は認められず，分離ウイルスはゲタウイルスと同定された。 次いで，マウスと子豚に対する病原性を検討した。マウスではとくに日齢と発病との関係を調べた。微量(10TCID_50)の脳内接種で，100%発病するのは3日齢までで，以後発病率は次第に低下し，11日齢接種で50%，13日齢接種では10%，15日齢を過ぎると全く発病しなかった。妊娠マウスに10^7.0 TCID_50のウイルスを腹腔内接種して胎子の感染状況を調べた。胎齢10日までは高率に胎内感染死が起こるようで，産子数が激減した。胎齢10日以後は胎内感染死から胎内感染-生後発病死へと移行し，胎齢16日接種では生後発病死が64%に達し，以後発病死は漸減した(17日齢時接種37%，18日齢接種7.4%，20日齢時接種7.1%)。感染時の胎齢が発病の重要な条件であることを示した。 豚では5日齢と18日齢の無菌豚に10^5.5/ml感染価のウイルスを筋肉内接種して発病の有無を調べた。18日齢を含めすべて元気喪失，全身のふるえ，皮膚の紅潮，後肢の運動失調の症状を示し，接種後2-3日に死亡またはひん死状態となった。死亡豚の扁桃，肺，肝，脾，血液からは10^4.0感染価/g以上のウイルスが回収でき，野外の発生症例と同様の疾病を再現できた。しかし，5日齢で経口投与した3頭では，1頭が2日後に軽度の歩行異常を示したに過ぎなかった。 4. 豚のゲタウイルスに対する抗体調査 ゲタウイルスが神奈川県下の豚の間にどの程度感染しているか，およその動向を知るため，秦野，伊勢原および平塚の3市の養豚場の繁殖豚を対象に，1986年と1987年目2年にわたり，HIテストにより抗体調査を行った。全体の陽性率は1986年は48%，1987年は28.9%で，地区別では秦野35%，伊勢原56%，平塚71%と調査年度および地区別にかなり変動が認められた。また，全体としてゲタウイルスの伝播度は低下しているようで，抗体陰性のおとり豚を置いて陽転時期の推定を考えたが，1986年はおとり豚に陽転がみられず，1987年は9月に7.7%，11月に11.0%と陽性率は低かった。 総括 従来，豚のトガウイルス感染による発病例は知られていなかったが，この研究である条件では発病し，急性経過で死亡することが明らかになった。今回の発生症例は2例とも同腹初生豚に集中的に発生しており，また，マウスの実験で明らかなように，発病には感染時の日齢が重要な要因である。抗体陰性の初生豚が一定量のウイルス感染を受けることが発病の一つの条件と考えられるが，胎内感染-生後発病の可能性も否定できない。この点，抗体陰性の繁殖母豚が増加していることから，今後注意すべき疾病の一つと考えられる。 |
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| Abstract | ||||||
| 内容記述タイプ | Other | |||||
| 内容記述 | Getahvirus, a member of alphavirus of the family Togaviridae, has been isolated from mosquitoes in Japan, Malaysia and Austraria and from healthy pigs and sick horses. Serological survey indicated that the Virus was widely transmitted in swine, however, there have never, been reports describing the sickness in swine due to the virus. The author has been engaged for several years in diagnostic analysis of pig diseases occurring in Kanagawa prefecture and revealed for the first time that the natural cases of fatal infection in piglets were due to the virus, which was characterized by swollen face with light neuroparalysis. The purpose of this study is to reveal the pathogenicity of the virus in swine and discuss the factors producing fatal infection in piglets based on the epizootiological surveys as well as the experimental infection in mice and piglets of various age. 1. The incidence of pig diseases in Kanagawa prefecture An investigation was conducted for the past 5 years from 1983 to 1987 to obtain which pig diseases were most prevalent and affecting pig husboundry in the prefecture. In this period, a total of about 160,000 pigs were raised in Kanagawa prefecture, mostly in the central area for breeding, farrowing and fattening, though the population tended to be dicreasing in number gradually. The accumulated data of diagnostic investigation performed during the period indicated that chronic infectious diseases and complicated infections increased instead of acute infectious diseases and abortion as well as loss of weaned and unweaned piglets were prevalent. The most prevalent among them were Aujeszk's disease, pneumonia due to the infection with Hemophilus and Pasteurella, coli-bacteriosis, abortions due to the infection with Japanese encephalitis virus and swine parvovirus, infectious gastroenteritis and toxoplasmosis. Besides, it was noticeable that concentrated occurrence of a disease in two litters of newborn piglets, characterized by swollen face with a light neuroparalysis, was first confirmed to be due to the infection with Getah virus. 2. Etiological investigation of the fatal disease of newborn piglets of two litters In October 1985, at a subsidiary pigfarm in Fujisawa city, 12 newbornes of a litter suddenly showed decreased activity and tremors followed by posterior paresis. Eight of them died by the 3rd day after the onset and the remaining four recovered gradually(case#1). In October 1987 at a subsidiary pigfarm in Hatano city, 11 newborns of a litter were born including two stillborn fetuses. At 23 days of age, all 9 piglets had swollen faces, nervous signs such as tremor and unusual walking. Three of them were submitted for necropsy the next day when two were dead and the other one was moribund. Although the remaining 6 piglets showed sligt bilateral swelling of eyelids,they recovered gradually (case #2). Both sows of Case #1 and #2 as well as pigs chosen randomly from the neighboring pigfarms were examined thoroughly but all of them showed no clinical abnormalities at all. At necropsy, there were found no specific gross and histopathological lesions. However, there were observed gelatinous infiltration of hypodermis and light edema of lungs, liver, spleen, kidney and lymphonodi in all or dead and moribund piglets. Bacteriological examination of visceral organs (brain, lungs, liver, spleen, kidney and gut) did not indicate that no pathologic bacteria were involved in the disease, although Escherichia coli was isolated from the intestinal contents. Virus isolation was attempted from visceral organs. Ten percent suspensions of the organs were inoculated onto cultures of HmLu cells originated from the hamster lung. Cytopathic effects of round cell type were observed two days after inoculation in the cultures inoculated with all the tissue samples examined. The infectivity titers ranged from 10^3.0 to 10^6.25 TCID_50/ml in Case #1 and from 10^2.5 to 10^4.5 TCID_50/ml in Case #2, respectively. The viruses recovered from Case #1 and Case #2 had a similar characteristics of cytopathic effects and could not be differentiated each other by neutralization test between convalescent sera and each isolates. The results of antibody examination using isolate antigen indicated that the hemagglutination inhibiting antibody titers ranged from 1:320 to 1:480 in convalescent sera of 53 days of age in Case #1 and from 1:160 to 1:320 at 44 days of age in Case #2. The antibody was never detected in acute phase sera of both cases. These results indicate that the disease of piglets was due to the infection with the recovered virus. 3. Characteristics of the isolates First, the virus recovered from the samples of Case #1 and Case #2 were examined for physico-chemical properties. The result of filtration test (50-100nm), the growth test in the presence of IUDR(50ｦﾌg/ ml) and sensitivity to the organic solvents such as ethyl ether and chloroform indicated that the virus have the general properties of alphavirus of the family Togaviridae. The virus had hemagglutinating ability only with erythrocytes in the ristricted range of PH 6.0 to 6.2 (HA titer of 128 with the virus infectivity of 10^7.0 TCID_50/ml). From these results it was suspected that the virus might belong to Getahvirus. Therefore, the serological properties was examined using the Haruna strain, the reference strain of Getahvirus and its specific antiserum. By cross-neutralization test, the virus recovered could not be differentiated from the Haruna strain, indicating that the virus is identified as Getahvirus. Secondly, the virus isolates were examined for pathogenicily in mice and gnotobiotic piglets including the relationship between age and pathogenicity in mice. Mice were inoculated intracerebrally with approximately 10ｦﾌl of 10 TCID_50/0.1ml. When inoculated at one to three days of age, all the mice were killed. When inoculated at 11 days of age 50 % of mice and at 13 days of age 10 % of mice were killed. However, at 15 days or more, no mice were killed. Pregnant mice were also tested by intraperitoneal inculation with 10^7.0 TCID_50 of the virus in order to examine whether or not their fetuses were affected. When inoculated at anytime during the first 10 days of gestation, they hardly produced nomal newborns probably due to fatal infection of embryos. When inoculated after 10 days of gestation or therafter, they produced almost nomal number of newborn which died soon after birth through the intrauteric infection. Inoculation at 16 days of gestation resulted in 64 % death of newborns. When inoculated at 17, 18 and 20days of gestation, their newborns died soon after birth at 37 %, 7.4 %, and 7.1 %, respectively. These result indicated that the younger the fetal age is, the more serious infection. Five 5-day-old and one 18-day-old gnotobiotic piglets were intramuscularly inoculated with 10^5.5 PFU of the virus and three 5-day-old piglets were inoculated oronasally with the same dose of the virus. They were observed daily for clinical sign. All of piglets inoculated intramuscularly exhibited anorexia, depression, tremors of the whole body, red discoloration of the skin and incoodination of the pelvic limbs. Three piglets became moribund and died 2 to 3 days after inoculation. The virus was recovered from their tonsils, lungs, liver, and blood. The infectivity titers of the virus in organs and sera ranged from 10^2.0 to 10^5.6 PFU/ml. Furthermore, one of the three piglets inoculated showed some clinical signs 2 days after inocuration. Thus, the experimental infection of piglets with the recovered Getahvirus reproduced the same peracute fatal disease as observed in the natunal cases. 4. serological survey of Getahvirus infection in swine In 1986 and 1987, serum samples were collected mainly from sows of the breeding farms (133) in Hatano, Isehara and Hiratsuka district, in order to know the incidence of infection with Getahvirus in swine in Kanagawa prefecture. As a whole, the positive incidence were 48.0 % in 1986 and 28.0 % in 1987, respectively. The positive rates of pigfarms infected were 35.0 % in Hatano, 56.0 % in Isehara and 71.0 % in Hiratsuka district. The result indicate that the distribution of antibody varied depending on years and districts. In 1986, some pigs were set in each district as sentinel pigs and tested for antibody with all negative result. In Octorber and November 1987, however, these sentinel pigs were found infected with the virus at 7.7 % and 11.0 %, respectively. Discussion and conclusion In the present study, it was clearly revealed for the first time that Getahvirus produces a peracute fatal infection in piglets under some conditions. In both cases encountered in the field, the outbreak of the disease was concentrated only in each farrow and did not spread to their neighboring pigs. The result was the same in the experimental infection in mice, suggesting that the age of infection is one of the most important factors. Furthermore, as in the experimental infection of gnotobiotic piglets, it is considered that if newborns without maternal antibody are primarily exposed to a relatively concentrated virus, the infection would result in peracute fatal disease as seen in the natural cases. As seen in the serological survey, the recent incidence of infection in sow was relatively low and varied by years and district. These findings could provide some favorable conditions for producing the disease. Lastly, prenatal infection could still reuselt in neonatal disease and possible subsequent death. In conclusion, It was elcidated that the infection with Getahvirus produces a peracute fatal disease in piglets without maternal antibody and some factors for producing the disease were also discussed. |
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| 学位名 | ||||||
| 学位名 | 博士(獣医学) | |||||
| 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 | 1991-12-04 | |||||
| 学位授与番号 | ||||||
| 学位授与番号 | 乙第302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 | |||||
