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細菌性肺炎に罹患した馬の病態を把握するために血清中の血清アミロイドA(SAA)および肺サーファクタント.プロテインD(SP-D)を測定した.供試馬として,正常値を明らかにするために185頭の臨床的に健康なサラブレッドを,またStreptococcus equi subsp. zooepidemicus(S. zooepidemicus)を用いた感染実験のために9頭のサラブレッドをそれぞれ使用した.健康馬におけるSAAの平均値は0.1μg/ml,SP,Dは平均0.2ng/mlと極めて低位であった.一方,S. zoepidemicusを実験的に感染させた馬では,菌接種後24時間の時点で発熱および肺炎症状が観察され,併せてSAAおよびSP-Dも有意に上昇した.その後抗菌薬による加療を実施したが,発熱および臨床症状が認められる期間は,SAAおよびSP.Dは有意に上昇していた.しかし,SAA,SP-Dともに臨床症状の消失後はずみやかに正常値に復した.特に,SP-DはSAAの変動に先行して正常値に復した.このような現象は,既報からSP-Dが肺胞損傷に伴って肺胞中から血液中へ漏出していることに起因すると推察された・以上のことから,SAAおよびSP-Dは馬の細菌性肺炎の病態把握に有用であることが明らかとなった.
In the present study, the concentrations of serum amyloid A and surfactant protein D in sera were measured to evaluate them for identification of the clinical condition of horses with bacterial pneumonia. The study utilized 185 clinically healthy control thoroughbreds and 9 thoroughbreds for experimental infectious study with S. zooepidemicus. Blood samples were collected from the 185 healthy control thoroughbreds. The 9 thoroughbreds were experimentally infected S. zooepidemicus using an endoscopic injection to a lung lobe and were then observed of clinical conditions. Blood samples were collected before inoculation and on the 1-15th, 22nd, and 29th days after inoculation(follow-up group). The levels of SAA and SP-D in the healthy control thoroughbreds were very low. In the follow-up group, the levels of SAA and SP-D changed in parallel with the horses' clinical condition. The pyrexia observed after bacterial inoculation faded by the 11th day, and the changes in SAA and SP-D occurred simultaneous to disappearance of the clinical signs. Measurement of SAA and SP-D proved useful for monitoring the clinical condition of the horses with bacterial pneumonia. Changes in the SP-D value were preceded by changes in the SAA value. Since the changes in SP-D occurred approximately simultaneous to the changes in the horses' clinical signs, we believe that they reflect the condition of the alveolar membranes. We conclude that measurement of SAA and SP-D in sera is useful for identification of the clinical condition of horses with bacterial pneumonia.
