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エジプトの乳牛における乳房炎の有病率と細菌病因、不顕性乳房炎と授乳期がSCCに及ぼす影響に関する研究
Study on prevalence and bacterial etiology of mastitis, and effects of subclinical mastitis and stage of lactation on SCC in dairy goats in Egypt.
PMID: 32577937 DOI: 10.1007/s11250-020-02331-5.
抄録
エジプトでは、カプリン乳房炎の有病率と疫学に関する情報が不十分である。本研究は、乳牛ヤギにおけるカプリン乳房炎の有病率と病因を調査し、不顕性乳房炎（SCM）のマーカーとしての体細胞数（SCC）の有効性を評価することを目的とした。本研究は、異なる授乳期にある249頭の無作為に選ばれた授乳中のヤギを対象に実施し、臨床検査を行った。これらの動物のうち、477頭のミルクサンプルを無菌的に採取し、細菌の付着をスクリーニングした。234の明らかに正常な乳試料でSCCを評価し、SCC≧10cells/mlをSCMの指標とした。臨床的乳房炎（CM）の有病率は、動物レベルで33.73％、乳房半身レベルで16.87％であった。また、一見健康なハーフでは、SCMは52.56%であった。培養の結果，単発感染は49.69％，混合感染は23.9％，陰性は26.41％であった．その内訳は，コアグラーゼ陰性ブドウ球菌（CNS）が58.75％と最も多く，次いで黄色ブドウ球菌（S. aureus）が24.375％，連鎖球菌（1.875％）が最も少なかった．細菌学的に陽性のサンプルと陰性のサンプルのSCCの平均値の間には有意な差は記録されず、授乳中期と後期の両方の段階でSCC≦10とSCC≧10cells/mlのものでも、SCCの平均値は記録されなかった。また、SCC≧10cells/mlで細菌学的に陰性の動物の割合は、中産期（9.3％）に比べて、晩産期（28.57％）の方が3倍も多くなっています。SCCはヤギの乳房内炎症（IMI）の適切な指標ではなく、細菌学的検査の方が効率的であり、時間と費用がかかることに変わりはないと考えられます。
In Egypt, inadequate information on prevalence and epidemiology of caprine mastitis is available. This study was designed to investigate prevalence and etiological agents of caprine mastitis and assess the efficacy of somatic cell count (SCC) as marker of subclinical mastitis (SCM) in dairy goats. This study was carried out on 249 randomly selected lactating goats in different lactation stages and examined clinically. Of these animals, 477 milk samples were aseptically collected and screened for bacterial carriage. SCC was assessed in 234 apparently normal milk samples, and SCC ≥ 10 cells/ml was indicator for SCM. Prevalence of clinical mastitis (CM) was 33.73% and 16.87% at animal and udder-half levels, respectively. SCM was 52.56% in the apparently healthy halves. Culture results proved single infection in 49.69% of samples, mixed infection in 23.9% of samples, and 26.41% of samples were negative. Coagulase negative staphylococci (CNS) were the most predominant bacteria (58.75%), then Staphylococcus aureus (S. aureus) (24.375%), and Streptococci (1.875%) were the least. No significant difference was recorded between mean of SCC in bacteriologically positive and negative samples, neither in those with SCC ≤ 10 nor with SCC ≥ 10 cells/ml both in middle and late lactation stages. Besides, the percentage of animals harboring SCC ≥ 10 cells/ml and negative for bacteriology in late lactation stage was 3 times (28.57%) more than in midlactation (9.3%). We can assume that SCC is not proper indicator for intra-mammary inflammation (IMI) in goats, and bacteriological examination remains more efficient, despites being time consuming and expensive.