臺灣地區弓形蟲感染症之流行病學研究

Abstract

弓形蟲 (Toxoplasma gondii) 是一種胞內寄生原蟲，為人畜共通傳染病病原體。弓形蟲感染症於2007年納入第四類法定傳染病，但其在台灣一般人群的流行病學仍不明。過去文獻侷限於特殊族群血清學調查及零星病例報告，缺乏全國性弓形蟲感染盛行率及感染途徑調查。本研究與全台灣6區的捐血中心合作，蒐集1,783位捐血人之血液、血清檢體進行弓形蟲即時聚合酶鏈鎖反應與酵素免疫分析法篩檢，同時蒐集捐血人暴露因子及人口學資訊，分析與感染弓形蟲相關性。研究結果發現弓形蟲感染普遍存在於全台各地，整體血清抗體陽性率9.3% (其中5人為anti-Toxoplasma IgM陽性，但輔以親和力試驗確認仍為非急性期感染)，東部顯著較高 (18.8%)。多變項邏輯斯迴歸分析顯示居住東部、低教育程度、生食豬肉、生食貝類、家中豢養貓等為台灣地區民眾感染弓形蟲可能相關因子。進一步以病例對照研究加以探究，以法定傳染病通報系統的急性感染個案做為病例組 (n=30)，以1:8比例依年齡、性別、地區自血清陰性捐血人隨機樣本中，配對選取對照組 (n=224)，以檢驗可能的危險因子。 30位急性感染病人中，臨床病徵多以類流感症狀併淋巴結腫大或硬塊表現，其次為中樞神經系統症狀，眼部病徵，流產，及先天性感染。多變項邏輯斯迴歸分析發現：生食文蛤 (adjusted OR=3.7 , 95%CI: 1.4–9.9)、家中豢養貓 (adjusted OR=2.9, 95%CI: 1.1–7.9) 為台灣地區急性弓形蟲疾病的獨立危險因子。本研究為台灣首次全國性大規模弓形蟲流行病學調查，提供感染盛行率、感染途徑及發病危險因子實證資料，可做為未來制定弓形蟲防治政策的參考。

Toxoplasma gondii, an intracellular protozoan pathogen, causes human and animal diseases worldwide. Although toxoplasmosis became a notifiable communicable disease in Taiwan in 2007, little is known about its epidemiology among the general population. Through collaborating with the Taiwan Blood Services Foundation, a total of 1,783 healthy blood donors from all six-branch blood service centers participated in our study. Of the 1,783 participants, 166 (9.3%) tested positive for anti-Toxoplasma IgG, while 5 (0.28%) tested positive for anti-Toxoplasma IgM. The five IgM positive donors had high avidity antibodies suggestive of past infection. No active parasitemia was detected by real-time PCR assays. Multivariate logistic regression showed that undercooked pork meat consumption, raw mussels consumption, having a cat in the household, a lower education level, and donation place in eastern Taiwan were associated with Toxoplasma seropositivity. We further conducted a nationwide population-based case-control study aimed to investigate the risk factors for acute Toxoplasma gondii disease in Taiwan. Cases of acute human toxoplasmosis notified to Taiwan Centers for Diseases Control were compared with controls randomly selected from healthy T. gondii-seronegative blood donors. Cases and controls were matched on age, gender and residency, at a ratio of 1:8. A total of 30 laboratory-confirmed cases of acute toxoplasmosis and 224 controls were enrolled. The most common clinical manifestation of toxoplasmosis cases was flu-like symptoms (n=20), followed by central nervous system disease (n=4), ocular diseases (n=3), abortion (n=2), and congenital infection (n=1). Multivariate conditional logistic regression showed that consumption of raw clam (adjusted odds ratio [OR] = 3.7; 95%CI: 1.4–9.9) and having a cat in the household (adjusted OR = 2.9; 95%CI: 1.1–7.9) were the two independent risk factors for acute toxoplasmosis. These findings can guide future research and control policy.