Nehili M, Ilk C, Mehlhorn H, Ruhnau K, Dick W, Njayou M
Department of Zoology and Parasitology, Ruhr-University Bochum, Germany.
Parasitol Res. 1994;80(4):277-90. doi: 10.1007/BF02351867.
The presence and survival of pathogens inside the gut of leeches were studied by means of light and electron microscopy. In African leeches from Cameroon, blood was serologically positive for human immunodeficiency virus (HIV) and hepatitis B; blood of Hirudo medicinalis bought in German pharmacies contained up to 11 different species of bacteria. In experiments done at low (3 degrees C) and high (22 degrees, 32 degrees C) temperatures, it was shown that ingested red and white blood cells survive for long periods. The time was prolonged to at least 6 months in cases in which the leeches were stored at 3 degrees C. The same effect occurred with pathogens. Bacteriophages (viruses of bacteria) and bacteria persisted in large numbers for at least 6 months in the gut of experimentally infected leeches. Protozoan parasites such as Toxoplasma gondii, Trypanosoma brucei brucei, or Plasmodium berghei were even capable of reproducing inside the gut of the leech. In the case of Plasmodium parasites, this proceeded at low (3 degrees C) and high (22 degrees C) temperatures until all erythrocytes were used up. These parasites survived as long as the erythrocytes and lymphocytes were of good shape, i.e., around 5-6 weeks p.i. Single stages survived longer, especially at low temperatures. However, electron microscopy studies gave no hint of penetration of such pathogens into the unicellular salivary glands, which would initiate a direct transmission. Such transmission, however, is possible--many fish leeches directly transmit several blood parasites--when the leeches are squeezed during skin attachment or when they are manipulated by dropping salt solution on their backs while they are sucking. Consequently, the leech is a potential vector of many pathogens, especially in regions with an endemic spread of human and/or animal pathogens.
通过光学显微镜和电子显微镜对水蛭肠道内病原体的存在及存活情况进行了研究。在来自喀麦隆的非洲水蛭中，血液经血清学检测显示对人类免疫缺陷病毒（HIV）和乙型肝炎呈阳性；在德国药店购买的医用水蛭的血液中含有多达11种不同的细菌。在低温（3℃）和高温（22℃、32℃）条件下进行的实验表明，摄入的红细胞和白细胞能长时间存活。当水蛭在3℃下储存时，存活时间延长至至少6个月。病原体也有同样的情况。噬菌体（细菌病毒）和细菌在实验感染的水蛭肠道内大量持续存在至少6个月。原生动物寄生虫，如弓形虫、布氏布氏锥虫或伯氏疟原虫，甚至能够在水蛭肠道内繁殖。就疟原虫寄生虫而言，在低温（3℃）和高温（22℃）下都会繁殖，直到所有红细胞被消耗殆尽。只要红细胞和淋巴细胞形态良好，这些寄生虫就能存活，即感染后约5 - 6周。单个阶段存活时间更长，尤其是在低温下。然而，电子显微镜研究没有发现此类病原体穿透单细胞唾液腺的迹象，而这将引发直接传播。不过，当水蛭在附着于皮肤时被挤压，或者在吸血时在其背部滴加盐溶液进行操作时，许多鱼蛭会直接传播几种血液寄生虫，这种直接传播是可能的。因此，水蛭是许多病原体的潜在传播媒介，尤其是在人类和/或动物病原体地方性传播的地区。
