Mörner T, Sandström G, Mattsson R, Nilsson P O
Department of Wildlife Diseases, National Veterinary Institute, Uppsala, Sweden.
J Wildl Dis. 1988 Jul;24(3):422-33. doi: 10.7589/0090-3558-24.3.422.
The occurrence of tularemia was studied in 1,500 hares submitted to the National Veterinary Institute, Uppsala, Sweden for postmortem examination during 1973 through 1985. A total of 109 tularemia cases was recorded based on the fluorescent antibody (FA) test for Francisella tularensis and on the gross and microscopic pathology. Tularemia was diagnosed only in the varying hare (Lepus timidus) and not in the European brown hare (Lepus europaeus). The geographical distribution of the 109 cases indicates that tularemia has not spread in Sweden during the last 45 yr, with the exception of an endemic occurrence of the disease on the island of Stora Karlsö in the Baltic sea. The disease was most frequent in the autumn and only a few cases were recorded during winter. Cases were not seen in the spring. The annual prevalence varied, with several cases in 1974 and 1981, but there were no cases in 1976 and 1980. The postmortem findings in hares dying of tularemia in the autumn were characterized by focal coagulative necrosis in liver, spleen and bone marrow, with high numbers of bacteria FA-positive for F. tularensis. In hares dying during winter months, the most characteristic findings were hemorrhagic enteritis and typhlitis, although necrotic lesions could occur in liver, spleen and bone marrow. Diseased hares on the island of Stora Karlsö were demonstrated to be infected with ticks, while hares on the mainland of Sweden generally were fed upon by mosquitoes. Twenty-six of the 109 hares with tularemia were examined bacteriologically and F. tularensis biovar palaearctica was isolated from eight. The lung extract antibody test for F. tularensis was performed in 18 of the 109 hares. All were negative. In addition to the field study, an experimental study with F. tularensis biovar palaearctica was performed. Four varying hares and three European brown hares were inoculated. None of the hares died from tularemia, and generalized infection was not demonstrated.
1973年至1985年间，瑞典乌普萨拉国家兽医研究所对1500只野兔进行了死后检查，以研究兔热病的发生情况。基于对土拉弗朗西斯菌的荧光抗体（FA）检测以及大体和微观病理学检查，共记录了109例兔热病病例。兔热病仅在变色兔（Lepus timidus）中被诊断出，而在欧洲棕兔（Lepus europaeus）中未被诊断出。这109例病例的地理分布表明，在过去45年里，兔热病在瑞典并未传播，波罗的海中的大卡尔斯岛（Stora Karlsö）上该病呈地方流行是个例外。该病在秋季最为常见，冬季仅记录到少数病例。春季未见病例。年患病率各不相同，1974年和1981年有几例病例，但1976年和1980年没有病例。秋季死于兔热病的野兔的死后检查结果特征为肝脏、脾脏和骨髓出现局灶性凝固性坏死，有大量对土拉弗朗西斯菌FA呈阳性的细菌。在冬季死亡的野兔中，最典型的发现是出血性肠炎和盲肠炎，尽管肝脏、脾脏和骨髓也可能出现坏死性病变。大卡尔斯岛上患病的野兔被证明感染了蜱虫，而瑞典大陆的野兔通常被蚊子叮咬。109只患兔热病的野兔中有26只进行了细菌学检查，从8只野兔中分离出土拉弗朗西斯菌古北区生物变种（F. tularensis biovar palaearctica）。109只野兔中有18只进行了土拉弗朗西斯菌的肺提取物抗体检测。结果均为阴性。除了野外研究外，还进行了一项关于土拉弗朗西斯菌古北区生物变种的实验研究。给4只变色兔和3只欧洲棕兔接种了该菌。没有一只野兔死于兔热病，也未显示出全身性感染。
