Undersökning av förekomst av okända virus hos svenska fjällrävar med encefalit

Abstract: The artic fox is under threat of extermination in Europe. The population decreased strongly at the beginning of the twentieth century because of intensive hunting. The artic fox was placed under protection by law 1928 in Sweden but despite this the population has had difficultly to recover. This can depend on several reasons, but the main threats are shortage of food and competition from the red fox. Along with Norway and Finland, Sweden has carried out a project called SEFALO (Saving the Endangered Fennoscandian Alopex lagopus), whose objectives were to prevent continued decreased populationnumbers and through, for example supplementary feeding, help the population to recover. 10 years ago approximately only 40 adult artic foxes were present in Sweden. Last summer, when the SEFALO-project was completed, the number was calculated to about 140 adult individuals. In an attempt to increase the number of individuals a breeding programme with wild captured foxes started in 1992. Unfortunately, the majority of the foxes developed central nervous symptoms and either died or were euthanized. Many of these foxes had serious encephalitis, but researchers has not so far found the reason to the disease. One have looked for the most common infectious causes of encephalitis, but without positive results. The main aim with this study was to examine occurrence of unknown viruses in Swedish artic foxes with encephalitis, to if possible find a causative agent of this disease. The study included four artic foxes who had shown neurological symptoms. Brainmaterial was examined from three of the foxes and CSF from one of them. DNA and RNA were extracted from the clinical material and through the use of primers with random sequences, the nucleotidesequences were amplified with the aid of PCR. The sequences were then cloned in E.coli-cells before sequencing was carried out. The result of this study showed that the material that was used did not for certain contain any agents that could have caused the artic foxes' disease. There are different reasons why any virus couldn't be identified. The virus concentration is often very low, especially in very sick animals, and this makes the detection more difficult. Virus can also be present in the animal but not in the tissue sample that is examined or the virus can exist in an other organ. To some extent this work supports earlier findings of a herpesvirus as a possible causative agent. In order for the artic fox population to survive and to continue to increase in number, futher actions are required and also additional research about the causative agent behind the disease.