Virus meningo-encephalitis in Slovenia. 4. Isolation of the virus from the ticks Ixodes ricinus.

This article describes the steps taken to verify that the tick Ixodes ricinus is the main vector of Slovenian meningo-encephalitis.In 1954, several unsuccessful attempts were made to isolate the virus from unengorged ticks collected at random, but in the following year this system was abandoned, and instead the search for specimens was carried out on the basis of evidence supplied by meningo-encephalitis patients with a tick-bite case history.In June-the peak endemic period-140 unengorged ticks were collected from a part of a forest in central Slovenia where one of these patients had been working. The ticks were washed in alcohol, finely ground, and centrifuged, and the supernatant was inoculated intracerebrally into suckling mice, and intraperitoneally into adult mice and guinea-pigs. The infected suckling mice died between the fourteenth and eighteenth day after inoculation; a suspension of their brains was inoculated intracerebrally into a further batch of suckling and adult mice, which subsequently fell ill, showing signs in the central nervous system.The virus strain obtained was subjected to neutralization and complement-fixation tests, in order to identify the infective agent.