Biology session

Lyme borreliosis is the most common tick-borne disease on the Northern hemisphere. The causative agents, namely certain members of the group Borrelia burgdorferi sensu lato can be maintained in nature by several vertebrate hosts. The aim of our study was to find out if the infection is present in the hedgehogs and in the different species of ticks collected from the hedgehogs and the vegetation on the Margaret Island. We also tryed to assess the human health significance of the local pathogen cycle.

We collected hedgehogs from 2009 to 2010 once a month, except the winter months. The animals were measured, the ticks and fleas were removed and in 2010 and 2011 tissue samples were taken from the ears of the hedgehogs. Questing ticks were collected by flagging. Later the ticks and fleas were identified, the DNA was extracted from the ticks by alcaline hydrolysis and from the tissue samples with a commercial DNA-extraction kit, and the Borrelia infection was investigated with the help of polymerase chain reaction and gel electrophoresis. Some of the positive samples were sequenced to identify the detected Borrelia species.

In the three-year study, we collected 9371 ticks and 1380 fleas from 386 hedgehogs. Among the ticks there were 5744 Ixodes ricinus, 480 Ixodes larve 144 Ixodes hexagonus, one Ixodes acuminatus, one Hyalomma marginatum and one Haemaphysalis punctata. Prevalence of the hedgehogs’ tick infestation was 78.13% and the median intensity was 19. Most (1374) of the identified fleas were Archaeopsylla erinacei and only six were Ctenocephalides canis. Prevalence of the hedgehogs’ flea infestation was 53,65%, the median intensity was 4. We collected 1467 I. ricinus from the vegetation. In the ticks collected from hedgehogs the minimum prevalence was 10.85% for B. burgdorferi s. l. The minimum prevalence in questing ticks was 12.95%. The bacteria detected in questing ticks and tissue samples were Borrelia afzelii, in tissue samples there were B. afzelii and Borrelia spielmanii and in the ticks collected from hedgehogs we found B. afzelii and Borrelia garinii. 94% of the hedgehog samples were positive for Borrelia, which is a very high prevalence compared to data from other countries.

Margaret Island is a popular city park in Budapest with several thousands of visitors every week. We have shown that hedgehogs can infect nymphs and larvae feeding on them and in their next stage after moulting, ticks might infect people and cause disease. According to our questionnaire, few people get infected on the Margaret Island despite the relatively high proportion of infected ticks, because the ticks occur mainly in the bushes, where people do not or rarely go.