In search for tick-borne encephalitis virus and Rickettsia in Belgian Ixodes ricinus ticks: Evidence of rickettsia felis.

This study investigated the presence of tick-borne encephalitis virus (TBEV) in ticks collected in Belgium between 2018 and 2024, as well as the occurrence of Rickettsia spp. in ticks sampled in 2024. A total of 3739 ticks from 17 locations, of which 16 in Flanders and 1 in Wallonia, were collected from vegetation and tested in 510 pools for TBEV by RT-PCR. Sampling locations were selected based on potential exposure risk, including proximity to human TBE cases, evidence of TBEV antibodies in animals, or near the border between Belgium and the Netherlands. No TBEV RNA was detected in this collection. The 2432 ticks collected in 2024, were tested in 324 pools for Rickettsia spp. by PCR. Spotted Fever Group (SFG) rickettsiae were found in half of the pools, corresponding to an estimated prevalence of 10 %. Rickettsia helvetica was the predominant species, with an estimated prevalence of 8 %, while two pools (1.26 %) tested positive for R. felis. These results contribute to the understanding of tick-borne disease epidemiology in Belgium. Continuous monitoring is recommended to evaluate the impact of environmental changes on Belgian tick populations and pathogen circulation.