Parasites of vectors - Ixodiphagus hookeri and its Wolbachia symbionts in ticks in the Netherlands

Abstract

BackgroundIxodiphagus hookeri is a parasitic wasp of ixodid ticks around the world. It has been studied as a potential bio-control agent for several tick species. We suspected that the presence of Wolbachia infected I. hookeri eggs in ticks is responsible for incidental detection of Wolbachia DNA in tick samples.MethodsThe 28S rRNA and 16S rRNA genes of a specimen of I. hookeri was amplified and sequenced. PCR on part of the 28S rRNA gene was used to detect parasitic wasp DNA in 349 questing Ixodes ricinus ticks from various sampling sites. Furthermore, the wsp gene of Wolbachia was sequenced from the I. hookeri specimen and a subset of ticks was tested using this marker.ResultsSeveral sequences from tick specimens were identical to the Wolbachia sequence of the I. hookeri specimen. Ixodiphagus hookeri was detected in 9.5% of all tested ticks, varying between 4% and 26% depending on geographic location. Ten out of eleven sampling sites throughout the Netherlands were positive for I. hookeri. Eighty-seven percent of I. hookeri-positive but only 1.6% of I. hookeri-negative ticks were Wolbachia positive. Detection of I. hookeri DNA was strongly associated with the detection of Wolbachia in ticks.ConclusionThis is the first reported case of I. hookeri in the Netherlands. Furthermore I. hookeri harbours Wolbachia species and is broadly distributed in the Netherlands. While detection of Wolbachia DNA in ticks might often be due to parasitism with this wasp, other sources of Wolbachia DNA in ticks might exist as well.

Evidence for Personal Protective Measures to Reduce Human Contact With Blacklegged Ticks and for Environmentally Based Control Methods to Suppress Host-Seeking Blacklegged Ticks and Reduce Infection with Lyme Disease Spirochetes in Tick Vectors and Rodent Reservoirs

“…Stafford et al (2003) reported that the prevalence of I. hookeri in host-seeking I. scapularis nymphs decreased from 25–30% to <1% as tick abundance decreased following deer removal. Recent studies from Europe indicate that these parasitoid wasps commonly are infected with Wolbachia and transfer these endosymbiotic bacteria to I. ricinus ticks (Tijsse-Klasen et al 2011, Plantard et al 2012). …”

Occurrence of Ixodiphagus hookeri (Hymenoptera: Encyrtidae) in Ixodes ricinus (Acari: Ixodidae) in Southern Italy

“…For example, I. hookeri (Hymenoptera: Encyrtidae) is a wellknown parasitoid of ticks (Wood, 1911;Logan et al, 1985;Mwangi et al, 1994;Tijsse-Klasen et al, 2011). These wasps reproduce sexually, the female mating with the male immediately after emergence from the tick host (Hu et al, 1998).…”

First evidence of Ixodiphagus hookeri (Hymenoptera: Encyrtidae) parasitization in Finnish castor bean ticks (Ixodes ricinus)

“…Overall, highly varying rates of I. hookeri parasitization in host-seeking I. ricinus nymphs have been reported from Europe (22% in France, 7.2% in Italy, 2-4% in Germany, 9.6% in the Netherlands) (Collatz et al 2011;Tijsse-Klasen et al 2011;Plantard et al 2012;Ramos et al 2015). Whereas the rates of parasitization observed here were low (even considering minimum infection rates usually provide underestimates), higher rates in, for example, France and the Netherlands suggest that Ixodiphagus may have tangible impact on tick populations.…”

“…Ixodiphagus hookeri is an encyrtid wasp that specializes in parasitizing a wide range of hard tick species across the globe Knipling and Steelman 2000;Takasu and Nakamura 2008;Plantard et al 2012;Ramos et al 2015). In Europe, they parasitize both larvae and nymphs of I. ricinus, with nymphs appearing to be the preferred targets (Takasu and Nakamura 2008;Collatz et al 2011;Tijsse-Klasen et al 2011;Plantard et al 2012;Ramos et al 2015). Following oviposition, wasp eggs hatch into larvae that begin feeding on the tick only after it has finished its blood meal in the nymph stage, leading to the death of the tick prior to its development to an adult .…”

“…Due to their specificity and lethality, Ixodiphagus have long been a target of interest regarding the biological control of ticks (Larrousse et al 1928;Mwangi et al 1994;Knipling and Steelman 2000). However, few studies have been conducted regarding the biology, distribution, phenology, and/or parasitization rates of I. hookeri in Europe (Collatz et al 2011;Tijsse-Klasen et al 2011;Plantard et al 2012;Ramos et al 2015). From Fennoscandia, no such studies have been published.…”