Changes in the Ixodes ricinus microbiome associated with artificial tick feeding

Area of Science:

• Veterinary Entomology
• Microbiology
• Molecular Biology

Background:

• Artificial tick feeding systems (ATFS) are crucial for studying tick biology and pathogen interactions.
• Antibiotics are often used in ATFS to prevent blood decay during long feeding periods, potentially altering tick microbiomes.
• The tick microbiome, including mutualistic bacteria, plays a vital role in tick physiology and development.

Purpose of the Study:

• To investigate the impact of antibiotic supplementation (gentamicin) in ATFS on the microbiome composition and performance of *Ixodes ricinus* ticks.
• To compare tick performance and microbiome profiles between *in vitro* feeding and traditional calf-feeding methods.
• To assess the effects of different feeding conditions on key bacterial symbionts and tick fecundity.

Main Methods:

• Consecutive feeding of *Ixodes ricinus* larvae, nymphs, and adults using ATFS with and without gentamicin, alongside parallel feeding on calves.
• Analysis of tick microbiome composition using 16S rRNA gene sequencing.
• Quantification of specific bacterial symbionts (*Candidatus Midichloria mitochondrii*, *Rickettsia helvetica*, *Spiroplasma* spp.) via qPCR.

Main Results:

• Ticks fed on calves exhibited significantly better performance (larvae and nymphs) compared to *in vitro* groups.
• Adult ticks fed *in vitro* with gentamicin showed improved detachment proportion and weight compared to those without gentamicin.
• Calf-fed ticks displayed higher species richness, distinct microbiome composition, and significantly greater fecundity than *in vitro*-fed ticks.
• Gentamicin supplementation influenced the abundance of *Ca. Midichloria mitochondrii* and *Spiroplasma* spp. in *in vitro*-fed ticks.

Conclusions:

• The feeding method (ATFS vs. calves) and gentamicin supplementation significantly alter tick microbiome composition and fecundity.
• Observed changes in microbiome and performance metrics due to ATFS conditions may impact tick biology and vector competence.
• Researchers using ATFS must consider these effects to ensure accurate interpretation of tick biology and pathogen transmission studies.