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Small rodents serve as reservoir hosts for tick-borne pathogens, such as spirochetes causing Lyme disease. Whether natural co-infections with other macroparasites alter the success of tick feeding, anti-tick immunity and the host's reservoir competence for tick-borne pathogens remains to be determined. In a parasitological survey of wild mice in Berlin approximately 40% of Ixodes ricinus infested animals harboured the nematode Heligmosomoides spp. simultaneously. We, therefore, aimed to analyse the immunological impact of the nematode/tick co-infection as well as its effect on the tick-borne pathogen Borrelia afzelii. Hosts experimentally co-infected with H. polygyrus and larval/nymphal I. ricinus ticks developed substantially stronger systemic Th2 responses, based on GATA-3 and IL-13 expression, than did single-infected mice. During repeated larval infestations, however, anti-tick Th2 reactivity and an observed partial immunity to tick feeding was unaffected by concurrent nematode infections. Importantly, the strong systemic Th2 immune response in co-infected mice did not affect the susceptibility to tick-borne B. afzelii. An observed trend for decreased local and systemic Th1 reactivity against B. afzelii in co-infected mice did not result in higher spirochete burden, neither facilitated bacterial dissemination nor induced signs of immunopathology. Hence, this study indicates that strong systemic Th2 responses in nematode/tick co-infected house mice do not affect the success of tick feeding and the control of the causative agent of Lyme disease.