▁poly gy rus ▁is ▁found ▁almost ▁u bi quit ously ▁within ▁populations ▁of ▁wild ▁wood ▁m ice ▁( Ap ode mus ▁s yl v atic us ). ▁In ▁one ▁study ▁of ▁wood ▁mouse ▁populations ▁in ▁Oxford shire , ▁England , ▁ 7 0 % ▁of ▁all ▁m ice ▁sample d ▁carried ▁an ▁in fection ▁with ▁H . ▁poly gy rus , ▁with ▁an ▁average ▁in fection ▁bur den ▁of ▁about ▁ 1 2 ▁w orm s ▁per ▁mouse . ▁Natural ▁in fection ▁intensity ▁displays ▁high ▁vari ability ▁in ▁wood ▁m ice , ▁r anging ▁from ▁none ▁to ▁ 2 4 4 ▁adult ▁w orm s ▁per ▁mouse . ▁Male ▁and ▁female ▁m ice ▁show ▁equal ▁par as it ic ▁bur dens . ▁Par as ite ▁occurrence ▁appears ▁to ▁posit ively ▁correlate ▁with ▁weight ▁and ▁age ▁of ▁the ▁mouse , ▁showing ▁an ▁increase ▁in ▁pre val ence ▁in ▁older , ▁heav ier ▁m ice . ▁In fection ▁was ▁also ▁season ally ▁reg ulated ▁in ▁the ▁wood ▁mouse ▁population , ▁with ▁highest ▁pre val ence ▁of ▁in fection / w orm ▁bur den ▁intensity ▁occurr ing ▁in ▁early ▁spring ▁and ▁reaching ▁their ▁lowest ▁values ▁in ▁late ▁summer / ear ly ▁aut umn . ▁This ▁is ▁in vers ely ▁correl ated ▁with ▁typical ▁bre eding ▁behav iors ▁of ▁the ▁wood ▁mouse , ▁where ▁the ▁population ▁pe aks ▁in ▁late ▁summer ▁or ▁early ▁aut umn , ▁and ▁is ▁at ▁its ▁lowest ▁in ▁the ▁early ▁spring . ▁The ▁bulk ▁of ▁research ▁on ▁H . ▁poly gy rus ▁has