VECTOR-BORNE DISEASES, SURVEILLANCE, PREVENTION Prevalence of Borrelia burgdorferi and Anaplasma phagocytophilum in Ixodes scapularis (Acari: Ixodidae) Nymphs Collected in Managed Red Pine Forests in Wisconsin

Changes in the structureofmanagedredpine forests inWisconsincausedby interacting rootand stem-colonizing insects are associated with increased abundance of the blacklegged tick, Ixodes scapularis Say, in comparisonwith nonimpacted stands.However, the frequency and variability of the occurrence of tick-borne pathogens in this coniferous forest type acrossWisconsin is unknown. Red pine forests were surveyed from 2009 to 2013 to determine the prevalence ofBorrelia burgdorferi and Anaplasma phagocytophilum in questing I. scapularis nymphs. Polymerase chain reaction analysis revealed geographical differences in the nymphal infection prevalence (NIP) of these pathogens in red pine forests. In the Kettle Moraine State Forest (KMSF) in southeastern Wisconsin, NIP of B. burgdorferi across all years was 35% (range of 14.5Ð53.0%). At the Black River State Forest (BRSF) inwesternWisconsin,NIPofB.burgdorferiacross all yearswas 26%(rangeof 10.9Ð35.5%).Differences in NIP of B. burgdorferi between KMSF and BRSF were statistically signiÞcant for 2010 and 2011 and for all years combined (P 0.05). NIP of A. phagocytophilum (human agent) averaged 9% (range of 4.6Ð15.8%) at KMSF and 3% (range of 0Ð6.4%) at BRSF, and was signiÞcantly different between the sites for all years combined (P 0.05). Differences in coinfection of B. burgdorferi and A. phagocytophilum were not statistically signiÞcant between KMSF and BRSF, with an average of 3.4% (range of 1.7Ð10.5%) and 2.5% (range of 0Ð5.5%), respectively. In 2013, the density of infected nymphs in KMSFandBRSFwas14and30per 1000m, respectively, among thehighest ever recorded for the state. Differences in thedensity of nymphs andNIPamong siteswereneither correlatedwith environmental factors nor time since tick colonization. These results document signiÞcant unexplained variation in tick-borne pathogens between coniferous forests in Wisconsin that warrants further study.