Mapping the interaction network for pathogen-tick-host interactions in Virginia
In recent decades, tick-borne diseases have increased in range and prevalence across the eastern US, significantly impacting human health. Disease prevalence is influenced by pathogen-vector specificity and tick-host specificity. Variation in climate and habitat shapes the distribution and abundance of tick and host communities. This variation might cause regional differences in the pathogen-tick-host interaction network, and mapping this network will enable a better understanding and prediction of tick-borne disease prevalence. We mapped the interaction network for twelve counties and two city districts in northern Virginia through identification and disease testing of ticks collected from the environment and from mammalian and avian hosts. From October 2011 to October 2012, we collected 3,283 questing ticks from the environment and 2,616 ticks from 47 vertebrate species (19 wild birds, 21 wild mammals, 6 domestic mammals, and humans). Collected tick species in order of abundance were Amblyomma americanum, Ixodes scapularis, Dermacentor variabilis, Haemaphysalis leporispalustris, I. minor, I. cookei, I. brunneus, I. texanus, and A. longirostre.727 ticks were PCR tested for 10 pathogen groups.
Three tick species had generalist host specificity: I. scapularis (39 host species), D. variabilis (18 host species), and A. americanum (17 host species). I. cookei, I. brunneus, and I. minor were limited to 5-10 host species. H. leporispalustris was highly specific to Sylvilagus floridanus and comprised more than half of this host’s total tick burden. We identified 9 pathogen groups: Borrelia burgdorferi (7.8%), Rickettsia sp. (7.0%), Anaplasma phagocytophilum (5.1%), Hepatozoon sp. (2.9%), Theileria cervi (1.7%), Coxiella burnetii (1.4%), Ehrlichia sp. (1.1%), Bartonella sp. (0.3%), and Eimeriidae sp. (0.1%). Babesia microti was not detected in any of the tested ticks. A. americanum showed a high prevalence of Rickettsia infection (31.4%). B. burgdorferi was detected in I. scapularis (21.0%), I. minor (2.8%), and A. americanum (2.0%). Multiple pathogens were found in 6.2% of ticks. Pathogen-tick-host interaction networks are very complex and subject to change as new species enter the community. The prevalence and diversity of tick-borne diseases are likely to increase with these factors.