Inter-annual variation in prevalence of Borrelia burgdorferi sensu stricto and Anaplasma phagocytophilum in host-seeking Ixodes scapularis (Acari: Ixodidae) at long-term surveillance sites in the upper midwestern United States: Implications for public health practice.

The geographic range of the blacklegged tick, Ixodes scapularis, and its associated human pathogens have expanded substantially over the past 20 years putting an increasing number of persons at risk for tick-borne diseases, particularly in the upper midwestern and northeastern United States. Prevention and diagnosis of tick-borne diseases rely on an accurate understanding by the public and health care providers of when and where persons may be exposed to infected ticks. While tracking changes in the distribution of ticks and tick-borne pathogens provides fundamental information on risk for tick-borne diseases, metrics that incorporate prevalence of infection in ticks better characterize acarological risk. However, assessments of infection prevalence are more labor intensive and costly than simple measurements of tick or pathogen presence. Our objective was to examine whether data derived from repeated sampling at longitudinal sites substantially influences public health recommendations for Lyme disease and anaplasmosis prevention, or if more constrained sampling is sufficient. Here, we summarize inter-annual variability in prevalence of the agents of Lyme disease (Borrelia burgdorferi s.s.) and anaplasmosis (Anaplasma phagocytophilum) in host-seeking I. scapularis nymphs and adults at 28 longitudinal sampling sites in the Upper Midwestern US (Michigan, Minnesota, and Wisconsin). Infection prevalence was highly variable among sites and among years within sites. We conclude that monitoring infection prevalence in ticks aids in describing coarse acarological risk trends, but setting a fixed prevalence threshold for prevention or diagnostic decisions is not feasible given the observed variability and lack of temporal trends. Reducing repeated sampling of the same sites had minimal impact on regional (Upper Midwest) estimates of average infection prevalence; this information should be useful in allocating scarce public health resources for tick and tick-borne pathogen surveillance, prevention, and control activities.

Characterization of a novel pathogenic variant in the FECH gene associated with erythropoietic protoporphyria.

Erythropoietic protoporphyria (EPP) is an autosomal recessive deficiency in heme biosynthesis due to pathogenic variants in the ferrochelatase gene (FECH). Patients present with lifelong photosensitivity and potential liver disease. Here we report a novel FECH variant designated c.904_912+1del found in trans with the c.315-48T>C hypomorphic variant, in one family with three affected individuals. These patients presented with immediate painful cutaneous photosensitivity but no hepatic manifestations. All have elevated protoporphyrin levels consistent with a diagnosis of EPP. Genetic, biochemical, and functional assay results obtained for this family suggest that the unique variant c.904_912+1del is likely pathogenic and thus causative of EPP.

Uncoordinated phylogeography of Borrelia burgdorferi and its tick vector, Ixodes scapularis.

Vector-borne microbes necessarily co-occur with their hosts and vectors, but the degree to which they share common evolutionary or biogeographic histories remains unexplored. We examine the congruity of the evolutionary and biogeographic histories of the bacterium and vector of the Lyme disease system, the most prevalent vector-borne disease in North America. In the eastern and midwestern US, Ixodes scapularis ticks are the primary vectors of Borrelia burgdorferi, the bacterium that causes Lyme disease. Our phylogeographic and demographic analyses of the 16S mitochondrial rDNA suggest that northern I. scapularis populations originated from very few migrants from the southeastern US that expanded rapidly in the Northeast and subsequently in the Midwest after the recession of the Pleistocene ice sheets. Despite this historical gene flow, current tick migration is restricted even between proximal sites within regions. In contrast, B. burgdorferi suffers no barriers to gene flow within the northeastern and midwestern regions but shows clear interregional migration barriers. Despite the intimate association of B. burgdorferi and I. scapularis, the population structure, evolutionary history, and historical biogeography of the pathogen are all contrary to its arthropod vector. In the case of Lyme disease, movements of infected vertebrate hosts may play a larger role in the contemporary expansion and homogenization of the pathogen than the movement of tick vectors whose populations continue to bear the historical signature of climate-induced range shifts.

Anaplasma phagocytophilum, Babesia microti, and Borrelia burgdorferi in Ixodes scapularis, southern coastal Maine.

Ixodes scapularis (deer ticks) from Maine were tested for multiple infections by polymerase chain reaction and immunofluorescence. In 1995, 29.5%, 9.5%, and 1.9% of deer ticks were infected with Borrelia burgdorferi, Anaplasma phagocytophilum, and Babesia microti, respectively. In 1996 and 1997, the number of A. phagocytophilum-infected ticks markedly declined. In 1995 through 1996, 4 (1.3%) of 301 were co-infected.