2006), and by 2015, populations were established in counties throughout the state ( Eisen et al. By 2005, presence of the ticks was reported in Chicago ( Jobe et al. scapularis had been found in the northernmost regions of the state in the early 1990s. scapularis has long been endemic, the range of these ticks expanded, covering most of Minnesota and nearly all of Wisconsin ( Eisen et al. In Minnesota and Wisconsin, states in which I. scapularis was also expanding its range in the states that border Iowa to the north and east. scapularis across Iowa, and the increasing proportion of ticks infected with B. This manuscript provides a summary of these 24 yr, with an emphasis on the changing proportions of ticks submitted to the program, the continuing expansion of I. scapularis were tested for the presence of B. Over this time, >11,000 ticks were submitted from within Iowa, identified, and catalogued, and hundreds of nymphal and adult I. Despite these drawbacks, passive surveillance programs remain an important and cost-effective tool in vector-borne disease epidemiology.īetween 19, a statewide tick-borne disease passive surveillance program was maintained at Iowa State University, with the primary goals of monitoring tick distribution and the infection rate of susceptible ticks with Borrelia burgdorferi. Negative tradeoffs of passive surveillance programs include a positive correlation of tick submissions with population density, the potential for false negatives in areas with few people to submit samples, uncertainty about acquisition location and timing of some specimens, and the inability to predict the prevalence of human cases in advance ( Johnson et al. The result is that passive surveillance programs produce reliable data about whether vector tick species are present in an area, the proportion of ticks infected with a tick-borne pathogen (limited in geographic granularity in regions from which few ticks are submitted), and the progress of establishment as a nonendemic tick species spreads into a territory not colonized previously. Passive surveillance programs relying on self-reporting by tick-bite victims or their physicians are comparatively easily and cheaply maintained, producing datasets of far greater scope but substantially less precision than active surveillance programs. These programs, however, are expensive in resources and manpower, which typically results in surveillance efforts that are quite limited in scope and duration. 2016).Īctive surveillance programs emphasizing systematic collection and pathogen testing of vector ticks provide great precision in evaluating the spatial and temporal distribution of ticks and patterns of pathogen distribution. scapularis in the midwestern and northeastern United States, and the concomitant expansion of Lyme disease, emphasize the increasing importance of this disease to public health ( Lingren et al. Furthermore, the expanding distribution of I. Although very few fatalities result directly from Lyme disease infection, the number of people infected and morbidity inflicted underscores the public health importance of this illness. Of these, Lyme disease is by far the most significant, with about 30,000 cases reported to the CDC per year ( ) and an estimated 10 times as many cases diagnosed ( Hinckley et al. It transmits a variety of disease-causing organisms, including those responsible for Lyme disease, human granulocytic anaplasmosis, babesiosis, and Powassan virus. The blacklegged tick, Ixodes scapularis Say, is currently the most important vector of disease to humans in the continental United States. Tick, Rickettsia buchneri, Anaplasma phagocytophilum, Lyme disease The results of these surveillance programs indicate an increasing risk of disease transmission by I. phagocytophilum, and 67.3% for Rickettsia spp. (likely representing Rickettsia buchneri). burgdorferi, Anaplasma phagocytophilum, and spotted fever group Rickettsia spp. Ixodes scapularis nymphs collected at these sites were tested for the presence of B. Active surveillance was performed at selected sites from 2007–2009. burgdorferi, the highest proportion of any year. burgdorferi increased over time between 19. The proportion of vector ticks infected by B. scapularis per year over the surveillance period, indicating expansion of this tick species across the state. An average of 2.6 of Iowa’s 99 counties submitted first reports of I. Submitted ticks were identified to species and life stage, and Ixodes scapularis Say nymphs and adults were tested for the presence of Borrelia burgdorferi. A passive surveillance program monitored ticks submitted by the public in Iowa from 1990–2013.
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