Passive Tick Surveillance, Dog Seropositivity, and Incidence of Human Lyme Disease

Abstract

Data on nymphal Ixodes scapularis ticks submitted by the public to the University of Rhode Island Tick Research Laboratory for testing from 1991 to 2000 were compared with human case data from the Rhode Island Department of Health to determine the efficacy of passive tick surveillance at assessing human risk of Lyme disease. Numbers of ticks submitted were highly correlated with human cases by county (r = 0.998, n = 5 counties) and by town (r = 0.916, n = 37 towns), as were the numbers of positive ticks submitted (r = 0.989 by county, r = 0.787 by town). Human cases were correlated with ticks submitted by town each year, and with positive ticks in all but 2 years. Thus, passive tick surveillance effectively assessed geographical risk of human Lyme disease. In contrast, tick submissions through time were not correlated with human cases from year to year. Dog seropositivity was significantly correlated with human cases by county in both years tested, but by town in only one of two years. Numbers of ticks submitted were correlated with dog seropositivity by county but not by town, apparently because of high variability among towns with small sample sizes. Our results suggest that passive tick surveillance, using ticks submitted by the public for Lyme spirochete testing, can be used to assess the geographical distribution of Lyme disease risk, but cannot reliably predict Lyme incidence from year to year.

Prevalence of And Risk Factors for Canine Tick Infestation in The United States, 2002–2004

“…Exposure to B. burgdorferi in dogs was shown to occur less frequently in North Carolina than in Virginia, Maryland, and Pennsylvania, where 30-40 times as many cases of Lyme disease were reported than in North Carolina (Duncan et al 2004). Seropositivity in dogs to E. phagocytophila (agent of human granulocytic ehrlichiosis), B. burgdorferi, R. rickettsii, and E. canis was significantly correlated with abundance of specific tick vectors (Johnson et al 2004, Hinrichsen 2001.…”

“…There is generally good agreement between the spatial and temporal distribution of tickborne diseases and the primary vectors (Ciesielski et al 1988, Duncan et al 2004, Fritz and Kjemtrup 2003, Hinrichsen et al 2001, Johnson et al 2004, Sonenshine 1994, Stafford et al 1998. Most tick species are adapted to a single, highly specific habitat and actively seek hosts only during certain well-defined periods of the year during which they are capable of transmitting disease (Sonenshine 1994).…”

The emergence of Lyme disease in Canada

“…These studies and the risk maps can then be used to evaluate, select and target surveillance methods, such as passive surveillance for tick vectors (already in use but with effort that varies geographically 12 ) and surveillance for the presence of Lyme disease vectors on, and evidence of B. burgdorferi infection in, sentinel animals. 25,26 With these methods, it may be possible to predict and then confirm how ticks are spreading in Canada and how endemic areas are expanding, which should in turn allow the targeting of public and physician awareness programs to the areas of greatest risk, for maximum effect.…”

Geographic Variation in the Relationship between Human Lyme Disease Incidence and Density of Infected Host-Seeking Ixodes scapularis Nymphs in the Eastern United States

“…Two more location-specific studies have examined the link between numbers of ticks sampled by passive surveillance and cases in Rhode Island and Maine. 14,15 To our knowledge, these studies are the only studies that have attempted to quantify and/or characterize the relationship between acarological risk and human cases in the eastern United States. However, an understanding of this relationship and how it varies geographically is important for models used in identifying optimal strategies for implementing vector-and reservoir-targeted interventions.…”