Surveillance: There are several methods used by researchers for tick surveillance including both active and passive methods.
Active surveillance is used to further determine whether a species of tick is established within a certain area and researchers actively go out into the field to collect tick specimens by various methods including flagging or dragging, collection from host or reservoir animals and other methods.
Passive surveillance is where tick specimens are voluntarily submitted to state or federal public health departments or disease surveillance laboratories by veterinarians, physicians and the general public.
- Dragging or flagging for ticks with cloth flags over vegetation
- Collecting ticks from host or reservoir animals or aspiration of excavated burrows or nests of hosts
- Collecting from an investigators clothing
- Using live, caged sentinel animals
- Carbon dioxide baited traps
- Use of domestic animals (e.g. dogs and Lyme disease) as sentinels for human disease– Johnson et al. (2004) found domestic canine seropositivity for Lyme disease was significantly correlated with human Lyme disease cases by county in two years of testing and by town in one out of the two years of testing in a passive tick surveillance study in Rhode Island. In another recent study by Mead et al. (2011), canine seroprevalence >5% for Lyme disease was a sensitive but non-specific indicator of risk for human Lyme disease while canine seroprevalence of <1% was associated with little to no risk for human Lyme disease infection. Other studies have also proposed canine Lyme seroprevalence as a sensitive and independent indicator of human Lyme disease risk (Duncan et al. 2004; Guerra et al. 2001; Lindenmayer et al. 1991).
- Passive surveillance– In a study by Johnson et al. (2004) data from nymphal Ixodes scapularis ticks submitted by the general public to the University of Rhode Island Tick Research Laboratory were compared to human Lyme disease case data from the Rhode Island Department of Health to determine the efficacy of passive tick surveillance as an indicator of human risk of Lyme disease. Their results demonstrated that numbers of ticks submitted and tested highly correlated with human cases both by county as well as town and that passive surveillance was an effective method to assess geographical risk of Lyme disease. Data provided from an 18 year passive statewide tick identification program in Maine found that submissions of nymphal stage I. scapularis were highly correlated with reported Lyme disease cases at the county level. They were also able to collect information on tick stage, degree of engorgement, seasonal abundance, geographical location, host and age of person from which the tick was removed and create distribution maps of the three major species submitted (Dermacentor variabilis, Ixodes scapularis and Ixodes cookei) (Rand et al. 2007).
Passive tick surveillance has been employed by Canada since the 1990 due to the expanding geographic range of Ixodes scapularis (Ogden et al. 2010; Ogden et al. 2006), but researchers have found this method lacks specificity for determining areas where tick populations are established due to dispersion of ticks from established areas by migratory birds (Koffi et al. 2012). In a study in Quebec, Ontario, Canada by Koffi et al. (2012), a logistic regression model was developed for estimating the risk of I. scapularis population establishment based on the numbers of ticks submitted via passive surveillance and an environmental suitability index. Passive surveillance data was then used to create risk maps which identified areas of emerging Lyme disease risk at a geographic scale conducive for local Lyme disease prevention and control activities.
Johnson JL, Ginsberg HS, Zhioua E, Whitworth UG, Markowski D, Hyland KE, Hu R. (2004). Passive tick surveillance, dog seropositivity and incidence of human lyme disease. Vector Borne Zoonotic Dis. 4(2): 137-42.