An analysis of companion animal tick encounters as revealed by photograph-based crowdsourced data

Abstract

Background: Community science is increasingly utilized to track important vectors of companion animal disease, providing a scalable, cost-effective strategy for identifying new foci, changing phenology, and disease prevalence across wide geographies.

Objectives: We examined photographs of ticks found attached to predominately dogs and cats reported to a photograph-based tick surveillance program to identify potential areas for improvements in tick prevention education and risk intervention.

Methods: We compared estimated days of tick attachment using a Kruskal-Wallis one-way analysis of variance, and a Pearson's chi-square analysis of variance on the number of submissions by host type submitted for each season.

Results: The blacklegged tick (Ixodes scapularis) was the most common species reported (39.8%). Tick photographs submitted were almost entirely adults (89.5%), and ticks found on companion animals exhibited an estimated median engorgement time of 2.5 days. Ixodes scapularis displayed the highest median engorgement of the top tick species found feeding on companion animals (χ² = 98.96, p < 0.001). Ticks were spotted year-round; during spring and summer, ticks collected from pets represented 15.4 and 12.8% of all submissions, but increased to 28.5 and 35.2% during autumn and winter, respectively.

Conclusions: Crowdsourced data reveal that mostly adult ticks are detected on pets, and they are found at a point in the blood-feeding process that puts pets at heightened risk for disease transmission. The increase in proportion of ticks found on pets during colder months may reveal a critical knowledge gap amongst pet owners regarding seasonal activity of I. scapularis, a vector of Lyme disease, providing an opportunity for prevention-education.

Keywords: cats; community science; dogs; tick-borne disease.

FIGURE 1

Comparison of estimated tick feeding time (days) on companion animals versus those found on humans or found unattached for ticks reported to the TickSpotters Program from 2014 to 2018. Tick feeding time was assessed by comparison to a pictorial tick engorgement chart based on the scutal index. Median engorgement for human‐encountered ticks (n = 20,710) was 1 day‐fed (SD = 1.39, SE = 0.01, range = 0‐8 days). Median attachment for pet‐encountered ticks (n = 5033) was 2.5‐days‐fed (SD = 2.11, SE = 0.01, range = 0‐9 days). Median engorgement for unattached ticks (unfed or replete) (n = 1880) was 0 days‐fed (SD = 2.29, SE = 0.05, range = 0–9 days). *** p < 0.001. ** p < 0.01. ns = Not significant

FIGURE 2

Violin boxplot displaying engorgement at detection (days) of the five most commonly reported tick species found on pets that were submitted to TickSpotters from 2014 to 2018. Feeding times were estimated by comparison to a pictorial tick engorgement chart created by TERC that removed feeding ticks from hosts at half day intervals, and was based on the scutal index. The horizontal bar within the box represents the median engorgement for each species. The dots represent the mean engorgement. Kruskal–Wallis nonparametric analysis of variance tested statistical difference among the species engorgement distributions. Effect size is denoted by episilon². Post‐hoc pairwise comparisons were conducted using the Dwass‐Steel‐Crichtlow‐Fligner method and (Holm) adjusted p‐values for statistically significant distributions are noted between species whose overall submissions were statistically different in engorgement

FIGURE 3

Comparison of seasonal tick encounter submissions by host (i.e., on whom or how the tick was found) out of the total United States submissions (no pet tick encounters were submitted from other countries) using Pearson's chi‐square analysis. Effect size is denoted by Cramer's V. ***p < 0.001