Seasonality and changing prevalence of common canine gastrointestinal nematodes in the USA

Jason Drake,Tom Carey

doi:10.1186/s13071-019-3701-7

Abstract

BackgroundThe three most commonly diagnosed gastrointestinal parasites of pet dogs within the USA are the whipworm, the hookworm, and the roundworm. The collection of large data sets from various sources throughout the industry have produced a number of publications on parasite prevalence in recent years. In this study, we look at data captured by the Companion Animal Parasite Council from 2012–2018, which includes 4.3–7.2 million annual fecal exams, to evaluate not only changes in prevalence, but also possible seasonal fluctuations of the three most common canine gastrointestinal parasites.MethodsAnnual and monthly data were collected from the CAPC parasite prevalence maps for canine roundworms, hookworms and whipworm. The map data were provided to CAPC by two large national reference laboratories. The data were evaluated for changes in prevalence on a monthly basis throughout each year as well as changes in prevalence from year to year from 2012–2018. Additionally, positive test results and total tests performed for each of the three parasites from 2012–2018 during individual months were totaled without using the year as a variable in order to evaluate the results for seasonality (i.e. all tests and positive results occurring in January, regardless of year, were totaled and analyzed).ResultsEvaluation of gastrointestinal nematode prevalence data from over 39 million fecal samples examined over a 7-year period revealed a subtle, yet significant, increasing prevalence for roundworms, an increasing prevalence for hookworms, and a slightly decreasing prevalence for whipworms. Seasonality was demonstrated for roundworms, hookworms, and to our knowledge, for the first time canine whipworms. Highest seasonal prevalence for roundworms, hookworms, and whipworms occurred during December–January, July–August, and January–February, respectively.ConclusionsEvaluation of monthly gastrointestinal parasite prevalence data from over 39 million fecal samples collected over a 7-year period revealed a slightly increasing prevalence for roundworms, an increasing prevalence for hookworms, and a slightly decreasing prevalence for whipworms. In addition to the annual changes in prevalence, seasonal prevalence was shown for the first time for whipworms. Prevalence of both whipworm and roundworm peaked in the winter, while prevalence of hookworm peaked in the late summer and early autumn.

Highlights

The three most commonly diagnosed gastrointestinal parasites of pet dogs within the USA are the whipworm, the hookworm, and the roundworm
Evaluation of monthly gastrointestinal parasite prevalence data from over 39 million fecal samples collected over a 7-year period revealed a slightly increasing prevalence for roundworms, an increasing prevalence for hookworms, and a slightly decreasing prevalence for whipworms
Prevalence of both whipworm and roundworm peaked in the winter, while prevalence of hookworm peaked in the late summer and early autumn

Summary

Introduction

The three most commonly diagnosed gastrointestinal parasites of pet dogs within the USA are the whipworm, the hookworm, and the roundworm. Whipworms exhibit intermittent egg shedding, relatively low numbers of eggs produced per worm compared to other common gastrointestinal nematodes like canine roundworm (T. canis) and canine hookworm (A. caninum), and production of very dense eggs that are difficult to find using passive fecal floatation with solutions of specific gravity less than 1.027 [8, 9]. The recent availability of fecal antigen diagnostic tests, which can detect roundworm, hookworm and whipworm infections in dogs, should improve the ability of veterinarians to diagnose infections with these gastrointestinal nematodes [10, 11]. National studies of gastrointestinal nematode prevalence in pet dogs receiving veterinary care indicate a prevalence of roundworms of 1.8–5.0% [5,6,7], hookworms of 2.5–4.5% [5, 6] and whipworms of 0.8–1.2% [5, 6]

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