Year-round tick exposure of dogs and cats in Germany and Austria: results from a tick collection study

Abstract

Background: Ticks and tick-borne diseases play a major role in companion animal health. Additionally, the European tick fauna is changing, for instance due to the spread of Dermacentor reticulatus, displaying a higher likelihood of winter activity than Ixodes ricinus. Therefore, we investigated current tick infestations in dogs and cats in Germany and in parts of Austria and the seasonal infestation risk.

Methods: Overall, 219 veterinary practices were invited to collect ticks from cats and dogs on a monthly basis. Ticks were morphologically identified and female I. ricinus specimens were measured to estimate attachment duration.

Results: In total, 19,514 ticks, 17,789 (91.2%) from Germany and 1506 (7.7%) from Austria, were received between March 2020 and October 2021, with 10,287 specimens (52.7%) detached from dogs, 8005 from cats (41.0%) and 1222 from other species (6.3%). In Germany, the most common tick species collected from dogs were I. ricinus (78.0%) and D. reticulatus (18.8%), while cats mainly harboured I. ricinus (91.3%) and I. hexagonus (5.5%) and only few D. reticulatus (0.6%). In Austria, collected I. ricinus reached similar proportions in dogs (90.4%) and cats (95.3%), followed by D. reticulatus in both dogs (5.2%) and cats (1.5%), with I. hexagonus (0.9%) collected only marginally from cats. The average infestation intensity amounted to 1.62 ticks/dog and 1.88 ticks/cat. The single to multiple infestation ratio was 79.1% to 20.9% in dogs and 69.0% to 31.0% in cats, with cats being significantly more often multiple infested than dogs, while the proportion of mixed-species infestations was 2.0% for both dogs and cats. The average attachment duration of female I. ricinus specimens amounted to 78.76 h for dogs and 82.73 h for cats. Furthermore, year-round tick exposure was confirmed, with 108 D. reticulatus and 70 I. ricinus received on average per month during December 2020 to February 2021.

Conclusions: The study shows a year-round tick infestation risk, with activity of both D. reticulatus and I. ricinus during winter, and confirms the widespread occurrence of D. reticulatus in Germany. Additionally, long average attachment durations and frequent multiple infestations underline the need for adequate year-round tick control, even during the winter months.

Keywords: Cat; Dermacentor reticulatus; Dog; Europe; Geographical distribution; Ixodes hexagonus; Ixodes ricinus; Pets; Ticks; Winter.

Fig. 1

Species distribution of the most common ticks collected from dogs and cats in Germany and Austria. Percentages refer to the proportion for each host species

Fig. 2

Developmental stage distribution of the three most frequently detected tick species on dogs (A) and cats (B). Percentages refer to the proportion for each tick species

Fig. 3

Geographical distribution (zip code areas) and number of all ticks (A), I. ricinus (B) and D. reticulatus (C) detached from dogs and cats in Germany and Austria. A map of the federal states of Germany and Austria is shown in the upper right corner (Germany: BW = Baden-Württemberg, BY = Bavaria, BE = Berlin, BB = Brandenburg, HB = Bremen, HH = Hamburg, HE = Hesse, LS = Lower Saxony, MV = Mecklenburg-Vorpommern, NW = North Rhine-Westphalia, RP = Rhineland-Palatinate, SL = Saarland, SN = Saxony, ST = Saxony-Anhalt, SH = Schleswig–Holstein, TH = Thuringia; Austria: BU = Burgenland, CA = Carinthia, LA = Lower Austria; UA = Upper Austria, SA = Salzburg; ST = Styria, TY = Tyrol, VA = Vorarlberg, VI = Vienna)

Fig. 4

Proportions of the three most frequent tick species detached from dogs per German federal state. A map of the federal states of Germany is shown in the upper right corner (Germany: BW = Baden-Württemberg, BY = Bavaria, BE = Berlin, BB = Brandenburg, HB = Bremen, HH = Hamburg, HE = Hesse, LS = Lower Saxony, MV = Mecklenburg-Vorpommern, NW = North Rhine-Westphalia, RP = Rhineland-Palatinate, SL = Saarland, SN = Saxony, ST = Saxony-Anhalt, SH = Schleswig-Holstein, TH = Thuringia)

Fig. 5

Multiple and single infestations with the two most frequently collected tick species on dogs (I. ricinus [A] and D. reticulatus [B]) and cats (I. ricinus [C] and I. hexagonus [D]) over the course of the study. Red boxes illustrate the main periods of tick species-specific differences

Fig. 6

Number of infestations with more than one tick species on dogs and cats per study month

Fig. 7

Distribution of attachment time of female I. ricinus specimens collected from dogs (A) and cats (B)

Fig. 8

Collected I. ricinus and D. reticulatus specimens per actively participating veterinarian over the course of the study period (A) and total number of received ticks per month (B). The number of specimens per active participant is not indicated for March to April 2020 or July to October 2021, as these periods were outside the 14-month study period and no collection kits were sent out for these months