University of Veterinary Medicine

No winter break for ticks in Germany

Researchers at the University of Veterinary Medicine’s Institute of Parasitology have found that ticks remain active in winter.

Research scientists from the institute of Parasitology at the University of Veterinary Medicine Hannover (TiHo) have observed that ticks in Germany are now active all year round. The Institute’s head, Professor Christina Strube, says: “Because winters are now milder, ticks seek out a host during this season of the year as well. This means that pets now need year-round protection against these parasites. And, of course, people should also make sure to check themselves for ticks after spending time outdoors in winter.”

Rising average temperatures and lower snowfall

The climate crisis has brought a continuous increase in mean temperatures for some decades now. Mild winters, and associated low levels of – or, frequently, complete absence of – snowfall influence tick activity. According to Germany's national meteorological service, the Deutscher Wetterdienst (DWD), average winter temperatures during the months of December, January and February have in recent years been up to 3.1 degrees Celsius higher than in the climatic reference period from 1961 to 1990.

Two main species of tick in Germany

In Germany, the two most prevalent tick species are the castor bean tick (Ixodes ricinus) and – on the increase for a number of years now – the ornate cow tick (Dermacentor reticulatus). Strube reports: “We were able to utilize three different approaches to observe winter activity in each of these species: using field collection sites, using tick plots, and using ticks that veterinary practitioners submitted to us for examination.” The field study involved the researchers dragging a piece of cotton cloth over the ground vegetation, known as the flagging method. Active ticks climb onto the underside of the cloth, enabling them to be subsequently collected and counted. Tick plots are a quasi-natural, open-air habitat within which ticks can climb up wooden rods, where they can easily be seen and counted. For the year-long submission study, the investigators examined almost 20,000 ticks and documented how many castor bean ticks and ornate cow ticks had bitten dogs and cats during the winter months.

Ticks active in winter

The ornate cow tick is constantly active throughout the winter – except when it’s snowing. “It ceases activity when there is unbroken snow cover,” Strube comments, “but both it and the castor bean tick are now active from December to February in mild winters. Especially in February, we can observe a marked increase in the activity of both tick species.”

Carriers of infectious diseases

Since ticks act as ‘vectors’, able to carry various infectious diseases, it is now the case that both humans and animals are at risk of infection with tick-borne diseases all year round. Relevant examples affecting animals include babesiosis and anaplasmosis, as well as – to a lesser extent – borreliosis. In Germany, the most prevalent tick-borne illnesses in people are borreliosis and early-summer meningoencephalitis.