Modern man evolved at least 200,000 years ago. Ticks have a small lead: they have existed for 350 million years. Much is already known about them, but there are still some mysteries to be cracked. As nature lovers, the paths of horses and riders cross with those of ticks particularly frequently. We have collected facts about ticks and other biting insects, talked to experts about current developments and asked: What is the forecast for 2020?
Someone who knows all about the eight-legged bloodsuckers is the married couple Dr. Lidia Chitimia-Dobler, veterinarian and tick expert, and Dr. Gerhard Dobler, microbiologist in the German Armed Forces and coordinator of the TBENAGER project (Tick-Borne Encephalitis in Germany). In this project he is investigating early summer meningoencephalitis (TBE) with partners from the public health service and the universities of Hohenheim, Leipzig, Munich, Hannover and Magdeburg. The oldest of the amber ticks is about 100 million years old. The crazy thing is that it hardly looks any different from the parasites that plague our horses and us today. “We can clearly assign each of these ticks in amber to the genera that still exist today,” says Dr. Dobler. Ticks have existed for over 350 million years. Physically, the bloodsuckers have changed very little over time, but changing living conditions also affect the crawlers that are usually so successful.
At the moment there are about 910 tick species known worldwide. About 60 of them are found in Europe and 20 in Germany. On horses – and humans – for example the common wood tick, the alluvial tick or the hedgehog tick. They prefer it rather humid, which was quite common in this country in the past. The wood tick is the most common tick in Germany. It can transmit pathogens that lead to anaplasmosis, borreliosis and TBE. The number of ticks with the dangerous protozoa, viruses and bacteria on board varies regionally. The alluvial forest tick occurs mainly in the South and East of Germany, but seems to be on the rise. Prof. Dr. Christina Strube from the Institute of Parasitology at the Foundation of the University of Veterinary Medicine Hannover is investigating how widespread different tick species are: “Preliminary results suggest that the alluvial forest tick is spreading from East to West in Germany. Only a few years ago, Magdeburg was known as the border, but by now we can also find this species near Hannover”.
Record years, but why?
The unusually hot, dry year 2018 is considered the record year in terms of tick numbers in Germany, and in 2019 there were also many of the crawlers on the move. But why were there such large tick populations if our native ticks do not like drought? “Actually, we had assumed that they would have to be less active,” says Dr. Dobler. “But in our studies we see that they simply exhibit different behaviour.” Dr. Dobler and his colleagues collect an average of 30,000 ticks per year in Bavaria alone, which are examined for the TBE virus. Up to now, the bloodsuckers have mainly been found in the transition zones from forest to meadows. “Instead, the ticks now appear more frequently in forests, where conditions are probably still very good,” Dr. Dobler observed.
Past and future
The adaptability of the bloodsuckers therefore plays a role. In addition, the number of ticks in a given year is also influenced by conditions that have already existed in previous years. The ticks, which were so numerous in 2018, already developed in 2016 and 2017, depending not only on the weather but also on the food supply for larvae and nymphs, i.e. the early stages of development. If there are relatively few rodents such as mice, this has an effect on the parasites, as Dr. Dobler explains: “The larvae and especially nymphs suck blood from rodents. If there are few rodents, many larvae and especially nymphs do not find a host and hibernate into the next year. The numbers of ticks are then much higher than could be assumed based on calculations with the weather of previous years.” However, reliable predictions on future tick numbers are hardly possible due to the complexity of the interaction of many components. Moreover, the relevant factors differ regionally. Dr. Dobler emphasizes: “So far, there is no really well applicable model to make predictions”. Long-term studies are necessary in order to be able to make more precise statements about the relationship between tick populations and changing conditions such as increasing drought.
In 2018, Hyalomma ticks were reported for the first time in Germany. These originate from the steppe regions of the Mediterranean and Africa. They are larger than woodbuck & Co. and go actively hunting. A few specimens in Germany were already described by scientists in 2015, but in 2018 and 2019 the ticks appeared more frequently. Whether they were really newcomers, which reached us via migratory birds, or whether they had lived with us before and were just not recognized as Hyalomma ticks, is not certain. “After we put pictures on the web, many people said that they had seen such animals before but thought they were spiders,” Dr. Dobler recalls.
So far, there is no vaccine that could be effective against all tick species. However, there is a vaccine that is effective against strains of all three Borrelia species relevant in Europe. Horses can be vaccinated from the age of 12 weeks. Tick repellent products, regular searching of the horse and the fastest possible removal of the ticks (pulling them out, not twisting them) are therefore extremely important.
TBE risk group: Riders
A vaccine against the dangerous TBE is available for humans and the vaccination is recommended according to Dr. Dobler: “For Lyme disease and other tick infections we have possibilities of antibiotic therapy. Unfortunately not for TBE. If someone falls ill, it is always a fateful course and can only be influenced symptomatically by medication”. The risk for riders to fall ill with TBE is high, simply because they are out in the wild more often and for longer periods of time where ticks can get to them. Horses rarely suffer from TBE. However, if the disease becomes clinically apparent, it can be severe or even fatal.
In Bavaria and Baden-Württemberg, between 85 and 90 percent of all human TBE cases in Germany are registered. Whether a classical risk area or not, horse owners should protect themselves and their horses accordingly.
Author: Lena Schwarz/equitrends International
Repellents and insecticides
In order to drive away mosquitoes, blackflies, ticks and other pests different repellents are available on the market. They are either based on synthetic substances, such as diethyltoluamide (DEET), icaridine or essential oils such as eucalyptus oil or lemon oil. Manufacturers have reacted to the current developments of the pests: For example, Zedan‘s Bremsenbremse is already supposed to deter the West Nile virus vector mosquito and the Hyalomma tick. It is intended for humans and horses and is based on an active ingredient complex of Icaridin and EC oil.
Other horse owners prefer the strategy of killing pests off. In this case insecticides are the remedy of choice. Here, however, the requirements are higher. Horse owners have to keep their own health and that of the horse in mind and these synthetic substances should not be used too extensively. Special rugs as for example by Pfiff help to get rid of these plagues, too.
As a retailer, the first thing you should do is find out whether your customer is looking for a product with natural ingredients or whether he is more familiar with chemical products. The agents also vary in duration of action and form of administration (e.g. spray, lotion, gel etc.). When applying the products, customers should make sure that they avoid nostrils, eyes, mucous membranes and wounds.