Veterinarians across Poland have been reporting cases of dogs with symptoms of severe anaemia, lethargy and wasting. Scientists have shown that the dogs were attacked by a parasitic protozoan. It turns out that it also poses a threat to wolves.
For several years, veterinarians in Poland have been struggling with cases of dogs suffering from serious body disorders caused by an unknown parasite. The animals suffered from anaemia and fell into lethargy, and the progressive disease led to cachexia, i.e. significant destruction of the body.
The first case was recorded in 2021 in Ostrowiec Świętokrzyski. In 2022, similar symptoms were found in several animals from the vicinity of Świdnik, Gdańsk, Hajnówka and Błędów. Although dogs of all ages had symptoms, they were particularly severe in older dogs.
Scientists from the Institute of Biochemistry and Biophysics of the Polish Academy of Sciences, the Faculty of Biology of the University of Warsaw and Vetlab used molecular methods to determine that the cause of the disease was the parasitic protozoan Hepatozoon canis. The researchers also extended their analyses to dogs' wild ancestors, wolves. Animals infected with this protozoan have also been found in their population. The research results have just been published in the journal Parasites & Vectors (https://doi.org/10.1186/s13071-023-05928-5).
Infections with this protozoan in dogs were first described in India in 1905. Currently, hepatozoonosis is a common disease of dogs in the Mediterranean region. Cases of infection in dogs in Central Europe have been reported in Hungary, Czechia, Ukraine, Slovakia and Germany. Studies have also shown parasite infection in wild predators - golden jackals, wolves and red foxes.
Scientists suspect that many cases of this disease were not diagnosed due to lack of appropriate diagnostics. The author of the study, Dr. Katarzyna Tołkacz from the Institute of Biochemistry and Biophysics of the Polish Academy of Sciences, says: 'The increase in the number of cases of hepatozoonosis in dogs indicates that this disease may become a significant problem in our country. It is therefore necessary to raise the awareness of veterinarians so that they extend the diagnosis to include another potential tick-borne disease.’
The researchers' suggestion has been confirmed by the case of dogs from Tłuszcz, admitted to a veterinary clinic in 2020 with suspicion of babesiosis. However, the tests performed at that time did not detect infection with the protozoan Babesia canis that would cause the disease, and the cause of the disease remained unexplained. Later tests of blood taken from sick dogs, performed by Dr. Tołkacz, showed that they suffered from hepatozoonosis.
The vector of the parasitic protozoan are ticks, especially the brown dog tick, also called the kennel tick, Rhipicephalus sanguineus. This species has not been detected in Poland yet. However, it is widespread in the Mediterranean area, from where it may have come to the country along with the dogs of people vacationing in that area. It has been observed that as the climate warms, R. sanguineus is expanding its range from southern Europe to the north.
Unlike other tick-borne diseases, such as Lyme disease, the parasite that causes it does not enter the host's body through a tick bite. 'Infection occurs by eating a tick infected with the protozoan, for example while cleaning fur with teeth. A dog can also become infected by eating another infected dead animal,’ Dr. Tołkacz says.
They suspect that this path of transmission of the parasite is the cause of hepatozoonoses observed in Central Europe, in both dogs and wild canids. In nature, dogs can hunt wild animals, they also have easy access to dead foxes hit by cars and carcasses of these animals left in the forests by hunters. Wild animals, such as wolves, foxes and jackals, can also use this food source.
Parasitic diseases are a significant factor in mortality in large carnivore populations around the world. 'In Poland we previously detected wolves that died due to scabies infection and suffered from tick-borne diseases, e.g. anaplasmosis and babesiosis,’ says the co-author of the study, Dr. Robert Mysłajek, a professor at the University of Warsaw and vice-president of the Association for Nature 'Wolf'. 'Hepatozoon canis is another on the list of natural enemies of these predators,’ he adds.
The research was co-financed by the Polish National Science Centre. (PAP)
lt/ zan/ kap/
tr. RL
