Veterinary session

In the past, many studies have been performed on parasites of animals living in the natural environment, however, the study of parasites of non-domesticated mammals living in an synanthropic environment is very important for public health. Because of their role in spreading zoonotic infection, the study of mass-occurring rodents such as rats in human settlements is of paramount importance. Wild rats, known mediators of bacterial and viral diseases, have been studied in a number of ways, but the effects of their parasites on humans have been less frequently analysed. In Central Europe, the study of the Norway rat (Rattus norvegicus) is warranted. Data on parasites of the Norway rat can be found mainly in Serbia and Croatia from areas close to Hungary. Even though the Norway rat is a well-known rodent species in Hungary as well, till now no comprehensive study has been conducted in the country on its parasitic diseases.

A research study was conducted on 131 rat carcasses in a test condition during the period of September 2020 to May 2021. The carcasses were received from 8 different districts of Budapest, Hungary. Preliminary morphological tests showed that at least one parasite species was detected in 110 of the examed carcasses. This high prevalence of 84% suggests that almost all rats contain parasites. Such high levels of infestation are very rare in populations of animals living in natural habitats and suggest the urbanization of the rat population. The preliminary morphological examination of ecto- and endoparasites was performed using a microscope which was followed by further molecular and histological procedures to identify the parasites. As a result, the following three main types of parasites were found in the examined rat carcasses:

Protozoan parasites: Eimeria sp.,Entamoeba sp., Arthropods: Nosopsyllus fasciatus, Polyplax spinulosa, Laelaps sp.,Ixodes ricinus, Haemaphysalis sp. Demodex sp., helminths: Heterakis spumosa., Nippostrongylus brasiliensis, Capillaria sp.,Syphacia muris, Gongylonema sp., Trichosomoides crassicauda.

In addition, three species of worms of zoonotic significance were found in rats: Hymenolepis nana, Hymenolepis diminuta (tapeworms) and Calodium hepaticum (nematode), the latter living in the liver.

Results show that the parasites found in the studied rats are common species and their occurrence could be expected from the outset. However, it is an important finding that within some districts of a large city almost all well-known rat parasites could be found which shows the high diversity of infection. While in other countries, captured rats alive have been studied for parasites, our studies to date confirm the parasites also be detected in the carcasses of poisoned animals, by relatively simple methods.

It can also be used to monitor larger volumes of rat populations, which may have epidemiological significance in the future.