In 2011-2013 1588 samples of dogs' blood were examined for dirofilariosis using Knott method, as well as the Kingston and Morton method. The species of microfilariae was determined on the basis of morphometric characteristics. Samples were also examined using the Canine Heartworm Antigen Test. Positive samples were examined using a multiplex PCR assay for species confirmation. Microfilariae belonging to the species D. repens were found in the blood samples of dogs from all the provinces of Poland. The mean prevalence of this species observed in Poland was 11.7%. The range of intensity of infection was counted using the number of microfilariae found in 60 μl of blood amounted to between 1 and 158, and the mean intensity was 18 microfilariae. Microfilariae and antigens of D. immitis were not found in any examined blood samples.

Angiostrongylus vasorum belongs to the superfamily of Metastrongyloidea. This nematode occurs in foxes, dogs and other predators. The Nematode A. vasorum place themselves in the pulmonary artery and its branches, and in the right ventricle and atrium of the heart. Numerous species of land snails are the intermediate hosts of the parasite. In 2013, lungs and hearts of 76 foxes shot in the Forest District Głęboki Bród in Augustowska Primeval Forest were parasitologically necropsied. Four of the examined foxes were infected with the nematode A. vasorum, a prevalence of 5.2%. In one fox pericardium there were 6 male and 6 female nematodes. In the remaining three foxes nematodes were localized in the pulmonary artery. In two foxes 2 specimens of nematodes were detected (male and female, and two females) while 1 female was detected in the other fox. This is the first report of the presence of the nematode A. vasorum in fox in Poland.

Parasitological examination after necropsies of 48 European beavers from Podlaskie and Warmisko-Mazurskie provinces were performed between April 2011 and November 2012. All helminthes were isolated from the contents of the gastro-intestinal tract and their species were determined. In addition, blood samples and faeces were examined. All beavers were infected with six species of parasites. Stichorchis subtriqetrus trematodes were found in 93.7% of animals. They were localized mainly in the caecum, less in the colon, and single juvenile parasites were found in the small intestine. The intensity of infection ranged from two to 893 parasites. Travassosius rufus nematodes (10-4336 specimens) were present in the stomach of 68.7% of the beavers. In the small intestine of four (8.3%) beavers, two-six specimens of Psilotrema castoris were found. This is the first record of this species in Poland and the third of its discovery in the world. Furthermore, in the small intestine of one beaver, two Trichostrongylus capricola nematodes were detected. In the liver of one beaver, pathological changes caused by hydatid cestode Echinococus granulosus occurred. Inflammatory changes of the gastric mucosa caused by Travassosius rufus and of caecum caused by Stichorchis subtriquertus, were observed. Coproscopy was performed with the use of Baermann, flotation, and decantation methods. All results of Baermann method were negative. Examinations with flotation and decantation methods confirmed necropsy findings. Using the flotation method, single oocysts of Eimeria sprehni in one beaver were detected. A blood test conducted by Kingston and Morton method did not reveal the presence of protozoa or microfilariae.