The occurrence and molecular identification of Thelazia spp. in European bison (Bison bonasus) in the Bieszczady Mountains

Infection with Thelazia nematodes results in eye disease in wild and domestic animals. The aim of the present study was to describe the occurrence of Thelazia nematodes in European bison, and to subject the isolated parasites to molecular identification and phylogenetical analysis. The eyeballs of 18 European bison from the Bieszczady Mountains, culled due to dysfunctional vision, were collected for study. The conjunctival sacs, tear ducts, corneal surface and nictitating membrane were rinsed with a saline solution. Any obtained nematodes were isolated under a stereoscopic microscope, and then identified as T. gulosa or T. skrjabini by molecular analysis of partial cox1 sequences. The prevalence of infection with Thelazia spp. was found to be 61%, with a 95% confidence interval (CI 95%) of 39-80%. Thelazia skrjabini was isolated from 56% (CI 95% 34-75%) of examined animals; T. gulosa was significantly less common (p = 0.038) with the prevalence of infection reaching 22% (CI 95% 9-45%). Three European bison were cross-infected with both T. gulosa and T. skrjabini. Phylogenetic analysis found the obtained sequences to be similar to those of Thelazia species from domestic ungulates in Europe. Infection intensity ranged from 1 to 16 nematodes per individual (median of three nematodes), and was significantly higher in females (6 nematodes) than in males (1 nematode; p = 0.019). A tendency for seasonal occurrence of nematodes in European bison was also observed. Our study provides further information regarding the patterns of Thelazia transmission in European bison in Poland.

Occurrence of chosen parasitic protozoa of roe deer (Capreolus capreolus) and red deer (Cervus elaphus) in Poland: a current review

Both roe deer (Capreolus capreolus) and red deer (Cervus elaphus) are wild ruminants that are present in large numbers in Poland. Although both are very often infected with parasitic protozoa, the species composition of these parasites and their prevalence are relatively poorly known. The aim of the present work is to gather existing data on the occurrence and species diversity of parasitic protozoa of the genus Eimeria, Babesia, Theileria, Giardia, Cryptosporidium and family Sarcocystidae in red deer and roe deer in Poland and compare the findings with those from other European countries.

Rare case of presence of nematodes Dirofilaria repens in apleural cavity of a dog

Dirofilariosis, caused by nematodes Dirofilaria repens, is a parasitosis of wild and domestic carnivores. Nematodes D. repens locate in the subcutaneous and intramuscular tissue. The aim of this article is to describe rare case of pleural infection of a dog with nematodes D. repens. 12-year-old golden retriever had been treated in the veterinary clinic due to emaciation, weakness and dehydration, observed for 2 weeks. Hematologic and biochemical tests revealed reduction in the number of leukocytes and erythrocytes, significant decrease of hemoglobin, hematocrit and albumins as well as increased ALAT, urea and creatinine levels. Parasitological examination of blood smear revealed the presence of multiple microfilariae. Increased echogenicity of renal parenchyma was visible during ultrasound examination. Necropsy of euthanized animal revealed adult nematodes D. repens, located in the pleural cavity. Additionally, enlarged kidneys with subcapsular petechiae and a single cyst in the renal cortex were observed. To our best knowledge, it is the first case of finding nematodes D. repens in a pleural cavity of a dog.

Gastrointestinal Helminths of a European Moose Population in Poland

Parasitic infections have a negative impact on the fecundity and survival of wild ruminants, particularly moose; however, despite being more susceptible to parasitic diseases than other wild cervids, they remain poorly examined in this regard. Therefore, the aim of the present study was to identify gastrointestinal and liver helminth species of the moose population in central Europe, assess the factors contributing to infection intensities and examine their impact on moose health. Abomasum, small intestine, caecum and liver samples were collected from 46 moose in Poland and evaluated for helminth parasite fauna and histopathological changes. Additionally, 289 moose fecal samples were analyzed for the presence of eggs, oocysts and larvae of parasites. In total, 19 parasite taxa were identified. The most prevalent were Mazamastrongylus dagestanica and Ostertagia antipini, which are typical nematodes of moose, together with Spiculopteragia boehmi and O. leptospicularis, characteristic also of other cervids. Parasite species diversity and abomasal parasitic infection intensity were higher in adult moose than in yearlings and calves. The numbers of histopathological lesions depended on the intensity of parasitic infections, and were most severe in the livers of moose infected with Parafasciolopsis fasciolaemorpha. The analysis of fecal samples revealed several regional differences in the levels of parasite eggs, oocysts and larvae shedding. Our findings indicate an accumulation of parasite infections over time in moose, which may be related to high environmental parasite pressure, possibly connected with high moose density and the presence of wetlands; they also serve as the most comprehensive study of moose parasites in central Europe to date.

Biodiversity of lung helminths in terrestrial mammals from Eastern Europe

This review provides the results of many years of original studies of the authors published in different journals and compilations taking into account an analysis of literature data. The studies on biological diversity of lung helminths of terrestrial mammals were performed by the authors in Armenia, Bulgaria and Poland. Literature data on European Russia were also taken into account. Sixteen animal species from the families Cervidae (six species), Bovidae (nine species) and Leporidae (one species) were investigated. In these animal taxons 27 helminth species from the families Dictyocaulidae (five species), Protostrongylidae (20 species), and Taeniidae (two species) have been found. Lung nematodes Muellerius capillaris and Protostrongylus hobmaieri, as well as zoonotic parasite E. granulosus were found to be common for all the countries studied. Also, relatively many species appeared common between several studied regions. Taking into account morphology, ecology and life cycles, we support a validity of genera Echinococcus and Alveococcus in the structure of the subfamily Echinococcinae of family Taeniidae.

First report of a newly-described lungworm, Dictyocaulus cervi (Nematoda: Trichostrongyloidea), in moose (Alces alces) in central Europe

Lungworms from the genus Dictyocaulus are the causative agents of verminous pneumonia in domestic and wild ungulates. Recently, in 2017, a new species was isolated from red deer and described as Dictyocaulus cervi; however, little is known about its epidemiology and pathogenicity in other cervids. The aim of our study was to determine the extent of infection with Dictyocaulus nematodes in the moose population in Poland. Parasitological necropsies were performed in 18 moose and 249 faecal samples were analysed. A combination of multiplex PCR and analysis of the partial SSU, cox1 and cyt B regions revealed the presence of D. cervi infection in two of the necropsied moose. Histopathological examinations revealed changes, including multiple cross sections of larvae of nematodes in alveoli, massive pulmonary fibrosis, mononuclear cell infiltration and diffuse alveolar damage in the lungs of four animals. The lesions were more pronounced when adult Dictyocaulus nematodes were present in the bronchi and bronchioles. Some of the observed pathological changes could be attributed to co-infection by nematodes of the Protostrongylidae, whose larvae were found in all four animals with lung pathologies. In the faeces, Dictyocaulus sp. larvae only occurred together with Protostrongylidae larvae; in addition, higher numbers of Protostrongylidae larvae were excreted in the faeces of animals with dictyocaulosis. The present study is the first report of the presence of D. cervi in moose, and demonstrates the value of multiplex PCR in the identification of Dictyocaulus nematodes. Our findings indicate that co-infections with multiple species of lung nematodes in moose may be commonplace, and this should be considered as a factor aggravating the course of parasitosis.

Usefulness of PCR-RFLP of 18S rRNA gene for rapid post-mortem diagnostics of highly pathogenic Eimeria spp. (Apicomplexa: Eimeriidae) of European bison, Bison bonasus L. with histopathological correlation

Eimeria spp. infection was investigated in 10 free-roaming European bison aged three months to 26 years by anatomopathological, histopathological, coproscopic and PCR-RFLP examination. The coproscopic study identified Eimeria oocysts in the faeces of five bison. The most prevalent morphotypes were E. bovis, present in all positive samples, and E. zuernii, in all but one. Additionally, mixed infections consisting of E. bovis, E. zuernii, E. alabamensis, E. auburnensis, E. canadensis, E. cylindrica, E. ellipsoidalis and E. subspherica were diagnosed in two bison calves. Besides being the most prevalent form, E. bovis also demonstrated the highest OPG (2,750). The presence of oocysts in the faeces was associated with those of macrogamonts, microgamonts and oocysts in the epithelium of the large intestine. Intestinal coccidiosis associated with lymphoplasmacytic enteritis was observed in many bison, not only those with positive OPG. Four animals with negative coproscopy results demonstrated early-stage gametogony in the large intestine; one case presented no endogenous stages of coccidians in the histopathological sections of the intestine, nor oocysts in the faecal samples. A 530 bp product of E. bovis 18S rDNA (GenBank: MK951685) was obtained from both the colon wall and oocysts; this was subjected to PCR-RFLP analysis based on AluI and Hin1II (NlaIII) restriction enzymes. Both samples yielded a consistent seven-band pattern, four of which (270 bp, 40 bp, 180 bp and 84 bp) were expected, and the other three represented undigested fragments. The obtained digestion pattern is indicative of Eimeria spp. infection, and can serve as a first-step diagnostic approach in detection of infection. The result of computer-based virtual digestion of the PCR product suggests that double digestion with Mval (BstNI) and KpnI restriction enzymes may be used as a second-step tool to distinguish between E. bovis, E. zuernii and E. alabamensis, all of which are highly-pathogenic species.

Patterns of parasite eggs, oocysts and larvae shedding by moose in the Biebrza marshland (NE Poland)

The study analyses patterns of endoparasite eggs, oocysts and larvae shedding by moose from the relict population in the Biebrza marshland, NE Poland, which has grown to be one of the largest in Central Europe since the ban on hunting imposed in 2001. The analysis identified 10 species or groups of parasites among 230 faecal moose samples collected over 16 consequent months. The most prevalent were the eggs of Trichostrongylidae, Trichuris spp., Nematodirella alcidis, Parafasciolopsis fasciolaemorpha and the larvae of Elaphostrongylus sp. Four parasite species were more prevalent in males, indicating male-biased parasitism, and the studied moose population exhibited a female-skewed sex ratio. Nematodirella alcidis eggs and Protostrongylid larvae were more prevalent during winter, which indicated their resistance to harsh weather conditions. The prevalence of Eimeria alces and Aonchotheca sp. increased during the growing season, as did the number of eggs per gram of faeces (EPG) of P. fasciolaemorpha, possibly due to the availability of water sources. Higher mean monthly temperature was also found to have a positive effect on the excretion of Trichostrongylidae and Moniezia spp. eggs. In addition, the time of infection and the specificity of the parasite life cycle, being sensitive to certain climatic conditions, also appeared to have a strong influence on eggs, oocysts and larvae shedding in this non-harvested moose population.

The morphological and molecular identification of the tapeworm, Taenia lynciscapreoli, in intermediate and definitive hosts in Poland

The tapeworm Taenia lynciscapreoli is a new species of the genus Taenia described in 2016, and which remains poorly understood. The aim of the present study is to extend current knowledge regarding its, morphology and genome. Biological material was analysed from three species of wild animals: Eurasian lynx (Lynx lynx), roe deer (Capreolus capreolus) and moose (Alces alces). Twenty-four adult tapeworms and four larvae were obtained from Eurasian lynx and roe deer respectively; none were detected in the studied moose. On the basis of morphometric (hooks measurements) and molecular analysis (partial 780 bp cox 1 gene sequences), the analysed tapeworm was identified as Taenia lynciscapreoli species. The phylogenetic analysis of the obtained sequences identified two haplotypes. The obtained findings can be used to supplement the species description. To our knowledge this is the first morphological and molecular identification of T. lynciscapreoli in roe deer, intermediate host, in Poland.

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Study is molecular and morphological identification of T. lynciscapreoli in Poland.

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78 animals from three species were examined: roe deer (71), moose (6) and lynx (1).

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28 parasites specimens were analysed: larvae (4), adult (24).

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This is the first identification of T. lynciscapreoli in roe deer in Poland.

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New description of the tapeworm should include that the number of hooks is 30–38.

Occurrence of tapeworms Moniezia benedeni (Moniez, 1879) in European bison Bison bonasus L. in Białowieża Primeval Forest

Tapeworms Moniezia benedeni are cosmopolitan parasites of wild and domestic ruminants. The aim of this study was to examine the prevalence of those tapeworms in European bison in Białowieża Primeval Forest. Parasitological necropsy of small intestine of 26 bison, aged from 3 months to 26 years was performed in years 2007–2011. Tapeworms M. benedeni were isolated from 11 examined animals and the prevalence of infection was estimated on 42.3%. Intensity of infection was ranging from 2 to 25 tapeworms and the mean intensity was estimated on 5.8 specimens. Prevalence in the group of calves reached 50% and in adult bison – 33.3%. Intensity of infection in calves was estimated on 2 to 5 tapeworms while in adult animals it was ranging from 1 to 2 parasites. High prevalence of tapeworms M. benedeni in European bison might result from poor condition or weak immunity of eliminated animals.

Ashworthius sidemi in cattle and wild ruminants in Poland - the current state of play

Ashworthius sidemi, a blood-sucking abomasal nematode, has been identified in various wild ruminants, including deer (Cervus elaphus), roe deer (Capreolus capreolus), fallow deer (Dama dama) and moose (Alces alces). Although it has been observed throughout Poland, most sightings have been in the eastern part of the country. However, more recently, A. sidemi has been confirmed in the Ruszów Forest District (Lower Silesian Wilderness). It is now possible to test the faeces of cattle for the DNA of the third-stage infectious larvae (L3) of A. sidemi. The present paper describes such a molecular study of 120 faecal samples collected from cattle grazed in the Ruszów Forest District and Biebrza Marshland, where A. sidemi had previously been detected in wildlife. In this study, no A. sidemi DNA was identified in any of the examined samples.

A further increase in the prevalence and intensity of infection with Ashworthius sidemi nematodes in red deer in the Lower Silesian Wilderness

The nematode Ashworthius sidemi is a typical parasite of Asiatic deer, particularly sika deer (Cervus nippon). It was probably first carried into Poland by migrating red deer. The aim of the present study was to determine the prevalence and intensity of A. sidemi infection in roe deer and red deer in the Lower Silesian Wilderness in the winter season 2015/2016. Parasitological necropsy of 34 abomasa of red deer from Forest District Ruszów was performed. The prevalence of A. sidemi infection was found to be 91.1%, and the intensity to range from 10 to 2680 nematodes, with a mean intensity of 394 parasites. This prevalence of ashworthiosis and maximum intensity of infection were respectively 17.2% and 38% higher than observed in the previous season (2013/2014). The mean intensity was also slightly higher than reported previously.

Microfilariae Onchocerca alcis Bain et Rehbinder, 1986 – a new parasite of moose Alces alces (L.) in Poland

Onchocerca alcis Bain et Rehbinder, 1986 belongs to the subfamily Onchocercinae. Mature nematodes of O. alcis are located on the surface of hindlimb tendons. The aim of this article was to describe the occurrence of microfilariae of O. alcis in the skin of moose from Kampinos Forest. This is the first report of O. alcis in moose from Poland and the third finding of this rare species in the world.

Pathological lesions in the lungs of red deer Cervus elaphus (L.) induced by a newly-described Dictyocaulus cervi (Nematoda: Trichostrongyloidea)

The large lungworms of the genus Dictyocaulus are causative agents of parasitic bronchitis in various ungulate hosts, including red deer. Recently, the red deer-derived lungworm D. cervi was described and separated from D. eckerti. Little is known of the transmission patterns, epidemiology, geographical distribution and pathogenicity of D. cervi. Histological examinations were performed on 22 formalin-fixed lung tissue samples of hunted red deer. Exclusively, D. cervi adults were derived from 15 red deer and confirmed molecularly (GenBank accession: MH183394). Dictyocaulus cervi infection was associated with various degrees of lung pathology, including interstitial pneumonia, bronchitis and bronchiolitis with an influx of eosinophils, lymphocytes, plasma cells and macrophages; massive hyperplasia of lymphoid follicles within bronchiolar tissue, and hyperplasia of the bronchial and bronchiolar epithelium. Furthermore, emphysema, atelectasis and lung tissue congestion were noted. Interestingly, interstitial and subpleural fibrosis was seen in adult Dictyocaulus-negative samples, suggesting either a prepatent phase of Dictyocaulus infection or infection/coinfection with protostrongylid nematodes.

Expansion of Ashworthius sidemi in red deer and roe deer from the Lower Silesian Wilderness and its impact on infection with other gastrointestinal nematodes

Nematodes Ashworthius sidemi are typical parasites of Asiatic cervids, mostly sika deer (Cervus nippon). Migrating red deer have probably introduced this parasite to the area of Poland from neighbouring countries. The aim of the study was to determine prevalence and intensity of infection of red deer and roe deer from the Lower Silesian Wilderness with A. sidemi after one year from previous studies and to examine the influence of these parasites on other species of gastrointestinal nematodes. 31 abomasa of red deer and 3 abomasa of roe deer from Forest Dictrict of Ruszów have been examined on the presence of parasites. In comparison with previous studies, red deer showed significant, over triple increase of prevalence of A. sidemi and over fivefold increase of mean intensity of infection. Maximum intensity of infection has increased over 24 times. These results indicate on dynamic spread of this new aswortiosis foci. Apart from previously registered parasite species, four new nematodes have been found in examined red deer and roe deer during this year studies. Red deer have been infected with Spiculopteragia assymmetrica, typical for fallow deer and Haemonchus placei - typical for bovine, whereas roe deer have been infected with Trichostrongylus axei and Trichostrongylus capricola, parasites of sheep, goats and bovine. Prevalence of red deer infection with nematodes S. boehmi and Ostertagia leptospicularis was lower than two years ago while prevalence of infection with S. mathevossiani and O. kolchida was higher. Intensity of infection with these nematodes has increased.

The first report of Aelurostrongylus falciformis (Schlegel, 1933) (Nematoda, Metastrongyloidea) in badger (Meles meles) in Poland

Aelurostrongylus falciformis belongs to the superfamily of Metastrongyloidea. This nematode occurs in European badgers and locates in lungs, in respiratory tract. Numerous species of land snails are intermediate hosts of the parasite. In 2015, parasitological necropsy of 9 badgers, shot in the Forest District Głęboki Bród in Augustowska Primeval Forest, was performed. Two examined animals were infected with nematodes A. falciformis. In the lungs of each badger two specimens of nematodes were detected (male and female). In the following article, description, morphometrical data and figures are presented. This is the first report of A. falciformis infection in badgers in Poland.

Endoparasites of Eurasian lynx (Lynx lynx) (Linnaeus, 1758) from an enclosure of Western Pomeranian Nature Society in Jablonowo

The aim of this study was to describe parasites of three lynx living in an enclosure of Western Pomeranian Nature Society in Jablonowo. During analysis of 3 gram faecal samples eggs of Toxascaris leonina, Toxocara cati, Ancylostoma sp. and oocysts of Cystoisospora felis were found. To our knowledge this is the first report of C. felis infection in lynx from Poland. Presented research show that wild cats in captivity are particularly exposed on parasitic infections and demand regular examination.

Interrelationships of Dictyocaulus spp. in Wild Ruminants with Morphological Description of Dictyocaulus cervi n. sp. (Nematoda: Trichostrongyloidea) from Red Deer, Cervus elaphus

Lungworms from the genus Dictyocaulus cause parasitic bronchitis (dictyocaulosis) characterized by coughing and severe lung pathology in both domestic and wild ruminants. In this study we investigated the interrelationships of Dictyocaulus spp. from European bison (Bison bonasus L.), roe deer (Capreolus capreolus), and red deer (Cervus elaphus) by nucleotide sequence analysis spanning the 18S RNA gene (small subunit [SSU]) and internal transcribed spacer 2 (ITS2) regions of the ribosomal gene array as well as the mitochondrial cytochrome c oxidase subunit 1 (cox1). Molecular analyses of sequence data obtained partly with novel primers from between 10 and 50 specimens from each host were carried out. Bayesian inference analysis revealed that each host species was infected with different genotypes. Analysis of cox1 sequence data showed a diverse genetic background and high evolutionary potential of Dictyocaulus taxa. Data from lungworms of European bison revealed a distinct genotype of Dictyocaulus viviparus, whereas Dictyocaulus capreolus was only found in roe deer. In contrast, red deer were infected with a taxon with unique SSU, ITS2, and cox1 sequences. These results indicate the occurrence of a novel genotype from red deer, which differs significantly from the National Center for Biotechnology Information reference sequence of Dictyocaulus eckerti. The molecular evidence was consistent with a morphological study with description and imaging of Dictyocaulus cervi n. sp. recovered from red deer. Dictyocaulus cervi n. sp. can be distinguished from D. eckerti on the basis of the absence of cervical papillae, the occurrence of a single ring of 4 symmetrical submedian cephalic papillae, length of the tail in females, morphometry of the female reproductive system, and measurements of gubernacula in males. In conclusion, our findings further strengthen the idea that the genetic complexity and diversity among Dictyocaulus lungworms infecting wildlife ruminants is larger than previously believed and warrants further investigation.

A new occurrence of Eimeria catubrina (Apicomplexa: Eimeridae) in elk (Alces alces) from the Kampinos Forest

A three-year-old elk was necropsied in Kampinos Forest, near the village of Granica. An analysis of a 3g faecal sample from the animal revealed the presence of 130 oocysts of Eimeria catubrina. The parasite is typical of roe deer; this study is only the second reported observation of E. catubrina in elks. As coccidia are so rarely found in elks, this observation of E. catubrina in this new localization is a matter of concern.

A massive invasion of Parafasciolopsis fasciolaemorpha in elk (Alces alces) in Lublin Province, Poland

Liver fluke Parafasciolopsis fasciolaemorpha is a parasite typical of elk (Alces alces). The present study describes the identification of a massive invasion of the liver fluke P. fasciolaemorpha in an elk in the Sobibór Landscape Park, Eastern Poland. In February 2016, samples of liver and faeces were collected from the elk during postmorte examination. A section of liver tissue and three grams of faeces were examined for the presence of flukes or fluke eggs by decantation. In total, 11,150 juvenile and mature flukes of P. fasciolaemorpha were found in the examined liver. Multiple cavities with distinct walls, filled with dark liquid, trematodes, fluke eggs and cellular detritus were seen in the cross section of the parenchyma. Additionally, some of the bile ducts were plugged with calcerous deposits. The three grams of examined faeces were found to contain 322 grey and golden-coloured eggs of P. fasciolaemorpha. The presence of such a massive infection of P. fasciolaemorpha in the examined elk has a significant impact on the health of the individual. We can assume P. fasciolaemorpha has a significant influence on the health and abundance of the entire elk population in Poland.

KEY WORDS

Parafasciolopsis fasciolaemorpha, elk, Sobibór Landscape Park, Poland.

Internal parasitic fauna of elk (Alces alces) in Poland

The abundance of elk (Alces alces) in Poland at the beginning of 2016 reached over 28 000 individual animals. However, little is still known about health status of elk population in the country. In particular, important health issue tend to be parasitic diseases which are the most common diseases in wild animals. Special emphasis should be given to the parasitofauna of elks. Their ability to move over great distances increases the chance of parasitic infestations in new areas and transmission to other wild animals and livestock. The aim of this article is to describe the parasites occurring in elk in Poland on the basis of previous studies from the country and to compare them with data from neighboring countries. The presented review reveals that elk populations have not been examined for the presence of parasites for decades, and no recent studies in Poland have examined the parasitofauna of this animal. As such, our study shows that assessing the parasites present in elk populations remains an important area of research.

MHC, parasites and antler development in red deer: no support for the Hamilton & Zuk hypothesis

The Hamilton-Zuk hypothesis proposes that the genetic benefits of preferences for elaborated secondary sexual traits have their origins in the arms race between hosts and parasites, which maintains genetic variance in parasite resistance. Infection, in turn, can be reflected in the expression of costly sexual ornaments. However, the link between immune genes, infection and the expression of secondary sexual traits has rarely been investigated. Here, we explored whether the presence and identity of functional variants (supertypes) of the highly polymorphic major histocompatibility complex (MHC), which is responsible for the recognition of parasites, predict the load of lung and gut parasites and antler development in the red deer (Cervus elaphus). While we found MHC supertypes to be associated with infection by a number of parasite species, including debilitating lung nematodes, we did not find support for the Hamilton-Zuk hypothesis. On the contrary, we found that lung nematode load was positively associated with antler development. We also found that the supertypes that were associated with resistance to certain parasites at the same time cause susceptibility to others. Such trade-offs may undermine the potential genetic benefits of mate choice for resistant partners.

The infection of reintroduced ruminants - Bison bonasus and Alces alces - with Anaplasma phagocytophilum in northern Poland

The north-eastern part of Poland is considered an area of high risk for infection with tick-borne diseases, including with human granulocytic ehrlichiosis (HGE) agents. The etiological agent of HGE is Anaplasma phagocytophilum. As the animal reservoir for A. phagocytophilum in the environment serve the species from Cervidae and Bovidae families. European bison (Bison bonasus) and elk (Alces alces) are the big ruminant species, reintroduced to the forests of Middle Europe after many decades of absence. In the foci of zoonotic diseases they are able to play a role as natural reservoir to pathogens, however, their status as protected animals means their study has been rare and fragmentary. The studies of B. bonasus were conducted in Białowieża Primeval Forest and A. alces in Biebrza National Park. PCR amplifications were performed using primers amplifing the end of the groES gene, the intergenic spacer and approximately two-thirds of the groEL gene in the first round, and primers that span a 395-bp region of the groEL gene were used in the second round. The positive results were obtained in B. bonasus and A. alces, the prevalence of infection was 66.7 and 20.0%, respectively. Randomly selected samples were sequenced, sequences were compared with GenBank entries using Blast N2.2.13 and determined as A. phagocytophilum. The results presented herein are the first record of the presence of Anaplasma phagocytophilum in A. alces, and at the same time confirm the previous observations regarding the infection of B. bonasus with A. phagocytophilum.

Molecular characterization of Fascioloides magna (Trematoda: Fasciolidae) from south-western Poland based on mitochondrial markers

The giant liver fluke, Fascioloides magna, is a veterinary important liver parasite of free living and domestic ruminants. This originally North American parasite was introduced along with its cervid hosts to Europe where it has established three permanent natural foci - in northern Italy, central and southern parts of the Czech Republic and the Danube floodplain forests. The first record on fascioloidosis in Poland originated from the Lower Silesian Forest in south-western Poland and since then an occurrence of F. magna in this country has not been documented. Recently, the parasitological examination of red deer (Cervus elaphus elaphus) from the Lower Silesian Wilderness (south-western Poland) revealed the presence of F. magna eggs. In order to determine the genetic interrelationships of the Polish giant liver fluke individuals, they were molecularly analyzed by mitochondrial cytochrome c oxidase subunit I (cox1) and nicotinamide dehydrogenase subunit I (nad1) and compared with haplotypes of so far studied European populations of the parasite. The study revealed the genetic uniformity of F. magna specimens from Poland with part of individuals from the Czech natural focus. Note: Nucleotide sequence data reported in this paper are available in the GenBank, EMBL and DDBJ databases under the accession numbers KP635008-9.

Extension of occurrence area of the American fluke Fascioloides magna in south-western Poland

Liver fluke Fascioloides magna is a typical parasite of American cervids. The reason for F. magna to appear in Poland territory was bringing the American wapiti deer to those forests around 1850. Along with these deer the aforementioned fluke was also introduced. The aim of this study was to present the case of finding of this species in cervids in Bory Zielonogórskie. Samples of deer feces were collected in February 2015 in Forest District Krzystkowice. A total of 16 samples of feces were examined, 7 of which came from the red deer, 4 from roe deer and 2 samples from fallow deer. Three grams of feces from each sample were examined for the presence of trematode eggs using the decantation method. Eggs of F. magna were detected in 2 of 7 examined samples from red deer, in the first sample it were found 3 eggs, and in the second one 46 eggs. Moreover, flukes eggs were found in 3 out of 4 roe deer faecal samples, in numbers of 1, 3 and 58 eggs respectively in each sample. Also, in faecal samples from two fallow deer were found in one of them 17 eggs F. magna. The results of this study extend the range of occurrence of the trematodes F. magna on the neighboring Lower Silesia Forest complex of Bory Zielonogórskie which are distant about 50 km. Fallow deer and roe deer were considered to be new in Poland definitive hosts of F. magna. .

Coccidia (Apicomplexa: Eimeriidae) of the lowland European bison Bison bonasus bonasus (L.)

Coprological studies conducted between 2007 and 2011 in free-roaming and captive European bison Bison bonasus (Linnaeus, 1758) from Poland revealed 11 species of Eimeria infecting the host, i.e., Eimeria alabamensis, Eimeria auburnensis, Eimeria bovis, Eimeria brasiliensis, Eimeria bukidnonensis, Eimeria canadensis, Eimeria cylindrica, Eimeria ellipsoidalis, Eimeria pellita, Eimeria subspherica, and Eimeria zuernii. The typical host for all isolated species is cattle. The most prevalent species was E. bovis (29.7%), while E. brasiliensis was the rarest (0.5%). Five of the species (E. bovis, E. bukidnonensis, E. canadensis, E. ellipsoidalis, E. zuernii) have been observed previously in bison by other authors, 3 species were noticed by us in bison previously (E. alabamensis, E. cylindrica, E. pellita), while for 3 species (E. auburnensis, E. brasiliensis, and E. subspherica) these are new host and locality records. Oocysts of two species (E. brasiliensis, E. bukidnonensis) were noted only in the feces of bison kept in captivity. Moreover, the prevalence of positive samples was higher in the group of captive animals (55.4%) in comparison with the free-roaming herds (29.5%); although, oocysts per gram (OPG), counted with the conventional McMaster technique, was comparable in both groups, reaching maximally 6550 and 6400 in free-roaming and captive individuals, respectively. Overall, 142 fecal samples from 424 samples examined were positive for Eimeria (prevalence=33.5%). Age-related analysis revealed a higher percentage of Eimeria spp. positive samples and higher OPG values in bison under 1 year old as compared to older individuals (93.3% and 50-4050; 37.3% and 50-550, respectively). Additionally, greater eimerian species diversity was present among calves in comparison with older bison. In most cases single-species infections were observed (59.8%) with a predominance of E. bovis (85.9%). Multiple-species infections consisted of 2-7 species, usually including E. bovis. The observation was made that E. bovis infection appears conducive to the host acquiring more eimerian species. No symptoms of clinical coccidiosis occurred during the study.

The prevalence and distribution of Dirofilaria repens in dogs in the Mazovian Province of central-eastern Poland

The aim of this study was to determine the prevalence and distribution of canine dirofilariosis from different districts of the Mazovian Province in central-eastern Poland. 462 dogs aged from 1.5-14 years were examined for dirofilariosis. Blood samples were examined for the presence of microfilariae using the Knott method, as well as the method of Kingston and Morton, after centrifugation in haematocrit microtubes in order to determine the intensity of infection as the number of microfilariae in 60 microliters of blood. The species of microfilariae found were determined after staining on the basis of the morphological characters. Samples were also examined using Canine Heartworm Antigen Test Kit SNAP HTWM (IDEXX, USA) that allows the detection of circulating antigens of females of Dirofilaria immitis. The positive samples were examined using multiplex PCR assay for species confirmation. Microfilariae belonging to the species D. repens were found in the blood samples of dogs originating from the city of Warsaw and from 18 districts of Mazovian Province. The mean prevalence of that species observed in the province was 25.8%. The range of intensity counted with the number of microfilariae found in 60 microliters of blood amounted to between 1-150; median intensity 9 microfilariae. The highest prevalence, reaching 52.9% and the highest median intensity of infection reaching 28 microfilariae, was found in Radom district. The lowest prevalence, amounting to 4.2%, was registered in Grójec district; however, the lowest median intensity reaching 6 microfilariae was noted in Żyrardów district. The infected dogs had not been outside of Poland, which means that this is an autochthonous infection. Microfilariae and antigens of D. immitis were not found in any examined blood samples. Results of the presented study show that autochthonous dirofilariosis caused by nematodes D. repens commonly occurs in the area of the Mazovian Province.

A new occurrence of Eimeria alces (Apicomplexa: Eimeridae) in elk (Alces alces) in East Poland

A total of 114 elk faecal samples from the Polesie National Park and adjacent forest districts were examined in 2013 and 2014. Three samples were positive. The positive samples were from the village of Wereszczyn, the Sobibor forest district, and the Polesie National Park and Forest district, Parczew. Morphometric examination revealed that the oocysts belong to the species Eimeria alces. This is the second identification of the parasite in elk in Poland and the fifth worldwide.

Migrations and the introduction of wild ruminants as a source of parasite exchange and emergence of new parasitoses

The relationship between European bison and cervidae is a good model for studies on the influence of migration and introduction of new species on the helmhninthofauna of wild ruminants and the occurrence of new parasitoses. Changes in the helminthofauna of bison and deer under the influence of changes in the environment and living conditions, as well as the introduction and migration of other species, are discussed in detail. The exchange of helminths between bison, cervids and domestic ruminants is demonstrated. Examples of helminth introduction from specific Cervidae species, the formation of the new host-parasite systems and the appearance of new parasitoses are also presented.

Dirofilaria repens Railliet et Henry, 1911--a new parasite acclimatized in Poland

Dirofilariosis caused by the Dirofilaria repens nematodes is widely dispersed in southern Europe, Asia and Africa among dogs, cats, other carnivores and occasionally, humans. The first case of D. repens infection, found in Poland in 2007, concerned humans. In 2009, dirofilariosis was first registered in dogs in 3 focuses in central Poland, Warsaw, Pruszków and Zyrardów, whose range grew considerably with the subsequent identification of D. repens microfilariae in 119 dogs in Warsaw and 18 districts of the Mazowieckie Province. The microfilariae of D. repens were found in blood samples taken from 1588 dogs from all 16 provinces of Poland. D. repens was also recently detected in a mixture of Culex pipiens and Aedes vexans mosquitoes collected in Mazowieckie Province using Real Time PCR. The results of this study confirms the acclimatisation of D. repens on the territory of Poland and a possibility for it to close its life cycle in domestic species of mosquito.

Coccidia (Apicomplexa: Eimeriidae) of elk (Alces alces) in Poland

Over a 4-year period, we analyzed 128 fecal samples from free-living elk (Alces alces L., 1758) to determine the prevalence of Eimeria infections and identify the species present. Two eimerian species were isolated including Eimeria alces and a morphotype resembling Eimeria catubrina. Overall, two samples from 128 samples collected were positive for Eimeria (prevalence = 1.6 %), and the oocyst per gram, estimated with the use of the conventional McMaster quantitative technique, ranged from 50 to 100. Also, E. alces has been found in Lithuania and Belarus and is the only known species of eimerian to infect elk. E. catubrina is a parasite typically infecting roe deer (Capreolus capreolus L., 1758). This is the first report of Eimeria spp. in elk in Poland. Results of our investigation indicate that elk may become infected with an eimerian species that is typical for roe deer, but this requires further investigation.

Nematodes of the large intestine of the European bison of the Białowieza National Park

The present study was conducted on 31 males and females of the European bison, eliminated during the winter seasons 2007-2011 in the Białowieza Primeval Forest, Poland. The caeca of 14 free-ranging bison, aged from 3 months up to 16 years, the most favorable infection site for the large intestine nematodes, were investigated during the winter of 2007/2008. The parasitological autopsies of the large intestines of 9 free-ranging bison aged from 5 months up to 10 years as well as 9 bison kept in the close reserves aged from one up to 20 years were done during the winter seasons of 2008-2011 to determine localization of nematodes in large intestine and the total intensity of parasite infection. Five species of nematodes (i.e., Trichuris ovis, Oesophagostomum venulosum, O. radiatum, Ashworthius sidemi, Nematodirus helvetianus) were found in dissected caecum of bison culled during the winter of 2007/2008. During the seasons of 2008-2010, 6 species of nematodes were found in the large intestine of bison (i.e., T. ovis, O. venulosum, O. radiatum, A. sidemi, N. roscidus and Bunostomum trigonocephalum). We did not find any nematodes in the lumen of the large intestine of captive bison culled during the seasons of 2010/2011. The results of the present study indicate that the intensity of infection by the large intestine nematodes of the European bison in the Białowieza Primeval Forest has stayed at the comparable level throughout the last 20 years; however the number of nematode species has increased. The observed level of parasitic infection is typical of subclinical parasitoses.

The annual cycle of shedding Eimeria oocysts by European bison (Bison bonasus) in the Bialowieza Primeval Forest, Poland

Between April 2008 and March 2009, we analyzed the pattern of coccidian oocysts present in the feces of the European bison (Bison bonasus L., 1758) and found 4 species (Eimeria bovis , E. canadensis, E. ellipsoidalis, E. zuernii) previously reported from this host and 3 species (Eimeria alabamensis, E. cylindrica, E. pellita) that are new host and locality records. All the species occurred in bison females, and only 4 occurred in males; E. bovis was the most prevalent in both sexes. The overall prevalence of Eimeria spp. invasion reached 34.7% in cows and 13.9% in bulls. The highest prevalence was noted in early spring, with a peak in April, and the lowest in late autumn and winter. The oocyst count per gram of feces (OPG) varied from 50 to 1,350; no symptoms of clinical coccidiosis were observed. We found a significant influence of winter aggregations of bison on shedding of coccidian oocysts. The prevalence and OPG values were higher in bison congregating in large numbers around winter-feeding sites in comparison to other sites. We suggest that the coming together of cows during the growing season impacts the gender-related differences in prevalence and the number of coccidian species involved. This observation probably results from an increased production of oocysts by sub-clinically infected individuals in high-density bison populations.

Pathological lesions in European bison (Bison bonasus) with infestation by Ashworthius sidemi (Nematoda, Trichostrongylidae)

Asworthius sidemi Schulz, 1933 is a blood sucking gastrointestinal nematode, primarily typical for Asiatic deer. It was found for the first time in Poland in European bison in 1997. To estimate the level of invasion of A. sidemi and histopathological changes connected with the presence of the parasite in the years 2004-2007 parasitological and histopathological examinations of 54 European bison from Białowieza Forest were carried out. Parasitological examination was carried out by the sedimentation method and A. sidemi were diagnosed under a binocular microscope. Samples for histological examination were collected from the abomasum and duodenum walls as well as from regional lymph nodes. Tissue samples were then fixed with 10% buffered formalin, embedded in paraffin, cut in to 5 microm thick sections and stained with hematoxylin and eosin (H&E). Parasitological examinations showed the presence of fourth stage larvae and juvenile forms of A. sidemi. The maximal intensity of invasion rose systematically from 4470 A. sidemi nematodes in 2004/2005 to 44310 in 2006/2007. Histopathological examinations showed infiltrations of inflammatory cells in the walls of abomasa and duodena at various levels of intensity (mainly lymphoid cells and eosinophils), hyperemiae, oedemae and lesions of mucosa and proliferation of lymphatic follicles. In individual cases of dysplasia of epithelial cells, atrophy or hyperplasia of glands and the presence of parasites in the lumen or walls of the abomasum/duodenum were observed. In one case, parasitic nodules were found. In regional lymph nodes proliferation of lymphatic follicles, presence of eosinophils and desolation of reproduction centers were observed. Intensification of histopathological changes was connected to a considerable degree with the developmental stage of A. sidemi as shown by parasitological examination.

[The way of penetration of first stage larvae of Elaphostrongylus cervi (Nematoda, Protostrongylidae) to the intermediate host and their development to the invasive stage]

The aim of the study was the way of penetration of the first stage larvae of Elaphostrongylus cervi to the intermediate host and their development to the invasive stage. The first stage larvae of E. cervi penetrate to the body of a snail by the epithelium of its foot, and localise in tissue of muscles. The period of their development to the second stage is 7 to 9 days, and to the third stage is 21 to 28 days.

[An attempt of experimental infection of fishes and chickens with invasive larvae of Elaphostrongylus cervi (Nematoda, Protostrongylidae)]

Elaphostrongylus cervi is a parasite of skeletal muscles and central nervous system of wild and farm red deer in Europe and Asia. Numerous species of terrestrial snails can be its intermediate hosts. Considering the fact that invasive larvae of E. cervi are released by deer to the external environment in huge numbers, fishes and birds can be accidentally infect by them. In this study the development of larvae E. cervi in those nonspecific hosts was discussed. It was determined that invasive larvae of E. cervi in the digestive tract of fish do not penetrate the intestinal wall, do not develop any further, and are probably digested. Similarly, those larvae given to chicken are also incapable of breaking the gut barrier and are digested. In all infected animals, the phenomenon of parathenia has not been observed and the meat of the animals studied poses not threat to humans.

[The first foci of dirofilariosis of dogs evoked by Dirofilaria repens Railliet et Henry, 1911 in central Poland]

Dirofilariosis is caused by nematodes Dirofilaria repens Railliet et Henry, 1911. This parasitosis is widely distributed in south Europe among dogs, cats and wild carnivorous. It occurs also in Asia and Africa. Adult nematodes D. repens locate in nodules, in subcutaneous or intramuscular connective tissue of dogs. The mosquitoes from genera Anopheles, Aedes and Culex are the intermediate hosts and vectors of mentioned parasites. The finding of 6 adult nematodes belonging to the species D. repens in scrotum under tunica vaginalis, during the castration of the dog, which has never been abroad, tended us to undertake presented studies. In August and September of 2009, 64 genuine dogs age from 1.5 to 12 years originated from 3 kennels in central Poland were examined. Dogs did not show any pathological symptoms of infection. Blood samples were examined for the presence of infection and a number of microfilariae. Species of microfilariae was determined after staining on the basis of morphological characters. In examined blood samples from dogs microfilariae belonging to the species Dirofilaria repens were found. Mean prevalence of infection in all examined kennels was 37.5% and mean intensity 32 microfilariae in 30 microl of blood. Microfilariae of D. immitis were not found in any examined blood samples. The results of presented studies show that native dirofilariosis of dogs caused by D. repens is common in central Poland. The result of our investigations lets us suppose, that the range of occurrence of D. repens will spread significantly towards north Europe.

[Sarcocystis cruzi (Protozoa: Apicomplexa: Sarcocystiidae) infection in european bison (Bison bonasus) from Białowieza Forest, Poland]

Samples of oesophagus, diaphragm and heart muscles were taken from one European bison from Białowieza Forest during seasonal European bison elimination in 2008. Five gram of each muscle was examined by staining small samples in 0.2% aqueous solution of methylene blue. After that they were placed between compressor glasses and examined under a dissecting microscope in order to detect Sarcocystis sp. infection. All sarcocysts observed were counted. The 5-g sample of the heart muscle yielded a total of 756 sarcocysts while that of the diaphragm contained 107 of them and that of the oesophagus--89. All of the sarcocysts were isolated from 1 g of each muscle by using preparation needles (probes). After that the sarcocysts were taken to 0.5% physiological solution and examined under light microscope. The special attention was paid to detection of their cyst wall, which was thin (1 microm up to 1.2 microm) and smooth in all cases. Sometimes villar protrusions were seen on the surface of the cysts. Differences between the size of sarcocysts isolated from different muscle samples were observed. The longest and the slenderest sarcocysts were found in the diaphragm. Slightly smaller in the oesophagus and the smallest ones in the heart muscle tissue. The average size of sarcocysts isolated from diaphragm was 957.6 microm x 112.7 microm. Sarcocysts found in the oesophagus measured 484.1 microm x 194.6 microm and those isolated from the heart muscle attained 305.4 microm x 103.9 microm. All of the sarcocysts isolated from heart, oesophagus and diaphragm muscles were identified Sarcocystis cruzi.

Ashworthius sidemi (Nematoda, Trichostrongylidae) in wild ruminants in Białowieza Forest

Between 2003-2007, abomasa of 91 European bison (Bison bonasus), 4 red deer (Cervus elaphus) and 2 roe deer (Capreolus capreolus) shot in the Białowieza Primeval Forest (Poland) were examined for worms presence. All the animals examined were infected with nematodes A. sidemi with an exception of one bison, that was shot in year 2003. There was much higher average intensity of invasion in bison (5529), than in red deer (85) and in roe deer (1837). The animals were shot in a period from December to March, and the nematodes found in them were fourth stage larvae and immature adult specimens. In the following years of examinations, a gradual increase in average intensity of infection was observed. In 2007, it reached in bison 10814 nematodes. Maximum intensity of invasion was found in this year as well and it reached 44310 nematodes in one bison. Pathological changes such as an oedema, hyperaemia and effusion in the abomasum and duodenum mucosa were most clearly seen in the calves that were highly infected. These changes probably lead to chronic diarrhoea, deterioration and deaths of young animals.

[Occurrence of coccidia from genus Eimeria in European bison in Białowieza Forest, Poland]

Protozoa from the genus Eimeria belong to the least recognized parasites of the European bison. There are only a few data concerning the infection of the bison by these protozoa in Białowieza Forest. In the winter of 2007/2008 weighting 3 g fecal samples from the rectum of 16 shot bison were examined by flotation method. In 13 of them were found coccidian oocysts from genus Eimeria, which were determined to the species by morphometric study under the microscope. In all 13 positive samples, it is 81.2%, oocysts of Eimeria bovis were found. Intensiveness of this infection oscillated from 1 to 181 and the mean one was 38 oocysts. E. zuernii was found in 9 samples in the mean intensity 19 (1-154) oocysts. E. ellipsoidalis occurred in 3 bison with a very low intensity 1 to 3 oocysts. The most rarely occurred E. canadiensis, only in 2 examined bison in the number of 2 and 3 oocysts. All found coccidian species are the typical parasites of cattle. Białowieza Forest is a new place of occurrence of these parasites. European bison is a new host for E. zuernii.

[Determination of limits of ashworthiosis foci in eastern and southern Poland]

The task was to establish the foci of ashworthiosis. The locations were: Białowieza Forest and Bieszczady Mountains. The wild cervides including: 52 red deer and 15 roe deer as well as domestic ruminants: 17 cattle and 18 sheep were examined parasitologically. Also, the examination was extended to neighbouring and additional areas. Contents of abomasa after multiple decantation were conserved with 2% formaldehyde. All nematodes were isolated from the contest, cleared in 70% ethanol with 5% glycerol and determinated to the species on the basis of structure of bursa copulatrix. Intensity of invasions of red deer oscillated from 3 to 296 specimens of A. sidemi and of roe deer from 42 to 545 nematodes. There were found none of domestic ruminants infected with this nematode in areas neighbouring with woods in both foci. Examinations showed that relatively new (found in 2000 year) focus of ashworthiosis in Polish part of Białowieza Forest has not dispersed yet beyond the limits of this forest complex. However, focus of ashworthiosis found in Bieszczady Mountains in 1997 year initially in Lutowiska Forest District expanded on the area of neighbouring Bieszczady forest districts: Komańcza, Cisna and Baligród and also on the area of Forest District Krasiczyn lying in Pogórze Przemyskie. So it is necessary further monitoring of status of A. sidemi infection of wild and domestic ruminants in neighbouring of both till now found foci.

[Increase of infection of European bison by nematodes Setaria labiatopapillosa in Białowie a Forest]

BACKGROUND

The aim of these studies was to determine the level of infection of European bison by nematodes belonging to the genus Setaria.

MATERIAL AND METHODS

From February 2006 to February 2007 21 bisons from 6 months to 20 years old shot in Białowieza Forest have been examined. During the necropsy pleural and peritoneal cavities were macroscopically examined for the presence of nematodes. The parasites were removed from tissues and fixed in 70% ethanol with 5% addition of glycerol and then identified to the species. Samples of blood were taken from shot bison and after centrifugation in microhaematocrit tubes directly examined to confirm the infection.

RESULTS

Nematodes Setaria labiatopapillosa were found in 71% of examined bisons. They usually laid freely in peritoneal cavity and sometimes also in pleural one. Accidentally single nematodes were observed in omentum on the surface of omasus and on the surface of liver surrounded by connective tissue. Intensity of bison infection by S. labiatopapillosa varied from 1 up to 24 specimens. Both young and old animals were infected with these nematodes. Observed after 3 years period over 30% rise of prevalence of nematodes S. labiatopapillosa, occurrence of these nematodes in all age groups of this host, and high intensity of infection are alarming. Although these nematodes in their typical localization and low level of infection do not evoke visible symptoms, the pathogenity of this species of nematode is not yet sufficiently recognized, and it is the reason, that monitoring of this infection in bison is necessary.

The first record of Elaphostrongylus alces larvae in moose in Poland and their development to the invasive stage

BACKGROUND

This is the first record of the first stage larvae of Elaphostrongylus alces in moose in Poland.

MATERIAL AND METHODS

The 75 faecal samples (5 g) from moose in Kampinos National Park were examined using Baermann method.

RESULTS

The prevalence of E. alces larvae in feaces samples was 37%. The maximal intensity reached 294 larvae. 20 larvae of the first stage and 27 larvae of the third stage were measured. The comparison of their dimensions with the results obtained by Lankester, shows that they represent E. alces.

Expansion of the Asiatic parasite Ashworthius sidemi (Nematoda, Trichostrongylidae) in wild ruminants in Polish territory

The abomasa of 40 wild ruminants (18 red deer, 9 roe deer, 13 European bison) shot in the Bieszczady Mountains and another 8 European bison shot in Bialowieza Primeval Forest, were examined for worms. Ashworthius sidemi was found in all of the animals from the Bieszczady Mountains, and the intensity of infection was usually massive. In Bialowieza Forest few specimens of A. sidemi were noted among three bison. Wild ruminants were infected by A. sidemi from June to September. The nematodes originating from this infection only attained sexual maturity in June of the following year, and from September the process of expelling the parasites of that generation began. From June to autumn, two generations of nematodes, one consisting of mature individuals from the previous year and the other of the current year comprising fourth stage larvae as well as juveniles, occur in these hosts. In the winter and spring periods until June, only one generation of the parasite, arrested fourth-stage larvae and juveniles, occurs in the hosts.