Biomedical subjects

Michal Stanko

Publications and source records attributed to Michal Stanko.

13 recordsLinked to original sources

PubMed2006

Prevalence of Borrelia burgdorferi s.l. OspA types in Ixodes ricinus ticks from selected localities in Slovakia and Poland.

In this study, 746 questing Ixodes (I.) ricinus ticks from eastern Slovakia and 187 ticks from southern Poland were investigated for infection with Borrelia (B.) burgdorferi sensu lato and different outer surface protein A (OspA) types by an improved restriction fragment length polymorphism (RFLP) analysis of the ospA gene. The method enables differentiation of both single and multiple infections with B. burgdorferi s.s. (OspA type 1), B. afzelii (OspA type 2), B. garinii (OspA types 3-8), B. valaisiana (subgroups I and II), B. lusitaniae, B. bissettii, and the recently described genospecies A14S. Broad heterogeneity in B. burgdorferi s.l. was found including all species and subtypes except for B. lusitaniae, B. bissettii, and genospecies A14S. Regional prevalence of B. burgdorferi s.l. varied between 8% and 22.5%. The most frequent species were B. garinii (45.4%) and, notably, B. burgdorferi s.s. (31.3%). I. ricinus nymphs harbored almost exclusively B. burgdorferi s.s. and B. garinii OspA type 4, while in adults a broad variety of B. burgdorferi s.l. types was found. Mixed infections were significantly more often in nymphs than in adult ticks. In all mixed infected nymphs, B. burgdorferi s.s. with OspA type 4 was present. These data strongly suggest that B. burgdorferi s.s. and B. garinii OspA type 4 are maintained in these areas by specific transmission cycles involving a so far undetermined vertebrate host which is frequently fed on by I. ricinus larvae. This improved method provides a reliable tool for epidemiological studies on the heterogeneity of B. burgdorferi species and OspA types, an important prerequisite for improved local risk assessment and for test- and vaccine development for Europe.

Animals↗

PubMed2006

Relationship between host abundance and parasite distribution: inferring regulating mechanisms from census data.

1. We studied the effect of host abundance on parasite abundance and prevalence using data on 57 associations of fleas (Siphonaptera) and their mammalian hosts from Slovakia. 2. We assumed that flea-induced host mortality could be inferred from the relationship between flea aggregation and flea abundance, whereas host-induced flea mortality could be inferred from the relationship between flea abundance or aggregation and host abundance. 3. Relationships between flea abundance or prevalence and host abundance were either negative (in 23 flea-host associations) or absent (in 34 flea-host associations). Negative relationships between flea abundance and host abundance were always accompanied by negative relationships between flea prevalence and host abundance. 4. The link between flea abundance/prevalence and host abundance was evaluated as the coefficient of determination of the respective regressions. Across flea-host associations, this link decreased with an increase in the degree of flea aggregation (measured as a parameter b of Taylor's power law). 5. Mean crowding of fleas decreased with an increase of host abundance in eight flea-host associations, being asymptotic in four of them. On the other hand, mean crowding of fleas increased with an increase in flea abundance in 49 flea-host associations, being asymptotic in 15 of them. 6. Results of this study suggest that different flea-host associations are governed by different regulating mechanisms, but different regulation mechanisms may act simultaneously within the same flea-host associations.

Animals↗

PubMed2006

Are ectoparasite communities structured? Species co-occurrence, temporal variation and null models.

1. We studied temporal variation in the structure of flea communities on small mammalian hosts from eastern Slovakia using null models. We asked (a) whether flea co-occurrences in infracommunities (in the individual hosts) in different hosts as well as in the component communities (in the host species) demonstrate a non-random pattern; (b) whether this pattern is indicative of either positive or negative flea species interactions; (c) whether this pattern varies temporally; and (d) whether the expression of this pattern is related to population size of either fleas or hosts or both. 2. We constructed a presence/absence matrix of flea species for each temporal sample of a host species and calculated four metrics of co-occurrence, namely the C-score, the number of checkerboard species pairs, the number of species combinations and the variance ratio (V-ratio). Then we compared these metrics with the respective indices calculated for 5000 null matrices that were assembled randomly using two algorithms, namely fixed-fixed (FF) and fixed-equiprobable (FE). 3. Most co-occurrence metrics calculated for real data did not differ significantly from the metrics calculated for simulated matrices using the FF algorithm. However, the indices observed for 42 of 75 presence/absence matrices differed significantly from the null expectations for the FE models. Non-randomness was detected mainly by the C-score and V-ratio metrics. In all cases, the direction of non-randomness was the same, namely the aggregation, not competition, of flea species in host individuals and host species. 4. The inclusion or exclusion of the uninfested hosts in the FE models did not affect the results for individual host species. However, exclusion of the uninfested host species led to the acceptance of the null hypothesis for only six of 13 temporal samples of the component flea communities for which non-randomness was detected when the uninfested hosts were included in the analysis. 5. In most host species, the absolute values of the standardized size effect of both the C-score and V-ratio increased with an increase in host density and a concomitant decrease in flea abundance and prevalence. 6. Results of this study demonstrated that (a) flea assemblages on small mammalian hosts were structured at some times, whereas they appeared to be randomly assembled at other times; (b) whenever non-randomness of flea co-occurrences was detected, it suggested aggregation but never segregation of flea species in host individuals or populations; and (c) the expression of structure in flea assemblages depended on the level of density of both fleas and hosts.

Animals↗

PubMed2006

Age-dependent flea (Siphonaptera) parasitism in rodents: a host's life history matters.

We studied age-dependent patterns of flea infestation in 7 species of rodents from Slovakia (Apodemus agrarius, A. flavicollis, A. sylvaticus, A. uralensis, Clethrionomys glareolus, Microtus arvalis, and M. subterraneus). We estimated the age of the host from its body mass and expected the host age-dependent pattern of flea abundance, the level of aggregation, and prevalence to be in agreement with theoretical predictions. We expected that the mean abundance and the level of aggregation of fleas would be lowest in hosts of smallest and largest size classes and highest in hosts of medium size classes, whereas pattern of variation of prevalence with host age would be either convex or asymptotic. In general, mean abundance and species richness of fleas increased with an increase in host age, although the pressure of flea parasitism in terms of number of fleas per unit host body surface decreased with host age. We found 2 clear patterns of the change in flea aggregation and prevalence with host age. The first pattern demonstrated a peak of flea aggregation and a trough of flea prevalence in animals of middle age classes (Apodemus species and C. glareolus). The second pattern was an increase of both flea aggregation and flea prevalence with host age (both Microtus species). Consequently, we did not find unequivocal evidence for the main role of either parasite-induced host mortality or acquired resistance in host age-dependent pattern of flea parasitism. Our results suggest that this pattern can be generated by various processes and is strongly affected by natural history parameters of a host species such as dispersal pattern, spatial distribution, and structure of shelters.

Age Factors↗

PubMed2006

Climate and environmental factors influencing Echinococcus multilocularis occurrence in the Slovak Republic.

During the period of 2000-2004, 3,096 red foxes from the whole territory of the Slovak Republic were sampled and examined parasitologically for infections with Echinococcus multilocularis, causative agent of serious alveolar echinococcosis in humans. Relations between prevalence of the parasite in individual regions of Slovakia and some environmental factors were weighted. During the study period, great differences of prevalence and infection intensity were found on a regional level and significant between-year fluctuation of both parameters was observed. High-endemic foci with an estimated prevalence of more than 30 % were detected in the northern and central part of the country. Climatic conditions, including low mean annual air temperature, high mean annual rainfall and the high humidity of the soil, showed to be important for E. multilocularis distribution. Significant correlation was calculated between prevalence of the tapeworm, mean annual precipitation values, and population density of small mammals.

Animals↗

PubMed2005

Relationships between local and regional species richness in flea communities of small mammalian hosts: saturation and spatial scale.

The number of species coexisting in a community may be regulated by local factors (e.g., competitive interactions), or by regional processes (e.g., dispersal from a regional species pool). The relative importance of local and regional processes can be inferred from the shape of the relationship between local and regional species richness. We investigated this relationship in communities of fleas parasitic on small mammals at two spatial scales: between the richness of fleas on individual hosts (infracommunities) and that of fleas on host populations (component communities), and between the richness of component communities and that of the entire regional species pool. We tested linearity (proportional sampling) versus curvilinearity with an asymptote (species saturation) by plotting "local" against "regional" species richness of fleas either among host species or within host species among populations. At the two spatial scales, we found consistent curvilinear relationships between species richness of the more "local" communities and richness of the more "regional" communities. This was true across all host species in the data set and for geographic subsets, even after controlling for the influence of sampling effort on estimates of species richness, and that of host phylogeny in interspecific analyses. We also tested for density compensation in species-poor communities. There was no strong evidence for density compensation at the infracommunity level, although its existence at the component community level appeared likely. Our results suggest that identical patterns in local-versus-regional species richness observed on two different spatial scales arise via different mechanisms: infracommunities appear saturated with flea species most likely because of local processes, such as host immune defenses, whereas component communities are saturated with species through interspecific competition, possibly among larval stages.

Animals↗

PubMed2005

Distribution of fleas (Siphonaptera) among small mammals: mean abundance predicts prevalence via simple epidemiological model.

We used data on the abundance and distribution of fleas parasitic on small mammals in Slovakia and aimed: (i) to confirm a positive relationship between abundance and distribution fleas within and across host species; and (ii) to test if prevalence of fleas can be reliably predicted from a simple epidemiological model that takes into account flea mean abundance and its variance. Prevalence of a flea species increased with an increase in its mean abundance both within and across host species. We calculated prevalences both for each flea-host association and for each flea species across all hosts. Observed prevalences did not differ significantly from those predicted by the epidemiological model using parameters of Taylor's power relationship between mean abundance of fleas and its variance. Regressions of predicted prevalences against observed prevalences produced slope values that did not differ significantly from unity and were independent of scale (within or across host species). Our results demonstrated that up to 96% of variance in flea prevalence can be explained solely by their mean abundance. We concluded that, in general, there is no need to invoke other, more complex factors for the explanation of the variation in flea prevalence.

Animals↗

PubMed2005

Central European Dobrava Hantavirus isolate from a striped field mouse (Apodemus agrarius).

Dobrava virus (DOBV) is a hantavirus that causes hemorrhagic fever with renal syndrome (HFRS) in Europe. It is hosted by at least two rodent species, Apodemus flavicollis and A. agrarius. According to their natural hosts they form the distinct genetic lineages DOBV-Af and DOBV-Aa, respectively. We have now established a DOBV isolate named Slovakia (SK/Aa) from an A. agrarius animal captured in Slovakia. The complete S and M and partial L segment nucleotide sequences of the new isolate were determined. Phylogenetic analyses showed that the SK/Aa isolate clustered together with the other DOBV-Aa sequences amplified from A. agrarius before and can be taken as the representative of this genetic lineage. SK/Aa, in comparison with a DOBV-Af isolate, was used for serotyping neutralizing antibodies of HFRS patients in Central Europe. Most patients' sera exhibited a higher endpoint titer when probed with our new isolate, suggesting that DOBV-Aa strains are responsible for most of the DOBV-caused HFRS cases in this region.

Animals↗

PubMed2004

Small mammals (Insectivora, Rodentia) as a potential source of chlamydial infection in East Slovakia.

The presence of antibodies against Chlamydophila (Chlamydia) psittaci in small mammals (Insectivora, Rodentia) in the region of East Slovakia are presented. The hosts were caught in several areas of Slovakia in habitats with different levels of anthropogenic disturbance. Research was carried out during 2000-2002. The authors examined 1,947 sera coming from 4 insectivore and 10 rodent species. Each serum was examined by micromethod of complement binding reactions using antigen Chlamydophila (Chlamydia) psittaci. Chlamydial infections were found in 251 individuals (prevalence 12.9 %) of 8 mammal species. The antichlamydial antibodies were proved at levels ranging from 1:32-1:1024. The highest prevalence of antibodies was detected in the most abundant rodent species Apodemus microps (14.8 %), Apodemus agrarius (13.9 %), Apodemus flavicolis (12.4 %), Microtus arvalis (12 %), and Clethrionomys glareolus (10.9 %). Positive hosts were registered in all studied localities. Testing of prevalence values in the individual research years confirmed significant changes. Our results showed that small mammals probably play an important role in the circulation of chlamydiae in nature.

Animals↗

PubMed2004

Anti-Borrelia antibodies in rodents: important hosts in ecology of Lyme disease.

Data presented in this study focuses on the presence of anti-Borrelia antibodies in small mammals from Eastern Slovakia during 2000-2003. The total seropositivity observed was 18.78% in rodents. Amongst all species, the total seroprevalence in Apodemus flavicolis was the highest (20.87%), followed by Apodemus agrarius (19.58%) and Clethrionomys glareolus (11.11%). However, the prevalence in Apodemus flavicolis during the year 2000-2001 was higher (26.72%), which reduced to 10.60% in 2002-2003. To compare the year range of seroprevalence in other small mammals was not feasible due to the small sample number. Area-wise distribution of anti-Borrelia antibodies was even (18.75% to 20%) in this study, except in the Bot'any province (0%). This confirms the equal distribution of Borrelia spirochetes in the other 3 localities. Prevalence of anti-Borrelia antibodies during summer was significantly higher than during autumn and early spring. The overall study also reviews the importance of small mammals in Lyme disease ecology.

Animals↗

PubMed2003

Genetic variability within Borrelia burgdorferi sensu lato genospecies established by PCR-single-strand conformation polymorphism analysis of the rrfA-rrlB intergenic spacer in ixodes ricinus ticks from the Czech Republic.

In Europe the Borrelia burgdorferi sensu lato complex is represented by five distinct genospecies: Borrelia burgdorferi sensu stricto, Borrelia afzelii, Borrelia garinii, Borrelia valaisiana, and Borrelia lusitaniae. These taxonomic entities are known to differ in their specific associations with vertebrate hosts and to provoke distinct clinical manifestations in human patients. However, exceptions to these rules have often been observed, indicating that strains belonging to a single genospecies may be more heterogeneous than expected. It is, therefore, important to develop alternative identification tools which are able to distinguish Borrelia strains not only at the specific level but also at the intraspecific level. DNA from a sample of 370 Ixodes ricinus ticks collected in the Czech Republic was analyzed by PCR for the presence of a approximately 230-bp fragment of the rrfA-rrlB intergenic spacer of Borrelia spp. A total of 20.5% of the ticks were found to be positive. The infecting genospecies were identified by analyzing the amplified products by the restriction fragment length polymorphism (RFLP) method with restriction enzyme MseI and by single-strand conformation polymorphism (SSCP) analysis. The two methods were compared, and PCR-SSCP analysis appeared to be a valuable tool for rapid identification of spirochetes at the intraspecific level, particularly when large samples are examined. Furthermore, by using PCR-SSCP analysis we identified a previously unknown Borrelia genotype, genotype I-77, which would have gone unnoticed if RFLP analysis alone had been used.

Animals↗

PubMed2003

Molecular evidence for Anaplasma phagocytophilum and Borrelia burgdorferi sensu lato in Ixodes ricinus ticks from eastern Slovakia.

Ixodes ricinus ticks (20 males, 20 females and 20 nymphs) collected in Kosice, Slovakia were examined for the presence of Anaplasma phagocytophilum and Borrelia burgdorferi sensu lato (s.l.) by PCR. 38.3 % of the tested ticks carried single infection of B. burgdorferi s.l. and 8.3 % were infected with A. phagocytophilum. Double infection of both pathogens was detected in 5 % of tested ticks. These results indicate that both B. burgdorferi s.l. and A. phagocytophilum co-circulate in the enzootic sites of Eastern Slovakia and may cause co-infection in humans.

Anaplasma phagocytophilum↗

PubMed2002

Seroprevalence of anti-Borrelia burgdorferi antibodies in sheep and goats from mountainous areas of Slovakia.

In the present study, domestic animals such as sheep and goats from eastern Slovakia were screened for the presence of anti-Borrelia antibodies. Seroprevalence in 181 sheep and 65 goats were carried out in 1999 and 2000. Modified ELISA method was used for detection of anti-Borrelia IgG antibodies. Seroprevalence obtained was 15.8% and 17.5% in 1999 and 2000 respectively in sheep, whereas in goats it was 17.2% and 19.4% respectively. The results suggest that these domestic species have potential to transmit the disease to other animals. Though the role of sheep and goats in Lyme disease has not yet been documented, there is great possibility of transmission of the causative agent via co-feeding to human beings.

Animals↗