[Approaches to developing a procedure for mapping water basin regions, by using the parasitological criteria].

The structure of a parasite system is formed and its functioning takes place in qualitatively different environments. The aquatic environment serves as a source of new elements and modules, energy, and information for parasite systems. And the parasite systems, for their part, affect the physical and biological parameters of the environment. Many intestinal infections caused by pathogenic microorganisms generally characterized by an acute disease course are related to a water factor. Such are typhus, typhoids, dysentery, cholera, salmonellosis, virus hepatitis, and others. Many parasitic diseases caused by pathogenic intestinal protistae (lambliasis, amebiasis, balantidiasis), blood parasite protistae (malaria), helminthes (opisthorchiasis, fascioliasis, diphyllobothriasis, cercariosis, pseudoamphistomosis) are also closely related to a water factor. Ascaridiasis, hymenolepiasis, trichocephalosis, and echinococcosis have a less close but still self-evident relationship to a water factor. The clbse relationships of many parasitic diseases to a water factor are also determined by the fact that the life cycles of many parasites necessarily include various intermediate hosts and parasite vectors, such as fishes, mollusks, crustaceans, and insects, which are aquatic organisms at some stages of their life. The results of continuous exposure of people to parasitic diseases are quite similar to the suppressive effects of the environment in the ecologically troublesome regions. The most prognostically useful information is formed while mapping by medical and ecological regions, by employing a combination of current mathematical and cartographical methods. The former include cluster analysis, quartering method, informational logical analysis, which are all described in this article and others. Regional mapping using the parasitological criteria should achieve at least two goals: 1) a scientific one that aids in finding causative connections and to prognosticate a situation; 2) a practical one that assists in developing regional programs for disease control and prevention. It is necessary to use the recommendations described in detail in the article in order to have the maximum results during medical and ecological mapping by the regions with a future goal of obtaining useful prognostic information.

[Polymorphism of the cox1 gene in bird schistosome cercaria isolates (Trematoda, Schistosomatidae) from ponds of Moscow and Moscow oblast].

Polymorphism of a 8 10-bp mitochondrial cox1 gene region was studied in 16 cercaria isolates of bird schistosomes (family Schistosomatidae), which were collected in water bodies of Moscow and Moscow oblast and represented three species: Trichobilharzia szidati, T. franki, and T. regenti. A substantial predominance of AT (65.4%) was characteristic of the cox1 sequences in all three species. Rare single nucleotide substitutions determined low (0.2-0.9%) intraspecific nucleotide and amino acid sequence diversity. Haplotype diversity h was high (80-100%) in all three species, suggesting a unique character for almost all cox1 sequences in the sample. Phylogenetic trees based on the nucleotide and amino acid sequence variations were constructed to study the relationships of the three schistosome species. A high support was observed for the main branching node that reflects differentiation of the monophyletic group Trichobilharzia and species of the genera Bilharziella (B. polonica), Dendritobilharzia (D. pulverulenta), and Gigantobilharzia (G. huronensis). Based on the nucleotide substitutions and amino acid polymorphisms, two groups of isolates, which infect Lymnaea stagnalis (T. szidati) and snails of the group Radix (T. franki and T. regenti) respectively, were isolated in the genus Trichobilharzia. The time of divergence between the two schistosome groups infecting snails of the genera Radix and Lymnaea was calculated from the cox1 nucleotide substitution rate, which is known for Asian and Indian blood flukes from the genus Schistosoma and is 2-3% per million years on average. Divergence of the three bird schistosome species under study and divergence of the Asian species of mammalian schistosome were almost concurrent, dating back to 2.5-3.8 Myr ago. Factors responsible for the lack of intraspecific subdivision with respect to the cox1 gene in bird schistosomes and the lack of separation between two species (T. franki and T. regenti) are discussed.

[Phylogenetic relationships among schistosomatidae].

According updates on molecular genetics, the development of human schistosomes in Asia with subsequent migration to the African continent is considered to be the most probable course of events. Generally, there are 2 hypotheses of the genus Schistoma. A hypothesis of Gondvana origin was based on snail host phylogeny and paleonthology and considered first schistosomes to originate on this continent to and appear in Asia from the Indian subcontinent platform 70-150 million years ago and in South America before Gondvana's split 60-120 million years ago. The recent data of molecular genetics show a high similarity between ITS2 sequences of S.bovis and S.intercalatum, with slightly lesser one between S.bovis and S.matthei. The similar pattern with slightly fewer differences can be seen in variability of cytochrome C subunit 1. Webster et al. 2006 noted a generally high similarity among species of the African group of schistosomes and considered it to originate from interspecies hybridization inside this group. Such hydridization occurring in both nature and a laboratory can make uncertain the determination of schistosome species based on a certain single gene marker.

[Individual and population variation in cercariae of bird schistosomes of the Trichobilharzia ocellata species group as revealed with the polymerase chain reaction].

The polymerase chain reaction with arbitrary (RAPD-PCR) or specific primers was used to study the population variation and to identify the species in cercariae of schistosomes of the Trichobilharzia ocellata species group (Trematoda, Schistosomatidae). In total, 28 cercariae were obtained from two spontaneously invaded mollusks Lymnaea stagnalis (LS) and L. ovata (LO), which were collected in different water bodies of Moscow. RAPD-PCR was carried out with two arbitrary primers, OPA9 and OPB11, which each detected different levels of individual and among-group variation and revealed considerable genetic differentiation of cercariae from different host mollusks. To check whether the cercariae of the two samples belong to one species, sequencing was performed with a region corresponding to intergenic transcribed spacer 2 (ITS2), which was earlier proposed for cercaria identification in three European species of bird schistosomes of the genus Trichobilharzia (T. franki, T. regenti, and T. szidati). The ITS2 sequences of two LO cercariae were identical, each consisted of 319 bp, and showed 100% homology to the T. franki ITS2 sequence. The ITS2 sequences of two LS cercariae were identical, each consisted of 323 bp, and showed 99.4% homology to the T. szidati counterpart. The causes of genetic variation in cercariae and prospects of using RAPD markers to study different stages of the life cycle in trematodes are discussed.

Comparative morphology of eggs of the Haplorchiinae (Trematoda: Heterophyidae) and some other medically important heterophyid and opisthorchiid flukes.

The egg morphology of the following medically important small flukes from Southeast Asia and Far East were studied: Opisthorchis viverrini, Clonorchis sinensis (Opisthorchiidae), Haplorchis taichui, H. pumilio, H. yokogawai, Stellantchasmus falcatus and Metagonimus sp. (Heterophydiae). This study revealed a great intraspecific variability and interspecific similarity in size and shape of eggs. The eggs shape does not seem to be suitable for species identification. On the other hand, biometrical analysis of egg size enabled us to divide eggs from the species studied into four distinct groups according to the Faust-Meleney index (FMI) characterizing egg size rather than the length and width of eggs. The surface structures of eggs, delineated by using a scanning electron microscope (SEM), appeared to be a suitable morphological feature for distinguishing some groups of small flukes. Eggs from the Haplorchiinae were typified by the characteristic filamentous mesh structure. The problems of identification of eggs in human stool samples and suitability of using morphological criteria such as shape and size of eggs are discussed herein.

[Heterogeneity of populations of the mollusc Bithynia inflata according to the degree of trematode infestation in opisthorchiasis foci]. / Geterogennost' populiatsii molliuskov Bithynia inflata po stepeni invazirovannosti trematodami v ochagakh opistorkhoza.

Results of studies of differences in the infection rate of natural populations of Bithynia inflata with trematodes (including Opisthorchis felineus) in the nidi of opisthorchiasis in the Sumsk and Chernigov Districts of the Ukrainian SSR and Tomsk District of the RSFSR are given. It has been shown that in the Ukrain over 1/3 of all populations of the specific intermediate host of opisthorchis does not take part in the circulation of the agent due to fundamentally different reasons: resistence to the infection and hyperinfection with parthenites of trematodes.

[Biological aspects of the problem of opisthorchiasis]. / Biologicheskie aspekty problemy opistorkhoza.

The paper reports the latest data concerning genesis and structure of opisthorchiasis area; biology, ecology, position in the system and distribution of the first intermediate hosts of Opisthorchis felineus; peculiarities of infections with Opisthorchis of the first and second intermediate hosts. The methods of chemical control of mollusks, the first intermediate host of Opisthorchis, are discussed.

[Concept of foci in opisthorchiasis]. / Poniatie ochagovosti pri opistorkhoze.

The elementary focus of Opisthorchis infection is identified as an area of endemic territory in which is present and realized the risk of infection of an additional host. The focus is identified as an area of endemic territory in which is present and realized the risk of infection of a definitive host. Prerequisites for the formation of the elementary focus and focus of Opisthorchis infection within the endemic territory are considered.

[Perspectives of the control of Opisthorchis invasion by the method of treating the molluskan population]. / Perspektivy bor'by s opistorkhoznoi invaziei metodom ozdorovleniia populiatsii Molliuskov

Sanitation of the mollusk population with highly effective cercaricide preparations can be used for the control of opisthorchosous infection. Low concentrations of molluskocides which are sublethal for non-infected mollusks have turned to be lethal for hyperinfected individuals. All tested molluskocides display a cercaricide effect in concentrations which are considerably lower than molluskocide ones. Low concentrations of cercaricides are toxic both for cercariae and parthenites from the liver of mollusks and for freely swimming cercariae. Disastrously affecting the freely swimming cercariae microdoses of cercaricides prevent the infection of the second intermediate hosts. Microdoses of cercaricides which are lethal for cercariae are not toxic for the majority of hydrobionts including fishes of all age groups. As far as the dynamics of the infection level of Bithynia with O. felineus is characterized by a one-peak curve with a distinct peak in the middle-end of July the treatment of water bodies with microdoses of cercaricides should be carried out just in this period.

[The ecological prerequisites for a worsening of the cercariasis situation in the cities of Russia (exemplified by the Moscow region)]. / Ekologicheskie predposylki obostreniia situatsii po tserkariozam v gorodakh Rossii (na primere Moskovskogo regiona).

Conditions favouring the sharp increase of risk to be infected with cercariasis (caused by trematode cercariae Trichobilharzia ocellata Brumpt, 1931, Schistosomatidae) were examined in Moscow region (Russian Federation). Main factors of worsening the cercariasis situation are as follows. a) The increase of environment pollution by everyday wastages and the overgrowing with macrophytes in internal water basins of Moscow, that makes favourable conditions for the development of molluscs, which are intermediate hosts (mainly Lymnaea ovata and L. auricularia). b) The sharp increase of number of ducks (mainly mallard Anas platyrhyncos), which are final hosts, that is a result of bird escaping from farms (approximately in 60-70-th) and of high adaptation of these birds to city water basins. The detailed estimation of the cercariasis situation in 89 water basins of different types in Moscow and recreation zone was carried out. Examples of charting the zones with different risk degree of cercariasis infection are given. It is stated that at current time the cercariasis became a significant and widely distributed medical problem, which is most important in cities (including such large one as Moscow). Prophylaxis recommendations are proposed.

[Morphological peculiarities of schistosomatid cercariae of Trichobilharzia cf. ocellata group occuring in Moscow and Saint-Petersburg populations]. / Osobennosti morfologii shistosomatidnykh tserkarii gruppy Trichobilharzia cf. Ocellata iz populiatsii Moskvy i Sankt-Peterburga.

Morphology of schistosomatid cercariae of the genus Trichobilharzia (ocellata group) is described based on original and reference data. The material (Trichobilharzia cercariae) was collected in 1999-2000 from naturally 'infected snails Lymnaea stagnalis from Moscow and Saint-Petersburg megalopolises. The more accurate flame cell formula for these cercariae, as well as some aspects of chaetotaxy and eye morphology are given. The differences between cercariae from these regions were found. Based on a comparison of nef data with the reference data, it was found that the cercariae examined differ from those from the Central Europe.

[Susceptibility of Bithynia inflata mollusks from different populations to Opisthorchis felineus infestation]. / Vospriimchivost' molliuskov Bithynia inflata iz raznykh populiatsii k zarazheniiu Opisthorchis felineus.

The paper reports the results of experimental infection of a specific intermediate host, molluscs Bithynia inflata from differently susceptible populations, with Opisthorchis felineus in one opisthorchis nidus. Non-susceptibility of molluscs from resistant and hyperinfected populations to O. felineus infection is shown.

[Susceptibility of Bithynia inflata mollusks from discrete populations for Opisthorchis felineus infestation from different foci of opisthorchiasis]. / Vospriimchivost' molliuskov Bithynia inflata iz razobshchennykh populiatsii k zarazheniiu Opisthorchis felineus iz raznykh ochagov opistorkhoza.

Experiments were conducted on crossed infection of the specific intermediate host of Opisthorchis, molluscs of Bithynia inflata from different and remote populations, with eggs of O. felineus from different nidi of the disease. The strains of the agent were found to be heterogeneous that is expressed in different degree of compatibility with the intermediate host.

[Method for the individual maintenance of mollusks infected with Schistosoma larvae in a thermostatic apparatus]. / Metodika individual'nogo soderzhaniia molliuskov, invazirovannykh lichinkami shistosom, v usloviiakh termostatirovaniia.

A technique has been suggested for individual maintenance of intermediate hosts of Schistosoma mansoni, molluscs of the genus Biomphalaria, in thermostat water bath with thermoregulator in order to study the host-parasite relationships in the mollusc-trematode system. Advantages of the suggested technique have been shown for studying total production of Cercaria when estimating the compatibility degree of various strains of S. mansoni and races of molluscs of some species of the genus Biomphalaria.

[A polymorphism study of the genomic DNA of trematodes at different phases of development]. / Issledovanie polimorfizma genomnoi DNK trematod v raznykh fazakh razvitiia.

Polymorphism of the genome DNA in different development stages of trematodes by means of the polymerase chain reaction (PCR) with universal primers was investigated. Interspecific variation in Trichobilharzia ocellata (cercaria) was shown in samples from the Moscow area and some regions in Byelorussia (Naroch Lake). Population groupments of T. ocellata are correlated with migration routes of subpopulation groupments of city populations of the mallard duck (Anas platyrhynchus). The cercariae of T. ocellata from rather distant geographical isolates (Moscow and Naroch Lake) differ by PCR pattern in greater extent than groupments of cercariae within Moscow. These distant isolates are considered to be members of separate populations. The cercariae of T. ocellata emitted from infected snails belonging to the different species (Lymnaea auricularia, L. ovata, L. pusilla pusilla) and during definite period (6 days with 24 h analysis) do not differ by the PCR patterns. T. ocellata cercariae emitted from L. auricularia in autumn period (from molluscs of the new generation in "new" summer infection) are found to be different significantly from the "spring" cercariae of the same year and the "autumn" ones of the previous year. The study of the experimentally reproduced life cycle of Opisthorchis felineus revealed an essential difference of cercariae genome. DNA from that in other development stages. This indicates, that genetic reorganisation in the genome of products of parthenogenetic development took place in the parthenita stage.

[Migratory capabilities of Bithynia inflata molluscs in a western Siberian opisthorchiasis focus (studied by the use of radioactive marking)]. / Izuchenie migratsionnykh sposobnostei molliuskov Bithynia inflata z Zapadno-Sibirskom ochage opistorkhoza (s primeneniem radiomarkirovki).

Migratory abilities of Bithynia inflata have been studied. The investigations have been carried out in the West-Siberian nidus of opisthorchiasis during four summer seasons since 1975. Mollusks were marked with isotopes 60Co and 110m Ag. It has been established that the mollusks do not migrate for long distances, prefer to lead a settled life and do not leave their constant biotopes even during spring floods. Migrations of mollusks within their biotopes take place, in general, along the shore line. After drying of water mollusks spend this unfavourable period in surface layers of the bottom mud or under the layer of vegetation litter-fall.

[An estimate of the potentials for eliminating aqueous biocenoses relative to free-living life forms of Opisthorchis felineus]. / Otsenka éliminatsionnykh potentsialov vodnykh biotsenozov po otnosheniiu k svobodnozhivushchim zhiznennym formam Opisthorchis felineus.

Different methods of estimating the elimination potential of invertebrate hydrobionts, members of water biocenoses, in relation to freeliving instars such as egg (miracidium) and cercarium of O. felineus are considered. Calculatons and conclusions are based on field and laboratory investigation carried out in the period 1985-1992. The elimination process in biocenoses does not practically influence on the intensivity of infection, but influences significantly on the extensivity of the infection of the molluscs Codiella with O. felineus larvae. This process is also the cause of low extensivity of infection of Codiella in natural water reservoirs (usually less than 1-2.5%) in all infection centres of exUSSR area including Western Siberia. The eggs (miracidia) of O. felineus are eliminated with different effectivity by invertebrate of nectobentos (oligichaeta, molluscs, and with less rate by arthropods). Coracidia are eliminated generally by nectoplancton crustaceans and water insect larvae. Invertebrate hydrobionts eliminate about 70% cercaria of the number of cercaria of the number coming out the infected molluscs being intermedial hosts.

[Parasitic systems under the conditions of human pressures (the problems of parasitic contamination)]. / Parazitarnye sistemy v usloviiakh antropopressii (problemy parazitarnogo zagriazneniia).

Foundations of the Parasitic Contamination (PC) conception being considered as an element of biological contamination and manifested itself in urbanized ecosystems under an influence of diversiform ecological (amenable to anthropopressure) and socio-economical factors are presented. PC is regarded as the "superthreshold" contamination exceeding the "natural background" (i.e. the parasitological situation outside urbanized ecosystems). As a rule, PC is accompanied with events as follow: an increase (often explosive in character) of hosts' number of all ranks, of vectors numbers and finally of parasites' numbers (parasitic expression); a partial replacement of parasite faunas (parasitic succession); a capture of new territories and hosts (parasitic expansion). As a rule, all processes run synchronously. They lead to disturbances of evolutionary generated relations (quantitative and qualitative ones) in parasitic systems and thereafter to changes in a tension of epidemic, epizootic and epiphytotic processes. It is assumed, that rates of evolutionary processes going in parasitic systems is increased at the recent historical stage. Their entropy character is being changed: they often transform from more of less regulated (balanced) processes, which were achieved in a long course of component coevolution, into chaotic (unbalanced) ones. It is stimulated with a powerful and at the same time differently vectored anthropogenic pressure onto parasitic system components. It promotes inhibition processes involved in generating of a natural parasite-host mutual adaptation.

[The role of the water factor in the dissemination of Toxocara eggs and the spread of toxocariasis in a megalopolis]. / Rol' vodnogo faktora v rasseivanii iaits Toxocara i rasprostranenii toksokaroza v usloviiakh megapolisa.

The water factor in transfer of the activators toxocariasis was not taken into account by parasitologists earlier. Yet in the urbanized ecosystems (first of all--in the megalopolis) it can have rather appreciable importance in distribution of toxocariasis in animals and man. Our researches which have been carried out in reservoirs of Moscow with the "wild" and the "organized" beaches, have revealed various, but as a whole their significant, of contaminations by invasion eggs Toxocara (Toxocara canis, T. mistax, and Toxascaris leonina). It specifies an opportunity of their hit in organism of the man and, as a consequence--toxocariasis. The examination of the patients toxocariasis of the people (first of all of children at the age of 3-10 years) have confirmed the fact of their bathing and involuntary swallow of water in urban unflowing reservoirs. In ecosystems of the megalopolis at a high level of parasite of pollution increased superinvasion of dogs and cats and free access of animals to internal reservoirs--the risk of infection of the people toxocariasis gradually grows.