Anthropogenic influence on the fish parasite fauna in lakes is studied. Three types of the influence are considered, namely pollution by industrial effluent, anthropogenic eutrophication, and development of aquaculture. Their effects on the fish parasite fauna were found to be different.
Sanitary and parasitological studies of the waste effluents and surface reservoir waters were conducted in the south of Russia. The efficiency of purification of waste effluents from the pathogens of parasitic diseases was investigated in the region's sewage-purification facilities. The water of the surface water reservoirs was found to contain helminthic eggs and larvae and intestinal protozoan cysts because of the poor purification and disinfection of service fecal sewage waters. The poor purification and disinvasion of waste effluents in the region determine the potential risk of contamination of the surface water reservoirs and infection of the population with the pathogens of human parasitic diseases.
To determine rate of infection of protozoa by enteroviruses to assess the potential role of protozoa as a natural reservoir of enteroviruses.
The samples were collected from flowing and stagnant water reservoirs in Orenburg region in summer and autumn. The samples of sewages were taken in all stages of their treatment. Cultures of protozoa were isolated with micromanipulator equipped with micropipette, incubated on Pratt's medium at 25 degrees C and fed with Pseudomonas fluorescens culture. RNA of enteroviruses was detected by reverse transcription polymerase chain reaction (RT-PCR).
Seventy-two protozoan species were found in Ural river, whereas 15 and 38 species were found in lakes and sewages respectively. Enteroviruses were detected by RT-PCR in 61.8% cultures of protozoa belonging to 23 species of flagellates, amoebae and ciliates isolated from natural water bodies undergoing anthropogenic impact as well as from sewages in all stages of their treatment. Predominant localization of enteroviruses in dominant taxons of protozoa (Paraphysomonas sp., Spumella sp., Petalomonas poosilla, Amoeba sp.) was noted.
Obtained data confirm presence of enteroviruses in protozoa living both in flowing and stagnant recreation natural water bodies as well as in sewages and confirm the hypothesis of persistence of enteroviruses in protozoa and the reservoir role of the latter. Contingency of life cycles of viruses and protozoa allows to explain the seasonality of aseptic meningitis incidence caused by enteroviruses, which peaks in summer and autumn when protozoa massively multiply in water bodies.
Distribution of Aspidogaster conchicola Baer, 1827 in the organisms of its hosts Colletopterum spp. from the Chivyrkuiski Gulf of Lake Baikal was investigated. The number of A. conchicola in the organism of Colletopterum spp. was found to decrease along the row pericardial cavity-mantle cavity-gills-kidney. The pericardial cavity of Colletopterum spp. is the most favorable habitat for A. conchicola with 72% of the helminthes parasitizing in it. In the pericardial cavity the largest number (61%) of A. conchicola was found in its posterior part.
The quantitative importance of ciliates, foraminifers, and amoebae was investigated in marine, brackish, and freshwater sediments from 15 littoral stations. Total protozoan communities were usually dominated by ciliates in term of abundance, while amoebae often dominated in terms of biomass. Applying the biomass-metabolic rate equation, ciliates, amoebae, and foraminifera were estimated to contribute 66% of the total abundance and 33% of the biomass, but up to 55% of the combined metabolic rate to the micro- and meiobenthos in the 15 sediments. Statistical analyses using ciliate data demonstrated: (1) species composition and community structures represented significant differences between freshwater and marine/brackish sediments, and subsequently between temperate and arctic sampling sites; (2) the occurrence of dominant ciliates and their allocation to feeding types indicated that herbivory was the most common feeding strategy in these sediments; (3) multivariate analyses showed all of the tested environmental factors (temperature, salinity, silt/clay, carbon, nitrogen, and chlorophyll a) to be important to varying degrees, but especially the combination of salinity, temperature, and silt/clay. Multiple factor effects or comprehensive influences might be important in regulating the distribution of protozoa in sediments. The importance of protozoa in sediment systems and the potential ecological significance of cysts are discussed.
[Ecological bases of the combination of natural foci of Trematoda infections in the floodplain-river ecosystem of the Konda River. Communication 2. Host population-combined foci of Trematoda infections]
In the context of the present-day teaching of parasitocenoses and the proposition that the pathogen's population is the only compulsory and specific component of a natural focus, the author discloses the ecological bases of the combination of natural foci of opisthorchiasis and methorchiasis (M. bilis), methorchiasis (M. bilis) and methorchiasis (M. xanthosomus). These foci are host population-combined. While analyzing the combination of foci, it is expedient to consider them in pairs since this provides a way of identifying only the combination bases that are unique to these foci. The parasitic systems of flukes, the parasitocenoses of co-acting parasitic systems of "twin types", the structure of foci, the species-specific composition of ecosystems, and the ecological relations of the Opisthorchis fluke hosts act as the biotic bases of a combination of foci of Trematoda infections. By coinciding, the multihost hemipopulations of parasites and the susceptibility of host populations predetermine the combination of Opisthorchis fluke foci. The susceptibility of hosts, the multihost pattern of Opisthorchis flukes, the identity of parasitic systems, and the common mechanism of pathogen transmission act as the epizootic bases of a combination of invasion foci. The morphological structure and hydrological regime of a landscape act as the abiotic bases of a combination of foci. The hydrological regime is by its nature a universal mechanism of pathogen transmission. The foci of Opisthorchis flukes at the level of parasitocenosis of metacercarium populations and fish populations in the Konda River ecosystem are combined in the age groups of only carp (Cyprinidae) underyearlings and yearlings. The abiotic, biotic, and epizootic bases of a combination of natural foci of Opisthorchis flukes are, in the aggregate, the ecological bases of a combination of foci.
The avian schistosomes, Trichobilharzia stagnicolae, T. physellae and Gigantobilharzia sp., that cause Schistosome Dermatitis (Swimmers' Itch) in humans were studied in the laboratory and at Cultus Lake, British Columbia, Canada in relation to the biology and behavior of their intermediate snail hosts, Stagnicola catascopium, Physa sp. and Gyraulus parvus, respectively, and their definite bird hosts. Wind-driven, surface currents were measured. Populations of snails, close to host-bird roosting logs had a very high prevalence of schistosome infections. An experiment that mechanically disturbed the epilithic habitat of the snails using a boat-mounted rototiller or a tractor and rake, eliminated almost all of the snails if the disturbance was done in areas of high snail concentration in shallow areas of the lake during the breeding and early development phase of the snail. It is proposed that the incorporation of snail habitat disturbance into management programs is an effective way to control Schistosome Dermatitis.
The main penetration route of cryptosporidia oocysts (at the infective stage) from animal carriers in the natural ecosystems of the forest zone into the environment of human habitat has been newly established. Oocysts excreted with feces are concentrated in the surface layer of the soil, then washed into water reservoirs. The viability of oocyts from the soil and the silt of river sand banks and shallows has been experimentally shown. As a result, the natural foci of cryptosporidiosis have been found to play an important role in the supply of infective agents to rivers serving as sources of water supply. From epidemiological viewpoint natural ecosystems are comparable with cattle-breeding farms and pastures. Humans run a real risk of being infected during visits to a forest.
Autopsies of Abbottina rivularis from southern Primorye (drainage-basin of Artyomovka River, Razdolnaya River and Khanka Lake) and southern Sakhalin Island (Maloye Chibisanskoye Lake) revealed high indices of diplostomum-infected lenses of these fishes. The metacercariae have been identified as Diplostomum parviventosum Dubois, 1932, D. huromense (La Rue, 1927), D. helveticum (Dubois, 1929), D. mergi Dubois, 1932, Diplostomum sp. The most lenses of parasitized eyes possessed dorsally situated sperical protrusions of the lens capsule ("cyst"). Earlier, this phenomenon was found by Larson (1965) in naturally infected bullheads (Ictalurus). The metacercarial infection level and its dynamics, age-composition of metacercariae in both lenses and "cysts", and "cysts" production are discussed.