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Parasites of Domestic Animals and their Life Cycles in Ecosystems Influenced by Man JAN PROKOPIC Institute of Parasitology (CSAV) Historical writings of ancient civilizations indicate that man has suffered from parasites practically since his origin. Malaria deci- mated the troops of ancient Rome, and microscopic blood parasites determined the results of more battles than did the most famous leaders. Fleas which transmitted a causative agent of the plague Pasteurella pestis caused the extinction of one-third of the European population in the 17th century. Also, populations in the tropics have been decimated by malaria, sleeping sickness, yellow fever, and schistosomiasis. Parasites and their hosts are members of the biocenosis of certain ecosystems. Therefore, a complex ecological approach is necessary to adequately study this problem. Since man shares the same environment with other animal spe- cies, the circulation of parasites between man and animals is quite common. For example, in Czechoslovakia the protozoan Toxoplasma gondii is widely distributed both in domestic and wild animals and in man. Similarly, larvae of Toxocara cants, a dog parasite, are often found in man as so-called Larva migrans (Sebek et al. 1975, ProkopiC and Klabonova 1979). Many human parasites develop in domestic or wild animals, e.g., Diphyllobothrium latum in crustaceans and fishes, Taenia saginata in cattle, Taenia solium in pigs, and Echinococcus granulosus in dogs and other carnivores. Trichinella spiralis occurs as a parasite in all mammal species including man (Prokopic 1959,1962). Thus, rapid ecological development stimulated by the social necessity 178
179 to solve basic questions concerning the environment of man and agriculture requires a complex approach. Recent worldwide developments in parasitology have created great interest in developing countries where parasitoses of man and animals have reached large dimensions. Developments in transporta- tion and the frequent migration of inhabitants and animals between countries and between continents influence the distribution of para- sitoses (Prokopie 1983). Parasites can be easily transmitted long dis- tances. Some species of parasites are introduced into remote places, where they have never occurred before. For example, the large liver fluke Fascioloides magna, which infests deers and other ruminants, was introduced into Czechoslovakia from Canada and has already spread throughout Europe. Similarly, a great number of parasitic species were introduced with the muskrat, e.g., Ondatra zibethica, into Europe and Asia where they have adapted to other rodents (Spassky et al. 1951). Many fish parasites have been introduced along with fish imports in recent years. Another factor of global importance is the change of ecological conditions under the influence of anthropogenic agents. This results in new characteristics in the circulation of some parasites (ProkopiC 1976). Of concern are the large-scale breeding of farm animals, in- tensive fish breeding, game parks, and refuse dumps. Also, some negative factors influence the life cycles of parasites so they have no possibility to realize their developmental stages in the given environ- ment. For example, trichinellosis in pigs and man can be eliminated in large-scale breeding of pigs, since pigs have no contacts with free- living animals and the reservoirs of trichinelles in the human food chain are consequently reduced. Favorable conditions for mass oc- currence of some parasites can also appear, especially pinworms and lice in children and coccidia in calves, pigs, rabbits, and poultry. Consequently, parasitological research must be directed both to basic research and to application, especially from the point of view of prevention, chemotherapy, disinfection, and total control of par- asitoses and diseases of man and animals transmitted by parasites. Application of new methods and improvement of technical equip- ment enable us to study thoroughly the systematics, taxonomy, and morphology of parasites. The bionomy of individual groups of parasites, especially eco- nomically important species, must be studied intensively. Of interest
180 in basic research of parasites are new methodologies and new tech- nical possibilities in morphology, pathological ultrastructure, bio- chemistry, biophysics, and mathematics which permit more accurate elucidation of parasite/host/environment relationships. Epidemiol- ogy and epizootiology of parasitic diseases of both man and animals should be thoroughly studied. Recently, the influence of anthropogenic factors on the develop- ment of parasitesâwarming of water, new technologies in breeding of farm animals, and changes in landscapeâhave become of great interest. We suppose that anthropogenic factors can considerably influence flora and fauna and consequently form new ecological con- ditions for the development of parasites. Research on parasites of free-living animals (ProkopiC 1972, 1973) and parasite/host relation- ships in various ecosystems should not be neglected. Numerous discoveries have been achieved in immunological re- search of parasitoses which have resulted in reevaluation of some concepts concerning this biological process. This trend is evident in the development of immunodiagnostics, irnmunopathology, and immunoprophylaxis (Kudrna, ProkopiC 1985). Knowledge and ap- plication of transplantation immunology and oncology can be used in this research (Kudrna, Prokopift 1986). The acquisition of denned purified antigens for serological tests can be helpful. The introduction of biotechnological methods in production of monoclonal antibodies would be of great significance, and these antibodies could become a source of immunosorbents for obtaining highly specified antigens. After the Second World War insecticides based on chlorohydro- carbons, especially DDT and HCH, were extensively used to destroy insect pests affecting plant production and parasites detrimental to health. Serious disadvantages of these chlorohydrocarbons ap- peared relatively soon, including their accumulation in the tissues of vertebrates, their toxicity, and the development of resistance in arthropods, in animal communities, and in biocenoses in general. Studies of the relationships between hosts and parasites show the complexity and heterogeneity of problems and distinct differ- ences in pathogenicity. Parasites have different developmental cycles which depend on specific intermediate hosts or vectors. This re- sults in variability of responses in host tissue. In addition, parasites which develop only in one host challenge very different pathological reactions during their development (Schramlova and Blazek 1984). Protozoa attack cells directly or are destroyed by phagocytes in a multicellular reaction. A toxic effect of the metabolic products of
181 numerous parasites has been demonstrated. This effect results in necroses of different ranges, an inflammatory response, an exudation of eosinophils, and in many cases the formation of granulome. The present level of parasitological research in Czechoslovakia is characterized by the completion of basic faunistic research, by elab- oration of bionomics of the more important parasitic species, and by determination of their role as pathoergots or vectors of causative agents. A significant advance in parasitological research in Czechoslo- vakia has been the acquisition of knowledge of the ultrastructure and morphology of important species of protozoa, worms, and arthro- pods. Much knowledge has been obtained about the geographical distribution and ecological conditions during the development of var- ious parasitic species, including the introduction of some parasites in Czechoslovakia. Recently in the spotlight are questions of the influence of anthropogenic factors on the development of parasites, including the introduction of parasites, warming of water, new tech- nologies in breeding of domestic animals, and landscape changes. Special ecosystems are created by refuse dumps. Anthropogenic influences are reflected in changes in the composition of parasites and in some features of their bionomy. These changes can be so important that parasitoses which are not currently dangerous in Czechoslovakia can gradually become quite serious. The modern age is characterized by close economic and cultural cooperation with developing countries. This provides a stimulus for intensive study of the tropics and subtropics. Waste industrial heat creates conditions for the occurrence of parasitoses introduced from warm regions, e.g., colonies of Monomo- rium pharaonis (Kohn and VlCek 1982) and the occurrence of soft ticks Argasidae in dumps. Further, the existence of pathogenic amoe- bae of the group Limax has been detected in warm water and in swimming pools (Cerva, Novak, and Culbertson 1968). In advanced industrial countries, individual fields of animal pro- duction have become large-scale breeding grounds for parasites. In- tensification of the production of animal products, maximum utiliza- tion of biological material, and the increase of labor productivity to provide food self-sufficiency are the aims of many countries. Large- scale breeding of farm animalsâespecially cattle (calves), pigs, and poultryâhas resulted in many problems concerning the health of these farm animals (Kotrla and Pavlasek 1980). Parasites generally belong to the negative factors in breeding of farm animals; they damage the host, either directly or indirectly.
182 In most cases, they become "the entry gate" for other pathogenic agents. Due to high concentrations of young farm animals, optimum conditions for effects of different pathogenic agents arise. Gastrointestinal nematodes parasitizing in domestic animals are considered to be the main cause of important economic losses. In recent years, problems of protozoan diseases of young farm animals, especially calves, piglets, and lambs have stimulated research on cryptosporidial infections. Insecticides are still commonly used to combat parasitic insects. It is necessary to develop new, more effective, insecticides with fewer side effects and without long-term residual build up in the environ- ment. Resistance of pests indicates a need for chemical groups which have not yet been applied, e.g., benzoylphenylurea derivatives which stop the synthesis of chitin and its accumulation in cuticula. The pos- sibilities of utilization of chemicals which are effective on juvenoids and pheromones have not been fully explored. Some methods of biological control have good prospects, e.g., bacteria, fungi, proto- zoa, or nematodes (Bacillus thuringiensis, Coelomomyces, Nosema algerae, Mermithidae). Studies of genetic control are being carried out especially in Diptera where sterile males or females with cellular incompatibility are introduced into normal populations. Production of antibodies in hosts evoked by inoculation of tissues obtained from infesting arthropods is under consideration. Due to the influence of anthropogenic factors, considerable eco- logical changes of the environment occur causing the extinction of some ecosystems and formation of new ones. Parasites react as members of ecosystems and these interrelationships warrant further study. REFERENCES 6erva, L., K. Novik, C.G. Culbertson. 1968. An outbreak of acute, fatal amoebic meningoencephalitis. Amer. J. of Epidemiology, 88/3:436-444. Kohn, M., M. Vliek. 1982. The occurence of Monomorium pharaonia (L.) outside human dwellings. Folia parasitol. 29:350. Kotrla, B., I. Pavlasek. 1980. The impact of different cattle management on the incidence of helminths in various age groups. Folia parasitol. 27:104-115. Kudrna, K., J. Prokopic. 1985. Vaccination of mice against Taenia Cratncepi infection using living cells prepared from metacestodes. Microbios Letters, 29:61-63. Kudrna, K., J. Prokopid. 1986. Vaccination against cestodes - review and prospect. Proceedings of second int. symp. Taeniasis/Cysticercosis and Echinococcosis/Hydatidosis, p.46-55.
183 Prokopii, J. 1959. Problem of diagnostics of Trichinellosis in free-living mam- mals. Cs. epid. mikrob. a imunol. 8:202-207. Prokopii, J. 1962. Trichinellosis in Czechoslovakia. Wiadom. paras. 8/11: 183- 187. Prokopic, J. 1972. Biocenotical study on cestodes of small mammals in various biotopes. Acta Sc. Nat. Brno 6/10:1-68. ProkopiJ, J. 1973. Biocenotical relationships among helminths of Microtu* Arvalis and their changes in various biotopes and seasons. Vest. Cs. spol. lool. 37:37-55. Prokopii, J. 1983. Contribution to the epidemiology of Taenia Saginata. Pro- ceedings of first int. symp. human taeniasis and cattle cysticerocis. 16-20. Prokopic, J., V. Klabanova. 1979. Epidemiological research of dogs in Ceske Budejovice as source of toxocarosis. Zpravy Cs. spol. paras. 19/3-4. Schramlova, J., K. Blaiek. 1984. Some aspects of histochemical investigations of the parasite and tissue reaction in bovine cysticercosis. Folia paras. 31:37-44 Spassky, A.A., N.P. Romanova, N.V. Naydenova. 1951. New data about parasitic worms of muskrat: Ondatra, abtthtca L. (in Russian). Trudy gelm.lab. 5:42-52 Sebek, Z., J. Prokopii, W. Sixl, Z. Wurst. 1975. Kann der Hunderpulwurm Tox- ocara canis (Werner 1782) dem Menschen gefahrlich werden? (Nematoda, Anisahidae). Mitteilungen der Abteilung fur Zoologie 4/1:61-65.
