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Damage caused by introduced species results from the high population densities and large body sizes that they attain in their new location. Escape from the effects of natural enemies is a frequent explanation given for the success of introduced species. Because some parasites can reduce host density and decrease body size, an invader that leaves parasites behind and encounters few new parasites can experience a demographic release and become a pest. To test whether introduced species are less parasitized, we have compared the parasites of exotic species in their native and introduced ranges, using 26 host species of molluscs, crustaceans, fishes, birds, mammals, amphibians and reptiles. Here we report that the number of parasite species found in native populations is twice that found in exotic populations. In addition, introduced populations are less heavily parasitized (in terms of percentage infected) than are native populations. Reduced parasitization of introduced species has several causes, including reduced probability of the introduction of parasites with exotic species (or early extinction after host establishment), absence of other required hosts in the new location, and the host-specific limitations of native parasites adapting to new hosts.

In this article, the most important animal pathogens, which, according to CDC classification, can be used as biological agents, are presented. The means of dissemination and the ways of infection's propagation are reviewed. Typical and the most dangerous signs and symptoms are described, as well as the consequences of these infections.

The initial infection process of nematode-trapping fungi is based on an interaction between the trapping structure of the fungus and the surface of the nematode cuticle. A bioassay was designed to investigate the predatory response of several isolates of nematode-trapping fungi against 3 mutants of Caenorhabditis elegans (AT6, AT10 and CL261), which have been reported to differ in the reaction of their cuticle to antibodies and lectins. The bioassay was also applied to infective larvae of animal (Haemonchus contortus, Teladorsagia (Ostertagia) circumcincta and Trichostrongylus axei) and plant (Meloidogyne spp.) parasitic nematodes. Differences in trapping ability were most marked in the first 24 h, and were density dependent. Although the isolate of Arthrobotrys responded very rapidly in the first 24 h, Duddingtonia flagrans was generally the most effective isolate and Monacrosporium responded relatively poorly throughout all experiments. All the fungi tested trapped the srf mutants of C. elegans more efficiently than the wild type, and there were differences between the different srf mutants of C. elegans. Differences in trapping ability were also observed between different isolates of D. flagrans; similarly, differences in trapping behaviour were observed not only amongst the different species of plant-parasitic nematodes, but also between the sheathed and exsheathed larvae of the animal-parasitic nematodes.

Circumstances that probably attended and influenced the adoption and development of the parasitic habit amongst the Nematoda are examined. Features that allowed early terrestrial nematodes to exploit discontinuous habitats such as decomposing organic matter, are considered to have been advantageous to microbivorous Secernentea that became parasites of animals and plants. This development followed the appearance of a land flora and that the Amphibia were the first vertebrate hosts of nematodes. Life cycles involving intermediate hosts were essential in drier environments and in a aquatic ones where intermediate hosts preserve the infective stages; keeps them "in circulation", and makes them attractive to predators. It is concluded that the parasitic habit was adopted repeatedly in both Secernentea and Adenophorea, though the latter did not diversify as much. Convergence is a common feature of nematode evolution, and the typical life history pattern of 5 stadia separated by 4 moults is often greatly modified by suppression, extension and diversification of stages and their roles. There is a need to examine the nematodes, especially of invertebrates in the remaining rain forests of Gondwanaland before they disappear.

The sporozoans comprise a coherent group of protozoans, with characteristic and complex life cycles, containing 4-5000 species parasitic in invertebrates, particularly annelids and arthropods, and vertebrates. The group is a very successful one but neither its origins nor evolution are well understood. Considerations of traditional life cycles combined with newer methodologies have thrown some light on the evolutionary expansions of the main groups of sporozoans, the gregarines, coccidia, haemosporidians and piroplasms. The sporozoans of economic importance such as the coccidia, malaria parasites and piroplasms have received most attention but the data obtained have also thrown new light on the possible evolution of less well studied groups and it is concluded that conclusions based on simple comparisons of life cycles will have to be modified. It is also clear that humans have played a major part in affecting the distribution and present abundance of many sporozoans of economic significance and probably also those of less importance, and that the rates of evolutionary expansion are much more rapid than previously thought.

The trypanosomatids combine a relatively uniform morphology with ability to parasitise a very diverse range of hosts including animals, plants and other protists. Along with their sister family, the biflagellate bodonids, they are set apart from other eukaryotes by distinctive organisational features, such as the kinetoplast-mitochondrion and RNA editing, isolation of glycolysis enzymes in the glycosome, use of the flagellar pocket for molecular traffic into and out of the cell, a unique method of generating cortical microtubules, and bizarre nuclear organisation. These features testify to the antiquity and isolation of the kinetoplast-bearing flagellates (Kinetoplastida). Molecular sequencing techniques (especially small subunit ribosomal RNA gene sequencing) are now radically reshaping previous ideas on the phylogeny of these organisms. The idea that the monogenetic (MG) trypanosomatids gave rise to the digenetic (DG) genera is losing ground to a view that, after the bodonids, the African trypanosomes (DG) represent the most ancient lineage, followed by Trypanosoma cruzi (DG), then Blastocrithidia (MG), Herpetomonas (MG) and Phytomonas (DG), with Leptomonas (MG), Crithidia (MG), Leishmania (DG) and Endotrypanum (DG) forming the crown of the evolutionary tree. Vast genetic distances (12% divergence) separate T. brucei and T. cruzi, while the Leishmania species are separated by very short distances (less than 1% divergence). These phylogenetic conclusions are supported by studies on RNA editing and on the nature of the parasite surface. The trypanosomatids seem to be able to adapt with ease their energy metabolism to the availability of substrates and oxygen, and this may give them the ability to institute new life cycles if host behaviour patterns allow. Sexual processes, though present in at least some trypanosomatids, may have played only a minor part in generating diversity during trypanosomatid evolution. On the other hand, the development of altruistic behaviour on the part of some life cycle stages may be a hitherto unconsidered way of maximising fitness in this group. It is concluded that, owing to organisational constraints, the trypanosomatids can undergo substantial molecular variation while registering very little in the way of morphological change.

Abundance of the sandfly Lutzomyia longipalpis, the vector of Leishmania chagasi, was surveyed using CDC light-suction traps in fifteen villages and 180 homesteads on Marajó island, Pará State, Brazil. Flies were most abundant in cultivated areas, secondary growth and open woodland, away from savanna grassland and forest. Within homesteads, the abundance of flies in animal sheds was weakly associated with the number of hosts kept therein, and inversely related to the number elsewhere, both human and animal. Houses harboured more flies if dogs were present and if the house had: a roof of thatch rather than of tiles or tin; a thatched roof which had not been treated with insecticide; relatively more holes in walls and roof. The sex ratio of flies was more male-biased at higher densities. We weigh the importance of these variables as risk factors for Le. chagasi infection.

Nowadays the developmental process of parasitism within the nematodes of animals and plants also takes place. Rhabditida group coming from the soil saprophytic forms is an example of such evolutionary process in statu nascendi. The conditions and ways towards the close relationships between two organisms, leading from the commensalism and facultative parasitism to the obligatory one have been presented.

Between October 1976 and January 1980 a total of 368 feral goats was examined in New Zealand for the presence of Chorioptes bovis and 434 for the presence of Psoroptes cuniculi. The seasonal pattern of C. bovis infestation in feral goats was similar to that seen in sheep and cattle. The prevalence of infestation reached 100% in July and August (winter) and declined to 27% in February and March (summer). Fewer goats were infested with P. cuniculi and prevalence of infestation reached a maximum of 41% in July. No goats were found infested in the December and January samples. Chorioptes bovis infestation was independent of the age and sex of hosts. Infestation with P. cuniculi was independent of the sex of the hosts, but older goats were more frequently infested (16%) than younger goats (8.6%). Unilateral infestation with P. cuniculi was more common (74.5%) than bilateral infestation. No severe lesions were associated with C. bovis, but 21.3% of goats with P. cuniculi had the external auditory meatus blocked by waxy material and 12.8% had scabby encrustations on the ears. The importance of goats as a possible source of infestation to domestic animals is discussed.

Turgida turgida is a common parasite of the stomach of the American opossum in Florida. Worms were usually found attached to the greater curvature of the corpus of the stomach. Ulcers always occurred at the site of the attachment. Large ulcers were associated with groups of adult parasites and were found in the oldest experimental infections. Turgida turgida fed on food within the stomach of the opossum and attached to the stomach wall when not feeding. Third-and fourth-stage larvae were found in opossums in Florida mainly from May to August suggesting that this is a major period of transmission.

The prevalence of Sarcocystis in white-tailed deer (Odocoileus virginianus) and mule deer (O. hemionus) in South Dakota was determined through microscopic examination of tongue samples. The percentage of Sarcocystis infection for both species of deer was determined for prairies east of the Missouri River, west of the Missouri River, and Black Hills of western South Dakota. Sixteen percent (N = 62) of the white-tailed deer tongues from East River, 69% (N = 42) from West River, and 74% (N = 23) from the Black Hills were infected. Prevalence for mule deer was 88% (N = 24), 78% (N = 63), and 75% (N = 12) from East River, West River, and the Black Hills, respectively. Of 50 tongue samples obtained from both species of deer during a special antlerless deer hunt in the Black Hills in 1978, 66% were infected. Coyotes (Canis latrans), dogs (Canis familiaris), red foxes (Vulpes vulpes), a gray fox (Urocyon cinereoargenteus), bobcat (Felis rufus), and raccoon (Procyon lotor) were fed muscle from white-tailed deer and mule deer naturally infected with Sarcocystis to determine their role as definitive hosts. All coyotes, dogs, and the gray fox shed sporocysts, while none were recovered from the other animals. Sporocysts shed by coyotes were counted and concentrated into an inoculum and administered to a white-tailed deer fawn, which was necropsied 85 days after inoculation. Sections of heart, tongue, esophagus, diaphragm, and skeletal muscle were found to be heavily infected with sarcocysts, while sarcocysts were not detected in a control fawn.

Pilot trials are described in which BHS, a Czechoslovak fasciolicide, was employed for mass treatment of fasciolosis in cloven-hoofed animals in wild-animals' reserves at the rate of 30 mg body weight using BHS-medicated feed. The treatment was combined with control measures against the intermediate host snail, Lymnaea truncatula, in primary biotopes using Frescon, a molluscicide of English origin, and CF-4, a molluscicide of Czechoslovak origin, at concentration of 1 and 0.5 per cent, respectively. Where the application of molluscicides was impracticable the intermediate host snails were controlled by means of sciomyzid larvae or by blasting surface layers of the soil.--Using this combined approach, the extensity of infestation, evaluated on the basis of coproovoscopical examination, was reduced from 7.05 to 0.71 per cent. The extensity of infestation, evaluated on the basis of necropsy findings, was reduced from 50 to 6.2 per cent. The intensity of infestation was reduced from 7.7 to 0.31 per cent per animal.--The results may prove useful in devising fasciolosis control schemes based on a complex approach.

A total of 488 wild small mammals (16 species) trapped in two federate units of Austria, Steiermark and Burgenland, were examined on the presence of blood parasites. In Steiermark Grahamelles were detected in Neomys fodiens, Clethrionomys glareolus, Microtus arvalis, M. agrestis, Apodemus flavicollis and A. sylvaticus, while Trypanosoma evotomys and Hepatozoon erhardovae were found in C. glareolus, and Babesia microti in Pitymys subterraneus and M. agrestis. In Burgenland Grahamelles were demonstrated in Sorex araneus, C. glareolus, A. sylvaticus, A. flavicollis and Rattus norvegicus, while trypanosoma grosi was encountered in A. flavicollis and Babesia microti in C. glareolus, M. arvalis and A. flavicollis.

This paper constitutes an introduction to the forthcoming series of publications summing up the present store of knowledge on the incidence and ecology of avian haematozoa in Central Europe. The paper contains bibliography dealing with the incidence of these parasites in the region studied. The problem of the incidence of blood parasites in domestic birds is discussed in detail. The incidence of blood parasites in wild birds is only briefly outlined as it is to be treated in detail in forthcoming papers.

The results of a survey involving more than 4,000 Colombian mammals, carried out to detect Echinococcus infections, are presented. Adult worms were found in 5 of 121 carnivores: E. oligarthrus in 1 of 11 ocelots, 2 of 9 jaguarundi cats and single puma; and E. vogeli in 1 of 15 domestic dogs. Although bush dogs were present, none could be examined. Polycystic larvae were found in 96 of 325 pacas (29.5%) and in 6 of 1,168 (0.5%) spiny rats, Proechimys spp. None of the 118 agouti showed hydatids but an infected heart was provided by hunters. The paca's infection rate increased with age but was not related to sex or geographic region. In 73 of 96 pacas the infection was due to E. vogeli, and the cysts were located in the liver. In 3 it was due to E. oligarthrus and the hydatids were extrahepatic, mainly attached to muscles. In the remaining 20, the species involved could not be determined. The parasites in two of the spiny rats, and in the agouti heart were E. oligarthrus. Although most of the infected animals were collected in the eastern plains, other records and verbal information indicate that, at least in Colombia where man has not exterminated pacas, agoutis, wild canids and felids, one still can find enzootic neotropical Echinococcus infection. The cycle of E. vogeli involves the bush dog and paca as hosts, and that of E. oligarthrus, the paca, agouti, spiny rat, and several species of wild felids.

Two new species of the genus Vexillata Travassos, 1937 parasitizing Heteromys anomalus of Venezuela are described, V. tejerai n. sp. and V. scorzai n. sp., both close to V. petteri Durette-Desset, 1970 and V. chabaudi Yoyotte-Vado, 1972, by possessing of 4 dorsal ridges and the dorsal rib divided near the tip. Both new species are differentiated from V. chabaudi by having the dorsal rib much shorter than rib 8; they are distinguished from V. petteri by having ribs 2 and 3 nearly the same size. The two new species are separated by the significantly greater size of V. tejerai and by the form of the copulatory bursa. A brief historical review of the genus is given, together with considerations on its origin and its probable relation to the Pudicinae or Brevistriatinae. A key to the 8 known species is also given.

The helminth burdens of 17 springbok from 2 localities in the Transvaal and of 4 springbok from the western Cape Province were determined. Eight of the animals from the Transvaal and the 4 from the Cape Province were also examined for arthropod parasites. In all, 26 helminth species, 5 species of ixodid ticks and 4 species of lice were recovered from the springbok. Of the helminths Dictyocaulus magnus, Trichostrongylus axei, T. falculatus and Agriostomum equidentatum were recovered from animals in each of the surveys. The lice Damalinia antidorcus, Linognathus antidorcitis and L. bedfordi were present on animals in the Transvaal and the western Cape Province.

153 small mammals belonging to 22 species were investigated during the year 1975. On this occasion, 29 different species of helminths were found. Parallel-infection of one host by different helminths was common. All age-groups and both sexes of hosts were infested. Pathological symptoms like eosinophile infiltration of the lungs and splenomegalia were generally observed as accompanying phenomena of endoparasitic infestations. Often, there were no distinct symptoms even if the intensity of the infection was comparatively high. Minor infections may pass without clinical phenomena. Amongst the investigated hosts Hymenolepis diminuta, Cyticercus fasciolaris (larva of Hydatigera taeniaeformis), Strongyloides ratti and Hepaticola hepatica were the most widespread species of helminths.

Bison bison (bison), Cervus canadensis (elk), Alces alces (moose), and Bos taurus (cattle) musculature containing Sarcocystis spp. cysts was fed to laboratory raised Canis latrans (coyotes), Sporocysts collected from the feces of coyotes fed musculature of each of the ruminant species were fed to four groups of three laboratory-raised domestic calves, respectively, to determine if Sarcocystis spp. was transmissible from wild to domestic ruminants and if so, to compare clinical signs of infection and morphologic features of cysts with those resulting from infection with Sarcocystis bovicanis. All calves fed sporocysts of Sarcocystis from coyotes that ate bison or cattle muscle had similar clinical signs and harbored morphologically similar parasites, suggesting that both bison and cattle are intermediate hosts for S. bovicanis and that this species is transmissible between the two ruminant species. All calves fed sporocysts from coyotes that ate elk muscle or moose muscle remained asymptomatic but one calf in each group had intramuscular cysts. The finding of relatively large numbers of intramuscular cysts in one calf fed sporocysts of elk origin and smaller numbers in one calf fed sporocysts of moose origin could represent either spurious natural infections or indicate low infectivity of Sarcocystis spp. from elk and moose to cattle.

Sheep were successfully infested artificially with the larvae of Haemonchus contortus, Trichostrongylus axei, Trichostrongylus falculatus and Impalaja nudicollis, cultured from the faeces of blesbok naturally infested with these nematodes. Haemonchus placei, Longistrongylus sabie, Trichostrongylus colubrifomis, T. falculatus, Impalaia tuberculata and Cooperia hungi likewise became established in sheep, goats and calves dosed with larvae cultured from the faeces of infested impala. Sheep and goats could also be infested with Cooperioides hamiltoni and Oesophagostomum columbianum of impala origin, but Cooperioides hepaticae could not be transmitted either to these hosts or to calves.

Numerous intranuclear inclusion bodies in enterocytes were detected exclusively in the ileum of two nine-day piglets coming from a litter infected with diarrhea. The inclusion bodies were homogeneous in hematoxylin and eosine (HE), their staining was not clear enough, was amphophilic and they filled nearly the whole nucleus. They were eosinophil less often and had a halo on the periphery. Their staining was clearly orange-red in Feulgen's nuclear reaction after re-staining with G orange and bright green. Intranuclear inclusions were located exclusively on shortened villi and pseudovilli of ileum above the follicles of activated Peyer's patches. The findings of intranuclear inclusions in ileum demonstrate adenovirus enteral infections in suckling piglets.

A total of 38 warthog, Phacochoerus aethiopicus, shot on a farm in northern South West Africa/Namibia were examined for internal and external parasites at monthly intervals over a period of 13 months. They harboured cestodes, 9 nematode species, 6 ixodid tick species and 1 species each of an argasid tick, a flea, a louse and larvae of a dipteran fly. Clear patterns of seasonal abundance could be determined only for the spirurid stomach worm, Physocephalus sexalatus, and the sucking louse, Haematopinus phachoeri.

From 1974 to 1977, 62 wild mule deer (Odocoileus hemionus) fawns from Steens Mountain, Ore were euthanatized in autumn (23 deer), winter (21 deer), and spring (18 deer). The number of sarcocysts of Sarcocystis spp was counted in histologic sections of various muscular organs. Sarcocysts were seen in the muscle specimens of 14 of the 23 deer euthanatized in autumn (September to November) and in specimens from all 39 deer euthanatized in winter (December and January) and spring (March and April). The sarcocyst burden was greatest in the spring (736/deer), less in the winter (150/deer), and least in autumn (12/deer). Most sarcocysts collected from 3- to 5-month-old deer in autumn were immature, whereas most sarcocysts collected from 9- and 10-month-old deer in the spring were mature. More sarcocysts were seen in sections of muscles from limbs than in those of tongue, esophagus, and other skeletal muscles; the fewest sarcocysts were seen in the heart. Degenerating sarcocysts were seen in deer examined in the spring, but not in deer examined in autumn and winter. Sarcocystis was the only infectious agent found in unthrifty deer fawns. Of the 18 fawns (6 in autumn, 1974; 6 in winter, 1974; and 6 in spring, 1975) examined for helminths, only mild infections were seen in the deer examined in the spring of 1975. From 1974 to 1977, from the Crooked Creek area of Oregon, 48 mule deer fawns (12 in autumn, 18 in winter, and 18 in spring) were euthanatized and evaluated for Sarcocystis infections.(ABSTRACT TRUNCATED AT 250 WORDS)

The paper presents a survey of flea species found in the studied territory, together with data on their distribution, host relationship, seasonal fluctuations of their numbers and possible role in tick-borne encephalitis epizootiology.

500 adult roes and 100 fawns were examined microscopically for the presence of Sarcocystis gracilis von Ratz, 1901. 95.80 per cent of the roes examined had Sarcosporidias. The parasites were noticed macroscopically in less than a third of them. The abdominal muscles were affected most frequently and most strongly. The leg muscles were affected least of all. Roe bucks were affected to a lesser extent than does. From the third month of life the fawns showed an incidence of parasites which increased with advancing age. During the period of research from May till November hardly any significant difference of parasitical attack occurred in adult roes.

The natural infection of Sphaeridiotrema globulus in the mute swan and the experimental infection in the chicken resulted in an ulcerative hemorrhagic enteritis. Swans and chickens died from the resultant blood loss. Culturing of the parasite on the chorioallantoic membrane of the chicken egg resulted in hemorrhage and a cellular response of the chorioallantois to the trematode. Experimental infections in the domestic chicken and chicken embryo can be of use for the study of ulcerative hemorrhagic enteritis produced by the trematode, pathologic features, identification of the metacercaria to the adult, and developmental aspects of the parasite.

Onchocerca dewittei n. sp. was collected from a wild Boar at the metatarse level (tendons and subcutaneous connective tissue); it can be differentiated from other species by the female cuticle showing straight ridges which overlap in the lateral fields, and by its relatively thick microfilaria (length 228-247 mu and width 6-7 mu). This suidean Onchocerca displays some primitive characters such as straight ridges and persistency of ten pairs of caudal papillae in the male; but as a whole this species is undoubtedly more highly evolved than O. raillieti Bain, Müller and coll., 1976, a parasite of Equidae.

A system to designate and define isolates of Trichinella spiralis is proposed. The designation gives the host from which the isolate was recovered, geographic origin, and year of recovery. Isolates of T. spiralis recovered from frozen muscles from four species of wild carnivores had low and different infectivity to laboratory mice. Viable larvae of T. spiralis were obtained from muscle samples of marten, wolverine, polar bear and arctic fox which had been frozen for 5, 6, 12 and 14 mo, respectively.

We studied the incidence of parasites of game animals under conditions of the individual habitats occupied by game animals. Our investigations were made both in the open field and in game reserves for several game species, and also in biotopes where game animals come into contact with domestic ruminants. We detected 72 nematode species in a total of 8 species of game animals. The results show that, the composition of the helminth fauna is influenced by conditions of the external environment, i. e., by the number of specimens, the extent of the biotope, contact with other animal species, the incidence of intermediate host, and by climatic and hydrological conditions. The contact between various host species, and their parasites has to last for a prolonged period, because it requires a certain length of time before the newly introduced host becomes a member of the original biocoenosis and adapts himself to such a degree that his parasites can infect other host species and he can receive their parasites (e. g., Fascioloides magna, Ashworthius sidemi).