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Infectious diseases of domesticated animals impact human well-being via food insecurity, loss of livelihoods, and human infections. While much research has focused on parasites that infect single host species, most parasites of domesticated mammals infect multiple species. The impact of multihost parasites varies across hosts; some rarely result in death, whereas others are nearly always fatal. Despite their high ecological and societal costs, we currently lack theory for predicting the lethality of multihost parasites. Here, using a global dataset of >4,000 case-fatality rates for 65 infectious diseases (caused by microparasites and macroparasites) and 12 domesticated host species, we show that the average evolutionary distance from an infected host to other mammal host species is a strong predictor of disease-induced mortality. We find that as parasites infect species outside of their documented phylogenetic host range, they are more likely to result in lethal infections, with the odds of death doubling for each additional 10 million years of evolutionary distance. Our results for domesticated animal diseases reveal patterns in the evolution of highly lethal parasites that are difficult to observe in the wild and further suggest that the severity of infectious diseases may be predicted from evolutionary relationships among hosts., Competing Interests: The authors declare no conflict of interest.

Parasitic infections in livestock are of major economic importance. However, increasing resistance against antiparasitic drugs, which is particularly prevalent among parasitic helminths and poultry coccidia, might sooner or later call the economic viability of certain livestock branches into question. Thus, there is a need to develop new efficient parasite control tools. In addition to efforts to discover new antiparasitic compounds or to implement targeted selective treatment strategies, development of vaccines would be a future-orientated alternative. The current review elucidates to what extend antiparasitic livestock vaccines are reality or still expectations.

Cryptosporidium is an important enteric parasite that is transmitted via the fecal-oral route, water and food. Humans, wildlife and domestic livestock all potentially contribute Cryptosporidium to surface waters. Most species of Cryptosporidium are morphologically indistinguishable and can only be identified using molecular tools. Over 24 species have been identified and of these, 7 Cryptosporidium species/genotypes are responsible for most human cryptosporidiosis cases. In Australia, relatively few genotyping studies have been conducted. Six Cryptosporidium species (C. hominis, C. parvum, C. meleagridis, C. fayeri, C. andersoni and C. bovis) have been identified in humans in Australia. However, little is known about the contribution of animal hosts to human pathogenic strains of Cryptosporidium in drinking water catchments. In this review, we focus on the available genotyping data for native, feral and domestic animals inhabiting drinking water catchments in Australia to provide an improved understanding of the public health implications and to identify key research gaps.

Endo and ectoparasites of domestic ruminants directly or indirectly contribute to reduce sustainability affecting food security in subsistence or small scale farming systems, food safety (food borne diseases and pesticide residues), environment (pesticides, pollution and ecotoxicity) and farmer's equity (limited or uneven access to relevant technical information/training). This is especially true for some regions of Latin America where there still are huge areas of natural grazing land for cattle, sheep and goats. Sustainable parasite control is not an absolute concept given the different regions and productive systems of the world and therefore, could have different levels of adoption and impact on farmers. This article develops a conceptual framework to better understand where each region or country is situated in terms of attaining a reasonable increase in animal production while preserving sustainability. Within this context the capacity to prioritize the target parasite species for control according to local epidemiology and production systems, the early diagnosis and monitoring of parasite resistance as well as the availability of well trained field professionals acquire a major role, creating an enabling environment for present and future decision support system approaches. Until new and different means of controlling parasites become available; the challenge is to utilize Good Animal Husbandry Practices and Integrated Parasite Management (IPM) principles in a pragmatic way allowing the rational use of pesticides., (Copyright © 2011 Elsevier B.V. All rights reserved.)

A World Association for the Advancement of Veterinary Parasitology tradition for its conference is to present some highlights of the country hosting the event, and with an emphasis on the history of, and research in, veterinary parasitology. A review of Canada's peoples, physiography, climate, natural resources, agriculture, animal populations, pioneers in veterinary parasitology, research accomplishments by other veterinary parasitologists, centres for research in veterinary parasitology, and major current research had been presented at a World Association for the Advancement of Veterinary Parasitology Conference in Canada in 1987, and was published. The present paper updates the information on the above topics for the 22 years since this conference was last held in Canada.

Dipteran larvae were collected from wounds of 78 domestic animals. The larvae were identified as follows: Wohlfahrtia magnifica, taken from dogs (the majority), goats, sheep, camels, horses and one cat; Lucilia sericata, from cats, sheep, one horse, and one dog together with Chrysomya albiceps; Przhevalskiana silenus from goats and Musca domestica from one sheep. The animals were treated with antibiotics, anti-inflammatory agents and insecticides and most animals fully recovered. We believe this to be the first record of L. sericata and C. albiceps taken together from a dog. Likewise, the presence of W. magnifica in cats appears to be a first record.

Dogs, cats, and horses are popular pets in many countries of the World and they have lived in close proximity with human beings for thousands of years. The effect of pet ownership on human health is well known and there is significant merit in preserving the health and welfare of these animals. Some infections caused by parasitic nematodes and arthropods of dogs, cats, and horses are now spreading in several areas of the world. This is the case of canine spirocercosis, feline aelurostrongylosis, and equine gastro-intestinal and nasal nematode and botfly infections. These diseases affect animal health and welfare and may be life-threatening. In spite these infections causing illnesses of major importance in clinical practice are spreading in new geographical foci, they are little known and underestimated also as an effect of difficulties in traditional diagnostics. Importantly, the limited reliability of conventional methodologies has also limited our knowledge of epidemiology, ecology, and biology of these parasitoses. This article reviews the DNA-based assays that have been recently developed for diagnosing these neglected pet parasitic diseases focusing on the advantages they have over classical techniques. Moreover, the opportunities for further epidemiological, ecological, and biological investigations are discussed.

The aim of this paper was to explore the effect of genetic heterogeneity in host resistance to infection on the population-level risks and outcomes of epidemics. This was done using a stochastic epidemiological model in which the model parameters were assumed to be genetically controlled traits of the host. A finite locus model was explored, with a gene controlling the transmission coefficient (i.e., host susceptibility to infection) and a gene controlling the recovery period. Both genes were simulated to have 2 alleles with underlying additive or dominance inheritance and an independent assortment of alleles. The model was parameterized for a viral pig disease (transmissible gastroenteritis), and complete homogeneous mixing among genotypes was assumed. Mean population genotype dramatically affected epidemic outcomes, and subtle effects of heterogeneity on epidemic properties were also observed. Genetic variation in the transmission coefficient led to probabilities of epidemics occurring that were slightly greater than expected, but genetic variation in the recovery rate had no such effect. Epidemics were generally less severe in genetically heterogeneous populations than expected from the constituent subpopulations. Furthermore, the genotype of the initial infected animal had a marked effect on epidemic probabilities, particularly when genetic variation was for recovery rate. The results of this model provide useful information to determine the optimum population structures and to exploit genetic variation in resistance to infection. Applications of the proposed model in genetically heterogeneous populations for identifying practical disease management strategies are also discussed.

A minimum of 11 genera of parasites, including 7 known or suspected to cause zoonoses, were detected in dogs in 2 northern Canadian communities. Dogs in remote settlements receive minimal veterinary care and may serve as sources and sentinels for parasites in persons and wildlife, and as parasite bridges between wildlife and humans.

The objective of the present study was to determine the incidence of internal parasites in dogs and cats owned by the employees of the Faculty of Veterinary Medicine, University of Warmia and Mazury in Olsztyn, and by students and their families, as well as in pets presented to veterinary clinics and in animals from shelters. The study, conducted from January to May 2008, involved 135 dogs and 35 cats. Feces samples were analyzed for parasites by flotation technique with the use of Darling's solution, as described by Fülleborn. The highest percentage of parasite eggs was reported in feces samples collected from shelter dogs, including Toxocara and Toxascaris (9.1%), Uncinaria-Ancylostoma (12.1%) and Trichuris (12.1%), while in shelter cats the extensiveness of parasitic invasion was as follows: Toxocara cati--61.5%, Toxascaris--15.4%, Uncinaria-Ancylostoma--7.7%, Isospora spp.--7.7%. The lowest parasite incidence was observed among dogs and cats owned by veterinary students and members of their families. Of 20 examined animals, only one dog carried the eggs of Toxocara canis and one dog carried the eggs of Trichuris in their feces. Similar results were obtained in the group of pets owned by the employees of the Faculty of Veterinary Medicine: among 6 dogs and 13 cats examined in the study, Toxocara eggs were detected in one cat only (16.6%). In the group of pets presented to veterinary clinics, comprising 77 dogs and 8 cats, feces samples taken from 11 dogs contained the eggs of Toxocara canis, Toxascaris leonina, Uncinaria-Ancylostoma and Trichuris, while Isospora spp. oocysts were found in the stool of two cats.

Parasitic infections are a primary cause of lost productivity in livestock world-wide. Accurate detection of parasites depends on many factors, including collection, storage, and transport of the sample, as well as the method of laboratory evaluation. However, the presence of a particular parasite does not always indicate the presence of parasitic disease. For many parasites, there exists a level at which the effect on production characteristics is balanced by the effect on the development of immunity. Interpretation of test results, therefore, should also consider such factors as the age of the animal or animals, clinical history, nutrition, local epidemiology of the parasites prevalent in the area, and any treatments that have been implemented.

Dynamics of parasite communities and host-parasite-environment interactions can be influenced by different factors. The present note, by discussing some field experiences in wild and domestic ruminant populations, approaches eco-epidemiology of abomasal nematodes in relation with host health and dynamics. Factors possibly playing a role in the host-parasite relationship are discussed, as well as possible use of macroparasites as ecological and sanitary indicators. The above topics are approached in a management perspective, in particular regarding interactions between domestic and wild ruminant populations.

Most available antiparasitic drugs are safe, cheap and highly effective against a broad spectrum of parasites. However, the alarming increase in the number of parasite species that are resistant to these drugs, the issue of residues in the food chain and the lack of new drugs stimulate development of alternative control methods in which vaccines would have a central role. Parasite vaccines are still rare, but there are encouraging signs that their number will increase in the next decade. The modern paradigm is that an understanding of parasite genes will lead to the identification of useful antigens, which can then be produced in recombinant systems developed as a result of the huge investment in biotechnology. However, we should also continue to devote efforts to basic research on the host-parasite interface.

Arthropod ectoparasites can have a major impact on the productivity and welfare of livestock. In recent years, many parts of Europe have seen important changes in the nature of animal husbandry and parasite control, which have increased the need for a precise understanding of the current distribution and prevalence of livestock ectoparasites. In some cases, these changes have been associated with moves towards increased productivity, such as higher-stocking densities, large-scale rearing units, indoor confinement, reduced genetic diversity and large-scale movement of animals and, in others, with a move towards organic farming. There have also been changes in parasite control, associated with the development of new parasiticides, such as the macrocyclic lactones, and concern over the continued use of some of the older neurotoxic compounds. These changes have been exacerbated by outbreaks of endemic disease, the threats of exotic disease introduction and fears of potential changes in arthropod distribution associated with climate change. This paper therefore, reviews the current status of livestock ectoparasites in Europe and the Mediterranean region.

A stochastic epidemic model is presented to study infection transmission dynamics, and hence epidemic severity and disease incidence, in a closed population. The aim was to understand the relative importance of various parameters that influence the dynamics of potential epidemics, particularly when the genetic mechanisms of resistance or tolerance to infection are considered. Simulations explored the effect of varying the transmission coefficient, latent period, recovery period, mortality rate, and the period of loss of immunity on overall epidemic outcomes. The critical parameters influencing the transmission of infection, and hence disease incidence, were the transmission coefficient, the latent period, and the recovery period; the period of loss of immunity had only trivial effects. Ideally, control strategies should decrease the transmission coefficient and/or increase the latent period and/or decrease the recovery period. By equating measured traits with disease transmission parameters, the model described in this paper can be used to identify which disease resistance genes or QTL will be truly effective in helping to develop disease-resistant livestock that suffer fewer epidemics and side-effects of infection. In particular, emphases should be placed on finding genes that decrease the transmission of infection, increase the latent period, or decrease the recovery period.

The development of subunit vaccines against most parasitic helminth infections will require a better understanding of the different components of a natural rejection process including (1) recognition of parasite antigens; (2) induction of protective immune response phenotypes; and (3) activation of appropriate immune effector mechanisms. While novel technologies have allowed significant progress to be made in the identification of candidate vaccine antigens, the large scale production of these antigens and their presentation to the host with appropriate adjuvant systems remains a major problem in vaccine research. Identification of the molecular interactions involved in the innate immune response to helminth infections and the application of new genomic and proteomic technologies are likely to lead to major advances in these research fields. Gastrointestinal nematode parasites and liver fluke are the most important helminth parasites of production animals. In recent years, a lot of new knowledge has been gathered on the immunobiology of the host-parasite interactions in these two infection systems, which has allowed new vaccination strategies to be considered. Functional genomic technologies such as gene expression analysis by microarrays, promise to further advance our understanding of the molecular pathways leading to protection against parasite infections. This will not only have implications for vaccine research, but also provide novel targets for drug development and genetic selection.

The studies of parasite fauna have in Poland a long tradition. Generally the helmint fauna of all groups of vertebrates was more or less examined and as much as over 100 species of Monogenea, almost 400 Digenea, over 250 Cestoda, about 500 Nematoda and 32 Acanthocephala have been recorded. The best recognized are the helminths of fish (especially those of Cyprinidae, Esocidae, Percidae and Salmonidae), frogs examined in various regions of Poland, some birds (especially connected with water environment: Anseriformes, Ciconiformes, Podicipediformes), most of insectivores (although examined only in few localities), European bisons, deers, foxes and wild boars (all under permanent monitoring), as well as domestic animals (cattle, horses, sheeps) and pets. Such groups like some amphibians, reptiles, bats, carniwores, some birds (especially Passeriformes, Charadriiformes, falcons and eagles) need further exploration, as some host species were not the subject of parasitological investigation. In some cases it will be rather difficult goal, as most of these animals are under strict preservation, and only dead (naturally or accidentally) specimens can be autopsied.

A participatory research model was used in six village communities in the Central Region of the North West Province of South Africa in order to achieve the following broad objectives: to obtain information on the challenges owners face in raising livestock in these areas and to evaluate the livestock owners' level of knowledge of internal parasites in their animals. Information obtained at participatory workshops clearly indicated a need for improvements in water supply, schools, job creation, and health services. Lack of pasture for grazing livestock was also cited as being important. Other most frequently mentioned livestock problems included 'gall sickness' (a vaguely defined condition not necessarily referring to anaplasmosis), parasites (both external and internal), chicken diseases and ingestion of plastic bags discarded in the environment. When livestock owners were questioned during individual interviews, most were able to identify the presence of parasites in either the live or dead animal. However, it seems likely that this is limited to the identification of tapeworms. It was found that most livestock owners use a combination of treatments, ranging from traditional to folklore to commercial. There were some difficulties in using the participatory methods since it was the first time that the facilitators and the communities had been exposed to them. Many communities had difficulty in dealing with the concept of finding solutions within the community, which is such an integral part of participatory methods.

Over the last decade, the anti-parasitics market has been the fastest growing sector of the overall $18 billion animal health market. While drugs for the treatment of parasites of livestock still dominate this sector and will continue to be developed or re-formulated, because of consumer demands for chemical-free food and of concerns regarding the environment and animal welfare there is a growing interest in the development of safe and effective vaccines. There is also a call for vaccines in the lucrative $3 billion-plus companion animal market. These demands for vaccines will add a greater impetus to an area that has seen tremendous success in the last 15 years. A number of anti-parasite vaccines have been developed, e.g. the recombinant 45w and EG95 oncosphere proteins against Taenia ovis and Echinococcus granulosis, respectively, and the Bm86 vaccine against Boophilus microplus. In addition, the cathepsin L vaccines against the liver fluke, Fasciola hepatica, and the H11 vaccine against Haemonchus contortus are progressing well. There are also many additional vaccine candidates for H. contortus and for other nematodes such as Ostertagia and Trichostrongylus spp. that may ultimately lead to broad-spectrum gastrointestinal worm vaccines. Live or attenuated-live vaccines are available for the control of avian coccidiosis, toxplasmosis in sheep and anaplasmosis in cattle, although molecular vaccines against protozoans are still proving elusive. The wealth of information in genomics, proteomics and immunology that has been forthcoming together will new methods of vaccine production and delivery should see many new vaccines reach the marketplace in the near future.

Preparations derived from plants were the original therapeutic interventions used by man to control diseases (including parasites), both within humans and livestock. Development of herbal products depended upon local botanical flora with the result that different remedies tended to develop in different parts of the world. Nevertheless, in some instances, the same or related plants were used over wide geographic regions, which also was the result of communication and/or the importation of plant material of high repute. Thus, the Nordic countries have an ancient, rich and diverse history of plant derived anthelmintic medications for human and animal use. Although some of the more commonly used herbal de-wormers were derived from imported plants, or their products, many are from endemic plants or those that thrive in the Scandinavian environment. With the advent of the modern chemotherapeutic era, and the discovery, development and marketing of a seemingly unlimited variety of highly efficacious, safe synthetic chemicals with very wide spectra of activities, herbal remedies virtually disappeared from the consciousness--at least in the Western world. This attitude is now rapidly changing. There is a widespread resurgence in natural product medication, driven by major threats posed by multi-resistant pest, or disease, organisms and the diminishing public perceptions that synthetic chemicals are the panacea to health and disease control. This review attempts to provide a comprehensive account of the depth of historical Nordic information available on herbal de-wormers, with emphasis on livestock and to provide some insights on potentially rewarding areas of "re-discovery" and scientific evaluation in this field.

The market for antiparasitic products comprises the largest segment for sales of livestock and companion-animal healthcare agents. Despite the availability of highly effective, broad-spectrum agents, there remains a need for safer, more convenient and more environmentally friendly products that will overcome the ever-present threat of resistance development. The very high cost of discovering and developing a new drug, especially for use in livestock, is reflected in the limited number of new classes of antiparasitic agent launched on the market. New strategies are being adopted to minimise the cost of discovering potential drug candidates by maximising the chance of identifying a useful target mechanism of action and by speeding the time to discover and optimise a lead structure. These rely heavily on new technologies in target identification, screen development and lead optimisation. Examples of these will be discussed and speculation made about the possible factors that could influence the future shape of antiparasitic control.

During the past 2 decades, treatment of livestock parasitism has changed from a situation of relative stability, particularly in the mid-late 1980s when the macrocyclic lactone compounds were introduced, to the situation in many countries now where control of sheep parasites is rapidly being lost. As serious as the situation may be, now is not a time to wring our hands in despair but a time to address some of the limitations and identify opportunities where a greater integration of the efforts of research and industrial bodies might be directed to maintaining parasite control in our livestock industry.

For sustainable livestock production it is suggested that the parasitologist take a leaf out of Nature's book in the search for solutions to the mounting problems concerning parasite control. While the farmer has come to regard all parasites affecting livestock as entirely without benefit, indigenous parasites and diseases are normal and play an essential role as interacting components of a natural environment in an ecosystem such as the 19,000 km2-sized Kruger National Park, Republic of South Africa. The parasites help to select their hosts for fitness and are assisted by predators and intra-species territorial aggression which continually eliminate the weak individuals from the system. It is essential to guard against the introduction of foreign parasites or infectious agents which have no real ecological niche or role in an established ecosystem, however, as they cause untoward interactions, sometimes of a violent nature. The policy must be to block off or, failing that, to control or eliminate these foreign parasites and diseases as far as possible. Often, when Man intervenes in an ecosystem, it leads to stress, overcrowding and stagnation and predisposes to disease and death. Intensification of the system, as in farming units, denies Nature the chance to manage on its own, because of clashing interests with Man. Frank parasitism and disease should almost invariably be seen as indicators of an imbalance in the ecosystem and should be rectified. Chemicals and vaccines should be used to produce sufficient food for all, but without exploiting Nature, or else Nature will be unable to continue catering for Man's needs.

In the past, the control of parasites of domestic animals has relied mainly on the use of drugs and pesticides. Although these compounds are still of great importance in the prevention and treatment of parasitic diseases, the accent has shifted in recent years to a more flexible approach, integrating various other control measures. The main reasons for this change are: development of resistance of the parasites against the compounds used; reduced development of new compounds to overcome resistance (increasingly stringent regulations on toxicity and residues, resulting in very high research and development costs, insufficient return for industry because of short life-span of new products due to resistance, and limited and poor markets for compounds against parasites in developing countries); increasing cost of new products for the user; problems associated with toxicity, environmental pollution and residues in animal products. Integrated parasite management makes use, where possible, of biological and mechanical control methods, of acquired and innate host resistance, and of genetical, ecological, sanitary and regulatory procedures, although chemical control can seldom be entirely abolished. Cost-effectiveness and sustainability in all respects are of primary importance.

This review presents short information on the present status and some future perspectives of vaccination against parasitoses of domestic animals. For the control of such parasitoses in some European countries only a few vaccines are registered: Paracox and Livacox (for coccidiosis in chickens), Toxovax (for toxoplasmosis in sheep), Pirodog (for babesiosis in dogs) and Dictol (for dictyocaulosis in cattle). These are live vaccines containing attenuated parasites, except Pirodog. As a world-wide innovation in 1994 a vaccine against ixodid tick infestation (Boophilus microplus) in cattle was marketed in Australia under the trade name TickGARD which contains a recombinant protein antigen. A recombinant vaccine against Taenia ovis cysticercosis in sheep was developed in Australia/New Zealand but has not yet been registered. The development of vaccines against further parasitoses of domestic animals is a fascinating and promising field. Present research activities are focussed on molecular antigen vaccines and vector vaccines. First reports (for example regarding leishmaniosis and malaria) indicate that nucleic acid vaccines represent a new potential of development.

Chemical methods continue to be the primary means for control of parasites in medicine and veterinary medicine. Environmental concerns are raised mainly in the control of free living stages of parasites, intermediate hosts, vectors of diseases and in control of sanitary pests. Similarly, the type of application in case of sheep-dips and spraying of acaricides and insecticides in poultry houses against chicken mites is problematical. The now available bolus with ivermectin may cause a stronger impact on the cattle dung fauna and subsequent degradation of the dung as already known after injection and pour on.

In the past, parasite control in domestic animals has relied mainly on the use of drugs and pesticides. Although these compounds are still of great importance in the prevention and treatment of parasitic diseases, in recent years the emphasis has shifted to a more flexible approach, integrating various other control measures. The main reasons for this change are:--development of parasite resistance to the compounds used; --reduced development of new compounds to overcome resistance (increasingly more stringent regulations on toxicity and residues, resulting in very high research and development costs, insufficient return for industry because of the short life-span of new products due to resistance and because the market for compounds in developing countries is limited and poor);--increasing cost of new products for consumers;--problems associated with toxicity, environmental pollution and residues in animal products. Integrated parasite management makes use, where possible, of biological and mechanical control, of acquired and innate host resistance, and genetical, ecological, sanitary and regulatory procedures, although chemical control can seldom be entirely eliminated. Cost-effectiveness and sustainability in all respects are of primary importance.

A cost-benefit model is developed to estimate the costs of major parasites to Australian livestock industries and to evaluate the benefits from improving parasite management. The model disaggregates the Australian livestock industries into agro-climatic regions and various stock classes to estimate the total treatment and production loss costs of major parasites. Experimental trials and a computer simulation model are used to estimate the productivity of livestock under different treatment regimes. Using the model, the economic costs inflicted by cattle ticks, sheep gastrointestinal worms, sheep lice and sheep blowflies are discussed and the farm profitability resulting from improved sheep roundworm management is assessed.

Transhumance is defined as 'seasonal moving of livestock to regions of different climate'. It is an integral part of livestock production in many parts of the world and takes several forms including moving of livestock from lowland to mountainous pastures or from dry to humid areas. The impact of transhumance on parasite populations of livestock and on parasite control is described, mainly using examples from Europe. The epidemiology of trichostrongylidosis of cattle, mainly caused by Ostertagia ostertagi and Cooperia oncophora, is characterised by prolonged survival of overwintered infective larvae until the end of June. Cattle moved to such contaminated pastures in a transhumant grazing system are exposed to these larvae and may be protected, during the second half of the grazing season until autumn, by a late application (June/July) of an intraruminal drug-release device. Community pastures used in a transhumant system with mixed grazing of young cattle originating from various farms may enhance transmission of dictyocaulosis. Therefore, specific prophylactic measures are required. Hill sheep nematode populations may differ from those in lowland sheep in that Haemonchus contortus generally plays a minor role in hill sheep in which Ostertagia circumcincta and Nematodirus spp. predominate. Infections with Fasciola hepatica and Dicrocoelium dendriticum can be acquired on mountainous pastures by cattle, sheep and other livestock grazing in a transhumant system as intermediate hosts of these parasites may find suitable habitats in these regions. There is evidence that in the prealpine and alpine area both parasites are mainly transmitted in two-season cycles. Further examples for the impact of transhumance on parasite-host inter-relationships include cysticercosis in cattle, echinococcosis, psoroptic manage in sheep, tick-borne fever of cattle, and hypodermosis in cattle. These are described and discussed.

The kinetic and dynamic disposition of endo- and ectoparasiticides in livestock in relation to development of resistance is examined. Based on the modes of action of antiparasitic drugs, maximum activity necessitates that the parasite be exposed to 'toxic' concentrations for as great a duration as possible. In contrast, exposure to non-lethal discriminating drug concentrations has a significant potential to promote the development of resistance. Orally administered anthelmintics quickly associate with particulate digesta in the rumen; their subsequent desorption from particulate matter as it vacates the rumen maintains the duration of metabolite availability. The flow rate of digesta increases with feed intake and the presence of gastrointestinal parasites, and together with other parasite-induced physiological changes to the gut, contributes to reduced duration of drug availability. The potential for orally administered drugs to bypass the rumen, due to closure of the oesophageal groove, exacerbates the effect. Once absorbed, the metabolite concentration with time profile progressively decreases, the rate depending upon the chemical nature of the drug and the type and condition of the host into which it was administered. The greater hepatic activity of goats speeds drug elimination, the lower dose equivalent availability increases the potential for generation of drug resistance in parasites of goats as compared to sheep. Parasites whose resistance is generated in goats may be then transferred to sheep. Similar distribution/elimination kinetics apply to topically administered insecticides of sheep. The progressively reducing concentrations expose ectoparasites to discriminating drug levels, again contributing to the development of resistance. It is anticipated that a greater understanding of the physiological/pharmacological effects which are described in this review will permit the more efficient use of existing and future antiparasitic drugs.

Avermectins, a relatively new class of broad spectrum pesticides, are used widely to control livestock parasites. Following treatment, avermectins are eliminated in the livestock faeces where they also have a wide range of harmful affects upon certain characteristic insects that breed in dung, few of which are pests, and many of which are beneficial. The effects range from acute toxicity in larvae and adults, through disruption of metamorphosis, to interference with reproduction. Different methods of drug administration lead to different concentrations of drug residues in the faeces, which in turn influence the responses of non-target organisms. Higher Diptera are particularly sensitive to drug residues and show a wide range of responses from death of larvae to developmental abnormalities in the adults. Larvae and immature adults of Coleoptera show some mortality in the dung of recently treated animals, while delayed effects upon reproduction and physiology have been observed in adults feeding on dung at longer post-treatment times. Although the impact of lethal doses has been described in some species, the effects of sub-lethal doses have hardly been recognised at the present time. Correlated with the deleterious effect upon dung-breeding insects, a retardation in the rate of loss of biomass of dung pats from avermectin-treated cattle has been observed following the various forms of drug administration. Differences in methodology, inappropriate statistics, and/or extremes of climatic conditions prevailing at the time of testing, explain the results of those studies where such delays have not been observed. It is short-sighted to consider only dung dispersal in relation to avermectin usage, a practice that overlooks the impact on the insects themselves and their diverse roles in pastureland ecology.

Diagnosis of parasitic diseases requires highly sensitive and specific tests. In many cases the identification of parasites concerns their epidemiology and it is important to distinguish between species and subspecies. Conventional techniques including serology and microscopy do not always meet these requirements. The principle of nucleic acid probes is that a specific sequence of the parasite's DNA is isolated and used in a hybridisation assay to identify homologous parasite DNA from infected material. Since DNA normally remains the same during every stage of the parasite's life cycle this technique has many applications. The use of DNA diagnostics in the identification and differentiation of certain animal parasites is discussed.

This review of internal parasitic diseases discusses methods of immune diagnosis, immune mechanisms of the host, and immunoprophylaxis against both protozoan and metazoan parasites of livestock. The limiting factors for immunodiagnosis are specificity and whether the host animals respond sufficiently to produce detectable serological responses. Because the array of antigens is so complex, the method of choice for helminths is to use excretory/secretory products of the parasite as antigens for microplate ELISA. Similarly, for protozoa, immunodiagnosis is facilitated by using a few, selected, immunodominant antigens rather than extracts of whole parasite. However, serodiagnosis does not always identify parasitised animals especially in the young, malnourished or sick host. Similarly, parasites may themselves modulate the response of the host and remain serologically undetectable. The production of recombinant, pure, parasite proteins is already facilitating diagnostic serology for several parasite species and, using recombinant DNA probes, it is now possible to distinguish inter- and intra-species differences. The central role of inflammatory cytokines, the regulatory proteins produced by activated T helper cells, in modulating both protective and potentially damaging inflammatory responses is discussed. Finally, the genetic control of the immune response and its relevance to immunoprophylaxis is considered. Several interesting developments in the production of sub-unit vaccines and the potential methods of delivery are appraised.

The parasitical diseases are among the game diseases the most wide spread. Since the interest of keeping game healthy is of great universal importance, the problem of the prevention of serious losses caused by parasites arises. Today this is in many cases possible by the exploration of all present prophylactical and therapeutical avenues. The presupposition in this respect is the thorough knowledge of parasite and host. Only then antiparasitical drugs can be employed at the right time. Furthermore the biotop, the agricultural and the forestry conditions have to be considered. Although population losses caused by parasites can be very heavy, a game population can never be decimated so far that its continuance will be endangered. Owing to the hitherto existing knowledge a qualitative population regulation is not caused by the parasites. Detrimental effects with domestic animals caused by game parasites or vice versa in hunting grounds is certainly possible but dependent upon the species greatly different, and practically without essential meaning in Austria.

A survey about the important parasites and parasitic diseases of the fair game animals in the GDR is given. Here are of special importance: the coccidiosis of the hares, the sarcosporidiosis and the infection with lungworms and gastro-intestinal helminths of the wild ruminants and wildboars, the onchocercosis of the red deer and lastly the infection with skin warble, pharyngeal gad-fly larvae and louse-flies of the roe and red deer. The possibility of crosswise infection between domestic and game animals is discussed and the necessity of practicable ways in prevention and medication of the parasites is demonstrated.

Attempts to develop vaccines for protozoan and helminth parasites of livestock have been generally unproductive. Difficulties have been encountered in identifying antigens which induce protective immune responses and in obtaining sufficient quantities of antigens for vaccine trials. Use of monoclonal antibody and genetic engineering technologies provides the necessary tools to overcome these problems. Application of these technologies in animal parasitology should provide for significant breakthroughs in vaccine development.

The paper presents a selected review of the epidemiological analyses performed in recent years (1984-1988) in the Institute of Malattie Infettive, Profilassi e Polizia Veterinaria of the University of Bologna on animal parasitoses, with special reference to the evaluation of some risk factors of bovine, swine and canine helminthoses, and to the validity of the coprological test for some parasites of the red fox.