Abnormal swellings in the tegument of the acanthocephalan parasite Metechinorhynchus salmonis.
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Acanthocephala↗
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Results for “Helminthiasis”
Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.
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A clinical and parasitological survey of the Tristan da Cunha islanders.
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Chorioretinitis↗
Immunodiagnosis of parasitic zoonoses: comparative efficacy of three immunofluorescence tests using antigens purified by affinity chromatography.
Three immunofluorescent antibody assays were developed during this study: the direct (DFAT) and indirect (IFAT) fluorescent antibody tests using frozen worm sections, and the cyanogen bromide indirect fluorescent antibody test (CNBr-IFAT) using helminth antigens purified by affinity chromatography bound on to commercially prepared CNBr-Sepharose 4B beads. Purified antigens used in the CNBr-IFAT gave greater specificity and sensitivity than either the DFAT or IFAT. Dirofilaria immitis, Toxocara canis, Angiostrongylus cantonensis and Ascaris lumbricoides infections were studied in natural and zoonotic hosts and in rabbits immunized with antigens prepared from these parasites. In addition, a serological survey of Aboriginal Australians from Queensland was made.
Animals↗
New opportunities for the diagnosis and control of animal diseases in the tropics.
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Africa↗
Indirect effects of soil and water on animal health.
Some variations in animal health among geographic areas are associated with variations in soils, water supplies or soil parent materials. Geochemical bases for health problems arising from essential nutrient element deficiencies or from toxic levels or imbalances of several elements are widely recognized. Less attention has been directed to the possibilities of geochemical influences upon regional differences in health resulting from pathogens, parasites, mycotoxins and poisonous plants. This review is an effort to collect and interpret such evidence as has been published on the subject since Louis Pasteur's original observation associating soil character and probability of anthrax.
Animal Diseases↗
Molecular aspects of drug resistance in parasitic helminths.
Parasitic helminths (worms) cause serious infectious diseases in humans and animals. As control of these infections relies mostly on chemotherapeutics, the anthelmintics, resistance has developed against most of these drugs in several parasite species. These resistant parasites are being used to elucidate the molecular mechanisms of drug action.
Animals↗
Effect of pregnancy and lactation upon infection.
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Animals↗
A compiled computer program for assisting the diagnosis of gastrointestinal helminths of humans and animals.
A compiled computer program for assisting the diagnosis of gastrointestinal helminths in fecal examinations of humans and animals is described. The characteristics of this program which distinguish it from previous similar programs are that it does not require specific software, it does not need a lot of computer memory, and it covers both humans and animals, making it easier to use.
Animals↗
Parasite-dependent modulation of acute inflammation (a review).
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Acute Disease↗
World Association for the Advancement of Veterinary Parasitology (W.A.A.V.P.) guidelines for evaluating the efficacy of anthelmintics in ruminants (bovine and ovine).
During the 8th International Conference of the World Association for the Advancement of Veterinary Parasitology (W.A.A.V.P.) held in Sydney, Australia, in 1977, President S. Gaafr appointed a committee to prepare international guidelines for evaluating the efficacy of anthelmintic products. The goal was to develop uniform testing standards and registration requirements to expedite the testing and approval of effective products with a minimum of labor, money, and experimental animals without sacrificing scientific validity. Achievement of such a goal would mean that data from investigators in one country could be used in registering drugs in another country. These guidelines, which were approved by the membership at the general meeting of the 9th International Conference of the W.A.A.V.P. on July 16, 1982 in Budapest, Hungary, are only a beginning in the development of uniform international methods for testing the efficacy of anthelmintics. We now propose that they be used by the scientific community recognizing that, at this time, these guidelines have not been officially reviewed or accepted by any government regulatory authority. Investigators are encouraged to evaluate this document critically and to recommend modifications promptly to the Committee so that they may be incorporated in these guidelines before the 10th International Conference to be held in Perth, Australia in 1983.
Animals↗
Critical tests in equids with fenbendazole alone or combined with piperazine: particular reference to activity on benzimidazole-resistant small strongyles.
Seven critical tests in equids were conducted with single doses of fenbendazole (5 mg kg-1) alone (Panacur--American Hoechst, Somerville, NJ); (2 tests with paste and 1 with suspension formulation) or in combination with piperazine (American Hoechst); (40 mg base kg-1); (4 tests with paste formulation). The main purpose of the tests was evaluation of activity against benzimidazole-resistant small strongyles (Cyathostomum catinatum, Cyathostomum coronatum, Cylicocyclus nassatus, Cylicostephanus goldi, and Cylicostephanus longibursatus). Natural infections of 2 populations of benzimidazole-resistant small strongyles were evaluated; 1 was population B in 2 horses and the other was population S in 5 ponies. Removal of the 5 species of population B was 49-91% in the animal treated with fenbendazole paste alone and 100% (4 of these species present) in the animal treated with the combination. For population S, 2 of the 5 resistant species were present in small numbers in 1 animal treated with fenbendazole paste alone and all were removed; the 1 animal receiving fenbendazole suspension alone had removals of 0-70% for the 5 benzimidazole-resistant species. Also for population S, the 5 resistant species were present in 2 animals treated with the paste combination and removal was 98-100% and of 4 of the 5 resistant species in 1 animal, removal was 76-99%. Removal of large strongyles (Strongylus vulgaris and Strongylus edentatus) was 92-100% for fenbendazole paste alone or in combination with piperazine in the 5 infected animals. For Oxyuris equi, present in 1 animal treated with the combination, there was 91% removal of immature and 100% removal of mature specimens. There probHably was no activity by fenbendazole alone or the combination against bots, tapeworms, and parenteral stages of S. vulgaris and S. edentatus. The combination may have had some activity against immature Habronema spp. and mature abronema muscae.
Animals↗
Potential problems associated with the controlled release of anthelmintics in grazing animals.
A high, constant and sustained release of drug appears to be a major requirement to avoid a late season rise in pasture infectivity that may result in production losses in calves in autumn or Type II osteragiasis in the following spring. The timing of administration is of crucial importance and will vary in regions of different epidemiology, such as between northern and southern United States. Lack of a standard and reliable technique for pasture larval counts has resulted in some negative or erratic results which are open to question. Although controlled release anthelmintics offer advantages of convenience, a comparison of the economic benefits at present favours prophylactic treatment of dairy heifers with conventional anthelmintics 3 and 6 weeks after spring turnout in northern regions of the Northern Hemisphere. There is a serious risk that boluses based on controlled release by diffusion will behave like slow decaying insecticides and select strongly for drug resistance, especially if farmers administer them in succession throughout the grazing season. There are, however, 2 features in the design of a controlled release device that in theory may minimize the risk of rapid selection for resistance: a high and constant release of anthelmintic followed by a rapid decline to zero as the device becomes exhausted. Under these conditions, the device may even prolong the useful life of an anthelmintic to which resistance has already developed. This paper was presented at Pfizer Symposium on The Application of Sustained Release Anthelmintic Dosage Forms in the Control of Parasites in Grazing Animals at the World Association for the Advancement of Veterinary Parasitology (W.A.A.V.P.) 10th International Conference, 18-20 August 1983, Perth, W.A., Australia.
Animals↗
Application of hybridoma technology to the diagnosis of parasitic disease.
Recent applications of hybridoma-derived monoclonal antibodies to the diagnosis of parasitic disease are reviewed. Diagnostic tests, utilizing monoclonal antibodies, have included radioimmunoassay (RIA) and enzyme-linked immunosorbent assay (ELISA) techniques to detect parasite antigen in host tissues and body fluids and circulating host antiparasite antibody. In general, the use of monoclonal-derived reagents has greatly increased the specificity of diagnosis by eliminating cross-reactions between closely related parasite species, without suffering a significant loss of sensitivity.
Animals↗
Controlled release technology for the control of helminths in ruminants.
Release rates from controlled release devices are determined by the device itself and thus are accurate, reproducible and predictable, whereas in general, prolonged or slow release systems are sensitive to environmental conditions. Diffusion and dissolution are the principal means of achieving controlled release. A diffusion system is specific for the active ingredient and release rate decreases proportionately to the square root of time because of a decreasing concentration gradient or an increasing diffusion path. In dissolution systems, the choice of matrix determines the rate of dissolution and release rates are linearly related to the area of dissolution which can be maintained constant. Consequently, this system has general application, a sharp cut-off point and can be used for more than one ingredient simulatenously. Potential disadvantages of controlled release technology centre on unacceptable tissue residues and parasite resistance to the chemicals used. Advantages include, the ability to programme the release of compounds to achieve specific effects for various periods, decreasing the frequency of dosage and increasing the choice of compounds for the control of parasitic infections. Sufficient epidemiological information should be available before controlled release technology is implemented. Existing anthelmintics and control strategies can be used to achieve an enhanced, but expected result, e.g., prolonged reduction in pasture contamination to protect both ewes and lambs. In future it should be possible to devise compounds and strategies appropriate to the unique features of controlled release technology, e.g., compounds which interrupt or inhibit the growth and development of parasites. Environmental impact should be low because of the specific effect and low dosage of the chemical used.
Animals↗
Interaction of host physiology and efficacy of antiparasitic drugs.
Antiparasitic drugs must be conducted to the parasite by the host and are therefore subject to physiological and biochemical processes in the host. Usually the efficacy of an antiparasitic drug will depend on a toxic concentration being presented to the parasite for sufficient time to lead to irreversible damage. Because many drugs are, in part, absorbed and transported to the site of the parasite by the circulatory system the area under the plasma concentration curve (AUC) may reflect availability of drug to the parasite and likely efficacy. A number of host physiological factors affect the AUC. Many anthelmintics are given orally as solids. Some absorption occurs in the rumen of ruminants, but many heterocyclic compounds such as the benzimidazoles require the low pH of the abomasum or gastric stomach to render them soluble. Certain disease states, including gastrointestinal parasitism, can cause the gastric pH to rise. This may in turn reduce solubility and absorption with resultant faster rate of excretion, particularly when accompanied by diarrhoea, and a reduced AUC. Once the anthelmintic has been absorbed, after oral or systemic administration, it is usually rapidly transported to the liver. The liver and adipose tissue may store the drug, releasing it over a period to produce a sustained effect as occurs with ivermectin, or it may rapidly metabolise it. A few anthelmintics, such as febantel, probably need to be metabolised in order to become active. However, more frequently the liver is involved in oxidation or reduction, followed by conjugation with sulfate, glucuronide or glutathione to render the drug more polar, to increase its molecular weight, inactivate it and facilitate its excretion. The rate of metabolism has been found to vary considerably between species and thus different dose rates and treatment are often required to achieve adequate antiparasite activity, with species such as deer, cattle and probably goats metabolising some anthelmintics faster than sheep. Some interesting possibilities for altering the absorption and metabolism of anthelmintics by the host may allow improved efficacy and reliability of antiparasite activity without necessarily increasing the dose rate of anthelmintic.
Animals↗
New methods of drug application for control of helminths.
Several new ways have been developed of delivering anthelmintics to ruminants aimed particularly at reducing labour. For single doses, these include a semi-automatic rumen injector for giving insoluble drugs to cattle more conveniently and efficiently than by oral dosing, and the dermal application of levamisole which is, however, subject to seasonal variation in absorption. Sustained administration offers potentially a high level of preventive control but carries a greater risk of developing drug resistance. Even with the best available methods of group administration in feed supplements or drinking water, there remains some uncontrollable variation in individual intake. Intraruminal sustained release devices largely overcome this problem and constitute the most important new technology. They are represented at present by the commercially successful morantel sustained release bolus, and the more versatile Laby capsule which is under development for anthelmintic delivery. Other new applications include the possible development of synergists, potentiators and drug combinations, the special features of drugs which bind strongly to plasma proteins, and the new possibilities offered by a drug highly effective against all stages of Fasciola hepatica. In the general approach to anthelmintic application in helminth control, there have been advances in knowledge of helminth population biology which can lead to better timing of strategic dosing programs, which show that single treatments can have persistent benefits without a simultaneous reduction in infection rate, and which question the conventional view that control schemes require the treatment of all animals in the group.
Administration, Oral↗
A method for the interpretation of parasite egg counts in faeces of sheep.
A new method for the interpretation of strongyloid egg counts in faeces in sheep flocks is proposed. The "Flock Parasitism Index" (FPI) is based on three epizootiological concepts: extent of parasitism, distribution of its intensity, and risk of pasture contamination by eggs. In the estimation of FPI from a number of faecal samples from different animals in a flock, the percentage of parasitized sheep and the distribution of parasitized animals of the sample into the classical categories of "low", "moderate" and "high" from the number of eggs per gram of faeces (EPG) and the arithmetic mean of EPG of the sample are considered. The pathogenic and epizootiological importance of each one of the "low", "moderate" and "high" categories are considered to be 0.1, 0.5 and 1, respectively. From the relationship between EPG and worm burdens, probabilities for "low", "moderate" and "high" distributions are calculated, and from the percentages of worm burdens estimated and their levels of confidence at 95% it is suggested that values of FPI equal to 2.0 must be considered as the limit of parasitism where economic losses are tolerable.
Animals↗
World Association for the Advancement of Veterinary Parasitology (W.A.A.V.P.) guidelines for evaluating the efficacy of anthelmintics in swine.
As a follow-up to a previous guideline publication on efficacy evaluation of anthelmintics in ruminants, an expert group of the World Association for the Advancement of Veterinary Parasitology presents similar guidelines for the testing of anthelmintics in swine. The goal of the guidelines is to develop uniform testing standards and registration requirements. Data obtained from investigations according to the guidelines should be internationally accepted in the registering of drugs. Further, the use of the guidelines may contribute towards reducing costs, labor and the number of experimental animals used for drug testing.
Animal Feed↗