[Parasite control in wild ungulates].
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Animals↗
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Results for “Parasite Control”
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[Use of drugs against significant parasitic diseases in domestic animals. I. Possibilities and principles of parasite control; cattle: piroplasmosis and coccidiosis].
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Animals↗
Teaching veterinary parasitology.
The history of parasitology and the teaching of veterinary parasitology in South Africa are reviewed briefly. Courses in veterinary parasitology are presented at the faculties of veterinary science at the University of Pretoria and the Medical University of South Africa as well as at the Pretoria Technicon. At the University of Pretoria, the three disciplines of veterinary parasitology, entomology, helminthology and protozoology, are covered in 330 core lectures; from 13 to 40% of the contact time is devoted to practical classes. Teaching veterinary parasitology is both labour intensive and costly, viz. R1700 (US$570) per student per annum. Such costs are justified by the R148.8 million (US$49.6 million) spent every year in South Africa on anthelmintics, ectoparasiticides and vaccines to control parasites. Veterinary parasitology is a dynamic subject and the curriculum must be revised regularly to incorporate new information. Because the parasite faunas are so diverse no single textbook can satisfy the requirements of the various institutions worldwide which teach the subject, with the result that extensive use is made of notes. In Australia and in Europe, ticks and tick-borne diseases are less important than they are in Africa; consequently insufficient space is devoted to them in textbooks to satisfy the requirements of the subject in African countries. Parasite control under extensive and intensive conditions is dealt with adequately at the University of Pretoria, but increasing emphasis will be given to small-scale farming systems, particularly if alternative food animals are to be kept.
Animals↗
Immunity and genetics: their relation to control of parasitic zoonoses.
Effective control of parasitic zoonoses will ultimately require a combination of several approaches, including hygiene/sanitation, pasture management, chemotherapy and immunoprophylaxis. Development of vaccines, and other approaches to improving protective immunity, require a detailed understanding of parasite immunogenicity and host immune responsiveness. It is increasingly recognized that there is considerable variation in both of these parameters, and that this variation is genetically determined. Recent studies in this area and the consequences for control are discussed.
Animals↗
The control of parasitic gastroenteritis of grazing cattle in Normandy, France using the morantel sustained release bolus.
The efficacy of the morantel sustained release bolus in controlling parasitic gastroenteritis in 153 first-season grazing cattle was assessed in three separate field trials conducted in Normandy, France. In each trial, comparisons were made on weight gain performance and parasitology data (faecal worm egg counts, herbage larval counts and- in two of the trials- worm counts from principal animals sacrificed at the end of the grazing season) when bolus treatment was given either at spring turnout or in mid-season in order to determine the optimum time for bolus administration. Cattle were allocated into three groups, each group maintained on a separate but equivalent paddock constructed from the division of a larger pasture. A morantel sustained release bolus was administered to one group of animals at the time of turnout and to a second group of animals in midsummer. The third group of animals in each trial remained nontreated. The effect of the treatment on the contamination of pasture, and parasite levels and weight gain of the principal trial animals was assessed. Similar results were observed in all three trials. Faecal worm egg counts were reduced during the first part of the grazing season in animals receiving the bolus at turnout compared with mid-season treated animals where egg counts followed a pattern similar to the controls until bolus treatment at which time counts abruptly dropped to a low level. Likewise, levels of infective larvae on pastures grazed by control and mid-season treated animals followed similar patterns, increasing to a high level in late summer, while larval levels on pastures grazed by early-season treated animals remained at low levels throughout most of the season. Serum pepsinogen levels, worm counts and weight gain reflected the results from faecal worm egg and herbage larval counts indicating that early-season treatment with the bolus provided the most efficient treatment time for controlling parasitic gastroenteritis throughout the grazing season. The overall mean weight gain advantage of the early-season bolus-treated animals over the controls was 37.2 kg (P less than 0.01) while the advantage of the mid-season treated animals over controls was 13.7 kg.
Animals↗
A model of non-specific immunity.
Though the importance of the non-specific immune response is well known, it has often been neglected in theoretical studies. Whereas adaptive or antigen-specific immune responses arise from the proliferation of clones of antigenic-specific cells to form populations sufficiently large to control the parasite, the non-specific response involves the activation of cells such as macrophages from a reservoir consisting of a fixed number of cells. In this paper, we use simple mathematical models to investigate the dynamics of the non-specific immune response to parasites. In particular we describe the conditions under which the non-specific immune response can clear a parasite, control a parasite, or merely reduce the growth rate of a parasite. We also show that non-specific response to concurrent infections of hosts with two parasites can lead to competitive exclusion of one of the parasites. The model incorporating non-specific immunity is then expanded to include specific immune responses. This more complex model, is used to investigate the relative roles of non-specific and specific immunity in dealing with parasites and shows that the non-specific immune system may control the density of parasites prior to the generation of specific immune responses which are capable of clearing them. Finally we show that the predictions of the models conform with results from published experiments on listeria infections.
Animals↗
Control strategies for ruminant and equine parasites to counter resistance, encystment, and ecotoxicity in the USA.
The need for improved parasite control strategies to conserve anthelmintic efficacy and to avoid drug-related problems are addressed. Recent surveys have revealed a trend for sole dependence on ivermectin by livestock owners in the USA, with little regard for epidemiologic-based strategies, or the annual rotation of unrelated anthelmintic groups. Innovative parasite control strategies for cattle, sheep, and horses in northern USA are presented. The importance of closer monitoring and more rational use of anthelmintics is stressed.
Animals↗
Parasitic bronchitis in goats and the possible use of Dictyocaulus filaria vaccine for its control.
Parasitic bronchitis is widely prevalent in migratory flocks of small ruminants in the northwest Himalayan regions of India. The prevalence data collected from 5554 goats, maintained in 31 villages in different agroclimatic regions of the Himalayas, showed that the prevalence of the disease in goats varied from 18.7 to 47.6% with an overall prevalence of 21.8%. Interestingly, 27.6% of goats maintained at an altitude of 2700-3900 m above mean sea level in Kargil (Jammu and Kashmir), where the climate is cold and dry for the major part of the year, were positive for the lungworm infections. The common lungworms observed were Dictyocaulus filaria, Protostrongylus rufescens, Varestrongylus pneumonicus and occasionally Muellerius spp. The kids were more susceptible to lungworm infections than adult goats. In experimental studies, it was seen that goats were more susceptible to Dictyocaulus filaria infection than sheep and two vaccine doses comprising 1000 and 2000 gamma-attenuated D. filaria (ovine strain) infective larvae conferred 97% protection in male Beetal kids against a homologous challenge dose of 4200 normal D. filaria larvae. The importance of simultaneous control of the disease in goats and sheep is discussed.
Animals↗
A mixed program for parasitic disease control.
In this paper we are concerned with the control of a parasitic disease by a permanent, time-continuous mixed program of vector reduction (reduction of the contact rate) and drug application. We shall use the model developed in [1] with two control functions: one for the reduction of the contact rate and another for the administration of drugs to the population. This model takes into account the possibility that there may by a certain fraction of the population which cannot be covered by any drug application. Optimal control policies for reduction of the contact rate and for the protected proportion of the population by drugs are derived by using Pontryagin's maximum principle. A cost-optimal strategy is deduced for the maintenance of the affected proportion of the population below a given level. Some numerical examples are computed.
Humans↗
Anthelmintic resistance and the future for roundworm control.
Anthelmintic resistance has emerged as the most important problem confronting the successful control of nematode parasites of grazing animals. Although the significance of the problem varies between, and within, countries and farming enterprises, there is little likelihood that it will disappear of its own accord. On the contrary, it is reasonable to assume that it will increase if there is no change in traditional methods of parasite control. Although progress is being made in non-chemotherapeutic methods of control, these are unlikely to provide any practical alternatives in the short-term future. Nor can the pharmaceutical industry be expected to solve the problem because of the long period and the exceedingly high costs involved in bringing a completely new class of drug on to the market. The answer must lie in carefully husbanding the currently available anthelmintics, by providing farmers with programs which give good levels of parasite control and maintain high productivity in animals with fewer anthelmintic treatments. To be enthusiastically adopted by farmers, the programs require a commitment by both research and advisory workers. Such success can be achieved, as exemplified by the "Drenchplan" and "Wormkill" programs in Australia. It behoves workers in all countries which have a significant grazing livestock industry, not only those with an existing resistance problem, to consider how such schemes could be implemented.
Animals↗
[New anthelmintics and new treatment systems for the control of parasitic diseases of cattle in pastures].
Advanced knowledge of the epizootiology of parasitic gastroenteritis and the introduction of new anthelmintics and new application systems allow new strategies to control parasites of cattle on pastures. Ideally, parasitic gastro-enteritis is prevented by evasive grazing, i.e. the animals are driven every two weeks to new and not yet contaminated pastures, and the application of anthelmintics is not necessary. Midsummer treatment is most effective when combined with a move to non-contaminated pastures (Weybridge dose and move system). Following the introduction of the slow-release-devices, the prophylaxis of parasitic gastro-enteritis became much easier. The device, which is usually called bolus, is administered before turnout and it results in an effective reduction of the infection risk throughout the grazing season. Treatment following 3, 6 and 9 weeks after turnout prevents the development of dangerous numbers of infective larvae on the pasture in the second half of the grazing season. This system is known as Glasgow model. The pulse-release boluses follow the same principle and they offer the advantage of application at turnout and of releasing the anthelmintic in full doses at intervals. Treatment at the beginning of housing is only necessary when measures to prevent parasitic gastro-enteritis during the grazing season were not sufficient. All strategic measures reduce the risk of lung worm disease, but they do not prevent lung worm infection completely. On farms with a high lung worm pressure, additional control measures may be necessary. In areas with high risk of liver fluke infection, treatment in July may reduce pasture contamination.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Use of an oxfendazole pulse release bolus in the control of parasitic gastroenteritis and parasitic bronchitis in first-season grazing calves.
The efficacy of the oxfendazole pulse release bolus system for the control of parasitic gastroenteritis and parasitic bronchitis in first-season grazing calves was evaluated in Belgium. Twenty-two calves were allocated to two groups. The calves in one group received a bolus at the time of turn out, while the other group remained untreated. The efficacy of the bolus was assessed by comparison of faecal worm egg counts, plasma pepsinogen concentrations, the antibody response to Ostertagia, Cooperia and Dictyocaulus species total plasma protein and albumin concentrations, and weight gains throughout the grazing season and the housing period. The oxfendazole pulse release bolus provided good control of parasitic gastroenteritis dominated by ostertagia. The effects of parasitic gastritis were greatly reduced as shown by the significantly lower values of serum pepsinogen and ostertagia antibody titres. The use of the bolus further reduced the adverse effects of parasitism as indicated by better liveweight gains and normal total plasma protein and albumin concentrations whereas in the untreated control group hypoproteinaemia and hypoalbuminaemia were observed. Most animals exhibited clinical signs of parasitic bronchitis at the end of the grazing season, and the bolus may not adequately control parasitic bronchitis in all cases at all times.
Animals↗
Scientists versus parasites: who are the winners? Molecular Understanding and Control of Parasitic Diseases: a Jacques Monod conference sponsored by the Centre National de la Recherche Scientifique, Roscoff, France, July 1-5, 1991.
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Antigens, Protozoan↗
Behavioural aspects of the control of parasitic diseases.
Human behaviour has been largely neglected in research on the parasitic diseases, in part because of the long-standing separation of the behavioural disciplines from the physical and biomedical sciences. Some of the reasons for the persistence of this "intellectual discontinuity" are discussed. The paper is principally concerned with the prospects for greater use of the methods and orientations of the behavioural sciences in parasitic disease research and control programmes. Behavioural research tends to fall into two categories employing, on the one hand, survey research and epidemiological methods and, on the other, participant observation and interviewing in depth. These approaches are shown to be complementary-equally useful and necessary. Various categories of health-related behaviour and kinds of research objective are reviewed in the following sections. Special attention is given to psychosocial cost-benefit studies, to analyses of control sectors, and to the formulation of a control philosophy. Finally, some specific behavioural research needs are discussed for some of the parasitic diseases of priority in the UNDP/World Bank/WHO Special Programme for Research and Training in Tropical Diseases-schistosomiasis, filariasis, American and African trypanosomiases, and malaria.
Attitude to Health↗
Synthesis and secretion of proteins by released malarial parasites.
Controlled mechanical homogenization of Plasmodium falciparum-infected erythrocytes releases parasites of a quality sufficient for studying the export of newly synthesized plasmodial proteins. Protein synthesis occurs within intact released parasites as defined by resistance of acid-insoluble incorporation of radiolabel to high levels of exogenously added EDTA, hexokinase, and RNaseA. While exogenously added ATP and erythrocyte cytosol were not essential for biosynthetic activity at levels comparable to that seen in infected erythrocytes, the addition of an extracellular ATP regenerating system (ARS) stimulated the synthesis of parasite proteins. Conversely, parasite viability and biosynthetic activity are decreased by the addition of a non-hydrolyzable ATP analogue (ATP gamma S), ADP, or ATP in the absence of a regenerating system. These data suggest a metabolic interdependence between extracellular energy metabolism and biosynthetic functions within the parasite. The export of a predominant subset of proteins was retarded in the presence of Brefeldin A, indicating the existence of a classical secretory pathway characteristic of that seen in higher eukaryotic cells. Interestingly, a Brefeldin A-insensitive component of export was also consistently observed; this may suggest the existence of an additional alternative secretory mechanism in malaria.
Adenosine Triphosphate↗
Regulation of parasite populations. A general theory of the epidemiology and control of parasitic infections.
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Animals↗
Evaluation of the morantel sustained release trilaminate in the control of parasitic gastroenteritis in first season grazing cattle.
A novel intraruminal bolus developed for the sustained delivery of the anthelmintic morantel tartrate was evaluated in the seasonal control of parasitic gastroenteritis in first season grazing calves. The morantel sustained release trilaminate is a trilaminate sheet consisting of a central lamina of a morantel tartrate/ethylene vinyl acetate matrix coated on both sides with a thin impermeable layer of ethylene vinyl acetate. A symmetrical pattern of circular perforations punched through the device controls the release of morantel. Administration of the trilaminate to calves significantly reduced their faecal egg output compared with untreated controls and thus reduced pasture larval contamination. Clinical parasitic gastroenteritis was prevented in the treated calves and there were significant reductions in their worm burdens compared with the untreated control calves both during and at the end of the grazing season. The control of parasitic gastroenteritis resulted in a significantly greater (P less than 0.0001) weight gain, of 45 kg, by the treated calves.
Animals↗
Epidemiologic approach to the control of sheep nematodes.
Epidemiologic approaches to parasite control, with reduced reliance on the use of anthelmintics, were studied in 6 groups of weaned lambs and 4 groups of suckling lambs grazing fertilized pastures. Strategies tested included prophylactic treatments in the spring, provision of safe pastures, treat-and-move strategies, and winter (prelambing) treatment of ewes. Suppressive treatment with a non-benzimidazole drug was used as a production yardstick against which the epidemiologic approaches were judged. Suppressive treatment with a benzimidazole drug was used to determine the drug resistance status of the flock. The success of each strategy was evaluated by measurements of body weight, wool growth, fecal egg counts, pasture larval counts, and total worm burdens. Prophylactic treatments in the spring were just as effective as suppressive treatments throughout the entire grazing season and resulted in significant (P less than 0.001) increases in weight gain. Effective parasite control also was obtained by moving ewes and lambs to safe pastures (low infectivity) in May, and resulted in significant (P less than 0.001) increases in weight gain. A treat-and-move strategy led to significant (P less than 0.001) increases in weight gain until September, but then a loss of weight in October, suggesting the need for a double treat-and-move strategy in the case of late-marketed lambs. The value of winter (prelambing) treatments for ewes also was demonstrated. Suppressive treatments with a benzimidazole drug confirmed the presence of benzimidazole-resistant nematodes.
Animals↗