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PubMed2000

Nematode parasite control practices of sheep and goat farmers in the region of Trikala, Greece.

Information concerning worm control practices of sheep and goat farmers in the region of Trikala (central Greece) was collected through a questionnaire survey by visiting farms and interviewing farmers. Questionnaires from 57 farmers residing in 23 rural communities were collected. Anthelmintics were used by 89% of the farmers. On average, lambs, kids and goats were treated once annually, while sheep were treated either once or twice annually. Only 2% of farmers reported treatment of animals with anthelmintics when moving to new pastures. The most common broad-spectrum anthelmintics used were those belonging to the benzimidazoles and probenzimidazoles. Fifty nine percent of the farmers used the same anthelmintic group for 3 or more years and 34% used two or more anthelmintic groups in the same year. Almost all farmers reported estimating live weights for calculating anthelmintic doses through visual perception on the basis of an average weight (96%). Tablets and boluses were the most preferred anthelmintic formulation used by 96% of farmers. The selection of an anthelmintic was based for 58% of farmers on recommendation by a veterinarian and for 39% of farmers on the cost of the drug. The most common occasions for deworming the animals were at turn out (86%) and after parturition (31%). Only 6% of farmers reported deworming new animals before introducing them onto the farm. Farmers preferred to seek information about the use of anthelmintics and worm control strategies from veterinarians (63%) and other farmers (37%).

Animal Husbandry↗
PubMed1999

Integrated and biological control of parasites in organic and conventional production systems.

Organic and other non-intensive animal production systems are of growing importance in several countries worldwide. In contrast to conventional farms, parasite control on organic farms is affected by several of the prescribed changes in management e.g. access to the outdoors in the summer and in most countries, a ban on preventive medication, including use of anti-parasiticides. Organic animal production relies heavily on grazing, and pasture or soil related parasites are thus of major importance. Several studies in northern temperate climate have indicated that outdoor production of pigs, primarily sows, and laying hens results in heavier and more prevalent helminth infections compared to conventional intensive production under indoor conditions. In organic dairy cattle, parasitic gastroenteritis in heifers may be more prevalent. In a short to medium term perspective, integrated control may combine grazing management with biological control using nematophagous micro-fungi, selected crops like tanniferous plants and on conventional farms, limited use of anti-parasiticides. At present, the non-chemotherapeutic control of pasture related infections is based mainly on grazing management strategies. Preventive strategies, where young, previously unexposed stock, are turned out on parasite-free pastures, can be used for grazing first season dairy heifers and in all-in-all-out poultry production. Evasive strategies aim at avoiding disease producing infections of a contaminated area by moving to a clean area and may be relevant for ruminants and pigs. In cattle, effective control of nematodes can be achieved by repeated moves of the herd or alternate grazing with other species. High stocking rates seem to be an important risk factor. In pig production, the effect of paddock rotation on parasite infections is largely unknown and studies are warranted. Control of nematodes by larvae-trapping fungi, or perhaps in the future by egg-destroying fungi, looks promising for ruminants and certain monogastric animals but delivery systems and practical dosing regimes integrated with grazing management have to be developed. In conclusion, good prospects are expected for acceptable parasite control without a heavy reliance on anti-parasiticides through integration of the above mentioned procedures but future studies are needed to confirm their efficacy under practical farming conditions.

Animal Husbandry↗
PubMed1994

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↗
PubMed1999

International approaches to the concept of integrated control of nematode parasites of livestock.

Livestock production systems throughout the world are under severe and sustained pressures. These are diverse and multi-factorial, ranging from the need to redress the oversupply of livestock commodities from the protected industries of the industrialised world, meeting animal welfare expectations, attempts to ease animal-induced land degradation and pollution, and competition with alternative products. As a consequence, funding for research to the ruminant livestock industries has been contracting universally. This applies particularly to research on those diseases of grazing livestock that are not zoonotic, threats to trade, or major "killer" diseases. Gastrointestinal helminths fall outside these priorities. The last decade has witnessed a major contraction throughout the world in the number of research centres and staff involved in applied veterinary parasitology research. This coincides with a time when these livestock industries need the most help. Resistance to anthelmintic drugs amongst the major nematode parasites of sheep and goats has now reached alarming proportions throughout the world and threatens the future viability of continued small ruminant production in many countries. Anthelmintic resistance is also increasing in the important nematode parasites of cattle. Also, this time coincides with the apparent reduction in the discovery and development of entirely new anthelmintic products by the pharmaceutical industry. As a consequence, those remaining researchers and extension personnel who have the responsibility of providing support to the ruminant livestock industry, are showing innovation and lateral thinking in ways to combat the perennial problem of internal parasites in grazing livestock. There are a number of excellent examples of parasite-control schemes, which do not rely entirely on anthelmintic treatment. These are now being supplemented with some exciting novel approaches to dealing with particularly pressing parasite problems. Also there is a move towards the development of true integrated approaches in the control of nematode parasites of livestock, which employ several of these methods when appropriate. This proves that as far as worm control in livestock is concerned, the old adage "necessity is the mother of invention", holds true.

Animal Husbandry↗
PubMed1996

[Integrated control of tropical parasitic diseases in animals].

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.

Animals↗
PubMed1991

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↗
PubMed1999

Treatment and control of gastrointestinal parasites.

Routine anthelmintic treatments are one of the most important components of an equine wellness program used by horse owners and veterinarians today. Thirteen different compounds are available in the United States in the treatment of gastrointestinal parasites, most of which are available over the counter. As a result, there is a decreased reliance on the veterinarian to perform routine tube dewormings. Therefore, the future of the veterinarian's role in the management of gastrointestinal parasites is likely to be in the consultation and design of parasite control programs. With this in mind, this article covers all of the equine anthelmintics and their clinical applications.

Animals↗
PubMed2001

The role of molecular biology in veterinary parasitology.

The tools of molecular biology are increasingly relevant to veterinary parasitology. The sequencing of the complete genomes of Caenorhabditis elegans and other helminths and protozoa is allowing great advances in studying the biology, and improving diagnosis and control of parasites. Unique DNA sequences provide very high levels of specificity for the diagnosis and identification of parasite species and strains, and PCR allows extremely high levels of sensitivity. New techniques, such as the use of uniquely designed molecular beacons and DNA microarrays will eventually allow rapid screening for specific parasite genotypes and assist in diagnostic and epidemiological studies of veterinary parasites. The ability to use genome data to clone and sequence genes which when expressed will provide antigens for vaccine screening and receptors and enzymes for mechanism-based chemotherapy screening will increase our options for parasite control. In addition, DNA vaccines can have desirable characteristics, such as sustained stimulation of the host immune system compared with protein based vaccines. One of the greatest threats to parasite control has been the development of drug resistance in parasites. Our knowledge of the basis of drug resistance and our ability to monitor its development with highly sensitive and specific DNA-based assays for 'resistance'-alleles will help maintain the effectiveness of existing antiparasitic drugs and provide hope that we can maintain control of parasitic disease outbreaks.

Animals↗
PubMed1983

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↗
PubMed1994

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↗
PubMed1993

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↗
PubMed1994

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↗