Biotechnology in the development of vaccines for animal parasites

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.     

Ovine helminthosis, a major health constraint to productivity of sheep in Ethiopia

Small ruminants represent an important component of the Ethiopian livestock production system, providing 12% of the value of livestock products consumed at the farm level and 48% of the cash income generated. Ethiopia is second in Africa and sixth in the world in terms of sheep population. The country has, however, benefited little from this enormous resource owing to a multitude of problems, disease being the most important. Disease alone accounts for mortalities of 30% in lambs and 20% in adults. Productivity losses attributable to helminth parasites are often substantial. A loss of US $ 81.8 million is reported annually due to helminth parasites. In a country confronted with challenges of an ever-rising human population and food shortage, such enormous losses caused by helminth parasites, 'the silent predators', are intolerable. Therefore, helminth control should receive special attention in poverty reduction strategies through improved productivity of livestock if the present and future challenges of food shortage are to be addressed. Productivity loss due to helminth infections can be substantially reduced through implementation of effective disease control strategies, which require an understanding of the epidemiology and ecology of parasites and parasitic infections under local conditions. This paper reviews extensive evidence demonstrating that helminthosis is a major constraint to productivity of sheep in Ethiopia. It also discusses epidemiology and ecology of major helminth parasites in the country and suggests strategies for improved control in various agro-ecological zones and production systems.     

Monoclonal antibody technology in the development of vaccines for livestock parasites

Vaccination against animal parasites offers an alternative to chemotherapy for the control of losses due to morbidity and mortality. However, only a few vaccines are currently available, and these are based on controlled infections with living parasites. Further advancement in the development of defined vaccines against parasite infections has been hindered by incomplete knowledge of the immunological relationship between the host and the parasite. The advent of monoclonal antibody technology has provided a powerful new tool for the identification and isolation of parasite antigens. Exploitation of this technique in veterinary parasitology has greatly facilitated progress toward the development of vaccines against several animal parasites.     

Evaluation of efficacy expectations for novel and non-chemical helminth control strategies in ruminants

The interest in novel methods of controlling helminth infections in ruminants is driven primarily by the development of parasite resistance to currently available anthelmintics. While the purpose of anthelmintics is to achieve high efficacy, i.e. >90% reduction of adult and/or larval parasites in the target host animal, the purpose of novel parasite control methods is rather to assist in maintaining parasite infections below the economic threshold. The ability to maintain parasite levels below the economic threshold is related not only to the efficacy of the control method, but also to the epidemiology of the parasites, climatic conditions, the livestock management program, and integration in a sustainable parasite control program. Because of this fundamental difference, novel parasite control methods need to be evaluated using efficacy criteria different from that adopted for anthelmintics. Although the efficacy of novel parasite control methods may be demonstrated in classic dose-confirmation studies, the impact on livestock production parameters can only be evaluated when tested on-farm. In this paper, the rationale for evaluating novel methods differently from anthelmintics is reviewed, potential performance expectations are presented, and four novel parasite control methods (vaccines, nematophagous fungi, condensed tannins, and immunonutrition) are assessed based on the potential performance criteria.     

Comparative efficacy of flubendazole and a commercially available herbal wormer against natural infections of Ascaridia galli, Heterakis gallinarum and intestinal Capillaria spp. in chickens

The efficacy of a commercially available flubendazole-based product and a commercially available herbal product were compared against three species of helminth parasites of chickens: Ascaridia galli, Heterakis gallinarum and Capillaria spp. A total of 48 naturally infected chickens were used in the study with 16 birds in each of three treatment groups (untreated control; flubendazole; and a herbal product). One bird from each treatment group was necropsied on Day 0 prior to first treatment to confirm the parasite species present in the birds. Treatments were administered as labelled and the 45 remaining birds were necropsied on Day 12 and worm counts performed. Average worm counts in the two treated groups were compared to the untreated controls to calculate efficacy. Flubendazole (Group A) achieved an overall efficacy of 99.4% for the three parasite species. The herbal product (Group B) achieved efficacies ranging from less than zero to 11.6% for the three parasites, with worm counts not significantly different to the untreated controls. At present, commercially available herbal products claiming anthelmintic properties do not require licencing as veterinary medicinal products (Directive 2004/28/EC: see Article 17 and 33-38) and thus are not required to meet specific efficacy thresholds. Products which do not appear to deliver acceptable anthelmintic efficacy, are obviously a concern from many aspects but specifically from an animal welfare perspective.     

Towards the implementation of the "basket of options" approach to helminth parasite control of livestock: emphasis on the tropics/subtropics

The virtual reliance on anthelmintic drugs alone to control internal parasites of livestock is inappropriate and ultimately unsustainable. In the tropics and subtropics, widespread and high levels of anthelmintic resistance, particularly in nematode parasites of small ruminants, is rife. But more to the point, many farmers in these regions of the world are resource poor and cannot afford, or are reluctant to purchase drugs that may also be of dubious quality. As it is with any intervention, the benefits must outweigh the costs. This is not only in terms of conventional parameters such as reduced mortality and increasing productivity (meat, milk, fibre and traction power) of livestock, but also within the broad framework of helminths of veterinary/human importance, the aim should be a positive impact on reducing the threat of helminth zoonoses. However, understanding the issues involved and education of the end-users (farmers) is of fundamental importance, before any internal parasite control program should be promoted. Within the above context, we provide examples of how the "basket of options" approach could be adopted for the control of three quite disparate helminth problems in the tropics and subtropics, viz.: strongyle nematode infections of donkeys, the Taenia solium cysticercosis/taeniosis problem of pig and man and Haemonchus contortus infections in small ruminants. The "best practice" approaches can be defined as those "basket of options" that are practical, affordable, available and appropriate, whether to the commercial producer, or to the resource-poor farmer. Constraints that may restrict applying such options are accessibility to, and affordability of, suitable remedies and above all, the availability of information needed to make informed decisions in this regard.     

The future of veterinary parasitology

Current evidence suggests research in veterinary parasitology is in decline despite its importance. This is particularly true in the UK where research funds have been diverted into BSE. Decline in interest in veterinary parasitology is at least in part due to the success of major pharmaceutical companies in producing a range of effective and safe anti-parasitic drugs. Research is needed because of the effects of parasites on animal welfare and the economic costs of parasites. However, there is little information on the actual costs of animal parasites. Another major reason for research is the development of drug resistance in protozoa, helminths and arthropods of veterinary importance. This is a serious problem particularly for sheep and goats in the southern hemisphere. A prioritised list of research requirements is suggested: (i) new drugs; (ii) resistance management; (iii) vaccines; (iv) breeding for resistance; (v) improved diagnostics; (vi) zoonoses; (vii) global warming and parasites. There is a major political challenge to raise the profile of veterinary parasitology and thus the funding essential for its advancement and the continued welfare and productivity of animals.     

Development of antiparasitic drugs in the 21st century

Prospects for discovering new antiparasitic drugs for veterinary medicine in the coming century will be determined by economic, social and scientific factors. Consolidation in the pharmaceutical industry in general, and the animal health industry in particular, changes the business conditions in which drug discovery for veterinary medicine occurs. Social pressures on traditional animal agriculture and companion animal ownership have shifted the interest of animal companies primarily to pet medicine. Antiparasitic drug discovery is more than ever targeted to the most lucrative market segments, but the excellence of available drugs, and the apparent lack of resistance in important parasites, reduces industrial motivation to invest in parasitology. Veterinary parasitologists in academia will still have the chance to interact with their industrial counterparts in the traditional ways of supporting drug discovery and development. Nonetheless, there are many new opportunities to expand the research horizons of veterinary parasitology to strengthen the case for retaining a significant presence in the animal health industry.     

在“同一个健康”框架下,加强兽医与人医合作,有效监测和应对人畜共患病和新发传染病

新发传染病主要是人畜共患病,是世界经济和公共健康的沉重负担。这就要求加强检测、鉴别和监视传染病的能力方面投入。高致病禽流感H5N1、新甲型流感("猪流感")H1N1、非典型性肺炎、西尼罗河病毒、地方流行性狂犬病、布鲁氏菌病以及发展中国家暴发的其它人畜共患病及近期猪抗甲氧西林金黄色葡萄球菌,是人类、动物及其环境相互作用的典型范例。面临中国动物和人类常见的新发传染病坚持"同一个健康"战略,这就要求业已存在的兽医和人医及公共卫生机构的通力合作。人的疾病控制系统与动物疾病控制系统虽然都已经建立,但人畜共患病的暴发表明兽医机构和人医机构密切合作的重要性。在保证环境健康的同时,通过动物疾病和人类疾病监测系统的密切合作,中国就一定能够控制人畜共患病。以这种方式进行疾病预防、监测与应对,各层面及各动物生产部门间有效的兽医推广是加强和保持健康生态环境中人和动物健康的有效办法。中国还需大量努力才能达到从制度上保证预防和消灭疾病。透明而准确的人与动物疾病监督通常会产生经济且可持续的预防疾病方法。加拿大在兽医、公共健康、食品安全和人畜共患病预防方面所发挥的作用就是与中国农业部合作,促进必要的、可持续的兽医监督网络的建设。     

Future challenges of disease in the beef cattle industry

Disease control must be part of the management system in any beef cattle enterprise where improved net returns are a constant goal. A current view of the importance of disease is reflected in the research portfolio of the Australian Meat and Live-stock Research and Development Corporation (AMLRDC), where only 14% of projects relate to cattle health problems. Our relative freedom from epidemics is partly responsible for this balance, but the profession should continue to be alert to the range of actual or potential threats to the national herds and those predisposing factors, both managerial and environmental, that influence their effects. In Australia with its crucial beef export component, several priority areas can be identified. They are (i) completion of the Brucellosis and Tuberculosis Eradication Campaign (BTEC) (ii) improved knowledge of the effects of production of subclinical disease including deficiency states (iii) better understanding of the infertility complex from conception to birth. Congenital viral infections such as mucosal disease and the arbovirus group are slowly emerging from their epidemiological obscurity (iv) constant awareness of the potential threat of exotic diseases and defensive methods available to meet them. There is a particular need to understand the epidemiology of the large tropical cattle herd, which interfaces with South-East Asia. Our comparative freedom from epidemics should not cause any relaxation of vigilance by the veterinary services in the private or public sectors. Nor should government be allowed to minimise the critical role of the veterinary profession in our defense against animal disease (v) increased liaison with our trading partners in livestock exports.(ABSTRACT TRUNCATED AT 250 WORDS)     

Educational preparedness of veterinarians for foreign animal diseases

Veterinary medical education in FADs has been and will continue to be critically important if veterinarians are expected to fulfill the profession's primary obligations to society--those of protecting our animals' health, conserving our animal resources, and promoting public health. It is imperative that curricula and instruction in veterinary schools and colleges provide the depth and breadth of knowledge and understanding necessary to prepare all veterinarians, including those in private practice, for their key role in defending against FADs. Development and implementation of governmental and military programs to diagnose, prevent, control, and eradicate FADs will require a dedicated cadre of public sector veterinarians who have a solid educational foundation in FADs and understand the contemporary issues and global challenges we face. Animal-related industries, associations, and organizations will increasingly rely on well-educated veterinarians to help guide them in ways that will protect animals, clientele, consumers, and trading partners from effects of FADs. Agencies and organizations concerned with conservation of animal resources will require veterinary expertise necessary to prevent FADs in a multitude of animal species, including marine animals, wildlife, endangered species, zoologic specimens, and important genetic lines as well as our domestic companion and livestock species. Species affected by FADs also include human beings for those disease agents with zoonotic potential; thus, veterinary education also plays a key role in public health.     

The current status and outlook for insecticide,acaricide and anthelmintic resistances across the Australian ruminant livestock industries: assessing the threat these resistances pose to the livestock sector

The Australian ruminant livestock industries are faced with the need to control parasitic infectious diseases that can seriously impact the health of animals. However, increasing levels of resistance to insecticides, anthelmintics and acaricides are substantially reducing the ability to control some of these parasites. Here we review the current situation with regard to chemical resistances in parasites across the various sectors of the Australian ruminant livestock industries and assess the level of threat that these resistances pose to the sustainability of these sectors in the short to long terms. We also look at the extent to which testing for resistance occurs across the various industry sectors, and hence how well-informed these sectors are of the extent of chemical resistance. We examine on-farm management practices, breeding of parasite-resistant animals, and non-chemical therapeutics that may act as short to long term means to reduce the current reliance on chemicals for parasite control. Finally, we look at the balance between the prevalence and magnitude of current resistances and the availability and adoption rates of management, breeding and therapeutic alternatives in order to assess the parasite control outlook for the various industry sectors.     

Recent developments in ectoparasiticides

The sales and use of ectoparasiticides for the control of arthropod parasites of domestic animals constitute a major sector of the global animal health market. Animals are infected by a number of parasitic insect and acarine species causing major economic losses in production livestock, intense irritation and skin disease in companion animals, or public health issues, including bites of humans or zoonotic disease transmission. Dog and cat fleas, for example, can be a serious source of both animal and human irritation, which has led to a rapid expansion in the development of flea control products. The control of ectoparasite infections of veterinary importance still relies heavily on the use of chemicals that target the arthropod nervous system. Such compounds have suffered from a number of drawbacks, including the development of resistance and concerns over human and environmental safety. The search for safer technologies has, however, been hindered by the limited number of active target sites present in arthropods and, to some degree, by the ever-increasing costs of research and development of compounds with novel modes of action.This review provides a background to the currently available groups of ectoparasiticide compounds used in veterinary medicine and highlights some of the more recent developments including the introduction of insect growth regulators and new and improved methods of product application.     

A review of selenium deficiency in grazing ruminants. Part 2: towards a more rational approach to diagnosis and prevention

ESTIMATING SELENIUM STATUS: Although the importance of selenium in ruminants has been recognised for over 30 years, problems associated with selenium deficiency are still frequently identified in grazing livestock operations. There is a growing diversity of tools available for the management of selenium deficiency giving rise to diagnostic and therapeutic dilemmas for the veterinary practitioner. There is no single test for selenium adequacy which can be considered superior in all diagnostic situations because the method of choice depends on the objective of the testing procedure. REFERENCE RANGES: Reviewing the available data, the current New Zealand reference ranges for selenium concentrations in ruminant tissue and feed appear valid. CLINICAL RELEVANCE: Management of selenium deficiency will continue to be important in grazing ruminants. Practising veterinarians should be familiar with the appropriate use of tests for selenium deficiency. Advice should be based on micronutrient analysis of animal tissue, defensible reference ranges backed by production response data, and supplementation programmes which optimise the return on investment.     

History of veterinary parasitology in France

The history of veterinary parasitology in France can be divided into three parts. (1) The early period of veterinary education, and development of sections on parasites and parasitic diseases, immediately following the creation of the veterinary colleges in France in 1762-1765 by Cl. Bourgelat until the beginning of the 19th century. This was the period of academics, naturalists and zoologists, with the exception of P. Chabert who, as early as 1782, directed attention to the harmful effects of parasites on animals and tried to control them. (2) Identification and establishment of the field of veterinary parasitology and the development of specific research work, mostly in veterinary colleges, on the biology and systematic control of parasites. This period was dominated by the tremendous amount of work carried out by L.G. Neumann and A. Railliet in every topic of veterinary parasitology. (3) The modern period of veterinary parasitology (before and after World War II). This period is characterized by the increasing development of the most sophisticated techniques in fundamental and applied research to provide efficient cheap and practical means for the diagnosis and control of parasitic diseases in animals.     

A survey of helminth control practices in equine establishments in Ireland

We report the results of a survey to assess the attitudes of horse owners and managers of equine businesses in Ireland to the control of helminth parasites, and the extent to which veterinary practitioners are involved in providing advice on parasite control of horses.Replies to our questionnaire indicated that there is a high level of awareness on the need for helminth control, typically leading to several doses of anthelmintic being administered to each animal every year. While a majority of respondents (61%) were concerned about the issue of anthelmintic resistance, only a few were of the opinion that it was a problem on their establishment. Measures to minimise the development of resistance, such as decreasing the frequency of dosing, optimising non-drug-based control strategies and assessing the need for dosing by faecal egg counts (FECs), were not widely employed in a strategic manner. Just over half (54%) of respondents indicated that they devised worming control programmes based on veterinary advice, and a large majority did not perceive any need for modification of their current worm control programmes.We concluded that there is considerable scope for increased veterinary involvement in the design and implementation of control programmes for helminths in horses, and that veterinarians do not always provide advice in accordance with "best practice" in helminth control.     

REGULATORY VETERINARY MEDICINE IN A CHANGING ENVIRONMENT*

SUMMARY There is an increasing need for the veterinary profession to meet the new challenges brought about by increased and intensified livestock production. These challenges consist of control and eradication of diseases, the humane treatment of animals and the prevention of transmission of disease from animals or animal products to man.     

Evaluating the economic and noneconomic impacts of the veterinary medical profession in Michigan

This study reaffirms the diversity and breadth of the veterinary profession. As it turns out, some of the furthest-reaching impacts of the veterinary medical profession were largely non-quantifiable. The veterinary medical profession had a substantial direct economic impact in Michigan during 1995. The total economic contribution of the veterinary medical profession to Michigan during 1995 that was attributable to expenditures on salaries, supplies, services, and their multiplier effect was approximately $500 million. In addition, the profession was associated with nearly 8,500 jobs (combined professional and lay positions). The veterinary medical profession was also considered to have an impact on the prosperity of the live-stock, equine, and pet food industries in Michigan, even though the economic contribution in these areas could not be directly quantified. Economic well-being of the individual businesses in these industries is directly related to the health and productivity of the associated animals, and improvements in output or productivity that accompany improved animal health likely carry substantial economic benefits in these sectors. In addition, progressive animal health management provides a crucial method of managing risk in the animal industries. Similarly, although the economic contribution could not be quantified, the veterinary medical profession enhances the safety and quality of human food through research, regulation, and quality assurance programs in livestock production, minimizing the risk of drug residues and microbial contamination. During 1995, approximately 5.3 million Michigan residents benefitted from the physical, psychological, and emotional well-being that accompanies companion animal ownership. By preserving the health and longevity of companion animals, veterinarians sustain and enhance these aspects of the human-animal bond. As Michigan enters a new century, it is likely that the state's veterinary medical profession will continue to make a highly valued societal contribution. Pets, equines, and food animals will continue to have prominent roles in Michigan for the foreseeable future, as will the human-animal bond, food safety, and medical research. Clearly, for economic and noneconomic reasons, it will be in the interest of the people of Michigan to seek opportunities to maintain and enhance the vitality of the state's veterinary medical profession. It was our hope that results of this study would provide university administrators, legislators, MVMA executives, and others with information needed to justify the ongoing provision of public support for the veterinary medical profession. In addition, we expect that the results will supply useful material for public relations and marketing campaigns by the MVMA and the Michigan State University College of Veterinary Medicine and will provide the media with public interest stories to promote the veterinary profession. Although this study considered the economic and noneconomic impacts of the veterinary medical profession only in Michigan, the results can provide an important reference point for educators, policy markers, and legislators in other states. In addition, this study could serve as a methodologic model for veterinary organizations in other states, or at the national level, to emulate.     

Food safety achieved through herd management

Most animal-derived food products originate from production chains consisting of a series of well-defined, separate production steps. Undesired events affecting food safety can principally occur at any point within the production chain. The principle of integrated food safety assurance from stable to table has therefore been established. The livestock holding has thus to be understood as a fix element of the production chain, and the producer has to accept a part of the responsibility for food safety. On a farm, food safety can be negatively affected by animal feed (microbiological or toxicological contamination), management (hygiene, stocking density, cleaning and disinfecting), veterinary treatments (use of antibiotics) and recycling of slurry. Most relevant practices can be summarised under the standard of "good farming practice". HACCP programmes as they are applied in the processing industries could in principle also be used at the farm level. Influential management steps would need to be identified and controlled. This approach is, however, still in its infancy at present. Using the current monitoring systems, microbiological and toxicological problems in food are difficult to be identified before the end of the production chain. As the cause of a problem can be found at the farm level, traceability of products through the production chain is essential. In Switzerland, traceability of animals is realised using compulsory animal identification and the animal movement database. Using this link, information on the health status of a herd could be made available to the slaughterhouse in order to classify animals into food-safety risk categories. This principle is a key element in the ongoing discussion about visual meat inspection in Europe and elsewhere.     

山东省畜禽养殖用药现状及对策

在对山东省畜禽养殖管理情况和用药现状的调研中,一方面看到了近几年在饲养管理和兽药等投入品监管中的进步,另一方面也发现,在畜禽养殖场中不规范用药是影响畜产品质量的重要风险之一.同时,深刻分析了兽药残留和耐药性的产生原因并提出了规范用药、保障畜产品安全的对策,以提升畜产品质量安全监管水平,促进畜牧业科学发展.