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1.
W I Morrison 《Veterinary parasitology》1987,25(2):163-176
The first part of this presentation considers some of the complexities of parasitic infections and parasite-specific effector mechanisms which have hampered the development of practical methods of immunisation against parasitic diseases. In the second part, an outline is given of the effector mechanisms involved in immunity of cattle to the protozoan parasite Theileria parva. Parasites are antigenically complex organisms which often have distinct developmental stages, sometimes with different predilection sites within the host. Antigenic polymorphism between strains is a common feature of parasites and sometimes results in strain-specific immunity. Certain parasites have also evolved mechanisms of modulating surface antigens which allow them to escape host effector mechanism. Effector mechanisms which control parasitic infections may operate by preventing establishment of the parasites, by eliminating the parasites once they have established or by affecting growth or fecundity of the parasites. In addition to specific antibody and cell-mediated immune responses, inflammatory or physiological responses play an important role in the control of some parasites. Current evidence suggests that effector mechanisms against T.parva parasites operate at two levels. First, antibodies produced against the infective stage of the parasite, the sporozoite, can, by neutralising infectivity, reduce the numbers of organisms which establish in the host. Second, cytotoxic T cells directed against parasitised lymphoblasts cause destruction of parasites following their establishment in the host. Moreover, in situations where immunity is parasite strain-specific, the cytotoxic T cell responses have also been found to be strain-specific. The elucidation of these effector mechanisms has indicated potential new strategies of immunisation against T.parva. 相似文献
2.
T M Craig 《Journal of animal science》1988,66(6):1565-1569
Internal parasitism is a pervasive constant that reduces returns in beef cattle production. Parasitism may influence production sufficiently so that data derived investigating performance response will be erroneous. The interaction of internal parasites of cattle with other facets of their lives makes it imperative that more parasite research be done on cattle to consider their impact. Results of trials designed to determine forage production at various stocking densities may not reflect the nutritive value of the forage, but instead the severity of parasite exposure. Relative resistance or susceptibility to certain parasites vary with the breed of livestock and the species of parasite. Extensive work to evaluate the ability of various breeds and sires to influence parasitic numbers has been conducted in sheep but not in cattle. Some parasite trials have ignored the effects of nutrition on the establishment and retention of parasites. This becomes especially important where multiple parasite exposure may occur. Susceptible cattle, even on an optimal diet, will become parasitized, but if reexposed to the same species of parasite, cattle on an optimal diet may be able to resist reinfection, whereas those on deficient diets will not. 相似文献
3.
Postmortem records of cattle brought to the Veterinary School in Kabete near Nairobi were examined for a period of 15 years (1984-1998, inclusive) in order to establish the role that parasitic diseases played as causes of death. The cattle were mainly of exotic breeds but a few were crosses or of indigenous breeds. There was a total of 1413 cases of deaths from various diseases of which 177 (13%) were due to parasites. The tick-borne diseases were in high proportions and accounted for 84,7% among the parasitic causes, which represented 10,6% of all the deaths recorded. The main tick-borne disease was East Coast fever (ECF) (65%) followed by heartwater (10,2%), babesiosis (5,1%) and anaplasmosis (4,5%). Hydatidosis was responsible for 7,3% of deaths from parasitic causes. Deaths from ECF were recorded in all the 15 years and in high proportions compared to those due to heartwater (8/15), babesiosis (7/15) and anaplasmosis 5/15). Over the period under consideration, no decline was noted among various disease conditions despite advances made in controlling tick vectors and in the treatment of various parasitic conditions. The area covered by this study has the advantage of having several veterinary-related institutions close by. Hence knowledge and awareness about livestock diseases is relatively high compared to other parts of the country. It is therefore challenging to the Veterinary Department to examine the service delivery systems and other factors that may contribute to the persistent presence of these fatal parasitic conditions of cattle. 相似文献
4.
为了解内蒙古部分地区规模化牛场牛体寄生虫的感染情况，从2015—2017年，采用饱和盐水漂浮法、离心沉淀法、麦克马斯特氏虫卵计数法、血清学和免疫学等方法，对内蒙古呼和浩特市和锡林郭勒盟等地的牛场进行了流行病学调查。结果显示：所检牛群主要感染的寄生虫为毛圆科线虫和艾美耳球虫；2015年还检出了新孢子虫，个别牧场有肺丝虫检出；未有吸虫、绦虫、血液原虫和毛滴虫检出。在为期3年的调查中，经针对性地治疗，寄生虫的感染率呈显著的下降趋势。这些数据的取得为了解所调查牧场的寄生虫感染状况，并根据调查数据开展相关寄生虫的防治工作提供了重要信息。 相似文献
5.
肠道寄生虫与菌群互作关系研究进展 总被引：1，自引：1，他引：0
肠道菌群是动物机体的重要组成部分，与寄生虫和宿主的关系十分密切。寄生虫感染往往会对宿主产生不利影响，其致病作用与寄生虫种类、寄生部位及其与宿主的相互作用有关。寄生虫感染可导致肠道微生态的改变、失调和炎症性疾病；肠道菌群也影响寄生虫在宿主体内的定植、增殖和毒力。肠道寄生虫包括寄生蠕虫和原虫，近年来对肠道寄生虫与菌群相互作用研究发现，无论是原虫还是蠕虫感染均可导致肠道微生物组成和多样性的改变，对宿主产生致病作用，而蠕虫对炎症性肠病的潜在治疗作用一度颠覆了以往人们对于寄生虫的认知。肠道菌群可促进或抑制寄生虫对宿主的致病作用，且益生菌对肠道寄生虫感染有一定的预防或治疗作用。目前对寄生虫与菌群相互作用的研究仍然处于初期阶段，对其相互作用的机制尚不清楚。明确寄生虫与肠道菌群的相互影响及其作用机制，对深入理解寄生虫－肠道菌群－宿主的相互关系、研发有效的抗寄生虫微生态制剂具有重要意义。作者就近年来肠道蠕虫和原虫与菌群相互作用的研究进展进行了综述，并对该领域未来的研究方向进行展望，以期为预防和控制寄生虫病提供新的策略和理论依据。 相似文献
6.
Parasites in cultured and feral fish. 总被引：3，自引：0，他引：3
T Scholz 《Veterinary parasitology》1999,84(3-4):317-335
Parasites, causing little apparent damage in feral fish populations, may become causative agents of diseases of great importance in farmed fish, leading to pathological changes, decrease of fitness or reduction of the market value of fish. Despite considerable progress in fish parasitology in the last decades, major gaps still exist in the knowledge of taxonomy, biology, epizootiology and control of fish parasites, including such 'evergreens' as the ciliate Ichthyophthirius multifiliis, a causative agent of white spot disease, or proliferative kidney disease (PKD), one of the most economically damaging diseases in the rainbow trout industry which causative agent remain enigmatic. Besides long-recognized parasites, other potentially severe pathogens have appeared quite recently such as amphizoic amoebae, causative agents of amoebic gill disease (AGD), the monogenean Gyrodactylus salaris which has destroyed salmon populations in Norway, or sea lice, in particular Lepeophtheirus salmonis that endanger marine salmonids in some areas. Recent spreading of some parasites throughout the world (e.g. the cestode Bothriocephalus acheilognathi) has been facilitated through insufficient veterinary control during import of fish. Control of many important parasitic diseases is still far from being satisfactory and further research is needed. Use of chemotherapy has limitations and new effective, but environmentally safe drugs should be developed. A very promising area of future research seems to be studies on immunity in parasitic infections, use of molecular technology in diagnostics and development of new vaccines against the most pathogenic parasites. 相似文献
7.
Waller PJ 《New Zealand veterinary journal》1992,40(1):1-3
Control of nematode parasites in ruminants is directed almost exclusively at the parasitic stage in the host using conventional anthelmintic therapy. However, to complete their life cycle, parasites have to develop through a series of free-living stages on pasture. It is within this environment that there is a vast range of cohabiting micro-organisms, some of which are known to infect or prey on nematodes. These include bacteria, protozoa, viruses and fungi. To date, most interest has been focused on those organisms producing chemical toxins which have been developed as anthelmintics, e.g. Streptomyces/avermectins. Yet the potential of predacious and nematoxic fungi and bacteria for the biological control of nematode parasites of livestock remains largely untapped. These organisms may well offer a cheaper and more sustainable approach to reducing the impact of parasitism in livestock. 相似文献
8.
N F Baker 《Veterinary parasitology》1988,27(1-2):125-138
Diagnostic methods which reveal only the presence or absence of Ostertagia in grazing animals are of little importance since all will acquire some degree of infection when grazed in the temperate regions of the world. Ostertagia infections may be (1) light--no disease or performance losses occur; (2) moderate--disease may or may not be overtly visible but performance losses occur or (3) heavy--disease is overt with or without death loss. The differentiation of these levels of infection is a quantitative matter insofar as the number of parasites correlates with the degree of pathology and is much less certain than is the presence or absence of infection. Historically, the quantitative parasite egg count in feces (eggs per gram (e.p.g.)), combined with the usual subjective and objective information obtained in clinical examinations has been the procedure used to obtain a quantitative estimate of the level of infection. More recently, the use of plasma pepsinogen levels as an indication of gastric pathology has been adopted by some laboratories. Neither of these methods have met with the desired level of accuracy, but they do have considerable value when their limitations are recognized. In the present era of emphasis on epidemiologically based control programs we are faced with yet another aspect of diagnosis, namely that of a quantitative estimate of numbers of infective stages (L3) on herbage. Methods to assess the number of L3 on forage are not satisfactory for routine clinical use. This paper evaluates the primary objectives of diagnosis as applied to the herd and flock. It briefly evaluates current methodology insofar as the diagnosis of parasitic gastroenteritis is concerned. The use of e.p.g. counts in clinical practice is discussed. Examples applicable to herds of weaner and stocker cattle are presented. 相似文献
9.
Thomas A Yazwinski Chris A Tucker 《Veterinary Clinics of North America: Food Animal Practice》2006,22(3):501-527
Gastrointestinal nematodosis of cattle is a parasitic condition resulting from an immense and seemingly forever-expanding array of factors. Countless determinants influence the incidence and severity of the species-specific infections that occur in cattle, determinants that affect the free-living or environmental stages of the parasites and the parasitic stages. The vast majority of animals have a subclinical or economic level of parasitism undetectable to the eye but quantified more accurately by treatment-induced improved performance (e.g., feed efficiency, nitrogen balance, weight gain, milk production). Unfortunately, the results of treatment (effectiveness and improved animal performance) sometimes can be as varied as the parasitisms that are being treated. 相似文献
10.
通过对张掖市肉牛寄生虫病感染情况分析,提出了＂定期监测、适时驱虫、合理用药、环境控制、定期评估＂的程序化防治方案。通过三年的推广应用,取得了显著的防治效果,获得显著经济效益,证明程序化防治技术在当今的牛业生产中是切实可行。 相似文献
11.
An extended-release injection, which is administered at a rate of 1 mg eprinomectin/kg body weight, has been developed to provide up to 150 days control of parasites of cattle. The product can facilitate the achievement of two of the fundamental aims of parasite control. The first is protection of the host against the negative impact of susceptible parasites in order to ensure control of disease and to enhance performance. The second is to reduce parasite transmission and hence the challenge to animals when grazing. In addition, farmers and veterinarians can benefit from high levels of convenience and hence compliance from a single administration, which also limits handling stress in the cattle. This introductory paper provides some perspective on the practical applications for this extended-release product under various husbandry systems and in different classes of cattle and discusses its role in sustainable parasite control. 相似文献
12.
Daugschies A 《DTW. Deutsche tier?rztliche Wochenschrift》2001,108(8):348-352
International transport of animals is associated with an enhanced risk of import of a number of parasite species that are not endemic in Germany. Pets accompany tourists on journeys all over the world, but in particular to southern Europe, and dogs are increasingly imported from (sub-)tropical countries for reasons of animal welfare. Veterinary practitioners are thus confronted with parasites that are unusual in their patients. The specific transmission routes determine whether an imported parasite is able to become endemic. Although parasites eradicated in Germany such as Trypanosoma equiperdum and Tritrichomonas foetus may be principally imported they are unlikely to re-establish due to the current epidemiological conditions. Imported animals that harbour parasites which may occur naturally but are currently rare in Germany are a potential source of increased infection risk. Certain areas in Germany have probably become endemic for Babesia canis and the respective vector tick Dermacentor reticulatus has been found. Whether other vector borne parasitic diseases such as leishmaniosis or heartworm disease have the potential to spread into Germany is still a matter of debate. 相似文献
13.
[目的]为了解芒市肉牛肠道寄生虫的感染情况,为其寄生虫病的防治提供参考。[方法]从云南省德宏州肉牛场采集191份新鲜粪样,采用饱和盐水漂浮法和自然沉淀法检查寄生虫的感染情况。[结果]共有124份样品检测出寄生虫感染,总感染率为64.92%,检出球虫、线虫、吸虫,其感染率分别为30.89%、4.19%、15.71%,混合感染率为14.41%。不同品种的肉牛之间寄生虫感染存在显著差异(P<0.05),不同养殖场、不同性别和不同年龄的肉牛之间寄生虫感染无显著性差异(P>0.05)。[结论]芒市肉牛寄生虫感染较为严重,其球虫的感染尤为突出,应定期驱虫和加强综合防治来促进肉牛的健康养殖。 相似文献
14.
Diseases resulting from zoonotic transmission of parasites are common. Humans become infected through food, water, soil and close contact with animals. Most parasitic zoonoses are neglected diseases despite causing a considerable global burden of ill health in humans and having a substantial financial burden on livestock industries. This review aims to bring together the current data available on global burden estimates of parasitic zoonoses and indicate any changes in the trends of these diseases. There is a clear need of such information as interventions to control zoonoses are often in their animal hosts. The costs of such interventions together with animal health issues will drive the cost effectiveness of intervention strategies. What is apparent is that collectively, parasitic zoonoses probably have a similar human disease burden to any one of the big three human infectious diseases: malaria, tuberculosis or HIV in addition to animal health burden. Although the global burden for most parasitic zoonoses is not yet known, the major contributors to the global burden of parasitic zoonoses are toxoplasmosis, food borne trematode infections, cysticercosis, echinococcosis, leishmaniosis and zoonotic schistosomosis. In addition, diarrhoea resulting from zoonotic protozoa may have a significant impact. 相似文献
15.
Morris CA 《Veterinary journal (London, England : 1997)》2007,174(3):481-491
Cattle show considerable variability in their responses to a wide range of disease challenges, and much of the variability is genetic. This review highlights genetic variation in disease susceptibility in Bos taurus cattle, with variation found at the breed level and also within breeds. Disease challenges come from bacteria and viruses, parasites and feed-borne toxins. For an animal to survive, it needs its own mechanisms for resisting these challenges, or for being resilient to them, or it must be protected artificially from them. Disease challenges have been classified as 'diseases from without', but there is also another class of genetic diseases resulting from inborn errors of metabolism, which might be called 'diseases from within'. Degrees of inheritance (heritabilities) are reviewed for a range of economically important traits including resistance to mastitis, ketosis, lameness, nematode parasites, external parasites, eye disease, respiratory disorders, tuberculosis, brucellosis, Johne's disease, foot-and-mouth disease, bovine spongiform encephalopathy, metabolic disorders caused by toxins found on the feed, and threshold levels of minerals and metabolites. Many, but not all, of the above require an immune response as part of the fight against an external challenge, and measurements have been made of general immune response as a way of describing or predicting how an animal will respond. There are now some examples of industry or breed societies applying selection for resistance to one or more diseases as part of a complete breeding objective in dairy cattle, beef cattle or dual purpose livestock. In most cases, industry and breed societies are in the early stages of applying effective selection pressure for resistance to specific cattle diseases, with the notable exceptions of Scandinavian cattle schemes, which lead the world in this respect. 相似文献
16.
为了掌握源于安徽省金寨县牛羊肠道寄生虫感染情况,对该地区展开病原学调查,以期为该地区牛羊寄生虫病防治与诊断工作提供理论依据。该调查主要采用直接涂片法、饱和食盐水漂浮法对在金寨县的4个乡（镇）7个不同养殖场（2个牛养殖场和5个羊养殖场）采集的50份牛羊粪便进行检查,并根据形态学特征对所获得的虫卵和幼虫进行归类。经过对调查样本的检查结果显示共查出8种寄生虫,分别为犊新蛔虫、古柏线虫、扩展莫尼茨线虫、大片形吸虫、食道口线虫、夏伯特线虫、捻转血矛线虫、前后盘吸虫等。由此可见,安徽省金寨县牛羊寄生虫感染还是比较严重,因此需采取相应的防治措施。 相似文献
17.
Integrated and biological control of parasites in organic and conventional production systems. 总被引：5，自引：0，他引：5
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. 相似文献
18.
Changing eating habits, population growth and movements, global trade of foodstuff, changes in food production systems, climate change, increased awareness and better diagnostic tools are some of the main drivers affecting the emergence or re-emergence of many foodborne parasitic diseases in recent years. In particular, the increasing demand for exotic and raw food is one of the reasons why reports of foodborne infections, and especially waterborne parasitosis, have increased in the last years. Moreover increasing global demand for protein of animal origin has led to certain farming practices (e.g. aquaculture) increasing in emerging or developing countries, where health monitoring may not be sufficiently implemented. Therefore, high quality epidemiological data are needed which together with biological, economic, social and cultural variables should be taken into account when setting control programs for these increasingly popular production systems in emerging economies. This review focuses on the dietary, social, economic and environmental changes that may cause an increase in human exposure to foodborne parasites. Some examples illustrating these new epidemiological dynamics of transmission foodborne parasitic disease are presented. 相似文献
19.
《Seminars in avian and exotic pet medicine》2004,13(4):197-205
Waterfowl, whether free-living or in captivity, are hosts to a wide variety of internal and external parasites. With few exceptions, the significance of most parasitic infections is unknown, due, in part, to the fact that mixed parasitic infections are the rule rather than the exception. Therefore, effects of any one parasite species must be made in light of the other parasites, diseases, or stressors (eg, malnutrition) that may be present. Furthermore, the pathogenicity of a parasite may differ among species of birds as well as different populations of the same species. Experimental assessment of the effects of some parasites have been attempted using the mallard duck as the model; however, in light of species differences, the applicability of such studies to other species of waterfowl is unclear. Of the several hundred parasites that are present, nasal leeches, Leucocytozoon simondi, certain species of coccidia, some nematodes, the trematode Sphaeridiotrema globulus, cestodes in the genus Gastrotaenia, and some acanthocephalans have been associated with morbidity and/or mortality in captive or wild waterfowl. Detection of many parasitic infections can be accomplished through traditional diagnostic techniques (eg, fecal flotation, blood smears); however, the presence of parasites does not automatically equate with the presence of disease. Control and treatment measures are few, especially for free-ranging waterfowl. However, excellent sanitation can help combat many parasites in captive situations. 相似文献
20.
Hunt PW 《Veterinary parasitology》2011,180(1-2):12-46
Since 1977, >2000 research papers described attempts to detect, identify and/or quantify parasites, or disease organisms carried by ecto-parasites, using DNA-based tests and 148 reviews of the topic were published. Despite this, only a few DNA-based tests for parasitic diseases are routinely available, and most of these are optional tests used occasionally in disease diagnosis. Malaria, trypanosomiasis, toxoplasmosis, leishmaniasis and cryptosporidiosis diagnosis may be assisted by DNA-based testing in some countries, but there are very few cases where the detection of veterinary parasites is assisted by DNA-based tests. The diagnoses of some bacterial (e.g. lyme disease) and viral diseases (e.g. tick borne encephalitis) which are transmitted by ecto-parasites more commonly use DNA-based tests, and research developing tests for these species makes up almost 20% of the literature. Other important uses of DNA-based tests are for epidemiological and risk assessment, quality control for food and water, forensic diagnosis and in parasite biology research. Some DNA-based tests for water-borne parasites, including Cryptosporidium and Giardia, are used in routine checks of water treatment, but forensic and food-testing applications have not been adopted in routine practice. Biological research, including epidemiological research, makes the widest use of DNA-based diagnostics, delivering enhanced understanding of parasites and guidelines for managing parasitic diseases. Despite the limited uptake of DNA-based tests to date, there is little doubt that they offer great potential to not only detect, identify and quantify parasites, but also to provide further information important for the implementation of parasite control strategies. For example, variant sequences within species of parasites and other organisms can be differentiated by tests in a manner similar to genetic testing in medicine or livestock breeding. If an association between DNA sequence and phenotype has been demonstrated, then qualities such as drug resistance, strain divergence, virulence, and origin of isolates could be inferred by DNA-based tests. No such tests are in clinical or commercial use in parasitology and few tests are available for other organisms. Why have DNA-based tests not had a bigger impact in veterinary and human medicine? To explore this question, technological, biological, economic and sociological factors must be considered. Additionally, a realistic expectation of research progress is needed. DNA-based tests could enhance parasite management in many ways, but patience, persistence and dedication will be needed to achieve this goal. 相似文献