Effect of bovine viral diarrhea virus in the feedlot.

It could be argued that bovine viral diarrhea virus (BVDV) is one of the most economically significant infectious pathogens of feedlot cattle. Although the direct economic losses caused by this virus have not been well quantified, the role it plays as an immunosuppressive agent and as a potentiator for other diseases, most notably bovine respiratory disease, have been well documented. It is also a difficult disease for the feedlot veterinarian to control effectively.Individual cattle persistently infected with BVDV often serve as the source of infectious virus within a group of feedlot cattle, and the ultimate responsibility for preventing persistent infections in cattle rests with the cow-calf producer and not with the feedlot owner. The enormous impact of the virus on the livestock industry has led the Academy of Veterinary Consultants to draft a position statement that resolves that the beef and dairy industries adopt measures to control and target eventual eradication of BVDV from North America.     

Infectivity of bovine leukaemia virus infected cattle: an ELISA for detecting antigens expressed in in vitro cultured lymphocytes.

A simple ELISA is described for quantifying expression of bovine leukaemia virus (BLV) antigens in short-term cultures of peripheral blood lymphocytes (PBL) isolated from infected cattle. The PBL-ELISA demonstrated that antigen expression levels in infected cattle could vary by more than 50-fold. Inoculation of sheep with dilutions of lymphocytes from two BLV-infected cattle, differentiated in the PBL-ELISA by 50 to 100-fold, suggested that antigen expression levels were correlated with infectivity. Haematological data indicated that increased antigen expression in PBL cultures was associated with an increased number of circulating B-lymphocytes, irrespective of whether or not an animal had lymphocytosis. This supported the hypothesis that BLV-infected cattle that are PBL-ELISA positive are more infectious and may present a greater risk of transmitting the disease. The applicability of the PBL-ELISA to a field situation was assessed with 98 BLV-infected cattle from three commercial dairy herds with infection prevalences of 11%, 23% and 47%. Similar percentages (49%, 50% and 52%) of PBL-ELISA positive cattle were identified among those infected cattle available for testing in the three herds. An additional 22 infected cattle from an experimental herd were tested to assess the stability of antigen expression levels over an 8 month period. Fewer (27%) of these cattle were identified as PBL-ELISA positive and antigen expression levels were generally lower than those observed in the commercial herds. Antigen expression levels in the experimental herd remained stable over the period of the study. The potential of the PBL-ELISA to assist in BLV eradication programs by identifying those seropositive cattle with the greatest potential to transmit infection is discussed.     

Problems and possibilities into the next decade involving beef cattle breeding research in the southern region: cooperator herds.

When resources are limited, use of cattle owned and maintained by cooperators to conduct beef cattle breeding research in the Southern Region can be a feasible alternative to the traditional policy of using experiment station cattle. Former students, former experiment station employees, extension personnel, institutional personnel, or tribal personnel can serve as suitable cooperators or can aid in locating potential cooperators. Several problems can be associated with cooperative work; however, the two most obvious are 1) only a limited number of researchable questions can be addressed and 2) complete experimental control over the cattle is seldom achieved. The procedure has the primary advantage that in most cases all or at least the greatest portion of the expense of owning and maintaining the cow herd is borne by the cooperator.     

Osteochondrosis in cattle.

Osteochondrosis is a poorly understood condition that affects many species, including cattle. Its incidence is not fully appreciated in the cattle industry for many reasons. Most of the reports show a male, purebred predilection, but this may simply be a result of the typical population for which medical attention is sought. With the increasing value of female breeding stock, a less skewed distribution of the disease will most likely result. Distribution of lesions is similar to that in the horse, with the stifle and tarsus most commonly affected. Treatment is divided into medical and surgical options, but neither seem to be strikingly effective as of yet. Surgical techniques include arthroscopy and arthrotomy, and both have their complicating factors. How osteochondrosis as a disease will affect the cattle industry is still to be decided. If the incidence rate does increase with more animals being valued for their economic potential, then treatment options will surely be reevaluated and refined.     

Observations on a herd of beef cattle maintained in a tsetse area. II. Assessment of the development of immunity in association with trypanocidal drug treatment.

Three groups of Boran cattle were maintained under different trypanocidal drug regimes for 29 months in an area of "medium" tsetse challenge. The development of immunity to trypanosmiasis in the cattle was assessed on the basis of changes in trypanocidal drug requirement, development of parasitaemia, ability to maintain normal blood values, growth and response to challenge after the withdrawal of the drugs. Observations were also made on serum antibody content by immunofluorescence and on serum immunoglobulin levels. Cattle treated with Berenil on the development of clinical disease developed a partial immunity to trypanosomiasis after two years. Cattle treated as a group with Berenil on the development of patent parasitaemia in any one animal of the group did not develop immunity. Cattle treated as a group with Samorin using the same criterion for treatment developed a degree of immunity to the disease. It was concluded that group treatment with Samorin was the most suitable of the three regimes examined for the maintenance of beef cattle is a tsetse infested area.     

牛呼吸疾病综合征及其防治

牛呼吸疾病综合征是严重危害国内外肉牛养殖业的一种重要传染病,该病的致病因素复杂,包括支原体、病毒和细菌等特异性病原以及运输应激等多种因素。美国等发达国家对该病的攻关研究开始于上世纪80年代初,其研究和临床防控均已达到较高水平,但仍认为该病将是未来10～20年养牛业所面临的主要疾病。我国对该病的认识和研究尚处于起步阶段,借鉴世界上发达国家的先进经验将有助于提升我国对该病的防控水平。     

慎防牛呼吸系统疾病综合征吞利毁场

牛呼吸系统疾病综合征(BRDC)是由病原体感染、应激刺激和机体抵抗力下降等病因共同作用引起牛的一种以发热、神差纳少和鼻炎、气管炎、支气管炎、肺炎为主要临床表现的一类传染性疾病的总称,又被称为“运输热。本病多在秋冬季或春夏之交呈地方性或散发性流行,常以多种病原体相互协同作用的感染、复杂的病情导致犊牛(特别是45日龄内的犊牛)和新引进牛相当高的发病率和大批量的死亡而侵吞养牛的利润甚至推毁养牛场,是一个严重困扰养牛业的世界性问题。作者综述了BRDC的危害、病因、快速诊断,并从养牛生产实际出发较为详细地阐述了BRDC的预防与治疗技术措施,对防控BRDC有一定的实际指导意义。     

Border disease in sheep caused by transmission of virus from cattle persistently infected with bovine virus diarrhoea virus.

Two outbreaks of border disease occurred on farms with sheep flocks and breeding cattle. The infection of the pregnant sheep was probably caused by transmission of virus from calves persistently infected with non-cytopathic bovine virus diarrhoea virus (BVDV) which were kept in close confinement with the ewes during mid-pregnancy. Border disease was also induced experimentally in eight lambs by exposing their dams at 38 to 78 days of gestation to a heifer persistently infected with BVDV. Both the natural and the experimental infections were characterised by typical signs such as 'hairy-shaker' lambs and high lamb mortality. The diagnosis was confirmed by virus isolations from live-born lambs, seroconversion and pathology. The study supports the assertion that cattle persistently infected with BVDV and in close contact with pregnant sheep, are an important source of strains of virus capable of causing border disease.     

Trypanosomosis: a priority disease in tsetse-challenged areas of Burkina Faso

Trypanosomosis is an important disease affecting humans as well as animals. It remains a big constraint to livestock productions in tropical areas. The objective of this study was to assess the importance of trypanosomosis among cattle diseases in Burkina Faso, mainly in tsetse-challenged areas, and to capture information on how farmers apply available methods for controlling the disease. A survey has been carried out in 29 villages of Burkina Faso in three regions (north, southwest, and west regions). One hundred and thirty-four cattle breeders were interviewed individually with a questionnaire. The results indicate that among the 16 diseases mentioned by cattle breeders, trypanosomosis is the most important one in tsetse-challenged areas. Overall, 76.12 % of the breeders mentioned it as the most important disease, while 54.55 % of the farmers in the southwest region and 70.91 % of the farmers in the west region ranked it as a priority disease. Chemoprophylaxis/chemotherapy is widely used as a control method. Isometamidium chloride and diminazene aceturate were used by 53.49 and 46.52 % of the responders, respectively. Among farmers, 85.55 % ranked diminazene aceturate as the less efficient while 14.45 % ranked isometamidium chloride as the most efficient trypanocid. Trypanocidal drug quality and drug resistance were raised as a major concern by 30.77 and 50 % of the respondents, respectively. According to them, zebu cattle are more susceptible to trypanosomosis than taurine Baoule cattle and their crosses with zebu, emphasizing that crossing susceptible breeds with trypanotolerant ones, could be used as part of an integrated control strategy.     

A study of some biologic properties of Bovid herpesvirus-4.

This article summarizes the results of a study on several strains of Bovid herpesvirus-4 (BHV-4), isolated from cattle. The study had several objectives, namely, to verify (a) the disease-causing potential of the virus, (b) the possibility by BHV-4 to induce a latent infection in the natural host and (c) the entity of the relationships among strains of the virus isolated from different disease syndromes. The following data were obtained: (1) All strains tested were able to replicate in experimentally infected calves; however, only one strain (85/BH 16TV) caused an overt systemic disease. (2) The nervous system as well as the lymphoid structures appeared to be the target organs for replication of the virus. (3) BHV-4, like other herpesviruses, was able to establish latent infection in cattle. (4) When two strains of the virus, isolated from cattle affected by different disease syndromes, i.e. respiratory disease (strain DN-599) or vulvovaginitis (strain 85/BH 16TV), respectively, they resulted to be closely related to each other. In particular, they revealed a similar DNA pattern and both strains were able to cause respiratory disease in calves. Moreover, the two viral strains were mutually protective in that calves were generally found to be refractory to challenge inoculation with either the homologous or the heterologous virus. (5) All BHV-4 strains tested generally failed to evoke a significant production of neutralizing antibody in the experimental calves.     

Treatment of external and internal parasites of cattle.

To control parasitic disease in cattle, one first has to determine what parasites he or she is trying to control--nuisance and biting flies in a milking parlor or ticks on range cattle? The determination may be based on geographic location, class of cattle, and their management. After determining what is there, then if the numbers are sufficient, justify treatment. Each livestock producer has a different array of parasites with which to deal, and in some circumstances, parasitic disease is below the economic threshold. Others may have occasional clinical disease associated with parasites, but most have situations in which the potential of economic loss is high enough to justify control.     

Chemotherapy of experimental bovine petechial fever.

A dithiosemicarbazone was compared with two tetracycline formulations in the treatment of bovine petechial fever (BPF) in experimentally infected sheep, and was then used to treat the disease in experimental cattle. The dithiosemicarbazone was found to be more efficacious than either of the other two drugs in treating ovine BPF, and also to be effective against BPF in cattle.     

Synergistic effects of concurrent challenge with bovine respiratory syncytial virus and 3-methylindole in calves.

OBJECTIVE: To evaluate the potential synergy between bovine respiratory syncytial virus (BRSV) and 3-methylindole (3MI) in inducing respiratory disease in cattle. ANIMALS: 20 mixed-breed beef calves. PROCEDURE: A 2 X 2 factorial design was used, with random assignment to the following 4 treatment groups: unchallenged control, BRSV challenge exposure (5 X 10(4) TCID50 by aerosolization and 5.5 X 10(5) TCID50 by intratracheal inoculation), 3MI challenge exposure (0.1 g/kg of body weight, PO), and combined BRSV-3MI challenge exposure. Clinical examinations were performed daily. Serum 3MI concentrations, WBC counts, PCV, total plasma protein, and fibrinogen concentrations were determined throughout the experiment. Surviving cattle were euthanatized 7 days after challenge exposure. Pulmonary lesions were evaluated at postmortem examination. RESULTS: Clinical respiratory disease was more acute and severe in cattle in the BRSV-3MI challenge-exposure group than in cattle in the other groups. All 5 cattle in this group and 3 of 5 cattle treated with 3MI alone died or were euthanatized prior to termination of the experiment. Mean lung displacement volume was greatest in the BRSV-3MI challenge-exposure group. Gross and histologic examination revealed that pulmonary lesions were also most severe for cattle in this group. CONCLUSIONS AND CLINICAL RELEVANCE: Feedlot cattle are commonly infected with BRSV, and 3MI is produced by microflora in the rumen of all cattle. Our results suggest that there is a synergy between BRSV and 3MI. Thus, controlling combined exposure may be important in preventing respiratory disease in feedlot cattle.     

The pathology of Psoroptes ovis infestation in cattle with a special emphasis on breed difference.

In cattle, infestations with P. ovis are responsible for a severe dermatitis. The disease is very common in some breeds of beef cattle whereas dairy cattle such as Frisian Holstein are considered as resistant. In order to investigate the factors responsible for this marked breed susceptibility, the immune response to P. ovis under experimental and field conditions has been studied using serology, lymphocyte transformation assay, intradermal tests and passive cutaneous anaphylaxis in susceptible Belgian White and Blue (BWB) and resistant Frisian Holstein (FH) cattle. The results of published studies are reviewed in this paper; original data on specific hypersensitivity reactions to P. ovisare also presented. The use of a sandwich ELISA allowed the detection of specific antibodies as early as 7 days post-infestation and very high titres were observed. There was a clear positive correlation between the antibody titre and the extent of lesions. This antibody response was associated with a marked in vitro lymphocyte proliferation but there was no difference between susceptible and resistant cattle. The passive cutaneous anaphylaxis test revealed the presence of specific Ig E in actively infested animals irrespective of the breed. Specific Ig E were detected fairly late during the course of an experimental infestation with P. ovis. The intradermal injection of P. cuniculi antigenic extract induced an immediate reaction in all animals including the controls; in contrast, a delayed hypersensitivity reaction was observed in infected BWB animals only. It is concluded that immunological as well as non-immunological factors may be responsible for the breed related susceptibility or resistance to P. ovis.     

The relationship between cellular immune response to foot-and-mouth disease virus Asia 1 and viral persistence in Indian cattle (Bosindicus)

Foot-and-mouth disease (FMD), the most contagious animal disease, is associated with persistent viral infection in ruminants, despite the induction of systemic immune response. The present study was performed to decipher the relation between the persistent FMD virus (FMDV) infection and cellular immune response in Indian cattle (Bosindicus) following experimental inoculation of FMDV Asia 1. Persistent viral infection (carriers) was detected by antigen capture RT-PCR on the oesophageal-pharyngeal fluid. Viral excretion was found to be intermittent and strongly variable among the persistently infected Indian cattle. Lymphocyte proliferative (LP) response, assessed as reactivity of peripheral blood mononuclear cells to FMDV Asia 1 antigen (Ag) was of low magnitude indicating a weak primary cellular immune response following infection. LP response to FMDV Ag was higher among the non-carriers than carriers of FMDV Asia 1. An enhanced LP response was associated with the lack of virus shedding in the OPF. The findings of this study are suggestive of relationship between cellular immune response and virus excretion during persistence of FMDV Asia 1 in infected cattle.     

Seasonal meningoencephalitis in Holstein cattle caused by Naegleria fowleri.

Primary amoebic meningoencephalitis is a fulminant infection of the human central nervous system caused by Naegleria fowleri, a free-living amoeba that thrives in artificially or naturally heated water. The infection usually is acquired while bathing or swimming in such waters. The portal of entry is the olfactory neuroepithelium. This report describes fatal meningoencephalitis caused by N. fowleri in Holstein cattle that consumed untreated surface water in an area of California where summer temperatures at times exceed 42 degrees C. In the summers of 1998 and 1999, severe multifocal necrosuppurative hemorrhagic meningoencephalitis was observed in brain samples from nine 10-20-month-old heifers with clinical histories of acute central nervous system disease. Olfactory lobes and cerebella were most severely affected. Lesions were also evident in periventricular and submeningeal neuropil as well as olfactory nerves. Naegleria fowleri was demonstrated by immunohistochemistry in brain and olfactory nerve lesions and was isolated from one brain. Even though cultures of drinking water did not yield N. fowleri, drinking water was the likely source of the amoeba. The disease in cattle closely resembles primary amoebic meningoencephalitis in humans. Naegleria meningoencephalitis should be included among differential diagnoses of central nervous system disease in cattle during the summer season in areas with high ambient temperatures.     

使用酵母培养物AYC-X6防治犊牛腹泻效果

[目的]犊牛腹泻是犊牛最常见的消化道疾病,是由饲养管理和多种感染性病原微生物共同作用引起。为研究在犊牛日粮中添加酵母培养物防治犊牛腹泻效果。[方法]在宁夏固原现代农业园区肉牛繁育基地随机选取120头2.5月以下犊牛作为试验牛群,对照组和试验组各60头,试验组犊牛每头每天添加30 g酵母培养物AYC-X6,对照组不添加。[结果]结果表明,试验组犊牛腹泻发病率减少35%,死亡率减少8%;平均每头治疗成本节省8.4元/头。[结论]犊牛日粮中添加酵母培养物AYC-X6,有利于建立健康稳定的瘤胃微生物菌群,对犊牛腹泻有很好的防治效果。     

Evaluation of hunter-harvested white-tailed deer for evidence of bovine viral diarrhea virus infection in Alabama.

Bovine viral diarrhea virus (BVDV) is one of the most relevant pathogens affecting today's cattle industries. Although great strides have been made in understanding this virus in cattle, little is known about the role of wildlife in the epidemiology of BVDV. While persistently infected cattle are the most important reservoir, free-ranging ungulates may become infected with BVDV as demonstrated by serosurveys and experimental infections. Therefore, free-ranging wildlife may maintain BVDV as the result of an independent cycle and may serve as a reservoir for the virus. Systematic studies on prevalence of BVDV-specific antibodies or frequency of persistent BVDV infection in North American wildlife are sparse, and no information is available from the southeastern United States. The objective of this study was to evaluate blood and skin samples from hunter-harvested white-tailed deer (Odocoileus virginianus) for evidence of BVDV infection. Virus-neutralizing antibodies were detected in 2 of 165 serum samples. Skin biopsy immunohistochemistry (IHC) was performed on samples from 406 deer using a BVDV-specific monoclonal antibody (MAb) (15c5), and BVDV antigen was detected in one sample. A similar IHC staining pattern was obtained using a second BVDV MAb (3.12F1). Viral antigen distribution in the skin sample of this deer resembled that found in persistently infected cattle and in a previously described persistently infected white-tailed deer; thus, the deer was presumed to be persistently infected. Evidence of BVDV infection in free-ranging white-tailed deer should encourage further systematic investigation of the prevalence of BVDV in wildlife.     

Anti-3AB antibodies in the Chinese yellow cattle infected by the O/Taiwan/99 foot-and-mouth disease virus.

The O/Taiwan/99 foot-and-mouth disease virus (FMDV), a South Asian topotype of serotype O, was introduced into Taiwan in 1999. The Chinese yellow cattle infected by the virus did not develop clinical lesions under experimental and field conditions. A blocking enzyme-linked immunosorbent assay (ELISA) kit with the 3AB antigen, a polypeptide of FMDV non-structural (NS) proteins, was used to evaluate the development and duration of anti-3AB antibodies, proving active viral replication, in the Chinese yellow cattle. The specificity of the assay was 99%, as was established with negative sera from regularly vaccinated and from na?ve cattle. The sensitivity tested with sera from naturally infected animals was approximately 64% and it was lower than that obtained by serum neutralization (SN) test. Under experimental infection, the Chinese yellow cattle developed lower anti-3AB antibodies than that developed in other species. Duration of anti-3AB antibodies was traced in two herds of naturally infected animals, indicating that anti-3AB antibodies persisted for approximately 6 months after outbreaks. On the basis of this study, we propose that the Chinese yellow cattle may have natural resistance, which limits viral replication and reduces the development of anti-3AB antibodies.     

Pulmonary and serum antibody responses elicited in zebu cattle experimentally infected with Mycoplasma mycoides subsp. mycoides SC by contact exposure

The purpose of the present study was to characterize the Mycoplasma mycoides subsp. mycoides small colony (MmmSC)-specific humoral immune response at both systemic and local levels in cattle experimentally infected with MmmSC, for a better understanding of the protective immune mechanisms against the disease. The disease was experimentally reproduced in zebu cattle by contact. Clinical signs, postmortem and microbiological findings were used to evaluate the degree of infection. Serum and bronchial lavage fluids (BAL) were collected sequentially, before contact and over a period of one year after contact. The kinetics of the different antibody isotypes to MmmSC was established. Based on the severity of the clinical signs, post mortem and microbiological findings, the animals were classified into three groups as acute form with deaths, sub-acute to chronic form and resistant animals. Seroconversion was never observed for the control animals throughout the duration of the experiment, nor for those classified as resistant. Instead, seroconversion was measured for all other cattle either with acute or sub-acute to chronic forms of the disease. For these animals, IgM, IgG1, IgG2 and IgA responses were detected in the serum and BAL samples. The kinetics of the IgM, IgG1 and IgG2 responses was nearly similar between both groups of animals. No evident correlation could thus be established between the levels of these isotypes and the severity of the disease. Levels of IgA were high in both BAL and serum samples of animals with sub-acute to chronic forms of the disease, and tended to persist throughout the entire experimental period. In contrast, animals with acute forms of the disease showed low levels of IgA in their BAL samples with none or very transient but low levels of IgA in the serum samples. Our results thus demonstrated that IgA is produced locally in MmmSC experimentally infected cattle by contact and may play a role in protection against contagious bovine pleuropneumonia.