Search

Briefly the history of maedi-visna and the major clinical symptoms are described. Examples are presented to demonstrate that the genetic composition of a breed determines whether or not sheep become sick after an infection with maedi-visna virus (mvv) or develop solely specific antibodies. The major pathway of transmission is not colostrum and milk, but a cell containing increased nasal discharge in cases of respiratory distress. The role of the environment and prophylactic measures against parasites is stressed, because even sheep of highly susceptible breeds can survive an infection under optimal conditions. The virus and subsequently the disease simply die out. The cooperation between clinicians and laboratories is necessary.

Bovine Herpesvirus Type 1 (BHV1) is the aetiological agent of a number of diseases and not only of IBR, namely infectious pustular vulvovaginitis (IPV), infectious balanoposthitis (IBP), conjunctivitis, encephalomyelitis, mastitis, abortion, enteritis, and lesions in the interdigital space. The serological identical strains differ, however, in some aspects. Typical genital strains usually cause a mild illness, sometimes not even detected clinically, but serologically. They hamper eradication programmes and do not cause IBR when inoculated intranasally. The other--modern--strains are, however, always able to induce a severe disease in the genital tracts. But infection of field or vaccine virus leads to the development of humoral and cell-mediated immunity. The latter is, however, not transmitted to neonates via colostrum. BHV1 antibodies can be found in bovines in all continents, and in many wild species. Prevalences vary greatly depending on herd size and management. Because seronegative cattle play a role in international trade a number of European countries have eradicated BHV1, with very high costs involved. Marker and conventional vaccines can prevent disease but not infection followed by the state of latency. The genomes of several strains, including the marker strains can remain latent in the same animal and be reactivated after stress or injection of corticosteroids. For the detection of humoral antibodies the ELISA is widely used. It is useful for testing bulk milk samples for antibodies derived from field virus and conventional vaccines but not from gE-deleted marker vaccines. Importing countries should consider only vaccinated animals for import. They should require that the animals are seronegative prior to vaccination.

The bovine leukaemia virus (BLV) is a retrovirus that infects mainly B lymphocytes of cattle, but proviral DNA can also be isolated from monocytes/macrophages. This study investigated the effect of BLV infection on surface antigens on freshly isolated peripheral blood monocytes and cultured monocyte-derived macrophages, with and without lipopolysaccharide (LPS) stimulation. The effect of BLV infection on phagocytic activity of CD14+ monocytes was also assessed. The percentage of monocytes expressing the surface antigens CD11b, CD32 (FcgammaRII), MHC class II and the surface antigen recognised by mAb DH59B were increased in BLV-positive cattle. In contrast, expression intensity of all markers was low in samples from BLV-positive cattle. CD14+ monocytes from BLV-positive cattle showed less Fcgamma-receptor-mediated phagocytosis compared to monocytes from BLV-negative cattle. After 7 days in culture, there was evidence for shedding/downregulation of surface antigens on monocyte-derived macrophages, in particular on cells from BLV-positive cattle. LPS stimulation decreased the percentage of cells expressing the measured markers in monocyte-derived macrophages taken from BLV-negative cattle, but not in cultures derived from BLV-positive cattle. The results provide further evidence for an altered function of monocytes and macrophages in BLV-infected cattle.

This study assesses quantitatively the risk that other countries, in particular those within the European Union, have incurred by importing cattle from the United Kingdom during the period before or shortly after the ban on the import of live breeding stock was introduced in 1989. It does this by assessing the probability that animals imported from the UK in a certain year would have become a detected BSE case, had they not been exported. Using the annual incidence rates available for separate birth cohorts and a given culling rate, a cumulative incidence for each birth cohort was calculated. These figures were then combined with the numbers of live breeding cattle imported from the UK into the other countries of the EU, to give an import-related risk index for each country, assuming that their culling rates were similar to that in Great Britain. The countries could thus be categorised in terms of the number of cases of BSE they might have expected.

In an attempt to determine whether scrapie infectivity can be found in the peripheral nervous system of a scrapie-diseased sheep, mice were inoculated intracerebrally or intraperitoneally with 10-fold dilutions of homogenates of Nervus (N.) axillaris, N. ulnaris, N. medianus, N. ischiadicus, N. tibialis, N. fibularis, and N.saphenus. Mice were observed for clinical signs of scrapie for 700 days and their brains were analyzed for accumulation of pathological prion protein by immunoblot. Substantial amounts of infectivity were found in all peripheral nerves tested except N.saphenus. Infectivity at titers of approximately 10(4.5) mouse infectious units (MIU)/g were detected in N. axillaris and N. ischiadicus, of approximately 10(3.0) MIU/g in N. ulnaris, N. medianus, N. tibialis, and N.fibularis, and of 10(6) MIU/g in the cerebellum. Since muscles are traversed by the nerve tracts tested, mutton of scrapie-diseased animals should not be regarded as being free of scrapie agent.

Twelve cattle with body wts ranging from 100 to 250 kg were treated using various doses and routes for four days with an E. coli derived alpha-hybrid interferon. The lowest parenteral doses (10(4) units per kg body wt) and the orally administered interferon did not lead to any disturbances, whereas the higher dosages led to marked changes in body temperature, pulse and respiration rates. Animals with the highest dose (10(8) units per kg body wt) became extremely distressed. The blood picture showed distinct changes, with very low leukocyte counts during treatment, which took weeks to recover. It is suggested that the dosages that did not lead to clinical symptoms are best suited for prophylactic or therapeutic purposes.

Four groups of six cattle were vaccinated from two to five times at 6 month intervals with two different trivalent FMD vaccines licensed in the given year. The FMDV type A strains in the vaccines designated A5F and A5B were closely related. Three months after the last vaccination the cattle were challenged by contact with animals inoculated with the original field strain A5B. The inoculated animals developed typical FMD symptoms with vesicles in the mouth and on the feet. Those cattle which had received vaccines that did not contain strain A5B also became severely sick, even after five vaccinations. Animals vaccinated twice with type B containing vaccine were also not completely protected. A safe protection can obviously only be achieved for fairly short periods of time if vaccine and challenge strain are homologous. It is proposed to change the rules of licensing, to speed up the procedure to vaccinate in cases of outbreaks. The need for further research, especially into improving vaccines, is stressed.

Three seronegative sheep persistently infected with Border disease virus and six seropositive, non-viraemic sheep were examined for the cellular distribution of the agent. These animals originated from a closed flock which had been kept in an isolation facility for 5 years. They were killed and immediately necropsied. There were no gross abnormalities other than reduced body weight of the persistently infected sheep. Two samples of each major organ were collected. The first sample was fixed by immersion in formalin and processed for histological examination, which showed no lesions unequivocally attributable to the viral infection. The second sample was snap-frozen for immunohistochemical examination. This revealed viral antigen in all organs of the persistently infected, but in none of the seropositive animals. The infected cells included smooth muscle cells of hollow organs and blood vessels, epithelial cells of the alimentary tract and urogenital organs, lymphocytes in lymphoid organs, endocrine cells, neurons and glial cell.

A method for extracting RNA from animal-derived materials that provides foot-and-mouth disease viral template suitable for Tth polymerase-dependent synthesis of cDNA and subsequent PCR is described. Viral genomes were detected in less than 24 h. Nasal swabs that can be easily and repeatedly collected, proved suitable for virus detection by PCR, even during the asymptomatic stages of infection.

Following transmission studies cerebrospinal fluid and synovia were checked for the presence of specific antibodies from ten seronegative goats derived from seropositive females and from 16 seropositive goats showing typical clinical symptoms. In the samples from the seronegative goats it was not possible to detect any specific antibodies whereas in 14 of the 16 seropositive goats specific antibodies were found in the synovia and in two goats specific antibodies could be found in the cerebrospinal fluid. The conclusion was that the local clinical symptoms may be the result of an antigen-antibody reaction.

Within nine months, enzootic bovine leukosis (EBL) occurred in 23 well documented herds. Eight of them (= 35%) had previously conducted the eradication programme as laid down by law. This proportion is tenfold higher than anticipated from the average incidence rate since 1978. The conclusion is drawn that a higher risk for reinfection exists for herds previously infected and cleaned than for those that never had leukosis before. For such cases hypotheses are presented. In one case clear evidence for one of the hypotheses was obtained. In case of re-occurrence of EBL in a previously cleaned herd it is proposed to examine the white blood picture of the sero-positive animals. If hematologically positive cattle are detected, they should be removed from the herd including their offspring.

Single oral (p.o.) or intravenous (i.v.) doses of biotin were given to four cattle (400-450 kg body weight) in two consecutive tests two weeks apart. Dosages were p.o. 20, 40, 80 or 160 and i.v. 5, 10, 20, 40 mg biotin per 300 kg body weight. A three-compartment model was used to describe the course of serum concentrations with time. After i.v. administration, terminal half-lives of about 8 h were found. Areas under the curves were linearly related to both the p.o. and the i.v. doses. The systemically available fraction of the p.o. dose was 50 to 60%. On the basis of kinetic parameters, the biotin uptake via the feed was estimated to be 2.5 mg/day, which was about half of that estimated to be in the hay consumed. The data suggest that there was no relevant ruminal synthesis of biotin.

A trial using 12 yearling heifers was carried out to test whether biotin metabolism and bioavailability are influenced by continuous dietary supplementation with biotin. Six of these heifers received no biotin supplementation (controls), while six received a daily dietary supplement of 20 mg biotin over the whole experimental period of four months. During each of three test periods (on days 14 and 21, 56 and 63, and 118 and 124), single test dosages of 40 mg (oral) and 5 mg (intravenous) biotin were given to each animal in a crossover test design. Blood samples were collected up to 72 h after each of these single doses, and at approximately two-weekly intervals for the assessment of baseline values. Serum biotin levels were determined by an ELSA test. Areas under the curves (AUC) were calculated as the target parameter for the assessment of the bioavailability of orally administered biotin. Serum biotin baseline levels were 300-800 ng/l in the controls and 3000-8000 ng/l in the supplemented animals. In both groups, AUC values in the first test period (days 14 and 21) were significantly higher than in subsequent periods. However, the biotin supplementation showed no significant effect. There was no significant difference in elimination half-lives between groups with and without biotin supplementation. The range was 5-18 h. Furthermore, there was no significant difference in the bioavailability of biotin between the test periods or between the biotin-supplemented and unsupplemented animals. Overall bioavailability was 48%.

Antiserum to a peptide corresponding to the 135-154 sequence of capsid protein VP1 of the foot-and-mouth disease virus O1 Kaufbeuren was raised in a pig. Although this serum contained neutralizing antibodies, the pig showed clinical symptoms after challenge. Virus isolated from this pig was identified as a mutant, with changes at positions 50, 198 and 211 of VP1 and at position 209 of VP2. This mutant, as well as a plaque isolate of it, differing from the challenge virus at positions 198 on VP1 (alanine being substituted for glutamic acid) and 209 on VP2 (histidine being substituted for tyrosine) resisted neutralization by the anti-peptide serum also in vitro. The same was observed with the O1 Kaufbeuren-related strain O1 Burgwedel, isolated from cattle in the field. It had substitutions only at positions 43 and 101 on VP1. The results show that neutralization epitopes flanking positions 145-147 on VP1 are modulated by other capsid protein parts. These parts seem to be important for neutralization escape in natural FMDV host species.

After a review on the viral agents playing a role in diseases of cattle those related to the occurrence in the genital tract are described. They may be causing abortion or local reactions leading to a reduced fertility and/or be of importance for the embryo transfer. Bovine herpesvirus type 1 (BHV1) and the bovine virus diarrhoea virus (BVDV) are the agents most widely distributed in Europe. Both are of economic importance, described in detail and vaccines available discussed.

The use of gl deleted live vaccines against Aujeszky's disease (AD) facilitates to differentiate vaccinated from field-virus infected animals. In this study different modes of vaccination were tried to find out how sheep can be protected from a lethal infection with ADV. It could clearly be demonstrated that Aujeszky disease virus (ADV) is spread by horizontal transmission from infected pigs to sheep. The nasal discharges of infected pigs contained a maximum of 10(8.75)TCID50/g mucus at days 3 and 4 p.i. and those of the contact-pigs 10(8.5)TCID50/g mucus at days 6 and 7 after contact. Non-vaccinated contact sheep were infected horizontally by the pigs. The highest titres ranged from 10(6.25) to 10(7.5)TCID50/g mucus. These animals were sacrificed at day 5 p.i. exhibiting acute symptoms of AD. The nasal discharge of vaccinated sheep contained much lower amounts of ADV (maximum: 10(4.25)TCID50/g mucus). All surviving animals had developed antibodies. Following challenge with the ADV-strain NIA3, no febrile response or virus-shedding was observed in sheep vaccinated 2x s.c. or 2x i.m. with a gl deleted live vaccine, whereas sheep, vaccinated only 1x i.m. (4 out of 4 animals) or 1x i.m. (3 out of 4 animals) or 1x i.n. and 1x i.m. (1 out of 4 animals) had to be sacrificed after showing acute symptoms of AD. In conclusion it can be stated that a double parental vaccination with a gl deleted live vaccine protects sheep against a field-virus AD infection.

The RNase mismatch cleavage method was examined for its efficiency of indicating single-base sequence differences in the capsid protein-coding regions of different foot-and-mouth disease virus subtype O1 strains. The method was found suitable for indicating such differences. RNase A as well as RNase T1 contributed to substrate conversion. Examples for the cleavage of eleven different single-base mismatches in RNA double-strands are now known. All virus genomes found to differ from each other exhibited three or more non-neighboured single-base sequence differences. Other genomes found to be indistinguishable by this method were those of a recent field isolate adapted to cell culture, and those of a vaccine production strain; its progeny was transmitted to pig and cow and then analyzed. The results suggest that host change does not necessarily select for antigenic variant virus, and that virus submitted to some kind of selection pressure is changed at more than one position.

Infections caused by BHV1 are very common in Europe, but the disease pattern is quite different: the diseases of the genital tract are most common, those of the respiratory tract vary in intensity and prevalence. Digestive disorders connected with BHV1 are in general only observed in calves and mainly in Belgium. Virus strains causing abortion or encephalitis are only present in a few countries. The same is true for BHV1 induced mastitis. Dermatitis and lesions in the interdigital space seem to be a rare event. BHV1 infections are frequently complicated by bacterial secondary infections, but there is evidence that BHV1 infections can occur simultaneously with bovine virus diarrhoea (BVD) and/or parainfluenza-3 (PI 3) virus. The biggest problem associated with BHV1 infection is the ability of the agent to become latent following a primary infection. The genome of the virus probably remains during the life of the animal in the ganglia of the region where the primary infection occurred. No vaccination can overcome this latent stage. By prophylactic vaccination it is possible to prevent an outbreak of clinical disease but it is impossible to prevent infection followed by the establishment of latency. Eradication programmes in Austria, Denmark and Switzerland have removed most of the seropositive cattle from the bovine populations. Currently a sanitary programme is also being conducted in Germany.

The effects of an inactivated strain of Aujeszky's disease vaccine in cattle were investigated. It has not been possible to use vaccines licensed for use in pigs successfully in cattle even though cattle develop neutralizing antibodies to these vaccines. The addition of zinc compounds to the vaccines resulted in protection in cattle. The basis for the use of zinc is discussed. A mutant based vaccine was effective following local administration, but was not when administered parenterally. Anti-prostaglandin was not effective either, despite its successful use in sheep when administered with BHV1. The vaccine presents a prospect for immunising dogs and cats, and the addition of zinc compounds to other drugs and inducers is discussed.

Antibodies raised in cattle against foot-and-mouth disease virus by vaccination or by experimental infection were distinguished. Vaccination elicited only antibodies to virus capsid proteins and the polymerase 3D. Virus replication in cattle elicited additional antibodies directed against the non-structural proteins 2B, 2C, 3AB1, and/or 3C irrespective of prior vaccination or whether the cattle exhibited symptoms of disease. Non-permissive mice inoculated with virus responded in the same way, indicating that antibodies raised due to the transient presence of antigen are safely recognized by the method applied which was radioimmunoprecipitation. All kinds of infections were thus detected and it was possible to differentiate between cattle exposed or not exposed to challenge in the field, and further between protected animals and possible virus carriers.

Following an outbreak of FMD caused by an A5 strain in the spring of 1984, ten cattle were vaccinated with samples of the five commercial vaccines used for the vaccination campaign in that year, i.e. two animals per vaccine. Six weeks later the cattle were challenged by contact with animals inoculated with the virus strain isolated from the field outbreak. Seven of the ten cattle became severely ill, exhibiting the typical symptoms of FMD, one animal did not show any clinical symptoms, the remaining two weak ones that might have escaped recognition by the cattlemen. Virus could be recovered from the vaccinated animals from days 2 to 10 following contact with the non-vaccinated infected cattle. It was concluded that a single vaccination does not protect cattle against the isolate.

A purified concentrated BHV1 antigen that had been tested in field trials was also tested under isolated conditions in BHV1 positive and negative cattle. The antigen proved to act specifically even after storage for 2 years at +4 degrees C or for 6 months at 37 degrees C. The best results were obtained when the test was read 48-72 hours after the injection, which is in agreement with the field trials. The increase in skin thickness decreased unless boosted by infection or vaccination gradually. The test is unsuitable to control a vaccination programme. There was no correlation between the increase in thickness and humoral antibody titers. Repeated application of the intradermal injection of the antigen did not result in seroconversion in seronegative cattle. The biological limits of the test evaluation are discussed.

Bovine leucosis infection rates were calculated for two years in a naturally infected dairy herd in which serologically positive animals were not preferentially culled. Transmission of infection was found to occur mainly during the winter housing period. No variation in susceptibility to infection with age was found and young animals did not show a prolonged time from infection to sero-conversion.

The infectious bovine rhinotracheitis (IBR) virus belongs to the group of herpes viruses. It causes in cattle a severe disease predominantly in the upper respiratory tract. Morbidity rate is 100 percent, mortality - depending on hygienic and other factors - ranges from 0-15 percent. The IBR virus is serologically indistinguishable from the infect pustulat vulvovaginitis (IPV) virus which causes disorders of the genital tract in both male and female cattle. Possibly the IPV virus is the older of the two. Already in the twenties it had been isolated and described in Europe whereas IBR virus was first isolated from feedlot cattle in the USA during 1955/1956. Most likely - experiments also gave a hint - the IPV virus increased its virulence for the respiratory tract by rapid and numerous passages as this was only possible in accumulations of tremendous heads of animals. Vaccines both live attenuated and killed ones have been developed. Killed ones are always administered parenterally; the live ones are either intramuscularly injected or locally sprayed (into the nasal cavity). Immunity is developed within 3 weeks, however, if vaccinated animals are challenged, virus is again shed for a number of days. Cattle thereby do not exhibit any symptoms of disease. This is true following any kind of vaccination (live or killed). After local administration of live vaccines, however, the production of interferon by the cells of the respiratory tract is remarkable whereas parenterally administration of vaccine does not lead to that.

The inconsistency in naming and labeling bovine herpesviruses (BHVs), other than BHV types 1 and 2 (BHV-1 and BHV-2), found in the literature is reviewed. To resolve the confusion and misunderstanding caused by the use of BHV-3, BHV-4 and BHV-5 for the same kind of BHVs, the most used label BHV-4 is proposed for designating Movar-type BHVs (which also were named 'orphan viruses' or 'cytomegaloviruses').

The program under discussion is based on results obtained during transmission studies in which specific antibodies were detected in the immunodiffusion test earlier than antigen in peripheral blood leukocytes. Furthermore, it could be demonstrated that seroconversion does not seem to occur later than 3 months after transmission of the infectious agent. The results obtained in 11 herds are presented. The program is as follows: when the result of the immunodiffusion test becomes available all positive animals above 6 months of age are immediately removed from the herd. The remaining animals are checked at intervals of 3 months and sero-positives are always instantly removed. In pursuing the program a number of herds have obviously reachend 2 years old.

The absolute amounts of immunoglobulins contained in twenty-five samples of colostrum were determined. It was found that the quality of the colostrum is approximately the same for the first nine hours following parturition. The secretion of a cow following an abortion, however, does not have the quality of colostrum and should therefore not be saved to feed newborn calves. Detailed studies concerning the transfer of colostral antibodies to the newborn showed that ideally two liters of colostrum should be given within the first twelve hours. If the calf is derived from a heifer, a young cow or from a newly introduced animal it should receive 50% of its colostrum from an older cow of the herd. The colostrum can be kept in a frozen state for 15 years without losing too much of its original quality. The amounts of immunoglobulins and specific antibodies (against infectious Bovine Rhinotracheitis and Parainfluenza-3) transferred were remarkably high and most likely due to those infections the dams had suffered from. It is proposed that programs should be introduced whereby dams are regularly vaccinated during the late gestation period. The vaccines used and their composition have to depend on the diseases prevalent in the individual countries and regions.

To evaluate the hygienic risk involved in using baculoviruses for insect pest control, safety studies are required. Pigs were chosen as representative test animals of commercial and agricultural importance. The tests were aimed at detecting virus propagation, immune reactions, and signs of acute infection (changes in body temperature and hematology profile, swelling of lymph nodes). Four of five animals inoculated with nuclear polyhedrosis virus showed a slight temperature rise at day 2 postinfection. After day 4 postinfection, no differences between infected animals and controls were observed. In the bioassay, virus activity could be recovered from fecal samples; however, no activity was found in organ extracts. The data did not indicate hygienic risks involved in the application of nuclear polyhedrosis virus, especially that from Mamestra brassicae, in biological pest control.