Shedding of malignant catarrhal fever virus by wildebeest calves

Malignant catarrhal fever virus (MCFV) was isolated from nasal and ocular secretions of wildebeest calves up to 3 months old. The virus was also isolated from explant cultures of cornea and nasal turbinates. It is suggested that MCFV replicates in the cornea and turbinates of young wildebeest calves less than 4 months old.MCFV was not isolated from secretions of calves older than 3 months, but virus neutralizing antibodies were found in their nasal secretions. The appearance of antibodies in the nasal secretions coincided with the cessation of virus shedding. The failure of calves over 3 months old to shed MCFV might explain the seasonal nature of bovine MCFV infection.     

Study on prevalence of bovine viral diarrhoea virus (BVDV) antibodies in 29 Italian dairy herds with reproductive problems

An epidemiological survey on prevalence distribution of antibodies to BVDV was carried out in dairy cattle herds during 1995-1996 in northern Italy. A total of 704 serum samples from 29 non-vaccinated herds reported to have reproductive problems were tested for serum neutralising antibodies. In each herd, sampling was based on the stratification by age into five classes (< 6 months old calves, 6-12 months old calves, pregnant heifers, uniparous, pluriparous). Overall, 53.3% of samples were serologically positive, with the lowest ratio in 6-12 months old calves (37.9%) and the highest in pluriparous cows (71.2%).     

Epidemiological study of bovine respiratory syncytial virus infections in calves: influence of maternal antibodies on the outcome of disease

A prospective epidemiological survey on bovine respiratory syncytial virus (BRSV) infections in calves was carried out on 21 dairy farms during one BRSV epidemic season. Special attention was paid to the role of maternal antibodies. On 15 farms the spread of the virus was demonstrated during the investigation period and on eight farms this was accompanied by an outbreak of acute respiratory disease. Disease seldom occurred in calves younger than two weeks old and the most severe disease was observed in calves from one to three months old. Although maternal antibodies did not effectively prevent the disease, both the incidence and severity of disease were inversely related to the level of specific maternal antibodies. Two serodiagnostic techniques were compared. In calves older than three months from herds with disease outbreaks associated with bovine respiratory syncytial virus the diagnosis was established in 80 per cent of the animals by an increase in IgG titre against BRSV and in 77 per cent by the detection of BRSV specific IgM. In comparison, only 10 per cent of the calves younger than three months were positive by IgG serodiagnosis, and 51 per cent by IgM serodiagnosis. On farms where the spread of the virus was accompanied by an outbreak of clinical disease more calves were present, a higher proportion of the calves was younger than three months, and calves of all ages were more often housed together.     

Variations in the immune response to natural Schistosoma mattheei infections in calves born to infected mothers

During previous work Schistosoma antibodies and circulating antigens were detected at birth in the serum from some calves born to Schistosoma mattheei infected mothers. The objectives of the present survey were: (1) to investigate the proportion of calves, born to cows infected with S. mattheei, which have specific antibodies and circulating schistosome antigens present in their serum at birth and (2) to investigate whether the presence or absence of these specific antibodies and/or circulating antigens at birth may affect the pattern of a natural S. mattheei infection in calves from 4 to 5 months of age, when the colostral antibodies are thought to be of negligible importance. A total of 28 calves born to infected mothers were randomly selected. Faeces, serum and colostrum samples were collected from the cows at calving, serum samples were collected from the calves at birth (day 0), after intake of colostrum (day 1) and monthly thereafter up to the age of 10 months. Both serum and colostrum samples were analysed for IgG(H+L) against SWAP mattheei and schistosome circulating anodic antigen (CAA) levels. The calves were exposed to a natural challenge from the age of 4-5 months. Faecal samples were collected from the calves monthly, starting at an age of 5 months up to 10 months, and were examined for faecal egg counts. Nine (group 1) out of the 28 calves were found to have specific antibodies in their serum at birth, in 5 of them CAA levels were also detected. In the other 19 calves (group 2) no IgG(H+L) or CAA were detected. At the end of the study faecal egg counts and CAA levels were significantly lower in calves from group 1 compared to group 2. Results confirm earlier work that specific antibodies and circulating antigens may be present in serum from calves at birth, and show that these calves have lower faecal egg counts and CAA levels after exposure to a natural challenge.     

Detection of neutralizing antibodies in calves after single vaccination against foot-and-mouth disease virus type ASIA 1 in the field]

On June 20th 1984 appeared the first FMD-Type ASIA 1 outbreak in Greece. Around the outbreak all susceptible animals were vaccinated with ASIA 1 vaccine produced by IFFA Mereiux. Three weeks after this first vaccination blood samples have been collected and examined for neutralizing antibodies. From 101 examined calves 37 were younger than 6 months, 63 between 6-11 months and one was 12 months old. The titer of the first group was less than 1.2 in 14 and greater than 1.8 in 8 calves. By the second group (63 animals) the titer was less than 1.2 in 28 and greater than 1.8 in 11 calves. The 12 months old calf had a titer of 2.1. Generally the titer only of 59 out of the 101 examined calves was greater than or equal to 1.2 (59%). That means that the vaccine used had a weak immunogenicity.     

Association of diarrhea in cattle with torovirus infections on farms.

An epidemiologic survey was performed to determine the incidence of torovirus infections in 2 disease entities of cattle: diarrhea of replacement calves up to 2 months old, and winter dysentery of adult cattle. Samples were obtained from 187 diarrheal and 115 healthy calves from 15 farms, as well as 149 diarrheal and 67 healthy cows from 27 farms with or without winter dysentery. Enzyme-linked immunosorbent assays for detection of torovirus, rotavirus, and coronavirus antigen in feces, and of torovirus and coronavirus antibodies in serum were used to monitor infections in these groups. Torovirus was detected in 9 of the 15 farms in the study, and in 6% of calves with diarrhea, which was significantly higher than in healthy calves (2%). Seroconversion to torovirus was found significantly more often after winter dysentery episodes than on farms without a disease history; coronavirus seroconversion was less common.     

Epidemiologic studies of the detection of viral infection agents in calf losses in the Weser-Ems region

In 961 calves up to an age of 6 months which were sent to the animal health center in Oldenburg between March 1987 and March 1990 for necropsy the results of determination of different viruses were calculated: BVD-, rota-, corona-, parainfluenza-3- (PI-3)-, bovine herpes-1 (BHV-1)- and bovine respiratory syncytial virus (BRSV). In 122 and 104 randomly collected health calves of 22 farms antibodies against BRSV and bovine adeno virus-types 5, 7 and 8 were determined. 50.1% of the necropsied calves were one and two weeks old. In this group in 40.2% rotavirus and in 19.0% coronavirus could be isolated. All over the calves the frequencies of isolated viruses were 13.3% for BVDV, 4.6% for BRSV, 3.2% for BHV-1, and 2.1% for PI-3. The percentages of positive findings for rota- and coronavirus increased up to 7 days after birth, and thereafter both decreased. The frequencies of BVDV and BRSV were higher in older groups. The frequency of PI-3 was low and remained constantly. Infections with rota-, corona- and with both viruses were accompanied by BVDV in 11.3, 5.3 and 14.3%, respectively. Against bovine adenoviruses and BRSV in the first 8 weeks and after 14 weeks of life in more than 70% of the calves antibodies were detected.     

The frequency and geographic distribution of Giardia infections in ruminants in Switzerland

In various districts (Cantons) of Switzerland 815 calves (a few days up to 6 months old), 382 lambs and 20 young goats (both groups 1-6 months old) were selected randomly for a single coprological examination (flotation method) for Giardia infection. In average 26.6% of the calves, 29.8% of the lambs and 4 of 20 young goats excreted Giardia cysts. In 9 Cantons the percentages of cyst excretors among the calves varied between 15 and 32, but these differences were not significant. Further there were no significant differences in the frequency of cyst excretion between calves of 3 different breeds and 2 age groups (up to 3 months old and 3 to 6 months). The intensity of cyst excretion was high and varied in random samples between 4.1 x 10(3) and 3.0 x 10(5) cysts per g of faeces in calves and between 2.2 x 10(3) and 1.6 x 10(5) in lambs. In 5 of 7 farms where calves and lambs were maintained simultaneously both animal species were Giardia infected. As expected, trophozoites of Giardia isolates from calves and lambs belonged to the Giardia duodenalis type and could not be differentiated on a morphological basis. Giardia cysts from calves (average measurements: 13.7 x 9.1 microns) and lambs (13.8 x 9.2 microns) were indistinguishable both morphologically and morphometrically. The results indicate that Giardia infections are frequent and geographically widely distributed in calves and lambs in Switzerland.     

Eradication of bovine leukemia virus infection from a high-prevalence herd, using radioimmunoassay for identification of infected animals

Radioimmunoassay (RIA), using the virion glycoprotein antigen, was applied in an attempt to eradicate bovine leukemia virus (BLV) infection from a herd in which virtually all the adult cattle are infected. Considering that most calves born to BLV-infected cows are negative for BLV at birth and remain negative for the first several months of life, the eradication program was based on the identification and isolation of the BLV-free calves born to infected cows. Twenty-five calves raised on colostrum and milk from their infected dams were classified as BLV-free on the basis of negative results in the RIA at 6 to 8 and 9 to 11 months of age. These animals were maintained in either complete (10 calves) or partial (15 calves) isolation from infected cattle and were examined at regular intervals for BLV and BLV antibodies. With the exception of 1 calf in the group raised in partial isolation, the animals have remained free of BLV up to the time of the last evaluation, when they were 32 to 35 months old. At these ages, more than 90% of the nonisolated cattle in the herd are BLV-positive. The data also show that this eradication trial would have failed if, in the initial procedure used to classify the calves as BLV-free, the agar gel immunodiffusion test instead of the RIA had been used. Inasmuch as the 25 calves in this study were fed colostrum and milk from their dams, the fact that only 1 of the calves became infected during the 26 to 29 months of observation provides further evidence that milk-borne transmission of BLV is infrequent and perhaps inconsequential.     

Duration of colostral antibodies to bovine leukemia virus by two serologic tests

The duration of detectable colostral antibodies to the glycoprotein antigen of bovine leukemia virus was studied in calves which were born to bovine leukemia virus-infected cows, but showed no serologic evidence of prenatal infection. Colostral antibodies detectable by an agar-gel immunodiffusion test (AGIT) persisted for less than 1 month to 6 months (mean 2.9 months) in the 139 calves examined. Colostral antibodies were detectable 1 to 5 months longer by radioimmunoprecipitation assay than by the AGIT in 22 of the 24 calves studied comparatively. The mean duration of colostral antibodies in those 24 calves was 3.8 months (min-max, 2 to 6 months) for the AGIT and 6.0 months (min-max, 4 to 9 months) for the radioimmunoprecipitation assay.     

体细胞克隆牛0～12月龄生长的测定研究

通过对5头体细胞克隆母犊牛及其同期自然繁殖出生的荷斯坦母犊牛初生期、6月龄、12月龄的体重、体尺指标测定,初步分析了其生长发育速度的变化规律。结果表明:(1)克隆牛初生重53.67±7.00kg,明显高于自繁奶牛(P<0.01),6月龄体重141.00±16.49kg,明显低于自繁奶牛(P<0.01),12月龄体重302.80±32.17kg,与自繁奶牛基本相当;(2)克隆牛0～6月龄期间平均日增重0.70±0.11kg明显低于自繁奶牛(P<0.01),6～12月龄期间平均日增重0.90±0.12kg,与自繁奶牛基本相当(P>0.05),0～12月龄期间平均日增重0.70±0.11kg,与自繁奶牛基本相当(P>0.05);(3)克隆牛初生体尺指标明显大于自繁奶牛(P<0.01),6月龄体尺指标明显小于自繁奶牛(P<0.01),12月龄体尺指标与自繁奶牛相当(P>0.05);(4)克隆牛0～6月龄期间体尺平均增长明显低于自繁奶牛(P<0.01),6～12月龄期间体尺平均增长明显高于自繁奶牛(P<0.01),0～12月龄期间体尺平均增长明显低于自繁奶牛(P<0.01)。     

Udder immunization for the protection of calves from salmonella infections. 2. Estimation of serological findings of colostrum with regard to its protective activity

Colostrum from cows which had been mammary gland vaccinated against salmonellosis were tested for antibodies by four different serological tests. Results from these tests were related to the protective activity for artificially infected calves. In opposition to agglutinating antibodies and antibodies detected by ELISA, complement fixing antibodies of the IgG1 class were shown to transfer early protection in artificially infected calves.     

Control of Boophilus microplus ticks in cattle calves by immunization with a recombinant Bm86 glucoprotein antigen preparation.

Forty Egyptian native cattle calves of 4-6 months old randomly allocated into two groups of twenty animals each were used to assess the effect of immunization of animals with a recombinant Bm86 antigen derived from Boophilus microplus ticks on induction of immunity that could protect calves during tick season. The immunization protocol involved two injections administered intramuscularly, the first was applied with complete Freund's adjuvant and the second was given with incomplete Freund's adjuvant two months later. Control calves were given saline plus adjuvant. Immunization reduced the number of adult ticks developing from a subsequent challenge infestation by 78% in immunized calves. Vaccination also, significantly reduced the weight of adult ticks in immunized calves (30.51%). The results of skin delayed hypersensitivity reaction revealed that the diameter of sites injected with the recombinant Bm86 antigen was significantly larger in immunized calves than those in controls. Analysis of the immune response indicated that there was a significant increase in the level of IgG and IgA antibodies in serum of immunized calves and protection from reinfestation was correlated with the levels of circulating antibodies.     

Persistence of antibodies and anamnestic response in calves vaccinated with inactivated infectious bovine rhinotracheitis virus and parainfluenza-3 virus vaccines

Persistence of antibodies in calves vaccinated with 2 types of inactivated infectious bovine rhinotracheitis (IBR) virus and parainfluenza-3 (PI-3) virus vaccines were determined. Calves seronegative for IBR and PI-3 viruses were inoculated with 2 doses of inactivated IBR virus-PI-3 virus vaccines administered 2 weeks apart. Blood samples were obtained from the calves for serum at 2 weeks, 6 months, and 1 year after vaccination. The serums were tested by serum-neutralization tests. Antibody response to the vaccines persisted on a declining scale for 1 year. The anamnestic responses to the vaccines were determined by inoculating the same calves with a booster dose of vaccine 1 year after the original 2 doses were given. Blood samples were obtained from the calves for serum 2 weeks later. The serums were tested by serum-neutralization tests. The single booster dose of vaccine elicited an anamnestic response to both IBR and PI-3 viruses.     

Duration of active and colostrum-derived passive antibodies to bovine viral diarrhea virus in calves.

Duration of active and colostrum-derived passive antibodies to bovine viral diarrhea virus was studied in 14 calves. Five calves born with actively induced antibodies to bovine viral diarrhea virus retained high titers during the year of observation. Colostrum-derived antibodies to bovine viral diarrhea virus in nine calves declined at an expected rate for the first four to six months of age. However, titers of six of these calves increased at five to eight months of age and either remained constant or increased through one year of age. Bovine viral diarrhea virus antibody titers of the other three calves declined at a constant rate to less than 1:4 by nine to 12 months of age.     

Antibody titer against bovine respiratory syncytial virus in colostrum-fed dairy calves born in various seasons.

OBJECTIVE: To determine antibody titer against bovine respiratory syncytial virus (BRSV) in dairy calves on farms and to investigate whether passively acquired antibody titers differ in calves born in various seasons. SAMPLE POPULATION: Serum samples from 129 colostrum-fed replacement calves in 8 dairy herds. PROCEDURE: A standard ELISA was used to determine BRSV-specific antibodies in serum samples obtained monthly, and antibody titers for calves born in various seasons were compared. RESULTS: BRSV-specific antibody titer in colostrum-fed dairy calves decreased to undetectable values at 3 to 4 months old. Calves born in winter generally had lower titers, compared with those for calves born in other seasons (P < 0.05). Titers in calves born in seasons other than winter did not differ. CONCLUSIONS AND CLINICAL RELEVANCE: Calves born in winter generally have lower BRSV-specific antibody titers, which may be caused by generally lower antibody titers in colostrum or by factors influencing colostrum intake.     

Investigation of bovine viral diarrhea virus infections in a range beef cattle herd

Bovine viral diarrhea virus (BVDV) infections resulting in clinical disease developed in calves, despite vaccination of dams and high maternal BVDV antibody titers in calves. Eight persistently infected (PI) calves born to immunocompetent dams were identified in the herd. Neutralizing BVDV antibody titers of PI calves had decreased greatly by the time the calves were 1 to 2 months old. Antibody titers of PI calves decreased more rapidly than antibody titers of calves that were not PI. Reduced antibody titers in PI calves allowed detection of BVDV in serum specimens of all PI calves by the time they were 8 weeks old. Persistent infection in suspect calves was detectable serologically and was confirmed by virologic examination of serum specimens 4 months after weaning, when the calves were 9 months old. Growth rates were reduced in viremic calves.     

犊牛超数排卵方法的研究

本试验采用不同超排处理方案对不同月龄犊牛(1~6月龄)进行超排处理,以得出犊牛超数排卵的最佳方案、最佳月龄和重复超排的最佳时间间隔。结果表明,超排方案4的超排效果最好,平均采卵数(80.0枚)、平均回收卵数(43.3枚)和平均可用卵数(37.8枚)均显著高于其他4个方案(P<0.05),表明超排方案4比较适合3月龄犊牛的超数排卵;2、3、4、5月龄犊牛应用超排方案4的超排效果较好,差异不显著,平均可用卵数分别为33.5、41.0、34.5、32.8枚,1、6月龄犊牛的超排效果显著差于其他4个月龄组(P<0.05),平均可用卵数分别为10.8、18.3枚,表明超排方案4处理犊牛的最佳月龄为2~5月龄;超排间隔2周组(6.3枚)平均可用卵数效果显著差于间隔3、4和5周组(16.7、23.7、23.0枚)(P<0.05),超排间隔3、4、5周组之间超排效果差异不显著,表明犊牛重复超排处理的最佳时间间隔为3~4周。     

Immunoglobulin M-specific enzyme-linked immunosorbent assay for serodiagnosis of bovine respiratory syncytial virus infections

An antibody-capture enzyme-linked immunosorbent assay (ELISA) for detection of immunoglobulin (Ig) M antibodies to bovine respiratory syncytial virus (BRSV) in cattle was developed. Monoclonal antibody to bovine IgM was used as the catching antibody. The IgM-ELISA was used, as well as a BRSV-specific IgG ELISA to determine the kinetics of IgM and IgG antibody responses to BRSV infections in cattle. High IgM and IgG antibody titers developed after naturally occurring or induced BRSV infection of calves (6 to 7 months old). Induced infection resulted in an IgM response that was first detectable at postinoculation day (PID) 11 reached a maximum at PID 13, and became undetectable again about PID 28. An IgG response also was detected by PID 11. However, a maximum response was not reached before PID 23, and titers remained high (until PID 80). In naturally occurring infection, IgM and IgG responses in calves were observed in the acute phase of epizootics of respiratory tract disease. Patterns of IgM and IgG response curves were similar to those observed in experimentally infected calves. The involvement of BRSV in an epizootic of respiratory tract disease in 8 calves (2 to 3 weeks old) was demonstrated by the detection of BRSV in several lung lavage samples. All calves had existing IgG antibodies to BRSV which were interpreted to be maternally derived. None of the calves responded with an increase in IgG antibody titer. However, a weak but distinct BRSV IgM antibody response occurred in 6 calves.(ABSTRACT TRUNCATED AT 250 WORDS)     

Humoral and cellular responses in calves experimentally infected with bovine leukemia virus (BLV)

In order to elucidate whether infection by Bovine Leukemia Virus (BLV) might induce an immunodeficient state, we inoculated sixteen calves with BLV. The calves were followed up for two years and were tested for humoral and cellular responses using various parameters, namely the appearance of antibodies to the BLV antigens, the changes in the numbers of lymphocytes involved, and the ratio between the two main populations of lymphocytes. Antibodies to the BLV antigens were of both the IgG and the IgM classes of immunoglobulins. The levels of antibodies of the IgM class were higher than those of IgG. There was a temporary decrease of reactive antibodies to the BLV antigens, to below detectable levels, during the 14-24 weeks post infection. A significant decrease in the level of plasma IgM was found in all BLV infected calves exhibiting lymphocytosis, while the level of IgG in the plasma of all experimental calves did not diverge significantly from the initial values, throughout the experiment. BLV infection was followed by lymphocytosis of B-cells in most infected calves, which persisted for the whole course of the experiment, while a decrease in the population of T-cells in peripheral blood was observed for a period of several months in all infected calves.