Microbial diversity involved in the etiology of a bovine respiratory disease outbreak in a dairy calf rearing unit

The etiological agents involved in a bovine respiratory disease (BRD) outbreak were investigated in a dairy heifer calf rearing unit from southern Brazil. A battery of PCR assays was performed to detect the most common viruses and bacteria associated with BRD, such as bovine viral diarrhea virus (BVDV), bovine respiratory syncytial virus (BRSV), bovine alphaherpesvirus 1 (BoHV-1), bovine coronavirus (BCoV), bovine parainfluenza virus 3 (BPIV-3), Mannheimia haemolytica, Pasteurella multocida, Histophilus somni, and Mycoplasma bovis. Bronchoalveolar lavage fluid (BALF) samples were taken from 21 heifer calves (symptomatic n = 15; asymptomatic n = 6) that, during the occurrence of the BDR outbreak, were aged between 6 and 90 days. At least one microorganism was detected in 85.7 % (18/21) of the BALF samples. Mixed infections were more frequent (72.2 %) than single infections (27.7 %). The interactions between viruses and bacteria were the most common in coinfections (55.5 %). The frequencies of BRD agents were 38.1 % for BRSV, 28.6 % for BVDV, 33.3 % for BCoV, 42.85 % for P. multocida, 33.3 % for M. bovis, and 19 % for H. somni. BoHV-1, BPIV-3, and M. haemolytica were not identified in any of the 21 BALF samples. Considering that BALF and not nasal swabs were analyzed, these results demonstrate the etiological multiplicity that may be involved in BRD outbreaks in dairy calves.     

Frequency of BCoV detection by a semi-nested PCR assay in faeces of calves from Brazilian cattle herds

Bovine coronavirus (BCoV) is one of the main causes of neonatal calf diarrhoea. Several diagnostic assays have been employed to detect the presence of the virus in stool samples from calves. Despite this, the frequency of BCoV infection among Brazilian and even South American cattle herds has yet to be well characterised. This study describes the occurrence of BCoV infection among calves from dairy and beef herds in four Brazilian states. A total of 282 stool samples from 1 to 60-day-old calves were evaluated for the presence of BCoV by a semi-nested (SN) PCR assay. The animals were from herds (n = 23) located in three geographical regions in Brazil (south, southeast, and center-west). The specific BCoV amplicon was detected in 15.6% (44/282) of the faecal specimens examined, of which 95.4% (42/44) were from diarrhoeic and 4.6% (2/44) from asymptomatic calves. The specificity of the SN-PCR amplicons was evaluated by restriction fragment length polymorphism (RFLP) analysis. The results show that the BCoV is widespread, mainly among calves from 16 to 30-days-old (p = 0.0023), and verify the association between BCoV infection and clinical signs of diarrhoea (p = 0.005). These findings emphasise the importance of this virus in enteric infections of Brazilian cattle herds.     

Molecular and phylogenetic characterization of bovine coronavirus virus isolated from dairy cattle in Central Region,Thailand

Tropical Animal Health and Production - Bovine coronavirus (BCoV) is involved mainly in enteric infections in cattle. This study reports the first molecular detection of BCoV in a diarrhea outbreak...     

Severe outbreak of bovine coronavirus infection in dairy cattle during the warmer season

A severe outbreak of enteric and respiratory disease associated with bovine coronavirus (BCoV) infection is described. The outbreak occurred in a dairy herd of southern Italy in the first decade of September 2006, when summer temperatures were still recorded, affecting calves, heifers and adult cows, with a marked decrease in milk production. By virus isolation and RT-PCR targeting the S gene, BCoV was identified as the etiological agent of the outbreak, whereas bacteriological, parasitological and toxicological investigations failed to detect other causes of disease. BCoV strains with 99-100% nucleotide identity in the S gene were isolated from nasal, ocular and rectal swabs, thus proving the absence of separate clusters of virus on the basis of tissue tropism. Sequence analysis of the haemagglutination-esterase and spike proteins of the strain detected in one rectal sample (339/06) showed a high genetic relatedness with recent BCoV isolates (98-99% amino acid identity), with several unique amino acid substitutions in the S protein. The BCoV outbreak described in this paper presents interesting aspects: (i) the occurrence of a severe form of disease in the warmer season; (ii) the simultaneous presence of respiratory and enteric disease; (iii) the involvement of young as well as adult cattle.     

Enteric parasitosis in northern Thailand dairy heifers and heifer calves

A cross-sectional study was designed to: (1) determine the prevalences of enteric parasitic infections in dairy heifers and heifer calves (Bos taurus) in northern Thailand, and (2) determine the risk factors associated with the observed prevalences of infection. A stratified random sample of 87 farms was selected for study, and fecal and blood samples were collected from 439 out of 450 heifers and heifer calves from these farms. Fecal samples were processed by floatation and modified Benedek sedimentation methods, and then examined microscopically for the presence of enteric parasitic ova. Complete blood counts typically were within the reference range (done using standard methods). The overall prevalence for enteric parasites in heifers and heifer calves was 54%; most were of trematodes (41%) and nematodes (26%). Risk-factors analysis at the farm level yielded no significant results. Increased age significantly increased the odds of enteric parasite infection (OR=1.02, 95% CI 1.01-1.04).     

A simulation of Johne's disease control

A dynamic and stochastic simulation model (the "JohneSSim model") was developed to evaluate the economic and epidemiological effects of different strategies for control of paratuberculosis in dairy herds. Animals occupy one of the six defined infection states; the spread of Johne's disease is modeled with five infection routes. Many different dairy farm situations can be simulated. Control strategies that can be simulated are: (1) test-and-cull; (2) calf hygiene management; (3) vaccination and (4) grouping of animals. Losses are caused by: (1) reduced milk production; (2) diagnosis and treatment costs; (3) lower slaughter value of cows and (4) sub-optimal culling. The benefits were calculated as reduction in the losses caused by Johne's disease; the costs of each strategy were calculated on the basis of actual costs of each item; and net present value (NPV) was calculated as benefits minus costs. Herd and prevalence data from The Netherlands and Pennsylvania, USA were used. In both situations, a low true mean prevalence within 20 years could be reached only when all calf management tools were applied. The Dutch control program (PPN) was on average economically attractive (with or without labor costs, the average NPV was Euro 1183 and 12,397, respectively). In Pennsylvania, contract heifer rearing and improved calf hygiene reduced the prevalence effectively and had large economic benefits (US$ 43,917 for 20-year period) if the calves were sent to the heifer facility while very young. Validation with data from 21 infected Dutch dairy farms (as well as face-validation: comparison of the results of the JohneSSim model with experiences of Johne's experts) supported the basic assumptions in the model.     

Influence of herd structure and type of virus introduction on the spread of bovine viral diarrhoea virus (BVDV) within a dairy herd

A herd is a population structured into groups not all equally in contact, which may influence within-herd spread of pathogens. Herd structure varies among cattle herds. However, published models of the spread of bovine viral diarrhoea virus (BVDV) assume no herd structure or a unique structure chosen as a representative. Our objective was to identify--for different index cases introduced into an initially BVDV--free dairy herd - risky (favourable) herd structures, which increased (decreased) BVDV spread and persistence compared to a reference structure. Classically, dairy herds are divided into calves, young heifers, bred heifers, lactating cows and dry cows. In the reference scenario, groups are all equally in contact. We evaluated the effect of isolating or merging groups. Three index cases were tested: an open persistently-infected (PI) heifer, an open transiently-infected heifer, an immune heifer carrying a PI foetus. Merging all groups and merging calves and lactating cows were risky scenarios. Isolating each group, isolating lactating cows from other groups, and merging calves and young heifers were favourable scenarios. In most structures, the most risky index cases were the following: first, the entry of a PI heifer; second, the birth of a PI calf; last, the entry of a transiently-infected heifer. Recommendations for dairy herds are to raise young animals together before breeding and to isolate lactating cows from others as much as possible. These recommendations will be less efficient if a PI adult enters into the herd.     

犊牛病毒性腹泻的发病机理与防控措施

犊牛腹泻是严重危害犊牛成长的常见病之一,治疗不及时可导致犊牛死亡和发育不良,给奶牛养殖业造成巨大的经济损失。临床上犊牛腹泻的发病原因主要有非感染性因素和感染性因素,感染性因素主要包括细菌性感染、病毒性感染和寄生虫感染。主要针对病毒性感染引起的犊牛腹泻的发病机理和防控措施进行了介绍,以期对奶牛养殖业的健康发展提供理论依据。     

牛冠状病毒、牛轮状病毒和致病性大肠杆菌混合感染致犊牛腹泻的研究

为了明确新疆石河子某规模化奶牛场犊牛腹泻病死率较高的原因。本研究对腹泻犊牛的粪样及病死犊牛肠道内容物进行病原检测,并对分离菌株进行毒力基因检测、耐药基因检测、动物致病性试验及药敏试验。最终明确病因主要由牛冠状病毒(BCoV)和牛轮状病毒(BRV)和大肠杆菌混合感染引起。药敏试验表明,分离到的大肠杆菌对28种抗生素产生了严重的耐药,仅对多粘菌素和呋喃妥因敏感,并且发现该菌同时携带2种毒力基因和10种耐药基因。本研究分离的一株大肠杆菌携带有丰富的耐药基因,具有多重耐药性,为该奶牛场上临床治疗加大了难度。而本试验结果为该养殖场提供科学的临床药物指导,为该牛场治疗此次犊牛腹泻提供了依据,同时为新疆犊牛腹泻混合感染的防控提供了病例参考和技术资料。     

Dynamics of virus infections involved in the bovine respiratory disease complex in Swedish dairy herds

The dynamics of bovine respiratory syncytial virus (BRSV), bovine parainfluenza virus 3 (PIV-3), bovine corona virus (BCoV) and bovine viral diarrhoea virus (BVDV) infections were studied in 118 dairy herds in south western Sweden. By using serology on paired samples from three approximately 7 vs. approximately 15-month-old calves per herd, the propagation of infections was investigated over about a 1-year period. The results implied that at least 74% of calves had experienced one or more of the monitored infections at the age of approximately 7 months (Sample 1, Spring); 30%, 48%, 34% and 8% were seropositive to BRSV, PIV-3, BCoV and BVDV, respectively. Seroconversions to BRSV, PIV-3, BCoV and BVDV occurred in 26%, 38%, 50% and 3% of seronegative animals and 63% had antibodies against two or more infections at approximately 15 months (Sample 2). In total, 90-97% of animals that were seropositive in Sample 1 remained positive in Sample 2. A significant association was found between BVDV and BCoV (P = 0.01). Moreover, a significantly higher proportion of herds in which no calves had a recorded history of respiratory disease (n = 15) were classified as negative to all four infections monitored when compared to herds in which disease was observed (P = 0.0002). This study showed a high infection burden in young animals and effective spread of BRSV, PIV-3 and BCoV in one area of Sweden. BVDV infections were restricted to a few herds, reflecting the effect of a voluntary control program against BVDV in Sweden.     

Estimating the costs of rearing young dairy cattle in the Netherlands using a simulation model that accounts for uncertainty related to diseases

The costs of rearing young dairy cattle are a part of the cost of the price of milk, as rearing produces the future dairy cows. As most dairy farmers are not aware of the rearing costs, the rearing of dairy replacements often does not get the attention it deserves. Calculating the distribution of the rearing costs throughout the rearing process is difficult as the costs are correlated with biological processes, such as variation in growth rate and disease uncertainty. In this study, a calf level simulation model was built to estimate the rearing costs and their distribution from 2 weeks of age until first calving in the Netherlands. The uncertainties related to calf diseases (calf scours and bovine respiratory disease) were included, in which both the probabilities of disease and the effects of diseases (growth reduction) differ at different ages. In addition, growth was modeled stochastically and in a detailed manner using a two-phase growth function. The total cost of rearing young dairy cattle was estimated as €1567 per successfully reared heifer and varied between €1423 and €1715. Reducing the age of first calving by 1 month reduced the total cost between 2.6% and 5.7%. The difference in the average cost of rearing between heifers that calved at 24 months and those calving at 30 months was €400 per heifer reared. Average rearing costs were especially influenced by labor efficiency and cost of feed. The rearing costs of a heifer that experienced disease at least once (20% of the simulated heifers) were on average €95 higher than those of healthy heifers. Hence, for an individual diseased heifer, disease costs can be rather high, while the relative contribution to the average rearing cost for a standard Dutch dairy farm is low (approx. 3%). Overall, the model developed proved to be a useful tool to investigate the total cost of rearing young dairy cattle, providing insights to dairy farmers with respect to the cost-efficiency of their own rearing management.     

A longitudinal study of bovine coronavirus enteric and respiratory infections in dairy calves in two herds in Ohio

This prospective longitudinal study examined the epidemiology and disease syndrome associated with bovine coronavirus (BCV) infections in a cohort of 8 conventional calves from 0 to 120 days of age, in two dairy herds in Ohio. The periods of respiratory shedding of BCV were determined by direct immunofluorescent (DIF) staining of nasal epithelial cells and ELISA of nasal swab supernatant fluids. The periods of fecal shedding of BCV were determined by ELISA and immunoelectron microscopy (IEM). The isotype-specific antibody titers to BCV in serum (at selected intervals between 0 and 120 days of age) and the post-suckling (24 to 48 h after birth) total immunoglobulin levels were examined by ELISA and zinc sulfate turbidity tests, respectively. Of the 8 calves studied, 4 had evidence of BCV respiratory (by DIF or ELISA) or enteric infections (by IEM or ELISA) in association with diarrhea or rhinitis, even though 7 of 8 calves showed increases in one or more serum antibody isotypes to BCV and 6 of 8 calves showed BCV respiratory or enteric antigen shedding by ELISA. Serological antibody titer increases occurred in 3 calves before 30 days of age and in 4 calves after 30 days of age; two of the latter calves had a second rise in serum antibody titers to BCV after the initial rise. A serological antibody titer increase was not observed in one calf. This suggests that BCV infections may be very common in a closed herd and may occur in older calves, although many may be subclinical and some may be recurrent. There were no statistically significant correlations between total serum immunoglobulin levels or BCV antibody isotype titers in serum (24-48 h after birth) and clinical disease or infection by BCV; however, calves with low levels of IgA BCV antibodies in serum (24-48 h after birth) had a significantly greater average number of days with diarrhea than those calves having high levels of IgA BCV-specific antibodies in serum.     

An outbreak of mucosal disease in a dairy herd

An outbreak of mucosal disease (MD) was studied in a dairy herd, comprising 12 cows, 9 heifers and 18 calves. During a period of 1 month, six 5 to 8 month-old calves showed typical signs of MD. They all died or were killed in extremis after 2-8 days with progressively worsening clinical signs. Post mortem lesions were examined in one calf. Non-cytopathogenic MD virus was isolated from serum or tissues from 3 clinically affected calves and from 1 healthy heifer. All cows and heifers except for the viremic one possessed neutralizing antibodies against bovine pestivirus. According to the current MD-pathogenesis concept, the affected calves were probably infected transplacentally during the first half of foetal life with pestivirus from the persistently infected heifer in the herd.     

Investigation of an outbreak of mucosal disease in a beef cattle herd in southwestern Saskatchewan.

This study describes the epidemiological investigation of an outbreak of mucosal disease that occurred on a ranch in southwestern Saskatchewan. Over a six-month period during the fall and winter of 1991-1992, in a herd of 515 beef cattle and 96 bison, 20 yearling cattle from a group of 105 housed in one feedlot pen died from mucosal disease. A further eight yearlings were slaughtered for salvage because they were at risk of dying from mucosal disease. Mucosal disease mortalities were the first observed evidence of fetal infections with bovine viral diarrhea virus in this herd. Animals that died from mucosal disease exhibited signs of ill thrift prior to death. Deaths from mucosal disease were confined to the progeny of one herd of beef cows. Following an outbreak of fetal infection with bovine viral diarrhea virus during 1989-1990, at least 28 (22%) of the 128 calves born from this herd of cows in the spring of 1990 were persistently infected with bovine viral diarrhea virus. However, only one calf born from this herd in 1991, and five calves born from all herds in 1992 were persistently infected. Of the five persistently infected calves born in 1992, three were born to persistently infected replacement heifers born in 1990. These heifers calved without assistance in 1992, but only one of their calves survived past three days of age, and it was persistently infected. In January 1992, 82% of the total herd had reciprocal antibody titers to bovine viral diarrhea virus of > or = 1024 which suggested a high level of herd immunity to bovine viral diarrhea virus.(ABSTRACT TRUNCATED AT 250 WORDS)     

An overview of calf diarrhea - infectious etiology,diagnosis, and intervention

Calf diarrhea is a commonly reported disease in young animals, and still a major cause of productivity and economic loss to cattle producers worldwide. In the report of the 2007 National Animal Health Monitoring System for U.S. dairy, half of the deaths among unweaned calves was attributed to diarrhea. Multiple pathogens are known or postulated to cause or contribute to calf diarrhea development. Other factors including both the environment and management practices influence disease severity or outcomes. The multifactorial nature of calf diarrhea makes this disease hard to control effectively in modern cow-calf operations. The purpose of this review is to provide a better understanding of a) the ecology and pathogenesis of well-known and potential bovine enteric pathogens implicated in calf diarrhea, b) describe diagnostic tests used to detect various enteric pathogens along with their pros and cons, and c) propose improved intervention strategies for treating calf diarrhea.     

Coronavirus as an agent of neonatal calf diarrhea in a Chinese dairy cattle farm.

Neonatal calf diarrhea is a significant health problem in dairy industry in the whole world. Although the aetiological agents of neonatal diarrhea are diverse, it is obvious that viruses play an important role. One of them is bovine coronavirus (BCV). Since BCV was discovered (MEBUS et al., 1969), there have been many published reports describing the virus and its importance in calves. In China, we first investigated the seroepidemiological status of BCV infections in cattle (YAO et al., 1990). The results showed that the incidence of infections with BCV in cattle in different chinese regions are high. Further work on direct diagnosis of BCV as a causative agent of diarrhea was therefore necessary. In the last years we have developed diagnostic methods including a monoclonal antibody-based ELISA to detect BCV and other diarrheal viruses. In this study, the diagnosis of an outbreak of BCV in chinese dairy cattle is described.     

一起奶牛腹泻病的病原学诊断

辽宁省某奶牛养殖场10～30日龄犊牛发生腹泻,为查明病因,我们对送检的18份犊牛腹泻样本分别进行牛轮状病毒(BRV)、牛冠状病毒(BCoV)、牛病毒性腹泻病毒(BVDV)、产肠毒素大肠杆菌(ETEC)、沙门氏菌(Salmonella)和安氏隐孢子虫(C. andersoni)的PCR检测。结果显示:18份犊牛腹泻样本中,BRV、BCoV、BVDV的检出率分别为83.3%(15/18)、88.9%(16/18)、61.1%(11/18),这3种病原的混合感染率较高,其他病原均未检出,说明该奶牛场的犊牛腹泻主要由BRV、BCoV、BVDV混合感染引起。     

Dairy calf management,morbidity and mortality in Ontario Holstein herds. I. The data

Heifer calf management practices and clinical outcomes were studied on 104 randomly selected Holstein dairy farms in southwestern Ontario between October 1980 and July 1983. Data were collected at both the farm level (all farms) and the individual calf level (1968 calves, 35 farms).Farm-level management data were collected by means of questionnaires and farm visits. Calf-level management data were recorded by farmers on forms provided. Treatments for disease and mortality data were recorded by the farmers on the calves up to the age of weaning, the age at which calves were no longer fed milk or milk substitutes on a regular basis.Farm size ranged from 23 to 154 calvings per year. Farm-level mortality rates per six-month season (winter/summer) were skewed, with a mean of about 6%, a median of zero, and a range of 67%. Morbidity rates were similarly skewed. Four percent of liveborn heifer calves died, 20% were treated for scours, and 15% were treated for pneumonia before the age of weaning.Stated farm policies on calf rearing were implemented to varying degrees on different farms, as estimated from individual calf data. This posed particular problems for interpreting farm-level data, since the danger of committing an ecologic fallacy was high. The data set described in this paper formed the basis for an observational study of the interlationships of heifer calf management and clinical outcomes.     

Attaching and effacing Escherichia coli infection as a cause of diarrhea in young calves

A form of enteric Escherichia coli infection was identified in 60 calves from 59 farming operations. The E coli responsible for these infections principally colonized the colon, inducing a distinctive lesion described as attaching and effacing. Hemorrhagic enterocolitis or blood in the feces was observed on 40% of the farms. Of affected calves, 86.6% were dairy calves (average age, 11.8 days). Forty-four calves were infected concurrently with other enteropathogens (cryptosporidia, rotavirus, coronavirus, enterotoxigenic E coli, bovine viral diarrhea virus, coccidia). Verotoxin-producing E coli was recovered from 31 calves; 8 were serotype O111:NM isolates, 3 were serotype O5:NM, and 1 was serotype O26:NM.