Epidemiologic factors and isotype-specific antibody responses in serum and mucosal secretions of dairy calves with bovine coronavirus respiratory tract and enteric tract infections.

Blood, feces, and nasal swabs specimens were collected 12 to 24 hours after birth and then 3 times/week (blood only once per week) from one group of 10 calves until they were 10 weeks old and from a second group of 10 calves until they were 10 to 20 weeks old. Colostrum was collected from all calves' dams and tears from 5 randomly selected calves in the first group. All fecal and nasal specimens were assayed for bovine coronavirus (BCV) antigens by ELISA. Nasal epithelial cells were examined for BCV antigens by direct immunofluorescence. Isotype antibody titers to BCV in all samples from 5 calves in group 1 were evaluated by ELISA. Zinc sulfate turbidity (ZST) values were determined on the first serum samples taken from all calves in group 1. To determine whether any correlation existed between ZST values, isotype antibody titers to BCV (12 to 24 hours after birth), number of respiratory sick days, number of enteric sick days, or days to first shedding of virus, a Spearman rank order correlation coefficient was done. Bovine coronavirus respiratory tract and enteric tract infections were common on this farm. Most initial infections developed when calves were 1 to 3 weeks old; however, there were also multiple incidences of shedding of viral antigens or seroconversions at later times during the study. Persistence of infection or reinfection of the upper respiratory tract with BCV was common. Colostral antibody titers to BCV (IgG1) were in all cows at moderate amounts; however, calf serum antibody titers and ZST values (12 to 24 hours after birth) were highly variable.(ABSTRACT TRUNCATED AT 250 WORDS)     

Rotavirus infections in calves in dairy herds

Neonatal calf diarrhoea was studied in 115 calves of one dairy herd from January 1976 to June 1977. Two syndromes could be distinguished: a mild and short lasting 'early diarrhoea' within the first three days of life and a usually more severe 'late diarrhoea' from the fourth to the 14th day of life. The latter type of diarrhoea occurred almost exclusively during the first half of the year. Thirty-four out of 45 calves with late diarrhoea excreted rotaviruses, whereas only one of 34 calves with early diarrhoea excreted virus. In addition, rotavirus excretion was found in 11 calves that either remained healthy or had recovered from diarrhoea before virus was first detected. Similar findings were obtained in the spring of 1978 but in addition bovine coronavirus was recovered from four calves with late diarrhoea and from three healthy calves. One faecal sample obtained from a calf with diarrhoea on day 2 yielded K99+ Escherichia coli. Nearly all cows excreted rotavirus-specific antibodies in their colostrum but no relationship was found between the initial colostral antibody titre against rotavirus and the development of rotavirus-associated diarrhoea in the calf.     

Bovine respiratory syncytial virus and bovine coronavirus in Swedish organic and conventional dairy herds

Background

Infections with bovine respiratory syncytial virus (BRSV) and bovine coronavirus (BoCV) are endemic to the cattle populations in most countries, causing respiratory and/or enteric disease. It has been demonstrated that herds can remain free from these infections for several years also in high prevalence areas. Organically managed (OM) dairy herds have been shown to have lower seroprevalence of both viruses compared to conventionally managed (CM) herds. The objective of this study was to challenge the hypothesis of a lower occurrence of BRSV and BoCV in OM compared to CM dairy herds.In November 2011, May 2012 and May 2013 milk samples from four homebred primiparous cows were collected in 75 to 65 OM and 69 to 62 CM herds. The antibody status regarding BRSV and BoCV was analysed with commercial indirect ELISAs. Herds were classified as positive if at least one individual sample was positive.

Results

The prevalence of positive herds ranged from 73.4% to 82.3% for BRSV and from 76.8% to 85.3% for BoCV among OM and CM herds, over the three sampling occasions. There was no statistically significant difference between OM and CM herds at any sampling occasion. The incidence risk of newly infected herds did not differ statistically between OM and CM herds at any sampling occasion, neither for BRSV nor for BoCV. The incidence of herds turning sero-negative between samplings corresponded to the incidence of newly infected. Bulk tank milk (BTM) samples were also sampled in the herds and analysed. Several herds were negative on individual samples but positive in BTM. Herd-level data on production, health and reproduction were retrieved from VÄXA Sweden and the study herds were representative of the source population.

Conclusion

There was no difference in prevalence of or incidence risk for BRSV or BoCV between Swedish OM and CM herds. Because the incidence of herds becoming seropositive was balanced by herds becoming seronegative it should be possible to lower the prevalence of these two infections among Swedish dairy cattle herds if biosecurity is improved.

Electronic supplementary material

The online version of this article (doi:10.1186/s13028-014-0091-x) contains supplementary material, which is available to authorized users.     

A longitudinal study of verotoxin-producing Escherichia coli in two dairy goat herds

A longitudinal study was conducted on two dairy farms to investigate the pattern of shedding of verotoxin-producing Escherichia coli (VTEC) in goats. Faecal samples were taken from 20 goat kids once weekly during the first 4 weeks of life and then once every month for the next 5 months of life, and from 18 replacement animals and 15 adults once every month for 12 months. The proportion of samples containing VTEC was higher for replacement animals and adults (85.7% and 78.7%, respectively) than for goat kids (25.4%). About 90% of the VTEC colonies isolated from healthy goats belonged to five serogroups (O33, O76, O126, O146 and O166) but the most frequent serogroups of these isolates, except one, were different in the two herds studied. E. coli O157:H7 was found in three goat kids on only one occasion. None of the VTEC isolates, except the three E. coli O157:H7 isolates, was eae-positive. The patterns of shedding of VTEC in goat kids were variable, but, in contrast, most of the replacement animals and adults were persistent VTEC shedders. Our results show that isolates of VTEC O33, O76, O126, O146 and O166 are adapted for colonising the intestine of goats but that, in contrast, infection with VTEC O157:H7 in goats seems to be transient.     

Longitudinal study of bovine rotavirus group A in newborn calves from vaccinated and unvaccinated dairy herds

Reports of rotavirus excretion in calves usually result from cross-sectional studies, and in face of the conflicting results regarding protection of calves born to vaccinated dams against diarrhea, the aim of the present study was to evaluate rotavirus excretion in dairy calves born to vaccinated or unvaccinated dams, to identify the genotypes of bovine rotavirus group A (RVA) strains isolated from these animals as well as to investigate characteristics of the disease in naturally occurring circumstances throughout the first month of life. Five hundred fifty-two fecal samples were taken from 56 calves, 28 from each farm and, in the vaccinated herd, 11/281 samples (3.91%) taken from six different calves tested positive for RVA while in the unvaccinated herd, 3/271 samples (1.11%) taken from 3 different calves tested positive. The genotyping of the VP7 genes showed 91.2% nucleotide sequence identity to G6 genotype (NCDV strain), and for the VP4 gene, strains from the vaccinated herd were 96.6% related to B223 strain, while strains from the unvaccinated herd were 88% related to P[5] genotype (UK strain). Genotypes found in this study were G6P[11] in the vaccinated herd and G6P[5] in the unvaccinated herd. All calves infected with rotavirus presented an episode of diarrhea in the first month of life, and the discrepancy between the genotypes found in the commercial vaccine (G6P[1] and G10P[11]) and the rotavirus strains circulating in both vaccinated and unvaccinated herds show the importance of keeping constant surveillance in order to avoid potential causes of vaccination failure.     

Duration of bovine intramammary infections in commercial dairy herds

Data on the infection status of cows on seven commercial dairy farms were collected over 492 full lactations. Foremilk samples were taken at an average interval of five weeks. A total of 249 streptococcal and 433 staphylococcal infections were diagnosed. Spontaneous elimination occurred in 49 per cent of all streptococcal infections and in 54 per cent of Staphylococcus aureus infections. The average duration of spontaneously eliminated infections was 10.8 weeks for Streptococcus agalactiae, 9.9 weeks for Strep dysgalactiae, 10.4 weeks for Strep uberis and 12.8 weeks for Staph aureus. The average duration of infections persisting until drying off was 19.3 weeks for Strep agalactiae, 18.7 weeks for Strep dysgalactiae, 18.5 weeks for Strep uberis and 25.2 weeks for Staph aureus. The method and rate of elimination of infection as found in this analysis are of value for estimating new infection rates and selecting quarters for dry cow therapy.     

Prevalence of bovine group A rotavirus shedding among dairy calves in Ohio.

Fecal samples were collected from 450 neonatal calves, ranging from 1 to 30 days old, between May, 1988 and May, 1989 to estimate the prevalence of bovine group A rotavirus in a stratified random sample of Ohio dairy herds. Calves were from 47 dairy herds chosen to be representative of Ohio herds. Bovine group A rotavirus was detected in fecal samples by a cell culture immunofluorescence test (CCIF) and ELISA. Of 450 samples tested, 46 (10%) were positive by CCIF and 67 (15%) were positive by ELISA. The agreement beyond chance between the 2 assays was good (kappa = 0.65). The overall prevalence rate of rotavirus shedding was 16.4% (74/450). Forty-three percent (29/67) of the samples positive by ELISA were subgroup 1, none were subgroup 2, and the remaining 57% (38/67) could not be assigned to either subgroups 1 or 2. Thirty herds (62.5%) had at least 1 group A rotavirus-positive calf (mean number of samples per positive herd = 12.4), and 17 herds (37.5%) had no rotavirus-positive calves (mean number of samples per negative herd = 6.0). A live oral rotacoronavirus vaccine was used in neonatal calves of only 1 herd and 3 of 17 (17.6%) calves from this herd were positive for group A rotavirus. The percentage of the rotavirus-positive fecal samples from all calves (n = 450) when stratified by fecal consistency was as follows: 28.3% (13/46) had liquid feces; 25.6% (10/39) had semiliquid feces; 23.4% (22/94) had pasty feces; and 10.7% (29/271) had firm feces.(ABSTRACT TRUNCATED AT 250 WORDS)     

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.     

A longitudinal study of serological patterns of respiratory infections in nine infected Danish swine herds

Sixteen litters of seven pigs from each of nine Danish farrow-to-finish herds were followed to investigate the serological patterns caused by natural infection with Mycoplasma hyopneumoniae, Pasteurella multocida toxin and Actinobacillus pleuropneumoniae serotypes 2, 5–7, 12. In seven of the herds, pigs were followed as two separate cohorts started 4 weeks apart, and in two herds only one cohort was followed.

A total of 999 pigs were included in the study. The pigs were blood sampled at weaning and subsequently every fourth week until slaughter. All pigs were examined for antibodies against M. hyopneumoniae (enzyme-linked immunosorbent assay), P. multocida toxin (enzyme-linked immunosorbent assay) and A. pleuropneumoniae serotypes 2, 5–7, 12 (complement-fixation tests). The most-common pattern (28%) of seroconversion was that of pigs first seroconverting to A. pleuropneumoniae serotype 2, followed by seroconversion to M. hyopneumoniae. Each herd had a dominant serotype of A. pleuropneumoniae to which most pigs seroconverted. Seroconversion to the respiratory pathogens occurred mainly in the growing-to-finishing units (8–24 weeks). The risk of seroconversion to the P. multocida toxin was very low (<20%) and occurred late.

None, four and seven herds tested seropositive to PRRS and to swine influenza virus subtypes H3N2 and H1N1, respectively, when testing 10 pigs per herd (selected randomly among the study pigs) at the age of 20 weeks.     

A case-control study of Washington dairy herds experiencing drug residue violations in market calves

The purpose of this case-control study was to examine the association between management practices and the occurrence of violative drug residues in calves originating from Washington dairies. In 1992, 74 dairies were identified as first-time offenders sending to abattoirs calves less than 1 week of age that had violative residue levels. Of these, 56 answered a subset of previously validated management questions from the 1991–1992 US National Animal Health Monitoring System National Dairy Heifer Evaluation Program (NDHEP) study during a violation investigation and comprised the case group. The controls were the 51 randomly selected Washington dairies that participated in the NDHEP, completed the four NDHEP questionnaires, and had not been identified as having residue violations. Management factors investigated were those associated with maternity and pre-weaning hygiene, vaccination and preventive practices, type and management of liquid calf feed, and general management. Other factors included herd somatic cell count (SCC), the presence of clinical signs associated with diseases of body systems, and herd size. Significant associations were detected between violation occurrence and the management of calving cows, colostrum volume and management, and the person responsible for calf care. Significant associations but of the wrong direction were found between violation occurrence and type and management of liquid calf feed. No significant associations were detected between violation occurrence and the remaining management factors, herd size, animals entering the herd, or SCC.     

Nationwide survey of antibodies to bovine coronavirus in bulk milk from Swedish dairy herds.

Bulk milk samples from 2236 dairy herds randomly selected throughout Sweden in proportion to region and herd size were analysed for antibodies to bovine coronavirus (BCV) in an ELISA. The results were expressed as optical density (OD) values and an OD > 0.04 was considered positive. Eighty-nine per cent of the samples were antibody-positive and 52 per cent had high levels of antibodies to BCV (an OD > 0.70). There were significantly higher OD values (P < 0.001) and fewer antibody-negative samples (P < 0.001) from larger herds than from smaller herds. There were also significantly higher OD values and fewer antibody-negative samples from herds in southern Sweden than from herds in northern Sweden (P < 0.001 and P < 0.001, respectively). These results indicate a higher frequency of BCV infections in larger herds and in herds in southern Sweden.     

Efficacy of tulathromycin in the treatment of bovine respiratory disease associated with induced Mycoplasma bovis infections in young dairy calves

The efficacy of tulathromycin in the treatment of bovine respiratory disease (BRD) due to Mycoplasma bovis was determined following experimental infection. Two highly pathogenic strains of M. bovis (with minimum inhibitory concentration values for tulathromycin of 1 and >64 microg/ml) were inoculated into 145 calves. Four days after inoculation, calves with clinical BRD were treated subcutaneously with saline or tulathromycin (2.5 mg/kg). Compared with saline, BRD-related withdrawals, peak rectal temperatures, and lung lesion scores were significantly lower for tulathromycin-treated calves (P < .01). Tulathromycin was highly effective in the treatment of BRD due to M. bovis in calves regardless of the minimum inhibitory concentration of the challenge strain (1 or >64 microg/ml).     

A longitudinal study of the diversity and dynamics of Mycoplasma hyopneumoniae infections in pig herds

A longitudinal study was carried out to investigate the diversity and persistence of Mycoplasma hyopneumoniae (M. hyopneumoniae) strains in four infected pig herds. In each herd, 20 pigs were randomly selected and blood and/or bronchoalveolar lavage (BAL) fluid was collected at 6, 10, 14 and 26 weeks of age. In the BAL fluid, quantitative PCR and MLVA (multiple-locus variable number of tandem repeats (VNTR) analysis) testing were performed for detection and typing of M. hyopneumoniae strains, respectively. At 26 weeks of age, the prevalence and severity of lung lesions were recorded at slaughter (minimum 50 pigs belonging to the same batch as the investigated pigs). The percentage of pigs testing positive on qPCR increased from 35% at 6 weeks to 96% at 26 weeks of age. With MLVA testing, positive pigs were found from 14 weeks onwards. Within each herd, only one distinct strain was detected, although clonal variants were identified in two herds. In three of the herds, the strain remained present until slaughter age. The percentage of pigs with Mycoplasma-like lesions ranged from 38% to 98%, and the average pneumonia score ranged from 1.7 to 11.9, respectively. The present field study documented that within a herd, mainly one distinct M. hyopneumoniae strain was present that persisted in the same animals for at least 12 weeks. This implies that the immune response of the animals following infection is not able to rapidly clear the infection from the respiratory tract.     

Experimentally induced coronavirus infections in calves: viral replication in the respiratory and intestinal tracts

Eleven 3- to 50-day-old colostrum-deprived gnotobiotic calves and seven 25- to 63-day-old colostrum-deprived conventional calves were allotted into 3 groups. Each group was inoculated with a fecal isolate of bovine coronavirus via different routes: orally/intranasally OR/IN, No. 1 through 8, group 1 calves; OR, No. 9 through 13, group 2 calves; IN, No. 14 through 18, group 3 calves. Nasal swab specimens and fecal specimens were collected daily and were examined for coronavirus antigen by use of direct immunofluorescent staining (nasal epithelial cells) or by use of immune electron microscopy (fecal specimens). All but 4 calves (No. 11, 13, 17, and 18) were euthanatized on postinoculation days (PID) 3 to 7. Calves 11 and 17 became severely dehydrated and died at PID 5. Calves 13 and 18 were evaluated for nasal and fecal shedding of coronavirus through PID 14. Distribution of coronavirus antigen in the respiratory and intestinal tracts of the 14 euthanatized calves was evaluated by use of direct immunofluorescent staining. All calves developed profuse diarrhea by PID 2 to 4; however, calves did not develop clinical signs of respiratory tract disease before euthanasia or death. Inoculated calves shed coronavirus in their feces as detected by use of immune electron microscopy. Infected nasal epithelial cells were detected in all but 2 orally inoculated calves (No. 9 and 10). Route of inoculation influenced the sequence of initial detection of coronavirus antigen from fecal specimens or nasal swab specimens.(ABSTRACT TRUNCATED AT 250 WORDS)     

Clinical and pathological observations on spontaneous bovine respiratory syncytial virus infections in calves

A clinical, pathological and microbiological study was made of acute spontaneous bovine respiratory syncytial virus infection in calves. Characteristic features were atelectatic areas, which had an exudative and, or, necrotising bronchiolitis with syncytial giant cells in the epithelial lining and in the lumina of these bronchioles. Restricted to these areas both bronchiolar and alveolar immunofluorescence for bovine respiratory syncytial virus were seen. Complications were severe interstitial oedema, interstitial emphysema and a catarrhal or fibrinous pneumonia due to secondary bacterial invasion.     

Evaluation of concurrent shedding of bovine coronavirus via the respiratory tract and enteric route in feedlot cattle

OBJECTIVE: To assess the relationship between shedding of bovine coronavirus (BCV) via the respiratory tract and enteric routes and the association with weight gain in feedlot cattle. ANIMALS: 56 crossbred steers. PROCEDURES: Paired fecal samples and nasal swab specimens were obtained and were tested for BCV, using antigen-capture ELISA. Paired serum samples obtained were tested for antibodies to BCV, using antibody-detection ELISA. Information was collected on weight gain, clinical signs, and treatments for enteric and respiratory tract disease during the study period. RESULTS: Number of samples positive for bovine respiratory coronavirus (BRCV) or bovine enteric coro navirus (BECV) was 37/224 (17%) and 48/223 (22%), respectively. Some cattle (25/46, 45%) shed BECV and BRCV. There were 25/29 (86%) cattle positive for BECV that shed BRCV, but only 1/27 (4%) cattle negative to BECV shed BRCV. Twenty-seven of 48 (56%) paired nasal swab specimens and fecal samples positive for BECV were positive for BRCV. In contrast, only 10/175 (6%) paired nasal swab specimens and fecal samples negative for BECV were positive for BRCV. Only shedding of BECV was associated with significantly reduced weight gain. Seroconversion to BCV during the 21 days after arrival was detected in 95% of the cattle tested. CONCLUSIONS AND CLINICAL IMPLICATIONS: Feedlot cattle infected with BCV after transport shed BCV from the respiratory tract and in the feces. Fecal shedding of BCV was associated with significantly reduced weight gain. Developing appropriate control measures for BCV infections could help reduce the decreased weight gain observed among infected feedlot cattle.