Microbiology of calf diarrhoea in southern Britain

Faeces samples from calves with diarrhoea in 45 outbreaks were examined for six enteropathogens. Rotavirus and coronavirus were detected by ELISA in 208 (42 per cent) and 69 (14 per cent) of 490 calves respectively; calici-like viruses were detected by electron microscopy in 14 of 132 calves (11 per cent). Cryptosporidium were detected in 106 of 465 (23 per cent), Salmonella species in 58 of 490 (12 per cent) and enterotoxigenic Escherichia coli bearing the K99 adhesin (K99+ E coli) in nine of 310 calves (3 per cent). In the faeces of 20 per cent of calves with diarrhoea more than one enteropathogen was detected; in 31 per cent no enteropathogen was found. Faces samples from 385 healthy calves in the same outbreaks were also examined. There was a significant statistical association of disease with the presence of rotavirus, coronavirus, Cryptosporidium and Salmonella species (P less than 0.001). Healthy calves were not examined for calici-like viruses and the association of K99+ E coli with disease was not analysed because there were too few positive samples. Rotavirus infections were more common in dairy herds and single suckler beef herds whereas Salmonella infections were more often found in calf rearing units. Cryptosporidium were more common in single and multiple suckler beef herds. K99+ E coli were found in one dairy herd and one multiple suckler beef herd both with unhygienic calving accommodation. Variations in coronavirus detection among different farm types were not statistically significant. In this survey rotavirus was the most commonly detected agent in calf diarrhoea and Cryptosporidium were found in approximately one quarter of affected calves. Infection with Salmonella species was widespread, but K99+ E coli infections were less common in the United Kingdom than in other countries.     

Aetiology of diarrhoea in young calves

Faeces samples were collected from 302 untreated calves on the day of onset of diarrhoea and from 49 healthy calves at 32 farms experiencing outbreaks of diarrhoea. At least four diarrhoeic calves were sampled on each farm, and samples were examined for rotavirus, coronavirus, cryptosporidium, enterotoxigenic Escherichia coli and Salmonella species. Although all these enteropathogens were excreted more frequently by the diarrhoeic than by the healthy calves, the difference was significant overall only for rotavirus. Rotavirus was excreted by 18 per cent of healthy calves, coronavirus by 4 per cent, cryptosporidium by 14 per cent, and no enterotoxigenic E coli or Salmonella species were detected. The most common enteropathogen in diarrhoeic calves was rotavirus, which was excreted by more than half the diarrhoeic calves on 18 farms. Coronavirus was excreted at a similar high prevalence on one farm, cryptosporidium on five farms and enterotoxigenic E coli on three farms. Concurrent infection with two or more microorganisms occurred in 15 per cent of diarrhoeic calves. There was no difference in the isolation rate of campylobacters between diarrhoeic and healthy calves.     

Rotavirus infections associated with diarrhoea in calves in Egypt

The successful isolation and identification of rotavirus from newborn calves with diarrhoea is reported for the first time in Egypt. From 25 faecal samples taken from diarrhoeic calves, ten virus isolates were found to give cytopathogenic effects on bovine embryonic kidney cells. Three of the isolates were identified as rotavirus using fluorescent antibody staining, serum-neutralization, complement fixation and agar gel precipitation. The complement fixation test revealed the presence of rotavirus antibodies in 18 of 105 serum samples obtained from other calves slaughtered at Cairo abattoir.     

Agents associated with neonatal diarrhoea in Ethiopian dairy calves

Faeces samples collected from diarrhoeic dairy calves in the first 8 weeks of life were examined for the presence of 5 enteropathogens. The majority of the 108 diarrhoea cases occurred in the first 5 weeks of life and a commercial ELISA kit detected bovine enteric coronavirus (BEC) in 38.9%, serogroup A rotavirus (RV) in 16.7% and K99 (F5) fimbrial adhesin-positive Escherichia coli (K99 ETEC) in 11.1 per cent. Concurrent infections of these enteropathogens were detected in 14.8% of samples (30.8% of samples positive for these agents). No evidence of cryptosporidial infection was found using a differential staining method on faecal smears nor was salmonella excretion detected. On 2 of the 8 farms only BEC was present; the other 6 farms were positive for all 3 agents. It is concluded that BEC is the major infectious cause of neonatal calf diarrhoea in the Ethiopian dairy herds studied with RV and K99 ETEC also contributing to morbidity, either alone or as mixed infections.     

Risk factors associated with diarrhoea in newborn calves.

A prospective study was carried out on 94 randomly selected beef calf herds in the Midi-Pyrénées region in France in order to determine neonatal gastroenteritis risk factors. A total of 3,080 newborn calves was enrolled from December 1995 to April 1996. By using a specific statistical analysis method that takes into account an 'intra-herd' correlation, our final model allows the identification of approximately 20 management risk factors associated with diarrhoea. We confirmed several factors identified previously (calving conditions) and estimated some new factors (month of birth). Several herd level factors were found to be significantly associated with the risk of diarrhoea. These factors included herd management conditions such as hygiene (cleaning, relative risk (RR) = 1.9), and also vitamin or salt supplements to animals and cow vaccination (RR = 2). It was found amongst the calf level factors, that calving conditions and dyspnea were associated with diarrhoea. Dam vaccination seemed to protect calves against illness. A relationship between diarrhoea and the month of birth was also observed. Our results confirmed that calf diarrhoea is a multifactor pathology and prevention should be considered globally within the farm.     

Occurrence of enterotoxigenic Escherichia coli in calves with acute neonatal diarrhoea

Enterotoxigenic Escherichia coli (ETEC) were isolated from 16.4% of diarrheic calves of up to 30 days old. Of 1-2-day-old calves nearly one half (45.0%) harboured ETEC, while this was the case with only 4.9% of 8-day-old calves. Among 206 9-30-day-old calves just three were found to harbour ETEC.     

Rotavirus-associated diarrhoea in buffalo calves in Sri Lanka

Faecal samples from 150 buffalo calves, one to 150 days old, located in various districts of Sri Lanka, were examined for group A rotavirus antigen by a screening enzyme linked immunosorbent assay (ELISA). Positive samples were confirmed by the blocking ELISA. In the calves studied 27·3 per cent were diarrhoeic, and the rest were non-diarrhoeic but were in contact with the animals showing diarrhoea. Antigen was detected in 36·6 per cent of the diarrhoeic animals and in 11·9 per cent of the nondiarrhoeic animals. There was a strong association between the presence of antigen in faeces and diarrhoea in these animals (ξ² = 46·98; P<0·001). Of the 146 serum samples examined for antirotaviral antibodies, by the blocking ELISA at a single serum dilution (1:20) against a constant dose of antigen (8 units), 68·5 per cent were positive indicating a widespread infection with the virus in the population studied. This is the first record of the detection of rotavirus and its association with diarrhoea in buffalo calves in Sri Lanka.     

Factors associated with time to neonatal diarrhoea in French beef calves

A prospective study was carried out on 92 randomly selected beef herds in the Midi-Pyrénées region in France. The objective was to determine factors associated with time to neonatal gastroenteritis. By taking into account the “intra-herd” correlation in failure time (in the semiparametric Cox model), we identified 12 management risk factors associated with hazard of diarrhoea. Some previously have been identified, but “new” risk factors were feeding of corn silage and the incidence of diarrhoea in the last season. We used the two main approaches which are often reviewed: marginal and frailty Cox models. Our results show that these two models give different parameter estimates, so the choice of the model remains crucial.     

The prevalence and clinical relevance of hyperkalaemia in calves with neonatal diarrhoea

One hundred and twenty-four calves with neonatal diarrhoea were investigated in order to assess the prevalence of hyperkalaemia and the associated clinical signs. Hyperkalaemia (potassium concentration >5.8 mmol/L) was recognized in 42 (34%) calves and was more closely associated with dehydration than with decreases in base excess or venous blood pH. In 75 calves with normal blood concentrations of D-lactate (i.e. ?3.96 mmol/L), K concentrations were moderately correlated with base excess values (r = ?0.48, P < 0.001). In contrast, no significant correlation was observed in 49 calves with elevated D-lactate. Only three hyperkalaemic calves had bradycardia and a weak positive correlation was found between heart rate and K concentrations (r = 0.22, P = 0.014). Ten of the 124 calves had cardiac arrhythmia and of these seven had hyperkalaemia indicating that cardiac arrhythmia had a low sensitivity (17%) but a high specificity (96%) as a predictor of hyperkalaemia.In a subset of 34 calves with base excess values ??5 mmol/L and D-lactate concentrations <5 mmol/L (of which 22 had hyperkalaemia), changes in posture/ability to stand could be mainly explained by elevations of K concentrations (P < 0.001) and to a lesser extent by increases in L-lactate concentrations (P = 0.024). Skeletal muscle weakness due to hyperkalaemia alongside hypovolaemia may produce a clinical picture that is similar to that in calves with marked D-lactic acidosis. However, since reductions in the strength of the palpebral reflex are closely correlated with D-lactate concentrations, a prompt palpebral reflex can assist the clinical prediction of hyperkalaemia in calves presenting with a distinct impairment in their ability to stand (specificity 99%, sensitivity 29%).     

Antimicrobial susceptibility of Salmonella isolates recovered from calves with diarrhoea in Australia

OBJECTIVE To identify the common serotypes and antimicrobial resistance patterns of Salmonella spp. associated with diarrhoea in Australian dairy calves under the age of 6 weeks. DESIGN Cross-sectional study. METHODS Faecal samples were collected from outbreaks of diarrhoea in dairy and dairy beef calves less than 6 weeks old. Samples were screened for Salmonella using standard enrichment culture techniques. The antimicrobial susceptibility to 12 commonly used veterinary and human antimicrobials was assessed using the Kirby-Bauer disk diffusion method and the susceptibility profiles of dairy and dairy beef properties were compared using Fisher's exact test. RESULTS Salmonella ser. Dublin, S. ser. Typhimurium and S. ser. Bovismorbificans were the three most common salmonella serotypes isolated. The majority of properties had one serotype. Most of the Salmonella isolates were not resistant to any of the antimicrobials tested. No resistance was seen to amikacin and nalidixic acid, and only one isolate was resistant to ceftiofur or amoxicillin-clavulanic acid. The most common antimicrobial resistance was to streptomycin, ampicillin or combination sulfonamides. Multi-drug resistance was detected in S. ser. Anatum, S. ser. Bovismorbificans, S. ser. Muenster, S. ser. Newport and S. ser. Typhimurium. Isolates from dairy beef properties were more likely to be resistant to ampicillin, kanamycin, neomycin, sulfamethoxazole/trimethoprim and tetracycline (P < 0.05) and were more likely to exhibit multi-drug resistance. CONCLUSION The prevalence of antimicrobial resistance in Salmonella isolates from dairy calves in Australia is low compared with that reported overseas. From a human health perspective, resistance to antimicrobials used in the treatment of human salmonellosis was infrequent.     

Pathology and residues in veal calves treated experimentally with clenbuterol

Six veal calves were medicated with clenbuterol at 20 μg kg bodyweight⁻¹ day⁻¹ for 42 days before they were slaughtered, to evaluate the lesions and residues in target organs. Compared with six unmedicated calves the most noticeable changes were tracheal dilatation, decreased uterine weight, slight mucous hypersecretion in the uterus and vagina and depletion of liver glycogen. The highest concentrations of clenbuterol (62 to 128 ng/g⁻¹) were recorded in the choroid/retina, and the aqueous humour had the lowest concentration (0·5 to 2·4 ng ml⁻¹). The residue concentrations were higher than the maximum residue level set for clenbuterol (0·5 ng g⁻¹)     

Pattern of diarrhoea in newborn beef calves in south-west France

A prospective study was carried out on 94 randomly selected beef herds in the Midi-Pyrénées region in France. The objective was to describe diarrhoea and mortality in beef calves from birth to 30 days of age. Calves (3,080) were followed from December 1995 to April 1996, and a total of 700 visits allowed records of herd management practices, individual data and environmental conditions to be collected. The incidence rate for diarrhoea during the neonatal period was 14.6%, and varied markedly between herds. Eighteen herds did not suffer from diarrhoea, while five herds had an incidence of more than 50%. Results indicate that 52% of diarrhoea appears during the first week and only 15% after the second week of life. The greatest risk of diarrhoea for a calf was during the first and second weeks of life (7.9 and 6.5 times, respectively). The month of birth was also significantly associated with morbidity, the highest incidence was observed in December and March (17.6 and 23.6%, respectively). Escherichia coli was isolated from 20.3% of faecal samples and appeared earlier during the first days of life. Rotavirus was frequently isolated (47.4%) from samples. Coronavirus was positive for only 16.5% but was significantly associated with diarrhoea. Cryptosporidium was less frequent (15.6%). The global mortality rate was 3.6% and was two-times higher in December than in other months. Forty per cent of herds did not exhibit mortality, and 10% had mortality rates greater than 10%. This study confirms previously reported data, and with greater precision and details on diarrhoea and mortality incidences among herds, age and month of birth in suckling beef calves.