Apparatus for pasteurising teat cup liners between cows in a herringbone parlour.

In a herringbone milking parlour, teat cup liners were deliberately contaminated in turn with Staphylococcus aureus, Escherichia coli, Streptococcus agalactiae and Sterp uberis. Contamination was achieved by filling the liners with milk that contained 10(6) test organisms per ml. After the clusters had been back-flushed with water at 85 degrees C for five seconds, normal swabbing methods failed to recover any contaminating organisms from the teat liners in 56 tests out of 64. After 10 seconds back-flushing no recoveries were made in the same number of tests. The apparatus developed to effect this back-flushing for a particular herringbone parlour is described, with details of its routine use during milking. For a 100-cow herd, the running cost of such equipment using a five-second back-flush is estimated at no more than 4 pounds per week and, in its present form, would not add more than 10 seconds to the total milking time for each cow. Improvements in design of the apparatus, and in milking techniques arising from the routine use of the device, are also considered.     

Serum resistance and virulence of Escherichia coli isolated from turkeys

Twenty-five strains of Escherichia coli isolated from turkeys were characterized for their serum resistance and virulence. An in vitro bactericidal assay was used to determine the serum resistance of E coli. Virulence was determined by survival time after IV inoculation of each strain into 3-week-old turkeys. Serum-resistant E coli strains were generally found to be virulent for turkeys, whereas serum-sensitive E coli strains were avirulent. Of the 25 strains, 18 strains were placed in the 2 categories of serum-resistant/virulent and serum-sensitive/avirulent. Five strains were serum-resistant and avirulent, and 2 strains were serum-sensitive and virulent. Serum resistance appears to be an important determinant of virulence for E coli in turkeys; however, the requirement for other virulence factors, in addition to serum resistance, was suggested by the finding that 5 serum-resistant strains were avirulent in turkeys.     

Prevalence and age-related variation of Cryptosporidium species and genotypes in dairy calves

Fifteen dairy farms in seven states on the east coast of the US were each visited on two consecutive years to determinate the prevalence of Cryptosporidium species in pre-weaned (5 days to 2 months) and post-weaned calves (3-11 months), respectively. After each of 971 fecal specimens collected directly from each calf was sieved and subjected to density gradient centrifugation to remove debris and concentrate oocysts, specimens were examined by immunofluorescence microscopy, and polymerase chain reaction (PCR). For all PCR-positive specimens the 18S rRNA gene of Cryptosporidium was sequenced. Cryptosporidium was identified from all farms. Types of housing appeared to have no influence with regard to prevalence of infection. Of 971 calves, 345 were infected with Cryptosporidium (35.5%), but more pre-weaned calves (253 of 503; 50.3%) than post-weaned calves (92 of 468; 19.7%) were found to be infected. A total of 278 PCR-positive specimens characterized by gene sequencing revealed Cryptosporidium parvum, Cryptosporidium andersoni, and two unnamed Cryptosporidium genotypes Bovine B (AY120911) and deer-like genotype (AY120910). The prevalence of these Cryptosporidium species and genotypes appeared to be age related between pre- and post-weaned calves. C. parvum, the only zoonotic species/genotype, constituted 85% of the Cryptosporidium infections in pre-weaned calves but only 1% of the Cryptosporidium infections in post-weaned calves. These findings clearly demonstrate that earlier reports on the presence and prevalence of C. parvum in post-weaned cattle that were based solely on oocyst morphology must be reassessed using molecular methods to validate species and genotype. This finding also indicates that persons handling or otherwise exposed to calves under 2 months of age are at greater risk of zoonotic infection from Cryptosporidium than the risk of infection from exposure to older calves.     

Prevalence of Giardia duodenalis genotypes in pre-weaned dairy calves

To determine the prevalence of Giardia genotypes in pre-weaned dairy calves, fecal samples were collected from a minimum of 18, 1-7-week-old dairy calves per farm on two farms each in the states of Vermont, New York, Pennsylvania, Maryland, Virginia, North Carolina, and Florida. Samples cleaned of fecal debris and concentrated using CsCl density gradient centrifugation were stained and examined by immunofluorescence microscopy and also subjected to PCR and gene sequence analysis. Prevalence by PCR ranged from 9% on a farm in Pennsylvania to 93% on a farm in Vermont, with an average prevalence for 407 calves on 14 farms of 40%. Gene sequence analysis of the TPI, beta-giardin and 16S rRNA genes revealed 85% of the positive samples to be Assemblage E, while 15% were Assemblage A, although the percentages of these genotypes varied greatly from farm to farm. Some farms had no Assemblage A Giardia. Thus, while a majority of the calves were infected with a genotype that is not known to be infectious for humans, calves on 7 of 14 farms did harbor Assemblage A Giardia. Calves should be considered as a potential source of human infectious cysts in the environment.     

Quantification of Mannheimia haemolytica leukotoxin by indirect ELISA

An indirect enzyme-linked immunosorbent assay (ELISA) was developed for the quantification of extracellular leukotoxin (LKT) produced in chemostat culture of Mannheimia haemolytica in a serum-free culture medium. Leukotoxin purified with preparative SDS-PAGE was used for the production of chicken polyclonal antibodies (PAb) that served as the primary detecting antibody. Excising the LKT protein from an analytical SDS-PAGE gel proved an efficient technique for the purification of the toxin. Consequently, the 102 kDa LKT polypeptide purified in this manner served as reference toxin and the resulting calibration curve was modelled using a four parameter logistic fit to relate absorbance to LKT protein concentration. The lower detection limit corresponded to an LKT concentration of 14.5 ng ml(-1). The presence of SDS, serum albumin and the coating pH had a distinct effect on the absorbance values of the indirect ELISA.     

Age-dependent seroprevalence of antibodies against a Helicobacter pylori-like organism and Helicobacter pylori in commercially reared swine

OBJECTIVE: To determine the prevalence of antibodies against a swine-origin Helicobacter pylori-like organism (HPLO) and H pylori in conventionally reared swine. ANIMALS: 640 conventionally reared swine of various ages from 16 high-health farms in Canada, 20 sows from Ohio, and 35 gnotobiotic swine. PROCEDURES: Blood was collected from the cranial vena cava. Sera were collected and tested via ELISA for antibodies against antigen prepared from a swine-origin HPLO and human H pylori strain 26695. RESULTS: Antibodies reactive with a swine HPLO, H pylori, or both were detected in 483 of 640 swine from all 16 farms in western Canada. Seroprevalence varied with age and was low (5.6%) in suckling ( 4 weeks old to adulthood. CONCLUSIONS AND CLINICAL RELEVANCE: Findings suggested that colonization by a swine-origin HPLO, H pylori, or both and resultant seroconversion, like that of H pylori infection in humans, were common in commercial swine operations. Furthermore, data indicated that gastric infection was acquired at an early age. The relationships to gastric colonization by HPLOs and clinical manifestations of disease such as gastritis and gastroesophageal ulceration remain to be determined.     

In this issue – June 2012

Assay to measure success of functional parathyroid excision · Palliative radiation therapy for malignant trichoepithelioma · Idiopathic haemarthrosis in horses · Fatal snail bait poisoning in a horse · Utility of diagnostic tests for Actinobacillus pleuropneumonia in pigs · Iodine deficiency disorders in sheep · Immobilisation of estuarine crocodiles     

THANKS TO REVIEWERS

Maximal movement initiation in Greyhounds · Novel chemotherapy protocol for osteosarcoma · Low‐field MRI for equine foot conditions · Periorbital wooden foreign body · Effect of plastic clips in sheep · Comparison of diagnostic tests for Lawsonia in pigs · Student vs employer expectations     

Serological and clinical surveillance studies to validate reported foot-and-mouth disease free status in Tsirang district of Bhutan

Serological and clinical studies were conducted between March 2009 and August 2010 to validate the foot-and-mouth disease free status of Tsirang district of Bhutan as determined by the country's passive surveillance system. Randomised (first survey) and targeted (third survey) samplings, with subsequent follow-up samplings (second and fourth), were conducted on FMD-susceptible animals to detect the disease at a design prevalence of 25% and 20% at the individual animal-level and village-level, respectively. Sera from cattle, goats, pigs, and sheep were tested for the presence of non-structural protein (NSP) antibodies using two commercial (PrioCHECK(?) FMDV NS and CHEKIT(?)-FMD-3ABC-bo-ov) and one in-house NSP kit (c-ELISA, AAHL, Australia). The overall seropositivity (all species) at the animal-level was 3% (95% CI: 1.7, 4.8) and 3.5% (95% CI: 2.1, 5.4), for the randomised and targeted surveys, respectively. Except for one goat from the first survey, none of the small ruminants and pigs had NSP antibodies. The seropositives from the first and targeted surveys were distributed among 13 and 16 of 20 villages sampled, respectively. All repeat testing from the initial seropositive animals and their herd mates, for both the first and third surveys, were negative in the NSP tests 6-8 months later. Using the hypergeometric exact probability formula for two-stage analyses, the results enabled rejection of the null hypothesis and supported conclusion that the population was free from disease at the minimum expected prevalence of 20% at the 95.53% and 99.46% confidence levels, for the randomised and targeted surveys, respectively. Clinical surveillance also showed absence of disease or clinical signs suggestive of FMD. The few seropositives were likely to be false positives due to factors such as imperfect specificities of the tests and possible NSP-residues in the vaccines. The study has paved the way for initiation of zoning approaches for the progressive control of FMD in Bhutan.