Investigation of On-Farm Transmission Routes for Contamination of Dairy Cows with Top 7 Escherichia coli O-Serogroups.

Shiga toxin-producing Escherichia coli (STEC) are foodborne bacterial pathogens, with cattle a significant reservoir for human infection. This study evaluated environmental reservoirs, intermediate hosts and key pathways that could drive the presence of Top 7 STEC (O157:H7, O26, O45, O103, O111, O121 and O145) on pasture-based dairy herds, using molecular and culture-based methods. A total of 235 composite environmental samples (including soil, bedding, pasture, stock drinking water, bird droppings and flies and faecal samples of dairy animals) were collected from two dairy farms, with four sampling events on each farm. Molecular detection revealed O26, O45, O103 and O121 as the most common O-serogroups, with the greatest occurrence in dairy animal faeces (> 91%), environments freshly contaminated with faeces (> 73%) and birds and flies (> 71%). STEC (79 isolates) were a minor population within the target O-serogroups in all sample types but were widespread in the farm environment in the summer samplings. Phylogenetic analysis of whole genome sequence data targeting single nucleotide polymorphisms revealed the presence of several clonal strains on a farm; a single STEC clonal strain could be found in several sample types concurrently, indicating the existence of more than one possible route for transmission to dairy animals and a high rate of transmission of STEC between dairy animals and wildlife. Overall, the findings improved the understanding of the ecology of the Top 7 STEC in open farm environments, which is required to develop on-farm intervention strategies controlling these zoonoses.

Effects of 3 surface types on dairy cattle behavior, preference, and hygiene.

Muddy surfaces have negative effects on the health and welfare of dairy cattle, and if possible, cows will avoid this surface. However, it is unclear whether it is the moisture content or the contamination with manure that is aversive to the cows. This study aimed to assess the use and preference for different wood chip (0.4 m deep) surface types: (1) clean and dry (clean, dry matter content, DM: 44 ± 2.8%), (2) dirty (dirty, contaminated with manure, DM: 40 ± 3.7%), and (3) clean and wet (wet, wetted by water, DM: 23 ± 3.3%). Eighteen nonlactating, pregnant cows were tested individually (mean 24-h temperature: 9.9 ± 4.46°C, mean ± standard deviation for all preceding values). Cows were kept indoors in test pens for 18 h on wood chip without feed and 6 h on pasture to allow for daily feed intake. To ensure cows made informed choices and to measure changes in behavior and hygiene associated with each option, they were first exposed to each surface for 5 d (n = 12 cows per surface type when they were restricted on one surface; i.e., each cow was exposed to 2 treatment surfaces only). Cows on the wet surface spent the least amount of time lying when restricted to one surface for 18 h (wet: 21%, dirty: 57%, clean: 64%) and spent more time lying when on pasture for 6 h (wet: 13%, dirty: 4%, clean: 3%). The total lying times during the 5-d surface exposure were wet: 4.6 ± 1.04 h, dirty: 10.6 ± 0.25 h, and clean: 11.7 ± 0.25 h per 24 h. Cows restricted on the wet surface for 18 h had fewer bouts (no.) of lateral lying (wet: 0.9 ± 1.36, dirty: 6.3 ± 1.36, clean: 8.4 ± 1.38), spent less time lying with their heads supported (wet: 18.9 ± 7.17 min, dirty: 36.7 ± 7.17 min, clean: 39.1 ± 7.26 min), and spent less time with the front legs tucked (wet: 16 ± 4.3%, dirty: 41 ± 4.3%, clean: 50 ± 4.3% of time spent lying, mean ± standard error of the mean for all preceding values), than cows on the other surfaces. Cows on the dirty surface were less clean compared with the other treatment groups (0.6 of a score on a 5-point scale; standard error of the differences of means: 0.11 for both comparisons). They were then given a free choice between 2 known surfaces for 2 consecutive days (n = 6 per pairwise choice). Cows ranked the surfaces as clean > dirty > wet. In summary, there is compelling evidence that wet surfaces impair the welfare of dairy cattle by affecting the quantity and quality of rest. Rebound responses indicate that the motivation to rest is not fulfilled on wet surfaces. Finally, when given a choice, they show clearly that they will avoid wet and dirty surfaces. The combined results indicate that changes in affective state likely underlie these behavioral responses.

Prevalence of Shiga toxin-producing Escherichia coli in pasture-based dairy herds.

Shiga toxin-producing Escherichia coli strains (STEC) are food-borne pathogens. While E. coli O157:H7 is commonly associated with cattle, less is known about the prevalence of non-O157 STEC serogroups in bovines. This study evaluated the prevalence and virulence status of O157:H7 and six E. coli O-serogroups (O26, O103, O45, O145, O121, O111) in New Zealand dairy farms using molecular as well as culture-based methods. Fresh farm dairy effluent (FDE) (n = 36) and composite calf faeces (n = 12) were collected over three samplings from 12 dairy farms. All seven target serogroups were detected through molecular techniques. Of the 202 isolates which were serologically confirmed following traditional culturing and immunomagnetic separation (IMS), O103, O26, O45 and O121 were the most common serogroups, being found in 81, 47, 42 and 32% of the FDE and in 17, 33, 25 and 9% of the calf faeces respectively. The majority (157/202) of the isolates were negative for stx and eae virulence genes. The prevalence of the seven target STEC was low, and only nine O26 isolates (4%) were recovered from four of the farms. The study has highlighted the need for improving the isolation of Top 7 STEC from the stx-negative populations present in fresh dairy effluent and calf faeces. SIGNIFICANCE AND IMPACT OF THE STUDY: Shiga toxin-producing Escherichia coli (STEC) are important food-borne pathogens that can cause severe illness in humans. Cattle are asymptomatic reservoirs for STEC, and transmission to humans can be by consumption of food products or water contaminated with cattle faeces. Our study investigated the prevalence of O157:H7 and six E. coli serogroups of STEC (O26, O103, O45, O145, O121, O111) over time in the dairy reservoir and increases the knowledge and understanding of these pathogens on pasture-based farms. Such information is required to develop risk-assessment models aiming at limiting transmission of these STEC to human.

Pain sensitivity and injury associated with three methods of disbudding goat kids: Cautery, cryosurgical and caustic paste.

Pain sensitivity and skull/brain injury associated with cautery, cryosurgical and caustic paste disbudding were evaluated in goat kids. Kids (reared for meat; n=280) were randomly assigned to one of four treatments (n=70 per treatment): (1) sham-handling (SHAM) or (2) cautery (CAUT), (3) cryosurgical (CRYO) or (4) caustic paste (CASP) disbudding. A pain sensitivity test was carried out 15min pre-treatment and 1h post-treatment. Skull/brain injury was assessed at post-mortem examination. Kids with evidence of injury to the skull/brain, as well as a random sample of kids (n=15 per treatment) without evidence of skull/brain injury, were selected for histological examination of brain tissue. Average daily gains (ADG) were calculated from body weight measurements taken 10min pre-treatment and then at 2, 7 and 14days post-treatment as a measure of the potential effects of pain or injury on growth. CASP and CRYO kids displayed higher pain sensitivity post-treatment than CAUT or SHAM kids, suggesting that they experienced more acute pain 1h post-treatment. One of 70 CAUT kids had a perforated skull, but there was no histological evidence of brain injury in this animal; a further nine CAUT kids exhibited hyperaemia of the skull. The other treatments did not result in injury to the skull/brain. There was no evidence of a difference in ADG across treatments. Caustic paste and cryosurgical disbudding resulted in greater acute pain sensitivity than cautery disbudding; however, cautery disbudding has the potential to cause skull injury if performed incorrectly.

Evaluation of microsatellites as a potential tool for product tracing of ground beef mixtures.

Microsatellite genotyping was evaluated as a potential tool for DNA-based tracing of ground beef product. DNA from mixtures containing different numbers of individuals was analysed with a set of cattle microsatellite markers frequently used for parentage testing. As samples contained DNA from several animals, the microsatellite markers showed multiple peaks. The method could distinguish between mixtures containing equal amounts of meat from three different individuals, meat from three individuals mixed in different proportions, ground beef mixtures purchased in different cities, and different batches of ground beef patties. Limitations occurred when batches contained large numbers of individuals (>10) and different batches used meat from the same individuals. We conclude that DNA microsatellites may be useful for DNA traceability of ground beef mixtures prepared from less than 10 individuals, but where larger numbers of animals contribute to a mixture the method is not consistently accurate.