Manageable risk factors associated with the lactational incidence, elimination, and prevalence of Staphylococcus aureus intramammary infections in dairy cows

Abstract

Staphylococcus aureus intramammary infections (IMI) are a major cause of mastitis on farms worldwide. Incidence and elimination rates are the key determinants of prevalence of Staph. aureus, and risk factors associated with these rates must be identified, prioritized, and controlled to obtain long-term reduction in prevalence. The objectives of this study were to identify manageable risk factors associated with the lactational incidence, elimination, and prevalence of Staph. aureus IMI. A cohort of 90 Canadian dairy farms was recruited and followed in 2007 and 2008. Quarter milk samples were collected repeatedly from a selection of cows, and bacteriological culture was realized to assess incidence, elimination, and prevalence of Staph. aureus IMI. Practices used on farms were measured using direct observations and a validated questionnaire. A linear regression model was used to explore the relationship between herd IMI prevalence and incidence and elimination rates. Multilevel logistic regression models were used to compute measures of associations between practices used on farms and IMI incidence, elimination, and prevalence. The herd incidence rate was the most important predictor of herd IMI prevalence: a reduction of the incidence rate equivalent to its interquartile range (0.011 new IMI/quarter-month) was associated with a prevalence reduction of 2.2 percentage points; in comparison, an equivalent increase of the elimination rate by its interquartile range (0.36 eliminated IMI/quarter-month) resulted in a prevalence reduction of 0.4 percentage points. Postmilking teat disinfection and blanket dry-cow therapy were already implemented by most herds. Most of the practices associated with Staph. aureus IMI incidence were related to milking procedures. Among these, wearing gloves during milking showed desirable associations with IMI incidence, elimination, and prevalence. Similarly, adequate teat-end condition and use of premilking teat disinfection were associated with lower IMI incidence and prevalence. The initial herd prevalence of Staph. aureus IMI was positively associated with subsequent IMI incidence. This indicates that, in some situations, an initial reduction of the pool of infected quarters could be justified. Some housing practices were associated with IMI incidence, elimination, or prevalence. The effects of these latter practices, however, were often influenced by specific cow characteristics such as parity or days in milk. These results highlight the importance of good milking practices to prevent Staph. aureus IMI acquisition and, therefore, reduce their prevalence.

Effect of microbial sanitizers for reducing biofilm formation of Staphylococcus aureus and Pseudomonas aeruginosa on stainless steel by cultivation with UHT milk

“…This bacterium causes bovine mastitis and one of the most cost intensive diseases in the dairy industry (Dufour et al, 2012). In addition, enterotoxigenic S. aureus strain contains the potentially to make food borne intoxications in human transmitted by consuming the contaminated dairy products (Hennekinne et al, 2012;Jørgensen et al, 2005;Ostyn et al, 2010;Schmid et al, 2009).…”

Update on Control of Staphylococcus aureus and Streptococcus agalactiae for Management of Mastitis

“…When gloves were worn, the odds ratio for new S aureus IMI incidence was 0.43 and the odds of eliminating existing infection was 2.2 times higher for herds where milkers wore gloves. 43 In a separate study, wearing gloves was also found to have a positive net economic benefit. 51 When friction is lost between the teat skin and the milking unit inflation, liner slips can occur, which allow air to be admitted in an uncontrolled fashion into the milking unit.…”

“…A recent Canadian study found that it was also associated with a lower risk for prevalence and incidence of S aureus. 43 NMC annually publishes a list of approved premilking and postmilking teat disinfectant products. 44 For a premilking teat disinfection protocol to be most effective, it must have good coverage on the teat and be in contact with the teat skin for 30 seconds.…”

Scientific Opinion on the assessment of dairy cow welfare in small‐scale farming systems

“…The association between housing system and housing characteristics (bedding, stall base, stall length) and intramammary infection with Staphylococcus aureus differed for cows in different parities in the same herds. Similarly, the association of stocking density with elimination of infection depended on days in milk (Dufour et al, 2012). In Switzerland, lower herd SCC was described in organic farms with Alpine summer pasturing, while there was no effect of housing (except soft bedding) (Ivemeyer et al, 2009).…”