Transmission dynamics of intramammary infections caused by Corynebacterium species

Abstract

The development of reliable models for transmission of intramammary infections (IMI) is the subject of extensive research. Such models are useful to enhance the identification and understanding of factors that affect pathogen-specific IMI dynamics. Longitudinal transmission models are valuable for predicting infection outbreak risks, quantifying the effectiveness of response tactics, and performing response planning. In this work, we focused on modeling Corynebacterium spp. by using a compartmental model. Previous investigations have considered modeling the transmission dynamics of several bacterial pathogens, but not Corynebacterium spp. We established a Corynebacterium spp. Susceptible-Infectious-Susceptible (SIS) model. We simulated the model numerically by using parameters that we estimated by a generalized linear model approach, using month of study as the time variable. The data, from which the parameters of the model were estimated, were obtained in a field trial conducted in 2 US dairy herds. Altogether, 786 cows were sampled at least once during the 13-mo study period. The total number of quarter milk cultures and cases of IMI caused by Corynebacterium spp. were 11,744 and 556, respectively, in farm A; the corresponding figures for farm B were 11,804 and 179. Our modeling study included only transmission from persistent IMI caused by Corynebacterium spp. within the lactation pens. The rate of new infections was significantly related to preexisting IMI in both farms, underscoring the importance of preexisting Corynebacterium spp. IMI for the transmission of Corynebacterium spp. within lactation pens. The estimated basic reproduction numbers (R) in the 2 farms were 1.18 and 0.98, respectively. The nonsignificant disparity in R was associated with significant differences in cure rates between farms.

Milk microbial composition of Brazilian dairy cows entering the dry period and genomic comparison between Staphylococcus aureus strains susceptible to the bacteriophage vB_SauM-UFV_DC4

“…has been frequently isolated from subclinical mastitis, our study highlights a positive correlation between this genus and clinical mastitis records. Using a longitudinal transmission model, Rachah et al 69 demonstrated an increase of new IMI caused by previous udder infections determined by Corynebacterium spp., which might explain the outbreaks of clinical mastitis.…”

Dynamics of somatic cell count patterns as a proxy for transmission of mastitis pathogens

“…The basic reproduction number R 0 is a combined value affected by the number of contacts per unit time, transmission probability per contact, and duration of the infectious period (Anderson and May, 1991). Dalen et al (2018) found that the cure rate for subclinical IMI differed significantly between 2 farms with the same mastitis pathogen, and that this difference affected the prediction of transmission dynamics of the same pathogen in each farm. With herd-specific knowledge of which transmission parameters have most effect on transmission dynamics, we can improve udder health management by focusing preventive actions on those management areas that are related to the transmission parameters of concern for each specific herd.…”

Transmission Dynamics of Corynebacterium spp. Within Two Danish Dairy Cattle Herds

“…Poisson regression is a commonly applied method for estimating transmission rates in both epidemic and endemic scenarios ( 8 , 19 ). We here wanted to assess and compare the transmission rates of Corynebacterium spp.…”

“…We used the term log( S int · I int / N int ) as an offset in the regression analysis, meaning that this model reflects contagious transmission directly between cows. Like in Dalen et al ( 8 ), we also constructed a similar model with log( S int ) as the offset, they mimic a fixed rate of infection, independent of the proportion of infected animals present at the sampling points. This model reflects environmental transmission where pathogens come from a reservoir in the environment.…”

“…To our knowledge, only one study has described the transmission dynamics of IMI caused by Corynebacterium spp. in U.S. dairy cows ( 8 ). To investigate the variance in the transmission dynamics of Corynebacterium and be able to include it in decision support tools, it is essential to obtain estimates of the transmission dynamics from more herds and other geographical regions.…”