Elsevier

Epidemics

Volume 23, June 2018, Pages 76-84
Epidemics

Digital Dermatitis in dairy cattle: The contribution of different disease classes to transmission

https://doi.org/10.1016/j.epidem.2017.12.007Get rights and content
Under a Creative Commons license
open access

Highlights

  • Class M4 lesions have a high occurrence and a long duration.

  • Class M4 contributes over 88% to the basic reproduction ratio.

  • To stop transmission of Digital Dermatitis focus should be on prevention of class M4 lesions.

Abstract

Digital Dermatitis (DD) is a claw disease mainly affecting the hind feet of dairy cattle. Digital Dermatitis is an infectious disease, transmitted via the environment, where the infectious “agent” is a combination of bacteria. The standardized classification for DD lesions developed by Döpfer et al. (1997) and extended by Berry et al. (2012) has six distinct classes: healthy (M0), an active granulomatous area of 0–2 cm (M1), an ulcerative lesion of >2 cm (M2), an ulcerative lesion covered by a scab (M3), alteration of the skin (M4), and a combination of M4 and M1 (M4.1).

We hypothesize that classes M1, M2, M3, M4, and M4.1 are the potentially infectious classes that can contribute to the basic reproduction ratio (R0), the average number of new infections caused by a typical infected individual. Here, we determine differences in infectivity between the classes, the sojourn time in each of the classes, and the contribution of each class to R0.

The analysis is based on data from twelve farms in the Netherlands that were visited every two weeks, eleven times.

We found that 93.89% of the transitions from M0 was observed as a transition to class M4, and feet with another class-at-infection rapidly transitioned to class M4. As a consequence, about 70% of the infectious time was spent in class M4. Transmission rate parameters of class-at-infection M1, M2, M3, and M4 were not significantly different from each other, but differed from class-at-infection M4.1. However, due to the relative large amount of time spend in class M4, regardless of the class-at-infection, R0 was almost completely determined by this class. The R0 was 2.36, to which class-at-infection M4 alone contributed 88.5%.

Thus, M4 lesions should be prevented to lower R0 to a value below one, while painful M2 lesions should be prevented for animal welfare reasons.

Keywords

Mortellaro
Hairy heel wrat
Infectivity
Cow
Infection
Basic reproduction ratio

Cited by (0)