Review: Livestock disease resilience: from individual to herd level

Abstract

Infectious diseases are a major threat to the sustainable production of high-producing animals. Control efforts, such as vaccination or breeding approaches often target improvements to individual resilience to infections, i.e., they strengthen an animal’s ability to cope with infection, rather than preventing infection per se . There is increasing evidence for the contribution of non-clinical carriers (animals that become infected and are infectious but do not develop clinical signs) to the overall health and production of livestock populations for a wide range of infectious diseases. Therefore, we strongly advocate a shift of focus from increasing the disease resilience of individual animals to herd disease resilience as the appropriate target for sustainable disease control in livestock. Herd disease resilience not only captures the direct effects of vaccination or host genetics on the health and production performance of individuals but also the indirect effects on the environmental pathogen load that herd members are exposed to. For diseases primarily caused by infectious pathogens shed by herd members, these indirect effects on herd resilience are mediated both by individual susceptibility to infection and by characteristics (magnitude of infectiousness, duration of infectious period) that influence pathogen shedding from infected individuals. We review what is currently known about how vaccination and selective breeding affect herd disease resilience and its underlying components, and outline the changes required for improvement. To this purpose, we also seek to clarify and harmonise the terminology used in the different animal science disciplines to facilitate future collaborative approaches to infectious disease control in livestock.

A biological integrity framework for describing animal welfare and wellbeing

“…The discussion has focused on welfare and wellbeing of the individual, yet it is well-recognized that attributes assessed at the level of the group are influenced by the current characteristics of individuals such as their disease status (Doeschl-Wilson et al 2021) as well as by heritable characteristics of the individual through indirect genetic effects (Bergsma et al 2008;Camerlink et al 2018). Individuals can both enhance and diminish the wellbeing of others in a group, and optimizing the wellbeing of the individual and the group may not be mutually attainable goals (Fraser 2003;Hemsworth et al 2015), Thus, there is a need for concepts and their explanatory frameworks to include descriptions of welfare and wellbeing at both the group and individual level.…”

“…If appropriate metrics of social connectedness can be developed, they may capture some of the wellbeing attributes of the group. Health dynamics can also differ between the group and the individual and need inclusion within a more comprehensive framework (Knap and Doeschl-Wilson 2020;Doeschl-Wilson et al 2021).…”

Bringing livestock back into the fold: Animal research in the Annals of Applied Biology—Past, present and future

“…Animal genetics, or “constitution” to adapt Hammond's concept (Hammond, 1945), are also important in the context of production efficiency, disease and animal welfare. The feasibility of selectively breeding livestock and fish for host resistance to disease, and therefore reduced susceptibility, is showing exciting potential (e.g., Tsairidou, Anacleto, Woolliams, & Doeschl‐Wilson, 2019), but there is room for expansion of this field into new areas focussing at the population level and aiming to solve problems which require holistic solutions (Doeschl‐Wilson, Knap, Opriessnig, & More, 2021; Rosendal & Olesen, 2022).…”

Optimal experimental designs for estimating genetic and non-genetic effects underlying infectious disease transmission

“…Yet, remarkably little is known about the role of previously identified ‘resistance’ loci in infectious disease transmission, because in most studies, disease resistance refers to the resistance of an infected animal to develop disease or other side-effects from infection (e.g. performance reduction or death), rather than to resistance to becoming infected or transmitting the infection [ 8 – 10 ]. Hence, it is not known whether selection for disease resistance actually reduces disease prevalence, since animals that carry the beneficial resistance alleles may still become infected and transmit the infection.…”