# Are Visitor and Personnel Downtime Restrictions an Effective Biosecurity Measure to Prevent the Indirect Transmission of Pathogens to Livestock?

## TL;DR

This paper reviews whether downtime restrictions help prevent livestock disease spread and finds they offer no proven benefit beyond basic hygiene measures.

## Contribution

The study is the first to systematically evaluate the scientific evidence for downtime as a biosecurity measure in livestock disease prevention.

## Key findings

- No evidence supports downtime as more effective than basic hygiene measures like handwashing and changing clothes.
- Only one study found possible pathogen transmission to new animals after nasal carriage in humans.
- Current guidelines recommending downtime lack strong scientific backing.

## Abstract

Downtime is a period of 24–72 h during which people who have made contact with one animal species avoid contact with other animals to prevent disease spread. This review evaluated the effectiveness of downtime and found no evidence that downtime provides protection beyond established measures like hand hygiene, changing clothes and boots and showering. Some studies show that humans may carry pathogens in their nasal cavities after contact with infected animals, but only one study indicated possible transmission to other animals under experimental conditions. These findings are limited by the small number of studies, which are primarily pig-focussed and have methodological challenges such as small sample sizes. This review highlights a gap between current biosecurity guidelines recommending downtime and the lack of supporting evidence. While downtime may deter unnecessary farm visitors, it provides no proven benefit over established hygiene measures and may create a false sense of security, leaving animal populations vulnerable. Resources and policy should therefore focus on implementing and verifying core hygiene measures rather than enforcing downtime.

Downtime, also known as an animal avoidance period, refers to a 24–72 h period during which individuals who have had contact with one animal species avoid subsequent contact with other susceptible species. This scoping review critically evaluated the effectiveness of downtime as a biosecurity measure. Peer-reviewed studies were identified and analysed using three electronic databases (Pubmed, Web of Science and Scopus). Two experimental studies directly evaluated downtime, nine additional articles examined human nasal carriage of pathogens after exposure to infected animals and seven articles evaluated the effectiveness of hygiene-based biosecurity measures targeting indirect mechanical pathogen transmission via humans (n = 14 unique articles in total; topical overlap noted where studies contributed to multiple categories). No evidence indicated an added benefit of downtime over other, more evidence-based measures such as hand hygiene, changing of clothes and boots and showering. While certain studies were able to identify the nasal carriage of pathogens, only one study indicated possible consequent transmission to naïve animals. This limited and species-specific evidence base reveals a critical gap between policy recommendations and scientific support for downtime. Based on these results, no clear benefit or necessity of downtime over other measures have been identified, other than its ability to deter unnecessary visitors, but these do not outweigh the impracticalities associated with an ‘animal avoidance period’. Resources and policy efforts should therefore shift from enforcing downtime toward ensuring and verifying adherence to fundamental hygiene measures.