Environmental DNA: A promising factor for tuberculosis risk assessment in multi-host settings

Area of Science:

• Veterinary Epidemiology
• Wildlife Disease Ecology
• Bacteriology

Background:

• Maintaining Official Tuberculosis Free status is challenging due to Mycobacterium tuberculosis complex (MTC) circulation in domestic and wild hosts.
• Tuberculosis (TB) hotspots in cattle occur in low-prevalence regions, necessitating in-depth epidemiological investigation.
• Understanding multi-host MTC transmission is crucial for effective disease control strategies.

Purpose of the Study:

• To conduct an epidemiological diagnosis of a TB hotspot in cattle.
• To estimate host population size and MTC prevalence in livestock and wildlife.
• To evaluate on-cattle environmental DNA detection as a proxy for MTC exposure risk at the farm level.

Main Methods:

• Conducted TB skin testing in cattle and MTC testing in sheep and goats.
• Assessed MTC prevalence in wild boar and badgers through culture.
• Utilized on-cattle environmental DNA detection and farm-level risk criteria (TB testing, environmental DNA) to categorize cattle farms.

Main Results:

• 16 of 24 cattle farms had positive skin test reactors between 2012-2016.
• MTC was confirmed in four sheep, indicating an unknown infection prevalence in this species.
• Wild boar showed an 8.8% MTC prevalence, and one badger tested positive; environmental MTC DNA detection correlated with pasture use and woodland proximity.

Conclusions:

• On-animal environmental DNA sampling can aid in assessing MTC contact risk in livestock at the herd level.
• The study highlights the complexity of MTC maintenance in multi-host settings.
• Environmental DNA detection offers a promising tool for future epidemiological research in complex disease scenarios.