Understanding Johne's disease (paratuberculosis) — a chronic wasting disease with significant cattle welfare implications.
Johne's disease causes one of the most prolonged welfare impairments in cattle farming. The subclinical phase — during which infected animals shed MAP in faeces without showing signs — may last years. Throughout this period, the immune system wages a losing battle against the intestinal infection. When clinical signs finally emerge, the disease is irreversible.
Clinical Johne's disease is characterised by profuse, watery diarrhoea that cannot be controlled. Affected cattle lose body condition rapidly despite maintaining appetite. Bottle jaw (submandibular oedema) develops from hypoproteinaemia. The progressive wasting and debility of late-stage Johne's represents severe, prolonged welfare impairment.
Control focuses on reducing transmission within herds through identification and removal of shedders, calf hygiene (preventing exposure to adult faeces), and biosecurity when buying in cattle. National control programmes involve testing, segregation, and culling strategies to progressively reduce herd prevalence over years.