Treatment and control by vaccination of erysipelas in farmed emus (Dromaius novohollandiae).

Abstract

To study erysipelas in farmed emus and the treatment and control of the disease by vaccination. A retrospective study of field outbreaks in emus and challenge experiments in mice using field and vaccine strains of the organism. Outbreaks of the disease were described. Field strains of the organism were identified and tested by challenge experiments in mice against commercial vaccine strains. Erysipelas was characterised by sudden death in yearling emus. Deaths mainly occurred during the cold wet months. Mortalities of 6 to 10% were seen within the first 7 to 10 days of an outbreak. Clinical signs were uncommon but some birds exhibited lethargy and greenish diarrhoea. Necropsy findings included marked petechial haemorrhages on the serosal surface of the large intestine in particular, pericardial effusion and congestion and mottling of the liver. Treatment consisted of individual or mass medication with procaine penicillin, reduction of stress factors such as overcrowding, and spelling and rotation of paddocks. Isolates from two field outbreaks were identified as strain 21. Complete protection was provided by a commercial strain 2b vaccine against challenge by strain 21 field isolates in mice. Annual vaccination of birds at 4 weeks and again at 8 weeks of age appeared to control further outbreaks on farms where the disease had previously occurred and vaccination appeared to protect for at least 12 months.