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Description
Anthrax is a serious, often fatal zoonotic disease of wild and domestic mammals caused by the spore-forming bacterium Bacillus anthracis. The disease occurs worldwide and often in outbreaks. The infected host sheds bacteria into the environment which sporulate when exposed to air.B. anthracis spores are highly resistant and can survive in the environment for many years. These spores may be ingested by grazing animals but do not generally present a threat to humans. Animals may become infected if they ingested large quantities of spores. Additionally, biting flies seem to have a role in transmission of spores in areas of endemic disease. Humans may be infected via contact with infected animal tissues, exposure to high concentrations of spores or contacted with infected animals. In herbivores, the disease commonly presents as a peracute onset septicaemia with a high mortality rate. In dogs, humans, horses and pigs the onset is less acute. There are three main forms of the disease; gastrointestinal, pulmonary or cutaneous.
Clinical signs
Ruminants and horses
In both cattle and horses, the disease course may range from peracute to chronic. Animals may be discovered dead in the field before any clinical signs have been observed.
- Fatal peracute septicaemia
- Sudden death
- Acute onset severe pyrexia
- Depression
- Neurological signs such as staggering or trembling
- Cessation of rumination
- Subcutaneous oedematous swellings
- Congested mucous membranes and petechiae
Pigs
Pigs are relatively resistant to anthrax and the disease often has a more chronic course affecting the oropharyngeal region. The disease often begins as an oedematous cellulitis of the the neck, head and regional lymph nodes. This may cause death by asphyxia.
Dogs
Dogs are rarely affected, but develop a similar disease to that found in pigs.