Infectious agents are living organisms that cause disease
Infectious agents are living organisms that cause disease or illness and can be spread from bird to bird. These include ‘germs’ (bacteria, viruses, fungi), external parasites (lice and mites), and internal parasites (worms, coccidiosis, blackhead). Infectious agents that cause disease are also referred to as pathogens.
Some environmental conditions can also make birds sick. Unlike infectious agents, the illness is not spread between birds. When the environment affects the health of birds it is usually because the animals are unable to adapt to the conditions. Environmental factors that can cause disease include:
- nutritional deficiencies
- poor air quality
- temperature extremes
- physical stress
- exposure to disease-carrying vermin and insects such as rodents and darkling beetles.
Severe physical stress can reduce the birds’ ability to resist disease. Flocks rely on people to give them:
appropriate feed and clean, uncontaminated water
appropriate environmental conditions
Without these, birds may suffer stress from fear, malnutrition, dehydration, over-crowding, dirty conditions, and extremes in climatic conditions.
How infectious agents spread
The disease can be spread by new infectious agents entering your flock or by the spread of established infectious agents that are already in the flock.
The disease can be spread by:
people – including through clothing, hands, and footwear
domestic and wild birds – through droppings, feathers, and discharges from the nose and mouth
contaminated equipment and vehicles
feed and water
animals (e.g. dogs, cats, rodents)
insects (e.g. mosquitoes, flies, beetles) – through the transmission of diseases such as fowl pox, tapeworm, Newcastle disease, and Salmonella. In many cases of infection, birds (and other animals) keep illness at bay and do not appear sick. These so-called ‘carriers’ do not look sick but can spread disease, often without detection. This is often the case with the food safety pathogen Salmonella, where infected birds do not usually show visual signs of infection.