The Basics of Biosecurity

How Diseases Spread on the Farm

Many germs cause disease in livestock and poultry. Some can make people sick, too. Fortunately, if we look at how germs spread, we can find ways to manage disease risk through biosecurity.

There are five main ways that diseases spread.

A close up of a horse with nasal discharge snorting and droplets in the air

Airborne spread occurs when an animal breathes in germs in the air

A close up a cow with white nasal discharge present in each nostril

Direct contact spread happens when a susceptible animal touches an infected animal or person

A black pig standing in a feed trough with water in the bottom

Indirect contact spread happens when an animal touches objects or environments that are contaminated with germs

A close up of feed pellets and a yellow scoop

Ingestion (or oral spread) occurs when an animal eats feed or drinks water that is contaminated with germs

A close up a tick embedded in the skin of an animal

Vector spread usually happens when an infected insect (like a tick or mosquito) bites a susceptible animal

Some infections can spread from animals to humans or humans to animals. These are called zoonotic diseases. Any animal or animal product, including meat, milk, eggs, and wool, can be involved in zoonotic spread. Young children, older adults, pregnant people, and people with a weakened immune system are more likely to get very sick if they contract a zoonotic disease.

Some common sources of germs are depicted below. Practice identifying disease risk by clicking on each of the exclamation marks: