As the season begins it's good to refresh knowledge on topics not always front of mind, like how diseases spread and how we can avoid exposure. Disease causing agents can expose animals and people through different routes. Some diseases are spread only one way; others are spread by several. Preventing exposure helps prevent disease.
1. Aerosol (breath or inhalation)
Droplets containing disease agents pass through the air and are inhaled. Examples include bovine viral diarrhoea (BVD), foot and mouth disease (FMD), Mycobacterium bovis (tuberculosis).
2. Oral (ingestion)
Eating feed, drinking water, or licking/chewing objects contaminated by disease agents in manure, saliva, urine, or parasites. Examples include botulism, bovine spongiform encephalopathy (BSE), FMD, Johne’s, Salmonella.
3. Direct contact
Disease agents in blood or saliva touches open wounds, mucous membranes (e.g., eyes, gums), or skin through nose-to-nose contact, rubbing or biting. Examples include external parasites, FMD, leptospirosis, rabies.
4. Reproductive
A sub-type of direct contact that includes diseases spread through mating or to the foetus during pregnancy. Examples include BVD, neosporosis, tuberculosis.
5. Vector
Insects, wildlife, rodents, wild birds, and other animals like dogs and cats can spread germs mechanically (on the footpads or feathers) or biologically (insect bite or shed in faeces). Examples include anaplasmosis (ticks), contagious mastitis (flies), vesicular stomatitis (mosquitoes).
6. Fomite
An inanimate object (e.g., needle, footwear, livestock trailer, milking unit) contaminated with a disease agent can spread it to other animals it touches. Examples include bovine leukaemia virus (BLV), FMD, mastitis, ringworm.
Zoonotic
Diseases spread between animals and people through the same ways described above: aerosol, direct contact, fomite, oral, and vectors. Examples include anthrax, tuberculosis, leptospirosis, rabies, salmonellosis.