Agriculture Reference
In-Depth Information
Chemical, biological, and physical agents cause illness. Chemicals include
toxins such as pesticides, cleaning products, and batteries. Biological agents
are probably the most common cause of illness and include parasites, bac-
teria, viruses, fungi, and yeasts. Physical agents are environmental factors,
such as drafts, mud, stress, and improper diet. Physical factors rarely cause
illness or death by themselves (though hypothermia can readily kill), but they
most defi nitely worsen a situation in which a chemical or biological agent is
involved by causing stress and weakening the animal's immune system.
Chemical Agents
Chemicals cause poisoning. Some chemicals are biological in nature — for
instance, poisonous plants — but it's the chemicals in a plant that may cause
illness. Poisoning can be avoided by diligently paying attention to what the
sheep can access. Remember to properly handle and dispose of anything that's
chemical in nature. Try to be conscious of the environment where your sheep
spend time; for example, if the sheep spend time in an old barn with lead
paint, you could have trouble. And be sure to learn what poisonous plants
grow in your area.
Biological Agents
When a biological organism causes disease, it's called a pathogen. Most often,
pathogens are introduced organisms, though sometimes even normal fl ora
can become pathogenic. In sheep, most of the diseases we think of, such as
pneumonia and scours, are caused by bacteria or viruses, though parasites
cause more general health problems.
Bacteria are single-celled organisms. Some are crucial to good health
but others are pure trouble. Bacteria can be treated with antibiotics, though
some bacteria are resistant to certain antibiotics, meaning that the antibiotic
doesn't work against that particular bug.
Unlike bacteria, viruses do not respond to antibiotics at all, period, end of
story. (Those antibiotics that the doctor gave you for a sinus infection won't
help with your daughter's cold. In fact, taking antibiotics for a virus may
increase bacterial resistance.) Scientists and medical folks now believe that a
lot of the antibiotic resistance we're seeing stems directly from improper use
in animal agriculture, such as routine feeding of antibiotics and not following
withdrawal times.
