Agriculture Reference
In-Depth Information
Yeasts and fungi don't often cause problems for shepherds, though they
can cause some skin problems, respiratory infections, and mastitis (that is, an
infection in a ewe's udder). Yeast and fungal infections often follow extensive
use of antibiotics.
For shepherds, internal and external parasites are the most common biologi-
cal bad guys. In fact, in comparison with other animals, sheep are more resis-
tant to bacterial and viral diseases but are far more susceptible to parasites.
Although parasites can affect both sexes and all ages of sheep, they are deadli-
est for lambs and young ewes.
Parasites aren't a single class of organisms but run the gamut from pro-
tozoa (single-celled members of the animal kingdom) to far more complex
organisms, like worms and insects. In simple terms, a parasite obtains food
and/or shelter from another organism. Most parasites are relatively benign
(for example, normal fl ora meet this defi nition). Some, such as biting fl ies,
are mainly a nuisance. But others, such as intestinal worms, may cause seri-
ous and even fatal illness. Sheep that become weakened and run down by a
parasite infestation can be killed by the parasites themselves or fall victim to
a secondary bacterial or viral disease.
Parasites are capable of attacking most parts of the body. Luckily, some of
the worst parasites aren't found in North America, though in the southeast-
ern United States, internal parasites are considered a limiting factor in sheep
production. Strong, healthy animals that are managed on clean pastures are
less likely to have severe parasitic infections, and some breeds — like the Gulf
Coast Natives — are known for a high tolerance to parasites.
Internal Parasites
A heavy load of internal parasites causes a vicious cycle of undernourishment
of the sheep that in turn makes them more vulnerable to parasites. Deaths
from parasites occur most often in lambs, yearlings, extremely old sheep, and
poorly fed sheep. Internal parasites reduce productivity and cause anemia,
wool break, progressive weakness, and sometimes death.
Worms are the predominant internal parasite in sheep, and there are 11
species that cause problems for shepherds in North America. They typically
inhabit the abomasum (the true stomach), small and large intestines, heart,
and lungs.
