One of the biggest problems for sheep and goat producers is effective
internal parasite control of Haemonchus contortus, or Barber Pole Worms.
In fact, many sheep and goats have built up a resistance against dewormers.
On April 19 the Comanche Extension Livestock and Range Committee held a
program called "Internal Parasite Control in Goats: New Techniques to
Try." Dr. Joan Burke, research animal scientist, USDA, Agricultural
Research Service explained the problems of parasitic worms in sheep and
"Abomasal and intestinal worms are the most important pathogens of sheep
and goats," Burke said. "Worm control has relied almost exclusively on
the use of anthelmintics (medicine that kills worms). You must do your
research on sheep and goats to find control methods for parasites."
Worms that are resistant survive and pass on their "resistant" genes.
"So, I don't recommend putting them [sheep/goats] out to a clean
pasture," Burke stated. "Underdosing, treating all animals at the same
time and moving animals to a clean pasture is where we have gone wrong
in treating the worms."
Benzimidazoles, Ivermectin, Doramectin, Levamisole and Moxidectin helped
create the prevalence of resistance of H. contortus, Burke said.
"It doesn't seem as bad as it sounds because not all worms are
resistant," Burke said. "Killing some of those worms may relieve the
animals for a few weeks."
But, resistance is inevitable. The rate of selection for resistance can
be greatly reduced by using two processes: FAMACHA and Smart Drenching.
FAMACHA is a selective treatment that monitors the parasites and helps
to identify severely parasitized sheep and goats. FAMACHA provides a
tool to identify anemic animals.
"FAMACHA is basically a selective deworming based on the level of anemia
determined by the color of the lower eyelid," Burke explained.
FAMACHA provides an eye color chart with five color categories. The
chart allows producers to compare the chart with the color of the mucous
membranes of the sheep or goats. To find the mucous membranes, pull down
the lower lid of the animal's eye and study the color. The redder the
membrane, the healthier the animal is. The more pink or white the
membrane is, the more anemic the animal is.
Smart Drenching is an approach in which the current knowledge of host
physiology, anthelmintic pharmacokinetics, parasite biology, dynamics of
selection for resistance and resistance status of worms on the farm are
known and recorded.
"Goats metabolize anthelmintic drugs much more rapidly than other
livestock," Burke said. "Goats should be given a dose of 1.5 to 2 times
higher than for sheep or cattle. Administer drugs orally, because
pour-ons are absorbed poorly. And, make sure to use the proper dosage-
no less or it will not work- and the proper technique."