Dealing with the small ruminant nightmare

by Sally Colby

Anyone who raises sheep or goats is aware of the mounting issue of parasites’ resistance to available anthelmintic products. Although new formulations are available in other countries, such products aren’t yet options in the U.S.

At a recent meeting of the North Carolina Sheep Producers’ Association, two veterinarians shared information about the use of copper wire oxide particles (COWP) in managing Haemonchus contortus. This parasite, commonly known as barber pole worm, is one of the most deadly parasites of small ruminants.

Dr. Melissa Gamble, who practices with Healing Springs Large Animal in Galax, VA, discussed H. contortus management, describing the parasite as the biggest challenge for the sheep and goat industry. Gamble said the parasite is present in flocks and herds throughout the U.S., and that understanding the life cycle of H. contortus is an important step in managing this potentially deadly parasite.

Mature barber pole worms are about one inch long and are named for their red and white spiral appearance. “The red is the gastrointestinal tract, and the white is the reproductive tract that spirals around the entire worm,” said Gamble. “They suck blood and lay eggs – that’s about all they do.”

Adult worms are voracious feeders, biting into the lining of the abomasum to suck blood. Gamble said lambs or kids with high numbers of the worms can lose up to one-fifth of their blood volume in one day, leading to death in just five days.

One of the first observable signs in sheep and goats is pale mucous membranes, easily assessed by examining the inner eyelid. Gamble explained that FAMACHA scoring, a 1 through 5 scale based on the color of the inner eyelid, is the best determinant of this parasite’s presence. “The next sign is weakness and less hardiness,” she said. “Animals don’t grow as well as the rest of the flock or herd. As the anemia becomes more progressed, they might develop bottle jaw, which is fluid accumulation under the chin.”

Gamble explained that when parasites suck blood, they’re also getting protein from the blood, and this loss of protein contributes to fluid accumulation. She also noted that when diarrhea is observed in infected young stock, it’s more often due to coccidia.

“Their life begins in the abomasum as an egg,” said Gamble of the H. contortus life cycle. “Adult females lay eggs in the abomasum, eggs pass through the gastrointestinal tract, and once they’re out of the tract and in feces on the ground, eggs develop into larvae and complete three larval stages.” Gamble added that larval development is faster in a warmer environment, and at minimum, takes about five to seven days for eggs to mature to the infective third stage larvae.

As larvae approach the third stage, they migrate upward on blades of grass, aided by dew or other moisture. The sheep or goat consumes larvae, which travel to the abomasum. Once mature, adult worms attach to the abomasal lining and begin to suck blood and lay eggs. Gamble said the worms lay eggs for one to two months at a rate of up to 5,000 eggs per day.

One step producers can take to minimize this parasite is careful management. Rotational grazing helps break the life cycle. Another option, which helps significantly when the worms are rampant, is placing animals in a dry lot and feeding them off the ground to limit ingestion of larvae.

Strategic deworming also helps manage Haemonchus and reduces the risk of the parasite developing resistance to deworming products. The animals’ FAMACHA scores estimate the level of anemia. Only animals that need deworming are treated, which reduces resistance and helps build refugia – a healthy level of parasites the animal can live with and that are not exposed to dewormers.

Another option is the use of COWP boluses. The boluses contain copper oxide wires and are administered orally. “The bolus passes through the rumen and into the abomasum where they stay,” said Gamble. “The boluses break down, resulting in a high level of copper in the abomasum that inhibits parasites’ ability to reproduce.”

COWP boluses were originally used as copper supplements for cattle and sheep. While sheep are sensitive to copper, the copper oxide wire particles in the boluses are poorly absorbed systemically and the copper remains primarily in the abomasum. However, because sheep are sensitive to excess copper, it’s important to not overdo COWP treatment. Various research projects show different figures for the frequency of COWP administration for best results, but in general, the concentration of copper remains high enough to kill parasites for 20 to 80 days.

When Dr. Nikki Gooch of Henry River Mobile Vet Services in Hickory, NC, was an intern, she studied the use of COWP boluses. The why of the study was easy: Haemonchus is a problem, animals infected with Haemonchus die, lambs gain less weight and there’s dewormer resistance. The more difficult aspect was that weaned lambs had not been studied, so one objective was looking at the potential stress of weaning and how stress contributes to higher parasite populations.

Weaned, untreated lambs were checked for packed cell volume (PCV), which is the basis for FAMACHA scores. “We did fecals before we started,” she said. “Ten days after treatment, we did PCVs and fecals again. Haemonchus eggs were lower in the fecals we did afterwards.” Gooch said research didn’t determine whether the copper reduced the number of adults or the number of eggs, but other research indicates that adult worms are killed.

“We didn’t have a dose established in 2104 when I started the study,” said Gooch, adding that previous researchers used levels between a half gram to six grams. “They said to always use the lowest dose possible, but didn’t know what that was. One paper showed that two grams is most effective and produces the lower concentration of copper in the liver based on post-harvest liver analysis.”

Gooch said the study showed COWP treatment did not significantly reduce average daily gain. “We weighed the lambs to make sure the copper wasn’t negatively affecting them,” she said. “We didn’t see any signs of copper toxicity, but we didn’t take liver samples because animals were going to be treated one time – not like ewes that might be treated several seasons in a row.” Boluses should be administered with a balling gun to ensure proper placement and swallowing.

The American Consortium for Small Ruminant Parasite Control (ACSRP) recommends a half gram to one gram for kids and lambs, and one to two grams for ewes administered no more than four times in one year.

Up-to-date research on COWP and parasite management recommendations are available at www.wormx.info.

2020-01-27T14:46:33-05:00January 27, 2020|New England Farm Weekly, Western Edition|0 Comments

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