At 10:00 AM, the last technical session Control of Parasites in Pastured Small Ruminant Livestock through Integrated Use of Pasture Management, Botanicals, and Pharmaceuticals began. Ms. Diane Schivera, Maine Organic Farmers and Gardeners Association, was the moderator. Dr. Tatiana Stanton, Cornell Small Ruminant Extension Specialist, and Dr. Katherine Petersson, University of Rhode Island Assistant Professor of Animal and Veterinary Science, were the two speakers. They rotated their presentations by topic. Ms. Schivera gave out 2 handouts, Oregano oil for internal parasite control in sheep, goats, and beef cattle (acts an ionophore or coccidiostat), and Vermi-Tox Study, a herbal dewormer containing condensed tannins.
Dr. Katherine Petersson started out the session with a presentation called War of the Worms. Worms in small ruminants are not a new problem. In the 1920s, drenches that included carbon tetrachloride and copper sulfate/nicotine were used to kill intestinal worms. Gastrointestinal (GI) nematodes are the biggest health problem east of the Rockies. ALL GRAZING ANIMALS HAVE WORMS!!!!!!!!! The most important is the barber pole worm, Haemonchus contortus. It is an abomasal (stomach) parasite, exploiting many environments and management practices. Typically, it is a warm weather worm but survives everywhere with adequate moisture. In summer, it is the predominant stomach worm even in Vermont. It is a blood-sucking parasite. A heavy burden of these worms can result in anemia and bottle jaw, a swelling of the lower jaw, and weakness. They consume a half-cup or more of blood per day. They do not cause diarrhea usually. Subclinical losses are possible. Decreased gains and growth are typical.
Related parasites also contribute to problems and can cause diarrhea are brown stomach worm (Ostertagia, Teladorsagia) and Trichostrongylus. The others are less important. The brown stomach worm (Ostertagia spp.) used to be considered the most serious parasite of sheep in cool climates. The worm develops in gastric glands of stomach (abomasum) and destroys the glands as they grow. It decreases appetite, digestion, and nutrient utilization. Clinical signs of infestation of this worm are diarrhea, reduced appetite, and weight loss.
GI nematodes (worms) have a life cycle that goes from an egg to worm stage. Eggs are in the dung of ruminants. When they are deposited on the ground, it takes from 5-7 days to hatch in warm weather. Once the worms hatch, they climb up on grass blades and can swim in dew or rain drops adhering to the leaves. The ruminant eats the grass and thus gets infected. These infective worms may live for 17-21 days. The worms while in the open environment are encased in a protective sheath. Once they are in the ruminant’s rumen, they shed their sheath chemically. While they are in the sheath, they can’t eat once they reach the infective stage. Once metabolic reserves are used up, they die. The hotter it is, the faster they wiggle, the quicker they die. Under cool, moist conditions, they can live for months. Freezing kills some species, including Haemonchus. In the winter, on pasture as eggs or larvae, only some species can make it through the winter. As larvae in the host in a dormant state (arrested or hypo-biotic), they can survive the winter. There is no sign of disease and no eggs found in the feces.
Goal is to manage the worms, not to eradicate the worms. Goal is to keep worms at a level that does not have detrimental health effects. Climatic effects on worm abundance and presence are: Warm, wet grazing seasons are perfect for Haemonchus and with a short life cycle of about 3 weeks from infection to egg laying; milder, shorter winters extend transmission season. Vermont worm season is July to August. Virginia worm season is June-October, and in Florida worm season is all year long. Barber pole worm has become more important in the Northeast. Past wisdom—other worms more important, but today veterinarian and producer experience say it is the most important. Most numerous eggs found in project samples in New England. The increased importance is probably due to resistant worms and/or changing, lengthening grazing season. High density grazing on permanent pastures increases chances for infection.
Since 1960s we have had fantastic drugs for treatment of sheep and goat GI nematodes. They are highly effective against adults and larvae (>95%), safe, nonprescription, and CHEAP. However, the overuse of these drugs has caused drug resistance. Some worms with a genetic ability to resist a drug always exist at low levels because of random gene mutation. When the drug is not present, the resistant worms have no advantage. Use of a drug gives those worms an advantage and gradually the number of resistant worms increases. Forty to 55 percent of NY and PA goat herds show severe resistance to Ivermectin and Fenbendazol, respectively. Fecal egg reduction rate study for each dewormer class in a New England showed only a 50% reduction for Benzimidoles, a 65% reduction for Macrolides, and a 75% for Nicotinics.
Management practices that speed up development of drug resistance are:
- Frequent treatments
- Treating all the animals at once
- Treating and moving to clean pastures
- Treating when there aren’t many worms on pasture (drought, end of winter).
All these decrease the refugia on your farm. Refugia are the portions of the parasite population not exposed (=unselected) when a drug is administered. Worms on pasture, and in untreated animals, keeps susceptible worms in the population. This is a good thing. The higher the refugia, the greater the chance that there will be susceptible worms around to reduce the chances of 2 resistant worms mating. Goals of rational drug use are to prevent disease/loss and minimize rate of development of resistance, so reduce treatments and maintain refugia.
Sheep and goats metabolize drugs differently so the effective dose in goats is two times the sheep dose except for Levamisole (1.5x) and Moxidectin injectable—do not use it. Other ways to increase refugia are:
1. Don’t deworm and immediately move animals to safe/clean pasture, only
resistant worms will go to the new pasture.
2. Put back on old pasture for awhile to pick up susceptible worms or just treat some animals before move.
3. Don’t deworm all animals at the same time.
New drugs keep coming out, such as amino acetonitrile, Monepantel—Zolvix. It is a different class of drug, but it will select for resistant worms just as quickly as all the others did.
As an alternative to commercial dewormers are herbal dewormers. Several products are commercially available containing variety of plants, but are not regulated by the FDA. No requirement for studies to support efficacy or safety and no guarantee of consistency from bag to bag. Dewormer use in organic sheep operations guidelines are:
- Ivermectin, moxidectin and fenbendazole (prescription only) currently allowed for limited use
- Prohibited in slaughter stock sold as organic
- Allowed for emergency treatment of dairy and breeder stock when all else fails
- Milk or milk products cannot be labeled organic for 90 days following treatment
- If offspring to be sold as organic meat, cannot be used in last third of gestation or during lactation
- Must treat in humane situation
Parasite Control in Sustainable Systems should follow these guideposts. Parasite losses are a management disease. We have ways of controlling parasites. Each producer has to decide which control methods work best for him or her. An integrated parasite control program is a must. Sheep and goats develop a natural immunity to GI worms. This immunity controls parasites, but does not elimin-ate them. Immune animals will still have eggs in manure. This immunity is in place at maturity. Goats more susceptible than sheep to GI worms. In all flocks, some animals are more susceptible than others to worms.
Animals with temporary high susceptibility to parasites are the young—before immunity develops, lactating ewes and does, and ewes at time of lambing are especially susceptible. Poor health or nutrition animals are also highly susceptible. Animals with an inherited high susceptibility to parasites should be culled. All other things equal, \~30% of the animals have 80% of the worms. Select for more parasite resistant breeding stock. Ask breeders if they have information on their breeding stock resistance to worms. Use fecal egg counts to assess problem in your flock.
Anyone can make any group of any breed more parasite resistant with selective breeding. Sheep breeds with higher levels of resistance to parasites are St. Croix, Katahdin, and Gulf Coast/Florida Native. One has to keep selecting for parasite resistance even in more resistant breeds. There is less research on variation in resistance in goat breeds. Immunity can be used effectively by doing selective deworming programs. This concentrates dewormer use on animals that need it the most. Less dewormer is used. It slows development of resistance to dewormers. Treating the high 33% of the flock with a drug that causes a 99% fecal egg count reduction (FECR) reduces daily pasture contamination with eggs by 80%. Following treatment, > 95% of eggs are being shed by untreated goats = REFUGIA.
To discover the highly susceptible sheep and goats to barber pole worm, FAMACHA is a popular targeted (selective) deworming program. It matches color of sheep or goat ocular mucous membrane to a color chart. A #5 color indicates an anemic animal that is heavily wormy. It identifies which ones to treat, but it only works for barber pole worm. Another means to select susceptible animals is to identify wormiest animals by doing fecal egg counts.
Dr. Tatiana Stanton gave a presentation entitled Basics of Pasture Management to Help Control Internal Parasites. On pasture, eggs in feces fall from animal to ground. Requires warmth (may be as cool as 50+F but lots of response by 60 F) and humidity to hatch into first stage larvae, L-1. This occurs in 1-6 days. L-1 eats bacteria in feces and grows, molts (sheds skin like a snake) and becomes L-2. L-2 also eats bacteria in feces and then molts.
Direct sunlight can heat fecal pellet to 155 F and sterilize pellet. This is an excellent time to mow a pasture short to aid in drying the fecal pellet. Shade trees and tall, dense grass increase humidity and protect fecal pellets from the sun, increasing worm hatch and survival problem. L-2 molts to L-3. However, the cuticle (skin) is not shed, so the L-3 has 2 layers of cuticle (sheath). This makes the L-3 much more resistant to drying out. However, the L-3 cannot eat, because his mouth is covered. He must live off his stored reserves. Since he is cold-blooded, his metabolism speeds up when it is hot. He can only live about 30-60 days in hot weather or 120-240 days in cool weather. He can not survive freezing.
Pasture becomes infective at this time. Most L3s do not get more than about 3 inches high on grass blade. The L-3 must escape from the fecal pellet to infect an animal. The L-3 can only live about a week or two inside a fecal pellet if it is hot and dry. Pellet must be broken up by rain (2 inches in a month’s time), then the larvae scoots on a film of water (from rain or dew) and gets under fallen leaves or other debris, OR scoots on a film of water 2-3 inches up onto fresh forage. For the barber pole worm life cycle, maybe only 2-10% of eggs end up as L-3 larvae on forage. L-3 must be eaten by a goat or sheep to continue development.
Cattle and horses can “vacuum up” L3 larvae from goat pastures and stop its life cycle. They are not hosts for the worm. If available, use them to graze pastures in between rotational cycles of sheep or goats.
Use clean or safe pastures – wise management decisions about pasture height, grazing duration and pasture rest - easy to say, difficult to implement for entire grazing cycle. Give priority to recently weaned young stock > lactating does/ewes > dry animals. Practice evasive by moving animals fast enough to prevent infection from feces deposited during current grazing period (autoinfection). Takes 3-5 days to hatch at 77-79F, 15-30 days to hatch at 50–52F. Often \~5 to 14 days from egg to L3. Play it safe with 4 day (wet, warm) to 7 day (cooler, drier) grazing duration. Move earlier if pasture getting too short – i.e. 3 inches.
Allow a long enough rest period that there is substantial L3 die off before animals return to graze (60 – 105 days). Problem with this latter remark is pasture rest periods to control barber pole worm need to be longer than normal recommendations for either pasture health or nutritional value of the forage (42 days or less). Options for keeping pastures from getting too mature while avoiding barber pole worms are graze cattle or horses in between sheep or goats, clip pasture, or harvest hay crop. Rotational grazing in the spring appears to reduce the “barnyard effect” and delay the onset of summer parasite problems.
Barnyards with grass or other good forage lead to high concentration of manure and internal parasites in grazing material and can contribute greatly to herd contamination with internal parasites. There may be a “barnyard effect” in pastures that border a barn and are not rotationally grazed to keep higher grass stubble heights. Worm egg counts were much higher in kids in early spring that were on continuously grazed pasture versus rotationally grazed due to this barnyard effect. By late July egg counts were similar.
Central graining and watering areas can also have a barnyard effect. Some options to help reduce barnyard effect is to lay down gravel, concrete, or herbicides, close off access to barnyard or provide hay in barn at night when animals come in from pasture to cut down on night grazing in the barnyard, make barn yards small so that no grazing occurs, or put in lanes or leave animals out 24/7.
Dr. Peterssen did the next segment on Evaluate the effects of vitamin E supplementation (10 IU/kg BW/day - VE 10) on lambs experimentally infected with Haemonchus contortus. Elevated levels of vitamin E supplementation had a beneficial effect on the abomasal worm burden. VE 10 lambs tended to have a lower mean fecal egg count and higher eosinophil and globule leukocyte counts. Future studies will examine mechanistic effect of VE supplementation on GI nematode infections in lambs including direct effects on parasitic defense mechanism.
Dr. Peterssen also briefly mentioned that cranberry leaves contain high levels of proanthocyanidin condensed (PAC) tannins. The leaves are by-product of harvest in Wisconsin and Massachusetts. The abstract is in a form of a powder and has anthelmintic properties. Cranberry leaf powder PAC exhibited anthelmintic activity against L1/L2 H. contortus after 48 hour incubation at a concentration of 1.25 μg/ml, larval development at a concentration of 600 μg/ml, and adult H. contortus after 48 hour incubation at a concentration of 1200 μg/ml. Cranberry leaf powder showed anthelmintic efficacy through fecal egg reduction at weeks 1 and 2 post treatment at a concentration of 75 μg/ml.
Dr. Petersson made us aware of a OREI research grant, USDA OREI Forage-based Parasite Control in Sheep and Goats in the Northeast U.S. These universities are involved in the project: West Virginia University, Cornell University, University of Rhode Island, University of Wisconsin, and Virginia Tech. This project is evaluating of birdsfoot trefoil (BFT) cultivars – URI tested 7 conventional varieties (Empire, Leo, Bull, New York, Norcen, Pardee, Bruce). The project also studied 51 high tannin varieties with limited seed availability (kept 20 most promising for multiplication of seed). There is an analysis of the condensed tannin profiles. There will be an assessment of the anthelmintic effect of BFT cultivars, and assess the effect of BFT on immune function. The project will also evaluate herd health and economic outcomes of BFT pasture mixes for GIN suppression.
Dr. Stanton followed up with On-Farm BFT Studies. Coordinating on-farm studies with participating farmers who will investigate how to best utilize BFT in the field. Want to work on-farm starting spring and fall 2014. Let Tatiana know if interested!
Researching these questions:
- Are there practical ways to incorporate BFT into grazing systems and control parasites?
- Variety differences in terms of effectiveness and suitability?
- Amount needed?
Dr. Stanton also covered Copper Oxide Wire Particles for Barber Pole Worm Control in Goats and Sheep. Sheep are ten times more susceptible to copper toxicity than cattle. When consumed over a long period of time, excess copper is stored in the liver. No damage occurs until a toxic level is reached. Then, a hemolytic crisis occurs with the destruction of red blood cells.
Copper is closely related to molybdenum, and copper toxicity occurs when the dietary ratio of copper to molybdenum increases about 6-10:1. Affected animals suddenly go off feed and become weak. Mucous membranes and white skin turn yellowish brown color. Urine is red-brown color due to hemoglobin in the urine. Copper oxide wire particles (COWP) were developed as a slow release source of copper for cattle on copper deficient soils. COWP particles are retained in the abomasum long enough to permit acid solubilization of the copper. This results in a gradual release of copper which reduces risk of copper toxicity to the sheep.
COWP boluses (Copasure©) available commercially and already approved by organic certification associations because of their role in copper supplementation. 12.5 and 25 gram boluses for calves and cows need to be repackaged into far smaller doses suitable for growing sheep and goats! Effective against Barber pole worm (Haemonchus contortus), but thought not to be effective against arrested worms. What time of year best to give? Not effective against Brown stomach worm (WHY?), and also not effective against tapeworms. .5-2 g dose for lamb or kid and 1-4 gram dose for ewe or doe. The lower dosages may be repeated a few times a year depending on soil and diet levels of Cu and Mo.
Studies in SE US focus on looking for lowest dosages that can be used in combination with FAMACHA – give COWP to your vulnerable “3s” (lambs, kids, lactating or late pregnant females) rather than giving a commercial dewormer. The mechanism that cause COWP to work is unknown. It seems to work poorly in animals that are stressed or run down. It is also not effective in just weaned kids or lambs. When it works, it is quite effective, killing 75-95% of Barber pole worms.
Cornell has a grant to develop guidelines on the use of Copper Oxide Wire Particles in the Northeast US. Boluses or capsules are injected into the throat and are swallowed. The capsules breakdown and wire particles of copper get dispersed into the stomach. The wire rods get trapped in the first 3 stomachs. The fourth stomach’s acid slowly dissolves the wire particles. The copper gets absorbed form the intestine.
A Cornell study with milking goats found COWP not as effective as a dewormer (assuming there is no resistance to the dewormer), but no discarding of milk was necessary. Two grams per head appeared to work as well as 1 gram per 22 lb. live weight and did not significantly increase the copper levels in milk. A study conducted on 3 sheep farms had these results. Fecal egg counts decreased at all farms after giving either .5 to 1 gram per head. Results were short term at two farms but lasted at least 42 days at the third farm. On lambs, .5 gram per head dosages appeared to be as effective as 1 gram per head dosages. We need more studies to identify why the effect at the three farms differed. This concluded the technical session program.