Diagnosis and Control of Intestinal Parasites in Alpacas

under themicroscopeDiagnosis and Control ofIntestinal Parasites in AlpacasBy Stephen R. Purdy, DVMPrevention is the key to intestinal parasite controlOvercrowding and poor sanitation must beaddressed to overcome parasite infestations andto minimize the potential for reinfection. Parasitecontrol programs must be easily implemented,and must rely heavily on good managementpractices and lightly on use of drugs. It is notpossible, and may not be desirable, to remove allof the parasites from the herd. Intestinal parasitesshould be managed to avoid clinical diseasethrough a combination of practices, includingfeces removal, pasture rotation, interspeciesgrazing, and lastly, use of medication.Most scientists believe that 20 percent of theanimals in a group harbor 70 to 80 percent of theparasites. We must identify that group, treat themonly if absolutely necessary, and keep them awayfrom the rest of the herd. This is especially truefor crias, which have lower resistance to intestinalparasites because of their relatively immatureimmune systems. You should give strong considerationto removing animals with low resistance toparasites from the breeding herd. Good nutritionis the basis for being able to fight off any immunesystem challenge, including intestinal parasites.It is very important to keep the herd well-fed,with minimal competition for food. When I geta call about wanting a new medication to treatan intestinal parasite problem, I immediatelystart to investigate the management and housingsituation. Most farms with large parasite problemsare overcrowded or have underfed animals.The best way to investigate the level ofparasitism in the herd is through periodicperformance of fecal exams. There are multiplemethods of analyzing feces, but it is importantto use a consistent, easily performed technique.I usually suggest individual sampling of allsuspected animals, particularly those with poorbody condition, poor growth rates, or those withdiarrhea or loose stools. A herd screening testshould include approximately 25 percent ofthe animals in each group.The following is the procedure I use, whichI feel is accurate and easily performed.• Collect fresh feces – use 1 or 2 lubricated,gloved fingers in the rectum or groundcollection immediately after defecation.• Mix feces – add 10 mL of concentrated sugarsolution (specific gravity 1.33, made by adding2.75 cups of sugar to 1 pint of very hot or boilingwater) to a 15 mL tube. Add feces to raisethe level to 12 mL (approximately 2 grams offeces). Pour entire mixture into a cup and mixwell to release eggs/oocysts from the feces. Filterout the big pieces through a gauze pad or teastrainer and add back into a centrifuge tube.• If you are using a swinging bucket centrifuge,fill the tube to the top and centrifuge for10 minutes with a slide cover slip on.• If using a fixed rotor centrifuge, fill tubeto approximately ¼ inch below the top andcentrifuge for 10 minutes; top off tube withsugar solution, add cover slip, and wait10 more minutes.• Apply the cover slip to a glass slide and view.• The total number of eggs/oocysts counted isper 2 grams of feces. Divide the final numberby 2 to calculate the EPG (egg per gram) orOPG (oocyst per gram for coccidia) count.A few tips for viewing parasite eggs will make theprocess less daunting when you are first startingto look at slides. Start by viewing slides on lowpower (10X objective – yellow). If you are havingtrouble finding the proper focus depth, move theslide so that the edge of the cover slip is directlyunder the lens (directly above the center of thelight) and focus on that, using the coarse and thenthe fine focus knob. When you have this initialfocusing done, you next focus at the level of the airbubbles. That is where the parasite eggs and coccidiaoocysts will be found. Adjust the light inten-102 • Alpacas Magazine

sity so that you can easily see the slide withoutbeing blinded or without peering into the darkness.Do not get discouraged at first – everyone needs topractice to learn this. Repetition is the key here.A few words on parasite terminology will helpto alleviate confusion. These are generally acceptedterms used by veterinary parasitologists.• Nematode – roundworm, non-segmented;microscopic:• Strongyles – eggs all look the same, canbe differentiated by growing larvae butnot usually done• Nematodirus – largest egg; distinctive “shell”;can survive on pasture over winter to hatchin the spring• Whipworms (Trichuris) – oval eggs with“doors” on the ends• Cestode: tapeworm:• Monezia; eggs often not seen in fecals asthey are passed as white segments whichare visible on feces• Coccidia are not worms but are protozoa;microscopic:• Small coccidia – Eimeria species; ovalshaped,like a fried egg with a big yolk• Eimeria macusaniensis (E. mac) – the big one;five times larger than small coccidia; pearshaped and two-toned brown in color.As you see from the picture on the followingpages, there are three size groups when we look atparasite eggs/ova. The large one is Nematodirus.The medium-size group has strongyles, E. mac,whipworms, and tapeworms. All have distinctiveshapes to differentiate which one you are lookingat. The small one is the small coccidia. It is theparasite that takes the most time to get used tofinding at low power magnification. If you findsomething that is not one of these six, it is mostlikely not a parasite egg. If you are unsure of whatyou are looking at, move it to the center ofthe visual field and look at it under highermagnification to decide.Specific Intestinal ParasitesThe strongyles are the most common intestinalparasites of alpacas on most farms. Their eggs arepassed in the feces, and under the right conditionsof temperature and moisture, they hatch intolarvae. The larvae mature into the infectiveL3 stage, which are found primarily in the firsttwo inches of the plants on pasture. Alpacas getinfected with parasites while consuming theseplants. If we keep our pastures from becoming tooshort due to overgrazing, then the infection ratewill be low. Remove animals before all of thepasture is eaten down. Also, turn older animalsout on pasture first, before young animals, so thatthey can eat the parasites to minimize damage toyoung animals with immature immune systems.Herd Sire 2010 • 103Photos courtesy of Dr. Stephen Purdy

Strongyle infective L3 stage in a water dropleton a blade of grass.Photo courtesy of www.florida-cracker.com/worm_management.htmTop, Nematodirus (N)and Monezia (tapeworm)(T) eggs;air bubbles (A)(100x magnification)Above, Nematodirusand Monezia(tapeworm) eggs(1000x magnification)Small coccidia (Eimeria species) cause problemsprimarily under conditions of overcrowding andfecal contamination of food. They are animalspecies-specific, meaning sheep, goat, camelid, andbovine coccidia are different, and will not crossinfectother species. The infective stage is consumedon pasture or by animals eating off of ground whichhas been contaminated by infected feces. You willsee this in the winter when animals are not onpasture, as well as in other times of the year. Smallcoccidia are usually not a significant clinical problemin adults, so do not medically treat animalsif they are asymptomatic. Infected crias can showsigns of diarrhea and poor weight gain.Look for small coccidia oocysts in fecals, butthey can take several days to show up after thediarrhea starts. My rule for diarrhea in a cria withouta fever is to treat for coccidia, even if the fecalis negative. Emphasize cleanliness in the herd toprevent reinfection. Do not treat all of the crias inthe group, but do monitor feces, growth rate, andbody condition, and run periodic fecals to decidewhich alpacas to treat with medication, if any.Young animals at shows are subject to diarrheaon occasion. This may be due to a viral intestinalinfection, but the stress of an unfamiliar situation,with many new animals and sounds, may alsocause a subclinical coccidia infection to becomeactive and overt. The animals did not pick up thecoccidia at the show. They were already carryingit, and their immune system was keeping it undercontrol, until the show stress weakened theirimmune response.E. mac (Eimeria macusaniensis) was thought ofas always being a deadly parasite before we startedusing more accurate techniques to diagnose it,and then realized that it is very common inanimals with no clinical signs of disease. It shouldbe thought of just like small coccidia, in myopinion. Infection can result in fatalities, butthis is most often in poor-doer adults withchronic disease problems.Clinical signs of E. mac infection in poor-doeradults or young animals include transient or rarediarrhea, poor appetite, weakness, swallowingproblems, and rarely, even neurologic signs. Lowblood protein (low albumin) disproportionate tothe anemia is seen in chronic disease situations inadult alpacas. Consider treating poor-doer adultsof unknown diagnosis with low protein, poorappetite, etc., for E. mac.However, most E. mac infections are not symptomatic!The oocysts are intermittently shed, andthey are not evenly distributed in the feces.104 • Alpacas Magazine

Photos courtesy of Dr. Stephen PurdyAdult Fasciola hepatica liver flukesWhipworm (Trichuris) egg (1000x magnification)106 • Alpacas MagazineHow many parasite eggs or oocysts in a fecal are significant?• Small coccidia• Crias with diarrhea: any are significant;treat individual animals and watch the entiregroup, especially crias.• Adults or crias with good growth rates and nodiarrhea: do not treat; emphasize cleanlinessand other management methods of control.• E. mac – same as small coccidia• Intermittently shed in feces with a longperiod of time from infection to shedding.• Adults with poor body condition and lowprotein without low red blood cell count(without anemia) = treat.• Stronglyes• 25 or more per slide is significant, but onlyif the animal has clinical signs of parasitism;review management and watch for disease.• Nematodirus• Any may be significant because it is a lowshedder; look for clinical signs of diseasebefore medicating.• Tapeworms• May not want to treat the affected animalas they may expel tapes on their own; watchthe feces to see if segments disappear.• Expect reoccurrence in the area, butnot always right away.• Whipworms• Treat any amount found if the animal hasclinical signs of infection; a tough parasiteto get rid of in the environment.Should you treat animals diagnosed with intestinalparasites of any kind with no clinicalsigns of disease? I would suggest no, you shouldnot. Use the results of fecal exams to decide ifyour parasite management practices are adequateand make the appropriate changes. Do not lookfirst for a different medication! The adverse clinicalsigns I look for when deciding to medicatealpacas include: poor body condition, failure togrow at a normal rate in young animals, weightloss, and diarrhea.Deworming medications are poisons – theykill worms, and worms are animals. Some medicationshave been associated with problems incamelids. Valbazen ® has been reported to causeabortion in pregnant camelids. Ivermectin(Ivomec ® ) and doramectin (Dectomax ® ) should beconsidered as environmental contaminants, asthey pass out of treated animals in their feces andurine in active form. They can kill beneficialinsects, such as dung beetles and worms, in thesoil around manure piles and where fecal, andthus drug, runoff occurs.Work done at the University of Massachusetts,Amherst proved that animals treated with onesubcutaneous injection of ivermectin haddetectable levels of the active drug in the feces forat least two months! (Purdy, unpublished data,2006). It is not known whether composting willbreak down these drugs in feces to make theminactive. Thus, it may not be a good idea to putcomposted alpaca manure from animals treated