Parasite Control for your Alpaca Herd

Pamela G. Walker, DVM, MS, DipACVIM-LA

Farm Veterinarian, Alpaca Jack's Suri Farm

Assistant Professor, The Ohio State University

 

Internal parasites can be a problem in Camelids without appropriate monitoring. There are many different parasites that need to be considered. Parasites that we consider to be the most important in older crias through adult camelids are Strongyles (which includes Nematodirus), Trichuris (Whipworms), Capillaria, Tapeworms, Coccidians and in some parts of the country Liver flukes and Lungworms. In crias, we are concerned about Cryptosporidium, Giardia and Coccidians. This article will concentrate on adult type parasites.

 

There are many different Strongyle parasites and in a regular fecal floatation, the many different types can not be differentiated (with a few exceptions) and are referred to as Strongyle type of parasites. The major parasites found in the third compartment (C3 or true stomach) are Haemonchus, Trichostrongylus, Ostertagia, and three that are like Ostertagia: Camelostrongylus, Teladorsagia and Marshallagia. Small intestinal worms are Cooperia, Nematodirus, Trichostrongylus, Lamanema and Tapeworms. These parasites do not cause diarrhea, but rather weight loss, ill thrift and low protein. Many parasites are variable egg shedders; one egg found in a fecal exam may represent a significant problem. Haemonchus is known for causing severe anemia and protein loss if the infection is significant.

 

Whipworms, Capillaria, and Oesophagostomum are found in the cecum and large intestine. Whipwormsand Capillaria are not commonly found in fecal analysis due in part to adult parasites shedding eggs intermittently and the eggs do not float very well unless saturated sugar solution is used. Both are clinically important and resistant to treatment. The larvae initially penetrates the small intestine where they mature, then the larvae migrates to the cecum and large intestine and become adults. The adults tunnel into the intestinal mucosa traumatizing vessels causing enteritis and diarrhea.

 

Camelids are susceptible to several species of liver flukes with Fasciola hepatica and F. magna being the most important in the U.S., particularly in the Pacific Northwest. These parasites can cause an ill-thrift syndrome characterized by low protein and changes in blood work that indicates liver disease with specific increases in GGT concentration and Bilirubin.

 

Whether or not Tapeworms can cause significant disease is controversial in some circles. They also are a parasite egg not frequently found in a routine fecal float. With increasing parasite load the eggs can be found more readily, especially when using saturated sugar solution and centrifugation method. What most owners notice are those pesky looking pieces of “rice” in the dung pile – or even on occasion some very long strands of white “string”. The Tapeworm (Moniezia) of ruminants is a very long worm (2 meters or more) and are passed to alpacas when they ingest contaminated forage mites. Infection tends to be one of young alpacas (weanling to yearlings) taking 6 weeks to develop to adult parasites within the alpaca with the adult worm living for approximately 3 months. Although rare, I have seen them cause clinical disease, even death from impaction in one instance.

 

There are several types of Eimeria species or Coccidia that can infect Camelids. These are species specific parasites with differing degree of pathogenicity. Eimeria lamae is considered to be the most pathogenic of the smaller coccidia, with Eimeria alpacae being the least pathogenic. Eimeria macusaniensis (E. mac)is the largest, slowest maturing and most significant of the coccidian parasites. For simplicity I refer to E. alpacae as small coccidia, E. lamae as medium coccidia and E. mac as large coccidia.

 

E. mac was first reported in the United States in 1988. Like other Coccidian type parasites, it is species specific infecting alpacas as well as llamas (guanacos and vicunas). There are many differences from “regular” (small and medium) coccidia. E. mac takes longer than other coccidia for the infection to mature in the animal (time until you can find the oocyst in a fecal analysis). It also sheds for longer in the feces, greater than 45 days. The youngest it can be seen is about 45 days of age verses 21 days of age for “regular” coccidia. Although we do not currently know how prevalent E. mac is in the U.S., we do know there is widespread concern by camelid owners across the country. E. mac can be seen in all ages, with clinical disease seen more frequently in younger crias and breeding age females traveling to a new farm. If E. mac is present on a farm, herd immunity will develop in adults; leaving the younger animals the most susceptible to infection and disease. It will also expose naïve animals (never exposed to E. mac before) that are new to the farm to infection with E. mac. These naïve animals should be monitored closely as serious disease (even fatalities) can occur before any clinical signs are seen. This is the primary (justified) cause of concern of camelid owners. Further complications are that clinical signs can range from no signs to severe diarrhea. Any animal that shows signs of ill thrift, weight loss, and/or diarrhea should be evaluated by your veterinarian. The first step is to run a proper fecal analysis (centrifugation using saturated sugar solution) and to determine if the protein and albumin concentrations are decreased. If you are suspicious of E. mac infection and the fecal is negative, but the protein and albumin concentration is low it is advisable to treat with Ponazuril anyway. Several factors however are encouraging, one is that immunity does appear to develop in both individuals and the herd and another is that like other coccidian parasites, healthy adults can have incidental findings of E. mac oocysts in their feces without ill effects (in my experience).

Although no formal research has been done on the best way to treat E. mac we know that Sulfas and Amprolium (Corid®) only are only effective in the earliest stages of the infection. These stages are generally already past when the oocysts are found in feces. Another drug, Ponazuril (Marquis®), used to treat an equine protozoal spinal parasite, has also been used to treat E. mac. The advantage of this drug is that it is effective in the later stages of the infection. Because Ponazuril is made for horses, it is too concentrated to use on alpacas as it is made. It is very water soluble and can easily be diluted. Measure out 40 grams of Ponazuril paste, using a gram scale, and then add distill water till the total weight is 60 grams and mix well; this results in a concentration of 100 mg/mL. Of this dilution, give 9 mg/lb (which equals 9 mL per 100 lbs), orally for 3 days. Since the equine paste has carrier as well as drug, this regimen should allow enough of the drug to given to be effective. Regardless of what drug is used, it is important to keep in mind that nothing stops shedding of the final stage of the parasite in feces. The importance of treating animals with clinical disease is to reduce survival of the multiplying stages of the parasite and resultant damage to the intestines.

 

Proper monitoring of internal parasites in Camelids can be challenging, especially in larger herds. Ideally a fecal exam should be done on each animal before any de-worming drugs are administered; this can be impractical in a large herd. In small herds (≤ 10 animals) all animals should be tested, in a large herd 10% of the animals or at least 10 animals should be tested. If there are several Barns, then choose 2 to 3 from each Barn with the total equaling 10 (or more if feasible). When deciding which animals to choose, pick from a variety of ages and target the ones with the lowest Body Condition Score (BCS). This should be done a minimum of two times a year. In addition, it is a good idea to perform a fecal exam on every female immediately after giving birth as her immune system is at its lowest. Another opportune time would be to test crias a few weeks after weaning. Using this information a tailored de-worming program can be designed for any size herd.

 

For this information to be meaningful, the correct procedure should be used. There are many different techniques and variations written about. A recent article¹ compared several techniques and floatation times. The conclusion was that the centrifugation-floatation technique, using concentrated sugar (specific gravity = 1.27) and a 60 minute floatation time was superior in detecting the parasites that have the potential for causing problems in Camelids.

 

In addition there are techniques to give a general idea of number of parasite eggs present or a specific number of eggs present per volume of feces. The latter is preferred and this technique is called eggs per gram (EPG). Please request this method when discussing the type of fecal exam needed with your veterinarian.

 

When discussing the results of fecal analysis, it is important to know how the numbers were obtained and what they mean. After proper preparation of the sample, each parasite egg seen on the slide is counted. As indicated previous, almost all Strongyle type parasites look very similar and are counted as a group. Nematodirus (a type of Strongyle) is a very unique egg and can and should be counted separately, especially as in some cases very low numbers of this parasite can represent a problem. Other distinctive eggs that should be counted separately are Whipworms, Capillaria, Tapeworms, and most Coccidians (especially the medium and large).

 

A frequently asked question is at what EPG should I de-worm my alpaca? There is not a simple answer to that question, even veterinarians cannot agree on the number! Two factors need to be taken into consideration. The first is which types of parasite eggs are found and the second is the BCS of the alpaca being tested. What is agreed upon is that if a fecal analysis reveals a significant EPG count, and the animal in question has a poor BCS, then the animal should be de-wormed. Conversely if a routine fecal analysis shows a “normal” amount of Strongyle type eggs in an alpaca that has a good BCS, de-worming is not needed or even desired. The big question is what is “normal” and what is “significant”? Truly it is a question without a definitive answer and you should work with your veterinarian to determine what is important for your herd. General guidelines for individual farms can be made after a series of fecal analysis over a period of time. If most of the time the results on your farm are less than 200 EPG of Strongyle type eggs then the de-wormer being used is still effective. If that number starts to climb, then you may have the start of a problem. The EPG number is lower when considering parasites such asWhipworms, Capillaria, Nematodirus and E. mac. It is very important to keep in mind treating the herd verses an individual animal. If you have an alpaca with a poor BCS, diarrhea, anemia and/or low protein, finding even 200 EPG of Strongyle type or 5 to 10 EPG (or less) of Whipworm, Capillaria, Nematodirus and/or E. mac will warrant treatment.

 

Many thought processes will need to be changed in the face of information learned by parasitologist and veterinarians over the last few years. One of the more major concepts to be changed is that alpaca owners are notorious for wanting to always have a negative fecal result in the animal being tested. Another is the desire to “rotate” drugs with each treatment.

 

Always having a negative fecal is a dangerous concept as it encourages the development of resistant parasites and it lowers the individual animals’ immunity to parasite infection. Due to the development of resistance to current drugs used to de-worm, the strategies used to treat our animals must change. For many years parasitologist and veterinarians have recommended that all animals in a herd should be treated with a de-worming drug at the same time. This concept has proven unsustainable year after year. We are seeing that despite the supposed “cleaning” up of all the animals on a farm, there is still development of resistant parasites. The current approach is to selectively choose to treat only animals in need of treatment. This will leave a population of parasites that have not been exposed to specific drugs and will help prevent selection for resistance (term used by parasitologist is refugia). This will also take into consideration that 20 – 30% of animal’s harbor 80% of the worms.²

 

What does this mean for the alpaca owner? Using the guidelines presented earlier, test your animals. As it is not practical to test everyone, you will have to use BCS to decide which animals to treat. The whole herd should be evaluated (preferably by the same person each time) and a chart of BCS kept. Initially treat the animals with low BCS or any alpaca that seems to be underweight for age and size. As this process continues, any animal that has a negative change in BCS should be treated (and tested). A list should be kept of those treated and if a positive weight/BCS gain in thin animals is not seen, an individual fecal in those animals should be done. It is important to also check mucous membrane color (gums, sclera, vulva) when checking BCS to determine if anemic (pale mucous membranes). Keeping in mind that thin animals with parasites may have other concurrent problems so additional testing may be necessary. Specifically, have your veterinarian perform a Complete Blood Count (CBC + PCV) to check for anemia and a Chemistry analysis to assess liver and kidney function. Further testing may be necessary in certain situations.

 

Rotation of drugs unfortunately does not include the use of Avermectins (Ivermectin, Dectomax) due to the presence of Parelaphostrongylus tenuis (Meningeal worm) in the Eastern United States (anywhere white tail deer are found). These drugs are still the mainstay we must use to prevent infection. Also unfortunately due to the overuse of these drugs, many of the parasites (not the Meningeal worm) have developed irreversible resistance to these drugs. In the Southern United States, this problem is very severe. De-wormers with new mechanisms of action are 5 to 7 years away from being developed in the US, so it is important to change our way of thinking.

 

There are 3 classes of anthelmintics in use today with small ruminants: 1) Benzimidazoles (Panacur, Valbazen), 2) Cholinergic agonists (Levamisole), and 3) Avermectins, Milbemycins (Cydectin). None of these drugs are labeled for use in camelids, so the specific doses and frequency of administration are unknown. Several of these drugs have very narrow ranges of safety. Panacur has a very wide margin of safety, whereas Valbazen and Levamisole have a very narrow safety margin. The choice of which product to use is the big question. The best choice is to use the oldest class of drugs that still results in a 90% reduction of parasite eggs found in a fecal floatation. The only way to test this is to have a fecal analysis done before any de-worming is done and to repeat (on the same animal) the fecal analysis in 14 days. If you have the room to change pastures after de-worming, wait for 4 to 5 days after the last dose of drug is given. It is also recommended that when using oral products to withhold food overnight. This slows the flow of gastrointestinal contents and allows an increase in the time the drug is in contact with the parasite. Another way to increase the efficacy of a drug that seems to be losing its potency is to repeat dosing 12 hours apart, this will also increases the duration of contact between drug and parasite (works best with Benzimidazoles). The dosing information provided should be reviewed with your veterinarian when you are considering which de-worming product to use. These are the drugs most commonly used as dewormers, other drugs may have been used in camelids, check with your veterinarian for safety.

 

 

It must be remembered that use of chemicals to control parasites is only one step in an attempt to limit parasite infection in our alpacas. Other factors such as herd density, feeding practices (always feed hay off the ground), climate, age of animal, overall health of the herd, type of soil and the actual parasites already present in the animal/environment must be taken into consideration. With so many variables, developing a proper de-worming program for your herd will not happen over night. It will take some careful thought by you and your veterinarian and a willingness to make decisions that at first seem contrary to what “you have always done”.

 

1. Comparison of methods to detect gastrointestinal parasites in llamas and alpacas. Cebra C, Stang B. JAVMA 2008; 232 (5):733-741.

2. Anthelmintic Resistance of Gastrointestinal Parasites in Small Ruminants. Fleming S, Craig T, Kaplan R, et al. J Vet Intern Med 2006;20:435-444.