E Mac
Eimeria macusaniensis - A form of coccidia


E mac


By Dr. Chris Cebra, Oregon State University

     I am writing this editorial to describe Eimeria macusaniensis infection, which I believe to be one of the most important emerging diseases in camelids. The causative organism is the largest of the camelid coccidia, 100 microns in length, thick-walled, and watermelon seed-shaped. It has longer prepatent (32 to 43 days) and patent (up to 40 days) periods than other species of coccidia, and also is as commonly associated with disease and death in adults as in crias. It is not a new organism. Dr. Jarvinen's work from 1999 suggested that it was present in most herds, and my recent experiences support that. It is "emerging" because of greater awareness, better detection methods, and possibly higher case attack rates. It is my belief that the extreme environmental stability of this organism has allowed it to build up over the 20+ years of popular camelid farming in the U.S., and that together with certain management practices including overcrowding, co-housing of crias and adults, overuse of certain pastures, and mixing stressed camelids from different locations, has lead to a real increase in clinical cases.

     Eimeria macusaniensis follows the typical coccidian lifecycle, requiring 13 to 21 days on the ground for oocysts to sporulate, having multiple rounds of replication within the host, and primarily damaging the intestinal epithelium. The severity of clinical disease relates to host immunity and infective dose.  Lightly infected, immunocompetent camelids may transiently shed small numbers of organisms, but will show no signs. Immunocompromised or immunonaive camelids, such as stressed adults or all crias, confronted with a large or overwhelming dose, may succumb to fatal disease in as little as 3 weeks, or as long as 2 weeks before oocysts appear in the feces. Adults within an infected herd appear to be less susceptible than ones introduced later, for example for breeding. The major signs of severe disease are those of weakness and wasting. Unless the camelid is weighed frequently, the owner frequently notices nothing wrong until the camelid collapses. Diarrhea is uncommon, except in crias. Hypoproteinemia is the major blood abnormality. Clinical abnormalities will be more comprehensively described in a soon-to-appear scientific report.

     The combination of lack of specific GI signs and a negative fecal examination makes the infection easy to miss. We consider all ill-thrift camelids to be suspect, and either treat empirically or perform multiple fecal examinations over at least a 2 week period.  Even then, shedding is often light (<100 oocysts/g) for the first week of patency, even in camelids with overwhelming infections. Considering that most of the anticoccidial medications available in the U.S. are most efficacious against the earlier stages of the organism, delaying treatment in suspect camelids is unlikely to be advantageous. It is more difficult to decide what to do with non-clinical shedders and their herdmates. As with other internal parasites, in general we acknowledge their presence and try to control them, not eliminate them. The long prepatent period, together with the pelleted camelid feces, offers the potential for timely manure removal to decrease pasture contamination. We believe the thick wall of the organisms imparts extreme environmental resistance, so leaving paddocks and pastures empty is of less benefit than with other GI parasites. Radical soil treatments including burning and topsoil removal have been tried, but such approaches should only be considered in extreme circumstances. As with other parasites, a good management approach decreasing stocking density, avoiding admixtures of stressed camelids, encouraging eating from above-ground feeders, avoiding excess cohabitation of crias and adults, conducting fecal parasite surveillance, timely antiparasitical treatments, and frequently checking demeanor and body condition of camelids should decrease the number of affected camelids and allow early identification of those that require treatment.

     I have only lightly addressed fecal detection. This will also be the subject of an upcoming scientific report. The high density of the oocyst makes it more likely to float in denser float solutions and also slower to rise. The low numbers at the onset of patency dictate that very sensitive techniques should be used. These factors should be considered when choosing the method of fecal analysis. 

Primary Reference:
Cebra CK, Valentine BA, Schlipf Jr. JW, Bildfell RJ,
McKenzie E, Waitt LH, Heidel JR, Cooper BJ, Lohr CV,
Bird KE, Saulez MN, Firshman AM. "Eimeria
macusaniensis infection in 15 llamas and 34 alpacas". 
J Am Vet Med Assoc. 2007 Jan 1;230(1):94-100.

Reprinted from Wool & Wattles: The AASRP Newsletter,
vol. 34, #4; pp. 10-11, Oct.-Dec. 2006 with
permission from Dr. Chris Cebra and the American
Assoc. of Small Ruminant Practitioners. Permission to
reprint this article is granted to participants in the
Newsletter Exchange.


From Camelid Healthcare Services:

Eimeria Macusaniensis (E.mac) is a coccidian parasite that can cause severe illness. E. mac is called a “large coccidia” because its oocyst (egg) is very large compared to the other coccidia of llamas and alpacas. E. mac, like the other “small’ coccidia is a protozoan parasite that lives in the intestinal tract. This parasite causes damage to the lining of the intestine and inhibits normal absorption of nutrients and causes fluid to be secreted from the damaged intestinal wall. This results in diarrhea, weight loss and low blood protein levels. 

E. mac is a common parasite of many alpacas and most farms will have some positive animals. A low number of E. mac found on a routine fecal exam is not cause for alarm—but something that should be noted. Most researchers would agree that a low level exposure to parasites results in some protective immunity and is desirable. Health problems occur when an animal is exposed to an overwhelming load of parasites or if exposure occurs when the animal’s natural defenses are low. This may occur if a cria failed to get a good passive transfer of colostrum, during show season or with travel to a new farm.

Diagnosis of illness caused by E. mac can be difficult because of the long pre-patent period. This pre-patent period is the time from infection (and damage to the intestinal wall) till the time the oocysts appear in the feces. Finding the oocysts in the fecal exam and clinical disease are the criteria that we use to establish the diagnosis. E. mac will have a pre-patent period of 35-43 days—so the animal can have damage to the intestine and we can not prove it is caused by E. mac because the fecal exam is negative.

Many times treatment for E. mac is started based on farm history of E.mac being present, clinical signs of diarrhea and low blood proteins on examination of blood work.
Treatment of E. mac can be accomplished with Corid, sulfa drugs or a new product called Marquis. Consult with your veterinarian for best treatment for your particular situation.


By Jill McElderry-Maxwell, Bag End Suri Alpacas of ME, LLC (2010)
(Editor’s Note: The author explains that she is not a veterinarian, and her intent with the article was to pull together the research available on the topic so that individuals could make informed decisions about their parasite management programs.)

INTRODUCTION: Coccidia are microscopic parasites that disrupt intestinal function. Although they are diagnosed on fecal examination, they are not worms. Instead, they are single celled organisms known as protists. Protists are obligate intracellular parasites – they must complete part of their life cycle in the cells of a host organism. Coccidia are widespread organisms that affect not only alpacas, but almost every group of animals known. They are ubiquitous in the environment, and naturally infect most animals to some degree. Problems arise when their numbers exceed the ability of their host to carry them without suffering negative consequences.

There are numerous coccidia of veterinary significance, including Eimeria, Cryptosporidium, Plasmodium, and Toxoplasma. The following species of Eimeria coccidia have been identified in New World camelids: Eimeria alpacae, Eimeria lamae, Eimeria punoensis, Eimeria peruviana, Eimeria ivitaensis and Eimeria macusaniensis [Duzynski, et al., 1998a]. The first four species are typically grouped together as “small coccidia.” Little information is available on E. ivitaensis, although this is apparently a large coccidian. It is unclear from my research whether this coccidian has been found in camelids living in North America.

This article deals with the large coccidian Eimeria macusaniensis, commonly known as E. mac or “Big Mac.” E. mac was first described in South America in 1971 [Guerrero, et al., 1971] and was widely identified in the North American herd by 1999 [Jarvinen, 1999]. Dr. Jarvinen’s work with midwestern farms in the late 1990s showed that almost a third had E. mac present, with approximately 10% of all animals tested carrying the parasite. Eimeria macusaniensis is difficult to detect on fecal flotation, and sheds very infrequently; it also causes fewer clinical symptoms than small coccidia (i.e., diarrhea is not frequently associated with E. mac). Thus, a farm may have infected animals without ever diagnosing the parasite, despite fecal examination.

Dr. Cebra believes that the apparent recent surge in E. mac reports represents both an actual increase in numbers of animals infected, as well as more accurate reporting of infection due to better fecal sampling and owner awareness [Cebra, 2007]. Given the frequent movement of alpacas across country and their admixture, it may have been inevitable that “Big Mac” would spread across the country and eventually reach significant levels in previously naive populations.

LIFE CYCLE [Duzynski, et al., 1998b]
Coccidia are present in the environment as oocysts, roughly equivalent to the egg stage of other parasites. The oocysts are usually passed from the host in the feces, and this is the form by which almost all coccidia are known and identified. Eimeria macusaniensis is distinct from the “small coccidia” by virtue of its large size (~90 microns versus ~30 microns) and piriform shape. Oocysts do not become infective unless environmental conditions are appropriate, at which point sporocysts containing sporozoites develop. The encapsulated oocyst is then referred to as a sporulated oocyst, and it can persist in the environment in this stage for years. The thick walls of sporulated E. mac make this organism virtually impervious to environmental extremes and it can persist in the soil for years. Some owners have resorted to extreme means to attempt to destroy E. mac oocysts in their fields, including topsoil removal and burning, but these measures are neither effective [Cebra, 2007], nor likely to be warranted.

Once a sporulated oocyst is ingested by a host, the covering of the oocyst is broken down either by mechanical or chemical activity in the host’s gut. After release, the sporozoites seek out and penetrate epithelial cells lining the gut. Inside the host’s cells, the sporozoites begin to multiply asexually into merozoites. The proliferation of merozoites eventually bursts the host cell, and the released merozoites begin seeking out new cells in which to begin the process of multiplication again.

Each species of coccidian is believed to have a specific number of asexual replication cycles that it completes. The final generation of sporozoites again seek out new host cells, but instead of making more sporozoites by fission, they develop into two types of gamonts: large, sessile macrogamonts (analogous to eggs) and smaller microgametocytes, which produce motile microgametes (analogous to sperm). When a macro- and microgamete fuse, a protective wall develops around the resulting zygote, which pushes free of the host cell and is excreted in the feces [Duzynski, et al., 1998b].

The prepatent period, the time between ingestion of a sporulated oocyst and passing oocysts in the feces, varies from species to species of coccidia. The prepatent period for the two most common small coccidia in alpacas are ten days for E. punoensis and 16-18 for E. alpacae [Foreyt, 1992]. Eimeria macusaniensis is unusual in that its prepatent period is 33-42 days, meaning than an animal can be infected for over a month before any trace of the parasite is evident in the animal’s feces. This unfortunately means that an animal may sustain considerable damage or even die from the activity of the parasite before there is any means of detecting the infestation.

Oocysts are known to sporulate more quickly at higher temperatures than lower, within the range of 50°F t o 122° F. Unsporulated oocysts do not survive outside of these temperature extremes, although sporulated oocysts can. Oocysts require moisture, oxygen and shade to sporulate. Direct exposure to sunlight will kill unsporulated oocysts [Duzynski, et al., 1998b]. Once sporulated, oocysts remain infective for anywhere from several weeks to several years in the natural environment, depending on species. Eimeria macusaniensis requires 13-21 days to sporulate [Cebra, et al., 2007].

In essence, coccidia thrive in damp, dark locations at moderate temperatures – accumulated dung and bedding that do not dry out are a haven for coccidia growth. You can limit your animals’ chances at (re)infection in several ways. Good manure management is important: remove manure from animal living areas regularly and consider allowing free range poultry to turn over your manure piles, since exposing the oocysts to sunlight prior to sporulating will kill them. The lengthy time period reqjuired for E. mac to sporulate means that prompt manure removal can be very beneficial in reducing the number of infective oocysts present in your animals’ environment.

The better overall health your animals are in, the better able they are to resist infection and mitigate the effects of all coccidia, including E. mac. Keeping stocking rates low and removing stressors from your animals’ environment will promote good health and reduce the effects of coccidia. A good plane of nutrition also permits an animal to carry a coccidia load without significant ill effects. Over time, alpacas will build immunity to the coccidia to which they have been repeatedly exposed, which is why clinical cases of coccidiosis are usually seen in young alpacas or older animals with compromised immune systems.

The same holds true for E. mac, although this species can be more virulent than the small coccidia, particularly in cria. However, it is entirely possible for an animal to carry subclinical loads of Eimeria macusaniensis and remain in good health. Although E. mac was initially viewed by many as a virtual death sentence, the emerging consensus among camelid veterinarians is that E. mac should be managed in the same way as small coccidia, but with greater vigilance [Cebra, et al., 2007]. Cria are particularly susceptible, and once an owner is aware of E. mac on their property, the parasite must be considered in any animal showing signs of ill thrift.

Coccidiosis caused by the “small coccidia” typically shows a clumped or ball stool in mild cases, progressing to diarrhea and weight loss in more severe infestations. In very severe infestations, portions of the intestinal lining may be shed, and the damage to the intestinal wall can be permanent, causing continued ill thrift or stunted growth. Eimeria macusaniensis is atypical in that diarrhea is not usually associated with even heavy loads of the parasite. Weight loss and weakness are symptoms of infection, but obviously are not diagnostic for E. mac alone. Bloodwork from an infected animal will reveal hypoproteinemia (low protein levels), but this is also not specific to E. mac infection.

E. mac oocysts are large and heavy, and can be easily overlooked in a fecal with a short float time, or one that is not centrifuged. Eimeria macusaniensis also sheds very few eggs (estimated at fewer than 100 in the first week of patency [Cebra, 2007]), so infrequent fecals are unlikely to find the parasite. If E. mac is suspected, multiple fecal examinations over a several week period, using centrifugation and a saturated sugar solution, are recommended as the best way to try to catch oocysts as they are shed.

Animals with known or suspected E. mac can be treated in two different ways: with a coccidiostat that prevents additional reproduction of the coccidia, or with a coccidiocide, which kills the organisms outright. Coccidiostats include amprolium (Corid), which inhibits thiamine uptake in coccidia; sulfadimethoxine (Albon), which prevents the uptake of folic acid; and sulfamethoxazole/trimethoprim (SMZ-TMP), which also prevents the uptake of folic acid.

Without access to thiamine or folic acid, coccidia are unable to continue reproduction, and the alpaca’s immune system will clear the remaining organisms on its own. Although dosages and protocols vary, most coccidiostats are used on an on-off-on rotation over several weeks. It is important to note that alpacas are very susceptible to thiamine depletion, much more so than other ruminants. Thiamine depletion results in polioencephalomalacia (PEM), characterized by swelling in the brain, which can be fatal. Symptoms include lack of appetite, poor coordination and other neurological signs. High doses of injected thiamine can reverse PEM.

For this reason, if using amprolium to treat coccidiosis, it is recommended that you concurrently administer thiamine subcutaneously every third day during treatment. It may seem counterintuitive to administer thiamine when amprolium works by blocking access to thiamine (the coccidia preferentially uptake the amprolium in place of thiamine). However, the injected thiamine is available to the alpaca’s metabolism, but does not reach the gut where the coccidia are.

Another important consideration when using coccidiostats in cases of known or suspected Eimeria macusaniensis is that coccidiostats are most effective against the first stages of a coccidial infection. Given the long prepatent period of E. mac, these stages may be past by the time treatment is begun. For this reason, a coccidiocide may be preferable. Two coccidiocides are currently recommended for the treatment of E. mac, ponazuril and toltrazuril.

Ponazuril (Marquis) is a medication originally developed to fight a protozoan in horses. It is effective against later stages of coccidial infection. The medication is very expensive and requires careful dilution to an effective dosage for alpacas (40 gm ponazuril paste plus 60 gm distilled water to equal 100 gm; dosed at 9mg/lb once diluted). While equine veterinarians stock the drug in many areas of the country, it may not be available except by mail order in others. It must be administered for three days.

Toltrazuril (Baycox) is a relatively new treatment for cocciodiosis. It is a coccidiocide, which kills the intracellular life stages of coccidia. It must be imported from Australia, and is available in this country from Light Livestock Equipment (www.lightlivestockequipment.com) or can be ordered directly from Australian sources. Many farms have reported success with single treatments, while others indicate that two doses several days apart are more effective.

 You should consult with your veterinarian to see which medication is recommended for your particular situation. In mild cases of clinical coccidiosis, coccidiostats may be preferred, as they do permit the animal to mount its own immune response to the nonreproductive coccidia. This will reduce the likelihood of future reinfection. In severe cases, where immediate relief from severe infection is required, a coccidiocide’s action may be more appropriate. It is important that the alpaca community refrain from overusing toltrazuril and ponazuril, in order to maintain their effectiveness for the future.

Proper hygiene and good husbandry to prevent coccidiosis are preferable to chemical intervention. Well cared for animals will typically develop an immunity to coccidia – including Eimeria macusaniensis. E. mac is now a widespread part of the parasite community affecting North American camelids, just as are the small coccidia. With proper management of your herd, the effects of this parasite on your own herd, as well as that of others, can be minimized. Proper quarantine and fecal testing of incoming and outgoing animals should take into consideration the longer prepatent period and low shedding rate of this organism, and animals should remain in quarantine for an appropriate duration.

Cebra, C. K,. et al, “Eimeria macusaniensis infection in 15 llamas and 34 alpacas,” J Am Vet Med Assoc, 230(1), 2007, pp. 94-100
Duzynski, D.W. et al., “The Coccidia of Camlidae,” 1998a, NSF-PEET DEB 9521687, available as an on-line reference at http://biology.unm.edu/biology/coccidia/ artiodact2.html
Duzynski, D.W. et al., “Biology of the Eimeriidae,” available as an on-line reference at http://biology.unm. edu/biology/coccidia/eimeriabiol.html
Guerrero, Carlos at al., “Eimeria macusaniensis n. sp. (Protozoa:Eimeriidae) of the alpaca (Lama pacos),” Journal of Eukaryotic Microbiology, 18(1), 1971, pp. 162- 163
Jarvinen, J.A., “Prevalence of Eimeria macusaniensis (Apicomplexa:Eimeriidae) in Midwestern Lama spp.,” Journal of Parasitology, 85(2), 1999, pp. 373-376
Jarvinen, J.A., “Infection of Llamas with Stored Eimeria macusaniensis Oocysts Obtained From Guanaco and Alpaca Feces,” Journal of Parasitology, 94(4), 2008, pp. 969-972
Johnson, Amy et al., “Diagnosis and treatment of Eimeria macusaniensis in an adult alpaca with signs of colic,” The Veterinary Journal, 179(3), 2009, pp. 465-467
Palacios, C. A., et al., “Eimeria macusaniensis and Eimeria ivitaensis co-infection in fatal cases of diarrhoea in young alpacas (Lama pacos) in Peru,” Vet Rec., 158 (10), 2006, p. 344
Walker, Pam, “Gastrointestinal Parasites in Alpacas,” available online at

Parasite Management in Camelids by Stacey Byers, DVM, MS, Dipl ACVIM

I. PROTOZOA A.    Coccidia (Eimeria alpacae, E. lamae, E. macusaniensis, E. punoensis)
This parasite typically causes diarrhea and weight loss or lack of gain in crias and naïve (previously unexposed) or immunosuppressed adults. There is no cross protection between species so adults can be infected and develop clinical disease from a different species. Treatment is typically only recommended if oocyst (egg) counts are significantly high with the presence of diarrhea. However if E. macusaniensis is suspected, treatment is often started regardless of finding oocysts in the feces since the parasite can cause significant intestinal damage.

Infection occurs by oral exposure can occur in as little as 4 days if oocysts are exposed to cool, moist conditions. Pasture management is key to reduce exposure. The oocysts die in warm, dry pasture in 20-30 days but can persist for years in cool, damp environments. The prepatent period (time from ingestion of the oocyst to shedding in feces) is variable among species but ranges from 10 days for E. punoensis to over 40 days for E. macusaniensis.

Oocysts cause diarrhea by damaging intestinal cells. After the anthelmintic treatment is finished, feces may remain loose until the intestinal lining is repaired. In severe infections, stunting or ill-thrift with continued diarrhea may occur due to permanent damage to the intestinal lining.