GI Parasites and Worms in Camelids, an Overview
Stacey Byers, DVM, MS, DiplACVIM
Colorado State University Veterinary Teaching Hospital
Camelids can be infected with many different parasites and these include gastrointestinal (GI), external (ticks, mites, etc), and a cria. This is only a partial joke since many heavy lactation females can look like they have a parasite problem but their poorer body condition is just due to milk production. This first part of a two-part article will be focusing on the GI parasites commonly affecting camelids, clinical signs of infection, and life cycle features that we can use for detection. Treatment and control strategies will be discussed in Part 2.
Why are we seeing more GI parasite problems in certain regions of the West? It is primarily due to the weather. Some areas have had significantly more rainfall or rain in normally dry times and winter has not helped in other areas since it has been warmer than normal rather than a long duration cold spell. These two factors – the moisture and temperatures – have favored the GI parasites. Environmental conditions have not been that harsh (hot and dry or frigid) to kill off the eggs in the pastures and pens. The eggs have always been around but were being inactivated by the weather conditions. The parasite eggs are shed in the feces of the animals in your herd.
The camelid dung pile is a great parasite control method compared to what owners have to do when keeping sheep and goats since they drop fecal pellets in random fashion. However the dung pile is not foolproof. Juveniles or other animals may not be that fastidious at using it if they are suffering from diarrhea and have the “urge to go now”. Also animals get feces on their feet, these can tracked around and lead to eggs being deposited in a variety of areas. Then we get a little water and warmth and voilà, the parasites can complete their life cycle and become infectious.
Most of the time we see GI parasite problems in our juvenile camelids. These juveniles are under more stress (psychological, immunological, physical, etc.) than adults, except for pregnant animals. The first time the animal is infected, their immune system is not prepared (naive) and it takes time for the immune cells to develop to fight the parasite (or bacteria, virus, etc.). This naiveté provides the parasites time to complete their life cycle leading to intestinal damage and cause the diarrhea, poor growth or weight loss, poor fiber, lethargy, etc. that we see. Older animals can have similar parasite problems because their immune system is not as robust as in younger adults. This is similar to the increased risk of influenza and pneumonia in elderly humans.
The severity of signs from GI parasites is usually dependent on the infectious dose the animal gets, therefore infection with a larger number of parasites results in more serious disease. Once the immune system has “seen” the parasites the first time, it is more prepared for the next exposure cycle and often can keep the infection in check without clinical signs developing. The duration of protection varies with types of parasites and time between exposures.
Additionally when we have years of low parasite loads on the pastures, the lack of continued low level immune stimulation can lead to a flare up of parasitism in any age camelid. The beneficial aspect of low level immune stimulation is one reason we no longer recommend routine, whole herd deworming when there are no signs of parasite infections or just small numbers of parasite detected on fecal examinations.
As a review there are several categories of GI parasites: nematodes, cestodes, and protozoa.
- Nematodes are sometimes called “worms”, and some of the more common ones found in camelids are Haemonchus, Trichostrongylus, Nematodirus, and Trichuris Haemonchus and Trichostrongylus are often lumped into the general category of “strongyles” since the eggs look identical.
- Cestodes are tapeworms and include Taenia and Moniezia
- The final category is the protozoa which includes coccidia (Eimeria species including macusaniensis), Cryptosporidium, and Giardia.
The GI parasites found in your particular region vary by environmental conditions, animal stocking density, previous biosecurity protocols a farm may have implemented, as well as other factors. All farms should assume to have coccidia, Nematodirus, and some version of strongyles. These may not show up in every fecal floatation performed, however, they are too common and impossible to eradicate completely from the environment and the animals (more in Part 2).
The different GI parasites have some unique features we need to discuss in more detail.
- Haemonchus and Trichostrongylus – Under optimal conditions of high temperature and humidity, the eggs from these worms can mature to infective larvae stages in approximately one week. The larvae require moisture and grass or spilled hay to wiggle on to in order to live long enough to be consumed by an animal. Once ingested, the larvae require 2-4 weeks to mature to the egg-laying adult stage (prepatent period) and then we can detect the eggs on fecal examinations. Adult Haemonchus attach to the Compartment 3 (C3) mucosa and feed on blood.
The signs of a severe infection are a reflection of this blood loss. The anemia from the blood loss shows as lethargy or exercise intolerance (e.g. lagging behind the group), increased respiratory rate and possible nostril flaring, increased heart rate, and pale mucous membranes and sclera. This can look like a Mycoplasma haemolamae infection. In “pure” Haemonchus infections, the host usually has well-formed feces because blood loss is the main problem, not impaired digestion. Trichostrongylus infections appear to have some variable geographical differences in severity of infection and disease. For example, camelids in the Northwest coastal areas of the US can have significant infections with this parasite.
- Nematodirus – The parasite is a low egg shedder so the presence of multiple eggs on a fecal floatation indicates a significant infectious load. The eggs can remain dormant for over a year on a pasture and hatch into infective larvae when optimal weather conditions exist. Once ingested, it takes 2-3 weeks before we can detect the eggs in a fecal examination. Alpacas often show signs of mild-moderate abdominal pain (colic) with Nematodirus
- Trichuris – This parasite is often called a “whipworm” because the adult form looks like a whip. Trichuris infections seem to have some variable geographical differences. The prepatent period is approximately unknown in camelids but 2 months in other ruminants. The eggs are very resistant to environmental degradation.
- Cestodes: Taenia and Moniezia – These are usually more of a concern for an owner than the animal as it can be disturbing to find small “grains of rice” attached to the rump or fiber of the animal. Most of the time tapeworms do not cause problems, however, significant infections can be pathologic and result in diarrhea and ill-thrift.
- Coccidia – There are multiple species of coccidia and all are host species specific so camelids cannot be infected by coccidia from cattle, chickens, etc. Coccidia are often found in fecal floats so treatment is only warranted if clinical signs are apparent or oocysts are seen in very high numbers. Diarrhea can be mild and due to maldigestion and malabsorption of nutrients with low infection loads, but can progress to an inflammatory condition with bloody diarrhea, mucosal shreds and fibrin in the feces with high infectious dosages. In severe infections, animals may strain to defecate and even develop a rectal prolapse from straining.
The oocysts require a minimum of 5 days to transition to the infectious stage and moist warm weather favors this faster time. The oocysts are very hardy hanging out in cool, moist conditions. The prepatent period varies from about 2-5 weeks depending with the individual Eimeria species with E. macusaniensis having the longest prepatent period.
- Cryptosporidium – Oocysts are immediately infective once they pass out in the feces and the infectious dose is very low, therefore infection occurs quite easily. The prepatent period is 3-7 days. Some species of Cryptosporidium can cause disease in animals and humans (zoonotic). The parasite is very difficult to eradicate from the environment so if it is on your premises, assume it is there to stay.
- Giardia –Often Giardia is an incidental finding on fecal examinations, but it can be the primary cause of diarrhea. We usually determine this when the diarrhea does not resolve with normal treatments. Infection typically occurs through contaminated water. Similar to cryptosporidiosis, the infectious dose is quite small and significant fecal shedding occurs in affected animals. Once Giardia is found on a farm, it is assumed that all animals will be infected. The prepatent period is between 3-10 days, and cysts are immediately infective. Some strains of Giardia are also zoonotic.
- General Clinical Features of GI Parasite Infections
Poor or no weight gain, weight loss, poor hair coat
- Colic or intestinal inflammation (enteritis)
- Diarrhea may be profuse and lead to metabolic abnormalities.
- Blood in the feces
- Weakness, lethargy
- Anorexia due to cramping or weakness or just not feeling well.
- Swelling along the bottom of the jaw, chest area, scrotum, prepuce, or udder. The swelling (edema) develops as fluid (similar to water) accumulates into the more ventral subcutaneous tissues. This can occur with severe protein loss from a damaged intestine.
Click here to read Part 2, Treatment and Control Strategies.