Parasite Control
January 2006
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1. What is parasite control and what does it entail?
Parasite control is based on maintaining parasite populations below which
clinical signs are observed. It does not involve the complete elimination of all
parasites from a herd for several reasons. A low level of parasites develops
immunity in the animals, decreases drug resistance, saves money for the owner,
and finally because complete elimination is impossible.
2. How do parasites cause immunity?
An animal exposed to parasites, bacteria, viruses, etc. develops
specialized cells that are used to fight infections from these
foreign organisms. Some produce life long immunity after a single
exposure while others produce immunity for as little as several
months. Low level repeated exposure to a foreign organism can
stimulate the immune system to continue producing the specialized
cells and thereby reduces the severity of infections in the future.
3. Why is drug resistance important?
Drug resistance to anthelmintics (anti-parasite drugs) is
becoming more common. Unfortunately these drugs are unable to
completely eliminate an entire population of parasites. The few that
remain are resistant to the drug and with time reproduce creating a
new population that is also resistant. Anthelmintic resistance is
very common in sheep and goats and increasing in alpacas and llamas.
Resistance is encouraged with indiscriminate use of anthelmintics,
shipping animals, open herds, and inadequate biosecurity.
Anthelmintics should complement but not replace good management and
sanitation practices.
4. How can management and sanitation reduce the need for
anthelmintics?
Management strategies include using feed bunkers and eliminating
standing water and wet areas around waterers to reduce the favorable
environment most parasites need to become infective. Frequent
cleanup of the dung pile and pasture rotation reduces the parasite
load and possible chances of exposure. Quarantine pens for all
incoming animals helps reduce exposure of the existing herd to new
parasite species as well as other diseases. Incoming animals are
stressed from transportation, new surroundings, and removal from
existing herdmates. The stress can cause a mild immunosuppression
causing an increase shedding of parasites or other organisms.
We
suggest that every 2 months a random sample of fecals from
the herd be evaluated to assess parasite control.
Concentrate on 3 general groups: crias in the first 3-4
months of life, yearlings, and adults. A sampling of 3-5
animals or 10% of the group should be adequate.
5. What types of deworming programs are available?
Deworming can be performed on a seasonal basis and/or as needed.
Which you use will vary by your geographical location, open or
closed herd, pasture – dry or irrigated, travel, stocking density,
etc. Periodic fecal sampling (as described above) including fecal
egg counts will provide information as to types and numbers of
parasites present. You should review your particular situation with
your veterinarian and in combination with fecal egg counts determine
the best deworming program for your situation.
A general program for the inland Pacific Northwest would include
twice a year treatments of all animals over 2-3 months old twice a
year. In the fall after a killing frost, animals would be treated
with an ivermectin-type product for intestinal worms, external
parasites, and nose bots. Animals should be treated in the spring
prior to majority of births with a fenbendazole-type product. The
periodic fecal exams would determine if additional dewormings would
be needed.
6. Who to contact for more information?
The following information is a brief overview of the more common
parasites seen in alpacas and llamas and some of the treatments
available. It is strongly recommended that a veterinarian evaluate
if treatment is warranted through examination of the animal or herd,
fecal analyses, and fecal egg counts. Use of anthelmintics should
not exclude good management and pasture sanitation programs.
Not all available anthelmintics are listed below. Use is
“off-label” as none are currently approved for use in alpacas or
llamas.
I. PROTOZOA
A. Coccidia (Eimeria alpacae, E. lamae, E. macusaniensis,
E. punoensis)
A parasite problematic for crias <1 year old 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. Due to developing drug
resistance and the inability to completely eliminate the parasite
from animals, treatment is only recommended if oocyst counts are
significantly high with the presence of diarrhea.
Infection is through the fecal-oral route and can occur in as
little as 4 days if oocysts are exposed in cool, moist pastures.
Pasture management is a key factor to reduce exposure to susceptible
animals. 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 33
days for E. macusaniensis.
Oocysts cause diarrhea by damaging intestinal cells. After
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. Contact your veterinarian if severe
diarrhea occurs since dehydration can rapidly lead to death
especially in warmer weather conditions.
Treatments Available:
Amprolium (Corid®)
5 day treatment or a 21 day prevention program. There are several
formulations available and dosage and delivery vary with each. The
product can be used for treating individual animals or via water
delivery for herd situations. It is best to treat individual animals
in face of outbreak as crias may not drink the water and not all
animals will receive the same dose.
Sulfadimethoxine (Albon®)
Available in both liquid and tablets for individual animal
treatment.
Decoquinate (Deccox®)
A preventative product. Add to feed of pregnant females 1 month
prior to parturition or when moved onto clean pasture prior to
parturition. It can be added to creep feed provided to crias to
reduce oocyst production. If coccidiosis has been a problem in a
herd, decoquinate should be fed to all growing animals on a daily
basis.
B. Cryptosporidium (Cryptosporidium sp.)
Rarely seen but can cause diarrhea in young camelids, especially
less than 30 days old. This is zoonotic so humans can get it too!
Use good hygiene/sanitation since no treatments are available. Keep
the animal dry and well hydrated until the parasite runs its course.
Prepatent period is 3-7 days.
II. NEMATODES (ROUND WORMS)
A. Strongyles (Cooperia, Haemonchus, Oesophagostomum,
Ostertagia, Trichostrongylus)
There are many types of “strongyles” that cannot be
differentiated by egg shape alone. Fortunately the treatment is
similar for all. These parasites can cause stunting, weight loss,
and diarrhea especially in juvenile animals.
B. Whipworms (Trichuris tenuis)
This parasite causes poor growth, diarrhea, and blood loss. It
can severely debilitate crias. This parasite is somewhat resistant
to the ivermectin-type products but the benzimidazoles such as
fenbendazole and albendazole are effective at the high end of the
dose range. This parasite requires 3 weeks in the environment to
become infective and is very difficult to remove once present. The
prepatent period is unknown.
C. Nematodirus battus, N. helvetianus
Nematodirus spp. eggs are approximately 2 times the size of
strongyle eggs. The parasite is a low egg producer so any eggs
present indicates a significant infection and should be treated.
This parasite can cause poor growth and diarrhea especially in
crias.
Use the high end dose range.
D. Parelaphostrongylus tenuis
Commonly called “meningeal worm”. The parasite is found in
white-tailed deer and requires a snail to continue the life cycle.
When camelids and other animals eat an infected snail, the parasite
migrates through the animal and penetrate the spinal cord causing
paralysis 50-60 days after ingestion death soon after. This parasite
is prevalent in the eastern United States but is currently not
present in the western states. Prevention includes deer-proof
fencing, snail-eating fowl, and the use of ivermectin products every
30 days.
Treatments Available:
Benzimidazoles
Increasing parasite resistance to many of these products especially
in sheep and goats and also in areas of the country with favorable
parasite environments.
Products available
Fenbendazole (Panacur®, Safe-guard®)
Albendazole (Valbazen® - not
recommended in pregnant animals)
Avermectins
Effective against many internal and external parasites. Reduced
efficacy with Trichuris.
Products available in oral or injectable forms
Ivermectin (Ivomec® and many others)
Doramectin (Dectomax®)
Moxidectin (Cydectin®, Quest®)
Levamisole (Levasole®, Tramisol®)
Not recommended in lactating animals.
Pyrantel-Pamoate (Strongid-T®)
III. CESTODES (TAPEWORMS) Cestodes are rare in camelids at
this time.
IV. TREMATODES (LIVER FLUKES)
A. Fasciola hepatica, Fascioloides magna
Requires a snail as an intermediate host so only at risk in wet
areas and the presence of snails. Camelids are good definitive hosts
for
Fasciola hepatica and pass eggs in their feces when infected.
It takes approximately 10-12 weeks after infection before eggs can
be detected in the feces. This parasite can cause severe liver
damage. Animals are often infected when co-pastured with infected
cattle, sheep, or goats.
Camelids are an aberrant host for Fascioloides magna so
eggs are not produced and therefore not detected on fecal
examinations. Infection is possible in areas that have infected deer
and elk.
Treatment for either type of liver fluke includes
ivermectin-clorsulon combination products or albendazole in
non-pregnant animals. Limiting co-mingling with infected domestic
ruminants, limiting deer and elk access, and use of snail-eating
fowl can reduce exposure.
V. LICE
Lice are commonly seen in the winter months. If the animal has a
severe infection, you may see areas of fiber loss from chewing or
rubbing as the animal tends to be itchy. Poor growth may be seen as
well. These parasites can often be found by parting the fiber along
the dorsal midline or rump and looking at the skin for movement at
the base of the fiber. Lice are 2-4 mm in length. Sucking lice can
be treated with oral or injectable avermectin products. Biting lice
are more successfully treated with insecticidal dustings. Treat all
animals in a group or they can re-infect each other. Repeat in 3
weeks if using an insecticidal dusting product. Pour-on products do
not work well due to the heavy fiber limiting contact and absorption
through the skin.
Lice are species-specific so you cannot get infections from
your animals.
VI. MITES (aka. Mange, Scabies)
The prevalence of Sarcoptes, Psoroptes, Chorioptes have
decreased with the increased use of ivermectin. Animals with
infections will often have areas of alopecia on the face, neck, and
perineum. The areas are also itchy. Treat all animals in a group at
the same time with injectable or oral avermectin products. Repeat in
2 weeks. These are reportable diseases in some states but not
Washington.
VII. TICKS
Ear ticks can cause secondary ear infections, itching, drooping
ears. Treatment involves cleaning the ear and use of ivermectin
products both systemic and topical in the ear. Other ticks are
difficult to detect due to the fiber. In cases of suspected tick
paralysis, a thorough examination is required which includes close
clipping of the fiber. Treatment is with ivermectin products.
References
1. Cebra CK, Mattson DE, Baker RJ, et al. Potential pathogens in
feces from unweaned llamas and alpacas with diarrhea. J Am Vet Med
Assoc 2003;223:1806-1808.
2. Foreyt WJ. Veterinary Parasitology Reference Manual. Ames, IA:
Iowa State University Press; 2001.
3. Foreyt WJ, Jasmer DP. An Illustrated Outline for Veterinary
Parasitology (VM537). Washington State University, Department of
Veterinary Microbiology and pathology; 2003.
4. Haskell SRR, Anttila TA. Small Ruminant Clinical Diagnosis and
Therapy. University of Minnesota, College of Veterinary Medicine;
2001:94-96.
5. Jarvinen JA. Anthelmintics for use in camelids (VET-590).
Western Veterinary Conference 2004
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Last Edited: Oct 29, 2007 1:09 PM
