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Treating Parasites

Dr. Jay Hriez, DVM

Written By:


HLRSC Guidebook -7th Edition

A parasite is defined as an organism that lives on or in an organism of another species, known as the host, from the body of which it obtains nutriment. Intestinal parasites can cause major problems in domestic rabbits because their anatomy and physiology is already somewhat delicate in terms of overall health and response to disease. It is important to recognize signs of rabbits with possible intestinal parasites. Any rabbit or group of rabbits that have signs of lethargy, lack of appetite, cachexia (wasting away), or dull, listless coats should be of prime suspect for a possible internal parasitic infection.

It helps to think of protozoa as a distant cousin of bacteria. Like bacteria, they are single celled. They are more complex than bacteria however because they have a nucleus and other cellular components that bacteria lack. One of the most common protozoal infections that a rabbit breeder will encounter at some point in their individuals or herds is Coccidia. There are currently 12 species of Eimeria, commonly referred to as Coccidia, that we find in domestic rabbits. Most of them are confined to the small and large intestine with the exception of one hepatic (liver) coccidian species.

Intestinal coccidiosis is the most common presentation noted by rabbit breeders and can be diagnosed with fecal flotation at most small animal veterinary clinics. Rabbits become infected with these species by ingesting oocysts of the organism, which is usually from other feces or fecal contamination. Whether or not a rabbit becomes ill is determined by multiple factors including the amount of the organism ingested, the species of the organism, age, and individual susceptibility of the rabbit. The most common age group that's affected is young rabbits. Signs include: weight loss, diarrhea (+/- blood +/- mucous), and dehydration.

It is important to note that since the disease is common in younger rabbits, the situation generally deteriorates rapidly once diagnosed. Quick intervention is often needed. Breeders with multiple rabbits showing these signs should pool a fecal sample for diagnosis via a fecal float.

Treatment of intestinal coccidia is most commonly achieved with Sulfa based drugs. The most common of which are:
- Sulfamethoxine (AIbon) at 75 mg/kg/day PO for 7 days
- 0.02% Sulfamerazine sodium via drinking water
- Trimethoprim-sulfa at 30 mg/kg PO q12h x 10 days
- Amprolium 9.6% (Corid) in drinking water (0.5 mI/ 500 ml 17 oz.)
- Ponazuril (Marquis in horses) at 20 mg/kg PO q24h x 7 days

It is important to point out that the following treatments are coccidioSTATS and are not coccidioCIDAL. This merely inhibits the replication of the pathogen while the rabbit gains immunity to the disease.

Hepatic (liver) coccidia are a common ubiquitous organism in rabbitries not treated with coccidiostats. Kits that suddenly die with little to no clinical signs are prime suspects for this! Unlike the intestinal coccidia listed above, a fecal float DOES NOT identify this organism. Rabbits that have succumbed to this form of coccidia will have diagnosis made upon necropsy. Common findings include an enlarged liver, nodules on the liver, and an enlarged gallbladder.

Prophylactic use of coccidiostats can be implemented in most rabbitries because of the low cost of the drug, along with the fact that rabbits tolerate sulfa-based drugs very well. Treating a herd every six months is a good place to start.

Intestinal Parasites: aka "worms"
The following organisms are what we commonly refer to as "worms" in domestic rabbits. These parasites are frequently seen with the naked eye and can cause major problems in your rabbitry if left undiagnosed. The most common place a breeder will see these parasites are in the rabbit's fecal pellets. Those who butcher their own rabbits and/or perform necropsies regularly may see some of these parasites in
abdominal organs.

These are commonly referred to as a type of roundworm in rabbits and more specifically pinworms. The most common species we see is Passalurus ambiguuus. Rabbits can have a relatively large amount of these worms and appear perfectly normal in many instances. Adult pinworms are generally found in the cecum and colon and breeders will generally see them passed in feces. They are approximately 10 mm in length, white, and visible with the naked eye. Rabbits become infected by ingesting the parasite's eggs (a fecal-oral route). Areas that have been contaminated with pinworm-infested feces should be thoroughly cleaned prior to any new rabbits living there.

Rabbits that are allowed to graze on fresh grass are at risk for becoming infected with Obeliscoides cuniculi or the rabbit stomach worm. After ingesting the eggs, the larvae of the parasite begin hatching in as little as 30 hours. Like pinworms, rabbits generally do not show outward clinical signs. Severely infested rabbits may show depression, lack of appetite, and poor weight gain. Treatment of these parasites can be done with Fenbendazole (Panacur or Safeguard) at 20 mg/kg by mouth. Repeat the treatment in 14 days to account for new infection. lvermectin can also be used at a dose of 0.4 mg/kg by mouth and repeated in 14 days. Alternatively, to treat on a herd wide level breeders can obtain Piperazine powder. Dissolve 3 grams
per liter of water or approximately 12 grams per gallon of water for two weeks.

Cestodes are commonly referred to as tapeworms. Rabbits have five species that can live in their Gl tract: Cittotaenia variabilis, Mosgovoyia pectinata Americana, M. perplexa, Monoecocetus Americana, and Ctenotaenia ctenoides. C. variabilis is the parasites that are most often found in domestic rabbits in the United States and Europe. Tapeworms have a very characteristic segmented appearances (their body
repeats in small pieces) and can grow to be very long. Treatment of them involves a single dose of praziquantel 10 mg/kg by mouth. This drug is commonly called Droncit.

Trematodes are known as flukes. The two common species we see in domestic rabbits are Fasciola hepatica and Hasstilesia tricolor. H. tricolor is generally not pathogenic (causing disease) but may be incidentally found in rabbits at necropsy or slaughter. F. hepatica are generally located in the gallbladder or bile duct of rabbits. Signs to look for include cachexia or wasting, poor hair coat, lethargy, and occasionally death. Eggs of this parasite can be found on fecal flotation of the intestinal parasite, while the adult form can be found incidentally like H. tricolor. Like the cestodes, a single treatment of praziquantel will take care of them.

Rabbits and cavies are subject to a myriad of ectoparasitic infestations that can wreak havoc on a primecoat or fool you into believing another metabolic process is occurring. While there are multiple parasites that can live in various soft tissues in rabbits and cavies, this article will focus on their ears and fur specifically.

Ear Mites
The ears of rabbits in particular are subject to relatively severe forms of parasitic infections of ear mites. This organism, Psoroptes cuniculi, is an obligate nonburrowing parasite. Obligate infers that the rabbit is this parasite's preferred host. A caveat to this is that it can live off of the host for up to 21 days! Breeders who come across this in their herd will notice very thick, reddish-brown crusts exuding from one or both ear canals. As the infection progresses, the infection spreads to areas like the face, neck, legs, feet, and dewlap. This process is extremely pruritic (itchy) and you may find your rabbit literally carving his or her outer ear to shreds some days. Even the most serious cases of ear mites usually respond extremely well to lvermectin and it should be the first drug you reach for in the case of ear mites. I recommend 0.4 mg/kg SC (subcutaneous under the nape of the neck) for 2-3 treatments 2 weeks apart. So a severe infection may get a SC injection on 3/11/09, 3/15/09, and 3/21/09. It is important to note that many times the mites have left
a trail of destruction in their path and a resulting superficial bacterial skin infection may be present. As an adjunct treatment, I usually will also administer Trimethoprim sulfa (Sulfonamide and Trimethoprim, TMS, SMZ-TMP) at 30 mg/kg by mouth twice a day for 2 weeks.

Fur Mites
Chyletiella parasitovorax is often referred to as "walking dandruff' in rabbits as it appears like large flakes of walking scales to the naked eye. This mite usually just causes dry, scaly, sometimes itchy dermatitis on the neck, trunk, hind end, and abdomen. The mite can be seen grossly or easily under a low power microscope for identification. Other mites commonly affecting rabbits include Leporacarus gibbus and Sarcoptes scabei. Rabbits infested with mites can be treated with lvermectin with identical directions that were used for ear mites.

Cavy mites include Trixacarus caviae and Chirodiscoides caviae with Trixacarus infections the most common. Cavies with infestations have excessive pruritus and secondary infections that form following infestation. The degree of itchiness has been characterized as so severe that cavies may have seizures from them. The most common areas affected are over the shoulders, on top of the neck, and on the thighs
and back. Cavies respond well to lvermectin given at 0.5-0.8 mg/kg SC 7 days apart (nape of the neck just like rabbits). Secondary infections, like rabbits, are cleared up readily by TMS at a dosage of 25 mg/kg PO twice a day for 2 weeks.

Fleas. ticks. and lice
Fleas are common in rabbits that are housed in close proximity to dogs and cats. Fleas can also come from rabbits housed outside and have occasional contact with wild rabbits. Rabbits with a flea infestation will have a dull, lifeless coat with hair that can be easily removed. They will often be itchy and have patches of hair missing. Rabbits can be safely treated with Advantage for CATS. I prefer 0.4 ml applied to the base of the neck for rabbits less than 9 pounds or under 10 weeks of age. Double this dose for rabbits over 9 pounds (0.8 ml).

Ticks occur in both wild and domestic rabbits with the most common species being the hard tick, Haemaphysalis leporis-palustris. Ticks cause all of the previously mentioned signs of mites and fleas however also can cause significant blood loss and anemia. They are also vectors for some very serious diseases including myxomatosis and papillomatosis. Remove any visible ticks you see with forceps being
careful to remove the entire tick. lvermectin at the dose mentioned earlier will kill any remaining adults that are feeding. Lice are relatively rare infestations in rabbits and may be safely treated with lvermectin at the dosing regimen listed. For cavies, I recommend using 0.3 mg/kg SC 10 days apart to control lice infestations.

Some Quick Tips:
- Rabbit and cavy mites are ZOONOTIC meaning that they can transiently infect you and cause itching!
- NEVER, NEVER, NEVER use Frontline (fipronil) on rabbits! Commonly used in dogs and cats to treat
fleas and ticks, this has the potential to cause seizures and death in rabbits after application.
- Make sure you follow any treatment of ectoparasites with thorough cleaning of any bedding, horizontal
surfaces, or objects your rabbit or cavy come in contact with.

Drug Formulary
The following medications are all commonly used in the prevention and treatment of parasites in rabbits. They are all summarized here in an easy reference with easy to follow conversions:

Ivermectin (Ivomec) Ear/ fur mites, Pinworns 0.04 mg/kg PO SQ 0.02 cc/ lb.

Sulfamethoxine (Albon) Coccidia 75 mQ/kQ PO 0.7 cc/ lb.

Trimethoprim sulfa (SMZ-TMP) Coccidia 30 mg/kg PO 0.3 cc/ lb.

Amprolium (Corid) Coccidia 9.6% in drinking water 0.5 cc/500 ml water

Ponazuril (Marquis) Coccidia 20 mg/kg PO Marquis is a paste
and must be compounded
Fenbendazole Pinworms 20 mg/kg PO 0.9 cc/lb Panacur
(Panacur) Panacur is given orally at above dose
(Safeguard) Safeguard is a paste must be compounded

Piperazine Pinworms Drinking water 3 gm/ liter water
or 12 gm/gallon

Praziquantel (Droncit) Tapeworms 10 mg/kg PO
23 mg tablet (for cats) for small breeds
34 mg tablet (for dogs) for large breeds

Prophylactic de-worming
The homage for any rabbit breeder that has a rabbitry is prevention over treatment. Many medications used above are relatively inexpensive and can be used on a regular basis to help prevent infestation with external or internal parasites. This is just a suggested schedule. The interval between treatments can be as frequent as once a month or as infrequent as every six months. Breeders who have routine prophylactic
de-worming programs in their herd often report better flesh condition, increased vigor during stressful conditions, low sickness, and low death rates.

Large Herds
The ideal de-worming schedule for a large herd (100+) would be the utilization of the water since automatic drinking systems are common. I recommend a quarterly (every 3 months) or bi-yearly (every 6 months) administration of a de-worming agent and a coccidiostat. This would include Piperazine in the drinking water to prevent pinworms along with Amprolium (Corid) to lower the incidence of coccidiosis.

Medium & Small Herds
These rabbitries may have the ability to individually de-worm rabbits on a bimonthly, quarterly, or bi-yearly schedules. I would recommend using lvermectin or Fenbendazole for prevention of pinworms. The advantage of lvermectin is that it has coverage for all major external parasites. The advantage of Fenbendazole is that it used for treatment of E. cuniculi. For coccidia, I would recommend Albon, Trimethoprim sulfa, or Ponazuril.

The ARBA Rabbit & Cavy Health Committee
Chairman: Dr. Jay Hreiz (NC)
2012 Committee Members: Dr. Wendy Feaga (MD), Dr. Fritz Trybus (IL), Dr. Nicole Velotta (WA), Denise Ancharski Stutler (PA)

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