| Agricultural development workers training manual: Volume IV Livestock |
|Chapter III: Guidelines and references|
Volunteers working in the field with rabbits should place more of their energies and resources on prevention of rabbit parasites, rather than on expensive chemical cures. As we have said repeatedly, prevention of both diseases and parasites (through good husbandry skills) is far more valuable than cure. Chemical cures are often unavailable, expensive, and of only short-term value. The key to parasites is knowing their life cycle so that you can plan to disrupt it and thereby remove them from rabbits in the least expensive manner. 90% of prevention of rabbit parasites depends on good sanitation and a good, balanced feed ration.
Coccidiosis is the prevalent parasitic disease of domestic rabbits. It is caused by a microscopic parasite that invades the lining of the intestine or liver. In these locations, the parasite multiplies extensively, and then leaves the body in the feces. Rabbits that recover from this protozoan infection frequently become carriers. It is important to distinguish between liver coccidiosis and intestinal coccidiosis. At least 4 species of coccidia live in the intestine, and 1 species grows in the liver.
Not all species of coccidia are equally harmful, and rabbits tolerate moderate numbers of some without illness. The most dangerous of the intestinal forms are Eimeria magna and E. irresidua. These produce symptoms such as diarrhea, poor appetite, weight loss, and sometimes death. E. irresidua evokes the most severe tissue damage. In some cases, direct damage may occur to the intestinal wall. The clinical diagnosis of coccidiosis depends on finding the oocysts in the feces or intestinal contents. Field diagnosis depends on live and post-mortem identification of the symptoms. Diagnosis of live animals is often difficult because other diseases and disorders produce similar symptoms.
Control of intestinal coccidiosis depends largely on management practices that minimize the danger of fecal contamination of feed, water, and hutch floors. Wire bottom floors greatly reduce the hazard presented by solid floors or slots. Feeders should be designed so that fecal contamination is held to a minimum. This is best done by building a feeder that the rabbits cannot sit in. An automatic water system (bottle and can) is recommended. Oocysts passed in the feces require moisture and warmth to sporulate and become infective. Therefore, coccidia are more widespread in the humid tropics than in other climatic zones. Dry wire floors and automatic water systems hinder sporulation of the parasite.
Sulfaquinoxaline administered continuously in the drinking water (0.025% for 30 days) prevents the development of the clinical signs of hepatic (liver) coccidiosis in rabbits heavily exposed to E. stiedai. Sulfaquinoxaline may also be given in the feed at 0.025% for 20 days, or for 2 days out of every 8, until slaughter. The rabbits acquire an immunity to subsequent infections. Lower concentrations of the drug are not satisfactory. The maximum prophylactic effect is obtained by 3 weeks of administration. A concentration of 0.10% of sulfaquinoxaline in the feed, or 0.05% in the feed and 0.04% in the drinking water, given continuously for 2 weeks, is recommended for therapeutic control of naturally occurring outbreaks. The drug should not be given within 10 days of slaughter of the rabbits. Sulfametazine, sulfamerzaine, or succinyl-sulfathiazole in the feed at 0.5% concentration have also been used during outbreaks
Treatment has only a temporary effect on intestinal coccidiosis, but may be useful in controlling outbreaks. When needed, a ration containing 0.1% sulfaquinoxaline may be fed continuously for 2 weeks. Intestinal coccidia develop a tolerance to the drug if it is used continuously, so treatment is not suggested unless clinical symptoms appear.
E. stiedade, the one species of coccidia that multiplies in the liver, is considered to be the most pathogenic coccidia of rabbits. Like the other forms, it enters the intestinal wall, but migrates to the bile ducts, where it reproduces. Infections lasting more than 16 days can be recognized by the white, circular nodules of the liver. The coccidia multiplies in the epilthelial cells of the bile ducts, which become thickened and tortuous and contain a vast number of occysts. In the early stages of infection there are no unusual symptoms, then the appetite decreases, a potbelly develops, and sometimes death follows. In moderate infections, there is no mortality, but disfigurement of the liver will occur.
Liver coccidiosis is acquired in the same manner as intestinal coccidiosis. The control measures also similar; however, liver coccidiosis can be controlled more easily by proper management.
Nosema cuniculi is the cause of this mild but long standing disease in rabbits. Many apparently healthy animals may have kidney lesions related to this infection. These lesions include cortical scarring with multiple, indented gray areas on the surface of the kidney. The scars extend from the cortical surface to the medulla. Nosematosis is a contagious colony infection. The organisms are passed in the urine and transmitted when there is urinary contamination of feed or water. Transmission may also occur to unborn rabbits in the uterus when the doe has the disease. The disease can be controlled by providing good sanitation and preventing contamination of food and water by urine. No treatment is available.
Roundworms (ascarius) are slender and cylindrical. They are found in the digestive tract. The stomach worm is a very slender, reddish worm about 1/2 inch long. Trichuris strongylus-the whip worm-is about the same size but is found in the small intestine. Both have similar life cycles. Eggs are passed in the feces, and after a short period small infective larvae develop. Moisture and warmth favor larval development; larvae are ingested and pass to the stomach or small intestine where they grow into adults.
Signs of infection depend on the degree of infestation. Light infestations produce little effect; heavy infestation may cause diarrhea and emaciation. The stomach worm produces ulceration of the stomach wall. Rabbits kept on the ground are more apt to be exposed to parasites than those kept on wire. Control can be accomplished by proper sanitation.
The pinworm, Passalurus ambiguus, is a common parasite of rabbits. These worms are glistening, white, and 1/2 inch long. They are often seen on the surface of freshly passed feces or through the wall of the cecum when animals are slaughtered. Ordinarily, pinworms do little harm. As the mature worms become inactive, they are passed out of the cecum as fecal pellets are formed. These parasites are spread from animal to animal by ingesting feed and water contaminated by the droppings of infected animals. Management methods used to control coccidiosis are effective against pinworms. When treatment is necessary, piperazine citrate is effective when administered at 100 mg/100 ml drinking water for one day. Also, phenothiazine may be mixed in the feed at a 2% strength.
Tapeworms occur in rabbits as adults in the intestine and as larval forms in the liver and abdominal cavity. The adult forms are very rare in hutch-raised rabbits (they are fairly common in tropical zones where rabbits are raised on dirt floors) but larval forms are more common.
The rabbit tapeworm, Cittotaenia ctenoides, is flat, ribbon shaped, and made up of numerous segments. It has a head with 4 suckers with which the worm attaches to the lining of the intestine. Rabbits harboring a few tape worms show no signs of disease. When many tapeworms are present, diarrhea and emaciation occur. Control is readily accomplished by good sanitation.
The most common larval forms of tapeworm are those of Taenia pisiformis. They are fond in the abdominal cavity and in the liver. Rabbits acquire these tapeworms infections by eating contaminated feed and drinking contaminated water containing tapeworm segments and eggs from the feces of dogs. The young larvae are then released from the eggs, penetrate the digestive tract, and migrate to the liver. They migrate within the liver, leaving white streaks behind, then leave the liver and enter the abdominal cavity. They then form small fluid-filled cysts (cysicerci), which may be attached to the membranes holding the intestinal tract or may exist free in the abdominal cavity. Each cyst contains an embryonic tapeworm, which, when eaten by a dog, will develop into a mature tapeworm. Dogs should not be allowed near rabbits nor allowed to eat any part of a raw rabbit carcass. Treatment for larval stages in the rabbit is not practical so control must be accomplished by management.
6. Ear Mite (Mange)
Psoroptes cuniculi, the common ear mite of rabbits, causes ear mange or canker. This condition is probably the second most common parasitic disease in rabbits. It is surpassed only by coccidiosis in terms of the damage it causes. Both can occur in well-managed colonies that are housed on wire floors as well as those raised on solid floors.
The mites live in the ear canal and cause damage to the skin lining this area. An exudate of brown, waxy material soon covers the inner ear. This dark encrustation consists of cellular debris, keratin, dried blood, and mites in varying stages of development. In severe cases, the entire inner surface of the external ear may be involved.
An effective medicine for ear mange is made of 1 part kerosene and 2 parts vegetable oil. Mineral oil by itself may also be used. If an outbreak occurs, first treat all rabbits in the colony. Start with those rabbits showing few signs of disease and finish with those having severe infections. This will minimize spreading of the parasite. Swab the entire inner ear with the oil mixture on a cotton swab or a piece of cloth. Allow a small amount to run down into the ear passage. If scales or crusts are sparse, be sure to work the oil well into the ear. If heavy crusts are present saturate them with oil until they become soft, and then remove them with tweezers. Then medicate the ear again. Burn all the cotton swabs and material removed from the ear.
Ear mange can be treated and eliminated from colonies by rigidly following the above treatment program. However, all rabbits must be treated, and all new introductions to the colony must be free of mites to keep the condition from reoccurring. Psoroptes cuniculi, Notoedres cati, and Cheylcticella parasitovorax may also cause mange on the skin of the head and body in rabbits. These parasites may cause the skin to become dry, scaly, irritated, and itching with hair loss in affected areas. Treatment is by dusting with talc containing 0.25% Insecticide.
7. Cuterebrid Flies
Larvae of Cuterebra flies are common subcutaneous parasites of wild rabbits but infrequent parasites of domestic rabbits. The adult fly appears wherever populations of wild rabbits exist. Rabbits are infected when the fly deposits eggs on the fur. Grub worms hatch from these eggs and burrow into the skin to form warbles. The larvae grow under the skin and may get as long as three-quarters of an inch. When full grown, the grubs leave the skin, drop to the ground, and develop into flies. The warbles cause little trouble when they are found in small numbers. The larvae can be removed by enlarging the opening in the skin and drawing them out with tweezers. The wound should then be painted with an antiseptic (such as iodine).
8. Fleas and Ticks
Rabbits are not commonly infested with fleas, but the rabbit flea, Spilopsyllus cuniculi, and the dog and cat-fleas Ctenocephalides cants and C. felis, occasionally have been reported on rabbits. These are more common when rabbits are not raised on wire floor cages-especially in the tropics. There are 4 stages in the life cycle of these fleas-egg, larva, pupa, and adult. The eggs are deposited on bedding and in cracks of the nestboxes and develop into larvae in a short time. These larvae then form pupae from which the adult fleas emerge. Control is aimed at killing the adults on the host and the immature forms in the nestbox. To destroy adult fleas, dust the animals with a commercial preparation of pyrethrum, rotenone, sevin, or malathion. Dusting should be repeated several times during a 2 week period. When dusting with malathion or sevin be sure to work the insecticide in past the fur to skin and avoid the head and eyes. Immature forms can be controlled by burning old nest box litter and scrubbing nestboxes with hot water and bleach.
The rabbit tick, Haemaphysalis leporispalustris, is a common parasite of wild rabbits and is less common on domestic rabbits because their housing is often not compatible with the life of the tick. However, this tick is one of the reservoirs of tularemia. This is a serious human disease, and care should be taken to insure that wild rabbits are not allowed access to areas in which domestic rabbits are being raised.