OTHER GASTROINTESTINAL PARASITES
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Glancing through a book on parasitology the reader soon discovers that several dozen different sorts of parasite can be found in the rabbit's digestive tract. They will not all be dealt with here as most are either very rare or only pathogenic under exceptional circumstances, or are little known or unknown in domestic rabbits. But in the farm rabbitry context, especially in the tropics, it is useful to have a basic grasp of the biological conditions that favour the development of such parasites.
Only one intestinal parasitic disease is found in rational rabbit production in Europe: coccidiosis. Wild rabbits living in the same regions. however, have many other parasites.
The main reason for this has to do with the various parasite cycles. Many are heteroxenous (multihost): to multiply and develop they must live successively on several hosts. For example, the little liver fluke shifts from mammal to snail to ant to mammal.
Others are monoxenous (single host) but the larval or adult form develops only in the outside environment under certain conditions (wet grassland, stagnant water, etc). This explains why rational production, by breaking the life cycle of these parasites, has eliminated the parasitic diseases they cause.
Some of these parasites are still found in farm rabbitries.
Cysticercosis (fapeworm). This common parasite produces fine, white streaks on the liver and translucent cysts, alone or in bunches, on the peritoneum and viscera. The cysts are produced by the larvae of dog and cat tapeworms. Rabbits are contaminated by eating feed that has been in contact with excrement. The final hosts (dog, cat, fox) become carriers by eating rabbit viscera.
Symptoms are few-sometimes diarrhoea-except with heavy infestations (not uncommon) when growth rate slows. There is no curative treatment. The other domestic animals have to be treated. Tapeworm larvae of other species of animals (pig, rat, etc) can also infest rabbits.
It is worth mentioning here that the larvae of some dog and cat tapeworms can infest not only rabbits but people as well (echinococcosis, coenurosis). The lesions are cyst clusters forming translucent "tumours" on the viscera or in the brain.
Taeniasis (tapeworm). Half a dozen tapeworm varieties can infest rabbits which become contaminated by eating mites in wet grass. Clinical symptoms are slight: mild diarrhoea, sometimes weight loss, very rarely mortality from intestinal perforation. A necropsy reveals flat worms a few millimetres wide, in lengths varying by species ( I cm to 1 m).
Tapeworms are seldom found in domestic rabbits. Treatments applicable to other animal species may be used.
Fasciola sp. and Dicrocoelium sp. (trematodes). Liver fluke (Fasciola hepatica) and little fluke (Dicrocoelium lanceolatum) are also very rare in rabbits. The conditions of infestation are the same as for ruminants. The intermediate hosts are certain snails found in grass from marshy areas (Fasciola sp.), or other types of snails and ants (Dicrocoelium sp.). Usually the only symptom is slowed growth. Treatment is pointless.
Trichostrongylus (nematodes). These are also small round worms (called roundworms), measuring 4 to 16 mm in length. The Graphidium (stomach worm) is rare in Europe but Trichostrongylus is very common in farm rabbitries. Rabbits become infested by eating green forage contaminated by larvae. The intrinsic pathogenic strength of these parasites is relatively weak, but they do greatly aggravate other rabbit ailments, particularly diarrhoea. Massive infestations can cause extreme inflammation of various parts of the intestinal tract (stomach, small intestine, caecum).
The conventional anthelmintics (thiabendazole, phenothiazine, tetramisole) can be used for rabbits. It is recommended that regular treatments be applied every month or two in contaminated farm rabbitries.
Two other small roundworms are frequently found in rabbit caeca and colons: Passalurus and Trichuris. These do not appear to be pathogenic except with massive infestations.
Strongylo´des (nematodes). These are small roundworms a few millimetres long able to migrate throughout all organs and reach the intestine. The etiology and epizootiology are identical to those in ruminants and pigs. Some massive infestations have been described in rabbits living in dark, damp, poorly kept hutches.
Intestinal parasitism is very common in wild rabbits. It is frequent and not of great economic importance in farm-bred domestic rabbits if overall sanitary and health conditions are satisfactory. In poorly kept hutches or where infestation is massive these parasites enhance all other ailments, both intestinal and other, making them acute, enzootic and lethal.
Rational rabbit production has done away with all these intestinal worms. Control is easy; it is only necessary to break the parasite's life cycle. Essentially this means taking care with forage:
Parasitism can be considerably cut back by frequent changing of the straw litter, which should always be dry. Late slaughter of fattening rabbits (3 months or more) is a negative factor, as some parasites have a rather long life cycle. This is interrupted by earlier slaughter. Regular treatment can also include broad spectrum anthelmintics or copper sulphate-based preparations in drinking water ( I percent) for I or 2 days.
Respiratory ailments are common among domestic rabbits. In rational production, they essentially strike breeding adults. In a farm rabbitry young rabbits can also be affected. Where such ailments are endemic, losses are especially to be feared among the females, in which the disease becomes chronic, leading to production stoppages and mortality among the nursing young. Respiratory diseases usually remain endemic, but abrupt epidemics, which can decimate the stock in a few weeks, sometimes break out in farm rabbitries.
The first symptoms arc a clear, fluid nasal discharge and frequent sneezing. The rabbit often rubs its nose with its fore-paws, the fur of which becomes matted and dirty. This is the first stage, common coryza, which is an attack on the upper respiratory tract.
Later the discharge turns yellowish, thick and purulent. Sneezing is less frequent but coughing may begin. Purulent coryza can remain stationary or develop into pneumonia, either spontaneously or from other specific or nonspecific causes (enteritis, lactation, malnutrition, etc). With pneumonia, the coryza, the sneezing and even the coughing and snuffling may disappear. The only symptoms will be slower respiratory movements, clearly visible in the nostrils, and difficulty in breathing in. In young rabbits growth slows or stops. Complications are frequent: diarrhoea, ophthalmia. sinusitis, torticollis (wryneck) and abscesses. Females can die suddenly during lactation or gestation.
At autopsy, coryza is manifested by the presence of pus in the nasal cavities and the atrophy of the mucous membranes. The lungs may be congested and parts may have a liver-like appearance. Very often there are lung abscesses with abundant yellowish-white caseous pus filling most of the chest cavity.
As with diarrhoea respiratory infections are due to the association of nonspecific contributing causes with infectious agents.
All the nonspecific attacks mentioned in the previous sections are decisive for the development of respiratory ailments. The lungs are protected by the rabbit's very developed, very complex nasal cavities. These cavities are covered by the pituitary membrane, which acts as a filter to stop dust and airborne microbes. It is therefore essential to protect this mucous membrane and keep it intact. The pituitary membrane is particularly sensitive to the following:
Three constants of disease agents are the randomness of their pathogenic strength, their numbers, and the fact that they are interchangeable. In other words, only some alteration in the mucous membranes of the upper respiratory tract will allow the germs present to develop to their specific pathogenic strength.
Bacteria. In approximate order of frequency these are pasteurella, bordetella, klebsiella, staphylococci, Escherichia coli, salmonella and Listeria.
Pasteurellosis is the disease most often cited, because rodents and lagomorphs are particularly susceptible to this germ. Pasteurellosis may take many forms in the rabbit: abscesses, mastitis, diarrhoea, metritis, wryneck, septicaemia. The rabbitry can easily become thoroughly infested, to the point where pasteurellosis can become endemic. Some pasteurella strains are more pathogenic than others. Pathogenicity can be acquired during the endemic stage, provoking an epizootic outbreak in the rabbitry or even in the entire region.
However, though pasteurella are the most common bacteria they are not the cause of most rabbit respiratory diseases. Bordetella are almost as common. In rational rabbit production the frequency of bordetella + streptococcus is as common or more common than pasteurellosis. The presence of pasteurella in a rabbitry does not indicate the presence or the probability of pasteurellosis.
Viruses. Apart from myxomatosis, which now seems more and more likely to cause pneumonia, no respiratory virus has been described in the literature. Viruses certainly do exist, however, and with rabbits as with other animal species the problem is the bacterial complications which follow them.
Parasites. There are several species which can develop in the lungs (Protostrongylus, Linguatulida, etc). They are relatively uncommon in domestic rabbits because, as with intestinal worms, an intermediate host such as a snail or dog is required. Only a laboratory analysis can reveal the presence of respiratory parasites.
RESPIRATORY DISEASE CONTROL
Chemotherapy (antibiotics, sulpha drugs) will be effective only if the rabbitry environment has been improved. Tetracyclines are pneumotropic antibiotics well tolerated by rabbits. Chloramphenicol is also often effective. Dosages vary according to the preparation but treatment should always last for 3 or 4 days. The medicine is best injected intramuscularly. Whenever a bacterium is isolated in the laboratory it is strongly recommended that an antibiogram be made at the same time. Sulfadimethoxine also works well for lung diseases and acts effectively against pasteurella.
Systematic preventive antibiotic treatments are both useless and dangerous.
There are numerous vaccines on the market of very uneven effectiveness. Most of these are pasteurella-based and sometimes bordetella-based. It is difficult to immunize rabbits against these two germs, whatever the quality of the vaccine. The main point is that bacteria are only exceptionally the direct cause of the disease, so that even if the rabbit is protected against pasteurella, it can still catch pneumonia from streptococci.
Furthermore, to be at all effective vaccination must be performed on healthy animals just after weaning and repeated 1 month later. Action is generally taken during the course of the disease only. Vaccination and chemotherapy are merely temporary measures to back up preventive hygiene.
Preventive hygiene is indispensable for success in respiratory disease control, even more than it is in digestive infections. It is covered in the last section of this chapter.
Other disorders of the rabbit
There are many rabbit diseases besides digestive and respiratory ailments. Most have disappeared from national rabbit production without the reason always being known. Others are still found in farm rabbitries but are rarely of economic importance. The following is a brief review of not uncommon diseases.
This is a viral disease (Sanarelli virus) which decimated rabbits in Europe for more than 20 years after being introduced into France in 1952. The Sanarelli virus develops in certain American rabbits, Sylvilagus (cottontails), without causing the disease, thus making them dangerous carriers.
Myxomatosis is extremely contagious and can be transmitted in many ways. Biting or stinging insects such as mosquitoes and fleas are the main vectors owing to the rapidity with which they can infect animals and the distances they are able to cover. Infection by interanimal contact or from contaminated equipment is also common. It now appears certain that pulmonary contamination is possible in confined rearing.
This virus is very resistant to weather and physical changes (cold, dryness, heat) and disinfectants. Formol, however, is very active, and is recommended for disinfecting equipment.
The first symptoms are inflammation of the mucous membranes (eyelids, genital area) which thicken and form small tumours. These tumorous nodules are found first on the tips of the ears and then all over the body. The tumours adhere closely to the skin and grow until they finally deform the whole head. Numerous nodules can be felt under the skin on the back.
Respiratory forms of the disease with no other symptom also seem to be common. Clinical diagnosis is then impossible. Recovery is rare but not unheard of when the animal can eat and there is no side infection. This is not desirable, however, for the rabbit then becomes a healthy carrier of the virus.
There is no treatment, nor should there be.
Vaccination is effective and can be done with a heterologous virus (the Shope virus which causes a small benign nodule in rabbits) or a weakened form of the myxomatosis virus. In western Europe the first is more popular, in Hungary the second.
Prevention requires good hygiene and insect control, especially of lice and fleas in farm rabbitries.
Breeders or countries buying rabbits should ensure the animals have been vaccinated for more than 3 weeks but less than 2 months before purchase, and that they come from a healthy rabbitry where regular vaccinations are the rule.
FOOT PAD ABSCESSES
Foot pad abscesses are a very common complaint, familiar to all breeders. Chronic abscesses are far more frequent under the hind paws. They start as a barely visible swelling which can be felt by palpating. They may be limited to the cutaneous and conjunctive tissues. The skin becomes thick (parakeratosis) and scabby. Infection is latent and the sores may bleed. Poor cage floor hygiene can cause a heavy side infection. The abscess then covers the whole metatarsus and becomes purulent.
These abscesses are found in farm rabbitries and in rational production where mesh floors are used. Breeding animals are especially prone to this disorder.
In farm rabbitries the main cause is poor upkeep of the straw litter, which becomes damp and rots. Various infections can follow (staphylococci, fungi) but the worst is a Corynebacterium (Schmorl bacillus) which gives rise to an evil-smelling necrotic gangrene which can spread to the head and the whole body, and then to other animals (necrobacillosis).
This disease is rare where rabbits are raised on wire-mesh floors, but sore hocks (caused by staphylococcus) are much more common than in rabbitries where straw litter is used. Poor quality, rough or twisted wires, wrong mesh size (too wide), and rust are the main culprits, all fostering the development of foot pad abscesses. It is difficult to raise heavy rabbit breeds on wire mesh.
The control of foot and hock diseases is primarily preventive:
Treatment is difficult. When there is no obvious suppuration the sores may be treated every day and then every 2 days with strong disinfectants such as iodine, Fehling liquor, paraffin oil and permanganate. The antifungoid action of iodine and permanganate is useful too in units using the litter system, which fosters complications with fungi. Antibiotic ointments are not recommended because the treatment is long and expensive and the ointments soften the skin.
When the abscesses become purulent or the fore-paws are affected the infection is then incurable and the animals should be culled. If other abscesses are noted, especially on the head (necrobacillosis), the bodies should be burnt or buried deep. Foot pad abscesses make it practically impossible for males to mate.
Buck-teeth prevent the upper and lower incisors from touching and so they do not wear down. The incisors keep growing and eventually prevent the rabbit from eating. Buck-teeth may be hereditary (jaw malformation), or the result of injury (teeth broken against wire mesh). There is no connection with the type of feed-forage, hard granulated feeds, and so on.
The only prevention is breeding. Look carefully at the teeth when buying or choosing a breeding animal. Treatment consists of cutting the teeth with sharp pliers right down to the gums every 15-21 days.
EAR AND SKIN MANGE
Ear canker or mange is very common. The symptoms are external otitis, and yellow or brown scabs in the ear canal. The course of the disease can be very long. The scabs become waxy and invade the whole ear. The inside of the ear becomes scaly.
This is a parasitic disease caused by a mite (Psoroptes or Chorioptes) and frequently complicated by bacterial infection. The middle ear may then be affected, causing wryneck (the rabbit's head is held constantly to one side).
Treatment can be effective if the disease is caught in the very early stages, that is, as soon as small yellow-brown deposits are noticed in the ear. Insecticides are applied locally in the ear. Organophosphates (for example, malathion) are preferable to organochlorines (DDT, lindane) which, though very active, are dangerous to man. Glycerine, iodized oil or cresyl oil are also effective with frequent applications.
Prevention involves culling rabbits whose external ear is deeply affected, and treating all other rabbits for several days in a row and then every fortnight. Throughout the treatment the straw litter must be changed frequently as the parasites can stay alive in the litter for a long time.
Skin mange is much less common. Today it is only found in poorly managed rabbitries. Lesions start at the edge of the lips, nostrils and eyes, spreading to the head and fore-paws as rabbits frequently rub their heads. The skin dries, the hair falls out and the skin becomes scaly and finally scabby. The skin mange mites, Sarcoptes and Notoedres, are not of the same family as ear canker mites. Treatment is the same, but prevention measures (culling diseased rabbits, cleaning cages) must be stricter.
Ringworm, also called dermatomycosis or trichophytosis, is a skin and hair disorder. Not very common in farm rabbitries, it is widespread in rational rabbit production. It starts with circular bald patches, usually on the nose. The hair looks clipped and the skin is irritated and inflamed. More small patches appear on the head, ears and fore-paws, and then over the whole body. On the oldest lesions the hair can be seen growing again in the centre.
It is a very contagious infection that can sometimes be transmitted to humans, though it is more commonly transmitted to other domestic animals such as dogs and cats. Ringworm is caused by microscopic fungi that can belong to different families (Trichophyton, Microsporum, Achorion) and are not specific to rabbits. There is no economic loss as long as infestation is light.
Treatment is long and costly. An antimycotic (griseofulvin) is administered in the feed for about 10 days. During treatment all equipment should be frequently cleaned and disinfected, in a 5 percent formal solution for example. Many producers, successfully it seems, sprinkle powdered sulphur (sulphur flowers) on the ground, cages and nesting boxes. In small rabbitries local treatment can be applied with antimycotics in powder or liquid form (tincture of iodine and other dyes), but preventive hygiene should accompany the treatment. Badly afflicted animals should be culled and domestic animals treated.
As well as the lice and fleas that are specific to rabbits, ectoparasites of other animal species (particularly poultry) can also bother rabbits. Not found in rational rabbit production, these farm rabbitry ectoparasites can harm production and, worst of all, they are the vectors of many diseases, including myxomatosis. With good hygiene and external antiparasitic preparations they can be rapidly eliminated.
Trichophagy or fur-eating occurs both in farm rabbitries and in units using wire-mesh floors. The animals eat each other's fur and end up with bare backs and flanks. All sorts of diagnoses have been advanced: unbalanced rations, behavioural problems, unsuitable environment, amount of light, overpopulation, genetics and so forth. It was very widespread when wire-mesh cages were first used extensively, but seems to be declining with the general improvement in production conditions (equipment, feed, strain).
There is no exact preventive measure and no specific treatment.
Other diseases that are transmissible from rabbits to humans (or that are common to both) include ringworm; gangrene of the paws and head, caused by Spherophorus necrophoris; hydatidosis or coenurosis, caused by larvae of dog and cat tapeworm; and trypanosomiasis. By contrast, neither rabbit variola (pox virus) nor rabbit syphilis (Treponema cuniculi) can be transmitted to humans.
Zoonoses are diseases shared by many animal species, especially man. Most have no special feature peculiar to rabbits and are rarely contracted by them (rabies, tetanus, etc). So only a few are mentioned here, either because they can be dangerous to people or because the appearance of the disease in the rabbit reveals its existence on the farm or in the village.
Zoonoses have apparently never been identified in rational rabbit production. This is because contamination is usually spread by forages polluted by other animal species. Zoonoses are also usually adult diseases; the early slaughter of animals (10-12 weeks) limits their spread.
When these diseases are suspected the dead animals should be burnt or buried, and human hygiene should be intensified.
Though antibiotic treatments may be effective in certain cases it is best not to treat but to cull the entire stock. Good hygiene is the only prevention. Apart from the usual rules of cleanliness, forage must be cut and stored with special care. Rats and mice are formidable propagators of these diseases.
Rat extermination around rabbitries is fundamental.
This disease is very rarely reported in rabbits. Nevertheless it does exist and may be of avian, bovine or human origin (in decreasing order of frequency). The rabbit is very resistant to tuberculosis, so the disease evolves very slowly. The lesions, which are the sole indication of tuberculosis, can only be seen in breeding animals. The main organ affected is the lungs, and less frequently the liver, intestine and kidneys. The spleen is very rarely affected.
The classic tubercular nodules are found in the parenchyma of these organs, often containing an almost solid cheese-like pus.
This is more common in guineapigs, wild rabbits and hares than in domestic rabbits reared on straw litter. It has almost disappeared with modern wire-mesh cage rabbit production. Pseudotuberculosis is one cause of synovial arthritis in man. The germ Yersinia pseudotuberculosis provokes numerous whitish nodular lesions on the intestinal viscera, especially the spleen, which becomes enlarged. These nodules, ranging in size from a lentil to a chickpea, are sometimes amalgamated. They are scattered throughout the abdominal cavity but are rarely found in the lungs.
Apart from a steady weight loss there are no symptoms to diagnose. The disease can easily be recognized by post-mortem examination.
There are few data on this disease. Various findings from Africa on the subject, while not contradictory, are not uniform.
It has been demonstrated that rabbits can contract trypanosomiasis experimentally or in particular circumstances. They are particularly susceptible to Trypanosoma brucei.
There are reportedly some rabbitries in tsetse fly areas, for instance in Cote d'Ivoire, with no recorded cases of spontaneous outbreaks of trypanosomiasis in rabbits. Trypanosomiasis has caused some problems in Mozambique, however. It has been reported that its symptoms are oddly like those of myxomatosis.
This disease is less rare than tularaemia, and still appears sporadically in farm rabbitries. A septicaemic disease caused by Listeria monocytogenes, it is very difficult to diagnose clinically. Listeriosis should be suspected when the following symptoms appear on the farm:
TULARAEMIA (RABBIT FEVER)
This very contagious disease is common in hares, but rabbits seldom contract it. Its significance is the danger it represents for man. A bacterial disease (Francisella tularensis), it gives rise to a high fever, leaving the animals in a semicomatose state. Lesions cause enlargement and congestion of the spleen. The liver is often dotted with numerous tiny grayish-white spots (miliary necrosis) about the size of a grain of millet.
Toxoplasmosis is unquestionably more common in farm rabbitries than is generally believed. It is caused by the intermediary stage of an internal cat and dog parasite, Isospora. The course of the disease does not usually produce symptoms, though there may be jerky nervous reactions. The lesions are translucent cysts in the brain, and in muscles or viscera. Often the spleen is enlarged.
Diseases and disorders associated with reproduction
Respiratory ailments are the main disorders affecting pregnant rabbits in closed rearing. In intensive production, apart from the environmental causes described earlier, lactation must be added as a contributing cause. In young nursing does, hard-to-diagnose ailments can be complicated by acute or subacute pneumonia. The doe may die before weaning her litter or have to be culled shortly afterwards.
DIGESTIVE DISORDERS AND ENTEROTOXAEMIA
Digestive diseases are far less serious in adult animals than in growing rabbits. The classic coccidiosis-type diarrhoea is rare in adults.
Intestinal parasitism (coccidiosis, strongylosis) will be latent or chronic, fostering the appearance of other diseases.
Enterotoxaemia is more common, especially in farm rabbitries. With or without mucoid enteritis it can develop very rapidly ( 1-7 days). Most often it occurs in late pregnancy or mid-lactation, sometimes in association with symptoms of acute pneumonia. In traditional rabbitries, complications of paresis or paraplegia are common, especially in fat, overfed does working at low-intensity breeding rates. Control in this case involves adapting the reproduction rate to the feeding capacities of the production unit. There is no treatment.
Some 25-30 percent of does die in intensive production, usually with no warning symptoms. Mortality occurs in mid-lactation in young first and second-litter females and in the latter stages of pregnancy in older does. Often called enterotoxaemia, this illness is certainly not of infectious origin, though bacterial complications are common. It is rather more like a metabolic disorder, such as milk fever in ruminants or eclampsia in women. Its etiology is still not clear. There is no curative treatment. Mortality can sometimes be reduced by preventive doses of calcium in drinking water or parenteral injections (Ca gluconate) just before kindling.
The external genital organs (vulva, penis, scrotum) can be the site of specific venereal diseases. The best known is rabbit syphilis or vent disease, caused by a spirochete ( Treponema cuniculi). It has never been reported in rational rabbit production, but vent disease is not exceptional in rural rabbitries. Inflamed lesions become ulcerated. Bucks are often affected (orchitis, balanitis) and transmit the disease, which can turn enzootic. This is a benign disease which impedes mating. It can easily be treated with antibiotics (penicillin, tetracycline).
Attention: this disease can be confused with the onset of myxomatosis!
The internal genital organs can also become infected. These far more serious, far more common infections make reproduction impossible.
Metritis or white discharge, a uterine infection, is often associated with mastitis and respiratory complaints. It is a major rabbit disease.
One symptom of metritis is an abnormal frequency of sterile does and mastitis in the rabbitry. Abortion, which is usually rare, may become more common. Metritis shows up at post-mortem: the uterus is thickened and poorly retracted and there may be abscesses at the last embryo implantation site, sometimes covering the whole uterus (pyometris).
Etiology is complex. Gestation and kindling are obviously contributing causes, but hygiene is a determining factor, and a chronic pasteurellosis in the rabbitry could be the culprit. The most common germs are nonspecific: staphylococci, pasteurella. The specific germs such as toxoplasm, Listeria and Salmonella are much less common. Specific infections are likely if there is widespread abortion.
Antibiotics can be given, especially at the onset of the disease. But they will not be effective unless the most advanced cases are culled- very thin does, or does with purulent mastitis or symptoms of pneumonia or purulent coryza.
Preventive medicine, in this case vaccination, is only valid for pasteurellosis (see section on respiratory diseases). Preventive hygiene is decisive in controlling internal genital diseases.
ABSCESSES AND MASTITIS
Abscesses are very common in rabbits. They sometimes grow to enormous size, and develop very quickly without any apparent change in the animal's health. There are two preferential sites in does: the submaxillary area and the teats. These and foot abscesses are the main reasons for culling breeding does.
Most often the cause is Staphylococcus aureus, but other germs may be present. The worst are pasteurella, which can make the disease epizootic and lead to numerous complications (pneumonia, septicaemia, abortion). Mastitis is common in units with mesh floors and is probably fostered by congestion caused by chilling. When mastitis is in the congestive stage (hard, reddened mammary gland but no pus) the disease may be staved off by a 3-day antibiotic treatment and the local application of astringents (vinegar) twice daily to aid decongestion. It is uneconomical to treat abscesses or purulent mastitis.
NONINFECTIOUS REPRODUCTION PROBLEMS
Absolute sterility is relatively rare. "Sterility epidemics" are usually seasonal and can often be traced to insufficient light (less than 14-16 hours). Sterility otherwise occurs after 1 or several kindlings (see previous chapter). Does serviced 3 times with no results should be culled for both hygiene and economy.
Cases of twisted uterus are not uncommon. This is discovered during post-mortems on does which die during gestation. The causes are not clear. Overcrowding of the uterus and disturbance of does are frequent explanations.
. Delayed birth
Delayed birth often occurs with small litters (1-3). Foetal retentions are common in this case, invalidating the doe economically. In modern production, birth is systematically induced by injections of ocytocine on day 33 of pregnancy (servicing on day zero).
Young first-litter females are the usual offenders. Disturbances, or mice in the nesting box, are possible causes.
There is no treatment for prolapses of the vagina.
Real cannibalism due to abnormal behaviour in the doe is exceptional. The female usually eats only those young which are already virtually dead but still warm. This may happen a few hours or days after parturition. Insufficient drinking water after parturition is considered a cause in farm rabbitries, and this could well be the true reason.
This is most often done by young females whose milk has not let down, or has let down too late. A doe that abandons 2 litters should be culled.
THE NEST AND YOUNG RABBIT MORTALITY
Compared with other domestic animals, rabbits are still virtually in the foetal stage at birth.
The survival of newborn rabbits, and hence the ultimate success of the rabbitry, is closely related to the quality and hygiene of the litter's immediate environment.
If the amount and type of materials used for the nest (straw, wood shavings, hay, etc) are inadequate during the first few days, the newborn rabbits will get cold and death is then inevitable. The doe does little to intervene. She pulls fur to help make the nest; she nurses her young once a day and sometimes she will defend access to the nest, but she does not care directly for the young. If the nest box is poorly designed and the young are able to get out after the first few days, the doe will not put them back.
If nest hygiene is poor (droppings, dampness) or if the mother is sick (mastitis, coryza) the young will develop a nostril-blocking rhinitis within a few hours. Their sense of smell is crucial as it guides them to the mother's teats. Small staphylococcic abscesses can quickly develop on the young rabbits' bodies (belly, groin, tarsus) in these conditions.
In modern French rabbitries with highly prolific does, an intensive reproduction system and adequate environmental conditions, an estimated 57 percent of the young are stillborn and another 16-20 percent normally die before weaning. About a third of this mortality figure is accounted for by precocious dam mortality. Some of the young can be saved by fostering 2 or 3 to another nursing mother with young of the same age. The remainder of the losses take place during the first 2 weeks of lactation. Occasionally entire litters are lost during the first 4-5 days.
The etiology of these mortalities is not known, but it seems to have more to do with the doe's state (lactation?) than with any particular disease of the newborn rabbits.
These figures indicate that a mortality rate of less than 15-20 percent should not be considered catastrophic. On the other hand, after the first 1520 days of lactation young rabbit mortality should be very low. If it is not the dam should be examined for mastitis or coryza. Cage and nest box hygiene should be checked. Pre-weaning diarrhoea (30-35 days) is a sign of inadequate hygiene. Coccidiosis indicates very poor hygiene.
The word prevention has been constantly repeated throughout this chapter as essential for successful rabbit production. Careful hygiene is usually enough to prevent major disease crises. Preventive medicines (vaccinations, anticoccidiosis treatments, etc) have been described. They are not widely used in rabbit production. The basic rules of preventive hygiene are now set down in detail.
LOCATION AND DESIGN OF THE RABBITRY
It has been emphasized from the outset that rabbits must have an environment in which they do not constantly have to withstand external disturbances and aggression.
The rabbitry should be located whenever possible far from such nuisances as noise and dust (dust carries microbes), sheltered from the prevailing winds, and in hot countries shaded from the sun.
Rat and mice extermination should be considered, as both are formidable, healthy carriers of diseases to which rabbits are susceptible.
Cleaning should be constantly kept in mind in the designing and building of a rabbitry. Nothing that cannot easily be cleaned and disinfected should be allowed. The rabbit's immediate surroundings (cage, feeding racks and drinkers) in particular should be portable, so they can be regularly removed, cleaned, dried and disinfected. In completely closed buildings the ventilation should be carefully designed for flow without draught. Where ventilation is used, forced-air ventilation is preferable, as it keeps insects out and makes it possible to control the air flow by adding or removing vents.
Some authors insist that in tropical countries the interior of the building should be sufficiently protected to act as a buffer against swings in temperature and humidity, especially during the rainy season, to cut down the incidence of pulmonary diseases. As an example, a rabbitry in Burkina Faso built with local materials (laterite bricks, palm framework, straw roofing) recorded a much lower range in temperature variations than did a "strong" building made of construction blocks with a tin roof.
Where possible, metal should be used for the wire-mesh hutch and accessories as it is the easiest material to clean and disinfect.
The rabbit's excitability is a contributing factor in illness. Casual visitors such as feed suppliers, rabbit buyers and other breeders (who are vectors of diseases from other rabbitries) should be barred. Rabbits should be protected against dogs, cats, and small wild carnivores.
Feed and water hygiene is basic as both can carry numerous rabbit diseases (coccidiosis, worms). Feed should be stored out of the reach of domestic animals. It should be distributed in troughs or racks, but never on the ground. Drinkers should never be set on the ground.
Rabbits drink a lot of water, but they won't drink dirty water. Water is the ideal medium for coccidia sporulation. Accordingly it should be changed and drinkers cleaned often.
Cage and nest hygiene is particularly important while the does are nursing. In wire-mesh hutches the cage must be removed and cleaned after each kindling. In farm rabbitries the straw litter must be renewed often. After kindling any stillborn young should be removed from the nest and the nest remade if necessary. Contrary to widespread belief, a doe will not abandon her young if they have been touched. It is only necessary to keep the doe out of the nest during the cleaning operation.
After weaning, if straw litter is used it should be kept clean and dry. The more animals per cage, the more difficult this is. In every type of production system weaning demands scrupulously clean, disinfected, dry cages. Weaning is one of the crucial moments in rabbit production. Avoid transporting the animals, mixing up litters and using questionable cages. Successful production depends on these details.
It is also necessary to work constantly against any increase in bacterial infection. Chronically sick animals (with coryza, pneumonia, mastitis, abscesses), especially breeding animals, must be culled. A sick breeding animal in a rabbitry is of small value compared to the danger it represents for the rest of the stock, the cost and uncertain outcome of treatment, and the possibility of its quick replacement (sexual maturity at 4 months).
In completely closed buildings the control of bacterial infection should include the maintenance of walls, ceilings and especially floors. Damp or dusty floors are a permanent source of air pollution.
The early slaughter (10-12 weeks) of animals for market is also a form of preventive hygiene. Many diseases take several months to develop before becoming contagious, especially in small or farm rabbitries.
Man is the most dangerous permanent vector of disease. He can bring in contaminants from the outside, so he should wash his hands before entering, and don footgear and a smock which always remain inside the rabbitry. Only a human being can palpate a doe suffering from mastitis and then systematically go on to infect all the mammary glands of the females to be palpated that day. Clean hands are extremely important, especially when handling animals and distributing feed and forage.
Preventive medicines to control parasitic diseases also help to maintain a healthy environment. Many parasites undermine the animals' state of health without causing directly perceptible losses, and open the way for a great variety of infections, but the systematic use of antibiotics as a preventive measure is not at all recommended. The abuse of antiparasitic drugs, especially of sulpha drugs, does far more harm than good. All drugs are poisons which must be used with caution.
Disinfecting the rabbitry should be a routine matter that follows some simple rules:
Cleaning. Dirty equipment cannot be disinfected. It must be washed first, or if water is short, carefully scraped and brushed.
Drying. Proper drying is in itself a first step towards disinfecting equipment.
Chemical or physical disinfecting. It should not be forgotten in this context that sundrying well-cleaned equipment for several days is a simple, cost-free and very efficient means of disinfecting. The only preconditions are a storage area off limits to domestic animals and a reserve supply of extra equipment so that cleaning and disinfecting time will not cut into production time.
In industrial production, pressurized steam-cleaning equipment is indispensable.
No matter what precautions are taken, after 1, 2 or 3 years health problems will become less and less easy to control. Imperceptibly productivity will decrease, despite an increase in hygiene and care and in the experience of the breeder. This has to do with rising levels of bacterial infection in the rabbitry, coupled no doubt with the irreversible presence of harmful microflora and microfauna in the animals.
Sanitary isolation becomes essential at this point. All rabbits in the affected section of the rabbitry must be culled. All equipment must be cleaned, repaired and disinfected. After this is done the area must be left vacant for some time (1-2 weeks) before introducing new rabbits.
Some small farm rabbitries have 2 premises which they alternate every year. This is a kind of 1-year sanitary isolation which has proved very effective.
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