खेती वाले खरगोशों में रोग- एक सिंहावलोकन
Rabbits are highly prolific animals which have enormous reproduction potential. They have the capacity to convert 20% of their feed protein to meat protein second to broiler chicken which has 23% conversion. Rabbit rearing is expected to be a viable alternative to broiler poultry industry as virtually there is zero competition between them for feed resources.
Like all other domesticated species, rabbits are also susceptible for various ailments. They are afflicted by number of infectious and non-infectious diseases. The success of rabbit industry relies upon reduction in the mortality, increase in the fryer production per maternity cage, reduction in operation / feeding cost. To run a Rabbitry with economic success, every effort should be made to reduce the loss of kits, does and fryers.
Diseases are the commonest cause of loss of litter, doe and fryers. The common disease control strategy followed in other farm animals cannot be applied as such in rabbits. In this publication, an attempt is made to give a brief introduction to commonly occurring diseases in farmed rabbits and their management especially for beginners.
1. Snuffles in Rabbits
Snuffles is almost similar to common cold in human beings but it is caused by a very common bacteria. Poor ventilation in Rabbitry can predispose to snuffles. Building up of offensive ammonia odour in a Rabbitry due to inadequate ventilation harms the upper respiratory tract. Snuffles is a clinical condition in rabbits characterized by nasal discharge, frequent wiping with the inner aspect of forepaws, cough and loss of weight.
This is caused by Pasteurella multocida. There are different strains of varying origin. Strain acquired from human visitors / handler causes only snuffles. But a very virulent rabbit strain can cause serious illness like pleurisy, pneumonia and death. Spread occurs among the rabbits in a farm by direct contact. Poor ventilation and stress play a major role in the spread.
Majority of small scale rabbit colonies (Maintained in hutches) and almost all large scale cage-based rabbitries have this problem of snuffles. Medications with antibiotic can help to solve the problem transiently. Long term solution is possible with systematic management and culling. At any cost, there should not be any compromise in ventilation.
There are two commonly practiced types of ventilation. Positive ventilation is by bringing in the outside air into the shed by a power-operated ventilator. Negative ventilation is evacuating the air inside the shed by means of ventilators.
Negative ventilation is the very commonly used method. Placement of air-inlets should be based on the external temperature. In winter, air is allowed to enter at the eaves of the shed but in hot summer air entering near the floor is comparatively cool.
The same Pasteurella can cause serious afflictions like pleuropneumonia in rabbits. These serious affections are observed only at necropsy. Except weight loss, no remarkable changes are observable in live animals. Even the deteriorating body condition can be recognized only by palpation not by visual inspection.
2. Abscesses under the skin
Rabbits affected with pasteurella organism may develop multiple abscesses under the skin all over the body. This is very commonly seen in all age groups. This condition is frequently noticed both in small and large scale rabbitries. Subcutaneous abscess size may range from a peanut size to a hen’s egg located in different parts of the body. Abscesses may occur as solitary lesion or clusters.
Abscesses in rabbits are mainly causedby pasteurella and Staphylococcus aureus. Peculiarly, rabbit’s pus is thick and viscid like tooth paste. Hence draining through narrow opening is difficult. Widely opening the abscess is necessary to drain the pus out. Systemic antibiotics like tetracyclines are of advantage in treating abscess in rabbits.
3. Cutaneous staphylococcosis
In some instances, staphylococcus organisms can cause a serious abscesses and moist dermatitis and may lead to death. In new born kits, staphylococcal moist dermatitis may lead loss of entire litter. Hence more attention should be given specifically to kits before weaning.
The affected kits appear wet and small abscesses are noticeable all over the body. This disease is quite common in large rabbitries wherein litter hygiene is compromised. Sometimes staphylococcal organisms affect both doe and kits. Affected does suffer from mastitis. The human strain of staphylococcus is mild and abscessation occurs sporadically.
Conversely, the rabbit strain causes a more severe and fatal disease in young kits. In case of mastitis in a doe, kits tend to be deprived of milk, starvation and death. Colloquially, mastitis in rabbits is termed as blue bag. Early identification can save the kits from starvation and death. Apart from this, Staphylococcosis do manifest as uterine inflammation and visceral abscessation located in abdominal cavity and thoracic cavity.
The lesions appear as superficial white foci in the size of pin-head on wet skin. In older rabbits, numerous pea-sized abscesses under the skin, purulent conjunctivitis, closed eyes due to sticky exudates and pneumonia are common findings. Notice of staphylococcal abscess in a new born litter is unfavorable for the viability of large Rabbitry as the elimination is very difficult. Litter management, nest box hygiene, timely culling of affected animals can reduce the incidence. Treatment with antibiotics like tetracycline is found to be effective.
4. Wry neck condition in Rabbits
This condition is also caused by Pasteurella multocida. Apart from causing snuffles, pneumonia and cutaneous abscessation, pasteurella organisms affect the middle ears and consequently head tilt is characteristic. Middle ear is usually infected and inner ear gets affected in serious cases. Affected rabbits keep their head tilted towards the affected side. Close examination of affected ears can reveal presence of exudates occluding the ear canal and dried exudates form a scab.
In some severely pathogenic strains of pasteurella, body cavities like mediastinum, peritoneal cavity, and uterus are also affected.
5. E coli infections
Escherichia coli infections occur both in weaned and unweaned rabbits.It is characterized by yellowish diarrhea, inappetance and death. E.coli infections are noticed both in small and large rabbitries. E. coli organisms tend to attach to the intestinal epithelium and efface the absorptive villus surface.
This results in loss of absorptive surface consequent failure of absorption. Rabbits kits aged 1 to 14 days are very vulnerable. Infection with E coli is characterized by watery diarrhea, distended belly, wet and stained posterior part of body, loss of appetite and death. In severe outbreaks, whole nest is affected and all litter lost.
6. Coccidiosis
Coccidian parasites are protozoan parasites affecting the rabbits. They are very prevalent in traditional keeping as colonies. Commonly, coccidiosis results in retarded growth in broiler rabbits. Occasionally, severe infections lead to hind limb paralysis. Almost always the occurrence of occurrence of coccidiosis is attributed to unhygienic housing. Use of coccidiostats and keeping the rabbits in cages considerably reduced the incidence of cocciodiosis.
There are two distinct forms of coccidiosis in rabbits. They are liver cocciodiosis and intestinal coccidiosis. Liver cocciodiosis is caused by Eimeria steidae; Liver cocciodiosis occurs both in traditional and commercial rabbitries. Young rabbits are frequently affected. But death is uncommon and retardation of growth is the frequent manifestation. Often, liver cocciodiosis is an accidental finding in post mortem examination. Emaciated carcass, moderate to severe enlargement of liver, pea-sized abscesses in the liver are characteristic necropsy findings. Sulphonamides are effectively used to treat coccidiosis in rabbits.
Another form called Intestinal coccidiosis is caused by 8 different species belonging to Eimeria.Among them, E.flavescens and E. Intestinalis are highly pathogenic and capable of causing death. Other species like E.coecicola, E.magna, irresidua, E.perforans are less lpathogenic and they commonly cause retardation of growth. At necropsy, thickening of intestinal wall and presence of pin-point haemorrhages in the caecal and colonic mucosa is characteristic.
Intestinal cocciodiosis should be differentiated from E coli infection and clostridial endotoxaemia. Hygienic measures, housing the rabbits in wire mesh floor cages, avoiding straw bedding, use of commercial coccidiostats in feed, treatment of affected animals and their isolation an effectively control the incidence. For prevention of coccidiosis, administration of Sulphonamides for 7 consecutive days and repeating again after a gap of 7 days is suggested.
7. Hairballs / wool block
Rabbits are habitually very clean animals. They frequently groom themselves. While grooming, fur can be swallowed by them which will cause trichobezoars. Physiologically, during the nest building process in advanced pregnancy, they do pluck their fur from the ventral abdomen, around the mammary glands, inner thigh and dewlap.
The fur plucked is used to line the nest. During this process also, there are possibilities for swallowing the fur. Very low fibre content in rabbit diet predisposes to ingestion of fur. All these circumstances lead to formation of hairballs and intestinal obstruction. This condition can be diagnosed by careful palpation of abdomen. Serious obstruction may be life threatening.
Feeding some loosening agents like mineral oil -20 ml and massaging mildly can resolve the wool block. Alternatively, drenching 10 ml of fresh pine apple juice two to three times a day can also disintegrate the hair balls. The enzyme bromelin present in the pine apple juice loosens the hairball and voided by natural process of excretion.Likewise, papain in papaya juice or commercial pharmaceutical products can also be used.
Provision of adequate fibre, relief from boredom and changing the light rhythm (lighting breaks) can help to avoid the problem of hairballs in rabbits.
8. Sore hock
Otherwise called ulcerative pododermatistis; there are many factors play their part for precipitation of this condition. The skin of the rabbit is very soft and fragile. Hence they are predisposed for abrasions, laceration and other injuries. Thickness of the skin, padding by the fur on paws, quality of wire mesh, and litter on the floor are the determinants for the incidence of sore hock in rabbits.
Small abrasions may extend to serious ulceration and even to lymphangitis. Abscessation is a common sequel. Restlessness, loss of appetite, loss of weight, cessation of breeding activities is the signs commonly seen in sore hock. The causative agent, staphylococcus aureus may spread to abdominal cavity also and cause renal lesions in advanced cases. This is preventable to certain extent.
Dry bedding and changing at regular interval will certainly reduce the incidence. Only suitable crossbreeds or breeds should be kept in cage floor. Recent introduction of plastic grill reduces the incidence of sore hock considerably. Treatment is not usually practiced for broiler rabbits; only for valuable breeder stock, treatment is attempted with topical and systemic antibiotics and sprays.
9. Caecal impaction
The posterior part of the alimentary tract in rabbit has a role similar to that of rumen in cattle. Especially the caecum has unique motility pattern and bacterial population which facilitate fermentative digestion. For unknown reasons the normal digestive process by the caecum is compromised and result in impaction.
This condition is characterized by thick viscid mucous accumulation and proceeding to slowed intestinal motility. Progressive slowing of motility ends up in constipation of cecum. Research in this condition has been concluded as this condition was of non-inflammatory origin. So, technically this condition is termed as caecal impaction and mucoidenteropathy complex.
Caecal impaction occur in rabbits two weeks after weaning and very prevalently seen in stall-fed, high concentrate feeding, low roughage diet conditions. Onset of illness may be sudden or delayed and progression to impaction is almost inevitable.
Affected animal isolate themselves from the cage mates. They stop eating roughages and pellets but the water intake continues to increase. Frequently, grinding of teeth is noticed. On palpation of right ventral abdomen, a cord-like mass is usually palpable. Shortly before death, fluid running out of nostrils is a quite common observation in affected rabbits. Mortality rate ranges from 60 to 100%.
Post – mortem lesions are characteristic and limited to caecum. Dried up or watery content, lump of mucus in caecum are the hallmarks of caecal impaction. Occasionally, the apical lobe of lung has changes suggestive of foreign body pneumonia. Treatment is not usually successful.
Metamizole / analgin and dexamethasone are used with inconsistent success. Prevention is attempted with tetracycline @ 250mg/liter of drinking water.
10. External parasites
Mite infestation (mange) is common in backyard rabbits. Commonly identified mite is Psoroptescuniculi. The signs are itching ears, head shaking, scratching with paws, greyish-white crusts in the ear canal and ear lobe. Mixture of paraffin and ectoparasiticide can be applied to resolve the problem.
Removal of crusts and application of commercially available ointments (ectoptasiticidal + antibiotics) will also cure the condition. Nowadays, Injection of ivermectin subcutaneously and repeating itafter 6 days is found to be effective.
CheyletiellaparasitovoraxandListrophorusgibbus are the Fur mites infesting the rabbits. This infestation is readily identifiablein white rabbits. Appears as small black dots on the back of the rabbits. Itching is frequently accompanied sign. Topical dressing or dipping with commercial dipping solutions is effective
Lice and fleas are not common in rabbits. European Rabbit flea, Spilopsyllus cuniculi is common; it is a potent mechanical transmitter of myxomatosis in rabbits; all ectoprasites are capable of transmitting myxomatosis, a highly contagious viral disease once devastated large population of wild rabbits in Australia and New Zealand. The episode of myxomatosis is Australia was intentionally spread to reduce the wild rabbit population which became an agricultural pest.
11. Myxomatosis
This is a contagious viral disease of rabbits characterized by skin tumors. Lesions may be mild. Occur both in wild and farmed rabbits. Heavy manifestations may lead to mortality. In rabbits kept as colonies, transmission of this myxoma virus occurs through ectoparasites like ticks, fleas, mites and flies.
In large rabbitries, iatrogenic transmission is common occurrence by exchange of needles and other equipment among diseased and healthy rabbits. Mosquitoes and fleas play the role of mechanical vectors. This disease occurs seasonally according to the seasonal breeding of vectors. In acute cases of myxomatosis, oedema of head, eyelids, genitals, blepharo-conjunctivitis with purulent exudate clogging the lid movement, blindness are the characteristic symptoms.
In chronic infection of myxomatosis, pseudo-tumors in ear, nose and paws are commonly noticed. They may drain and heal spontaneously. These pseudo-tumors regress spontaneously and leave a scab which may also disappear in due course.
Vaccination is in practice in some countries. Similarly, iatrogenic transmission is also common in an event of vaccination in outbreak. Although vaccination is not advisable in an outbreak, myxomatosis severity may come down. Changing the needle for each maternity cage is mandatory to curtail the spread.
12. Rabbit syphilis
Treponema cuniculi is the causative agent for syphilis in rabbits. This spirochete infection is rare in industrial rabbitries. This agent is specific to rabbits and not capable of causing disease in human beings. Redness (Erythema), swelling (edema), vascular lesion on extremities andexternal genital organs, scab on rupture are characteristic of syphilis.
Lesions may later spread to muzzle and mouth owing to autoinoculation. Self-mutilation results in painful ulceration. Dark field microscopic examination of skin scrapping is sufficient to diagnose the presence of Treponema. This is one of the disease which responds very well to treatment in rabbits. Complete cure can be expected for tetracycline and chloramphenicol administration
13 Encephalitozoonosis
Encephalitozooncuniculi is a protozoan parasite causing a neurological disease in rabbits. Convulsion, torticollis, paralysis, urinary incontinence and scalding of the perineal area are the features. Necropsy reveals kidney lesions, small depressed areas of necrosis and scars on renal surface are the common. Latent infections are very common in encephalitozoonosis.
14. Toxoplasmosis
From cats, a protozoan parasite spreads to rabbits, other domestic animals and even human beings. Toxoplasma gondii has high seroprevalence than clinical illness. Having the zoonotic potential, toxoplasmosis needs strict preventive measures in place. Feed contaminated with cat feces is the main source of infection.
Listlessness, fever and death in few days are observed in toxoplasmosis. Highest morbidity is seen in pregnant and lactating rabbits. At necropsy, congestion of organs; inflammatory lesions on lungs; severe swelling of liver(ten times the normal size) are noticeable. Potentiated Sulphonamides are effectively used.
15. Ring worm
Ring worm lesions are commonly caused by Trichophyton and Microsporum fungi. They spread by direct contact and fomites shared among the infected and healthy rabbits. They cause circular patchy hairless areas on the skin. Later, the lesion develops scales. These fungal agents are zoonotic.
Diagnosis by wood’s lamp examination of lesion or microscopic examination of plucked hairs. Topical keratolytic agents and antifungal agents like miconazole are effective. Even if not treated, the lesions tend to subside spontaneously after correction of nutritional and management shortcomings.
16. Red urine
In general, the urine is cloudy and turbid in clinically healthy rabbits. This is due to high concentration of calcium carbonate in urine. Rabbits kept in cages do void in the same place regularly and chalky calcium carbonate deposits are quite commonly observed on the floor of the cage. In some occasions, rabbits void red-tinged urine.
Although it does not have any clinical significance, it attracts the attention of farmers. Plant pigments and metabolites tend to cause the red urine condition. There are variations even among the cage mates who eat same fodder. Feeding of greens like spinach, carrots, radishes also have some hypothetical correlation with red urine.
This condition improves spontaneously and does not require any treatment. Rarely, uroliths, uterine infections, urinary tract infections can also cause red discoloration of urine. Special diagnostic procedures are to be employed for arriving at a definitive diagnosis.
17. Moist dermatitis
Pseudomonas aerogenosa causes this condition. Not very frequently observed. Characteristically, greenish fur colour change on the affected skin with eczematous lesions are noted. Topical and systemic treatment with common antibiotics solves this issue.
18. Tyzzer’s diseases
Clostridium piliforme is the causative bacteria. Tyzzer’s diseaseis characterized by diarrhea, loss of condition and death. Clinical diagnosis is made difficult by the manifest-alike salmonellosis, cocciodiosis, clostridial septicaemia, colibacillosis.
Lower alimentary tract is affected and fecal smear examination may reveal cocci arranged in piliform / filamentous stems. Necropsy reveals salt grain sized abscesses on the liver surface.
19. Indirect antibiotic toxicity
Penicillins are not indicated in rabbit. Penicillins, lincomycocin, vancomycin,tylosin, amoxicillin, ampicillin are capable causing an indirect toxicity in rabbits. Oral administration of these antibiotics derange the normal fauna of caecum thereby alter the fermentative digestion.
In the absence of normal fauna, Clostridium piliforme like organisms grow rapidly and an endotoxaemia like crisis prevails. This pathogenesis takes few days to two weeks. Loss of rabbits is usually an outcome of indirect antibiotic toxicity. However, chloramphenicol, tetracycline, Sulphonamides, fluoroquinolones and aminoglycosides are comparatively less harmful to rabbits.
General disease prevention in rabbits
The three vitals of a profitable, return-oriented Rabbitry are cleanliness, ventilation and observation.
Diseases in rabbits occur as a result of faulty management. Almost all diseases in rabbits are either caused or precipitated by defective management. There are three vital features in every Rabbitry which needs to be followed scrupulously. They are cleanliness, ventilation and observation.
Cleanliness- It is principal method of preventing occurrence of diseases in rabbits. Proper and time-bound disposal of wastes, litter material, excrement, dead animals, kindling remnants is very essential. They not only create health hazard but potentially attract predators.
Ventilation- Rabbit excrement has strong odour. Their urine has raw calcium carbonate deposits. Ammonia production is high. In the event of poor ventilation, ammonia build up inside the house will detrimentally affect the health and subsequently production. Poor ventilation is a main precipitation factor for snuffles- very common pasteurella infection in rabbits which can pose a serious threat for Rabbitry.
Observation- Rabbits are noiseless animals and they exhibit clinical illness in a subtle way. Frequent visits and regular observation in rabbit houses help us to diagnose illness timely and attend early. Early detection of external parasites can limit the spread of myxomatosis. Affected animals should be isolated. To contain the spread of staphylococcosis, pasteurellosis, and many other contagious infections, culling and disposal is advocated.
Authors:
Jegaveera Pandian
ICAR- Central Sheep and Wool Research Institute,
Avikanagar, Rajasthan-304 501
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