Rabbit diseases diagnosis, prevention and control

- Bacterial Diseases

1-Pasteurellosis

Etiology

- Pasteurellosis in rabbits is caused by the organism Pasteurella multocida, a bacteria is a gram negative stained short rod, bipolar that includes a large variety of different strains.
-Some of these strains are highly virulent and cause serious disease, while others may only induce mild disease or no disease at all.

- Has 5 antigenic group ( A, B, C, D, E) A and D are the most common isolates from rabbit as primary respiratory diseases followed by Staph and Bordetella as secondary cause.

-Different strains also infect different species of animals. The bacteria reside in the upper respiratory airways of clinically normal animals but if the sensitive lining of the respiratory system is damaged by ammonia, dust particles, a virus or other bacteria, Pasteurella invade and initiate an immune response, causing clinical disease.
Other strains are involved in enzootic pneumonia and lung abscess.
In chickens, Pasteurella multocida causes fowl cholera.

Pasteurella multocida is the most common bacteria responsible for respiratory infections and also competes with Staphylococcus as the major cause of carcass abscess, reproductive tract infections and mastitis.

- Animal can be symptomless carrier.

It called overt diseases (stress related).

Culture Media: The organism grows on blood agar. It is aerobic and facultative anaerobic. The colonies are mucoid in appearance.

Predisposing factors :

1- Ammonia is extremely destructive to the cells lining the respiratory system.
Therefore, poor ventilation and lack of effective air exchange are the most
important concerns. When combined with hot, humid conditions we have the
potential for high mortalities from snuffles
2-In winter, excessive draught also increases susceptibility to infection. Shed design, ventilation and temperature control have been discussed in a previous section. an even flow of ventilation throughout the shed with maximum air-exchange and minimal draught is the ideal to work towards.
3-Diets that are over 18% in protein when fed to rabbits result in higher production of faecal and urinary ammonia, thus further compounding the problem. As mentioned previously, there is a high carriage of Pasteurella multocida amongst normal rabbits.
4-Although transmission from normal carrier animals to animals completely free of the bacteria is normally very low, animals that develop clinical disease shed bacteria at much higher rates (direct transmission). Thus management factors including no quarantine facilities, poor identification of diseased livestock, cross fostering from diseased does and poor culling policies together with inadequate hygiene to eliminate the bacteria that have been shed will predispose to infection. It is important to note the Pasteurella multocida can remain viable in water nipples and unclean feeders for several days (indirect contact through utensils).

Susceptibility:

-    All ages are susceptible.

-   Young developed acute form with high mortality.

-  Semi-mature and adult acquire sub-acute and chronic with low morality.

 

Snuffle

Snuffles is a severe infection of the upper respiratory tract. Young rabbits as
well as lactating does and performing bucks are equally susceptible in death.

The most common clinical signs are:

1- severe nasal discharge, chronic sneezing and wet matted fur on the inside of the fore legs from constantly rubbing the nose.
2- sneezing due to snuffles must be differentiated from sneezing due to pellet dust or water droplets entering the nasal cavity. Wet patches on the forelegs and nasal discharge (a mixture of mucus and pus) are the giveaway signs.
3- Infections including conjunctivitis and pneumonia may take place secondary to snuffles.

P.M: Rhinitis, sinusitis, in chronic cases erosion in turbinate bone and atrophy.

Pneumonia/lung abscess

Tend to be a chronic due to large numbers of organisms in the environment.
Infection can either be acute, where sudden death occurs or chronic, usually involving lung
abscesses where rabbits lose weight rapidly and experience deep, difficult respiration (dyspnoea).

D.D: Dyspnoea must be differentiated from laboured breathing due to heat-stress or shock.

Following infection of the respiratory system, young rabbits usually die within a week. Those that survive fail to thrive and do not reach market weight. Infected animals continually shed bacteria into the environment, resulting in transmission of the disease to other susceptible stock.

P.M: Large abscesses can be present in thoracic cavity, hemorrhage on lung fibrin cover , pleural cavity.

Wry-Neck ((Head Tilt) (Otitis Media)
Wry neck is the common name for a middle ear infection

Pasteurella can spread from nasal cavity to the ophthalmic bulla via the Eustachian tube. Presence of inspissated pus in the deeper structure of ear spread along the nerve leads to neurological signs with rolling and nystagmus.

Rabbits lose their sense of balance and direction and consequently tilt their heads to one side. Wry neck is not particularly serious and whilst some animals may develop brain abscess, the majority go to slaughter at the correct market weight.

Body abscess

In contract, young growers with severe pasteurella body abscess usually fail to thrive. The abscess continually forms, discharges and regresses, spreading bacteria into the environment. Infection usually results from pre or post weaning injury with the opportunistic bacteria invading wounds caused from fighting. After surgery may cause osteomyelitis
Rabbits that make slaughter are usually condemned which is worse than the animal dying during the growing period. Abscess along the backbone is a particular problem due to the fact that they are not usually noticed until dressing and result in complete carcass condemnation.

Mastitis/Metritis

Does tend to suffer mastitis or metritis concurrent with snuffles. Lactating does are highly susceptible particularly if nutrition during breeding is inadequate (poor quality feed, too much energy in the ration) they are housed in draughty conditions or suffer heat stress or they are placed under a highly stressful breeding program. Does do not usually die directly, performance drops substantially, kids do not thrive and concurrent snuffles infection results in transmission to neighbouring does who may in turn succumb to infection. Female affected showed vaginal discharge, fail to concept. Bucks showed abscess in tests.

Conjunctivitis

Swollen eyes glued shut from exudates congestion of conjunctiva with serous purulent exudates and epiphora (abnormal flow of tears).

Haemorrhagic septicemia

In peracute cases no signs animal die from fever, lung hemorrhage. L.nodes showed sever congestion chest cavity contain a clear yellowish fluid.

Diagnosis:

1- Clinical signs
2- Isolation of causative agent but not relied on (may M.O die during transport, M.O found in deeper tissue, M.O may be normal inhabitant)
3-Serological test

4- PCR

Treatment and prevention

Firstly, it must be stressed that while many antibiotics will successfully destroy the
organism, most of these drugs do not penetrate the nasal cavity of rabbits well and are of little effect in reducing the carrier status of the animals. They will have some advantage in controlling secondary infections such as pneumonia, particularly during hot, humid summers and draughty winters, however their routine use for the control of pasteurellosis is not warranted.

1-Terramycin is probably the most effective either through the feed or water although it can reduce growth rates by depressing appetite and predispose to diarrhea. The dose rate is 250-500 mg/L drinking water.

2- Cephalaxine used parentally.
3- Antibiotics effective against Pasteurella include enrofloxacin trimethoprim sulfa, chloramphenicol, penicillin G, and azithromycin.

4-N.B: pencillin used only parentally as by oral rout leads to diarrhea.

5-Gentamycin effective in local application (eye drop, nasal drop, ointment) to avoid nephrotoxicity.

6-Compination between Enrofloxacine and oxytetracycline will be effective.
Culling is by far the most effective policy, operating a high culling rate in the breeding phase of production with plenty of replacements over time yields stock with better resistance and prevents transmission of the organism. Kids from does suffering with pasteurellosis should never be cross-fostered and must be raised independently from
unaffected growers.

Vaccination:

-Dead formalized vaccine at age of 2 month 1cm S/C and boaster after15 days then:

 Revaccination every 6 months in non-endemic area
 every 2 months in endemic areas.

The vaccine includes somatic antigens (3, 12) and capsule types A and D, with
improved cross-immunity observed among the same serotype strains.

Overall, effective management of pasteurellosis in rabbits focuses on cautious
antibiotic use, strategic culling, and vaccination programs to enhance herd
immunity

Differential diagnosis: Other respiratory diseases
Bordetella bronchiseptica is another common inhabitant of the respiratory tract, but is not normally associated with respiratory disease.

Secondary Staph. aureus infections can also be found.

Myxoma virus causes nasal and ocular discharge, and one form does produce

predominantly respiratory signs, although this is rare

 

Viral Haemorrhagic Disease produces tracheal and lung haemorrhage and sudden death.

Prevention and control:

-Pasteurellosis must be considered when planning initial shed design.
-Ventilation and air exchange must be even through the shed with effective .

- Removal of manure or ammonia without causing ammonia to rise to cage level.
-Temperature must be controlled within a 10°C range and no excessive draught should be apparent.
-Management techniques including the early diagnosis of diseased livestock and effective culling policies must be adopted.

- Culling policy should aim at severely affected animals initially and then include mild to sub-clinical carriers as production becomes more successful.

2-Stapylococcosis

Etiology: Staphylococcus aureus.

Most disease causing strains in rabbits are hemolytic, coagulase-positive, mostly type C strains.
General: Outbreaks occur sporadically in commercial and laboratory facilities and
manifestation of disease ranges from localized abscessation to acute septicemia.

Transmission:

-Direct contact, aerosol. Carrier animals can harbor the organism in the upper respiratory tract.
-Possible entry sites include umbilical vessels and skin abrasions.

Pathogenesis: After inoculation, the organism can spread hematogenously or via local extension resulting in pyoderma, purulent mastitis, internal abscessation, septicemia and purulent bronchopneumonia. Pododermatitis or “sore hock” may occur in association with abscesses or mastitis.

1-Suppurative lesions composed of thick, purulent exudates can be found in the
subcutaneous , mammary gland, genital tract, conjunctiva and the respiratory
tract.
2-Suppurative emboli can be found in the kidney, lung, brain and heart. With
mastitis, the affected glands have swollen, red areas with indurations of the
overlying skin due to chronic abscessation.
3- In pododermatitis, the swelling and exudates is usually concentrated along the
ventral hock area.
4- Focal supportive necrotizing lesions with colonies of cocci.

Diagnosis:
Demonstrate Gram positive cocci on Gram-stained sections. Confirm by bacterial culture, but must determine if the isolate is a pathogenic strain (Beta
hemolytic)
Differential diagnosis: Pasteurellosis, Tyzzer’s Disease and listeriosis.
Treatment:

Demonstrate Gram positive cocci on Gram-stained sections. Confirm by bacterial culture, but must determine if the isolate is a pathogenic strain (Beta
hemolytic)

Differential diagnosis: Pasteurellosis, Tyzzer’s Disease and listeriosis.
Treatment:
sore hock: Topical ointments with Gentamycin antibiotics, can put flat surface in cage or put rabbit in solid-bottom cage with soft bedding, but creates sanitation problems.

 

3-Bordatellosis

Etiology: Bordatella bronchiseptica

General: The role of this organism in respiratory disease is not firmly established. It can be recovered from the upper and lower respiratory tract of healthy rabbits.
In cortisone treated rabbits, suppurative bronchopneumonia has been reproduced
experimentally and the organism has been isolated from natural cases of localized
pneumonic lesions.

Transmission: Direct transmission by aerosol. Bordatella bronchiseptica may impair airway clearance mechanisms and facilitate establishment of Pasteurella multocida.

P.M:

Chronic interstitial pneumonia, chronic bronchiolitis and perivascular and peribronchial infiltrations.

Diagnosis:

Bacterial culture. Organisms often present in large numbers.