I. Pasteurellosis

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I. Pasteurellosis


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A. Etiology:

* Pasteurella multocida is a small



* Gram-negative

* nonspore-forming bipolar rod.



B. Transmission:


*Transmission occurs by direct contact
, aerosol, venereal, and hematogenous routes.

* Incidence of infection and disease is high (probably > 90%).

* Many rabbits are asymptomatic carriers. The incidence of bacterial carriage is no different in antibiotic-treated rabbits.



C. Disease Forms:

-Upper respiratory disease ("snuffles")

-pneumonia

- otitis media,

- pyometra,

- orchitis,

- subcutaneous abscesses,

- conjunctivitis

- and septicemia are manifestations of P. multocida infection.




1. Snuffles -

This is the most common manifestation of pasteurellosis.

Clinical signs characteristically include:-

serous to mucopurulent nasal exudate with sneezing and coughing. Exudate may be seen on the medial aspect of the forepaws. Signs may subside temporarily only to recur throughout life. Lesions include reddened mucosa in acute infections, thickened mucosa in chronic infections, and exudate in nasal cavity and paranasal sinuses. Antibiotic therapy usually causes abatement of clinical signs. The prognosis for disease improvement or remission is good, however there is a good chance of recurrence.









2. Enzootic Pneumonia

Affected rabbits frequently die
acutely with no signs (especially young rabbits);
anorexia and depression
may be observed.

Acute pneumonia lesions include red-grey foci of
consolidation of the cranioventral lung lobes with or without hemorrhage.


Chronic pneumonia is characterized by

generalized consolidation, encapsulated
abscesses, fibrinopurulent or mucopurulent pleuritis and pyothorax.

If the pneumonia is recognized early, aggressive antibiotic therapy may
be of some value.

The prognosis for all cases of pneumonia is poor.





3. Otitis Media

Usually there are no clinical signs.


Torticollis will occur if the function of the internal ear is compromised,
either by direct bacterial invasion or by the damaging effects of the bacterial
toxins.

Nervous signs and incoordination are observed if the bacteria
extends to the meninges. Creamy, white exudate in middle ear is found either
uni- or bilaterally.
When treated with antibiotics at the first indication
of a head tilt, rabbits with otitis media may improve or stabilize.


In rabbits with severe torticollis, NSAID or corticosteroid therapy may
be indicated. Bulla osteotomies and lavage of the tympanic bullae
has proven to be a fruitless approach to treatment. The torticollis
may progress in spite of antibiotic therapy, so the prognosis is guarded.

4. Genital Infections -


Venereal or hematogenous transmission
may occur.

Affected rabbits may have a vaginal discharge which may
be serous to mucopurulent and/or a history of infertility.
The uterus
can be palpably enlarged with pyometra. Acute infection of the uterus
is characterized by slightly dilated horns filled with grey exudate.
In chronic infections the uterine horns are greatly dilated with purulent
exudate, and are fragile.


In affected bucks, one or both testicles
may be enlarged, tender, firm and may contain abscesses.

The health
of affected rabbits can be salvaged by surgical removal of diseased tissues
coupled with antibiotic therapy.

The prognosis for recovery after
surgery is good.





5. Abscesses -




Contaminated wounds and septicemia are common
routes for abscess development in a variety of locations, but especially
in the subcutis.


The presence of subcutaneous swellings which are filled
with creamy exudate and may have draining fistulous tracts is typical of
Pasteurella abscesses. Treatments include sedation of the rabbit
prior to lancing and flushing superficial abscesses t.i.d.


with Betadine
or chlorhexidine. Systemic antibiotic therapy should be provided
for 1 week. If the infections persist, surgical resection may be
required.









6. Conjunctivitis -



Signs include epiphora with blephorospasm,
eyelids closed by excessive mucopurulent exudate and facial staining.




Reddened conjuctiva with serous to mucopurulent adherent exudate are found.


Often there is inflammation and eventual stenosis of the nasolacrimal duct,
resulting in chronic epiphora and hair loss. The use of antibiotic
ophthalmic ointments will improve most cases. Occasionally, the nasolacrimal
duct may need to be flushed to remove inspissated purulent material.





7. Septicemia -

Septicemic rabbits usually die acutely;
however, one may see pneumonia or infertility prior to death. Diffuse
congestion and petechiation of thoracic and abdominal viscera as well as
abscesses in viscera (kidneys, liver, lungs) may be seen on necropsy.







D. Predisposing Factors:

Onset of clinical disease is often
associated with some underlying stressor, such as a marked change in environmental
temperature or humidity, poor ventilation, poor sanitation, and overcrowding.


Physiologic conditions that also predispose to disease is age (very young
or very old), pregnancy, nutritional state, and genetics. Some rabbit
stocks are genetically hardier, and can carry Pasteurella throughout life
without developing clinical disease.





E. Diagnosis:

Tentative diagnosis of pasteurellosis is based on
clinical signs and gross necropsy findings of a mucopurulent exudate associated
with inflamed body parts such as the respiratory tract, subcutis, middle
ears, and reproductive tract.

A presumptive diagnosis

may be reached
by making a smear or scraping from the affected area and staining with
a gram stain. With torticollis, radiographs of the tympanic bulla
may disclose the presence of exudate or bony reaction (increased density
in the bulla). Definitive diagnosis requires isolation of the bacteria
by culturing the affected site(s).





F. Treatment:




Most Pasteurella isolates are sensitive to penicillin.
Only sulfaquinoxaline and tetracycline have known withdrawal times and
can be used for rabbits raised for slaughter. Short term use of certain
oral antibiotics, such as ampicillin or amoxicillin, or prolonged systemic
antibiotic therapy with any drug may upset the cecal bacterial flora.
If anorexia or diarrhea occurs during therapy, stop treatment immediately.
Dietary supplementation with high fiber foods, such as alfalfa cubes or
high fiber pelleted diets, or with yogurt containing live Lactobacillus
cultures may reduce intestinal upsets.




Antibiotics Commonly
Dispensed for Rabbits

Enrofloxicin


2.5 to 5 mg/kg b.i.d. for 5 to 7 days (oral and injectable)

Procaine penicillin
40 to 60,000 IU/kg body weight IM s.i.d. for 3 to 10 days

Sulfaquinoxaline

0.256 gm/50 gm feed for 30 days or 226 gm/ton of feed

Tetracycline

300 mg/liter of water for 7 days, or 5 mg/kg q.i.d. for 7 days




G. Control:

The best control for pasteurellosis is good
husbandry techniques and culling of rabbits with clinical disease.

Since
most all rabbits carry Pasteurella multocida in the nasal cavity,
management measures are aimed at controlling the clinical disease expression.

The rabbitry must have good ventilation, low ammonia levels, and low humidity
to decrease incidence of this disease.

In a breeding colony situation,
all infected rabbits with clinical disease should be culled for many reasons.


(In spite of antibiotic therapy, the chance of disease recurrence is high.
Rabbits with clinical signs shed large numbers of organisms into the environment.


The best way to improve the genetic hardiness is to remove breeders with
clinical disease.)

Clean automatic waterers and cages in which diseased
rabbits were housed and then spray with 1% bleach solution to kill residual
bacteria. (Bleach will eventually damage galvanized caging, so alternative
disinfectants can be used.)

All new arrivals should be quarantined
prior to introduction into the rabbitry.

If possible, weanling rabbits
should be raised separately from the breeding colony.