Pasteurella multocida Infection in Rabbits Barbara Deeb, DVM, MS
Dept. of Comparative Medicine
University of Washington
Related Articles Forthcoming...
Pasteurella multocida is a well known cause of morbidity and mortality in
rabbits. The predominant syndrome is upper respiratory disease or
"snuffles." P. multocida is often endemic in rabbit colonies and the
acquisition of infection in young rabbits is correlated to the prevalence in
adult rabbits (1). If young rabbits are removed early from infected adults,
the chance of infection for the young decreases. Rabbit colonies free of P.
multocida infection have been established by fostering cesarean-derived
neonates onto P. multocida-free does or by treating does with antibiotics
prior to kindling and up to weaning of kits. Transmission is mainly by
direct contact with nasal secretions from infected rabbits and may be
greatest when rhinitis induces sneezing and aerosolization of secretions
(2). The bacteria can survive for days in moist secretions or water. P.
multocida gains entry to the respiratory tract primarily through the nares,
and once infection is established, may colonize also the paranasal sinuses,
middle ears, lacrimal ducts, thoracic organs, and genitalia. Occasionally
rabbits harbor chronic infections of internal tissues or organs, such as
middle ears or lungs, without any signs of rhinitis and are negative for P.
multocida by nasal culture (3).
Colonization and disease is influenced by factors related to both host and
pathogen. Different strains of P. multocida have been isolated from rabbits.
They are classified by capsular type and serotype; A:12 is the most common
in rabbits in the U.S., but A:3 and other A and D serotypes exist. More
severe disease has been associated with A:3 and D strains (4, 5). Bacterial
capsular polysaccharides are important in inhibiting phagocytosis;
lipopolysaccharides confer resistance to complement and bactericidal
activity of serum. Pili (fimbria), which are filamentous appendages
elaborated by bacteria, have receptors which may help P. multocida stick to
and colonize mucous membranes (6). Toxin production is another factor which
influences virulence; toxin produced by bacteria can cause disease by itself
and in sites removed from where the bacteria reside. This has been shown
with purified toxin from P. multocida (7). A syndrome of atrophic rhinitis
or degeneration of the nasal turbinates has been associated with
toxin-producing strains of P. multocida in rabbits (8). Both capsular types
D and A have been shown to produce toxin (9, 10). Preexisting or
simultaneous infections with other respiratory bacteria such as Bordetella
bronchiseptica, may influence the ability of P. multocida to colonize and
debilitate the tissues (3).
Ability of the rabbit to resist P. multocida infection depends, in part, on
health of the exposed mucosa, and probably on rapid production of mucosal
antibodies (IgA) which will inhibit growth of the bacteria. High levels of
humoral antibodies (IgG) are not associated with elimination of infection
but rather with chronic infection (3, 11). Thus measurement of P. multocida
IgG antibodies in serum is helpful in detecting infections inaccessible to
culture in the live rabbit. Attempts to induce immunity and protection using
bacterins, potassium thiocyanate extracts (12) or attenuated live bacteria
(13) have failed to prevent pasteurellosis over time. However, some
unvaccinated, untreated rabbits exposed to P. multocida resist infection
altogether and of those with infection a significant number resist disease.
The factors which enable that resistance to occur are of great interest.
Recent and ongoing studies involve determining whether immunity may be
induced using specific and highly purified fractions of P. multocida as
antigens in vaccines (11, 14, 15, 16) and whether these antigens can be used
SUMMARY: 10 Practical Points about Pasteurella multocida in Rabbits
1. Not all rabbits carry P. multocida.
2. If removed from sources of infection early, a rabbit may never acquire P.
3. Not all rabbits with P. multocida get sick.
4. P. multocida is still the most common cause of respiratory disease,
primarily rhinitis, in rabbits.
5. Some P. multocida strains are more virulent than others, but most
clinical laboratories cannot differentiate strains.
6. Chronic infection and disease can occur in areas of the body inaccessible
7. Hidden infections sometimes may be detected by radiology, or serology.
(See Nov. 1992 Rabbit Health News regarding serologic testing.)
8. Some rabbits are able to resist or clear mild infection without treatment.
9. Rabbits with disease due to P. multocida infection should be treated with
10. Some rabbits with chronic infections or deep abscesses may not improve
but be stabilized with antibiotics. Many owners are willing to use
antibiotics on a long term basis.
1. DiGiacomo, R.F., Garlinghouse, L.E., Van Hoosier, G.L. Jr. 1983. Natural
history of infection with Pasteurella multocida in rabbits. JAVMA 183:1172-1175.
2. DiGiacomo, R.F., Xu, Y.M., Allen, V., Hinton, M.H., Pearson, G.R. 1991.
Naturally acquired Pasteurella multocida infection in rabbits:
Clinicopathological aspects. Can J veterinarian Res 55:234-238.
3. Deeb, B.J., DiGiacomo, R.F., Bernard, B.L., Silbernagel, S.M. 1990.
Pasteurella multocida and Bordetella bronchiseptica infections in rabbits. J
Clin Microbiol 28:70-75.
4. Okerman, L., Spanoghe, L., De Bruycker, R.M. 1979. Experimental
infections of mice with Pasteurella multocida strains isolated from rabbits.
J Comp Path 89:51-55.
5. Rideaud, P., Coudert, P., Mercier, P., Hervouet, P. 1992. A Comparative
study of the virulence of Pasteurella multocida from rabbits. Fifth Congress
of The World Rabbit Association, Corvallis, OR, July.
6. Ruehl, W., Hinojoza, J., Murray, W., Rush, H., Marrs, C. 1991.
Identification and immunologic evaluation of a putative pilin in Pasteurella
multocida. AALAS Bull 30:21.
7. Chrisp, C.E., Foged, N.T. 1991. Induction of pneumonia in rabbits by use
of purified protein toxin from Pasteurella multocida. Am J veterinarian Res:52:56-61.
8. DiGiacomo, R.F., Deeb, B.J., Giddens, W.E. Jr., Bernard, B.L., Chengappa,
M.M. 1989. Atrophic rhinitis in New Zealand rabbits infected with
Pasteurella multocida. Am J veterinarian Res 50:1460-1465.
9. Suckow, M.A., Chrisp, C.E., Foged, N.T. 1991. Heat-labile toxin-producing
isolates of Pasteurella multocida from rabbits. Lab Anim Sci 41:151-156.
10. DiGiacomo, R.F., Deeb, B.J., Brodie, S.J., Zimmerman, T.E., Daniel,
G.M., Chrisp, C.E. (in press). Toxin production by Pasteurella multocida
isolated from rabbits with atrophic rhinitis. Am J veterinarian Res.
11.Zimmerman, T.E., Deeb, B.J., DiGiacomo, R.F. 1992. Polypeptides
associated with Pasteurella multocida infection in rabbits. Am J veterinarian Res
12. Lu, Y.S., Pakes, S.P., Massey, L., Stefanu, C. 1987. A potassium
thiocyanate extract vaccine prepared from Pasteurella multocida 3:A protects
rabbits against homologous challenge. Infect Immun 55:2967-2976.
13. Deeb, B.J., DiGiacomo, R.F., Bernard, B.L., Silbernagel, S.M.,
Chengappa, M.M. 1989. Field trial of a live streptomycin dependent
Pasteurella multocida serotype A:12 vaccine in rabbits. Lab Anim Sci:39:229-233.
14. Lu, Y.S., Afendis, S.J., Pakes, S.P. 1988. Identification of immunogenic
outer membrane proteins of Pasteurella multocida 3:A in rabbits. Infect
15. Snipes, K.P., Hansen, L.M., Hirsh, D.C. 1988. Plasma and iron regulated
expression of high molecular weight outer membrane proteins by Pasteurella
multocida. Am J veterinarian Res 29:1336-1338.
16. Suckow, M.A., Bowersock, T.L., Nielson, K., Janovitz, E.B., Chrisp, C.E.
1992. Stimulation of mucosal immunity to Pasteurella multocida heat-labile
toxin in rabbits. Cont Top Lab Anim Sci 31:11.