Three young adult (3 yr old) male squirrel monkeys (Saimiri sciureus)Over the course of 8 days, three monkeys presented to the veterinary service center with severe respiratory distress. The animals were sedated for examination and blood collection. Auscultation revealed severe inspiratory strider but normal sounding lung fields. The larynx appeared abnormal in all three animals but was difficult to completely visualize. One animal died following intubation and the other 2 were euthanized the following day due to poor prognosis.

Gross Description:  

Lesions were remarkably similar in all three animals. There was unilateral firm thickening of the left side of the larynx in 2 animals and bilateral swelling in 1. Lungs were normal.

Histopathologic Description:

Tissues from all three monkeys contained similar lesions. The normal histoarchitecture of the larynx is markedly altered by a necrotizing inflammatory process that expands the submuscosa and dissects between laryngeal muscle fibers. The inflammation, which consists almost exclusively of viable and degenerate neutrophils within a background of granular eosinophilic and basophilic matrix (fibrinous exudate, necrobiosis, and mucinous degeneration), widely separates and isolates muscle fibers between the intrinsic and extrinsic laryngeal cartilages. Myofiber necrosis in this region is prominent, while extrinsic laryngeal musculature is less severely affected. Multifocally, the overlying mucosa is ulcerated, partially covered by suppurative exudate, and contains expanded pockets of degenerate neutrophils and fibrin. Mucous glands are also disrupted and entrapped within the inflammation. A Gram stain revealed very low numbers of Gram negative coccobacilli, a few of which exhibited filamentous morphology.

Morphologic Diagnosis:  

Larynx: Laryngitis, necrosuppurative, severe, transmural, chronic, with necrotizing myositis and intralesional Gram negative bacteria.

Lab Results:  

CBC abnormal findings elevated WBC (11.7-13.3 K/μl, normal ref range 7.9 +/- 2.8 SD) due to increases in neutrophil counts were noted in all 3 animals.  Clinical chemistry abnormal findings elevated CPK in all three animals (2928, 5038, and 7752 IU/L, normal CPK ref ranges 562 +/- 1379.8 IU/L).  Cultures were obtained from the laryngeal lesions from 2 of the 3 animals. A pure culture of Bordetella bronchiseptica was obtained from both.


Bordetella bronchiseptica

Contributor Comment:  

Bordetella bronchiseptica can colonize and cause disease in a wide range of mammals and is associated with acute tracheobronchitis in dogs (kennel cough) and cats, atrophic rhinitis in swine, snuffles in rabbits and experimentally can produce acute pneumonias in rats (1). Members of the Bordetella genus include B. bronchiseptica, B. pertussis, B. parapertussishu and B. parapertussisov and all possess several virulence factors including filamentous hemagglutinin (FHA), fimbriae, pertactin, LPS, dermonecrotic toxin (DNT), tracheal cytotoxin (TCT), and others, but only B. pertussis has pertussis toxin (3). These factors contribute to the organisms ability to colonize respiratory epithelium, but may also contribute to cellular damage and immune regulation. These squirrel monkey cases represent a severe and very interesting manifestation of infection with this agent. Although isolation of this organism from the laryngeal lesions of these three squirrel monkeys does not definitively prove that it was the inciting cause, the lesions are consistent with those that could be produced by a highly pathogenic organism possessing such potent virulence factors. 

It is also interesting that all three squirrel monkeys presented with such similar lesions within a relatively short period of time. These monkeys were housed off site in a structure with large garage-like doors that could be opened in warm weather, yet when closed, still had space above and below that would allow access to birds, insects, rodents, and possibly wind blown sticks and leaves. The similarity in age, gender (all young males) and housing of these three animals suggest that an environmental and/or behavioral component may have contributed to their susceptibility. Because many mammals can carry B. bronchiseptica in their upper respiratory tracts yet remain asymptomatic, we cannot definitively prove that this organism was the cause of the severe laryngeal lesions. However, pure cultures directly isolated from the lesions of all three animals are supportive that this organism was directly responsible.

Other causes of laryngitis or laryngeal lesions in animals include oral necrobacillosis (calf diphtheria) due to Fusobacterium necrophorum, or laryngeal ulcers often seen in feed lot cattle (2).

JPC Diagnosis:  

Larynx: Laryngitis, necrosuppurative, subacute, focally extensive, severe, with multifocal muscle degeneration, necrosis, hemorrhage, and ulceration, squirrel monkey (Saimiri sciureus), primate.

Conference Comment:  

Bordetella spp. are aerobic, non-fermentative, gram-negative coccobacilli. There are six identified species with three of veterinary importance. 

Bordetella spp. of veterinary importance(1)
B. bronchisepticaInfectious tracheobronchitis (kennel cough) in dogs; atrophic rhinitis in pigs
B. avium Coryza in turkeys
B. hinziiCommensal in respiratory tract of chickens; opportunistic infections in humans

B. bronchiseptica has several virulence factors that promote colonization and that enable the bacterium to escape destruction in the host. Attachment virulence factors include fimbriae, and two non-fimbrial outer membrane proteins (filamentous hemagglutinin and pertactin). Replication is enhanced by production of hydroxamate siderophores and binding proteins that mobilize iron from transferrin, lactoferrin, and heme. Factors that allow escape from destruction include:(1)
  1. Adenylate cyclase toxin/hemolysin (also called cyclosin)
    1. Hemolysin binds to the host cell and facilitates entry of the adenylate cyclase domain. 
    2. Adenylate cyclase toxin causes an increase of cAMP intracellularly, which inhibits the respiratory burst of macrophages and prevents phagocytic activity of heterophils.
  2. Dermonecrotic toxin (DNT) - Intracellular bacterial toxin released upon lysis of the bacteria; inhibits the Na/K ATPase pump and causes vasoconstriction
  3. Lipopolysaccharide - Pyrogenic and mitogenic; causes macrophage chemotaxis and activation; induction of tumor necrosis factor production
  4. Tracheal cytotoxin stimulates nitric oxide production and interferes with mucociliary function
  5. Type III secretion products undefined products; inactivate transcription factor NF-_B and modulate effects on host immune response

B. bronchiseptica infections are often seen in conjunction with other bacterial or viral coinfections. It is generally considered the primary cause of kennel cough in dogs, but canine parainfluenza virus 2, canine adenovirus 2, canine distemper virus, and Mycoplasma spp. have been known to have predisposing roles.(2) Atrophic rhinitis complex generally includes B. bronchiseptica, Pasteurella multocida, Haemophilus parasuis, and viral infections including porcine cytomegalovirus.(4) B. bronchiseptica actively promotes colonization of the nasal cavity by P. multocida which in turn produces cytotoxins that inhibit osteoblastic activity and promote osteoclastic reabsorption.(4)

Some sections submitted by the contributor included an adjacent lymph node with multifocal sinus histiocytosis and erythrophagocytosis, interpreted as draining hemorrhage. 


1. Bemis DA, Shek WR, Clifford CB: Bordetella bronchiseptica infection of rats and mice. Comp Med 53:11-20, 2003
2. Caswell JL, Williams KJ: Respiratory system. In: Jubb, Kennedy, and Palmers Pathology of Domestic Animals, ed. Maxie MG, 5th ed., vol. 2, pp. 638-639. Elsevier Limited, St. Louis, MO, 2007
3. Cotter PA, DiRita VJ: Bacterial virulence gene regulation: an evolutionary perspective. Annu Rev Microbiol 54:519-565, 2000
4. L³pez A: Respiratory system. In: Pathologic Basis of Veterinary Disease, eds. McGavin MD, Zachary JF, 4th ed., pp. 481-483, 491, 542. Elsevier, St. Louis, MO, 2007
5. Mann PB, Wolfe D, Latz E, Golenbock D, Preston A, Harvill ET: Comparative Toll-like receptor 4-mediated innate host defense to Bordetella infection. Infect Immun 73:8144-8152, 2005
6. Pilione MR, Harvill ET: The Bordetella bronchiseptica type III secretion system inhibits gamma interferon production that is required for efficient antibody-mediated bacterial clearance. Infect Immun 74:1043-1049, 2006

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