Some Feline Respiratory Infections Can Cross Species Lines

Cats can transmit several different respiratory pathogens to humans. Recognizing these diseases can help veterinarians appropriately treat feline patients and counsel clients about preventing zoonotic transmission.

PLAGUE

Yersinia pestis is a gram-negative, facultative anaerobic, rod-shaped, nonspore-forming coccobacillus that causes plague.¹ Cats typically are infected by contact with infected rodents or rabbits or from the bite of an infected flea.² Bubonic plague, the most common form of plague in cats, is characterized by fever, lethargy, anorexia, and lymphadenitis in a single node or a cluster of nodes.²

Cats with primary systemic plague do not present with focal lymphadenitis, but typically develop tachycardia, diarrhea, vomiting, and respiratory distress syndrome.² They can also develop secondary pneumonic plague, which tends to cause diffuse necrotizing interstitial pneumonia.² Thoracic radiography reveals destruction of the lung architecture and, in some cases, pulmonary abscess.^2,3

Secondary pneumonic plague in cats is a serious public health risk because of the potential for respiratory droplet transmission to humans.² There has been at least one case of a human who died from primary pneumonic plague acquired from contact with an infected cat.⁴

Cats can also bring fleas infected with Yersinia pestis into the home or a shelter, where they can bite humans and other animals. Cats with suspected Yersinia pestis infection should be hospitalized, especially if they show signs and symptoms of pneumonia.² Cats should be isolated for at least 48 to 72 hours after beginning appropriate antibiotic therapy and until they improve clinically.²

TULAREMIA

Francisella tularensis is a highly infectious, gram-negative coccobacillus transmitted by a dog tick (Dermacentor variabilis), wood tick (Dermacentor andersoni), lone star tick (Amblyomma americanum) and, in the western United States, deer flies (Chrysops species).⁵ Cats are highly susceptible to infection by these routes or by consuming infected tissue.^5,6 They may be asymptomatic or present with acute fever, lymphadenopathy, anorexia, dehydration, draining abscess, oral or lingual ulcers, pneumonia, hepatomegaly, and splenomegaly.⁶

Cats can readily transmit tularemia to humans, most often through bites or scratches, but also through droplet transmission or exposure to secretions.⁵ Asymptomatic infected cats can also infect humans.⁵ Veterinarians should consider tularemia in cats with acute febrile illness, especially if they hunt wild prey.⁶

Among humans, the case-fatality rate for untreated tularemia is up to 30%.⁷ To prevent zoonotic transmission, cats with tularemia should be isolated and cases should be reported to the local public health department.⁷

LUNGWORM

Lungworm in cats includes infections with Aelurostrongylus abstrusus, Oslerus rostratus, Troglostrongylus species, Capillaria aerophila, and several Paragonimus species.⁸ Infections can be asymptomatic or may cause mild to severe respiratory disease, presenting as productive cough, mucopurulent nasal discharge, dyspnea, tachypnea, pleural effusion, pneumothorax, and respiratory failure.⁸

A. abstrusus, the most common lungworm among domestic cats, is host-specific.⁸ However, C. aerophila often infects cats and can be transmitted to humans and dogs through contact with feces containing embryonated eggs.^8,9 Paragonimus are also zoonotic, but humans are only infected by consuming raw or undercooked crabs or crayfish, the second intermediate host.⁸

Veterinarians should consider lungworm in outdoor cats, especially if they present with pulmonary hypertension and right-sided heart failure.⁸ In general, the best way to prevent lungworm infections is to keep cats from preying on hosts and counsel clients regarding fecal-oral transmission.^8,9 In humans, capillariasis causes productive cough, bronchitis, hemoptysis, fever, dyspnea, and pulmonary lesions.¹⁰

BORDETELLOSIS

Bordetella bronchiseptica, the small aerobic coccobacilli that cause kennel cough, can be transmitted from both cats and dogs to humans through respiratory droplet transmission.^11,12 However, zoonotic transmission is uncommon, unless human patients are immunocompromised.¹¹ In one review of eight human cases of B. bronchiseptica transmission over a 15-year period, three cases involved cat exposure, including exposure to a coughing cat.¹¹ The human patients typically had serious comorbidities that increased their susceptibility to infection, including chronic obstructive pulmonary disease, cystic fibrosis, and AIDS.¹¹ Symptoms in humans ranged from bronchitis to severe pneumonia, but none were fatal.¹¹

PASTEURELLOSIS

Pasteurella multocida, a gram-negative coccobacillus, is a commensal organism of the oral cavity in cats. However, P. multocida can also cause subcutaneous abscesses, secondary respiratory infections, and pyothorax in cats.¹³ Humans can acquire P. multocida infection not only from bites or scratches, but also from close contact with secretions or contaminated aerosols.¹³

In one recent report, three humans developed life-threatening P. multocida infections after providing intensive palliative care for their dying dogs and cats.¹⁴ None of these cases involved a known bite or scratch. In one case, an owner became infected after both she and her dying pet consumed honey from the same dropper.

Although such cases are rarely reported, they may be more common than the literature indicates. It is only possible to establish an epidemiologic link by taking a very detailed history, according to Joseph Myers, MD, FACP, FIDSA, professor of internal medicine at Northeast Ohio University, who reported the nonbite pasteurellosis cases.

PREVENTIVE MEASURES

Cases of cat-human zoonotic respiratory transmission underscore the importance of isolating cats whenever they are in the acute stages of respiratory infection. In addition, veterinarians should reinforce common sense messages about infection control, particularly when owners are caring for ill animals, Dr. Myers emphasized. Pet owners should consistently wash their hands before and after contact with these animals and should avoid exchanging oral secretions with pets.

Dr. Karon earned her doctorate in veterinary medicine and master’s degrees in public health and journalism from the University of Wisconsin-Madison. She was an infectious disease epidemiologist and “disease detective” (EIS officer) with the Centers for Disease Control and Prevention before becoming a full-time medical writer. She lives in the San Francisco Bay area, where she volunteers for the local Humane Society.

REFERENCES

• Garcia-Vallejo JJ, van Kooyk Y. A new cellular target for Yersinia pestis. Immunol Cell Biol. 2015;93(9):769-770. doi: 10.1038/icb.2015.60.
• Orloski KA, Lathrop SL. Plague: a veterinary perspective. J Am Vet Med Assoc. 2003;222(4):444-448.
• Watson RP, Blanchard TW, Mense MG, Gasper PW. Histopathology of experimental plague in cats. Vet Pathol. 2001;38(2):165-172.
• Doll JM, Zeitz PS, Ettestad P, Bucholtz AL, Davis T, Gage K. Cat-transmitted fatal pneumonic plague in a person who traveled from Colorado to Arizona. Am J Trop Med Hyg. 1994;51(1):109-114.
• Centers for Disease Control and Prevention. Tularemia. CDC website. www.cdc.gov/tularemia/ transmission. Published 2015. Accessed May 14, 2016.
• Zoonosis update: tularemia. American Veterinary Medical Association website. www. avma.org/News/Journals/Collections/ Documents/javma_222_6_725.pdf. Published 2003. Accessed May 16, 2016.
• Overview of tularemia. Merck Veterinary Manual website. www.merckvetmanual.com/mvm/ generalized_conditions/tularemia/overview_of_ tularemia.html. Published 2015. Accessed May 16, 2016.
• Pennisi MG, Hartmann K, Addie DD, et al. Lungworm disease in cats: ABCD guidelines on prevention and management. J Feline Med Surg. 2015;17(7):626-636. doi: 10.1177/1098612X15588455.
• Giannelli A, Passantino G, Nascimento Ramos RA, et al. Pathological and histological findings associated with the feline lungworm Troglostrongylus brevior. Vet Parasitol. 2014;204(3- 4):416-419. doi: 10.1016/j.vetpar.2014.05.020.
• Cesare AD, Castagna G, Otranto D, et al. Molecular detection of Capillaria aerophila, an agent of canine and feline pulmonary capillariasis. J Clin Microbiol. 2012;50(6):1958-1963. doi: 10.1128/JCM.00103-12.
• Wernli D, Emonet S, Schrenzel J, Harbarth S. Evaluation of eight cases of confirmed Bordetella bronchiseptica infection and colonization over a 15-year period. Clin Microbiol Infect. 2011;17(2):201-203. doi: 10.1111/j.1469- 0691.2010.03258.x.
• Mattoo S, Cherry JD. Molecular pathogenesis, epidemiology, and clinical manifestations of respiratory infections due to Bordetella pertussis and other Bordetella subspecies. Clin Microbiol Rev. 2005;18(2):326-382.
• Lloret A, Egberink H, Addie D, et al. Pasteurella multocida infection in cats: ABCD guidelines on prevention and management. J Feline Med Surg. 2013;15(7):570-572. doi: 10.1177/1098612X13489215.
• Myers EM, Ward SL, Myers JP. Life-threatening respiratory pasteurellosis associated with palliative pet care. Clin Infect Dis. 2012;54(6):e55-e57. doi: 10.1093/cid/cir975.