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Capnocytophaga canimorsus Infection: Causes, Symptoms, Risk Factors And Treatment

Recently, a 63-year-old man in Germany died due to multiple organ failure caused due to a rare bacterial infection called Capnocytophaga canimorsus (CC) infection. He contracted the disease after he was licked by his dog. Initially, he developed flu-like symptoms but soon it progressed to kidney and liver dysfunction and later, cost him his life. Well, who would have thought that a dog lick could cause the death of a person. This case was published in the journal European Journal of Case Reports in Internal Medicine. [1]

Soon after the man was hospitalized, he got a serious blood infection and even cardiac arrest. The antibiotics for bacteria like Haemophilus influenza and Streptococci were given to treat his condition, but all were unsuccessful. Later, on the fourth day, the culprit bacteria were identified as Capnocytophaga canimorsus, a Gram-negative bacteria normally found in the mouth of canines. According to the Centers for Disease Control and Prevention, around 74% of dogs and 57% of cats have some types of CC bacteria present in their mouth.

Causes Of Capnocytophaga canimorsus Infection

Most of the time, the bacteria in dogs and cats cause no problem to the animals as well as humans. However, in a few cases, the bacteria were held responsible for causing respiratory problems, kidney dysfunction and blood infection in humans.

Researchers say that though dogs and cats are somewhat affected by the bacteria, they are not found out in routine testing of pets as such type of bacteria requires special culture methods to get detected.

The transfer of CC bacteria from canines to humans is through their saliva. When the infected saliva of canines come in contact with the broken, burned or wounded skin of a person through scratch or lick, it gets transferred to their body and start causing fatal symptoms. Also, CC is not contagious from one human to another. It only gets transferred from animals to humans.

A study says that CC bacteria produce a toxin which affects the white blood cells of humans. Also, among the multiple strains of CC bacteria found in the oral cavity of dogs, only a few are responsible for producing such toxins. This brings out the fact that only a subpopulation of CC bacteria are pathogenic for humans and not all of them. [2]

Another study suggests that CC bacteria have immunosuppressive characteristics to resist the mechanism of removing pathogens from the body. Thus, when they enter the human body, they start feeding on white blood cells (phagocytes) and hence, develop the potential to continue living in the tissues of humans and affecting them at the same time. [3]

White blood cells are the cells of the immune system which have a defence mechanism against all pathogens entering the human body. During the CC infection when they get compromised, the body's immune system is directly affected which leads to the dysfunction of maximum number of body organs hence, causing the death of a person in most of the cases.

Symptoms Of Capnocytophaga canimorsus Infection

Symptoms of CC infection can be seen usually within 3-8 days. They are as follows: [4]

  • Severe sepsis
  • Gangrene
  • Septic shock
  • Diarrhoea or abdominal pain
  • Meningitis
  • Eye infections
  • Endocarditis
  • Fever [5]
  • Headache or confusion
  • Malaise

Risk Factors Of Capnocytophaga canimorsus Infection

People who have recently undergone splenectomy or alcohol abuse are at greater risk of getting CC infection. However, individuals who have a weak immune system are also at higher risk of getting affected by CC bacteria. Such disorders include the following: [5]

  • Chronic obstructive pulmonary disease
  • Diabetes mellitus
  • Cirrhosis
  • Hemosiderosis
  • Grave's disease
  • Ovarian cancer
  • Hodgkin lymphoma

Complications Of Capnocytophaga canimorsus Infection

Complications caused due to CC infection include the following:

  • Acute kidney failure
  • Lung damage
  • Brain damage
  • Long-term disability
  • Severe gangrene which may lead to loss of body parts
  • Death

Diagnosis Of Capnocytophaga canimorsus Infection

The CC infection is diagnosed by the following tests: [5]

  • Case history: It includes a brief history of the patient like recent bite by canines, any chronic condition, ongoing medications and many more.
  • Blood culture test: To detect the bacteria in the bloodstream
  • Antimicrobial therapy: To obtain an accurate diagnosis of the infection
  • Biochemical tests: To identify the exact species of the bacteria
  • 16S rRNA gene sequencing: For identification, quantitation and classification of microbes

Treatment Of Capnocytophaga canimorsus Infection

Treatment methods for CC infection depend on the severity of the condition. They include the following: [6]

  • Central venous catheter: They are inserted into the vein of a patient during abnormal blood clotting to transfer intravenous fluids or other dilute medications in their body.
  • Noradrenalin: To maintain the arterial blood pressure during emergency
  • Artificial respiratory system: They are suggested during acute respiratory failure or respiratory acidosis. In severe cases, tracheostomy is also suggested.
  • Broad-spectrum antibiotics: Like Penicillin G and ceftriaxone or a combination of piperacillin-tazobactam + ciprofloxacin to treat the bacterial infection
  • Continuous venovenous hemodialysis: Suggested during the kidney failure or sepsis to remove toxins from the patient's circulatory system
View Article References
  1. [1] Mader, N., Lührs, F., Herget-Rosenthal, S., & Langenbeck, M. (2019). Being Licked by a Dog Can Be Fatal: Capnocytophaga canimorsus Sepsis with Purpura Fulminans in an Immunocompetent Man. European journal of case reports in internal medicine, 6(10), 001268. doi:10.12890/2019_001268
  2. [2] Fischer, L. J., Weyant, R. S., White, E. H., & Quinn, F. D. (1995). Intracellular multiplication and toxic destruction of cultured macrophages by Capnocytophaga canimorsus. Infection and immunity, 63(9), 3484-3490.
  3. [3] Mally, M., Shin, H., Paroz, C., Landmann, R., & Cornelis, G. R. (2008). Capnocytophaga canimorsus: a human pathogen feeding at the surface of epithelial cells and phagocytes. PLoS pathogens, 4(9), e1000164.
  4. [4] Butler, T. (2015). Capnocytophaga canimorsus: an emerging cause of sepsis, meningitis, and post-splenectomy infection after dog bites. European Journal of Clinical Microbiology & Infectious Diseases, 34(7), 1271-1280.
  5. [5] Janda, J. M., Graves, M. H., Lindquist, D., & Probert, W. S. (2006). Diagnosing Capnocytophaga canimorsus infections. Emerging infectious diseases, 12(2), 340–342. doi:10.3201/eid1202.050783
  6. [6] Hloch, O., Mokra, D., Masopust, J., Hasa, J., & Charvat, J. (2014). Antibiotic treatment following a dog bite in an immunocompromized patient in order to prevent Capnocytophaga canimorsus infection: a case report. BMC research notes, 7, 432. doi:10.1186/1756-0500-7-432

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