The Modern Epidemiology of Cat Scratch Disease and Recommendations to Reduce Risk of Infection

Cat scratch disease is a zoonotic infection with the gram-negative bacteria Bartonella henselae. The disease may be spread to a human through exposure to cat fleas, or through a cat bite or scratch. Common symptoms may include a papule or pustule at the site of injury, which may be followed by systemic signs of fatigue, fever, and headache, as well as lymphadenopathy near the site of injury.¹

Cat scratch disease has been recorded throughout the United States. Data collected in the late 1970s and early 1980s indicate an incidence of hospitalizations due to cat scratch disease of 0.77 to 0.86 cases per 100,000 individuals in the general population. More recent data, reported in the year 2000, indicate a hospitalization incidence of 0.60 cases per 100,000 children.²

Through an analysis of insurance records collected from 2005 to 2013, Christina A. Nelson, MD, MPH, FAAP, and colleagues, characterized the epidemiology and burden of cat scratch disease in the United States.²

In their claims-based study, the researchers searched for the ICD-9-CM diagnosis code for cat scratch disease (078.3). Of 13,273 cases identified over the study period, 12,735 cases were managed on an outpatient basis, and the remaining 538 cases required hospitalization.²

Expressed in terms of an annual incidence, this equates to 4.5 outpatient diagnoses and 0.19 inpatient admissions per 100,000 individuals. Although the annual incidence of cat scratch disease fell from 5.1 cases per 100,000 individuals in 2005 to 4.0 cases per 100,000 by 2013, inpatient admissions remained stable throughout the study period, with the exception of a slight peak in 2008.²

Cat scratch disease is more common in children aged 5 to 9 years than in any other age group, but is also overrepresented in older adults (aged 60 to 64 years).²

Although females develop cat scratch disease more commonly than males, inpatient admissions related to cat scratch disease were observed to be more commonly males than females, in cases that occurred in 3 age groups: those aged 0 to 4 years, 25 to 29 years, and 40 to 49 years.²

Researchers estimated the total direct medical costs associated with cat scratch disease in the United States at nearly $9.8 million annually. Although this is a relatively small overall burden of disease for an entire nation, these costs are nonetheless avoidable.²

Cat scratch disease can be prevented through use of flea control measures in cats and by thorough hand washing after handling cats. Considering that children aged 5 to 7 years are the most commonly affected group, reducing feline contact with young children may also help reduce the risk.^1,2

References

1. NIH. Cat-scratch Disease. Medline Plus website. https://medlineplus.gov/ency/article/001614.htm . Accessed October 2016.

2. Nelson CA, Saha S, Mead PS. Cat-scratch disease in the United States, 2005-2013. Emerg Infect Dis. 2016;22(10):1741-1746.