Zoonosis: Cat-Scratch Disease Associated with Neuropsychiatric Symptoms

What if certain mental disorders had a bacterial origin? A new study links the bacterial agent responsible for cat-scratch disease to a wide range of clinical signs associated with chronic conditions. This represents a major breakthrough in the care of infected patients.   The bacteria Bartonella causes several human diseases. Of the thirty known species of Bartonella, thirteen are considered pathogenic to humans. Among them, the most common, B. henselae, causes cat-scratch disease. Pets are also susceptible to infection by various species of Bartonella and can play a role in human infection. Thus, as its name suggests, the cat is the primary reservoir of cat-scratch disease. Infected through bites from the flea Ctenocephalides felis or through contact with contaminated blood, up to 40 to 50 percent of domestic cats may carry Bartonella henselae, depending on the region. However, dogs can also be infected by the bacteria. Bartonella infection actually causes more clinical signs in dogs than in cats, which generally remain asymptomatic. However, transmission of the infection from dogs to humans has not yet been demonstrated. Many domestic and wild animals, including cattle and rodents, can serve as reservoir hosts for various species of Bartonella. This bacterial pathogen is thus increasingly recognized as an emerging threat. Furthermore, a new study paints an even bleaker picture. New and improved methods for detecting the bacteria—which can hide within blood vessel walls and in the skin—have made it possible to identify bartonellosis in patients with a wide range of chronic diseases. Researchers at the North Carolina State College of Veterinary Medicine were able to link infection with Bartonella henselae to neuropsychiatric symptoms in humans, in addition to skin lesions. Of 33 patients with neuropsychiatric symptoms—ranging from sleep disorders to migraines, depression, and anxiety—29 were infected with Bartonella, and 83% of them also had skin lesions. The bacteria may therefore be responsible for a wide range of symptoms that can be mistaken for those of other chronic diseases, including mental health disorders as well as skin conditions. The researchers hope that this discovery will enable doctors to better identify the pathological causes of certain syndromes that may have a bacterial origin, beyond a nonspecific clinical presentation. The treatment for infected patients would then simply involve the use of antibiotics.