Animal bites, arthropod bites and zoonoses: Case

This child has classic cat scratch disease caused by Bartonella henselae, the most common cause of chronic regional lymphadenopathy in children after cat contact. The sequence is characteristic: a primary inoculation papule appears at the scratch site within days, followed one to two weeks later by tender regional lymphadenopathy in the draining node bed, here the right axilla following a right forearm scratch from a kitten, which is the typical vector. Her well appearance, normal blood count, and ultrasound showing a necrotic node without drainable collection support a diagnosis that is usually self-limiting over weeks to months. [1]

The differential of subacute tender regional lymphadenopathy is what the examiner will probe. Reactive bacterial lymphadenitis from an infected wound, atypical mycobacterial lymphadenitis, and tuberculous lymphadenitis all enter the differential, as do lymphoma and other malignancies when the node is hard, fixed, or persistently enlarging. The kitten-scratch exposure, the inoculation papule, and the regional rather than generalised distribution strongly favour cat scratch disease, which can be confirmed by Bartonella serology, and the absence of systemic toxicity or a rapidly enlarging mass allows a period of observation. [1]

Management of uncomplicated cat scratch disease is supportive with analgesia and reassurance, because the illness resolves spontaneously in most children over weeks to months. Antibiotics are reserved for severe, prolonged, or disseminated disease, where a short course of azithromycin is the usual choice, and a suppurating node that becomes acutely painful and fluctuant may need needle aspiration for symptomatic relief rather than incision and drainage, which can leave a chronic sinus. The child is reviewed at four to six weeks to confirm the node is shrinking, with clear safety-netting advice to return for fever, spreading redness, or an enlarging mass. [1]

The bite-related teaching points round out the case. This child's kitten scratch did not require antibiotic prophylaxis in the way a deep puncture cat bite would, because the inoculation here produced a self-limiting lymphoreticular illness rather than a cellulitis, but the principles of any animal exposure still apply: an exposure history, wound care, a tetanus review, and in Australia a deliberate consideration of bat and lyssavirus exposure. Atypical presentations such as fever of unknown origin, neuroretinitis, or encephalopathy should trigger Bartonella serology, and the family can be reassured that the household kitten is the reservoir and that routine flea control reduces transmission. [2]