Menagerie: Bartonella henselae chorioretinitis in the setting of diverse animal exposure

Clinical record

A previously healthy 12-year-old girl presented to a rural hospital with 10 days of intermittent fevers. On Day 19 of fever, the patient was referred to a tertiary paediatric centre. On arrival, she described lethargy, headache, mild photophobia, and pain affecting her neck and back. Her medical history was remarkable for diverse animal exposure, including chickens, rabbits, horses, seven cats, one kitten, a green-cheeked conure and a pet cow. Examination revealed isolated 5 mm left-sided cervical lymphadenopathy. There was mild lumbar spinal tenderness on palpation. Cardiac examination was normal. Ophthalmoscopy was not performed at presentation due to photophobia.

Testing revealed a high C-reactive protein level and erythrocyte sedimentation rate, together with a positive antinuclear antibody (Box 1). The differential diagnoses included subacute bacterial endocarditis, occult osteomyelitis and a range of zoonoses (Q fever, cat scratch fever and rickettsial disease). Urine culture and serial blood cultures were subsequently negative.

Vague lower back pain and headache suggested possible malignancy or discitis and prompted magnetic resonance imaging (MRI) scan of the brain and spine. While the MRI scan was unremarkable, the patient continued to spike fevers ≥ 39°C. Persisting photophobia and concern for zoonotic infection led to formal ophthalmology assessment. On Day 21, her uncorrected visual acuity was 6/6 in the right eye and 6/5 in the left eye. The anterior segments were normal. The optic disc margins were blurred. The left eye showed mild vitritis and two chorioretinal lesions: the first in the superotemporal retina and the second in the inferotemporal retina (Box 2). This raised the possibility of endocarditis with embolic phenomenon, and treatment was deferred while retinal lesions were documented and transthoracic echocardiography arranged.

Echocardiography confirmed normal cardiac anatomy and no vegetation. Doxycycline was commenced on Day 27, with the provisional diagnosis of Bartonella henselae infection. The patient had rapid improvement in symptoms and resolution of fever. On Day 37, serology was available, confirming bartonellosis with total antibody titre ≥ 2028 (Box 1). Rickettsial serology (spotted fever and typhus groups) showed low positive titres, which was attributed to antibody cross-reactivity. The patient successfully completed 6 weeks of oral antibiotic therapy. At 7 weeks, the patient was asymptomatic with visual acuity of 6/6 in each eye. Ophthalmoscopy showed mild retinal scarring with partial involution of the retinal lesions and pigmentary changes (Box 2, E and F).

Lessons from practice

• Bartonella henselae infection is an under-recognised cause of undifferentiated fever, responsible for about 5% of cases in children.

• Retinal or choroidal lesions are an important clinical manifestation of infection with B. henselae and many non-infectious causes of fever. An early ophthalmic examination should be considered in all cases of undifferentiated fever in children.

• Doxycycline may be used as a therapeutic trial while awaiting serological diagnosis in patients who have a high pre-test probability of zoonotic infection due to Rickettsia or Bartonella species.

• There is no evidence to support removal of healthy animals from households; however, domestic animals should receive regular health checks and treatment for arthropod infections.