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The diagnosis of ocular TB is often presumptive and based on the presence of characteristic clinical features in conjunction with imaging and laboratory investigations. Although TB is endemic in other countries, it is relatively uncommon in North America and is therefore a less common cause of uveitis.
We describe the first reported case of ocular manifestations after avian–human transmission of TB.
A 50-year-old female was referred for evaluation of floaters in both eyes. Her past medical history was significant for uveitis in her right eye for 6 months, treated initially with prednisolone by another physician. Her best-corrected visual acuity was 20/63−1 OD and 20/25 OS. Slit lamp examination showed pigmented guttae on the corneal endothelium of the right eye. The anterior chamber of the right eye had cell grade of 0.5+ and flare grade of 1+. Examination of the lens revealed bilateral 1+ nuclear sclerosis. Dilated fundus examination revealed a blunted macular reflex and 2+ vitreous haze in the right eye, while the left eye was unremarkable and only demonstrated retinal pigment epithelial damage consistent with senile schisis (Fig. 1).
Ultrawide field fluorescein angiography of the right eye revealed diffuse late perivascular and deep choroidal hyperfluorescence with disc leakage. In addition, macular hyperfluorescence with leakage was observed. In the left eye, ultrawide field fluorescein angiography revealed an inferotemporal area of staining without disc leakage (Fig. 2). Swept-source optical coherence tomography was performed and only demonstrated a fine epiretinal membrane and intraretinal fluid in the right eye (Fig. 2).
On further history, it was revealed that the patient kept a pet African grey parrot. Bite wounds were seen on the patient's hands, which occurred throughout the year before her presentation in the clinic (Fig. 3).
The results of a complete uveitis work-up, including angiotensin converting enzyme, lysozyme, rapid plasma reagin, syphilis testing (fluorescent treponemal antibody absorption test), human leukocyte antigen-B27, rheumatoid factor, antidouble-stranded DNA, and Lyme antibody titres, were unremarkable. A purified protein derivative skin test was not performed, as the patient previously received the bacille Calmette-Guerin vaccination.
Although inflammation in the anterior segment was responsive to topical steroids, the posterior segment inflammation persisted. Anterior chamber and vitreous taps were collected in the clinic and sent to a local public health laboratory for polymerase chain reaction (PCR) testing. Both samples were positive for Mycobacterium tuberculosis. QuantiFERON-TB Gold blood testing was also performed and was positive for M tuberculosis.
The patient was subsequently referred to an infectious disease clinic for complete work-up and treatment. Chest radiograph and computed tomography were both negative for pulmonary TB. The intensive phase of her treatment lasted 2 months and involved administration of isoniazid, rifampin, pyrazinamide, and ethambutol. She remained on isoniazid and rifampin for an additional 10 months.
She was treated with a dexamethasone intravitreal implant (Ozurdex) twice during the first 6 months of follow-up for management of cystoid macular edema. Her visual acuity after resolution was 20/32 OD and 20/25 OS.
Ocular TB may present with involvement of the inside of the eye (uvea, retina, optic nerve), the surface of the eye (cornea, sclera, conjunctiva), or its surroundings (orbit, eyelids).
Particularly, tuberculous uveitis is most commonly seen and may be acquired through direct mycobacterial infection of the eye, hematogenous spread of bacteria, or an immune-mediated hypersensitivity reaction from a remote or systemic TB infection.
In patients with chronic, unexplained uveitis, the presence of risk factors for TB, signs of systemic TB infection, and the exclusion of other potential causes of granulomatous uveitis should prompt suspicion for TB.
Investigations, including vitreous tap for a suspected intraocular infection, may support a diagnosis of TB but may not be conclusive. Cultures and staining for acid-fast bacilli from an aqueous or vitreous sample require a large sample volume, have a low yield, and take a long time to complete.
After 3 months of multidrug systemic anti-TB therapy, the vitreous inflammation resolved; however, resolution of the macular edema was limited and posed a threat to permanent vision loss. Infectious disease specialists were consulted, and it was determined that the patient would benefit from local dexamethasone therapy to control ocular inflammation during concurrent TB treatment.
It is uncertain how the patient's African grey parrot became infected with TB initially. Several mycobacterium species are known to affect birds, and there have been few reports of avian–human transmission of Mycobacterium avium.
A veterinarian consultation facilitated a tracheal swab from the parrot, which was found to be positive for TB by PCR. In this case, the bite wounds on the patient's hands provided a portal of entry for the pathogen.
This is the first case describing avian–human transmission of TB leading to ocular manifestations. Ocular TB may be diagnosed clinically and in conjunction with laboratory tests that confirm the presence of the bacteria. As seen in our case, imaging with optical coherence tomography and fluorescein angiography, in combination with a thorough history, facilitates an accurate diagnosis.
Footnotes and Disclosure
The authors have no proprietary or commercial interest in any materials discussed in this article.
World Health Organization,