Mansonella ozzardi corneal lesions in the Amazon: a cross-sectional study

Abstract

Objectives: To characterise and confirm the presence of Mansonella ozzardi microfilariae in the cornea by biomicroscopy and corneal confocal microscopy.

Design: Cross-sectional study.

Settings: Clinical practice study in patients from rural communities in Coari city on the Solimões river, Amazonas state, Brazil.

Participants: The eyes of 212 consecutive volunteer patients were examined using a flash light and their blood checked for the presence of microfilariae by an expert microscopist. Patients with suspicious corneal lesions (characterised as nummular keratitis) were submitted to biomicroscopy, fundoscopy and corneal confocal microscopy evaluation (CCME). In two patients, a biopsy of the limbal conjunctiva adjacent to the nummular keratitis was carried out and blood collected from the surgical wound for microfilariae investigation by thick blood film examination.

Primary and secondary outcome measures: Positive correlation between corneal biomicroscopic and confocal lesions and M ozzardi microfilaremia.

Results: Of the 212 patients, 56 (26.4%) were positive for microfilaremia. 22 patients with nummular keratitis identified under flash light examination underwent biomicroscopy and CCME. Corneal lesions were positively correlated to microfilaremia (p=0.0001). At biomicroscopy, lesions were classified as quiescent or active. At CCME, lesions were categorised as circular or filiform. The associations between corneal lesions, CCME findings and microfilaremia are shown.

Conclusions: We describe M ozzardi microfilariae in the cornea and the associated eye pathology. Further studies using ocular tissue PCR and other imaging techniques would be helpful.

Figure 1

Clinical features. (Left and bottom) Central irregular ‘mottled’ appearance surrounded by an opaque halo; (right) four typical keratitis lesions with a normal translucent area between the lesions and the limbus, but no corneal neovascularisation.

Figure 2

Five different sub-epithelial circular lesions (about 80 µm in diameter) in different patients. Images are 400 µm×400 µm.

Figure 3

Filiform lesions located above the epithelium basal layer about 300 µm long and 10 µm wide, with one ‘C’-shaped end and the other tapered, all in the same patient, who had a limbal conjunctiva thick blood smear positive for Mansonella ozzardi. Images 400 µm×400 µm.

Figure 4

Microfilaria as detected by thick blood smear and corneal confocal image from a patient who underwent both tests.