Microbial keratitis in East Africa: why are the outcomes so poor?

PURPOSE: Microbial keratitis (MK) is a major cause of blindness in Africa. This study reports the epidemiology, causative organism, management and outcome of MK in people admitted to a large referral hospital in Northern Tanzania, and explores why the outcomes are so poor for this condition. METHODS: A retrospective review of all admissions for MK during a 27-month period. Information was collected on: demographics, history, examination, microbiology, treatment and outcome. RESULTS: A total of 170 patients with MK were identified. Presentation was often delayed (median 14 days), and more delayed if another health facility was visited first (median 21 days). Appropriate intensive antibiotic treatment was prescribed in 19% before admission. Lesions were often severe (41% >5mm). Filamentary fungi were detected in 25% of all specimens (51% of specimens with a positive result). At discharge, 66% of affected eyes had a visual acuity of less than 6/60. Perforations developed in 30% and evisceration was necessary in 8%. Perforation was associated with large lesions and visiting another health facility. HIV infection was diagnosed in 16% of individuals tested, which is approximately twice the prevalence found in the wider population. CONCLUSIONS: Microbial keratitis is a significant clinical problem in this region, which generally has a very poor outcome. Delayed presentation is a critical issue. Fungal keratitis is a prominent cause and there is an indication that HIV may increase susceptibility. Prompt recognition and appropriate treatment in primary/secondary health facilities and rapid referral when needed may reduce the burden of blindness from this disease

Trachoma: protective and pathogenic ocular immune responses to Chlamydia trachomatis.

Trachoma, caused by Chlamydia trachomatis (Ct), is the leading infectious blinding disease worldwide. Chronic conjunctival inflammation develops in childhood and leads to eyelid scarring and blindness in adulthood. The immune response to Ct provides only partial protection against re-infection, which can be frequent. Moreover, the immune response is central to the development of scarring pathology, leading to loss of vision. Here we review the current literature on both protective and pathological immune responses in trachoma. The resolution of Ct infection in animal models is IFNγ-dependent, involving Th1 cells, but whether this is the case in human ocular infection still needs to be confirmed. An increasing number of studies indicate that innate immune responses arising from the epithelium and other innate immune cells, along with changes in matrix metalloproteinase activity, are important in the development of tissue damage and scarring. Current trachoma control measures, which are centred on repeated mass antibiotic treatment of populations, are logistically challenging and have the potential to drive antimicrobial resistance. A trachoma vaccine would offer significant advantages. However, limited understanding of the mechanisms of both protective immunity and immunopathology to Ct remain barriers to vaccine development