Prevention and Treatment of Trachoma D. J. Gove. From University of Southampton. Now at Sun Microsystems Inc, California, USA J. D. Hawkins From University of Southampton. Now a Consultant K. Shahani, University of Southampton A.K.Shahani@soton.ac.uk akshahani@hotmail.com M. E. Ward, University of Southampton Geo Data Institute, University of Southampton

Trachoma Bacterium Chlamydia Trachomatis Infectious Eye Disease Inflamed Upper Eye Lid Geo Data Institute, University of Southampton

Trachoma Infection Young children: Reddening and irritation Older children, Adults: Scars on eyelids Trichiasis: Eye lids contract. Eye lashes turn inwards and Damage cornea Cumulative damage to cornea results in visual loss and blindness Time

Clinical Signs of Trachoma Normal tarsal conjunctiva. The dotted line shows the area that should be inspected. Notice that the blood vessels are visible. Trachomatous inflammation - follicular (TF).

Clinical Signs of Trachoma Trachomatous inflammation - follicular and intense (TI + TF) Trachomatous scarring (TS). Geo Data Institute, University of Southampton

Clinical Signs of Trachoma Trachomatous trichiasis (TT). Corneal opacity (CO). Geo Data Institute, University of Southampton

Microbiological Information About Chlamydial Infection Clinical signs appear when infection has taken hold and the disease becomes apparent. Microbiological information about body’s immune responses can detect infection well before disease becomes apparent. Microbiological information is expensive.

Global Distribution of Active Trachoma

Global Distribution of Trichiasis

Trachoma blindness. Trachoma has been eradicated from most developed Trachoma is the world’s major cause of preventable blindness. Trachoma has been eradicated from most developed countries. Trachoma is very common in poor countries. About 10% of the world’s population is at risk of blindness from Trachoma. About 84 million people have active disease. About 8 million people are visually impaired or blind d ue to Trachoma. Geo Data Institute, University of Southampton

Prevention and Treatment of Trachoma World Health Organization (WHO) SAFE strategy for controlling Trachoma Surgery for advanced trachoma Antibiotics Facial cleanliness Environmental improvements. Geo Data Institute, University of Southampton

Prevention and Treatment of Trachoma Morocco has succeeded in controlling Trachoma through using SAFE strategy 80 % 60 % 40 % 20 % 0 % % of active disease Five regions of Morocco Geo Data Institute, University of Southampton

Clinical Model

Microbiological Model

Infection Dynamics Time Force of infection Infected / Diseased Susceptible Resistance Susceptible Duration of infection Duration of resistance Incubation period Duration of clinical signs Time Point of infection

Data and Information for Models Data from various sources Demography: Life Table. Birth rate by age of woman. Longitudinal surveys of the population in the village of Jali in Gambia for Clinical and Microbiological Models. Sources: Dr Robin Bailey, Professor David Mabey, Professor M E Ward Infection probabilities by age Duration of infection by age Probabilities of consequences of infection etc.

Data and Models: Demographics

Recurrence of active disease following chemotherapy Data and Model Recurrence of active disease following chemotherapy 12% 9.6% 7.2% 4.8% 2.4% 0% Prevalence 0 50 150 200 250 Time (Weeks) Jali data Model

Data and Models: Clinically Active Disease

Data and Models: Scarring

Data and Models: Trichiasis

Chemotherapy Chemotherapy was modelled as an immediate reduction in the force of infection Geo Data Institute, University of Southampton

Chemotherapy: Single Treatment Prevalence of Infection Time in Weeks

Treating 0 – 15 age group is almost as beneficial Chemotherapy Treating 0 – 15 age group is almost as beneficial as treating the whole village. Chemotherapy by itself will not eradicate Trachoma in Jali and other areas with high prevalence

Repeated Chemotherapy Treatments: Age 0-15 Prevalence of Scarring 0 200 400 600 800 1000 Time in Weeks

Repeated Chemotherapy Treatments: Age 0-15 Prevalence of Trichiasis Time in Weeks

Vaccination Vaccines are not available at present Models can provide some guidance about the “type” of vaccine that would be effective. Vaccine parameters Duration of protection. e.g. 5 years Effectiveness of protection: Reduction in infection probability e.g. Infection probability is reduced to 70% of its base value Vaccination is modelled as increased resistance decreasing the number of susceptibles

Vaccination with various vaccines. Time to return to previous levels of infection with various vaccines. Vaccine effectiveness 0-5 age group 2.5 year 5 year 30% 2 years 50% 4.5 years Vaccine effectiveness 0-15 age group 2.5 year 5 year 30% 4.5 years 50% 7 years

Socio-Economic Actions Effect of socio-economic actions is modelled as a reduction in the force of infection Examples of socio-economic actions Actions that decrease / eliminate poverty Easy access to sufficient clean water Improved hygiene There is no high quality data for estimating the effects of particular socio-economic actions Geo Data Institute, University of Southampton

Force of Infection Reduced to 90% of Previous Chemotherapy Prevalence of Infection Time in Weeks

Changes in Force of Infection for age 0-15 Prevalence of Infection Time in Weeks

Concluding Remark Appropriate data + Detailed models for evaluating treatment strategies can evolve good strategies for eradicating Trachoma Geo Data Institute, University of Southampton