Geo Data Institute, University of Southampton

1. 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

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

3. 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

4. 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).

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

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

7. 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.

8. Global Distribution of Active Trachoma

9. Global Distribution of Trichiasis

10. Trachoma • 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

11. 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

12. 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

13. Clinical Model

14. Microbiological Model

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

16. 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.

17. Data and Models:Demographics

18. 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

19. Data and Models: Clinically Active Disease

20. Data and Models: Scarring

21. Data and Models: Trichiasis

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

23. Chemotherapy: Single Treatment Prevalence of Infection Time in Weeks

24. 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

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

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

27. 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

28. Vaccination Time to return to previous levels of infection with various vaccines.

29. 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

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

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

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