Trachoma Surveys by Segment (TSS) and “TT40” methods in seven districts in Kenya

Dr. Jefitha Karimurio

Supervisors: Prof. Jill Keeffe, A/Prof. Richard Le Mesurier, A/Pof. Mutuku Mwathi

Problem statement

• Kenya districts 80,000 to 1,000,000 people

• Trachoma clustered in dry areas

• In large districts (>200,000 people) clusters widely scattered.

• Endemic communities missed and non-endemic ones treated.

• Also, TT surveys in persons >15 years require large samples

The new methods

TSS method

• Districts were divided into segments with 100,000-200,000 people each (standardized intervention units).

• Areas with similar risk scores aggregated in a segment

The TT40 method

• Previous data sets re-analysed to calculate the optimum lower age limit for TT survey participants (40 years).

Results

• 7 administrative districts

• 16 segments surveyed

• 6 needed MDA x 5 years

• 4 needed it x 3 years

• 6 excluded from MDA

% of TT cases likely to be missed (n= 316 cases)

15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 900

10

20

30

40

50

60

70

80

90

100

00.60000000000000

1 2.56.3 8.9

13

21.2

26.9

37.5

46.5

61.7

70.9

88.9 89.996.2 98.7

Age of survey participants in years

% of TT cases

missed

Backlog of TT correction factor for age >40 years = 1.1

Conclusion

• TSS is an effective method to indentify the areas that need mass treatment.

• It reduced the cost of mass treatment by exclusion of the segments which do not require MDA

• TT40 method improves the efficiency of a trachoma survey

• Correction factor is required to extrapolate the total backlog