Randomization took place at the study mobile clinics in each village separately after baseline interview and testing, with participants selecting one of 10 colored marbles from an opaque bag containing 4 marbles assigning to the control arm, 3 marbles assigning to the low lottery prize arm and 3 marbles assigning to the high lottery prize arm. This highly transparent procedure was considered necessary for acceptability of randomization in the study population.

Village level lotteries were organized every four months and 4 lottery winners (one male and one female per lottery arm) per village were drawn. Individuals in the intervention arms testing positive for any of the two STIs did not receive a lottery ticket. They could, however, continue as study participants and thus become eligible in subsequent rounds. Individuals in the control arm were not eligible for lottery tickets, but all other study procedures were identical between the control and intervention arms. Anyone testing positive for a STI (regardless of arm) was offered counseling and free STI treatment and individuals testing positive for HIV were referred to public health clinics offering AIDS treatment for appropriate follow-up. Individual pre-test and post-test counseling following Lesotho national guidelines was provided to study enrollees at each testing interval.

Each participant received a small in-kind incentive (candles, matches, and washing powder), worth approximately $3, as a reward for their participation.

# **2.5 Data and measurement**

All participants were tested for HIV, following the Lesotho national testing guidelines, at baseline and months 16, 20 and 24.<sup>4</sup> Participants were tested for syphilis and trichonomiasis at baseline and before each lottery draw.<sup>5</sup> A baseline and end of trial survey were administered to all participants. The surveys were conducted in private with an enumerator of the same gender as the respondent to mitigate potential reporting biases. The surveys included modules on socioeco-

> 4First line testing was completed using the DetermineTM HIV-1/2 rapid test. If the result was negative, the participant was considered HIV negative. If the participant tested positive, he or she was given a second rapid test using the DoubleCheckGold<sup>TM</sup> HIV 1&2 test. Once the participant received a second, confirmatory test, he or she was considered HIV positive. If, however, the second test was negative after an initial positive result, a third test was done to determine HIV status. The third test used is the Uni-Gold<sup>TM</sup> Recombigen<sup>⃝R</sup> HIV. If the third test was positive (negative), the respondent was considered HIV positive (negative).

5For syphilis, both male and female participants were tested using the SD BIOLINE Syphilis 3.0 Rapid Blood Test. Male participants were tested for trichonomiasis with the InPouch<sup>TM</sup> TV manufactured by Biomed Diagnostics. The test provides a system for microscopic identification from urine or genital discharge. Female participants were tested for Trichomonas using the OSOM<sup>⃝R</sup> Trichomonas Rapid Test, an immunochromatographic assay that detects pathogen antigens directly from vaginal swabs.

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