Background Visceral leishmaniasis (VL) is a deadly disease transmitted by the sand fly Phlebotomus argentipes on the Indian subcontinent, with a promising means of vector control being orally treating cattle with fipronil-based drugs. While prior research investigating the dynamic relationship between timing of fipronil-based control schemes and the seasonality of sand flies provides insights into potential of treatment on a large scale, ecological uncertainties remain. We investigated how uncertainties associated with sand fly ecology might affect our ability to assess efficacy of fipronil-based control schemes. To do this, we used a previously-described, individual-based, stochastic sand fly model to quantify how uncertainties associated with 1) the percentage of female sand flies taking blood meals from cattle, and 2) the percentage of female sand flies ovipositing in organic matter containing feces from treated cattle might impact the efficacy of fipronil-based sand fly control schemes. Principal findings Assuming no prior knowledge of sand fly blood meal and oviposition sites, the probabilities of achieving effective sand fly population reduction with treatments performed 3, 6 and 12 times per year were �5-22%, �27-36%, and �46-54%, respectively. Assuming �50% of sand flies feed on cattle, probabilities of achieving efficacious control increased to �8-31%, �15-42%, and �52-65%. Assuming also that �50% of sand flies oviposit in cattle feces, the above probabilities increased further to �14-53%, �31-81%, and �89-97%.