Why sand flies samplings of a single night are insufficient? An analysis in an urban area of northeast Argentina based on light traps.

SANTINI MS; CAVIA R; FERNANDEZ MS; SALOMÓN OD; QUINTANA MG

Reims

Congreso; ISOPS IX; 2016

Univ Reims

In recent years, in Argentina, entomological surveys to study the occurrence and abundance of sand flies of epidemiological interesthave become more frequent. Indicators of infestation levels, as the proportion of sampled sites where a particular sand fly speciesoccurs, or its abundance, were usually estimated, as well as other community characteristics, such as the number of speciespresent (richness). Some of these surveys cover large areas, so the number of nights that lights traps remains active, as well as thetotal number of light traps, has a cost in relation to human and material resources. The aim of this work was to study how theestimation of the proportion of sampled sites where a particular species occurred, the species abundances ? trap success ? andthe richness changed when the light traps remained active for more than one night. We analyzed data from four entomologicalsurveys conducted in the city of Puerto Iguazú, northeastern Argentina (summer 2011, fall and winter 2012 and spring 2014)at 49?55 sampling sites selected with worst-scenario criteria. In each site, a light trap for capturing Phlebotominae was active duringtwo consecutive nights in summer 2011, fall and winter 2012 and three consecutive nights in spring 2014. Lutzomyia longipalpisand Nyssomyia whitmani (Leishmania infantum and L. braziliensis main vectors in the study area, respectively), were thespecies more frequently captured. For these vectors, the estimation in the percentage of sites with presence increased between 23%and 75% (depending on the species and the season) with two nights compared to the estimation of a single night. The pattern forthe average number of captures showed that the estimation did not change substantially but the coefficients of variation slightlydecreased. The richness increased with the number of trap nights in all samples. Our results show the importance of avoiding single-night sampling due to the increase in the estimated percentage of sites with occurrence of vectors with a two-night protocol andin the richness also with a three night protocol. As more nights are sampled, the probability of detection of sand flies of differentspecies increases (even medically important species), and the variability between nights is compensated. However, due to costrestrictions, complementary studies are in progress to determine the optimal minimum number of nights to estimate these and othervariables in different environments and seasons. Also, other characteristics of the survey, such as the type of trap (or traps) usedand the main objective of the survey should be considered. Currently in Argentina, where operationally possible, the generalrecommendation is a three-night capture protocol.