Estimating Effects of Temperature on Dengue Transmission in Colombian Cities

Background: Dengue fever is a viral disease that affects tropical and subtropical regions of the world. It is well known that processes related to virus transmission by mosquitoes are highly influenced by weather. Temperature has been described as one of the climatic variables that largely governs the development and survival of mosquito eggs as well as the survival of all insect stages. Previously, we noted that high temperatures in the Colombian city of Riohacha negatively affect the establishment of dengue virus (DENV) infection in mosquitoes; in Bello and Villavicencio cities, which have lower average temperatures, DENV infection rates in mosquitoes are positively associated with a gradual increase in temperature. Here, we test the hypothesis that a similar effect of temperature can be detected in the incidence in the human population inhabiting dengue-endemic cities in Colombia. Objective: Our objective was to evaluate the effect of climate variables related to temperature on DENV incidence in human populations living in DENV-endemic cities in Colombia. Methods: Epidemiologic data from the Instituto Nacional de Salud from 2012-2015 and 7 variables related to temperature were used to perform Spearman rank sum test analyses on 20 Colombian cities. Additionally, locally estimated scatterplot smoothing analyses were performed to describe the relationship among temperatures and incidence. Findings: Results indicated that Colombian cities with average and maximum temperatures greater than 28°C and 32°C, respectively, had an inversely related relationship to DENV incidence, which is in accordance with areas where higher temperatures are recorded in Colombia. ConclusionClimatic variables related to temperature affect dengue epidemiology in different way. According to the temperature of each city, transmission might be positively or negatively affected

Infection Rates by Dengue Virus in Mosquitoes and the Influence of Temperature May Be Related to Different Endemicity Patterns in Three Colombian Cities

Colombia is an endemic country for dengue fever where the four serotypes of virus dengue (DENV1–4) circulate simultaneously, and all types are responsible for dengue cases in the country. The control strategies are guided by entomological surveillance. However, heterogeneity in aedic indices is not well correlated with the incidence of the disease in cities such as Riohacha, Bello and Villavicencio. As an alternative, molecular detection of dengue virus in mosquitoes has been proposed as a useful tool for epidemiological surveillance and identification of serotypes circulating in field. We conducted a spatiotemporal fieldwork in these cities to capture adult mosquitoes to assess vector infection and explain the differences between Breteau indices and disease incidence. DENV infection in females and DENV serotype identification were evaluated and infection rates (IR) were estimated. The relationship between density, dengue cases and vector index was also estimated with logistic regression modeling and Pearson’s correlation coefficient. The lack of association between aedic indices and dengue incidence is in agreement with the weak associations between the density of the mosquitoes and their infection with DENV in the three cities. However, association was evident between the IR and dengue cases in Villavicencio. Furthermore, we found important negative associations between temperature and lag time from two to six weeks in Riohacha. We conclude that density of mosquitoes is not a good predictor of dengue cases. Instead, IR and temperature might explain better such heterogeneity

Geographical clustering of Trypanosoma cruzi I groups from Colombia revealed by low-stringency single specific primer-PCR of the intergenic regions of spliced-leader genes

A low-stringency single-primer polymerase chain reaction (LSSP-PCR) typing procedure targeted to the intergenic regions of spliced-leader genes (SL) was designed to profile Trypanosoma cruzi I stocks from endemic regions of Colombia. Comparison between SL-LSSP-PCR profiles of parasite DNA from vector faeces and cultures isolated from those faeces showed more conservative signatures than profiles using LSSP-PCR targeted to the minicircle variable regions (kDNA). This was also observed by analysing 15 parasite clones from one stock as well as serial samples of a same stock after in vitro culturing or inoculation into mice. Thus, SL-LSSP-PCR appears more appropriate than kDNA-LSSP-PCR for reliable typing of major T. cruzi I groups from in vitro cultured stocks and triatomine faeces. SL-LSSP-PCR grouped 46 of 47 T. cruzi I Colombian stocks according to their geographical procedences in four clusters: Cluster Cas from Casanare Department, Cluster Mg from Northern Magdalena department, Cluster Mom from Momposina Depression in Southern Magdalena and finally Cluster NW from northwestern Colombia, including Sucre, Chocó, Córdoba and Antioquia departments. Sequence analysis identified punctual mutations among amplicons from each cluster. Within Cluster Mg, sequence polymorphism allowed association with different sylvatic vector species. Novel SL sequences and LSSP-PCR profiles are reported from T. cruzi I infecting Eratyrus cuspidatus, Panstrongylus geniculatus and Rhodnius pallescens vectors.Fil: Mejía Jaramillo, Ana María. Universidad de Antioquia; ColombiaFil: Arboleda Sánchez, Sair. Universidad de Antioquia; ColombiaFil: Rodríguez, Ingrid Bibiana. Universidad de Antioquia; ColombiaFil: Cura, Carolina Inés. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres"; ArgentinaFil: Salazar, Alexander. Universidad de Antioquia; ColombiaFil: del Mazo, Jesús. Consejo Superior de Investigaciones Científicas. Centro de Investigaciones Biológicas; EspañaFil: Triana Chávez, Omar. Universidad de Antioquia; ColombiaFil: Schijman, Alejandro Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres"; Argentin