Insecticide Resistance Status of Aedes albopictus (Diptera: Culicidae) Populations from Cuba.

Aedes albopictus (Skuse, 1894) is one of the major vectors for arboviruses such as dengue, Zika, and chikungunya. Originally from Southeast Asia, this species has spread to Africa, Europe, and the Americas, including Cuba. This spread has been favored by its great adaptability to variable temperatures and to the resistance of its eggs to desiccation. Chemical control of mosquitoes is an essential alternative to stop arbovirus transmission, but insecticide resistance status of the Cuban Ae. albopictus populations is unknown. For this study, Ae. albopictus larvae and adults were collected from two municipalities in Havana, Cuba in 2019. Adult bioassays for deltamethrin, cypermethrin, lambda-cyhalothrin, chlorpyrifos, propoxur, and bendiocarb susceptibility were conducted according to CDC methodology. Larval bioassays for temephos susceptibility were performed following WHO protocols. Resistance profiles for α and ß-esterases, glutathione S-transferase (GST), and multifunction oxidases (MFO) pathways were constructed and analyzed. Resistance to temephos and deltamethrin was detected in Mulgoba and Plaza field populations, but resistance to lambda-cyhalothrin was only found in the Plaza colony. Plaza colony exhibited a higher expression level to all four metabolic enzymes and α-esterases and GTS were over-expressed in Mulgoba. The development of insecticide resistance in Cuban Ae. albopictus populations makes it imperative that we develop integrated control strategies to minimize the development of resistance and provide effective vector control that prevents the onset of arbovirus epidemics.

First Record of Natural Transovarial Transmission of Dengue Virus in Aedes albopictus from Cuba.

Transovarial transmission (TOT) of dengue virus (DENV) in Aedes spp. is an important mechanism for DENV maintenance in nature and may be important in initiating outbreaks. The objective of this study was to explore the occurrence of TOT in wild Aedes albopictus populations in Cuba. Mosquito larvae were collected in Cotorro municipality, Havana, Cuba, and identified to species. Fifteen pools of Ae. albopictus each containing 30 larvae were processed for DENV detection by using conventional reverse transcription polymerase chain reaction (RT-PCR) and nested PCR. Four out of 15 pools processed were positive for DENV-3, but no other DENV serotype was detected. This is the first time TOT of DENV detected in Cuban field populations of Ae. albopictus, and this suggests that this species may be an important vector of DENV in Cuba.

Vector-borne transmission and evolution of Zika virus.

Zika virus (ZIKV), discovered in the Zika Forest of Uganda in 1947, is a mosquito-borne flavivirus related to yellow fever, dengue and West Nile viruses. From its discovery until 2007, only sporadic ZIKV cases were reported, with mild clinical manifestations in patients. Therefore, little attention was given to this virus before epidemics in the South Pacific and the Americas that began in 2013. Despite a growing number of ZIKV studies in the past three years, many aspects of the virus remain poorly characterized, particularly the spectrum of species involved in its transmission cycles. Here, we review the mosquito and vertebrate host species potentially involved in ZIKV vector-borne transmission worldwide. We also provide an evidence-supported analysis regarding the possibility of ZIKV spillback from an urban cycle to a zoonotic cycle outside Africa, and we review hypotheses regarding recent emergence and evolution of ZIKV. Finally, we identify critical remaining gaps in the current knowledge of ZIKV vector-borne transmission.