The Department of Health and Consumer Affairs of the Government of Andalusia, in its West Nile Virus (WNV) surveillance campaign, which took place between June 14 and November 23, 2023, has captured a total of 49,629 female mosquitoes of species transmitting the virus, through the different traps located in 26 locations in high, medium and low risk municipalities.
Likewise, a weekly or biweekly collection has been carried out, depending on the locations, for the investigation of the captured mosquito species with the analysis of the presence of WNV in them using the real time PCR (RT_PCR) technique.
Added to this surveillance was the information from the 23 sampling points managed by the Pest Control Service of the Provincial Council of Huelva, which, for the first time, were also analyzed by RT-PCR during the season. In addition, the information provided by the Doñana Biological Station – CSIC was added, which has seven trapping areas in the province of Seville and executes the Arboprevent project with 400 new sampling points in different provinces of Andalusia.
Throughout the 2023 WNV transmission surveillance season, two confirmed human cases of infection with this virus were reported in Andalusia, one in the month of July in Arroyomolinos de León (Huelva) and another in August in La Puebla de los Infantes. (Seville). The first of these cases ended with the death of the affected person, who had previous pathologies.
Prior to the start of the season, the Ministry of Health and Consumer Affairs, through the Environmental Health Service of the General Directorate of Public Health and Pharmaceutical Regulation, established and published the risk map for the development and execution in 2023 of the Safety Program. Surveillance and Vector Control of West Nile Fever, through which both the administrations involved – health, environment, agriculture – and the Andalusian municipalities included in the risk map, know their starting epidemiological situation with respect to to West Nile fever, as well as the actions that must be carried out depending on whether this situation continues or evolves due to the presence of virus circulation, cases in animals, cases in humans, etc.
Thus, during the 2023 season, WNV circulation was identified on 42 occasions (mainly in Culex perexiguus), the first time being on June 14 in Los Barrios (Cádiz) and the last on November 10 in Benalup-Casas Viejas (Cádiz). The municipality in which WNV circulation was detected most times was La Puebla del Rio (Seville) and in which the greatest number of transmitting females were captured was Villamanrique de la Condesa (Seville).
This season, 16 equine outbreaks of WNV infection were declared, the first being on August 2 and the last on November 17. The outbreaks were located seven times in Seville, four in Cádiz, three in Córdoba, and one in Huelva and Málaga. Seven outbreaks of wild birds with WNV infection were also reported (4 imperial eagles, 1 Bonelli’s eagle, 1 short-eared owl and 1 red kite), mostly chicks that had fallen from their nests. The seven outbreaks were distributed from August 18 to September 28 in Jaén (1 bird), Córdoba (2 birds) and Seville (4 birds). On occasions, both equid and bird cases served to detect WNV circulation for the first time in these municipalities.
At the end of the season, 89 municipalities in Andalusia had a Risk Level (NR) 2 or higher, of which 77 have approved the Municipal Surveillance and Vector Control Plans, four have been presented and are under study, and eight have not. they have presented. This means that 91% of the municipalities affected by NR have the planned management tool approved or under study.
This 2023 season, surveillance of mosquitoes of the Aedes genus also began by installing 6 traps with smart sensors (Vectrack) that are capable of reporting, in real time, the taxonomic genus, sex and number of mosquitoes. For these differentiations, Vectrack uses different characteristics – size, flight pattern, etc. – of the insects it catches. Aedes albopictus were located in all the traps, and the presence of the dengue virus was investigated in 295 captured specimens by RT-PCR, with the results being negative in all cases.