Retrospective entomological and eco-epidemiological survey of a leishmaniasis outbreak in southern Spain

Leishmaniasis is a well-known vector borne disease with a high incidence in southern European countries. In Spain, <i>Leishmania infantum</i> infections typically occur as sporadic and infrequent outbreaks. However, in recent years, several outbreaks have been reported in different regions, accompanied by increasing hospitalization rates. In 2023, 31 human cases of <i>Leishmania</i> infection were reported in hospitals across 15 municipalities in Córdoba (southern Spain). Visceral leishmaniasis was the predominant form (77.4%), followed by cutaneous (19.4%), and mucocutaneous (3.2%) forms. A retrospective analysis of <i>Phlebotomus</i> captures from the mosquito monitoring network was conducted to characterize the phenology, abundance, and feeding behaviour of sand flies in the main outbreak area. A total of 22,220 sand fly specimens were recorded, with male identification revealing five species: <i>Phlebotomus perniciosus</i> (94.3%), <i>Sergentomyia minuta</i> (4.3%), <i>Phlebotomus ariasi</i> (0.08%), <i>Phlebotomus sergenti</i> (0.03%), <i>Phlebotomus papatasi</i> (0.005%) and 1.3% undetermined. Sand fly captures peaked in September, preceding the major peak in human case notifications. Most of the identified blood meals (75.0%, <i>n</i> = 163) came from Iberian rabbits (<i>Oryctolagus cuniculus algirus</i>), although blood from six other mammal species, including two samples of human origin, and one bird species was also detected. A total of 5855 female sand flies analysed, grouped into 145 pools, showed a <i>Leishmania</i> infection prevalence of 3.8%, peaking in October and November. Our findings suggest that the Iberian rabbit may play a key role in the local epidemiology of <i>L.</i> <i>infantum</i>, given its high frequency as a blood source for <i>Ph. perniciosus</i> and the elevated vector densities and infection rates observed in the outbreak area. These results emphasize the need for continuous entomological surveillance and proactive vector management, integrating the monitoring and control of potential reservoir hosts to effectively reduce transmission risk in the affected areas.