Potential vectors of Trypanosoma evansi in the Canary Islands (Spain): diversity, abundance, and climatic and site-related factors.

BACKGROUND

Trypanosoma evansi is a protozoan parasite responsible for surra, a disease of significant veterinary and economic impact. Mechanical transmission by haematophagous Diptera, particularly Stomoxys spp. and Tabanidae, plays a central role in its spread. The Canary Islands represent a relevant setting for this research, as several historical outbreaks of surra have been reported in local dromedary populations. This study aimed to assess the diversity and abundance of potential T. evansi vectors in the province of Las Palmas (Canary Islands, Spain), with particular emphasis on the species Stomoxys calcitrans, and to evaluate the influence of climatic and site-related factors on their distribution.

METHODS

Over a 2-year period (2023-2024), dipteran specimens were sampled using Nzi and Vavoua traps at ten locations across Gran Canaria, Lanzarote, and Fuerteventura. Morphological identification and environmental data collection were performed at each site. Generalised linear mixed models (GLMMs) were used to assess the influence of climatic and site-related parameters on species abundance.

RESULTS

A total of 23,695 haematophagous Diptera were collected, with S. calcitrans being the predominant species (99.6%). Pseudolynchia canariensis (0.4%) and Tabanus cordiger (a single specimen) were also detected. GLMMs revealed variations in S. calcitrans abundance, specifically in relation to mean temperature, mean wind speed, distance between traps and dung heaps, and trap type.

CONCLUSIONS

These findings provide a baseline for the ecological surveillance of mechanical vectors of T. evansi in island ecosystems, with particular reference to the Canary Islands. Further longitudinal studies are needed to assess seasonal dynamics and potential vector-host interactions under local conditions. However, given its high abundance, S. calcitrans appears to be the predominant species of potential epidemiological relevance and should be prioritised in surveillance and control strategies under the conditions studied.