Landscape effects on the abundance of Lutzomyia longipalpis and Migonemyia migonei (Diptera: Psychodidae: Phlebotominae) in Corrientes city, northern Argentina

Ecological determinants of leishmaniasis vector, Lutzomyia spp.: A scoping review

Leishmania spp. are zoonotic parasites transmitted by phlebotomine sand flies, including those of the Lutzomyia genus, which can cause leishmaniases in both humans and dogs. Lutzomyia spp. are established in many countries in South and Central America and some areas of the southern United States, with suspected potential of these vectors to undergo further range expansion due to climate change. A scoping review was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Extensions for Scoping Reviews (PRISMA-ScR) guidelines to describe the current state of knowledge on the key ecological factors associated with Lutzomyia spp. survival, reproduction and establishment. The following electronic databases were searched for eligible studies published from 1 January 1990, to the date of search, 26 April 2023: CAB Direct (CABI), MEDLINE (via Ovid), Biological Sciences Database and Environmental Sciences Database. Primary research articles that were available in English and focused on ecological factors associated with Lutzomyia spp., such as climatic and habitat factors, geographic range, seasonality and temporality, and host abundance, were eligible for inclusion in the study. Following de-duplication, a total of 167 studies were included in Level 1 screening, 64 studies were included in Level 2 screening and 31 studies met the criteria for data extraction. Study locations included Argentina, Brazil, Colombia, Peru, Venezuela, the United States, Mexico and Canada, with some studies including multiple regions. A total of 31 different Lutzomyia spp. were assessed across these studies, with most (51.6%) of the studies focused on Lutzomyia longipalpis. Eligible studies investigated factors such as seasonality (n = 5), temperature (n = 19), precipitation (n = 13), humidity (n = 2), vegetation presence or requirements (n = 13), ecotypes (n = 7), and/or community type (i.e., urban, suburban, rural) (n = 5). Lutzomyia spp. activity was found to be higher during the rainy season, and peak when temperatures were between 20 and 25°C. Lutzomyia spp. were also found to preferentially reside in tropical or subtropical forests, which are characterised by their lack of a distinct dry season and high precipitation. This scoping review summarised the current state of the literature on the ecological factors associated with the survival, activity and reproduction of Lutzomyia spp. While there appears to be some consensus in the literature regarding some ecological requirements (such as seasonality, temperature and habitat features), overall, there is a lack of published research in this topic. This poses a significant challenge for future studies, which aim to predict the future distribution of Lutzomyia spp. in the context of climate and land use changes. Additional ecological research is urgently needed on Lutzomyia spp. given their relevance to both human and animal health.

Effect of land use change on the phlebotomine sand fly assemblages in an emergent focus of cutaneous leishmaniasis in Yucatan, Mexico

As land use intensifies in tropical forests, it is expected that species assemblages will be modified and that key functions of these ecosystems will be affected. The latter scenario is important from a public health perspective, because the land use change has been linked the outbreaks of vector-borne diseases. In this study, we evaluated the response of Phlebotominae (Diptera: Psychodidae) assemblages and their pattern of co-occurrence in four sites with different land use in an emerging cutaneous leishmaniasis focus in Yucatan, Mexico. Our hypothesis is that the conservation status (as forest cover) will positively influence the structure and composition of sand flies' assemblages. Using three different traps over a period of five months, a sampling effort of 1, 440 night-traps was performed. A total of 7, 897 sand fly specimens belonging to six genera and 10 species were collected. Our hypothesis was partially achieved since sand fly diversity increased as forest cover increased and vice versa, however random patterns of co-occurrence in assemblages were detected among sites. Even though the high abundance of sand flies in the forest fragment suggests an amplification effect, our results show that different vector species directly dominate in each site. We discuss the potential implications of the nestedness of species dominance. We suggest that in this emerging focus and under the land use gradient, Lutzomyia cruciata and Psathyromyia cratifer could play a pivotal role in maintaining the transmission cycles of Leishmania. The apparent generalist or colonialist profile of Lu. cruciata in disturbed areas deserves attention, due to the potential risk of leishmaniasis "domiciliation". This information is essential to understand the eco-epidemiology of leishmaniasis and the factors associated with its emergence in Yucatan, Mexico.

Phlebotomine Sandfly (Diptera: Psychodidae) Fauna and The Association Between Climatic Variables and The Abundance of Lutzomyia longipalpis sensu lato in an Intense Transmission Area for Visceral Leishmaniasis in Central Western Brazil

The presence, abundance, and distribution of sandflies are strongly influenced by climate and environmental changes. This study aimed to describe the sandfly fauna in an intense transmission area for visceral leishmaniasis and to evaluate the association between the abundance of Lutzomyia longipalpis sensu lato (Lutz & Neiva 1912) (Diptera: Psychodidae) and climatic variables. Captures were carried out 2 yr (July 2017 to June 2019) with automatic light traps in 16 sites of the urban area of Campo Grande, Mato Grosso do Sul state. The temperature (°C), relative humidity (%), precipitation (mm3), and wind speed (km/h) were obtained by a public domain database. The Wilcoxon test compared the absolute frequencies of the species by sex. The association between climatic variables and the absolute frequency of Lu. longipalpis s.l. was assessed using the Spearman's correlation coefficient. A total of 1,572 sandflies into four species were captured. Lutzomyia longipalpis s.l. was the most abundant species and presented a significant correlation with the average temperature, humidity, and wind speed in different periods. Lutzomyia longipalpis s.l. was captured in all months, showing its plasticity in diverse weather conditions. We emphasize the importance of regular monitoring of vectors and human and canine cases, providing data for surveillance and control actions to continue to be carried out in the municipality.