An update on Leptolegnia chapmanii as control agent of vector mosquitos

PÁRAMO, MANUEL E. RUEDA; GARCÍA GARCÍA JUAN JOSÉ; LECLERQUE ANDREAS; MANFRINO ROMINA; CAVALITTO SEBASTIAN; LOPEZ-LASTRA, CLAUDIA C.; GUTIERREZ ALEJANDRA; SCHUSTER CHRISTINA

La Plata

Congreso; II Congress of the Latin American Society for Vector Ecology; 2022

Leptolegnia chapmanii (Straminipila, Saprolegniales) is an oomycete known to be a specific pathogen of mosquitos (Culicidae) and blackflies (Simuliidae) larvae, being harmless to "non-target" aquatic organisms. Biology and ecology aspects of this microorganism are known, as well as the effect of abiotic variables, such as temperature, UV radiation and water quality, on its viability and efficacy as a control agent. The zoospores produced by L. chapmanii infect larvae through their cuticle or through digestive tract, when the larvae have ingested them. As an advantage, the handling of L. chapmanii under laboratory conditions is relatively simple, since it can be kept in nutrient culture medium. The presence of L. chapmanii has been reported in the United States, Argentina and Brazil, contemplating a possible cosmopolitan distribution. In Argentina it was found in the Province of Buenos Aires at the end of the 20th century, infecting larvae of the mosquito Ochlerotatus albifasciatus. Later, in 2015, it was reported infecting larvae of the yellow fever mosquito (Aedes aegypti) in the province of Misiones. More recently, in 2021, it was found in the National Natural Park “El Palmar”, in Entre Ríos province, using floating traps with sentinel larvae. The taxonomic identification of this strain is corroborated by morphological characterization, molecular analysis, and pathogenic activity tests on A. aegypti larvae. This study contributes to expand the knowledge about the natural distribution of L. chapmanii. The isolation and identification of new strains of oomycetes would allow to expand the use of this microorganisms in microbial control strategies. Also, we are advancing in the development of a biological insecticide based on L. chapmanii, on a pilot and laboratory scale. In the biotechnological process, nutritional, economic and easily acquired substrates have been identified, viable for scaling up production. In cooperation with a private company, we are developing a massification, formulation, storage and application protocol. Furthermore, we are conducting efficacy studies under field conditions and safety studies in other "non-target" organisms. Surveys will be carried out soon in Misiones province (Argentina), and in Germany, in order to improve knowledge about the distribution of this entomopathogen, among other oomycetes of interest. We hope to expand the stock of biological material with potential for development, innovation and transfer processes to the public or private industry. The strains are deposited in the Mycological Collection at CEPAVE.