Control of the Coqui frog, Eleutherodactylus coqui

Abstract

Eleutherodactylus coqui is an invasive species whose unchecked population growth is having environmental and social impacts on the Hawaiian islands. One focus was to fine tune doses of possible toxicants to control the frogs. It was found that applied as a spray, a 1% caffeine and 0.01% pyrethrin cocktail yielded complete mortality in a single application. These concentrations could be tested in field trials. Animals treated with the caffeine/pyrethrin cocktail experienced decreases in liver and muscle glycogen and severe hyperglycemia. This is consistent with known phosphodiesterase inhibition triggering enzyme inhibitions that ultimately lead to lethality. IBMX, a caffeine analogue and potent phosphodiesterase inhibitor, when combined with pyrethrin, had a similar effect. Drugs blocking other possible modes of action such as adenosine antagonism and ryanodine receptor opening had no effect. It was therefore suggested that caffeine in combination with pyrethrin might be an effective method for controlling frog populations and the lethality of the treatment may be due to phosphodiesterase inhibition followed by eventual hyperkalemia.