DENR warns vs releasing frogs, fishes to eliminate dengue-causing mosquitoes

Releasing frogs and fishes in swamps and stagnant water to eliminate dengue-carrying mosquitoes can disrupt the ecological balance of the surrounding environment, the Department of Environment and Natural Resources-Biodiversity Management Bureau (DENR-BMB) warned the public on Tuesday, Aug. 9.

Cane toad (DENR-BMB)

DENR-BMB Director Natividad Bernardino said placing frogs and fishes is not an effective solution to eliminate dengue-causing mosquitoes as they have a “diverse diet from plant materials to small invertebrates.”

“While adult frogs eat a variety of things, mosquitoes do not appear to be a major part of the diet of any adult frog or toad,” she noted in a statement.

She said mosquitoes make up only less than one percent of the frog’s diet, citing a 2016 study by biologist Jodi Rowley on the effectiveness of frogs to combat the Zika virus.

The director of the DENR-BMB noted that the cane toad (Rhinella marina), which is being released by some local government units supposedly to combat dengue, is one of the worst invasive alien species in the world.

Bernardino warned that introducing non-native species of frogs and fishes to a new environment may become invasive and alter the biodiversity of the area.

Invasive alien species, according to the Convention on Biological Diversity, are “organisms that are non-native to an ecosystem, and which may cause economic or environmental harm or adversely affect human health.”

Bernardino said invasive species can negatively affect human health by directly infecting humans with new diseases, serving as vectors for certain diseases, or causing wounds through bites, stings, allergens, or other toxins.

In the joint advisory on the use of frogs and fish to combat the dengue-causing mosquitoes, known as Aedes aegypti, the DENR, Department of Health, and Department of the Interior and Local Government, stressed that improving the quality of the environment is among the solutions to this water-related vector-borne disease.

"Thus, the public must keep their surroundings clean, maintain unobstructed water flows of waterways, and keep freshwater ecosystems healthy to remove possible breeding grounds of mosquitoes," said Bernardino.