The Department of Environment and Natural Resources-Biodiversity Management Bureau (DENR-BMB) has warned the public against releasing frogs and fish in swamps and stagnant water to fight the dengue outbreak, as it can disrupt the ecological balance of the surrounding environment.
BMB Director Natividad Bernardino explained that placing frogs and fish 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,” Bernardino explained.
“Mosquitoes make up only less than 1 percent of the frog’s diet.”
Citing a 2016 study by biologist Jodi Rowley on the effectiveness of frogs to combat the Zika virus, she said that “mosquitoes make up only less than 1 percent of the frog’s diet”.
According to Bernardino, the cane toad, known as 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.
“When introduced to a new environment, non-native species of frogs and fishes may become invasive and alter the biodiversity of the area,” she warned.
The Convention on Biological Diversity defines invasive alien species as “organisms that are non-native to an ecosystem, and which may cause economic or environmental harm or adversely affect human health”.
“Invasive species can negatively affect human health by directly infecting humans with new diseases.”
Bernardino added that 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.
The proliferation of mosquitoes is largely attributed to environmental conditions that encourage the reproduction of disease vectors.
These conditions include dirty surroundings, stagnant man-made canals and interference to natural water flows and decline in the quality of wetlands such as streams, creek, rivers, swamps and marshes due to solid wastes, invasive plants, and structures.
“The existence of natural predators in these wetland ecosystems, given that they are kept in their natural state or properly maintained, should also help control population of mosquitoes and invasive alien species should never be an option,” she said.
In a 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.
The DENR advised the public to keep the surroundings clean, maintain unobstructed water flows of waterways, and keep freshwater ecosystems healthy to remove possible breeding grounds of mosquitoes.
