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Spiders, lizards and frogs can help prevent dengue, Zika outbreaks

In Photo: An assortment of different spiders

SPIDERS, lizards and frogs have a few things in common. First, they eat bugs, including mosquitoes. Second, they are also food to other animals as part of the food chain.

So, instead of using chemical pesticides or releasing potentially harmful biological agents, like the so-called mosquito fish, officials of the Department of Environment and Natural Resources (DENR) said it is better to keep the population of these natural predators of pesky bugs healthy at all times.

Ecosystem functions

Environment officials said maintaining a healthy population of spiders, lizards and frogs would effectively prevent the spread of dengue, malaria and Zika virus.

Spiders weave webs, which serve as traps for insects, mosquitoes, included. On the other hand, lizards and frogs use their tongue to catch their prey. While they are predators to smaller bugs, the spiders, lizards and frogs are food to bigger animals in the wild, including birds, snakes, and other mammals. 

Director Theresa Mundita S. Lim of the DENR’s Biodiversity Management Bureau (BMB) said that, without these spiders, lizards and frogs, the insect population would go up, increasing the chances of disease outbreak.

In areas where there are reports of malaria, dengue or Zika, Lim said there is a big possibility that the population of these insect-eating species has gone down.

The absence of spiders, lizards and frogs could also affect the behavior of other species that prey on them, affecting ecological balance, Lim said.

Threats

People often harm the creepy spiders, lizards and frogs, as their sheer appearance cause people to feel nervous or afraid.

While habitat loss is the main reason for the declining population of spiders, lizards and frogs, activities that specifically target these species aggravate the situation.

Some people harvest spiders, lizards and frogs in the wild. In some areas, people traditionally harvest palakang bukid, or frogs found in rice fields, for food.

 They are also sold in some rural markets, as they have become popular bar chow to those with special craving for exotic food.

Lucrative business

On the other hand, hobbyists catch certain species of spiders and lizards, trading them as aquarium pets.

Others catch certain species of spiders for spider fighting, or sabong. Spider derby is a popular past time for young boys. It is considered a blood sport involving aggressive spiders, wherein two spiders are pitted against each other, with owners and spectators placing small bets.

One spider costs around P200 up to P500, making hunting spiders a lucrative activity, even for young boys, who go out to catch them from their natural habitats—usually on trees or bushes.

In some areas in the Visayas, even adults resort to gambling in spider fights, just like cockfights. Bets for spider fights by adults could range up to P20,000.

Some local government units have issued ordinances against spider fights, such as Negros Occidental, which considers spider fighting “a threat to public morals.”

In Bacolod City the police once issued an order warning residents against participating in spider fights, which is considered an illegal gambling.

Meanwhile, hobbyists consider certain species of lizards as aquarium pets, like tuko or gecko.

People later trade on geckos because of the belief that their internal organs have medicinal value and their meat are aphrodisiac. 

Because of its popularity and the amount of money involved in trading geckos, the DENR had issued a public advisory against trading geckos.

Harvesting wildlife, whether they are classified as threatened or not, without permit from the DENR is illegal and punishable by fine or imprisonment, or both, under Republic Act 9147, or the Wildlife Resources Conservation and Protection Act.

Invasive alien species

The DENR-BMB is set to issue a public advisory underscoring the importance of maintaining a healthy population of spiders, lizards and frogs and other insect-eating species in the wild, and advising local governments to prevent their constituents from harvesting or causing them harm in order to maintain a balanced ecology.

“With the declining population of natural predators, mosquitoes could easily breed, posing serious public-health problems,” Lim said.

 According to Lim, unlike “exotic” wildlife or invasive alien species, native species of spiders, lizards and frogs do not pose a threat to the ecosystem or other species, cautioning the public, particularly LGUs and the private sector, against releasing biological control agents without the benefit of scientific research.

Lim said release of biological agents in an ecosystem may cause more harm than good in trying to control pests, like mosquitoes, noting that the population of invasive alien species may eventually become uncontrollable, causing other species to become extinct.

Invasive fish species

Josie de Leon, the head of BMB’s Wildlife Division, said there are news reports that mosquito fish is being eyed anew as a biological control agent to prevent Zika virus from spreading. She was referring to reports that  the Subic Bay Metropolitan Authority (SBMA) is eyeing to unleash mosquito fish to control the population of disease-carrying mosquitoes in their offices. 

The SBMA had already sought for 10,000 fingerlings of the mosquito fish, locally called itar or kitaba, from the Bureau of Fisheries and Aquatic Resources (BFAR).

“Mosquito fish is an invasive alien species. Releasing them into the wild is prohibited by law, because it may adversely impact on the [local] ecological balance,” de Leon said. 

Mosquito fish was earlier used to fight the spread of dengue in certain areas. While there are no reports of its adverse impact, de Leon said there is also no proof of their positive impact in controlling mosquito population.

“We have native species of spiders, lizards and frogs that can effectively control pests like mosquitoes. We just need to maintain their population healthy,” she added.

Mosquito-borne diseases

According to DENR officials, scientific research or study on the potential impact of mosquito fish in a controlled environment should be made.

The Philippines is often besieged by reports of dengue and malaria outbreaks. Lately, the presence of Zika virus was reported in some areas. The United States’ Centers for Disease Control and Prevention (CDC) had already issued a travel advisory, especially for pregnant women, to those going to several Southeast Asian countries, including the Philippines, due to the Zika virus.

The CDC advised pregnant women who traveled to the Philippines or other Southeast Asian countries to undergo Zika virus testing. Other countries identified in the travel advisory are Brunei, Myanmar, Cambodia, Indonesia, Laos, Malaysia, Maldives, Thailand, East Timor and Vietnam.

The Zika virus has been present in Southeast Asia for some years now, with several countries reporting occasional cases of the infection. The Philippines’s Department of Health has said there were 12 confirmed reports of Zika virus cases this year. 

According to Lim, with a healthy population of spiders, lizards and frogs, the Philippines could control mosquitoes that cause deadly and costly disease outbreak. 

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