Dengue: Alternatives to pesticide spraying

Saturday May 30, 2020 Written by Melinda Morris-Ponga, Te Ipukarea Society Published in Environment
Melinda's daughter Paulina and granddaughters Rose and Kavialeah learn to trap mosquito larvae. 20052942 Melinda's daughter Paulina and granddaughters Rose and Kavialeah learn to trap mosquito larvae. 20052942

The escalation of Operation Namu to rid the country of dengue is something we are very grateful for. The commitment shown by Te Marae Ora could mean an end to the current dengue season; reported cases are significantly down.

Operation Namu is not all about pesticide spraying.  Te Marae Ora are taking an integrated approach, combining the spraying with tutaka cleaning of property and mosquito-prone areas, larvae-trapping and using a good non-toxic larvicide in identified ‘wet’ areas.

The use of pesticide sprays is something I have always been uncomfortable with and it has inspired me to research alternatives. 

During the last major dengue outbreak of 2006/7, myself and a group of others asked the health ministry to stop the mass spraying of the pesticides Reslin and Malathion and use a larvicide instead, and they agreed. Both pesticides had been linked to harmful side effects to humans and the environment.

Since 2012, TMO has instead used Deltamethrin insecticide spray for mosquito control. It is approved by the World Health Organization.  However the chemical fact sheet states it is toxic if inhaled and can damage human organs.

Further studies recommend controlled use of Deltamethrin in areas away from humans, animals and especially pregnant woman.    

With lethal effects on fish and marine life it is not recommended near waterways.  

Being a neurotoxin it impacts the human nervous and immune systems with varied sensitivity on individuals, the side effects of spray exposure are listed as skin irritation, headaches, nausea. 

Other research indicates adverse effects on male sperm count. 

None of this sounds good for spraying around people. It makes you think about the safety of workers using the product and the importance of wearing full protective respirator masks, goggles, gloves, and coveralls. 

It is critical this protective gear is never washed in the home or with the family’s laundry because of toxic residue. Most chemical harm is due to a lack of product education, not being aware of the dangers and therefore not taking full precautions.  

Since 2010, Te Marae Ora has also been using the much safer, non-toxic larvicide called Bacillus thuringensis israelensis, with the brand name Vectobac. 

This bacteria is found naturally in soil, and kills mosquito larvae. Larviciding is generally known to be more effective than sprays and is used in pooled water and also on ground debris. 

It is reportedly safe for bees, fish, animals and humans – so, much safer for the people using it.  

We know Te Marae Ora uses pesticide as a last resort, because it is WHO approved and is also a more affordable option. Vectobac is more expensive but if used in correct dosage, a cost comparison is promising. We are looking into cost-cutting with direct bulk supply.

Te Marae Ora has been putting concerted effort into investigating biocontrol methods like introducing sterilised male mosquitoes into the population, effectively breeding out of the dengue-carrying mozzie, Aedes Aegypti.  This method is still in the trial stage but is also very promising. 

Of new interest is the World Mosquito Program discovery called Wolbachia bacteria, a common bacteria that lives inside insect cells. Mosquitoes infected with this bacteria show reduced ability to transmit viruses like dengue and zika to humans.

The Wolbachia bacteria is passed on to the mosquito’s offspring yet apparently does not pose any risk to humans, animals or the environment. This is a new development worth further investigation of potential environmental impacts, both good and bad.

I really like Papa Tom Wichman’s larvae traps method. This is basically just leaving containers of water around for mosquitoes to lay eggs in, but emptying them every couple of days to break the breeding cycle.

This showed me that taking responsibility in helping manage our mosquito problem was something everyone could take part in.

Details of this method can be found on Te Ipukarea Society Facebook page.  

  • This week’s article is written by TIS supporter Melinda Morris-Ponga who is concerned about the effects of spraying pesticides on human health and on our environment.


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