MRCU fogs areas to combat dengue-carrying mosquitoes

To the untrained eye, the thick white plumes of smoke rising from some East End and Savannah communities this week could have easily been confused for fire. However, there was no fire; the smoke is one of several tools in the Mosquito Research and Control Unit’s arsenal against the Aedes aegypti mosquito, the primary transmitter of the dengue virus.

Six confirmed cases of dengue fever, three of which were locally transmitted, have forced the MRCU to step up its spraying schedule. During the ground-level spraying, residents are advised to keep doors and windows closed to prevent chemicals from going inside. People are also advised to turn off air conditioners while spraying is taking place.

“Everything is used according to the label,” said MRCU Director Jim McNelly. “Everything is registered for use by the US EPA (Environmental Protection Agency); everything is done with properly calibrated equipment to minimise risk to people, non-targets and the environment.”

For some residents though, seeing a wall of thick smoke advancing towards, and even engulfing, them can be quite intimidating.

Lupert McDonald says he contracted dengue fever more than 40 years ago in Jamaica. – Photo: Andrel Harris

“I was working in the grounds when I saw the smoke,” said Lupert McDonald, who said he was in his 70s. “I thought it was a fire, so I ran to the other side of the house, but then the smoke came around there too, so I ran to the road.”

Told that the smoke was a result of the MRCU spraying the area because of the recent reports of dengue, McDonald, a Jamaican farmer, told of his own encounter with the virus which he contracted more than four decades ago. He said even after all that time, the pain is still clear in his mind.

“From my toes to my head, every joint hurt,” he said. “I woke up and had to change all my clothes because everything was soaking wet from the sweat.”

The spraying is conducted in two parts. First the MRCU uses an insecticide. According to the MRCU’s website, a chemical classified as ‘synthetic pyrethroid’ is applied though a method called ‘ultra-low volume’, which involves spreading between ½ and 1 ounce of the chemical per acre. The chemical compound is vaporised into a thick white fog. MRCU staff in protective gear blast the fog at vegetation and bases of houses, as well as the surrounding foliage of vacant lots. This initial fogging kills adult mosquitoes in the area.

The Cayman Compass attended the spraying of a few homes in Savannah on Wednesday. During that fogging, multiple adult mosquitoes could be seen flying from the fog. A few minutes after the spraying, the MRCU staffers then sprayed another chemical compound, that was diluted with fresh water. When sprayed, this second mixture produced a transparent liquid that coated the exterior walls of homes, as well as the surrounding plants.

An neighbourhood is fogged with vaporised insecticide to kill mosquitoes. – Photo: Taneos Ramsay

McNelly said if the MRCU is to successfully target the Aedes aegypti mosquitoes, his team will need the cooperation of the public.

“Our folks need access to properties to do their job, which, right now, is protection of the public’s health,” said McNelly.

The MRCU targets communities where the confirmed cases of dengue have been reported.

Prior to the fogging and spraying, MRCU staff go from door to door to alert people that they will be spraying around the properties. The MRCU also posts updates on its Facebook page to let residents know which neighbourhoods will be sprayed.

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  1. This individual got caught working outside unaware of the fogging. So obviously he wasn’t advised to stay inside. He wasn’t provided a protective mask. How could this happen?

    Trip Advisor:
    Murtle says:
    20/06/2018 at 3:18 pm
    I am very concerned about this information as I am currently in the caymans visiting!! Tonight we were walking back from dinner at the westing and suddenly saw a truck with a siren. We weren’t sure what it was and suddenly this truck sprayed this something literally within approximately 10-15 yards of us. My husband suddenly said mosquito spays… we all turned away and covered our faces. I was SO UPSET!!! I couldn’t believe they sprayed this with us right there. I am horrified as to what side effects—if any— we might have from this!!!???. Murtle