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Team helping to reduce risk of Zika virus

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On the hunt: Dwaine Swan, Vector Control's Paget inspector, left, and general foreman Tracy Woolridge inspect a ditch in case mosquitoes are breeding in the stagnant water (Photograph by Lisa Simpson)

The Zika virus has made global headlines in recent days but Bermuda's Vector Control team have already been doing everything in their power to minimise the health risks from mosquitoes. The Department of Health's Vector Control experts say they are on top of the island's mosquito problem, but now is not the time for complacency.After the mosquito-borne Zika virus was declared a global health emergency by the World Health Organisation, the local team is reminding the public to do their part by removing standing water from their properties.While there have been no confirmed cases on the island, the Department of Health said last week that it was looking at whether two patients needed to be tested for the virus.Armell Thomas, the programme manager for Vector Control and Port Health, said: “We have one of the best mosquito programmes in the world. “We don't have all the answers but geographically we are small enough to do such a good job to control these mosquitoes and vector-borne diseases as we possibly can for now.”But he said the public and business owners could assist by getting rid of standing water and any items that could collect water and pose a threat.“That's the only way the public can help us and we will continue to monitor our programmes and surveillance,” Mr Thomas added. “It will really help us to eliminate the Zika virus from actually coming here.”While the Aedes aegypti mosquito, which is linked to the Zika outbreak, has been eradicated in Bermuda, Mr Thomas said the Aedes albopictus mosquito was also capable of carrying the virus, as well as dengue and chikungunya.However, general foreman Tracy Woolridge said: “I'd advise the public not to panic because Vector Control is on top of it.”Zika virus emerged in Brazil last year and, according to the WHO, has been transmitted in at least 30 countries. As many as 1.5 million people have been infected, with pregnant women said to be most at risk because of its suspected links to deformations in infants.Since the outbreak made international headlines, Vector Control has seen an increase in calls and requests for information. Teams are on alert and conduct two- to four-mile radius sweeps of the workplace and home of anyone suspected of having a vector-borne disease.“We're very serious in our programme,” Mr Thomas said. “We're not waiting for a virus to come out. “That's probably what makes us one of the best surveillance programmes out there because of the fact that we already do it.“Any virus that comes out, the public is going to be worried and asking questions. “A lot of people don't understand exactly what we do. This is a crucial time to explain to the public what we've been doing prior to these diseases.”Since the late 1990s, Vector Control, with the help of other government departments such as Parks and Works and Engineering, has been running a “robust” surveillance programme designed to monitor and track the Aedes mosquito in Bermuda. The team has more than 600 ovitraps, which mimic the preferred breeding site for container breeding mosquitoes such as Aedes albopictus , placed in strategic locations around the island. These are checked for mosquito eggs on a weekly basis and the results are mapped on a computer programme.Mr Thomas said: “If there's anything over 50 eggs on a stick we're going to go out and seek and destroy and we monitor it for a period of time.”They do door-to-door checks and inspect properties close by for problem areas.The team also uses larvicides and insecticides to control mosquito populations before they have hatched and as adults, and a spray unit makes regular trips around the island.“In Bermuda, we try to eradicate the mosquito at the pupae stage,” Mr Thomas said. “We try not to wait for it to become an adult.”Because mosquitoes breed in stagnant and brackish water, the team also monitors and clears canals and ditches on a regular basis, as well as derelict or unfinished pools and tanks. Guppy fish have been introduced to bodies of water that could pose a threat. “It's very important to keep these canals clear and not take the fish out because that's our number one defence against mosquitoes,” Mr Woolridge said.Mr Thomas also reminds the public to ensure that screens are fitted on their tank overflow pipes to stop mosquitoes from getting in. Aquatain, a silicone-based liquid that forms a film on top of water to stop mosquitoes breeding, can also be used in small bodies of standing water such as bird baths.Mr Woolridge stressed the importance of disposing rubbish properly because even a bottle cap could hold enough water for a mosquito to lay eggs.“It's very important that people don't throw trash in trees because sometimes we miss that,” he added.A further threat is posed by bromeliad plants, which can collect water in their cups and provide an ideal location for mosquitoes to lay their eggs.“I call that plant my worst enemy,” said Dwaine Swan, the Vector Control inspector for Paget. He urged people to either drill a hole in the plant to let water drain out, keep them in pots so that the water can be tipped out, or remove them entirely.The team is urging the public to follow advice about avoiding mosquito bites when travelling to affected areas and to seek medical advice immediately if they suspect they have the virus.• For more information, contact Vector Control on 278-5397

Pest control: Dwaine Swan, the Vector Control inspector for Paget, holds up one of more than 600 ovitraps that are placed around the island and monitored weekly for mosquito eggs (Photograph by Lisa Simpson)
Breeding ground: Dwaine Swan, the Vector Control inspector for Paget, points to a bromeliad plant, which he describes as his “worst enemy”. The plant holds water in its cup, which can provide an ideal location for mosquitoes to lay eggs (Photograph by Lisa Simpson)
Control measures: Dwaine Swan, Vector Control’s Paget inspector; Tracy Woolridge, the general foreman; and Armell Thomas, the programme manager for Vector Control and Port Health, inspect a derelict pool. It has been pumped twice and fish introduced to control the mosquito population. Other measures that can be taken include creating a hole in the bottom of the tank or pool so that water can drain out (Photograph by Lisa Simpson)
<p>Species carrying vector-borne diseases</p>

Bermuda has four species of mosquito that can carry vector-borne diseases, according to experts at Vector Control.

However, while the culex mosquito, the eastern salt marsh mosquito and the black salt-marsh mosquito are a “nuisance”, the Aedes albopictus is more aggressive and more likely to carry Zika, dengue and chikungunya.

“The Aedes family normally carries the Zika virus,” Armell Thomas, the programme manager for Vector Control and Port Health, told The Royal Gazette. “The one we have, the Aedes albopictus, does not like the Zika virus for some reason but it can carry it.”

Aedes albopictus, also known as the tiger mosquito, can be told apart from other species by several characteristics. It is smaller than the salt-marsh mosquito that is often found close to marshy areas, according to Mr Thomas.

They also lay eggs in different patterns, said general foreman Tracy Woolridge.

“The culex lays her eggs on top of the water in a raft but the Aedes albopictus lays her eggs as single eggs.”

“The Aedes is a very aggressive mosquito,” he added. “With the culex mosquito — that's the common house mosquito — and even with the salt marsh, they will buzz around you and they are a nuisance, but with the Aedes mosquito, she doesn't buzz, she bites around your ankles. She likes dark places. That's why it's hard to detect.”

Mr Woolridge said mosquitoes need only a small amount of water to breed, which is why it was “very important to empty out water around your yard”.

“Without water they're not going to multiply,” he added.

Mosquitoes take an average of seven days to hatch and can fly up to about two miles, but this can vary from species to species.

Only female mosquitoes bite, Mr Wooldridge explained, because they are looking for a “blood meal”.

“That's how she gets the protein for her eggs,” he said.

But he added that mosquitoes also have a purpose, with the male playing an important role in pollinating plants.