Mosquitoes in the Cayman Islands

The short answer

• Expect some bites, mostly around sunrise and sunset in the wet season, mid-May to October. Swarms come in waves after high tides and rain flood the wetlands.
• Swamp mosquitoes fly miles from the wetlands into neighbourhoods. MRCU's September warning singled out the eastern districts.
• Use DEET or picaridin on top of sunscreen, and tip out standing water at home every week.
• A government unit fights them. The Mosquito Research and Control Unit (MRCU) treats swamps from the air and streets by truck; WhatsApp 936-8503 to see planned operations.
• No dengue so far in 2026, and no 2026 case of Zika, chikungunya or Oropouche announced.

Will I get bitten?

By season

Mosquito season follows the wet season, which the National Weather Service puts at mid‑May to October. The nuisance is the black salt marsh mosquito, Aedes taeniorhynchus, whose eggs lie dormant in wetland soil. When high tides and rain flood the wetlands, they hatch together and a wave of adults emerges several days later. The dry season is generally quieter, but MRCU says surges can still happen: a high tide can flood coastal wetlands and trigger an emergence of salt marsh mosquitoes, and rain adds breeding sites. In 2026 MRCU issued mosquito warnings in July, August and late September. Its light traps on Grand Cayman caught about 41,000 mosquitoes on 3 October, falling to about 10,000 by 7 October.

By place

• Near wetlands: the source. MRCU says swamp mosquitoes can travel several miles from them into homes and businesses.
• The Eastern Districts: MRCU's September 2026 warning said they could expect some of the highest levels.
• Cayman Brac and Little Cayman: included in that warning too. A four-person MRCU team works there on the ground, backed by aircraft from Grand Cayman when needed.

When they come out

• Black salt marsh mosquito (wetlands): most active around sunrise and sunset; in a surge it also bites by day in shade near trees and shrubs. It doesn't spread disease to people, but it can give dogs and cats heartworm.
• Aedes aegypti (around homes): bites mainly in early morning and early evening, and breeds in containers such as buckets and tyres. It only flies a few blocks in its lifetime. This is the species that can carry dengue, Zika and chikungunya.
• Culex quinquefasciatus (around homes): bites in the evening and breeds in dirty water and cisterns.

How to avoid bites

• DEET: 20% or more gives several hours' protection. A higher strength lasts longer, with little gain above about 50%.
• Picaridin: about 20% protects for 8 to 12 hours.
• Where to buy: DEET sprays are on the shelves at Foster's and Hurley's, and Hurley's also stocks a 20% picaridin spray.
• Sunscreen first, repellent on top. Our reef-safe sunscreen guide covers the first half.
• Children: spray on your own hands, then apply to the child's face. Keep it off their hands, eyes, mouth and any cuts.
• Plant-based: only oil of lemon eucalyptus is proven, shown as OLE or PMD on the label. Pure lemon eucalyptus essential oil is not the same and isn't recommended. OLE and PMD products aren't for children under 3.
• Clothing: loose long sleeves and trousers. Permethrin-treated clothing keeps working through several washes; never put permethrin on skin.
• Indoors: keep window and door screens in repair, and use air conditioning if you have it.
• At home: once or twice a week, walk your property and empty anything holding water: buckets, plant saucers, tyres, toys. Cover water-storage containers.
• Pets: keep dogs and cats on heartworm prevention.
• What doesn't work: repellent wristbands, sound-emitting devices, and taking garlic or vitamin B.

What MRCU does

The Mosquito Research and Control Unit is a government unit based on Red Gate Road in George Town, with its own team on the Sister Islands. Its main tools:

• Surveillance: trapping adult mosquitoes, checking water for larvae and running field surveys, which decide where it treats. It also checks that its insecticides still work.
• Larviciding: killing larvae is its mainstay against swamp mosquitoes, and aerial larviciding is done in daylight. In September 2026 its aircraft spread a granular larvicide (Natular G30) across Grand Cayman from West Bay eastward in low passes.
• Fogging and aerial spraying: truck, thermal and backpack fogging on the ground, and aerial treatment of adult mosquitoes. Truck fogging and aerial adult treatments usually happen shortly after sunset, when the target mosquitoes are active; ground teams also thermal-fog targeted areas by day when needed. Everything depends on the weather.
• How often: there's no fixed number of fogging visits per neighbourhood. MRCU decides from trap counts, field inspections, residents' reports, breeding conditions and weather, and must leave the intervals product labels require between applications.
• Water control: sluice gates and canals manage swamp water levels, and mosquitofish are released to eat larvae.
• Aircraft: one returned on 20 October 2026 after its mandatory 100-hour inspection. The second had not returned to service as of 29 October, MRCU said.
• Drones: MRCU's newest tool is a drone programme.

No genetically modified mosquitoes

MRCU doesn't use genetically modified mosquitoes and has no plans to, and it isn't currently using or trialling sterile-insect or Wolbachia methods. The Oxitec project's releases ended in 2018 and the partnership formally ended in January 2019. Those releases targeted Aedes aegypti, not the swamp mosquito behind much of the seasonal biting.

See when and where it's spraying

Send a WhatsApp message to 936-8503. The automated reply links to MRCU's control activity page, which shows planned operations and start times on a map. Updates also go out on the MRCU WhatsApp channel and its social accounts, all listed at linktr.ee/CaymanMRCU.

Report a problem

Use "Report biting problem" on the control activity page (drop a pin, rate the biting 1 to 5), or email MRCU@gov.ky or WhatsApp 936-8503 with your location, a contact number and details of the biting. A report doesn't guarantee a fogging visit: MRCU assesses it and decides the response. The office line is 949-2557, Monday to Friday, 8:30am to 4:30pm.

Is the spraying safe?

MRCU says all the chemicals it uses are safe, registered and applied according to strict guidelines, and it publishes the labels and safety data sheets for its products. All but two are registered with the US EPA. If you keep fish ponds or beehives near a planned treatment, contact MRCU beforehand for advice on the product being used. Beekeepers can give MRCU their hive locations and contact details, and evening adult treatments help reduce overlap with the hours bees forage. For pets, call MRCU.

A short history

In 1834 the Governor of Jamaica said that Grand Cayman's mosquitoes amounted to "quite a national misfortune". MRCU was set up in April 1965 under Dr Marco Giglioli; work on the Sister Islands began in 1970 and the first aerial campaign flew in 1971. Even in 1974, one trap in Bodden Town caught a record 793,103 mosquitoes in a single night. MRCU's history page has the full story.

Dengue, Zika, chikungunya and Oropouche

Current status: Timothy McLaughlin, senior public health surveillance officer at the Public Health Department, told the Cayman Compass on 10 October 2026 that Cayman had not recorded any dengue cases this year. No 2026 case of Zika, chikungunya or Oropouche has been announced (checked 28 October 2026); the last official figure, for 2025, was no confirmed cases of any of these viruses. All four are notifiable diseases, which doctors must report to Public Health.

• Dengue: four related viruses spread by Aedes aegypti. A second infection with a different one raises the risk of severe illness. The last locally acquired cases were in 2023: of 18 confirmed by November that year, 9 were caught in Cayman.
• Zika and chikungunya: also spread by Aedes aegypti.
• Oropouche: spread mainly by biting midges, and by some mosquitoes. Cayman recorded one imported case in 2024, with no local spread. There is no vaccine or medicine for it.

The region is busier. In October 2026 the Pan American Health Organization reported rising dengue in the Caribbean and chikungunya re-emerging in places that hadn't seen it for years. If you develop a fever, severe headache, body aches, nausea or a rash after travelling somewhere with dengue, see a doctor and mention where you've been.

Questions people ask