MRCU Ramps Up Response to Mosquito Emergence

While you’ll likely notice improvements in the next few days, another spike is likely mid-month due to the recent rainfall. The black salt marsh mosquito (Aedes taeniorhynchus) — the main species currently causing discomfort — can also transmit heartworm to dogs and cats. Pet owners are encouraged to speak with their veterinarians to ensure their animals are protected with appropriate preventive medication.

Heavy rains and high tides have led to a surge in mosquito numbers across Grand Cayman — and the Mosquito Research and Control Unit (MRCU) is taking action.

Crews have increased both aerial and ground spraying to bring mosquito levels back down. Right now, we’re in the middle of one emergence, and another is expected to begin around 15 August, following Saturday’s downpour that left water pooling in areas that were previously dry.

MRCU teams are working extended hours to target adult mosquitoes (the ones that bite) and treat standing water to prevent larvae (baby mosquitoes) from hatching.

“We’re doing everything we can to reduce mosquito numbers as quickly as possible,” said Dr Alan Wheeler, MRCU Director. “While you’ll likely notice improvements in the next few days, another spike is likely mid-month due to the recent rainfall.”

What You Can Do

The black salt marsh mosquito (Aedes taeniorhynchus) — the main species currently causing discomfort — can also transmit heartworm to dogs and cats. Pet owners are encouraged to speak with their veterinarians to ensure their animals are protected with appropriate preventive medication.

If you notice unusual mosquito biting, please let us know by emailing mrcu@gov.ky  — include the location and the time of day when it occurred. Your feedback helps us target problem areas more effectively.

A Closer Look at the Mosquito Situation

So far this year, mosquito trap counts have more than doubled compared to the same period in 2024.

• 2024: Average of 5.8 mosquitoes per trap per night

• 2025: Average of 13.9 mosquitoes per trap per night

There have been 23 nights so far this year with high mosquito counts — that level was only seen four times last year.

To learn more, visit the MRCU website and social media platforms.