Mosquito Research and Control Unit Update

Despite the challenges, MRCU remains optimistic as the data show mosquito numbers trending down. However, with the recent rainfall, additional mosquito emergences are expected. Mosquito numbers commonly increase around 10 days after heavy rainfall events, depending on the amount of standing water and conditions in breeding areas.

The Mosquito Research and Control Unit continues to face a tough battle against elevated mosquito numbers across Grand Cayman, but recent trap data show numbers are beginning to move in the right direction.

While mosquito activity remains higher than residents would consider comfortable, daily trap totals have decreased from the highest levels recorded this month. The latest available data show a reduction from 9,309 mosquitoes collected on 18 June to 4,723 on 22 June. Although daily numbers will continue to fluctuate, the overall trend from the recent peak is encouraging.

Weather remains one of the biggest challenges affecting mosquito control operations. The most effective window to target adult mosquitoes, which are the mosquitoes flying and biting people, begins about 15 minutes after sunset and lasts for approximately three hours.

If rain, lightning or unsafe flying conditions occur during that short period, aircraft operations must be cancelled for the evening. When that happens, the opportunity to treat adult mosquitoes from the air is missed for that day.

Aerial spraying is carried out in operational blocks. For example, the West Bay Peninsula is treated as one block, covering much of West Bay down toward George Town. Other blocks focus on areas such as North Side, East End, South Sound, Bodden Town, Newlands, Prospect and surrounding communities.

Some blocks are larger than others. When blocks are smaller, two smaller blocks may be combined and treated on the same evening. However, all blocks cannot be covered in one night, so operations are prioritised using trap data, field inspections, weather conditions and public reports.

Truck foggers also continue to support mosquito control efforts and are especially helpful in areas where ground based treatment is needed. However, truck foggers cover a much smaller area than aircraft and cannot operate effectively during rainfall. If it is raining, treatment from truck foggers will not be effective and operations may be delayed or cancelled.

Despite the challenges, MRCU remains optimistic as the data show mosquito numbers trending down. However, with the recent rainfall, additional mosquito emergences are expected. Mosquito numbers commonly increase around 10 days after heavy rainfall events, depending on the amount of standing water and conditions in breeding areas.

Mosquito control is much more than spraying. Our teams work daily to inspect breeding sites, collect and analyse trap data, carry out larviciding, conduct aerial and ground based adulticiding operations, and process public complaints to help determine where control efforts are most needed.

This work supports the Cayman Islands Government’s priority of promoting healthy, empowered people and improving quality of life for all ages by helping to reduce the impact mosquitoes have on residents, visitors and communities across the islands.

Residents are encouraged to continue doing their part by removing standing water from yards and properties, covering water storage containers, clearing blocked gutters and reporting areas with heavy mosquito activity.

The Mosquito Research and Control Unit thanks the public for its patience and understanding as teams continue working to reduce mosquito numbers across the island.