Mosquito extermination teams are reporting a marked drop in the number of mosquitoes capable of spreading dengue fever after a concerted campaign.

The intensified efforts by the Mosquito Research and Control Unit since January have been in response to three suspected dengue fever cases, which were confirmed by the Centres for Disease Control and Prevention last week.

No new cases have been reported since three people from West Bay and George Town contracted dengue in January, according to local public health officials.

Bill Petrie, director of the mosquito control unit, said his teams had intensified their efforts in January when the dengue cases were first suspected.

 “We took all the work crews who work on this end and intensified all our efforts in those areas. Then we expanded it outwards from those locations. That took about two weeks,” Mr. Petrie said.

Dengue fever is caused by a virus transmitted to humans by the bite of an infected mosquito.

The unit has been targeting specific problem areas rather than blanketing the entire island, an approach which Mr. Petrie said was paying dividends. “It looks like we have some good results in that we seem to be reducing the numbers of the aedes aegypti mosquitoes,” he said.

He explained that this type of mosquito, which is also capable of spreading yellow fever, is different from others as its primary food source is human blood so it lives around people, in yards and gardens by their homes, and is active throughout the day and not just at dawn and dusk like other mosquitoes.

“They only really live around humans. That is why they are so efficient as disease carriers. They usually only feed on human blood, it’s their favourite blood source. Also, it doesn’t fly very far, it doesn’t have to,” he said.

January’s cases are the first local cases reported in Cayman. Previous cases of the fever seen in Cayman have been imported.

“We are glad to say that those three persons had recovered by late January, and equally glad to say there are no more suspected dengue cases in the Cayman Islands,” said the Medical Officer of Health, Dr. Kiran Kumar.

The CDC confirmed the three patients had dengue type 2, the most prevalent strain of the virus.

Dr. Kumar said the local cases were likely caused when visitors from countries with dengue, or residents returning home from abroad, contracted mild, undiagnosed cases of the illness, who were then bitten by mosquitoes that transferred it to the three victims.

Blood samples had been sent in January from Cayman to the Caribbean Epidemiology Centre in Trinidad, and then passed on to the CDC in Puerto Rico to confirm the findings.

The results of these samples had been expected in early February, but were delayed because the CDC lab was busy dealing with an outbreak of dengue fever in Puerto Rico, Dr. Kumar said.

Public and private health practitioners are monitoring for dengue cases. “If we encounter a suspected case, we again will send samples to CAREC for testing,” Dr. Kumar said.

Health officials and mosquito control staff encourage the public to examine their gardens, patios and yards for places where standing water settles, as mosquito larvae grows in water, often in buckets, or abandoned rubber tyres, or plant saucers.

“We keep on saying over and over again to remove standing water from your yard, I know we sound like a broken record, but it’s valid and it’s useful. You might have a beautiful, clean and tidy garden, but it might just be one bucket that is the source. Just turn it upside down,” he said.

He also advised removing garbage and any other receptacles that may hold standing water from yards.

Mr. Petrie explained that aerial spraying is not very effective in dealing with the aedes aegypti mosquito. Instead, staff visit locations where mosquitoes breed and use larvicide to kill larvae and take egg samples to establish what kinds of mosquitoes are breeding in an area.

Dengue symptoms include high fever; severe headache; backache; joint and eye pain; nausea and vomiting; and rash. Most people recover without any complications, using pain relievers and bed rest.

Dr. Kumar said that once a patient has developed a fever, the infectious period lasts for only one week.