Mozzie monitor: An ovitrap mosquito gauge.

An investigation has been launched to check for any manipulation of ovitrap indices, Secretary for Health, Welfare & Food Dr York Chow says.

The move follows a complaint received earlier this week that Food & Environmental Hygiene Department staff allegedly asked its pest control contractor in Kwai Tsing to manipulate ovitrap results. The ovitrap indices in Tsing Yi fell from 36.5% in May to 0% in June and July and 1.9% in August. The figures for Kwai Chung were 16.7% in May, 17.8% in June, 4% in July and 0% in August.

Dr Chow said the indices are important for mosquito control and a lot of resources have been allocated to curb mosquito breeding, adding that public health will be affected if the results are wrong or manipulated.

Thorough investigation

"We have now required the department to have a thorough investigation to see whether there is any manipulation of the results of ovitrap reports, in particular, which districts and what types of results," he said.

"We have to find out the facts first and see whether this is the system's problem or a human problem."

Director of Food & Environmental Hygiene Eddy Chan said it is totally unacceptable if the ovitraps are tampered with as that might affect the disease vectors monitoring programme.

"If staff members of the department were found to be involved, disciplinary action will be taken," Mr Chan said.

District review

A review is being conducted at locations where substantial falls in ovitrap indices have been seen in recent months, especially those with zero readings. District staff are also asked to review the situation taking into consideration anti-mosquito operations that have been carried out in the areas. New ovitraps will be placed if accuracy of the results is in doubt. Enhanced pest control work will be conducted in the affected areas if needed.

Meanwhile, department staff and contractor's workers are urged to report any discovery of tampered ovitraps for follow-up action. Contractors should strictly follow all contract requirements in performing pest control work. Any instruction to deviate from the requirements should be reported immediately.

Since 2000, the department has been using ovitraps to detect the presence of adult Aedine mosquitoes - a Dengue fever vector - in selected areas. Since 2003, 38 locations have been selected for vector surveillance.