Malathion which is being used in the fogging of mosquitoes is not harmful to the public, according to the Head of the Vector Control Unit, Dr Horace Cox and in the wake of the growing concerns over the Zika virus the campaign is being stepped up countrywide.
Malathion, an organophosphate insecticide, is being mixed with diesel fuel which is used as an agent to enable dispersal. The mixture is then transformed into a dense vapour to kill adult mosquitoes. This method is currently one of several measures employed across the country as instructed by the Ministry of Public Health in an effort to prevent the mosquito-borne Zika virus being transmitted.
The Zika virus is spread by the bite of an infected Aedes aegypti mosquito. Its symptoms include fever, joint and muscle pains, headaches, rashes, and conjunctivitis. These symptoms usually appear within three to twelve days following the bite of an infected mosquito and last for four to seven days. It has sparked deep alarm, particularly in South America, because of its perceived linked to microcephaly and Guillain-Barre Syndrome cases in Brazil and Colombia.
And while some have expressed concern about the potential health risks that malathion may have on humans, Head of the Vector Control Unit of the Ministry of Public Health, Dr. Cox maintains that the use of malathion in the fogging exercise does not pose any risks to the health of residents.
He contended that his agency, along with others across the Caribbean have been using the chemical for a long time, adding that its use has not been discouraged by either the Pan-American Health Organization (PAHO) or the World Health Organization (WHO).
“I know some persons have the reservation about the use of it, but as far as we know we are not breaching any protocol by using it,” Dr Cox said.
Although the general public would not be affected by the malathion fog, Dr. Cox advised that those who have existing respiratory conditions such as asthma, as well as young children and the elderly follow the guidelines that would have been communicated through the media and via public service announcements for safety reasons.
The doctor stressed that a lot of effort has gone into ensuring the safety of this particular group of persons including the deployment of a team which is instructed to make house visits, notifying the households of scheduled fogging.
“We are aware that the smoke has the potential to trigger asthma attacks, therefore we placed a lot of emphasis on the notification process,” he said.
Emphasis is also placed on the safety of those who are involved in the fogging exercise.
He said that overalls, protective gloves and respirators once used properly during fogging are enough to offer the necessary protection. As an additional measure, each individual is given a meal before undertaking the exercise since they would be going up against the strong scent of malathion.
Dr. Cox acknowledged that while malathion is effective in mosquito control, it indeed has some negative implications on existing ecosystems. He stressed however, that at the end of the day, there is no “perfect chemical or drug.”
Experience
Though the fog kills the adult mosquitoes, Dr. Cox explained that the chemical has no effect on the larvae and pupae stages of mosquitos. Therefore, instead of an area being fogged once, residents should expect to experience the exercise at least twice. This process, once done correctly, can result in the mosquito population decreasing by 60%, the doctor explained.
“We know that there are some agents out there that may not be as offensive in terms of the odour, so we will be looking at these to see how feasible it would be to implement in our setting. But because of several things, it may not be feasible; two of the things we have to look at specifically are the environmental setting and cost effectiveness, but these are what we hope to assess in the near future,” he explained.
Additional assessments are being conducted to determine whether if after such a lengthy use, mosquitoes are becoming resistant to malathion. Dr. Cox explained that in some Caribbean countries malathion is used for extended periods, then replaced with another chemical before being eventually reintroduced with the hope of
decreasing the possibility of mosquitoes being resistant to the chemicals.
However, he went on to say that sometimes such practices could result in a scenario where the mosquito becomes resistant to both chemicals over time.
He said, “We have been looking at it and some advice that we have received is that while resistance to malathion would not occur immediately, you will have a scenario where resistance to both chemicals would have developed eventually. Which would have other repercussions for developing countries such as Guyana in that if something like that were to happen, we will find ourselves having to resort to more expensive approaches.”
When questioned on the status of other regions, Dr. Cox explained that the health system is looking to become more decentralised. He went on to say that the policy at the moment is that each region takes control of their regional health activities while supervision would be done by the central arm.
For areas like Parfait Harmonie and Meten-Meer-Zorg on the West Coast and West Bank of Demerara respectively, he noted that the team has offered support to start off the exercise as residents have continuously complained about mosquito infestation being “very bad”. He said that since they are expected to provide extensive coverage to all the regions, it is often challenging since they don’t always have the resources available.
“It is difficult because we don’t have all the resources that allow people to feel our presence right away. Sometimes, because we may have communities that need our immediate attention as a result of some cases of dengue or malaria, we may go there and just target the community and then go according to schedule as we come out,” he said, before adding “If they haven’t seen the team as yet, my expectations are that they will see the team in the near future because the activities are ongoing.”
The vast area and terrain to be covered are also issues.
“We would have started in Moruca (a sub-district of Region 1) but the area is vast and then the challenging thing is that it’s not like Georgetown where you travel through a street and you touch 40 houses. These people are scattered, so you find that you may be fogging an area where there are only three houses,” he related.
As a result, they have moved to target the densely populated areas and locations where there has been a fair number of reported cases of dengue or other mosquito-borne illnesses.
He explained that while fogging has commenced in Regions 1, 7, 8 and 9, the agency has been devising plans on how best other vector control measures can be implemented in the hinterland area.
“As I said, fogging isn’t the only thing that is being done, it is just one of the vector control measures which is complemented by several other things including the use of insecticide residual sprays which is administered inside the home and kills the
mosquito upon contact and
larvicide which deals with the larvae stages of the mosquito with great emphasis being placed on the control of and the elimination of the breeding sites,” he said.
The doctor further stated that getting this message out to the general public remains a key point in the fight against the spread of any mosquito-borne viruses since everybody can play their part which would in turn complement the measures that have been implemented by the Vector Control Unit.
The distribution of treated mosquito nets also continues and over 6000 nets have been shared so far to antenatal clinics in both the hinterland and on the coast.
Dr. Cox highlighted that this distribution caters to both public and private medical institutions, adding that this move not only targets the Zika virus but also other mosquito-borne diseases especially in Regions 1,7,8 and 9. “We want to ensure that the baby is a healthy baby and is a product of a healthy pregnancy…. it is our obligation to ensure that every mother sleeps under a treated net,” he related.
He said that the technical team would have been able to adapt to language barriers in indigenous communities over time since they are mostly involved in the field work with additional assistance sometimes being given by village Toshaos. Apart from that, Dr. Cox stated that the use of pictures and drawings to convey some of the information has proven to be more effective.
The first case of Zika in Guyana was confirmed in January when a 27-year-old woman from Covent Garden on the East Bank of Demerara was diagnosed with the virus. More than a month since the first case was reported, the Minister of Public Health, Dr. George Norton last week announced that a 16-year-old Eccles, East Bank Demerara resident is Guyana’s second confirmed case of the Zika virus.
