Questions and Answers

Malaria is an infectious disease caused by the parasitic infection of red blood cells by a protozoan which is transmitted by the bite of an infected female malaria vector mosquito.

The name malaria is a Latin word meaning bad air; the early Romans associated the deadly fever with swamps and the bad smell that came from the swamps.

The epidemiological definition of a malaria vector is “An organism that does not cause disease itself but which spreads infection by conveying pathogens from one host to another”. In terms of malaria, it’s a female mosquito that has the ability to carry the malaria parasite and then spread the parasite to humans.

No, mosquitoes are not born with the malaria parasite; a malaria vector needs to bite a malaria infected person before they can transmit the disease to other humans. The percentage malaria infected people in a population and the density of malaria vectors determines your risk of contracting the disease.

There are over 3000 different mosquito species in the world and only 40 species are malaria vectors. Mosquito species have diverse behavioural characteristic and it is important to understand their feeding preference and resting patterns so that the most effective and appropriate malaria control intervention can be selected. Some mosquito species feed primarily on animals (zoophilic) and others seek out humans for their blood meal (anthropophilic). Some species live (exophilic) and bite outdoors (exophagic) while others fly into (endophilic) houses and feed indoors (endophagic).

Malaria control measures and methods vary a great deal and the epidemiological prototypes related to ecological and socio-economical factors and conditions determine to a large extent the malaria control method/s that are most appropriate. An integrated approach to malaria control focuses on vector control strategies based on the biology of the mosquito, the epidemiology of the disease, and human behavioural patterns. A typical integrated malaria vector control program will consists of the following malaria control intervention methods:

• Indoor Residual House Spraying (IRS).
• Larvaciding.
• Fogging (Space spraying).
• Environmental management.

Indoor residual house spraying (IRS) is a malaria control intervention whereby trained spray operators equipped with hand held pumps, spray the inside surface of the walls with a residual insecticide. The insecticide then dries and forms a crystalline deposit on the sprayed surface.

IRS is a tried and tested malaria control intervention method. The main aim of IRS is to kill and or repel the malaria mosquito from houses so that the mosquitoes cannot bite and transmit malaria to the inhabitants.

The insecticides used in IRS have the following ways of affecting the malaria vector mosquitoes.

• The deterrent effect or spatial repellency repels and deters the mosquitoes from entering sprayed houses.
• The excito-repelent effect causes discomfort to mosquitoes that do enter houses and that come into contact with the sprayed surface causing the mosquitoes to either die or to exit before biting.
• The toxicity of a residual insecticide kills mosquitoes on contact thus reducing the mosquito population and mosquito density in an area. By reducing the lifespan of the malaria vectors malaria transmission is interrupted by reducing human, vector contact.

The answer is in the name, indoor residual house spraying takes place indoors, residual insecticide is applied on the inside walls of houses. There are a number of reasons why insecticide is applied indoors only.

1. The application of residual insecticide indoors maximizes the protection to the inhabitants, preventing or repelling mosquitoes from entering houses and killing mosquitoes that do enter and come into contact with the sprayed surfaces.
2. Many malaria vectors bite and rest indoors, IRS targets these malaria vectors by applying insecticide against the walls.
3. The residual effect of the insecticide is prolonged when it is applied on the inside walls of houses because it is kept in a relatively cool and dry environment and out of direct sunlight that decreases the repellency and toxicity of insecticide.
4. By applying insecticide indoors it is kept out of the physical environment eliminating possible negative environmental contamination.

The timing of spraying operations varies according to your geographical location. Climatic factors such as rainfall and temperature dictate to a large degree when the malaria season starts and ends and thus when spraying commences and stops. In equatorial regions malaria transmission is year round and in other area malaria transmission is seasonal.

The frequency of spraying depends on the insecticide used in IRS due to varying degrees of efficacy and it depends on the surface the insecticide is sprayed on. Some insecticides remain effective for up to a year (DDT) and others can remain effective between 3 (Organophosphates) and 6 months (Pyrethroids). If an insecticide is effective for a year, IRS will take place once a year and if an insecticide is effective for 3 or 6 months then two to four spray rounds a year is required for effective malaria control. The frequency of spraying has a direct influence on the cost of the malaria control program.

All insecticide used in IRS malaria control should be World Health Organisation (WHO) approved insecticides for malaria vector control to ensure that the quality and efficacy of the products. The available IRS insecticides are divided into the following classes.

• Organophosphates.
• Carbamate.
• Pyrethroids.
• Organochlorine.

Several factors need to be considered before an insecticide is selected for IRS such as vector susceptibility, residual effect, excito-repellency, availability, cost and safety.

Spray coverage refers to the percentage houses sprayed in an area. The ideal situation would be to spray every single house; however spray coverage’s of 80% is seen as the gold standard for effective IRS malaria control.

Once a house is sprayed, a copy of a spray card is left in the sprayed house indicating when and by whom the house was sprayed. After each day, the field supervisor will collect these spray cards from the spray operators and the information will be captured into a database. A record is then kept of each sprayed house and the spray coverage can be calculated after each spray round. A field supervisor can monitor and evaluate the spray progress by looking at the spray cards left in houses to determine if, when and by whom the house was sprayed.

IRS is targeted at the malaria vector to break the human vector contact. The higher the spray coverage of an area the more people are protected from the malaria vector thus breaking the malaria transmission cycle. The combined repellency effect of sprayed houses in an area disrupts the collective resting and feeding patterns of the mosquito population in the sprayed areas.

Spray operators are equipped with a full overall, respiration mask, full facial visor, safety gloves and boots. Direct contact with the insecticide is minimized by the use of the above mentioned personal protection equipment and therefore it is safe for the spray operator. The insecticide used in IRS is World Health Organisation (WHO) approved insecticide and the risk of malaria infection far outweighs the risk that the insecticide can ever pose to people in malaria affective areas.

Larvaciding is a malaria vector control intervention method that targets the larval life stage of mosquitoes. Trained spray operators equipped with hand held pumps, spray larvacide on stagnant water to control the mosquito density.

Mosquitoes are prolific breeders and any stagnant water becomes potential mosquito breeding sites, larvacide on stagnant water kills mosquito larvae before they reach the adult stage.

The larvacide used in malaria vector control programs have different modes of action against mosquito larvae. Larvacide modes of action against the mosquito larvae vary between the following:

• Larval contact poison.
• Larval stomach poison.
• Larval growth regulators.
• Larval biological control agents.

Larvacide is applied to stagnant water that cannot be drained or filled with soil.

The frequency of larvaciding is determined by the efficacy of the selected product and by the rainfall patterns of the specific control area. Larvaciding frequency will increase in the wet season and decrease in the dry season.

Larvaciding will take place when mosquito larvae are identified during the surveillance of stagnant water bodies. Water bodies that lie stagnant for a period of 10 days and longer can become mosquito breeding sites.

There are several mosquito larvacides on the market with the following modes of action on the mosquito larvae.

• Larval contact poison.
• Larval stomach poison.
• Larval growth regulators.
• Larval biological control agents.

The various larvacides has been developed to kill mosquito larvae before they hatch and it poses no risk to human health, non target species and the environment if the products is used according to the label directions. Spray operators are equipped with a full overall, respiration mask, full facial visor, safety gloves and boots. Direct contact with the insecticide is minimized by the use of the above mentioned personal protection equipment and therefore it is safe for the spray operators.

Fogging (space spraying) is a malaria vector control intervention method that targets outdoor resting adult mosquitoes through the dispersion of liquid insecticide in the air.

Many of the mosquito species hide in vegetation during the day before the enter houses at night. Fogging just before dusk kills outdoor resting adult mosquitoes and reduces the mosquito density in the control area leading to less human vector contact.

Trained fogging operators would use either a thermal or ultra low volume fogger to disperse liquid insecticide into the air in the form of hundreds of millions of tiny droplets less than 50 μm in diameter to kill outdoor resting mosquitoes. The fogging operators rely on the wind speed and direction to drift the insecticide over the target area.

Fogging mainly takes place between and on the perimeter of a camp site or a group of houses and in areas with dense vegetation.

The timing and frequency of fogging is determined by the malaria vector species resting and biting habits. Most malaria vectors in Africa become active in the early evening and early morning and therefore fogging generally takes place during the above mentioned periods.

The timing and frequency of fogging is determined by the malaria vector species resting and biting habits and the rainfall of the specific control area.

• Natural pyrethrum.
• Pyrethroid.
• Organophosphate

Spray operators are equipped with a full overall, respiration mask, full facial visor, safety gloves and boots. Direct contact with the insecticide is minimized by the use of the above mentioned personal protection equipment and therefore it is safe for the fogging operator. The various fogging solutions have been developed to kill adult mosquito and it poses limited health risk to humans if the products is used according to the label directions.

Environmental management is a combination of different activities performed by trained environmental management operators to reduce the amount potential mosquito resting and breeding sites in a control area.

Environmental management reduces the potential mosquito breeding and resting places resulting in less human vector contact.

Trained environmental management operators routinely clean drainage ditches to encourage water flow, cut grass to encourage evaporation of stagnant water and fill or drain stagnant water to destroy mosquito breeding sites. All the above mentioned methods in combination reduce the malaria vector density in the control area leading to less human vector contact.

Environmental management is conducted in a control area wherever there are potecial mosquito resting and breeding sites.

Environmental management is a sustained process but the frequency is mainly determined by the rainfall pattern of the control area.

The frequency will increase in the wet season to at least twice per week and decrease in the dry season to once a week as less rainfall and standing water is prevalent in the control area.

IMCC’s main aim is to build the required malaria control capacity for the mine/company through training and skills transfer to local employees. The mine/company retains the skills and knowledge to continue with scientific, sustainable and effective malaria vector control.

Integrated malaria vector control training is a 2 week process where men and/or woman are recruited and thoroughly trained in the following malaria control aspects of IRS, larvcidning, fogging and environmental management.

• Safe use of personal protection equipment (PPE).
• Safe storage of insecticide.
• Insecticide storeroom inventory management systems and procedures.
• Safe mixing and handling of insecticides.
• Identification of mosquito breeding sites.
• Insecticide application technique.
• Malaria control equipment maintenance procedures and schedules.
• Documenting spray coverage.
• Safe disposal of insecticide refuse (empty sachets and insecticide waste water procedure).

Once the training is completed the IMCC trainer stays on site and completes the first integrated malaria vector control round with the newly established malaria control team to ensure that all aspects of the training is adhered to and to ensure that all international best practice and standards are followed.