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Zika Virus

Zika virus disease is a viral disease transmitted primarily by Aedes mosquitoes; the same vector carrying dengue, yellow fever, chikungunya, and Rift Valley viruses. The virus, first identified in the late 1940’s in Eastern Africa, caused small outbreaks in Western Africa, and Asia (1960s, 1970s), and an epidemic in Polynesia (2007). The current strain of Zika virus, first affecting Chile (Easter Islands in 2014) then Brazil (2015) and now numerous additional countries of the Americas, is more closely related to that of Polynesia than the African strains.

For updates on Zika virus and details on human health, please refer to WHO. 

Prevention and protection

The best form of prevention is protection against mosquito bites, and the elimination of mosquito breeding sites.  This applies to both urban and rural areas.  As the mosquitos need water for their larvae stage, stagnant waters should be removed or drained to disrupt breeding possibilities.
WHO recommendations on this can be found at:

Livestock, water and mosquitoes

Livestock are not known to be susceptible to Zika virus, but livestock are kept in peri-urban and rural areas, where their need for water also increases opportunities for mosquitoes to breed and thrive.

A specific challenge is posed by watering facilities for livestock, such as drinking water containers and watering holes.  For keeping mosquito breeding low in such facilities, FAO recommends that animal drinking water troughs, or other containers, are emptied, cleaned, and scrubbed twice weekly. 


Widespread alarm over the current outbreak of Zika will, at least in the short term, likely see a dramatic increase in the use of pesticides to control mosquito populations or their larvae in water. WHO recommends fogging with pesticides for emergency situations only, and stresses that the elimination of mosquito breeding sites is the most effective intervention for protecting human populations.  If pesticides are used, then it is important that the right types of pesticides are used in the right manner

Which pesticides to use

Information on selection of pesticides is available on the website of the WHO Pesticide Evaluation Scheme (WHOPES). It provides detailed guidance on chemical vector control.  The types of recommended pesticides vary depending on their  specific purpose:

Agricultural pesticides that are not on the WHOPES list should not be used!

Certain pesticides can be highly toxic to fish. When selecting a product to treat borders of open water for adult mosquitos, one should chose a product from the WHO list that is not toxic to fish. Information about fish toxicity can be found on the label or on the internet.   

How to use these pesticides

Pesticides should be mixed and applied according to instructions by WHO and the manufacturer, in order to maximize efficacy and minimize risks.  The recommend dosage is provided in the above WHO links on recommended pesticides.

Persons handling and applying pesticides should be aware of the hazards and potential risks. They should have the appropriate application equipment and personal protection equipment (PPE), and be trained in the proper handling, application and storage of the chemicals they are exposed to. This should include training in the proper use of PPE and the use and maintenance of application equipment.  All operators of equipment (sprayers, foggers, etc.) should wear personal protective equipment appropriate for the application of their duties.

Specific guidance is available on:

Longer term general considerations related to pesticide use

In general, FAO and WHO recommend member countries to handle and use pesticides in compliance with the International Code of Conduct on Pesticide Management [2014], which covers pesticide life-cycle management including registration, importation, transportation, application and disposal of pesticide wastes. FAO/WHO technical guidelines on implementation of the Code of Conduct are available on the FAO and WHO websites.

New techniques – Sterile insect technique

An area for further refinement and validation is the Sterile Insect Technique (SIT) that has been developed during the last ten years at the FAO-IAEA Joint Programme on Nuclear Techniques in Food and Agriculture. This is a form of pest control that uses ionizing radiation to sterilize male insect pests that are mass-produced in special rearing facilities. It has been successfully used worldwide for over 50 years for various agricultural insect pests, such as fruit flies, tsetse flies, screw worms and moths. Its deployment against Aedes disease-transmitting mosquitoes, such as the carrier of the Zika, chikungunya and dengue viruses, is ongoing with some pilot projects already successfully completed and others showing promising results. The SIT offers the most responsible biologically-based approach in terms of eco-friendliness and biosecurity because the irradiated and released insects are sterile and cannot become established in nature. The transgenic approaches instead can have potentially unforeseen consequences because the released insects are not sterile and therefore will reproduce and become established. See here for more information.

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