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    The Cayman Islands Mosquito Research & Control Unit

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    About Us

    The Mosquito Research & Control Unit (MRCU) was established in 1965 when Marco Giglioli arrived from London with instructions ‘to establish a laboratory and conduct research with a view to advising the Cayman Government on suitable methods of control.’

    The Mosquito Research and Control Unit aims to help Cayman Islands residents by reducing mosquito nuisance and protecting against mosquito-borne diseases such as malaria and dengue which are common in the region.

    To do this, we employ an Integrated Pest Management approach, using a range of physical, biological and chemical control techniques to minimize nuisance levels of mosquitoes and prevent disease transmission.

    Dr Marco Giglioli



    • 1834 – The first record of a mosquito problem on Grand Cayman by the Governor of Jamaica who when visiting noted ‘The mosquitoes there amount to quite a national misfortune.’
    • 1938 – The first known survey of species was carried out by a visiting sanitary inspector followed the same year by a team from Oxford University
      • 1948 – Further surveys carried out by a visiting malariologist (Dr G Giglioli)


      • 1965 – The Mosquito Research & Control Unit was established under the control of Dr Marco Giglioli to prevent vector borne disease and to reduce nuisance biting. A laboratory was set up on the current site of George Town hospital A&E.


      • 1966 – The Mosquito (Research &) Control Law was first passed.


    • 1966 – The first vehicle mounted fogging unit (a Tifa Todd machine) hit the streets of George Town by 1969 there were 9 fogging units mostly mounted on Mini Mokes, staffed largely by volunteers.

      • 1967 – Dyke building began in the swamps of Grand Cayman and the network of dykes and canals grew until 1983. This allowed for the swamp levels to be manipulated to interrupt the breeding cycles of the swamp mosquito.


      • 1968 – Port disinsection began; arrangements were made for the spraying of any ship or aircraft arriving in Grand Cayman.


      • 1970 – Operations began in the Sister Islands.


      • 1971 – The first aerial insecticide campaign took place using malathion from a Cessna Ag-Wagon aircraft.


      • 1971 – Dr Giglioli the Director of MRCU was awarded the Order of the British Empire (O.B.E) medal for his work in mosquito control.


      • 1972 – Aerial applications began on a large scale.


      • 1974 – Records were broken when 793,103 mosquitoes were caught in a trap in Bodden Town in a single night.


      • 1987 – Due to the appearance of insecticide resistance to conventional insecticides, hormonal and bacterial insecticides are introduced.


      • 1996 – Moved to the Giglioli Building on North Sound Road.


      • 1996 – Further excavation of the swamps (the creation of ‘canalitos’) increasing the flow of water in and out of the swamp with tide and rainfall.


      • 2003 – Large scale larviciding operations (using temephos) were first carried out and larvicing remains the mainstay for control of the swamp mosquitoes.


    • 2006 – the MRCU moves to it’s current custom built building on Red Gate Road.
    Biorational Mosquito Control products

    Pesticides vary in their toxicity and in their potential ecological impact. Pest control materials that are relatively non-toxic to people with few environmental side effects are sometimes called “biorational” pesticides. These fit well into an integrated pest management strategy, which relies on monitoring for early detection of pests and emphasizes the use of selective products that provide control while preserving the ecological health of the farm and minimizing negative effects on beneficial insects that suppress pests. MRCU incorporates a number of these biorational products in their integrated mosquito control programme.


    Bacillus thuringiensis subsp. israelensis (Bti) is a naturally occurring soil bacteria used as a microbial insecticide tocontrol the spread of vector-borne diseases, protect public health, and manage insect pest species. Bti was firstdiscovered in a stagnant pond in Israel in 1976 (Margalit and Dean 1985). Initial testing of Bti revealed acutetoxicity to mosquitoes (Goldberg and Margalit 1977) and black flies (Undeen and Nagel 1978). Further researchdemonstrated that Bti is nontoxic to humans, mammals, birds, beneficial insects, fish, plants, and most aquaticorganisms (EPA 1998 Bti EG2215 Factsheet). Bti an ideal pesticide with greatly reduced environmental impacts incomparison to man-made chemical insecticides. In addition, Bti is species specific, breaks down rapidly, limitednon-target impacts (de Barjac and Sutherland 1990), There are 26 Bti products in the United States with some ofthe following trade Names: Vectobac, Teknar, Aquabac, Bactimos, LarvX, etc.


    Spinosad is natural product approved for use in organic agriculture by numerous national and international regulators including the US EPA. Spinosad has ?a good environmental profile and is an effective natural product for the integrated management of larval mosquitoes. It possesses a unique mode of action not shared by any other insecticide and is shown to be minimally disruptive to most non-target species tested. It is made by a soil bacterium named Saccharopolyspora spinosa and is a mixture of two chemicals called spinosyn A and spinosyn D.The genus?Saccharopolyspora?was discovered in 1985 in isolates from crushed?sugar cane collected at an abandoned rum factory in the Caribbean Virgin islands. Evaluation of the bacterial actinomycete showed it to have powerful insecticidal properties.?Spinosad has been registered for use in pesticides by the US Environmental Protection Agency (EPA) since 1997. MRCU has been using EPA approved spinosad based products since 2012. Spinosad is highly active against larvae of all mosquito species tested. The only spinosad based products currently available for mosquito control in the Caribbean region are sold under the trade name Natular. Natular products are the first larvicides evaluated as a Reduced Risk product by the EPA.Spinosad is highly active to mosquito larave, by both contact and ingestion.?Spinosad affects the nervous system of insects that eat or come in contact with it, primarily targeting binding sites on nicotinic acetylcholine receptors of the insect nervous system and causing their muscles to flex uncontrollably. This ultimately leads to paralysis and death in 24-48 hours.

    MRCU’s mosquito control program employs IPM principles by first determining the species and abundance of mosquitoes through larval and adult surveillance and then using the most efficient, effective and environmentally sensitive means of control.

    Methoprene is a growth regulator which prevents larvae by imitating the mosquitoes natural juvenile hormone. Because methoprene affects other insects but is safe for humans and mammals, it’s also formulated and sold for controlling a variety of other pests, from flies on cattle farms to fleas on dogs. Methoprene does not work by killing mosquito larvae directly; they will continue to live as larvae until they’re eaten by predators or die naturally but they will never turn into adult mosquitoes.


    Aquatain AMF is a unique silicone-based liquid for mosquito control. The product has a purely physical action and does not contain any toxic chemicals. It spreads across the surface of standing water – even large water bodies – and forms a very thin film. As silicones have a very low surface tension, the film prevents pupae and larvae from attaching themselves at the surface while attempting to breathe, thereby causing them to drown.Aquatain AMF is approved for sale in 60 countries including Australia. In April 2015, the European Commission formally exempted the product from registration in the European Union due to its physical action.?Aquatain AMF has been prequalified by the World Health Organization (WHO) for procurement by the UN and other international agencies and countries in tackling mosquito-borne diseases.?

    Synthetic Pyrethroids

    Pyrethroids are synthetic chemical insecticides widely used for controlling a variety of insects. Permethrin and Deltamethrin? are the two synthetic pyrethroids commonly used by MRCU to kill adult mosquitoes.

    Permethrin has been registered by the EPA since 1979. It is currently registered and sold in a number of products such as residential indoor and outdoor insect foggers and sprays, treated clothing, flea products for dogs, termite treatments, agricultural and livestock products, and mosquito abatement products. It is also regulated by the Food and Drug Administration as a treatment of head lice and scabies. Permethrin is the most widely used mosquito adulticide in the U.S. and is used to treat 9 to 10 million acres annually (out of 32-39 million acres treated with a mosquito adulticide). Permethrin’s widespread use can be attributed to its low cost, high effectiveness, low incidence of pest resistance, and broad labeling.

    Most pyrethroid mosquito control products can be applied only by public health officials and trained personnel of mosquito control districts. MRCU ?applies pyrethroids as an ultra-low volume (ULV) spray from both trucks and aircraft. ULV sprayers dispense very fine aerosol droplets that stay aloft and kill adult mosquitoes on contact. Pyrethroids used in mosquito control are typically mixed with a synergist compound, such as piperonyl butoxide, which enhances the effectiveness of the active ingredient. The product is often diluted in water or oil and applied at rates less than 1/100th of a pound of active ingredient or less than 4 fluid ounces of mixed formulation per acre.

    The United States Environmental Protection Agency (EPA) has conducted human health risk assessments for all labeled uses of pyrethroids. Based on the results of these assessments and any required label changes, pyrethroids can be used for public health mosquito control programs without posing unreasonable risks to human health when applied according to the label. At high exposure levels, such as those resulting from accidents or spills, pyrethroids can affect the nervous system.

    When applied according to label directions, pyrethroids used in mosquito control programs do not pose unreasonable risks to wildlife or the environment. Pyrethroids are low in toxicity to mammals and are practically nontoxic to birds. However, pyrethroids are toxic to fish and to bees.?

    The EPA reevaluates all pyrethrins, pyrethroids and synergists through registration review. Registration review is our program for systematically reviewing all registered pesticides every 15 years to make sure that every pesticide can still perform its intended function without unreasonable adverse effects on human health or the environment.

    As a result of the Food Quality Protection Act, EPA must consider the cumulative risks of pesticides that, like the pyrethroids and pyrethrins, share a common mechanism of toxicity. In November 2011, the EPA completed a cumulative risk assessment for the pyrethroids/pyrethrins and identified no cumulative risks of concern. This assessment is available from Regulations.gov, docket EPA-HQ-OPP-2011-0746.


    The Environmental Protection Agency (EPA) evaluates and registers (licenses) pesticides to ensure they can be used safely. These pesticides include products used in the mosquito control programs which states and communities have established. To evaluate any pesticide, EPA assesses a wide variety of tests to determine whether a pesticide has the potential to cause adverse effects on humans, wildlife, fish and plants, including endangered species and non-target organisms.

    mosquito officials select control measures that best suit local conditions Officials responsible for mosquito control programs make decisions to use pesticides based on an evaluation of the risks to the general public from diseases transmitted by mosquitoes or on an evaluation of the nuisance level that communities can tolerate from a mosquito infestation. Based on surveillance and monitoring, mosquito control officials select specific pesticides and other control measures that best suit local conditions in order to achieve effective control of mosquitoes with the least impact on human health and the environment. It is especially important to conduct effective mosquito prevention programs by eliminating breeding habitats or applying pesticides to control the early life stages of the mosquito. Prevention programs, such as elimination of any standing water that could serve as a breeding site, help reduce the adult mosquito population and the need to apply other pesticides for adult mosquito control. Since no pesticide can be considered 100% safe, pesticide applicators and the general public should always exercise care and follow specified safety precautions during use to reduce risks.?


    Malathion is an insecticide commonly used in mosquito control programs.Malathion is an organophosphate (OP) insecticide that has been registered for use in the United States since 1956. It is used in agriculture, residential gardens, public recreation areas, and in public health pest control programs. When applied in accordance with the rate of application and safety precautions specified on the label, malathion can be used to kill mosquitoes without posing unreasonable risks to human health or the environment.

    ?Malathion is an adulticide, used to kill adult mosquitoes. MRCU applies malathion by truck-mounted and aircraft-mounted sprayers.Malathion is applied as an ultra-low volume (ULV) spray. ULV sprayers dispense very fine aerosol droplets that stay aloft and kill mosquitoes on contact. ULV applications involve small quantities of pesticide active ingredient in relation to the size of the area treated. For mosquito control, malathion is applied at a maximum rate of 0.23 pounds (or about two and one-half fluid ounces) of active ingredient per acre, which minimizes exposure and risks to people and the environment.

    Malathion can be used for public health mosquito control programs without posing unreasonable risks to the general population when applied according to the label. The EPA has estimated the exposure and risks to both adults and children posed by ULV aerial and ground applications of malathion. Because of the very small amount of active ingredient released per acre of ground, the estimates found that for all scenarios considered, exposures were hundreds or even thousands of times below an amount that might pose a health concern. These estimates assumed several spraying events over a period of weeks, and also assumed that a toddler would ingest some soil and grass in addition to skin and inhalation exposure.

    However, at high doses, malathion like other organophosphates, can overstimulate?the nervous system causing nausea, dizziness, or confusion. Severe high-dose poisoning with any organophosphate can cause convulsions, respiratory paralysis and death.


    Integrated Pest Management
    ipm overview

    In order to accomplish long-range, intelligent, and environmentally sound mosquito control, the management of mosquitoes must use not just one but all available pest control methods. This dynamic combination of methods into one thoughtful, ecologically-sensitive program is referred to as Integrated Pest Management (IPM). Sometimes when referring to vector mosquitoes, this program is referred to as Integrated Vector Management (IVM). MRCu’s mosquito control program employs IPM principles by first determining the species and abundance of mosquitoes through larval and adult surveillance and then using the most efficient, effective and environmentally sensitive means of control. In some situations, water management or source reduction programs can be instituted to reduce breeding areas. MRCU also considers biological control such as the planting of mosquitofish (Gambusia affinis). When these approaches are not practical or otherwise appropriate, then a pesticide program is used so that specific breeding areas and/or adult mosquitoes can be treated.

    The Cayman Islands has many water sources that act as mosquito/vector breeding areas near populated areas. Without ongoing and effective mosquito control, the human environment would be significantly and adversely affected by substantial mosquito activity. MRCU’s mosquito control program, including biological and chemical control, is essential to abate the vectors in the environment to a tolerable level. MRCU’s program will never alleviate all mosquito vectors. Rather, it is a maintenance program aimed at striking a balance to allow comfortable and healthful human existence, while protecting and maintaining the environment. History has shown us that the control and abatement of vectors are necessary for our human environment to continue to be habitable.

    MRCU’s mosquito control program is directed primarily at the larval stages of mosquitoes. Control activities are contained to a localized area and have a lower impact utilizing this approach because the larvicides used by MRCU specifically target the mosquito’s biological systems. Although adult mosquitoes may be targeted for control, it is not the emphasis of MRCU’s program. Focusing on mosquito larvae requires that control be achieved in a number of different types of breeding sources.



    Chemical Control

    Chemical Control

    Public Education

    Public education is a key component that is used to encourage the reduction and prevention of mosquito habitats on private and public property. MRCU’s education program teaches the public how to recognize, prevent, and suppress mosquito breeding on their property. This is accomplished through the distribution of brochures, fact sheets, newsletters, participation in local events and fairs, presentations to community organizations, newspaper and radio advertising, public service announcements, social media, and contact with MRCU staff in response to service requests. Public education also includes school presentations that teach future adults to be responsible by preventing and/or eliminating mosquito breeding sources.

    Hatch and Strand (and the Canals)

    Hatch and Strand is a program set up by MRCU whereby we can manipulate the water levels that allow the swamp to reduce the numbers hatching at the start of the season. During the dry season the swamp mosquitoes lay their eggs just above the water line meaning when the tide significantly increases or rain begins to fall they will flood and hatch in large numbers.

    During the spring time low tides we are able to block off large sections of the swamp using a system of sluice gates and water is pumped into these areas in order to flood them. This is maintained for several days to allow the larvae to hatch. Following this the sluice gates are opened and the water drains out to sea taking large numbers of mosquito larvae with it and stranding the rest in the mud to die.

    The canals also act as a passive means of control allowing tidal variations into and out of the swamp. They also aid drainage after heavy rainfall.

    Biological Control

    There are a number of natural predators that feed on adult mosquitoes and larvae. Some of the more common predators are detailed below. MRCU has utilized mosquito fish (Gambusia sp) in its control operations. In the mid-1970’s these fish were seeded across all mangrove areas of the island by dropping them from helicopters. They are now established and play an important role in reducing mosquito numbers.


    Goldfish, guppies, bass, bluegill and catfish prey on mosquito-larvae. But the most important fish predator, by far, are the Gambusia species, commonly known as the mosquito fish. This is probably the most effective predator of mosquito larvae and is used by many mosquito control agencies to augment their control efforts.


    Many birds will eat mosquitoes. The more important among these are purple martins, swallows, waterfowl (geese, terns, ducks) and migratory songbirds. Bird predators usually eat both the adult and aquatic stages of mosquitoes.


    Most adult frogs and tadpoles do not include mosquitoes as a large part of their diet. Tadpoles infrequently feed on mosquito larvae and instead generally feed on small, suspended particles of plant-related materials. However, mosquito larvae predation is known for three species of North American tadpoles – the spade foot toad, green tree frog and giant tree frog. While not a direct act of predation, tadpoles may compete with mosquito larvae for food.


    Dragonflies are often referred to as “mosquito hawks.” Though they do eat mosquitoes, they do not eat enough mosquitoes to do much harm to wild populations. One feature that favors dragonflies as mosquito predators is that in the dragonflies’ aquatic stage, most of its food consists of mosquito larvae.


    While damselflies are not as effective in controlling mosquitoes as dragonflies, their aquatic stage also consumes many mosquito larvae.



    While bats eat mosquitoes, they are far more effective at locating, catching and eating insects other than mosquitoes.


    Spiders become mosquito predators when a mosquito inadvertently flies into a spider’s web where it is encased and eaten.


    The red-eared slider turtle is generally thought to be the most voracious turtle that feeds on mosquito larvae.


    Some mosquitoes prey on other mosquitoes. The most notable being the predatory mosquitoes in the genus Toxorhynchites. These mosquitoes provide a double benefit since the larvae are predacious on other mosquito larvae and the adults are not known to transmit disease.

    Both adult and larval species of aquatic beetles will consume mosquito larvae and pupae. Two beetles that readily eat the aquatic stages of mosquitoes are the predaceous diving beetle and the water scavenger beetles. However, they will consume many types of aquatic insects other than mosquitoes.

    Freedom of Information

    For more information on Freedom of Information please see: www.foi.gov.ky/

    As a public authority, the Portfolio of the Civil Service is committed to openness, transparency and serving the public interest in compliance with the Freedom of Information Law, 2007.

    The Freedom of Information (FOI) Law was passed on 19th October 2007 and came into effect in January 2009. It gives the public a right of access to all types of records held by public authorities, but also sets out some exemptions from that right.

    Publication Schemes

    Each public authority covered by the Freedom of Information Law has a legal duty to adopt and maintain a publication scheme in accordance with s. 5 of the FOI Law. The main purpose of a publication scheme is to make information readily available without the need for specific written requests. Schemes are intended to encourage organisations to publish proactively, and develop a greater culture of openness.

    The Law states that Information to be published by public authorities includes:-

      • The functions of the authority, what work it does and how it sets about its tasks.


      • The departments and agencies of the authority.


      • The subjects handled by each department or authority, with the locations of the departments and agencies and the opening hours of all offices.


      • The title and business address of the Principal Officer and other key officers within the authority.


      • Classes of records held.


    • Manuals, interpretations, rules, guidelines, practices or precedents.

    Classes of Information

    A Class of Information is a way of collecting together similar types of information. The Mosquito Research & Control Unit has grouped its Classes of Information into?broad categories (or functions)?which

    reflect?the Portfolio’s outputs. If you are intending to make a request, the following grouping of information should give you an indication of where the information may be found.

    • Administration
    • Policy development and advice
    • Operational support and advice

    Making a Request

    We want to help you find the information you are interested in.

    If you want to request information from the Mosquito Research & Control Unit, contact the Information Manager or the FOI Unit.

    Requests must be in writing (letter, email or facsimile) and must include your name and an address (either postal or e-mail). Please be as specific as possible about the information you would like, as this will help us to respond promptly. Where possible, please include a contact telephone number so we can call to discuss your request if necessary.

    We will respond to your request promptly. The Law requires public authorities to respond within 30 calendar days, allowing an extension of an additional 30 calendar days if needed. We will always acknowledge receipt of FOI requests made to the Information Manager and we will let you know if we need to extend the deadline. For detailed advice on what sorts of information is exempt please see the FOI Unit website.

    Information Manager Contact Details

    Ms. Ligia Whittaker
    The Mosquito Research and Control Unit
    The Marco Giglioli Building
    99 Red Gate Road
    PO Box 486
    Grand Cayman KY1-1106
    Telephone: – +1 345 949 2557
    Fax: – + 1 345 949 8912
    E-mail: – foi.mrcu@gov.ky


    Fees associated with a Request for Information

    There is no application fee and no fee for going to a public authority and looking at a record requested by FOI. However, a requester may be required to pay copying or change of format fees. Details concerning costs and payment are contained in the FOI Regulations which are available on the FOI Unit website.

    Right of Appeal

    If you are not satisfied with the help offered to access information from the Mosquito Research & Control Unit, you should contact the Information Manager.

    If you have a complaint not relating to Freedom of Information please visit our contact us section.

    Internal Review

    If you make a request under the Freedom of Information Law and are not satisfied with our response, you are entitled to an internal review. If you believe you are entitled to an internal review, please put your complaint in writing and either e-mail or post it to the Information Manager. Include your name, address, telephone number and the reference number at the top of our letter or e-mail to you. You have 30 calendar days from the date of receipt of a refusal to request an internal review. Please explain why you would like us to review our original response.

    Under section 33 of the FOI Law, you may ask for an Internal Review of a response to your request:

    • If you were refused access.
    • If you were granted partial access to the record(s) specified in your application.
    • If your request was deferred.
    • If there was a refusal to amend or annotate an official document containing personal information.
    • If a fee was charged for action taken* or if you disagree with the amount of the fee charged.

    *Where the decision was taken by a person other than the responsible Minister, Chief Officer or Principal Officer of the public authority.

    Appeal to the Information Commissioner

    If you are dissatisfied with the internal review of our decision, or an internal review was not available, you can seek an appeal from the Information Commissioner.

    Dislosure Log

    This website forms the Mosquito Research & Control Unit e-publication scheme, developed in compliance with Section 5 of the FOI Law.

    The disclosure log provides details of FOI requests that we feel may have a wider public interest.

    Please note that the disclosure log does not list everything that has been released under FOI. Some responses consist of large numbers of documents that are not held in electronic format. Where practical, the documents concerned have been scanned and made available online via our website. Requests sent to multiple departments and not specific to MRCU have been omitted.

    In addition to a summary of the original request, the log indicates whether or not the information was released and what exemptions, if any, were applied.

    Where the actual reply has been reproduced, the applicant’s name and other personal details have been deleted.

    Mosquito Lifecycle

    Mosquitoes (Order Diptera, Family Culicidae) are some of the most adaptable and successful insects on Earth and are found in some extraordinary places. Virtually any natural or man-made collection of water can support mosquito production. They’ve been discovered in mines nearly a mile below the surface, and on mountain peaks at 14,000 feet, and if you know where to look, there is a good possibility that there are mosquitoes breeding in your own backyard. Not every species of mosquito causes problems for people, but many have profoundly negative effects. Mosquitoes can be distinguished easily from other flies by the fact that they have both a long, piercing proboscis and scales on the veins of their wings. Approximately 35 species of mosquitoes are found in the Cayman Islands, with more than 3,000 species known throughout the world. In the Cayman Islands, only a few of these species are important as carriers of disease, but many more are important nuisance species that dramatically affect peoples’ quality of life.


    While all mosquitoes need standing water to reproduce, different mosquito species are found in different habitats. Some mosquitoes are considered “floodwater” species that breed in temporary water habitats, while others are considered “permanent water” mosquitoes and breed in water sources that remain for long periods of time. Other species have evolved so specifically that they will only lay their eggs in natural or artificial containers.?No matter what their preferred breeding habitat, all mosquitoes undergo the same four-stage life cycle: egg, larva, pupa, and adult, with the larval and pupal stages always being aquatic.


    Once the egg hatches, the larval stage begins. The larvae of most mosquito species hang suspended from the water surface because they need air to breath. An air tube, called a siphon, extends from the larva’s posterior to the water surface and acts as a snorkel. Larvae filter feed on aquatic microorganisms near the water’s surface. As a defense mechanism, when alarmed, the larvae can dive deeper into the water by swimming in a characteristic “S” motion, which has earned them the nickname “wigglers” or “wrigglers”. As they feed, larvae outgrow their exterior covering and form a new exoskeleton, casting off the old ones. The stages between these molts are called instars. The larval stage has four instars. The length of the larval stage ranges from 4 to 14 days, varying with species, water temperature, and food availability.


    In the pupal stage, no feeding occurs, however the pupa must still breathe air at the water’s surface and is sensitive to light, shadows, and other disturbances. Pupae are also physically active and employ a rolling or tumbling action to escape to deeper water, which is why they are commonly referred to as “tumblers”. The pupal stage lasts from 1 1/2 to 4 days, after which the pupa’s skin splits along the back allowing the newly formed adult to slowly emerge and rest on the surface of the water.



    The male adult mosquito will usually emerge first and will linger near the breeding site, waiting for the females. Mating occurs quickly after emergence due to high adult mortality rates. As much as 30% of the adult population can die per day. The females compensate for this high rate by laying large numbers of eggs to assure the continuation of the species. Male mosquitoes will live only 6 or 7 days on average, feeding primarily on plant nectars, and do not take blood meals. Females with an adequate food supply can live up to 5 months or longer, with the average female life span being about 6 weeks. To nourish and develop her eggs, the female usually must take a blood meal in addition to plant nectars. She locates her victims by the carbon dioxide and other trace chemicals exhaled, and the temperature patterns they produce. Mosquitoes are highly sensitive to several chemicals including carbon dioxide, amino acids, and octenol. The average female mosquito’s flight range is between 1 and 10 miles, but some species can travel up to 40 miles before taking a blood meal. After each blood meal, the female will oviposit (lay) her eggs, completing the life cycle. While some species oviposit only once, others may lay eggs several times over the course of their lives.

    A Brief Guide to Common Mosquitoes of the Cayman Islands.

    Although there are in the region of 36 reported species of mosquitoes found in the Cayman Islands some we see more regularly than others. If you have a mosquito problem and want to report it to the department you may be able to help our investigations by taking a short look at this guide.

    Aedes? taeniorhynchus

    The ‘Black Salt-Marsh mosquito.’ This small black mosquito is by far the most abundant pest mosquito in the Cayman Islands. Most of our operational efforts go into the control of this species. This mosquito breeds mainly in the swamps, the female lays her eggs in the mud and when water levels rise they hatch in large numbers. It is a strong flier and can travel long distances, so large numbers emerging on one part of the island can quickly spread. These mosquitoes can be found year round, but numbers peak in the rainy season. They are active around sunrise and sunset.



    Psorphora ciliata and Psorophora columbiae

    These are the two largest species of mosquito found in the Cayman Islands. They breed mainly in standing water on pasture land. They hatch off in large numbers after the first rains and can be a serious biting nuisance to people and livestock. They are black mosquitoes easily identified by their size.







    Culex nigripalpus

    This small brown mosquito will breed almost anywhere, but the most saline parts of the swamp, it can be found in natural pools and ponds as well as crab holes and artificial breeding sites like buckets.



    Culex quinquefasciatus

    Another small brown mosquito, however Culex quinquefasciatus or the Southern House Mosquito is more likely to be found in the domestic setting, it favours nutrient rich breeding sites such as compromised septic tanks or sites containing plant material.





    Aedes aegypti

    Aedes aegypti

    Aedes aegypti or the ‘Yellow Fever Mosquito’ is a very domesticated mosquito. It is found associated with human habitation breeding in water drums, guttering, buckets and discarded trash. It can be controlled by house and business owners by simply clearing up any water holding containers or making sure that water is not allowed to stand for more than a couple of days in e.g. bird baths, pet water bowls, plant pots, etc. it is a distinctive black and white mosquito that bites mostly in the daytime/late afternoon. This mosquito can carry yellow fever, dengue and chikungunya viruses. It is found widespread across Grand Cayman, but help from the public can help to seriously reduce numbers. Clear up trash and other sources of standing water, including buckets, dog bowls, ornamentals, plant pots and tires. Anything that will hold water when it rains will provide the perfect breeding site for this mosquito

    Aedes albopictus

    Is widely known as the ‘Asian Tiger Mosquito.’ This small black and white mosquito with its distinctive stripe across the thorax is often associated with the domestic setting. It breeds in containers around the house as well as tree holes and natural water containers nearby. Aedes albopictus is a carrier of the deadly dengue and chikungunya viruses. Currently it is found in relatively small numbers in Grand Cayman where it first arrived in 1997.





    There are a number of Anopheles species to be found in the Cayman Islands. They breed mostly in fresh water and are easily identified when biting as they stand ‘end-up’ unlike other mosquitoes that keep their bodies flat. Anopheles stand with their heads down and are often described as needle like in appearance. Of the Anopheles found in the Cayman Islands one species; Anopheles albimanus can carry the malaria parasite. This mosquito can be identified by the ways it stands as well as its distinctive rear white feet. Anopheles like to bite late into the evening.

    *Photo credit for Anopheles albimanus by Audio Visual, LSHTM. Wellcome Images. images@wellcome.ac.uk.

    *For other photo credits see images.

    Mosquito-Borne Diseases

    Mosquitoes cause more human suffering than any other organism — over one million people worldwide die from mosquito-borne diseases every year. Not only can mosquitoes carry diseases that afflict humans, they also transmit several diseases and parasites that dogs and horses are very susceptible to. These include dog heartworm, West Nile virus (WNV) and Eastern equine encephalitis (EEE). In addition, mosquito bites can cause severe skin irritation through an allergic reaction to the mosquito’s saliva – this is what causes the red bump and itching. Mosquito vectored diseases include protozoan diseases, i.e., malaria, filarial diseases such as dog heartworm, and viruses such as dengue, encephalitis and yellow fever. CDC Travelers’ Health provides information on travel to destinations where human-borne diseases might be a problem.

    Dog Heartworm
    Yellow Fever
    Eastern Equine Encephalitis
    St. Louis Encephalitis
    LaCrosse Encephalitis
    Western Equine Encephalitis
    West Nile Virus
    Zika Virus

    Malaria is an ancient disease. In all likelihood originating in Africa, it has been described by the Chinese as far back as 2700BC and the Sumerians from 1700 BC. The malaria parasite (plasmodium) is transmitted by female Anopheles mosquitoes. The term malaria is attributed to Horace Walpole in a letter from Italy in 1740 and is derived from the Italian ‘mal-aria” or “bad air” because it was thought to come on the wind from swamps and rivers. Scientists conducted much research on the disease during the 1880s and early 1900s. Approximately 40% of the world’s population is susceptible to malaria, mostly in the tropical and sub-tropical areas of the world. It was by and large eradicated in the temperate area of the world during the 20th century with the advent of DDT and other organochlorine and organophosphate mosquito control insecticides. An elevated standard of living, including the use of air conditioners and window screens, along with public health interventions have largely remanded malaria transmission to tropical areas. Nonetheless, it can still be found in northern Europe.

    More than one million deaths and 300 – 500 million cases are still reported annually in the world. It is reported that malaria kills one child every 40 seconds. In the United States malaria affected colonization along the eastern shore and wasn’t effectively controlled until the 1940s when mosquito control organization instituted Anopheles control programs. A resurgence occurred during the 1960s and early 70s in the United States due to returning military personnel from Vietnam. Minor outbreaks of locally-acquired malaria occur sporadically in the United States, but have been quickly controlled by aggressive mosquito control measures. The influx of illegal immigrants in addition to returning tourists may provide for infrequent outbreaks in the future.

    Anopheles quadrimaculatus and Anopheles freeborni have been the primary vector of the Plasmodium vivax (protozoa) in the United States (Foote and Cook 1959).

    Antimalarial drugs have been available for more than 50 years and recently scientists in Britain and the United States have cracked the code of the malaria parasite genome, a step that may help boost the campaign against the disease. In the meantime, active case detection

    Chikungunya virus is a pathogen transmitted by mosquitoes, and has established itself in the Caribbean (approximately 350,000 suspected cases in the Western Hemisphere since December 2013). It has now resulted in 2 cases of locally-transmitted Chikungunya virus in Florida in July of 2014. As of July 22, 2014, 497 travel-related cases have been found in 35 states, Puerto Rico and the U.S. Virgin Islands. The occurrence of locally-transmitted cases causes public health officials fear to its spread and establishment in states bordering the Caribbean. The name “Chikungunya” is attributed to the Kimakonde (a Mozambique dialect) word meaning “that which bends up”, which describes the primary symptom – excruciating joint pain. Although rarely fatal, the symptoms are debilitating and may persist for several weeks. There is no vaccine and primary treatment is limited to pain medication.

    The mosquito species that transmit this disease are the Asian Tiger Mosquito (Aedes albopictus) and the Yellow Fever Mosquito (Aedes aegypti). Genetically, it appears that viral strain currently spreading throughout the Americas is more easily transmitted by Ae. aegypti. Both species lay their eggs in containers such as cans, discarded tires and other items that hold water close to human habitation, but Ae. aegypti is more geographically confined to the southeastern United States. Traditional mosquito methods of truck-mounted and aerial sprays are ineffective in controlling these mosquitoes. Removal of water-bearing containers and sanitation are key preventive strategies.

    Dog HeartwormDog heartworm (Dirofilaria immitis) can be a life-threatening disease for canines. The disease is caused by a roundworm. Dogs and sometimes other animals such as cats, foxes and raccoons are infected with the worm through the bite of a mosquito carrying the larvae of the worm.

    altIt is dependent on both the mammal and the mosquito to fulfill its life cycle. The young worms (called microfilaria) circulate in the blood stream of the dog. These worms must infect a mosquito in order to complete their lifecycle. Mosquitoes become infected when they blood feed on the sick dog. Once inside the mosquito the microfilaria leave the gut of the mosquito and live in the body of the insect, where they develop for 2-3 weeks. After transforming twice in one mosquito the third stage infective larvae move to the mosquito’s mouthparts, where they will be able to infect an animal. When the mosquito blood feeds, the infective larvae are deposited on the surface of the victim’s skin. The larvae enter the skin through the wound caused by the mosquito bite. The worms burrow into the skin where they remain for 3-4 months. If the worms have infected an unsuitable host such as a human, the worms usually die. The disease in dogs and cats cannot be eliminated but it can be controlled or prevented with pills and/or injections. Some risk is present when treating dogs infected with heartworms but death is rare; still prevention is best. Of course good residual mosquito control practices reduce the threat of mosquito transmission. Until the late sixties, the disease was restricted to southern and eastern coastal regions of the United States. Now, however, cases have been reported in all 50 states and in several provinces of Canada.

    Arthropod-borne viruses (arboviruses) are the most diverse, numerous and serious diseases transmitted to susceptible vertebrate hosts by mosquitoes and other blood-feeding arthropods. Arboviral encephalitides are primarily zoonotic, being maintained in complex life cycles involving a nonhuman primary vertebrate host and a primary arthropod vector. These cycles usually remain undetected until humans encroach on a natural focus, or the virus escapes this focus via a secondary vector or vertebrate host as the result of some ecologic change. Humans and domestic animals can develop clinical illness but usually are “dead-end” hosts because they do not produce significant viremia, and do not contribute to the transmission cycle. There are several virus agents of encephalitis in the United States: West Nile virus (WN), eastern equine encephalitis (EEE), western equine encephalitis (WEE), St. Louis encephalitis (SLE), La Crosse (LAC) encephalitis, dengue and yellow fever all of which are transmitted by mosquitoes. Another virus, Powassan, is a minor cause of encephalitis in the northern United States, and is transmitted by ticks. A new Powassan-like virus has recently been isolated from deer ticks. Encephalitis is global, in Asia, for example, about 50,000 cases of Japanese encephalitis (JE) are reported annually.

    Dengue is a serious arboviral disease of the Americas, Asia and Africa. Although it has a low mortality, dengue has very uncomfortable symptoms and has become more serious, both in frequency and mortality, in recent years. Aedes aegypti and Ae. albopictus are the vectors of dengue. These mosquitoes prefer to lay their eggs in containers close to human habitations and are not well-controlled by standard spraying techniques. The spread of dengue throughout the world can be directly attributed to the proliferation and adaptation of these mosquitoes. Over the last 16 years dengue has become more common, for example; in south Texas 55 cases were reported in 1999 causing one death. More recently, Hawaii recorded 85 cases of dengue during 2001 and the Florida Keys reported over 20 cases in 2010. In 2004 Venezuela has reported more than 11,600 cases classic dengue fever and over 700 cases of DHF. Indonesia dengue outbreak has caused over 600 deaths and more than 54,000 cases. In 1999, Laredo and Nuevo Laredo had an outbreak of almost a 100 cases.

    In 2010, Puerto Rico experienced its largest outbreak, with 21,000 cases reported. In 2009, Florida reported the first cases of local dengue transmission in 75 years, within Old Town, Key West. A serosurvey of residents suggested an infection rate of 5%, indicating serious risk of transmission. Despite thorough control efforts carried out by the county and state in early 2010, by the end of 2010, Florida had reported an additional 65 locally acquired dengue cases. All the cases were in Key West, except two cases in two more northerly counties.

    Yellow fever, which has a 400-year history, at present occurs only in tropical areas of Africa and the Americas. It has both an urban and jungle cycle. It is a rare illness of travelers anymore because most countries have regulations and requirements for yellow fever vaccination that must be met prior to entering the country (http://www.cdc.gov/ncidod/dvbid/yellowfever/index.htm). Every year about 200,000 cases occur with 30,000 deaths in 33 countries. It does not occur in Asia. Over the past decade it has become more prevalent. In 2002 one fatal yellow fever death occurred in the United States in an unvaccinated traveler returning from a fishing trip to the Amazon. In May 2003, 178 cases and 27 deaths caused by yellow fever were reported in southern Sudan. In the Americas 226 cases of jungle yellow fever have been reported with 99 deaths (ProMed 12-22-03).

    Eastern Equine Encephalitis (EEE) is spread to horses and humans by infected mosquitoes. It is among the most serious of a group of mosquito-borne arboviruses that can affect the central nervous system and cause severe complications and even death. EEE is found in freshwater hardwood swampland in the Atlantic and Gulf Coast states in the eastern part of North America, Central and South America, and the Caribbean. It has a complex life cycle involving birds and a specific type of mosquitoes including several Culex species andCuliseta melanura. These mosquitoes feed on infected birds and become carriers of the disease and then feed on humans, horses and other mammals. EEE cannot be transmitted from humans or other mammals because the viremia presented in the disease is not sufficient to further transmission. Thus, humans and other animals are known as “dead-end hosts.” Symptoms may range from none at all to a mild flu-like illness with fever, headache, and sore throat. More serious infections of the central nervous system lead to a sudden fever and severe headache followed quickly by seizures and coma. About half of these patients die from the disease. Of those who survive, many suffer permanent brain damage and require lifetime institutional care. There is no specific treatment. A vaccine is available for horses, but not humans.

    St. Louis Encephalitis (SLE) is transmitted from birds to man and other mammals by infected mosquitoes (mainly some Culex species). SLE is found throughout the United States, but most often along the Gulf of Mexico, especially Florida. Major SLE epidemics occurred in Florida in 1959, 1961, 1962, 1977, and 1990. The elderly and very young are more susceptible than those between 20 and 50. During the period 1964-1998 [35 years] a total of 4478 confirmed cases of SLE were recorded in the United States Symptoms are similar to those seen in EEE and like EEE, there is no vaccine. Mississippi’s first case of St. Louis Encephalitis since 1994 was confirmed in June 2003. Previously the last outbreak of SLE in Mississippi was in 1975 with over 300 reported cases. It was the first confirmed mosquito-borne virus in the United States in 2003. It turned up in October 2003 in California Riverside County in sentinel chickens. The last [SLE] human case in California occurred in 1997. In Louisiana in 2003 there was a fatal St Louis Encephalitis case previously listed as a West Nile caused death.

    LaCrosse encephalitis (LAC) is much less widespread than EEE or SLE, but approximately 90 cases occur per year occurs in all 13 states east of the Mississippi, particularly in the Appalachian region. It was reported first in 1963 in LaCrosse, Wisconsin and the vector is thought to be a specific type of woodland mosquito (Aedes triseriatus) called the tree-hole mosquito, with small mammals the usual warm-blooded host. Infrequent fatalities occur in children younger than 16. It is not transmissible from human to human. There is no vaccine for LaCrosse encephalitis.

    Western Equine Encephalitis (WEE) was first recognized in 1930 in a horse in California. It is found west of the Mississippi including parts of Canada and Mexico. The primary vector is Culex tarsalisand birds are the most important vertebrate hosts with small mammals playing a minor role. Unlike LAC it is nonspecific in humans and since 1964 fewer than 1000 cases have been reported As with EEE a vaccine is available for horses against WEE but not for humans. In Arizona 3 counties have been found with sentinel chicken flocks seroconverting to WEE.

    West Nile virus (WNV) emerged from its origins in 1937 in Africa (Uganda) into Europe, the Middle East, west and central Asia and associated islands. It is a Flavivirus (family Flaviviridae) with more than 70 identified viruses. Serologically, it is a Japanese encephalitis virus antigenic complex similar to St. Louis, Japanese and Murray Valley encephalitis viruses. Similar to other encephalitises, it is cycled between birds and mosquitoes and transmitted to mammals (including horses) and man by infected mosquitoes. WNV might be described in one of four illnesses: West Nile Fever might be the least severe in characterized by fever, headach, tireness and aches or a rash. Sort of like the “flu”. This might last a few days or several weeks. At least 63% of patients report symptoms lasting over 30 days, with the median being 60 days. The other types are grouped as “neuroinvasive disease” which affects the nervous system; West Nile encephalitis which affects the brain and West Nile meningitis (meningoencephalitis) which is an inflammation of the brain and membrane around it. (CDC)

    It first appeared in North America in 1999 in New York (Cornell Environmental Risk Analysis Program) with 62 confirmed cases and 7 human deaths. Nine horses died in New York in 1999. In 2001, 66 human cases (10 deaths) were reported in 10 states. It occurred in birds or horses in 27 states and Washington D.C., Canada and the Caribbean. There were 733 horse cases in 2001 with Florida reporting 66% of the cases; approximately 33% were fatal. In 2001 more than 1.4 million mosquitoes were tested for WNV. In the United States (2004) over 43 species of mosquitoes have tested positive for WNV transmission, the Culex pipiens group seems the most common species associated with infecting people and horses. Currently, 65 mosquito and 300 bird species have tested positive in the United States for this virus.

    During 2002, the number of areas reporting WNV grew to 44 states and 5 Canadian provinces. The only states not reporting WNV were Alaska, Arizona, Hawaii, Nevada, Oregon and Utah that year. Intrauterine transmission (CDC MMWR) and laboratory infections (CDC MMWR) were reported for the first time. In all over 3800 human cases with 232 fatalities in 39 states and Washington DC were recorded. More than 24,350 horse cases of WNV were confirmed or reported in 2002. There is a vaccine for horses. Even alligators (CDC-EID) were found infected in Georgia.

    The first confirmed 2003 WNV infection was in South Carolina on July 7th, 2003. South Dakota confirmed a WNV infection in a dog. The final CDC report list 9858 cases. Nebraska had 1942, Colorado 2947 and Idaho only one (CDC) . In Florida there were 94 human cases with most occuring in the panhandle. Bay county, FL reported 14 cases and one death. Of the more than 9858 cases, 6829 were West Nile Fever ( the milder form), 2863 were neuroinvasive (the more severe form) and 166 clinically unspecified. There were over 4200 positive dead birds reported in 39 states and 4500 plus infections in horses in 40 states with more than 425 of these in Colorado. West Nile was reported in 1377 sentinel chicken flocks from 15 states. In Florida 1173 seroconversions to WNV were reported from 34 counties. More than 1950 positive mosquito pools were reported from 32 states and New York City.

    In Canada (01-12-04) WNV was been confirmed in 9 Provinces. At least 10 human deaths and more than 1220 cases have been confirmed. Canada reported over 445 presumed or confirmed horse cases in 6 Provinces with over 180 in Alberta Province. Five Provinces have reported positive mosquito pools (>575) with over 290 from Manitoba. Canada confirmed over 1600 positive dead birds from 12000 tests.
    Mexico (December 2003) has tested over 590 citizens in 25 states. Six have tested positive with three with the more severe form of WNV. Mexico horse data shows 2475 had positive WN returns in 29 states. Of more than 18000 birds tested 117 were positive. The Pan American Health Organization (PAHO).

    Arizona and New Mexico reported the first human cases of WNV on May 26, 2004 and a week later confirmed a total of 7 cases. South Dakota reported it’s first case on June 8, 2004. In 2003 South Dakota had 14 deaths and over human cases reported. Wyoming and Florida (http://www.heraldtribune.com/) has joined the list recently. Alabama, Arizona, Texas and Virginia have reported WN V infections in horses. WNV seroconversions have been reported in 64 sentinel chicken flocks from 4 states (Arizona, California, Florida, and Louisiana), and 58 WNV-positive mosquito pools have been reported from 6 states (Arizona, California, Illinois, Indiana, Louisiana, and Pennsylvania).

    As of 2014, there have been 36,437 cases of WNV reported to CDC. Of these, 15,774 have resulted in meningitis/encephalitis and 1538 were fatal. CDC estimates that there have been at least 1.5 million infections (82% are asymptomatic) and over 350,000 cases of West Nile Fever, but the disease is grossly under reported due to its similarity to other viral infections.

    Canada’s 1st dead bird (a blue jay) from West Nile virus in 2004 was confirmed in Ontario in May 2004. West Nile virus was confirmed in 2 birds in Puerto Rico near the former US Roosevelt Roads Navy Base (southeastern Puerto Rico).

    Britain’s Health Protection Agency has started its annual surveillance program for possible human cases of West Nile virus infection. The program, which has been used for the last three years, operates during the summer, when there is West Nile virus activity in other countries. The UK has had no reported WNV, but are developing a West Nile Virus Contingency Plan.

    Zika virus has emerged from its origins in central Africa and has rapidly spread to the South Pacific and western hemisphere. A Flavivirus related to West Nile, Yellow Fever, St Louis and the equine encephalitides, Zika was first discovered in macaque monkeys in 1947 in the Zika Forest region of Uganda. Since its discovery in 2014 off the coast of South America, Zika cases have been found in 35 countries in the Americas.

    As of 28 April, 2016, there have been 426 reported cases of Zika virus due to travel to endemic areas. However, local transmission within the continental United States has, as yet, not been reported. In US Territories in the Caribbean, a total of 599 cases have been reported, with 596 being locally acquired, primarily in Puerto Rico and the US Virgin Islands.

    Although in rare cases Zika can be spread through sexual contact with an infected person, it is usually transmitted through the bit of an infected Aedes agypti or Aedes albopictus mosquito. The illness is usually quite mild, with fever, rash, conjunctivitis and joint pain lasting a few days to several weeks or months. Often patients are not sick enough to seek medical treatment so a great many cases are not reported. It is thought that one attack confers immunity. However, cases of microcephaly, a congenital defect of cranium and brain size resulting in profound neurological defects in newborns usually resulting in death have been been positively identified as being caused by Zika infection. An autoimmune condition called Guillain-Barré syndrome, causing damage to nerve cells resulting in muscle weakness and, on occasion, paralysis and death has been linked to Zika infection.

    The mosquito vectors of Zika virus are peridomestic, preferring to lay their eggs above the waterline of containers, treeholes, creases in tarpaulins and other vessels that may contain water. Aedes aegypti, in particular, will lay eggs in a series of containers after feeding. Both Aedes agypti and Aedes albopictus will feed day or night when a potential host comes within their limited flight ranges. Aedes agypti has more of a tendency to enter and stay within houses if conditions are proper. This species is exceedingly skittish, often leaving its host prior to taking a full blood meal when the host moves. Both mosquitoes also seem to prefer feeding on the host’s lower extremities.

    Traditional outdoor ULV sprays are ineffective against Aedes agypti, it being difficult to obtain contact with the spray droplets in flight due to its cryptic habits. Some success with ULV sprays has been obtained against Aedes albopictus in urban areas, while suburban areas remain refractory. The primary means of controlling both species is to eliminate their oviposition habitats by removing water bearing containers or emptying them and scrubbing the insides to remove eggs deposited above the waterline. Personal protective measures such as application of EPA-registered repellents and wearing of long-sleeved shirts and long pants are also effective measures.

    When traveling to areas endemic for Zika in the Caribbean, it is also recommended to stay in hotels with air conditioning and window and door screens to keep mosquitoes outside. If available, it is advised to sleep under mosquito bed nets.

    Integrated Mosquito Control