TECHNICALMosquitoes coming?

www.pestmagazine.co.uk July & August 201332 pest

Mosquitoes

There is a growing awareness of rising mosquito numbers andthe threat of future increases. Professional pest controllers shouldbe taking note of both the threats and opportunities this bringssay Dr Julian Entwhistle and Rob Fryatt of Xenex Associates.

bring both threats

& opportunities

Rob Fryatt, left, with Dr Julian Entwhistle

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Asian tiger mosquito, Aedes albopictus, begins a blood-meal

Patch makes us invisible to

mosquitoes!Research at the University ofCalifornia, Riverside has led to thedevelopment of the world's firstproduct that blocks the mosquito’sability to efficiently detect carbondioxide, its primary method of tracking a human blood meal.

The University lab identified volatile odour molecules that canimpair, if not completely disrupt, a mosquito’s carbon dioxidedetection machinery. This has subsequently been developed byOlfactor Laboratories Inc to produce the Kite Mosquito Patch.

The company said this July that the product marks a significantadvancement in the global fight against mosquito-bornediseases such as malaria, West Nile Virus and dengue fever.

The first Kite Mosquito Patches will be tested in Uganda, one ofthe hardest hit countries in Africa, where hundreds of thousandsdie annually of malaria.

The time is right for the pest management industry to become moreaware of the threats and opportunities of the rising numbers ofmosquitoes in the UK and there are some important lessons from theexperience in other countries.

The rapid spread of West Nile Virus in the USA at the beginning ofthis century created opportunities for the pest control industry there.From few companies specialising in mosquito control activity beforethe first cases, now more than 30% of the pest managementcompanies in the USA are involved in mosquito control work.

To some, these insects may not be well understood and theirmonitoring and control techniques may be new to others. This articlereviews, in brief, the threats and opportunities that increasingnumbers of mosquitoes create.

To start with there are 33 species of mosquito in the UK, more than20 of which bite humans. They have life cycles of as little as twoweeks in hot weather. The females typically lay several batches ofover 100 eggs at a time, so they can become extremely abundantand troublesome when conditions are in their favour.

According to research by Dr Jolyon Medlock, head of public healthentomology at Public Health England and other researchers, 57

local authorities received complaints about mosquito bites in the tenyear period from 1999 to 2009 – a substantial increase over theprevious ten years. In addition, there are around 4,000 calls to theNHS Direct helpline about mosquito bites in July and August eachyear – a figure that increased yet again last summer. So mosquitoesare already significant pests in the UK and the problem isincreasing.

The question is how much worse will the problem get and how canthe pest management industry prepare for it? To answer this, let'slook at the threats mosquitoes pose and the opportunities that mayemerge for their control.

The first threat is due to climate change with warmer temperaturesand wetter weather. The warmer temperatures allow greater survivalover winter and more generations per year whilst the wetter weathermeans more go through from egg to adult stage. So climate changealone will continue to favour our resident mosquitoes and increasethe problems they bring of nuisance biting in hot and humidsummer days.

Climate change will also make the UK more attractive for mosquitospecies that normally only occur in warmer countries, therebyincreasing the risk that more dangerous species will becomeestablished.

The second threat posed by mosquitoes is the transmission ofdiseases. We tend to think this is only relevant to the tropics where

Climate change favours mosquitoes

Disease transmission

TECHNICALMosquitoes coming?

July & August 2013 www.pestmagazine.co.uk 33pest

Thesimilar to Aedes albopictus and this hasled to scare stories about the UK arrivalof the Asian tiger mosquito

native Culiseta annulata looks

Comparison of native with invasiveCuliseta annulata Aedes albopictus

Culiseta annulata

(UK native species)Aedes albopictus

(the Asian tiger mosquito)

Body length(not including mouth parts)

6mm to 7mm 4mm to 5mm

Leg length 13mm to 14mm 7mm to 8mm

Wing span 13mm to 15mm approx 7mm to 8mm

Adapted from the Mosquito Watch Programme website (details provided by the Killgerm Group)

the transmission of malariaby mosquitoesstill leads to over half amillion deaths per year.Whilst dengue fever,transmitted by

, is responsible foraround half a millionhospital admissions.

The most likely mosquito-borne disease to causemajor public healthconcern in the UK is WestNile Virus (WNV) – as inthe USA. 237 human casesof WNV were reported insouthern EU countries in2012 and the disease isopen to being importedvia birds which can form areservoir of infection. Thequestion then is whethernative mosquitoes couldact as vectors and sustainan epidemic in the UK.

In 2005 Dr Jolyon Medlock, Prof KeithSnow and Dr Steve Leach documented 14UK species of mosquito that have beenimplicated in WNV transmission elsewhere.Many of these species can transmit WNVbetween birds and humans, so theingredients are already here for localtransmission once WNV enters the country.In 2012 Dr Nick Golding of Oxford

University and other researchers reported onthe arrival in East Kent of the main speciesresponsible for WNV transmission insouthern Europe, .

Following its entry into the USA in 1999,probably through an infected bird, WNVswept quickly from east to west and hassince spread into Canada and SouthAmerica. Last year was the worst in the USAsince 2003, with 5,674 cases in 48 states,including 286 deaths. WNV has now beenidentified in over 40 different mosquitospecies in the US with species themost important.

A competent vector of WNV in southernUSA is the Asian tiger mosquito,

, which often occurs in towns andcities and readily bites humans. It is alsocapable of transmitting other virusesincluding chikungunya and dengue fever.

Dr Medlock and others have examined thepotential for this mosquito in the UK. Theyhave concluded that conditions would permit

it to survive throughout large lowland areaswith at least four to five months of adultactivity (May-September), and moreprolonged in the urban centres aroundLondon and the southern coastal ports.

However, all UK birds tested so far have animmunity to WNV and this is often putforward as one of the reasons why the riskof WNV spread in the UK is low. It mayenter in an infected bird but the spreadwould be less rapid, if at all.

is the most invasive mosquitospecies in the world. It originated in the FarEast and invaded Africa, Europe, North andSouth America primarily through eggstransported in used car tyres. As the UKimports up to one million used tyres everyyear it is quite likely to arrive by this means.Imports of the houseplant Lucky Bamboo canalso harbour this mosquito which has nowbeen reported present in 19 Europeancountries.

Anopheles

Aedes

aegypti

Culex modestus

Aedes

albopictus

Ae Albopictus

West Nile Virus threat

Most invasive species globallyCulex

Established

Introduced

Absent

No data

Unknown

Aedes albopictusCurrent known distribution March 2013

Azores (PT)

Canary Islands (ES)

Madeira (PT)

Svalbard/Jan Mayan (NO)

Outermost regions

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www.pestmagazine.co.uk July & August 201334 pest

Significant public health threat

There have been several scare stories aboutthe arrival of in the UK butsuspected cases checked by Mosquito Watch(www.cieh.org/policy/npap_mosquito_watch.html) and other laboratories have allproved to be unfounded so far, due toconfusion with the somewhat similar lookingnative . The threat ofinvasion of WNV or chikungunya into theUK is therefore very real and the presence of

in the country would be asignificant public health threat.

Invasion by other vectors is also possible.

More extreme scenarios become more likelywith climate change. These potentiallyinclude the re-emergence of malaria -–

. This was present in the18th and 19th centuries in the marshlandsand estuaries of East Anglia, Essex, Kentand the counties of the south coast ofEngland, transmitted by the native

.

In addition, there is potential for survival of, the vector of dengue and

yellow fever – an outbreak of yellow feverresulting from a ship docked in Cardiff in1865 caused some 30 cases in localresidents. This may seem way back in thepast, but the occurrence of locallytransmitted cases of dengue fever in Franceand Croatia in 2010, and the fact that

also transmits dengue, showsthat this scenario is not so remote as it mayat first seem.

The final threat posed by mosquitoes in theUK is the lack of capacity and skills tocontrol them! In spite of the increasingproblems, only 11 local authorities state thatthey undertake mosquito control and activesurveillance. Very few regulatory approvalsare now held in the UK for professionalmosquito insecticides. Control has becomelargely dependent on environmentalmanagement to reduce the areas suitable forthe larvae and the deployment oflarvicide, alongside limited adult mosquitotrapping and personal protection measuressuch as repellents, window screens andmosquito nets.

Although the UK has leading internationalscientific expertise in mosquito management,through the world renowned London andLiverpool Schools of Tropical Medicine and,in addition, since 2005 a mosquito nuisancereporting scheme for environmental healthofficers, it is questionable whether there aresufficient skills, experience and capacity atthe operational and organisational level to

cope with the increasing mosquito problemand the threat of invasion by non-nativespecies and transmission of mosquito-bornediseases in the UK.

The good news is that many of our majorinsecticide suppliers have excellent mosquitocontrol experience within their globalorganisations, accompanied by effectiveand proven mosquito products, which theycould call upon.

In addition, our industry colleagues inmarkets such as Italy have good practicalexperience in managing and monitoringmosquito outbreaks.

Now is the time to make sure that the UKindustry understands the problem, identifiesthe skills required and is preparing tomanage the future threat. After all,mosquitos do not understand or respect thenational borders that have allowed us tokeep many other potential invaders away!

Ae. albopictus

Culiseta annulata

Ae. albopictus

Plasmodium vivax

Anopheles atroparvus

Aedes aegypti

Ae.

albopictus

Bti

Skills gap in control

Good news

Mosquitoes love...According to an article in the Jackson, Mississippi daily newspaper, thethere are some things that turn us humans into attractive blood buffets!

Turns out that Blood Type ‘O’, the most common type, is like a chocolate sundae formosquitoes. They are twice as likely to land on a Type ‘O’ carrier than a Type ‘A’ person.Type ‘B’ blood is about halfway on this scale.

But the biggest attractant is carbon dioxide and that puts us all on a level playing field - wellnot quite. The bigger you are the more carbon dioxide you exhale. Pregnant womenregardless of their size, produce roughly 27% more carbon dioxide than usual becoming amagnate for mosquitoes.

Fitness fanatics however are also more attractive. Chemicals released when working-outdraw mosquitoes like a moth to a flame. It's a Catch-22, if you're not active then you couldput on a few pounds and breathe more, which is just as attractive to mosquitoes. The colourof your clothes can also draw them in – in order of attractiveness it’s black, blue and red.

Clarion Ledger

CIEH calls for action

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Useful CIEH mosquito report

The Chartered Institute of Environmental Health (CIEH), at its public health conferenceheld in Cardiff on 8-9 May 2013, requested that Government should act on the followingrecommendations:

Implement an EU-wide policy on mosquito control. It is necessary to intensifyinternational and European collaboration at legislative and executive levels;

Notification systems across Europe should be standardised and notifications reportedto a central agency;

Harmonisation of mosquito control practices to reduce harm to the environment. EUguidelines for insecticides should be harmonised between member states;

Enhanced human and veterinary surveillance activities will assist public healthauthorities to implement control measures at source;

The general population, especially in the affected areas, should be informed aboutthe typical presentation of the disease and vectorcontrol strategies, particularly in the domesticenvironment.

Whist this report was published by the CIEH in May2009, the 24-page booklet provides a useful overviewof mosquitoes in the UK and the problems they pose.Written by Dr Colin Malcolm from the School ofBiological & Chemical Sciences at Queen MaryCollege, University of London, copies can bedownloaded from the NPAP publications section ofthe CIEH websitewww.cieh.org/policy/npap_publications.html