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Integrated vector control approach

Dr. Kulrajat Bhasin

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Plan of presentation

• Introduction• Principles of vector control• Integrated vector control approach.• Selection criteria for vector control measures• Evolution of Integrated vector control approach.• Integrated vector control approach for mosquito.• Key elements of an IVC Strategy.• References.

Introduction• Vector - definition

• Common vectors and diseases

- Mosquito : Malaria, filaria, viral encephalitis e.g.., Japanese encephalitis, viral fevers e.g.., Dengue, west Nile.

- Housefly : typhoid and Para typhoid fever, diarrhea, dysentery, cholera, gastroenteritis, amoebiasis, helminthic infestations, poliomyelitis, conjunctivitis, trachoma, anthrax, etc.

- Sand fly : Kala azar, oriental sore, sand fly fever, oraya fever

• Transmission of disease- Direct contact, mechanical, biological (propagative, cyclopropagative, cyclodevelopmental).

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Principles of vector control

1. Environmental control: the best approach as the results are likely to be permanent.

2. Chemical control 3. Biological control4. Genetic control5. Newer methods like insect growth regulators,

chemosterilents, pheromones

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Integrated vector control approach• No single method is likely to provide a solution in all situations. The

present trend is to adapt a IVC approach.

• Vector control approach combining two or more methods with a view to obtain maximum results with minimum efforts.

• “Integrated vector control approach is the present trend for vector control defined as utilization of all appropriate technological and management techniques to bring out an effective degree of vector suppression in a cost effective manner and also to avoid the overuse of one of the methods”.

• Selection of methods is not possible without detailed field information on the ecology, bionomics of vectors, role in disease transmission.

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Life cycle of Mosquito

4 Common stages in development namely : 1. Egg, 2.Larva , 3.pupa and 4. adult

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Habits of vectorsA knowledge of these habits is essential from the point of

view of controlling them as well as the part they play in transmission of disease

Mosquito 1. Feeding habits: • males never bite and subsist on plant juices• females on the other hand are

hematophagus2. Time of biting: generally evening (aedes fearless

females)3. Resting habits: exophyllic . Vegetations, shrubs ,

tree holes, cattle sheds.4.Breeding habits: anopheles-prefer clean water culicines - dirty polluted water. aedes - artificial collections of water( rainy

season) mansonia – aquatic plants( water hyacinth5. Hibernation: in winters or when condns not

favorable in adult stage6. Dispersal : not far unless swept away with air

currents( yellow fever) 7. Life span : normally varies from 8 – 34 days but

males as a rule are short lived

Housefly1. Breeding habits : in order of importance are• Fresh horse manure• Human excreta• Manure of other animals• Garbage• Decaying fruits and vegs• Organic rubbish dumps• Liquid wastes scattered on ground2. Feeding habits : does not bite, mechanical

transmission. Cannot eat solid food so vomits and making a soln sucks in a liquid state

3. Restlessness : moves to and fro.4. Vomit drop : fly vomits frequently which is a

culture of disease agents5. Defecation : habit of defecating depositing

bacteria on exposed food6. Resting habits : on vertical surfaces and hanging

objects and tendency to fly towards light.7. Dispersal : up to 4 miles or more from point of

origin

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Selection criteria for vector control measures

1. Effectiveness.2. Safety.3. Simplicity of use- indications, contraindications,

skills, difficulties in using.4. Cost5. Time and effort6. Type of benefit.7. Social acceptability- local context.8. Support requirements.

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Evolution of the integrated vector control

• Vector control has been a part of malaria control activities since the early 20th century.

• During the pre-DDT era, reduction of vector mosquitoes largely relied on larviciding & environmental management of breeding habitats.

• 1950s- DDT and other insecticides were extensively used.

• 1970s, development of insecticide resistance, poor human acceptance and environmental concerns against the use of insecticides.

• This led to a rethinking in vector control strategies.

• 1980s, WHO proposed an Integrated Vector Control (IVC) strategy based on the principles of Integrated Pest Management in agriculture.

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Mosquito Control Measures

Anti larval measures

Anti adult measures

Protection against mosquito bites

Legislative control

1. Environmental control

2. Chemical control

3. Biological control

1. Space sprays

2. Residual sprays

3. Genetic control

1. Mosquito nets

2. Screening

3. Repellents

Civic laws

Integrated vector control approach for mosquito

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Anti-larval measures

Environmental controlThe most important step in reducing the number of mosquitoes 1.Elimination of breeding places (source reduction) like,

Filling and leveling Drainage of breeding places Water management

2.Proper disposal of refuse other wastes.3.Cleanliness in and around the houses .Community involvement & multisectoralcoordination

Chemical ControlLarvicide Formulation Duration

Petroleum oil- Diesel oil and Larvicidal oil Suspension 1-2 weeks

Paris green Granules 2 weeks

Organophosphorus compounds Abate Malathion FenthionChlorpyrifos

Emulsifiable concEmulsifiable concEmulsifiable concEC, Suspension

2-11 weeks1-3 weeks1-2weeks2-4 weeks

Insect growth regulators- Diflubenzuron, Methoprene, Pyriproxyfen

Suspension/ Granules

4-8 weeks

Bacterial Larvicides- Bacillus thuringiensis H-14B. Sphaericus

EC/ Granules 1-2 weeks2-8 weeks

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Insect Growth Regulators

• Highly toxic to insect larvae or pupae, interfering with development into adults. Used in large scales in USA..

• Costly & have restricted availability -not used in India.• Particularly useful if insects have developed resistance to

insecticides or because of their environmental effect.• Safe to human beings and environment. 1. Juvenile hormone analogues: prevent development of larvae

into pupa or pupae into adult. Ex. Methoprene2. Chitin synthesis inhibitors: interfere with moulting process,

killing larvae when they moult. Act more rapidly.Ex. Diflubenzuron and Triflumoron.

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Expanded Polystyrene Beads

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• Expanded form of polystyrene granules - available commercially with diameter ranging from 0.6 to 2.5 mm.

• Increased by boiling.• They do not decay and remain floating for years.• Spread on surface of water to form floating layer. A layer of 1-2

cm is sufficient if it covers the surface.• Easily blown or washed away- only sites where water remains

confined -wells.• Used safe in drinking water

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Biological Control

• Natural enemies into the environment-includes Insects,

Viruses, Bacteria, Protozoa, Fungi and Fish.

• Only two of them have become widely employed. They are

Larvivorous fish and Biolarvicides.

Biological Control

1.Larvivorous fish• Feed on mosquito larvae.• Easy, practical, cheap; they have no food value.• They should have the following characteristics

– Preference for mosquito larvae over other types of food – Small size – High reproduction rate– Tolerance to pollution, temperature fluctuation &

transportation. • Two species are widely used- Gambusia - clean water, tolerate wide range of temperature, pH

water salinities.Guppy- Polluted water, cannot <10 degree C.

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Larvivorous fish(contd)• Useful in ornamental tanks, wells, Garden ponds, fountains,

swimming pools, large water collection.

• Approximately 5 fish per sq.m of water surface.

Advantages

a. Long term effective control measure.

b. Cost effective.

c. Environmentally safe.

d. Controls variety of mosquito species.

Disadvantages

a. Effective when large numbers eventually establish themselves.

b. takes 1-2 months; not suitable - quick anti larval measures are

needed.

c. less effective in waters with much vegetation or floating garbage.17

2. Biolarvicides

• Bacteria for the control of mosquito larvae. Bacillus thuringiensis H 14 and Bacillus sphaericus.

• Available as wettable powder and granules which contain bacteria, spores and toxic crystals.

• Safe to environment , human being and animals but are expensive.

Bacillus thuringiensis H 14• Gram positive, spore forming bacteria which is specifically

acts against mosquito larvae.• Produces endotoxin which after ingestion causes gut

paralysis & leakage of contents into body cavity leading to death.

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Biolarvicides(contd)• It is applied at 0.5 gm/sq.m • 250gm of B. thuringiensis is mixed with 10 L of water to make

2.5% suspension & sprayed at 1L over 50 sq.m every 2 weeks. Bacillus sphaericus• It also produces toxin.• It is more effective in polluted water - suitable for treatment

of breeding sites of Culex.• 500gm of B. sphaericus with 10 L of water to make 5%

suspension & it is sprayed at 1 L over 50 sq.m. every 3 weeks.Others Biolarvicides- Fungi- Coelomyces, Culicinomyces,Nematodes – Romanomermis cluicivorax and R. iyengari.

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Anti-adult Measures

Space sprays – Space sprays are those where the insecticidal

formulations is sprayed into the atmosphere in the form of mist or fog.1. Thermal fog.2. ULV cold aerosols.

– Done where immediate results are needed like during outbreak of disease to bring down mosquito population drastically.

– Exophillic vector species.

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Space sprays (contd)Sl. no

Name of Insecticide

Formulation Preparation of formulation

Equipment used Remarks

1 Pyrethrum extract

2.0% extract 1:19 i.e., 1 part of 20% pyrethrum extract in 19 parts of kerosene

Flit pump or hand operated fogging machine

Used for indoor spray

2. Technical Malathion

5 parts of tech. Malathion in 95 parts of Diesel oil

Vehicle mounted thermal fogging machine Speed of vehicle 6 km/hour

Outdoor thermal fogging

Used for outdoor spray

3 Deltamethrin1.25ULV

1 litre in 199 litre Diesel

Thermal fogging machine

Outdoor thermal fogging

Used for outdoor spray

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Space Sprays

Advantages of space sprays• Immediate effect - suitable for control of disease outbreak.• Less insecticide is required for one application.• Kills exophillic species of mosquito.Disadvantages of Space sprays• Effect lasts for shorter period- repeated at least once a week.• The cost of equipment, operational and maintenance - high; • Needs specially trained staff for maintenance and repair.• May cause pollution.• Problems with acceptability.

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Indoor Residual Sprays

• Application of insecticides to surfaces so that the insecticide particles remain on the surface in the form, size and quantity suitable for insects to pick up on contact and sufficient to exert a lethal effect over a long period.

• Endophillic species.

Compression pneumatic sprayerKnapsack sprayer

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Indoor Residual Sprays

Sl.No.

Name of the insecticide Dosage Residual effect in weeks

1 DDT 50% wp 1 gm 10 -122 BHC 50% wp 200 mg 6 – 83 Malathion 25% wp 2 gm 6 – 84 Deltamethrin 2.5% wp 20 mg 10 -12

5 Alpha Cyperthrin 5.0% wp 25 mg 10 -126 Cyfluthrin 10% wp 25 mg 10 -127 Lamdadcyhalothrin 10% wp 25 mg 10 -128 Fenitrothion 40% wp 1 gm 6 – 89 Primiphs-methyl 25% wp 2 gm 6 - 8

Problems related to house spraying 1. May leave visible deposits on walls .2. Non acceptability.3. Painting or re-plastering of walls after application reduces or eliminates efficacy of insecticides.4. People may be reluctant to allow stranger into their houses.

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Genetic Control

• Methods such as1. sterile male technique2. Cytoplasmic incompatability3. Chromosomal translocations4. Sex distortion5. Gene replacement

Limitations:

1. Lack of mating competitiveness released males.

2. Immigration of fertile females from regions close to the

release sites.26

Zooprophylaxis

• Reallocation or introduction of cattle or domestic animals

between settlements and mosquito breeding i.e. ring of

cattle sheds on the outskirts of a village with houses in the

center.

• Many mosquito prefer animal blood than human blood and

hence decreases biting of human and transmission of

disease.

• In Japan it is proved to be effective against Culex.

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Personal Prophylaxis

a. Mosquito Nets• Mosquito bite during sleep. They also protect against other

creatures like spiders, cockroaches, lizards and rats.• Best pattern is rectangular net.• Size of the openings in the net is should not exceed 0.0475

inch in any diameter. The number of holes in one square inch is usually 150.

Disadvantages of Untreated Nets1. Mosquito can feed when body makes contact with the net.2. Hungry mosquito wait on or near the net until net is opened.3. After failing to get through the net Mosquito are diverted to

unprotected people sleeping nearby. 28

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Insecticides Treated bed Nets

• Provide better and effective protection by not only preventing mosquito bites & also killing them.

• They are prepared by soaking the net in insecticidal solution & dried.

• Nylon nets are preferred - more durable, insecticide stays longer duration and quicker in drying after impregnation.

• Synthetic Pyrethroids are used for impregnation. Permethrin,Deltamethrin, Cyfluthrin and Lambdacyhalothrin are used.

Personal Prophylaxis(contd)

b. Repellents • Mainly used for application on exposed parts of skin. • They act by preventing human-insect contact and do not

knock down or kill. • Chief advantage is short duration of protection. Useful for

Plantation workers, Army people, Labors who work outdoor at night and Travelers.

• N-N-Diethyl-3-toluamide (DEET),indalone, dimethyl pthalate, dimethyl carbate.

• DEET is best available product; effect last for 4-6 hours. on application.

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Personal Prophylaxis(contd)

c. Screening- Screening of buildings with zinc, aluminum, plastic or

bronze having 16 meshes to the inch is recommended.

d. Protective clothing.

d. Others- Mosquito hitting swatter, use of fan at high speed,

repellents.

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Personal Prophylaxis(contd)Insecticide Vaporizers• Protect against mosquito and biting flies by, 1. Irritating and disturbing them after contact and preventing

them from biting and also preventing them entering room. 2. Paralyzing or killing them.• Coils, mats, liquid vaporizers and aerosols/spray- Transfluthrin, Legislative control• Use of laws to prevent / reduce propagation and spread of

vectors is an effective means of vector management, through stringent approach.

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IVC

BiologicalSource

reduction

Health Education

Personal Protection

Chemical

•Community•School education•TV•Mass media

Bed nets and repellents

•Insect growth regulators•Adulticides•Larvicides

•Intermittent irrigation•Water level management•Land filling•Channelling•Draining

•Exotic natural enemies•Larvivorous fish•Microbial agents

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Key elements of an IVC Strategy

1. Advocacy, social mobilization and legislation

– Promotion and inclusion of IVC principles.

– Empowerment of communities for sustainability.

– Establishment or strengthening - regulatory & legislative control for public health.

2. Collaboration within the health sector and other sectors:

– Agriculture and agriculture development projects.

– Urban sector;

– Industrial development;

– Infrastructure development projects;

– Water resources development projects;

– Housing projects;

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3. Integrated approach• IRS in high risk areas and in epidemic situations based on

vector behavior and community acceptance.• Use of insecticide-treated nets/long-lasting insecticidal nets

and other personal protection methods.• Environmental management.• Biological control.4. Evidence-based decision making• IVC strategy requires assessment of the vector control needs

based on the local factors. • Demands efficient surveillance/ information management

system that highlights targets for vector control interventions.

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5. Operational and implementation research• Strong operational and implementation research support for

development of new and modified tools6. Capacity building• expertise at the central, as well as peripheral levels.• developing tools and guidelines in local languages and training

of personnel for vector control.7. Monitoring and evaluation• indicators as per the local requirements and targets set.• Inputs, costs & outcome of different interventions, when used

singly or in combination & simultaneously or consecutively in a defined area, must be monitored.

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Thank you