Vector Borne Diseases and Vector - PowerPoint Presentation

Slide1

Vector Borne Diseases and Vector Control

 

Slide2

Vectors

Vectors are invertebrates or

arthropods

or animals which transmit disease either through ingestion, injection or contact.

Slide3

Nuisance Pests: Cockroach

A female German cockroach only needs to mate once. She can fertilize all the eggs she will produce in her 9 month lifespan and produce about 200 offspring

Slide4

Rats and Fleas

There are about 1600 species of fleas in the world

A single adult pair of rats can produce 500 offspring in a year. A pair of breeding owls which produce five to six chicks in a year can eliminate up to 3,000 rats in a year

Slide5

Vector-borne Disease Burden

The major burden of disease in the African region is attributable to vector borne diseases. These include malaria, lymphatic filariasis,

trypanosomiasis

, onchocerciasis,

schistosomiasis, dracunculiasis, yellow fever and dengue fever.

It is estimated that 90% of global clinical malaria cases (300 million) and malaria related deaths (1 million) annually occur in the continent. About 55 million people are at risk from trypanosomiasis.

Although onchocerciasis is controlled in 11 West African countries, the disease is still a public health problem in 19 countries including Nigeria. Plague also remains a problem in at least 11 countries and outbreaks in Nigeria have recently been reported.

Leishmaniasis is endemic mainly in East Africa where a sharp increase in the number of cases has been observed. There are 164 million people infected with

schistosomiasis and 477 million people are at risk world wide. The incidence of Guinea worm has been dramatically reduced but substantial efforts are still needed in Nigeria and some countries.

Slide6

Guineaworm Lifecycle

Slide7

Guineaworm

Countries

Slide8

Guineaworm

Guinea worm enters the body when people drink water containing

cyclops

. infected with the guinea worm larvae.

Cyclops die in the stomach and release the guinea worm larvae to move through tissue in the intestines.

Male and female worms mate after about three months. The male worm dies.

After about eight months, the mature female worm moves toward the surface of the skin (usually the lower limbs).

After about one year from the time the person drank the infected water, the worm is ready to emerge from the body. The infected person has felt no effects up to this time. A painful blister forms. Infected people try to relieve the pain by immersing the sore in the water.Contact with water causes the guinea worm to emit its larvae,

recontaminating the water source and perpetuating the cycle of the disease.

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Schistosomes

(also known as Blood fluke) are one of the major human

helminth

parasites endemic in 74 developing countries, threatening 650 million people and causing severe morbidity especially in children under the age of 14 (WHO, 2008). It is due to a

trematode

of the genus

Schistosoma

, of which 5 species are the principal causes of the human disease, i.e

S.

mansoni, S.

haematobium

, S.

japonicum

, S.

mekongi

and

S.

intercalatum

.

Slide10

Onchocerciasis

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Trypanosomiasis

Trap using pheromones

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Factors to consider in vector control

Life history of vector: Most of the vectors are insects with complete or incomplete metamorphosis

Habits: knowledge of feeding, resting and flying habits

Cost of control

Ecological consideration: it helps to envisage how the plan of action will affect the totality of the environment. It is important that an Environmental Impact Assessment (EIA) of the planned action be carried out before proceeding.

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Typical Stages in the Life Cycle of Mosquito

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Slide15

Malaria

Plasmodium

falciparum

occurs throughout tropical Africa and in parts of Asia, the Western Pacific, South and Central America, Haiti and the Dominican Republic;

Plasmodium

vivax

is almost absent from Africa but is the predominant malaria parasite in Asia and South and Central America;

Plasmodium

malariae

is found worldwide but has a very patchy distribution;

Plasmodium

ovale

occurs mainly in tropical West Africa and rarely in the Western Pacific.

Anophelis

gambiae

A,

funestus

Slide16

Epidemiology of Malaria in Nigeria

S/N

ecological zone

states

Transmission period (months)

Strata definition

Malaria vectors

1

Sahel Savannah

Borno and Yobe

1-3

Unstable/ epidemic prone

An

arabiensis

2

Sudan Savannah

Adamawa, Bauchi, Gombe, , Katsina, Jigawa, Kebbi, Sokoto and Zamfara.

4-6

Unstable/ epidemic prone

An

arabiensis

3

Guinea Savannah

Kogi, FCT, Benue, , Taraba, , Nassarawa,

4-6

Unstable/ epidemic prone

An

arabiensis

4

Forest Mosaic

, Kwara, Ondo, Ekiti, Anambra

4-6

Unstable/ epidemic prone

An

arabiensis

5

Forest

Lagos, Ogun, Osun, Oyo, Delta, Ebonyi, Edo, Imo and Abia.

7-9

Unstable/ epidemic prone

An

arabiensis

6

Mangrove

Cross River, Akwa Ibom, Rivers, Bayelsa

9-12

Stable

An

gambiae

& An

funestus

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National Vector Control ProgrammesThere are established programmes aimed at the control, eradication and or elimination of these vector borne diseases: - - Roll Back Malaria,

- Nigerian Guinea worm Eradication

Programme

(NIGEP), - National Onchocerciasis

Control Programme, - National Schistosomiasis control

- Lymphatic filariasis elimination programme, - Trypanosomiasis eradication programme etc.

Slide19

Mites, Ticks – Other

Acari

,

Reduvid

bug

Mites and ticks which feed on vertebrate hair or blood often carry disease organisms, such as spirochete bacteria, responsible for relapsing fever and Lyme disease.

Others are rather unpleasant parasites themselves, such as ticks, chiggers, and the skin mites that cause mange and scabies. Yet most mites are free-living, found in great abundance in soils, plant litter, and even in water.

In all there are about 30,000 species of

Acari

known, and that is probably only a fraction of the actual number of species.

Slide20

Bugs and Lice

Slide21

Vector Control Methods

Environmental Control

Chemical Control

Biological Control

Genetic Control

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Environmental Control

Water control

Drainage clearing

Filling burrow pits and abandoned ditches, holes

FlushingDrying of breeding places

Management of irrigation waterRemoval of marginal and other vegetation Removing shade where mosquitoes breed

Disposal of empty cans, discarded tyres

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Source Reduction

It consists of elimination of larval habitats or rendering of such habitats unsuitable for larval development.

Public education is an important component of source reduction.

What you/your family can do to prevent mosquito proliferation. e.g. Household drainage clearance and larviciding using oil or other agents.

Other forms of source reduction include open marsh water management, in which mosquito-producing areas on the marsh are connected by shallow ditches to deep water habitats to allow drainage or fish access. Rotational impoundment management, in which the marsh is minimally flooded during summer but is flap-gated to reintegrate impoundments to the estuary for the rest of the year.

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Biological Control

Biological control includes use of many predators:

- dragonfly nymphs and other indigenous aquatic invertebrate predators such as

Toxorhynchites

spp.

- predacious mosquitoes that eat

larvae and pupae; however, - mosquito fish,

Gambusia

affinis and G.

holbrooki.

- Naturally occurring

Fundulus

spp. and possibly

Rivulus

spp., killifish

Mosquito fish are indiscriminate feeders that may eat tadpoles, zooplankton, aquatic insects, and other fish eggs and fry.

- The

entomopathogenic

fungus,

Laginidium

giganteum

,

has been registered for mosquito control by EPA under the trade name

Liginex

, - The pathogenic protozoon,

Nosema

algerae

,

(Not available).

-

Entomoparasitic

nematodes such as

Romanomermis

culicivorax

and

R.

iyengari

are effective;

- A predacious copepod,

Mesocyclops

longisetus

,

preys on mosquito larvae and is a candidate for local rearing with

Paramecium

spp. for food

.

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Genetic control

Genetic control will make use of male insects which will be sterilized and released into the field where they mate with several females but without producing any offspring. This is being tested and with the developments in biotechnology, it may be the technique of the future.

In the insect world, the female once mated will not go for mating with another male.

Slide26

When did we start using insecticides?

At the beginning of World War II (1940), insecticide selection was limited to several arsenicals, petroleum oils, nicotine, pyrethrum, rotenone, sulphur, hydrogen cyanide gas, and

cryolite

.

At the beginning of World War II (1940), our insecticide selection was limited to several arsenicals, petroleum oils, nicotine, pyrethrum, rotenone,

sulfur

, hydrogen cyanide gas, and cryolite. It was World War II that opened the

Modern Era

of

Chemical control with the introduction of a new concept of insect control --synthetic organic insecticides, the first of which was DDT.

It was World War II that opened the Modern Era

of

Chemical

control with the introduction of a new concept of insect control --synthetic organic insecticides, the first of which was DDT.

Slide27

Insecticides

Insecticides are agents of chemical or biological origin that control insects. 

Control may result from killing the insect or otherwise preventing it from engaging in

behaviors

deemed destructive.  Insecticides may be natural or manmade and are applied to target pests in a myriad of formulations and delivery systems (sprays, baits, slow-release diffusion, etc.). 

Slide28

Insecticides

Stomach poisons

Paris Green

Sodium fluoride

Natural

Pyrethrum

Rotenone

Derris

Nicotine

Mineral oils

Fumigants

Hydrogen cyanide

Methyl bromide

Sulfur dioxide

Carbon disulphide

Organophosphates

Chlorthion

,

Diazinon

,

Dioxothion

,

Demethoate

, EPN,

Malathion

(OMS1),

Fenthion

(OMS2), Methyl parathion, Parathion,

Ronnel

,

Trichlorfon

,

Dichlorvos

, Abate (OMS 786),

Naled

,

Gardona

,

Chlorpyrifos

,

Fenitothion

(OMS 43),

Dicaphthon

(OMS 214)

Organochlorine

compounds

DDT,

Methoxychlor

, BHC,

Lindane

, Heptachlor,

Dieldrin

,

Aldrin

,

Toxaphene

,

Kepone

,

Mirex

Repellents

Meta-

diethyltoluamide

Benzyl benzoate

Indalone

Dimethyl

phthalate

Ethyl

hexanediol

Carbamates

Carbaryl

Dimetilan

Pyrolan

Propoxur

(OMS 33)

Synthetic

pyrethroids

Resmethrin

Bioresmethrin

Pothrin

Slide29

Inorganic Insecticides

They are compounds of arsenic and fluorine but may also include compounds of sulphur and salts of zinc, copper, lead, mercury, chromium and selenium.

Mostly not very selective and not very toxic to insects; large quantities are required for effective control.

Most commonly used inorganic insecticides: copper arsenate, lead arsenate and

cryolite

; Paris Green, or copper

acetoarsenite

is a stomach poison; used as larvicides; is applied as 2% dust by mixing with soapstone powder or slaked lime; 1Kg/ha is recommended.Arsenials

are also important in the control of cattle ticks;

Slide30

Organochlorines

The

organochlorines

are insecticides that contain carbon (thus

organo

-), hydrogen, and chlorine. They are also known by other names:

chlorinated hydrocarbons, chlorinated organics, chlorinated insecticides, and

chlorinated synthetics.

The organochlorines

are now primarily of historic interest as more are banned. See DDT

Slide31

The Callous Spray of DDT

The United States used a lot of DDT during the mid-1900s

At one point, the US was producing 220 million pounds of DDT a year!

In 1958, nearly 80 million pounds of DDT was sprayed onto American farmlands.

Slide32

Organophosphates

OP

s is the term that includes all insecticides containing phosphorus.

Other names used, organic phosphates, phosphorus insecticides, nerve gas relatives, and phosphoric acid esters.

All organophosphates are derived from one of the phosphorus acids, and as a class are generally the most toxic of all pesticides to vertebrates. The OPs are generally divided into three groups--aliphatic, phenyl

, and heterocyclic derivatives.

Slide33

Fumigants

The fumigants are small, volatile, organic molecules that become gases at temperatures above 40

o

F. They are usually heavier than air and commonly contain one or more of the halogens (

Cl

, Br, or F). Most are highly penetrating, reaching through large masses of material. They are used to kill insects, insect eggs, nematodes, and certain microorganisms in buildings, warehouses, grain elevators, soils, and greenhouses and in packaged products such as dried fruits, beans, grain, and breakfast cereals.

Methyl bromide and others - ethylene dichloride, hydrogen cyanide, sulfuryl

fluoride (Vikane

®), Vapam®,

Telone®II, D-D®,

chlorothene, ethylene oxide, and the familiar home-use moth repellents

napthalene

crystals and

paradichlorobenzene

crystals. Developing countries have to stop MB by 2045 as per Montreal Protocol.

Phosphine

gas (PH

3

) has also replaced methyl bromide in a few applications.

Slide34

Malaria- Interventions

If we can control malaria, we will see an acceleration of Africa's development

If

malarious areas are free of the disease, family incomes will rise

If there is less malaria in homes, school attendance will increase - sometimes dramatically.

Tools needed to roll back this cause of suffering and poverty, to banish this obstacle to economic growth.

Insecticide treated nets in the home reduce transmission and prevent infection. Indoor spraying

with safe insecticides prevents infection. Treatment during pregnancy protects the mother's health and improves birth weight.

Rapid diagnosis and early treatment of someone with malaria shorten the illness and reduce death rates.

These interventions appear simple. Ensuring their success is not. To be effective they must reach all at risk.

Slide35

Lymphatic Filariasis

Debilitating parasitic disease

Caused by nematode worm

Wuchereria

bancroftiTransmitted by mosquitoes- Culex

and Anopheles spp.Consequences:

- disability(elephantiasis) - Social and cultural stigma

- Discomfort due to acute bacterial

adenolymphangitis

Slide36

Lymphatic Filariasis

Slide37

Yellow Fever

Acute communicable disease caused by arthropod – borne

flavirus

(B arbovirus)

Jaundice is prominent signDisease is distributed in two epidemiological patterns

Urban – man to man transmission by Aedes aegypti

Sylvatic – transmission b/w monkeys anf

from monkeys to man via Ae. africanus and Ae

. lutheocephalus

Slide38

Dengue Fever

Dengue fever is acute infection caused by

Arboviruses

transmitted by Aedes mosquitoesMay have similar epidemiological pattern with YF.

However, discovery of Ae. albopictus

in 1991 in Nigeria resulted in replacement of Ae. aegypti may have changed the epidemiological pattern

Slide39

Integrated Vector Management

IVM is a process of evidence-based decision making procedures aimed to plan, implement, monitor and evaluate targeted, cost-effective and sustainable combinations of regulatory and operational vector control measures.

IVM has a measurable impact on vector borne disease transmission risks. It adheres to the principle of subsidiary, inter-

sectoral

partnerships and adds on selective vector control, the attributes of environment friendly interventions, and sustainability.

Slide40

The concept of Integrated Vector Management

builds on selected vector control which was defined by WHO Expert Committee on Malaria as following:

the targeted use of different vector control methods alone or in combination to prevent or reduce human vector contact cost-effectively, while addressing sustainability issues (WHO, 1997).

Slide41

IVM Attributes

IVM has the following attributes:

- environmentally sound,

- inter-sectoral, - selective,

- targeted, - cost-effective and - sustainable.

IVM involves the utilization of a range of interventions including environmental management and the safe and judicious use of insecticides and biological control agents.

Slide42

TYPE

INTERVENTION

TARGETS

REQUIREMENTS

a) Environmental Management

Appropriate environmental changes and communal hygiene and sanitation *

Mosquitoes, black flies, snails, etc.

Appropriate tools and habitat management.

b) Biological Control

Larvivorous fishes, fungus & other microbes, nematodes etc

Mosquitoes

Black flies

Microbial larvicides, Local Fishes e.g. Tilapia, guppies etc

Predators parasites Competitors

Snails

Efficient predators and competitors

c) Chemical Control

Larviciding

Mosquitoes, Black flies, snail vector etc

Recommended and approved insecticides,

Neem

& other herbal insecticides, Insect Growth Regulators (IGR) and approved application equipments

Space/Outdoor spraying

Mosquitoes

Pyrethroids

, other recommended and approved insecticides, Personal Protective & approved and appropriate equipments

Indoor Residual Spraying

Vectors of malaria, lymphatic Filariasis, Leishmaniasis

Pyrethroids

, other approved insecticides

Insecticide-treated nets

Vectors of malaria, Leishmaniasis, lymphatic Filariasis, trypanosomiasis

Pyrethroids

& appropriate materials

Personal Protection

Mosquitoes, flies, fleas

Insecticide

coils

, mats,

repellents

,

natural

products

etc

d) Genetic Control

Sterile Insect Technology

Mosquitoes, Tsetse flies, black flies

Well-equipped laboratory (long term)

IVM Components

Slide43

Vector Control Services

This vector control unit will consist of a core group with entomological, epidemiological and environmental skills.

The role of the Vector Control Unit will be to provide the overall strategic and technical guidance to LGAs, for planning, implementation, monitoring and evaluation of vector control activities on the basis of information from epidemiological and environmental health services.

The State Ministries of Health will have to include vector control and environmental health skills.

On the basis of the orientation received from the vector control services, the State Team will prepare and implement integrated vector management plans with technical support and advice from the national level.