Ppt for MBBS students on 'Prevention of Dengue'

1. Prevention of Dengue
Dept. of Community Medicine, MMC
Dr. Mamta T.G. (Asst. Prof.)

2. A mosquito can sense a human from what
distance???

3. Prevention of Dengue

4. Aedes- The Tiger Mosquito

5. →Name- Aedes
→Full name- A. aegypti,
A. albopictus
→Found in- Asia, America, Africa
→Breeds in- Artificial containers
→Bites at- Daytime
→Flight range- Around 100m
→Fevers caused namely-
• Dengue
• Chikungunya
• Zika
• Rift Valley
• Yellow
AEDES

6. Prevent Dengue..?!!- But How??
Aedes Bites HumanAedes Breeds in
Artificial water
collection
Human develops DengueAdult Aedes Mosquito
1 2 3 4

7. Mosquito Control Measures
Anti-larval
Environmental
Chemical
Biological
Anti-adult
Residual
Sprays
Space
Sprays
Genetic
Control
Protection Against
Mosquito Bites
Screens
Repellents
Mosquito
Nets
1 2 3

8. Integrated Vector Management
Avoid excessive use of any one method
Combine one or more methods
Prevent environmental pollution
Avoid development of Insecticide resistance

9. A) Environmental
B) Chemical
C) Biological
ANTI LARVAL
MEASURES
1

10. Aedes Breeding Sites

14. Eliminate breeding places of mosquitoes = “Source Reduction”
1. Eliminating the breeding source – by filling/ levelling/ drainage
2. Make the source unsuitable for breeding e.g. change salinity
A) Environmental

15. *Get rid of water holding containers- Artificial collection of water *

16. COMMONLY USED
LARVICIDES
i) MINERAL OILS
ii) PARIS GREEN
iii) SYNTHETIC
INSECTICIDES
B) Chemical Control

17. i) MINERAL OILS
•Application of oil to water - one of the
OLDEST KNOWN MOSQUITO CONTROL MEASURES
• Mechanism of action:
1. The oil cuts off air supply to the larvae and pupae
2. Specific toxic action on the larvae and pupae
• Application: Once a week
• Amount: 40 – 90 litres / hectare

18. • Disadvantages:
1. Water becomes unfit for drinking
2. Kills fish
• Widely used oils:
1. Diesel
2. Fuel
3. Kerosene
4. Special mosquito larvicidal oil

19. ii) PARIS GREEN
•Also called copper acetoarsenite
•Insoluble emerald green microcrystalline powder
Mechanism of action:
•Stomach poison- must be ingested by larvae
•Bottom feeders also killed when used as special
granular formulation

20. Application:
•As 2% dust – 2kg Paris green + 98 kg diluent
•Hand / rotary blowers used
Amount:
•1 kg (actual Paris green) / hectare of water
* In dosage normally used, not harmful to fish, domestic animals or man

21. iii) SYNTHETIC INSECTICIDES
Organ phosphorous compounds:
Compound Dosage (g /ha)
Abate 56 - 112
Malathion 224 - 627
Fenthion 22 - 112
Chloropyrifos 11 - 16
Abate - least toxic ( conc. of 1ppm)

22. Organochlorine compounds:
• DDT, HCH
Not recommended now due to-
1. Long residual effect
2. Water contamination
3. Increased risk of resistance development in vector
mosquitoes
DDT
Bacillus thuringensis var. israelensis (B.t.i.)- a naturally produced
bacterial toxin

23. •Gambusia affinis
•Lebister reticulatus
(Barbados millions)
C) Biological Control Measures

24. A) Residual sprays
B) Space sprays
C) Genetic control
ANTI ADULT
MEASURES
2

25. S.No Toxicant Dosage (g/m2) Effectiveness
(months)
1 DDT * 1 - 2 6 - 12
2 Lindane 0.5 3
3 Malathion 2 3
4 OMS - 33 2 3
A) Residual Sprays

26. Limitations of insecticides-
•Development of resistance
*It is important to conduct periodic tests to determine susceptibility of
different mosquito vectors to the various commonly used insecticides
INSECTICIDE OF CHOICE- DDT

27. Residual surface spray
Residual wall / indoor spray

28. • Space sprays- Insecticide is sprayed into the atmosphere as a mist / fog to kill
insects.
• Types-
1. Pyrethrum extract :
• Active principle- Pyrethrin
• Action- Nerve poison
• Amount- 1oz (0.1% Pyrethrin) / 1000 cu.feet.
Close doors & windows for ½ hour after spraying
B) Space Sprays

29. 2. Malathion and Fenitrothion:
• Extensively used
• Ultra low volume (ULV)
space spraying method
• Limitations-
• Reduction in number of mosquitoes is temporary
• Re-infestation occurs within a short while

30. • Methods explored-
1. Sterile male technique
2. Cytoplasmic incompatibility
3. Chromosomal translocations
4. Sex distortion
5. Gene replacement
…....still in “Research phase”
C) Genetic Control

31. • Advantages-
1.Cheaper
2.Potentially more efficient
3.Not subject to vector resistance

32. A) Mosquito nets
B) Screens
C) Repellents
“Protection”
against bites
3

33. • Net hole dimensions - 0.045 in
• No. of holes / sq. inch - 150
• Offers protection during sleep
• Material – white in color
• Treated with insecticides
A) Mosquito Nets

34. • Screens made of copper or bronze
are installed in buildings
• Aperture- 16 meshes/ sq. inch
• Advantage- Gives excellent protection
• Disadvantage- Expensive
B) Screening

35. C) Repellents

36. International Health Regulation
• Airport/ Seaport- Free of mosquitoes and breeding sites for 400m
Aedes Aegypti Index (%) = No. of houses with Aedes breeding
Total no. of Houses examined in the area
Kept zero at all ports