The article ‘Diagnosis and management of dengue’ gives a
comprehensive review of dengue, detailing cause, transmission, clinical
features, treatment and prevention (1). With respect to prevention, the
authors discuss about vaccine development, community involvement strategy,
vector control using chemicals, biologicals and traps. According to the
authors, the strategy to control vector population is centred mainly on
the use of chemicals, a counterproductive measure. Therefore, efforts
should focus on community involvement to control Aedes aegypti, the
principal vector, which breeds in discarded containers (that collect
rainwater) and in other water storage containers.
When DDT had been widely in use about 41 years ago (2) Aedes aegypti
had almost disappeared from many countries. With diminished use of DDT,
the menace of DHF has now returned (2). The problem has become more
pronounced with urban expansion, increased use of non-biodegradable
products (that can hold rain water and allow mosquitoes to lay eggs), lack
of water supply via pipes (this makes water storage in containers and
tanks a necessity) among other factors (2).
A community involved environmental management for dengue prevention
study carried out in Guantanamo, Cuba showed Aedes infestation reduction
by 50-75% (3). However, as the authors suggest (1), this study did not
investigate the effect of the intervention on dengue virus transmission
(1). Notwithstanding this, persistent reduction in vector infestation is
bound to reduce dengue virus transmission.
Cans, plastic bottles, tires, car batteries (4) and flower containers
in cemeteries have been found to be good breeding places. Latex collection
cups, in rubber growing countries, cocoa pods, coconut shells, tree holes,
plant stumps, mud pots, flower pots, grinding stones, water tanks etc are
good breeding ground for mosquitoes (5). Care needs to be taken to turn
latex collection cups upside down during rainy season to prevent vector
breeding. Use of flower holding vases with drain holes or bronze vases, in
cemeteries, has been suggested to limit mosquito spread (6).
Community participation programme focusing on eradicating or reducing
breeding containers at homes, weekly emptying of storage containers
(weekly emptying can disrupt mosquito life cycles, since newly hatched
larvae require 9 days under favorable conditions to develop into the adult
stage or complete the cycle), encouraging larval control by using
larvicide (temephos or Abate 1% sand granules), introducing larvivorous
fish into water containers, covering larger containers with lids to
prevent egg laying by mosquitoes and encouraging the use of predacious
copephods of the genus Mesocyclops as a biological control agent will help
stop the spread of dengue and DHF (7,8). A novel insecticide delivery
instrument named the Mossie-Buster has been developed to control mosquito
larvae from urban breeding places in Townsville, Australia (9).
References
1. Teixeira GM, Barreto ML. Diagnosis and management of dengue. BMJ
2009;339:b4338
2. Vu SN, Nguyen TY, Kay BH, Marten GG, Reid JW. Eradication of Aedes
aegypti from a village in Vietnam, using copepods and community
participation. Am J Trop Med Hyg. 1998; 59:657-60.
3. Vanlerberghe V, Toledo ME, Rodríguez M, Gomez D, Baly A, Benitez
33 JR, et al. Community involvement in dengue vector control: cluster
randomised. BMJ 2009;338:1959b.
4. Mazine CA, Macoris ML, Andrighetti MT, Yasumaro S, Silva ME,
Nelson MJ, Winch PJ. Disposable containers as larval habitats for Aedes
aegypti in a city with regular refuse collection: a study in Marilia, Sao
Paulo State, Brazil. Acta Trop. 1996; 62:1-13.
5 Thenmozhi V, Hiriyan JG, Tewari SC, Philip Samuel P, Paramasivan R,
Rajendran R, Mani TR, Tyagi BK. Natural vertical transmission of dengue
virus in Aedes albopictus (Diptera: Culicidae) in Kerala, a southern
Indian state. Jpn J Infect Dis. 2007;60:245-9.
6. O'Meara GF, Gettman AD, Evans LF Jr, Scheel FD. Invasion of
cemeteries in Florida by Aedes albopictus. J Am Mosq Control Assoc. 1992
;8:1-10.
7. Effectiveness of dengue control practices in household water
containers in Northeast Thailand.Trop Med Int Health. 2005;10:755-63.
8. Vu SN, Nguyen TY, Tran VP, Truong UN, Le QM, Le VL, Le TN, Bektas
A, Briscombe A, Aaskov JG, Ryan PA, Kay BH. Elimination of dengue by
community programs using Mesocyclops(Copepoda) against Aedes aegypti in
central Vietnam. Am J Trop Med Hyg. 2005;72:67-73.
9. Canyon DV, Hii JL. The Mossie-Buster: a hose-driven insecticide
delivery tool for the control of container-breeding mosquitoes. J Am Mosq
Control Assoc. 1997 ;13:389-94.
Competing interests:
None declared