July 28, 2013 9:54 AM
Bill Brieger
Recently we have seen some online discussion about
mosquitoes biting 24/7, and while this is true, it is not all species of
mosquitoes that bite all the time - only that anytime during the day/night one
might be bitten, but by different types of mosquitoes, carrying different
diseases at different times. Below is a chart that tries to draw some of the
distinctions among the different types of mosquitoes. It is not all inclusive. Some references are
listed at the end. Finally there is an abstract about possible changes in
malaria mosquito biting behaviors, although we should use caution in that this
has not been verified universally.
mosquito-types-sm.jpg
Reference Links
How Mosquitoes Work.
http://science.howstuffworks.com/zoology/insects-arachnids/mosquito1.htm
Be vigilant to different mosquito breeding grounds.
http://www.fehd.gov.hk/english/safefood/images/Pestnews_9e.pdf
Biological Notes on Mosquitoes.
http://www.mosquitoes.org/LifeCycle.html
Mosquito. From Wikipedia, the free encyclopedia.
http://en.wikipedia.org/wiki/Mosquito
Anopheles Mosquitoes.
http://www.cdc.gov/malaria/about/biology/mosquitoes/
Differentiate Culex, Anopheles and Aedes Mosquitoes.
http://profwaqarhussain.blogspot.com/2012/10/differentiate-culexanopheles-and-aedes.html
Flight performance of the malaria vectors Anopheles gambiae
and Anopheles atroparvus. http://www.ncbi.nlm.nih.gov/pubmed/15266751
Effects of changing mosquito host searching behaviour on the
cost effectiveness of a mass distribution of long-lasting, insecticidal nets: a
modelling study. Malaria Journal 2013, 12:215 doi:10.1186/1475-2875-12-215.
Olivier JT Briët (oliv...@unibas.ch). Nakul Chitnis (naku...@unibas.ch)
Abstract: Background The effectiveness of long-lasting,
insecticidal nets (LLINs) in preventing malaria is threatened by the changing
biting behaviour of mosquitoes, from nocturnal and endophagic to crepuscular
and exophagic, and by their increasing resistance to insecticides. \
Methods: Using epidemiological stochastic simulation models,
we studied the impact of a mass LLIN distribution on Plasmodium falciparum
malaria. Specifically, we looked at impact in terms of episodes prevented
during the effective life of the batch and in terms of net health benefits
(NHB) expressed in disability adjusted life years (DALYs) averted, depending on
biting behaviour, resistance (as measured in experimental hut studies), and on
pre-intervention transmission levels.
Results: Results were very sensitive to assumptions about
the probabilistic nature of host searching behaviour. With a shift towards
crepuscular biting, under the assumption that individual mosquitoes repeat
their behaviour each gonotrophic cycle, LLIN effectiveness was far less than
when individual mosquitoes were assumed to vary their behaviour between
gonotrophic cycles. LLIN effectiveness was equally sensitive to variations in
host-searching behaviour (if repeated) and to variations in resistance. LLIN
effectiveness was most sensitive to preintervention transmission level, with
LLINs being least effective at both very low and very
high transmission levels, and most effective at around four
infectious bites per adult per year. A single LLIN distribution round remained
cost effective, except in transmission settings with a pre-intervention
inoculation rate of over 128 bites per year and with resistant mosquitoes that
displayed a high proportion (over 40%) of determined crepuscular host
searching, where some model variants showed negative NHB.
Conclusions: Shifts towards crepuscular host searching
behaviour can be as important in reducing LLIN effectiveness and cost
effectiveness as resistance to pyrethroids. As resistance to insecticides is
likely to slow down the development of behavioural resistance and vice versa,
the two types of resistance are unlikely to occur within the same mosquito
population. LLINs are likely cost effective interventions against malaria, even
in areas with strong resistance to pyrethroids or where a large proportion of
host-mosquito contact occurs during times when LLIN users are not under their
nets.
——–
Finally please note that one malaria intervention alone will
not solve our problems so we need to apply a mix that includes Nets, Indoor
Residual Spraying, Diagnosis with mRDTs, Appropriate treatment with
Artemisinin-based Combination Therapy, Intermittent Preventive Treatment, one
day a vaccine and others …
View article...
Malaria update is a service of Jhpiego's Senior Malaria
Adviser. You can also follow Malaria updates on
https://twitter.com/#!/bbbrieger and http://malariamatters.org/
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