6 ms·

This is something that has confused me for a long time. America definitely has mosquitoes (I’m from Washington, DC). How are there mosquitoes but no malaria?

nicoburns 5y ago
It's only a few (4?) species of mosquito that carry malaria, out of hundreds of species in total.
pjscott 5y ago
It's bizarrely hard to find good explanations of this! The National Malaria Eradication Program, between 1947 and 1951, cut down on malaria transmission enough that the parasite was driven locally extinct. They drained wetlands where mosquitoes bred, sprayed house interiors and mosquito-heavy areas with DDT on a very large scale, and generally engineered a very specific ecological disaster, depriving the parasite of the human hosts needed for part of their reproductive lifecycle. Without enough infected humans, the parasites died out. Crucially, they didn't need to get rid of all the mosquitoes to do this: they just needed to drive mosquito-to-human transmission low enough for long enough. https://en.wikipedia.org/wiki/National_Malaria_Eradication_Program https://en.wikipedia.org/wiki/National_Malaria_Eradication_P...
- londons_explore 5y ago
  If this were the complete story then just a single person coming back to the USA infected would lead to mass infection... Clearly that hasn't happened.
  - Clewza313 5y ago
    Malaria does not spread from human to human, you need infected mosquitos in the mix. So you would need to get a breeding population of infected mosquitos biting humans for it to start spreading.
  - im3w1l 5y ago
    Only explanation I can think of is that the malaria from elsewhere is different somehow, worse adapted to US conditions.
  - Brybry 5y ago
    We do still have mosquito abatement programs too. I know here in Louisiana the local abatement program has trucks that spray synthetic pyrethroid chemicals (resmethrin, sumithrin and prallethrin) at night and uses an organophosphate (naled) from planes. And residents are routinely urged to be aware of and eliminate standing water on their property. We just don't use DDT anymore -- we almost wiped out our state bird with it. Edit: I have to wonder how much housing changes also mattered. With modern air conditioning and well sealed homes it's fairly rare to have mosquitoes in the home at night.
  - juskrey 5y ago
    The answer is malaria eradication efforts never stopped neither in US nor in Europe. It's just as routine as renewing asphalt roads or maintaining sewers
cbkeller 5y ago
The Anopheles mosquitos [1] which spread human malaria are present at some level across about half of the US, but are just not especially abundant here compared to other mosquitos that do not spread malaria. In fact, of the ~200 mosquito species which occur in the United States, only 12 are known spread any sort of human disease [2]. [1] https://en.wikipedia.org/wiki/Anopheles https://en.wikipedia.org/wiki/Anopheles [2] https://www.cdc.gov/mosquitoes/about/mosquitoes-in-the-us.html https://www.cdc.gov/mosquitoes/about/mosquitoes-in-the-us.ht...

nicoburns 5y ago

It's only a few (4?) species of mosquito that carry malaria, out of hundreds of species in total.

pjscott 5y ago

It's bizarrely hard to find good explanations of this! The National Malaria Eradication Program, between 1947 and 1951, cut down on malaria transmission enough that the parasite was driven locally extinct. They drained wetlands where mosquitoes bred, sprayed house interiors and mosquito-heavy areas with DDT on a very large scale, and generally engineered a very specific ecological disaster, depriving the parasite of the human hosts needed for part of their reproductive lifecycle. Without enough infected humans, the parasites died out. Crucially, they didn't need to get rid of all the mosquitoes to do this: they just needed to drive mosquito-to-human transmission low enough for long enough. https://en.wikipedia.org/wiki/National_Malaria_Eradication_Program https://en.wikipedia.org/wiki/National_Malaria_Eradication_P...

londons_explore 5y ago
If this were the complete story then just a single person coming back to the USA infected would lead to mass infection... Clearly that hasn't happened.
- Clewza313 5y ago
  Malaria does not spread from human to human, you need infected mosquitos in the mix. So you would need to get a breeding population of infected mosquitos biting humans for it to start spreading.
- im3w1l 5y ago
  Only explanation I can think of is that the malaria from elsewhere is different somehow, worse adapted to US conditions.
- Brybry 5y ago
  We do still have mosquito abatement programs too. I know here in Louisiana the local abatement program has trucks that spray synthetic pyrethroid chemicals (resmethrin, sumithrin and prallethrin) at night and uses an organophosphate (naled) from planes. And residents are routinely urged to be aware of and eliminate standing water on their property. We just don't use DDT anymore -- we almost wiped out our state bird with it. Edit: I have to wonder how much housing changes also mattered. With modern air conditioning and well sealed homes it's fairly rare to have mosquitoes in the home at night.
- juskrey 5y ago
  The answer is malaria eradication efforts never stopped neither in US nor in Europe. It's just as routine as renewing asphalt roads or maintaining sewers

cbkeller 5y ago

The Anopheles mosquitos [1] which spread human malaria are present at some level across about half of the US, but are just not especially abundant here compared to other mosquitos that do not spread malaria. In fact, of the ~200 mosquito species which occur in the United States, only 12 are known spread any sort of human disease [2]. [1] https://en.wikipedia.org/wiki/Anopheles https://en.wikipedia.org/wiki/Anopheles [2] https://www.cdc.gov/mosquitoes/about/mosquitoes-in-the-us.html https://www.cdc.gov/mosquitoes/about/mosquitoes-in-the-us.ht...