How is DDT used to fight malaria?

February 20, 2015

Can we dispel common misapprehensions about fighting malaria?

In fighting malaria, DDT is not used outdoors.  Spraying swamps with insecticide does little to combat malaria because malaria-carrying mosquitoes don’t usually breed or rest there, and collateral damage from DDT reduces mosquito predators.

USAID-paid workers conducting Indoor Residual Spraying (IRS) campaign. (Where? When?) USAID photo, via Stanford University, Human Biology 153

USAID-paid workers conducting Indoor Residual Spraying (IRS) campaign. (Where? When?) USAID photo, via Stanford University, Human Biology 153

DDT’s utility in fighting malaria comes from its persistence when used close by humans bitten by those species of mosquito that carry malaria. Malaria is a parasitic disease.  Malaria parasites complete their life cycle in a human host (victim), and any insect taking blood from an infected human gets some of those parasites.  The parasite completes another phase of its life cycle in certain species of mosquito — not flies nor other biting insects — and after about two weeks, mosquitoes can infect humans with newly-ready parasites.

Those species that carry malaria are usually active from about dusk until after midnight.  Consequently, they bite people usually as they sleep.  Because the “blood meal” is heavy, newly-fed mosquitoes usually fly to a nearby wall of the home to excrete water from the meal, so they fly with a lighter load.  If DDT, or some other pesticide, coats that wall, the mosquito will die before being able to pass new parasites on to new victims.

DDT is NOT used to spray outdoors, to fight malaria.  Among other things, outdoor spraying threatens domestic animals and any creature that preys on the malaria-carrying mosquito; as a pragmatic matter, outdoor use affects only a tiny percentage of malaria-carrying mosquitoes. Malaria-carriers tend to breed in small, temporary pools of water from rain; this transience makes outdoor fighting difficult.  Many people fail to understand this crucial point: DDT outdoors doesn’t help in the fight against malaria.  (Other outdoor campaigns can provide relief, such as elimination of old tires, filling potholes in roads, draining raingutters, and generally eliminating the mosquito breeding areas close to human homes, since mosquitoes rarely move more than about 50 yards in their lifetime.)

It’s important to realize that DDT in IRS allows a mosquito a free first bite.  The hope is that bite is from an uninfected mosquito, who will then land on the treated wall of the home and get a fatal dose of pesticide, so that spreading malaria it may have picked up from its victim, is stopped.  Bednets, which form a physical barrier, prevent even the first bite.  Bednets gain effectiveness from treatment with impregnated insecticides.

The U.S. Centers for Disease Control, the lead agency in the campaign to eradicate malaria from the U.S. after World War II, explains this use of DDT in Indoor Residual Spraying, or IRS:

Indoor Residual Spraying

Many malaria vectors are considered “endophilic”; that is, the mosquito vectors rest inside houses after taking a blood meal. These mosquitoes are particularly susceptible to control through indoor residual spraying (IRS).

What Is Indoor Residual Spraying?

As its name implies, IRS involves coating the walls and other surfaces of a house with a residual insecticide. For several months, the insecticide will kill mosquitoes and other insects that come in contact with these surfaces. IRS does not directly prevent people from being bitten by mosquitoes. Rather, it usually kills mosquitoes after they have fed if they come to rest on the sprayed surface. IRS thus prevents transmission of infection to other persons. To be effective, IRS must be applied to a very high proportion of households in an area (usually >80%).

Health workers sparying insecticide on the walls of a wood and adobe dwelling.

Health worker spraying insecticide on the walls of a wood and adobe dwelling, in Indoor Residual Spraying (IRS). CDC image

History of IRS

IRS with DDT was the primary malaria control method used during the Global Malaria Eradication Campaign (1955-1969). The campaign did not achieve its stated objective but it did eliminate malaria from several areas and sharply reduced the burden of malaria disease in others.

Concern over the environmental impact of DDT led to the introduction of other, more expensive insecticides. As the eradication campaign wore on, the responsibility for maintaining it was shifted to endemic countries that were not able to shoulder the financial burden. The campaign collapsed and in many areas, malaria soon returned to pre-campaign levels.

As a result of the cost of IRS, the negative publicity due to the failure of the Malaria Eradication Campaign, and environmental concerns about residual insecticides, IRS programs were largely disbanded other than in a few countries with resources to continue them. However, the recent success of IRS in reducing malaria cases in South Africa by more than 80% has revived interest in this malaria prevention tool.

Rachel Carson understood this use of DDT, and she understood that outdoor use of DDT, such as crop spraying, or fighting insects affecting trees, could induce insects to evolve resistance and immunity to DDT.  In Silent Spring Carson warned that unless outdoor uses were greatly curtailed, DDT would be rendered ineffective to fight diseases.  Fred Soper, the super-mosquito killer from the Rockefeller Foundation who organized and led the UN’s malaria eradication effort, also understood the race against evolution of DDT resistance.  He had hoped resistance would not show up in tropical areas until the 1970s — malaria campaigns around the Mediterranean produced DDT resistance as early as 1948.  Sadly, resistance to DDT was already established in many mosquito populations in tropical Africa before Soper could take the UN’s program to them.  The UN had to abandon the campaign, as CDC’s explanation indicates.

Today, every mosquito on Earth carries some of the alleles of resistance to DDT, and many are immune to it.


National Infant Immunization Week, April 20-27, 2013

April 23, 2013

National Infant Immunization Week:  Find out about the power to protect with immunizations on http://www.vaccines.gov/

This week is National Infant Immunization Week designated by the U.S. Centers for Disease Control (CDC).  Vaccinations worked miracles in extending human lifespans, and in making childhood much safer from disease, for those children who get vaccinated.

Information following comes directly from the CDC:

Protect Your Baby with Immunization

Photo: A mother and childImmunization is one of the best ways parents can protect their infants from 14 serious childhood diseases before age two. Check to see if your baby is up to date on immunizations.

It is important for children to be fully immunized. Diseases that can be prevented with vaccines can be very serious – even deadly – especially for infants and young children. For example, children younger than 2 years old are at the highest risk for serious pneumococcal disease like pneumonia, blood infection (sepsis), and meningitis. Before the pneumococcal vaccine was used routinely, an estimated 17,000 cases of severe types of pneumococcal infection, like meningitis, occurred each year.

Immunization. Power to Protect.

Immunizations have helped to greatly improve the health of children in the United States. Most parents today have never seen first-hand the devastating consequences that vaccine-preventable diseases have on a family or community. While most of these diseases are not common in the United States, they persist around the world. It is important that we continue to protect our children with vaccines because outbreaks of vaccine-preventable diseases can and do occasionally occur in this country.

For example, in 2010, there were 27,550 people reported to have “whooping cough” (pertussis) in the United States. Twenty-seven deaths were reported – 25 of these were in children younger than 1 year old. In 2011, 222 people were reported to have measles in the United States – that’s more than any year since 1996. Measles is brought into the United States by unvaccinated U.S. residents and foreign visitors who get infected when they are in other countries. Measles is still common in many parts of the world, including Europe, Asia, the Pacific, and Africa. In fact, in France alone, more than 15,000 people were reported to have measles in 2011. Measles spreads easily, and it can be serious, causing hospitalization and even death. Young children are at highest risk for serious complications from measles.

Vaccinating your baby according to the recommended immunization schedule gives him or her the best protection against 14 serious childhood illnesses – like measles and whooping cough – before he is two years old. The recommended schedule is designed to protect infants and children early in life, when they are most vulnerable and before they are exposed to potentially life-threatening diseases.

Vaccine Information for ParentsVisit CDC’s vaccine website for parents.

The Diseases Vaccines Prevent

The recommended immunization schedule for babies includes vaccination protection against all of the following diseases:

Vaccinate On Time, Every Time

Even though the United States experiences outbreaks of some vaccine-preventable diseases, the spread of disease usually slows or stops because of immunization. If we stopped vaccinating, even the few cases we have in this country could very quickly become tens or hundreds of thousands of cases. Fortunately, most parents choose to vaccinate their children and immunization rates in this country are at or near record high levels. In fact, less than 1% of children do not receive any vaccines. However, some children have not received all of their vaccines and therefore are not fully immunized. It’s important that children receive all doses of the vaccines according to the recommended immunization schedule. Not receiving all doses of a vaccine leaves a child vulnerable to catching serious diseases.

That’s why it’s important to make sure that your child is up to date on his or her immunizations. Call your pediatrician to find out if your child is due for any vaccinations. Or, you can use this online tool to enter your child’s current record and quickly see if any doses have been skipped or missed. It is important to your child’s health to be up to date on immunizations.

Paying for Immunization

Photo: A babyMost health insurance plans cover the cost of vaccinations, but you should check with your insurance provider before going to the doctor. If you don’t have health insurance, or if your insurance does not cover vaccinations, the Vaccines for Children (VFC) program may be able to help with the cost.

The VFC program helps families of eligible children who might not otherwise have access to immunization. The program provides vaccinations at no cost. Children younger than 19 years of age are eligible for VFC vaccines if they are:

  • Medicaid-eligible
  • Uninsured
  • American Indian or Alaska Native,
  • Underinsured and vaccinated in Federally Qualified Health Centers or Rural Health Clinics.

Parents of uninsured or underinsured children who receive vaccines at no cost through the VFC Program should check with their health care providers about possible administration fees that might apply. These fees help providers cover the costs of giving the vaccines, including storing the vaccines and paying staff members to give vaccines to patients. However, VFC vaccines cannot be denied to an eligible child if a family can’t afford the fee.

Have Questions about Immunization?

  • Talk with your child’s health care professional, contact your local or state health department, or call the CDC at 800-CDC-INFO (800-232-4636).
  • Visit CDC’s vaccine website for parents

More Information

CDC works 24/7 saving lives and protecting people from health threats to have a more secure nation. A US federal agency, CDC helps make the healthy choice the easy choice by putting science and prevention into action. CDC works to help people live longer, healthier and more productive lives.

Last syndicated: April 19, 2013
This content is brought to you by: Centers for Disease Control and Prevention (CDC)

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V for Vaccine: A slightly rude film with a powerful point

January 10, 2013

A couple of kids in the Dallas area have died already from influenza — neither had been vaccinated against it.  Deaths have occurred across the nation, frequently in young, otherwise healthy people.

Nasty flu bugs going around this year, and the every-year epidemic has hit about two months early.  One part of the good news is that the vaccines this year are especially well-suited to target the viruses that cause the trouble.  The vaccines work well every year, but especially well in 2012 and 2013.

The bad news is that millions of people haven’t bothered to get vaccinated. That’s not good.

  1. Under Obamacare, there’s no copay for insurance for a flu shot.  It’s “free” if you have any kind of insurance. In addition, county health offices offer the vaccines for free to any comers.  A couple of weeks ago at the pharmacy I stood behind a woman who confessed she’d not gotten a flu shot (pharmacies are pushing vaccinations these days, to promote their mini-clinics).  “I’ve got that crappy teachers’ insurance,” she told the technician.  “It never pays for anything like that.”  The tech looked it up, and told her that her copay was zero, and her insurance paid for it — essentially a free shot, to her.  On the way into the clinic she said, “I’ve never gotten a flu shot before.”  Oy.
  2. Think Herd Immunity:  Are you usually healthy?  Great.  But if you’re pregnant, or you work around people who are or may be pregnant, or if you’re over 60, or if you have any chronic condition like diabetes, high blood pressure, chronic sinusitis, or a raft of other things, you’re at risk, and you put others in those risk categories at risk.  My grandfather worked at a hospital while my mother and my oldest brother were living with him; after a week of my grandfather’s working in the polio ward, my brother came down with the disease.  Of course we don’t know for sure, but my grandfather kicked himself for 40 years, until his death, because he thought he’d brought home the disease my brother caught.  With vaccines, those incidents become much more rare.

Risking this blog’s G rating, I’m going to post this film, “V for Vaccine.”  Found it at New Anthropocene.  Turn up your offense filter, or ignore the language — but pay attention to what this guy says, PowerM1985:

Is it worth getting your children vaccinated if it risked them becoming autistic? In this video I give a short demonstration of why I personally believe that even if there was a risk of my child becoming autistic (AND THERE IS NOT!) I would still get them vaccinated.

You should probably know that the work of the Centers for Disease Control to correctly predict which strains of the viruses will be most prevalent, and get vaccines that will fight those viruses, has been very, very good this year.

  • Influenza A (H3N2), 2009 influenza A (H1N1), and influenza B viruses have all been identified in the U.S. this season. During the week of December 23-29, 2,346 of the 2,961 influenza positive tests reported to CDC were influenza A and 615 were influenza B viruses. Of the 1,234 influenza A viruses that were subtyped, 98% were H3 viruses and 2% were 2009 H1N1 viruses.
  • Since October 1, 2012, CDC has antigenically characterized 413 influenza viruses, including 17 2009 influenza A (H1N1) viruses, 281 influenza A (H3N2) viruses and 115 influenza B viruses.
    • All 17 of the 2009 influenza A (H1N1) viruses were characterized as A/California/7/2009-like. This is the influenza A (H1N1) component of the Northern Hemisphere vaccine for the 2012-2013 season.
    • Of the 281 influenza A (H3N2) viruses, 279 (99%) were characterized as A/Victoria/361/2011-like. This is the influenza A (H3N2) component of the Northern Hemisphere influenza vaccine for the 2012-2013 season.
    • Approximately 69% of the 115 influenza B viruses belonged to the B/Yamagata lineage of viruses, and were characterized as B/Wisconsin/1/2010-like, the influenza B component for the 2012-2013 Northern Hemisphere influenza vaccine. The remaining 31% of the tested influenza B viruses belonged to the B/Victoria lineage of viruses.

What are you waiting for?  Go get a flu shot!

More:

English: This is CDC Clinic Chief Nurse Lee An...

This is CDC Clinic Chief Nurse Lee Ann Jean-Louis extracting Influenza Virus Vaccine, Fluzone® from a 5 ml. vial. (Photo credit: Wikipedia)

Graphic on influenza, 2013 - Flu.gov

Information from Flu.gov; click image to get to active Flu Vaccine Finder


Swine flu shuts down prisons: Let the prisoners out?

May 3, 2009

This headline from the Sacramento Bee sure caught my eye:

Swine flu case shuts down visits at all 33 state prisons

Of course, I read it too fast, and skipped over the word “visits.”  I had to click on the story to see whether they were going to tell the prisoners to stay at home for a week, like the Fort Worth, Texas, school district did.   I suppose, after a fashion, that was exactly the message.

At the Officer of the Receiver for California Prison Health Care Services, spokesman Luis Patino said Sunday that an inmate in Centinela State Prison in Imperial County was diagnosed as probable for the H1N1 virus, or swine flu.

“The inmate and his cellmate have been isolated, Patino said. “They remain at the prison.”

Whew!

Ticket sales for movies are way up in those areas where the schools are shut down — good news for the opening weekend of X-Men Origins:  Wolverine.

Maybe we’d be better off if the kids remained in school, as well as keeping the convicts in the prisons.

Is the panic over swine flu too much? If we go back to the week ending March 21, 2009, we find that there were already more than 22,000 cases of influenza in the U.S., with 35 pediatric deaths.  Has the swine flu added to either the rates of infection or the rates of death?  If the dramatic steps, the event cancellations and school closings, are appropriate for the swine flu, shouldn’t they have been appropriate for the other flu viruses, too?

Do we really need to close schools?  What do you think — tell us in comments.

See the CDC’s report on swine flu at their site:    H1N1 (Swine Flu)

Other resources:


War on Science: CDC publishes suppressed study

March 15, 2008

On the eve of a major conference on health effects of DDT, the U.S. Centers for Disease Control published a study it had suppressed for several months, detailing pollution effects in the Great Lakes area. The author of the study, demoted but still outspoken, was grudgingly granted permission to attend the Kenaga International Conference on DDT and Health, which opened yesterday at Alma College in Alma, Michigan.

Alma Conference logo

Science won the skirmish, getting the study pried out of CDC. News coverage of the conference stopped short of spectacular so far: Only local Michigan media outlets provided coverage. If we won the war, but no one knew . . . ?

The Morning Sun suggested that further studies of health effects in the area are required, and that no successful cleanup of a toxic site is ever done without health studies showing the need.

[Jane] Keon[, chairwoman of the Pine River Superfund Citizen Task Force] hasn’t read the entire report but did read the portions about Gratiot County.

“There’s no new information, and everything mentioned is well-known and verified by ATSDR and CDC,” she said. “I understand that in addition to 200 researchers and much peer review the report data was reviewed by state and local health departments in the areas of concern without the complaint that the science was weak.

“We in the task force view the report as further proof that a full-blown health study is needed in Gratiot County. From our own studies we also know that communities with contaminated sites that have a health study to point to get very thorough cleanups, while communities that do not have a health study do not get thorough cleanups.”

The task force has twice applied for grants to perform a comprehensive local heath study but were turned down both times.

“The reasons offered (for rejection) seemed lame and illogical,” Keon said. “One time we were told that we didn’t have enough data, and yet that is why we desired the health study – to have a scientific collection of data.”

A citizens’ group in Washington, D.C., the Center for Public Integrity, obtained a copy of the study last year and made it available on the internet. There is no indication I can find of whether there were changes made in the study between the leaking and the formal publication.


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