Thursday, July 30, 2015

A New Hope for Control and Eventual Eradication of Malaria

Past and Current Malaria Prevalence Around the World
Source: World Development Report (2009) via Virtual History

I quote from an article in The Guardian:
The world’s first malaria vaccine has been given the green light by European regulators.....The European Medicines Agency (EMA) recommended that RTS,S, or Mosquirix, should be licensed for use in young children in Africa who are at risk of the mosquito-borne disease. The shot has been developed by Britain’s biggest drugmaker GlaxoSmithKline (GSK) and part-funded by the Bill and Melinda Gates Foundation..... 
According to the WHO, 627,000 deaths from malaria were reported globally in 2013, of which the vast majority (562,000) occurred in Africa, mostly among children under the age of five (82%).
WHO estimates that there are 198 million cases of malaria a year now.

Apparently this is not an "ideal vaccine" requiring multiple shots over a period of years to protect a child fully. In Africa, getting a child its shots on a regular basis will be very difficult -- perhaps beyond the ability of public health officials to achieve high levels of immunity in the population. Still, if researchers have the knowledge to develop one vaccine, there is hope that they may develop other malaria vaccines that are better tailored for African needs.

The development of DDT and of a basis of scientific knowledge about malaria led to efforts to eradicate the disease in a number of developed countries. It is worth remembering that when the USA was founded as an independent nation, malaria occurred over its entire extent, and that malaria was a problem not only in southern Europe but in England and much of northern Europe. The World Health Organization created its Global Malaria Eradication Program in 1955, based on the then existing successes, but the successes could not be maintained, and in 1969 the Program was abandoned, to be replaced by a less ambitious WHO Malaria Control Program.

Basic Facts

Malaria is caused by any one of four Plasmodia species. It is transmitted from human to human by any of a variety of mosquito species. Thus a mosquito takes a blood meal from a person with malaria, rests for a while, and (after the agent has gone through a transformation in the mosquito, bites another person injecting the agent as it takes blood. If one can eliminate malaria from a human population, eliminate the mosquitoes capable of transmitting the disease, keep the mosquitoes from biting people, and/or cure the patient before he can transmit the infection, then these public health measures can stop a malaria outbreak or end endemic malaria in a region.

Historically a number of approaches have been used to fight malaria:
  • Drugs to treat the disease, beginning with Quinine and Chloroquine (1946).
  • Use of pesticides, beginning with DDT, to kill mosquitoes.
  • Reduction of mosquito breeding sites, by such things as making sure that there are no open bodies of water in which the mosquito eggs may be laid or the larva develop.
  • Other ways to keep larva from becoming mosquitoes, from spraying oil on the top of ponds, to use of larvacides, to stocking ponds with larva eating fish.
  • Use of window screens and bed nets (including insecticide containing bed nets) to keep mosquitoes from biting people.
Vaccine Development

Dr. Lee Howard, then the Director of the USAID Office of Health, recognized in the mid 1960s that the then current arsenal of means to combat malaria was not adequate for its eradication. True, the disease exists only in man, so if all human cases could be eliminated, the disease would be gone for good. However, getting a human population completely free of malaria was difficult, requiring many approaches to be used simultaneously. Moreover, at least one of the forms of the disease could lie hidden for years, only to reappear and restart a epidemic or become endemic. Moreover, the governments of many of the countries that had the worst malaria problems were weak, and the operation of a large scale public health campaign for a long period with no slip-ups was beyond their capacity. 

Dr. Howard thought that adding a vaccine to the armament of the malaria control workers would be a potential way to get to eradication or at least control. Unfortunately, no one had much of an idea as to how to create a vaccine to an organism as complex as a Plasmodium. Indeed, it was not known how to grow the organism in the laboratory -- a necessary step for all future work. Nonetheless, Dr. Howard convinced his colleagues at the National Institutes of Health to join with USAID and begin basic research toward the development of a vaccine against malaria. Now, half a century later, we finally have a first such practical vaccine. The search has yielded a great deal of fundamental knowledge about the parasite and the immune response, and further research and development can be expected to improve the vaccines against malaria.

So What

If a vaccine can make people immune to malaria (for a period of time) then the prevalence of the disease will be reduced. Indeed, even if the protection is only partial, the danger to a person contracting the disease may be reduced.

Combine the protection of a vaccine (and better protection from future improved vaccines) with improved knowledge of mosquitoes, and full use of the available control techniques (described above) should make control efforts more effective and eradication efforts more possible. The Gates Foundation believes we are now at a point in history when eradication is foreseeable. Certainly governments and public health agencies around the world are generally more capable of managing such efforts well.

The world public health community has eradicated smallpox and Guinea Worm Disease, and is on the verge (I hope) of eradicating polio. Lets hope malaria is next!

Read more....

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