This morning’s email brought the news that the World Health Organization (WHO) approved the first vaccination for malaria. The vaccine, called Mosquirix, is not just a first for malaria — it is the first developed for any parasitic disease. Parasites are much more complex than viruses or bacteria, and the quest for a malaria vaccine has been underway for a hundred years. In this age of the covid-19 pandemic we are used to hearing vaccine efficacy of 95% plus. The malaria vaccine’s efficacy is only about 50% across all malaria pathogens, but that is a start. The vaccine targets plasmodium falciparum, the deadliest of five malaria pathogens and the most prevalent in Africa.
One of the insidious impacts of malaria is that it can infect the same person over and over. In many parts of sub-Saharan Africa, even those where most people sleep under insecticide-treated bed nets, children have on average six malaria episodes a year. The disease, even not fatal, takes a toll. The repeated infections can permanently alter the immune system, leaving people weak and vulnerable to other pathogens. Worldwide the WHO estimates that there are more than 200 million cases of malaria globally each year, the vast majority in Africa. Approximately 500,000 deaths are recorded annually, although public health officials believe deaths not recorded might be 4-5 times higher.
The CDC records approximately 2,000 cases of malaria each year in the United States, virtually all associated with visitors or returnees from foreign countries. Fortunately, malaria transmission in the United States was eliminated in the early 1950s through the use of insecticides, drainage ditches and the incredible power of window screens.
It’s hard to believe that there was a time when every state in America except Alaska was malaria endemic. There is a long history of malaria in the USA dating back to the 15th Century when it first appeared in the nation. But malaria is likely older than mankind as fossils of mosquitoes have been found in Africa that predate humanoid fossils. The first known case of the disease in America is believed to be after the arrival of explorer Christopher Columbus in 1492. Together with his crew, Columbus was infected with the disease during his voyage, although the malaria didn’t survive as the vector borne mosquitoes died off in the cold climate.
In 1607 the disease established itself and became epidemic in the Jamestown settlement as the colonies increased. European settlers and their West African slaves transmitted the disease to the Native Americans and it quickly spread to the Carolinas, Maryland, Georgia, Alabama and Florida. The disease then proceeded to spread west to Ohio, Missouri and the Gulf of Mexico. During this time, malaria was epidemic in much of Europe and the continual flow of workers arriving from England to America aided the spread of the disease.
Changes in living also contributed to the establishment of malaria in America as people settled in towns and villages. Inhabitants were living in closer quarters, sharing space with domesticated animals and travelling less thus passing the disease onto family and neighbors. The growing of rice in pools of stagnant, shallow water commenced in the Carolinas, creating an ideal habitat for mosquitoes. Poor sewage and drainage also produced an environment for the parasites to live in and breed.
Locally in the Washington DC metro area, the trendy neighborhood, Foggy Bottom, was not always so trendy. The fashionable Northwest neighborhood, now home to luxury condominiums, pristine river views and the affluent, was characterized by tenement dwellings, smoke stacks and slums 60 years ago – and was a hotbed of malaria.
It wasn’t until 1906 during the construction of the Panama Canal that the spread of malaria was recognized as a significant problem after 21,000 of the 26,000 workers were affected by the disease. During this time the Center for Disease Control (CDC) was established in an attempt to control malaria throughout America.
Around the same time, approximately 500,000 American soldiers deployed to malaria-endemic areas during World War II were infected with the disease. It is believed over 60,000 American soldiers died from the disease while fighting during the African and South Pacific campaigns. This ramped up the effect to prevent malaria from infiltrating further within the country. The military began to use the pesticide DDT to control both malaria and the bacterial disease, typhus.
People often ask me if I contracted malaria while I served in Kenya. Yes, a couple of times. Malaria is caused when an infected mosquito bites a person and then the malaria parasites start reproducing inside the person’s bloodstream. Symptoms usually take a week or two to appear but can be delayed for up to a month after the mosquito bite. Symptoms of malaria include fever and flu-like illness, including shaking chills, headache, muscle aches, and tiredness. I don’t recall “flu season” in Kenya, so the several times I felt like I had “the flu” off I went to the local pharmacy (whose owner received his doctorate from Oklahoma State), they took a blood sample, visually spotted the parasite under a microscope, and issued the prescribed medicine. In a day or two… or three, in my case, the symptoms were gone.
So congrats to the researchers for their breakthrough on malaria and the first vaccine against human parasites!