Malaria returns to the United States

GUEST COLUMN, John Richard Schrock, Library Frontlines

The U.S. detects and treats about 2,000 malaria cases each year. For the last decades, they have only been in travelers, usually from southern Asia and Sub-Saharan Africa. But five recent cases in Maryland, Florida and Texas have no connection to international travel. While it is possible that an infected mosquito arrived via an international airliner (airport transmitted malaria) and escaped, malaria-infected mosquitoes have now been found in Florida. This disease agent has now returned. 

Malaria was also a U.S. disease long ago. It became less common as Americans developed housing with secure windows, eliminated standing water, and many moved to drier urban environments.

In 2020, there were an estimated 241 million cases worldwide, with Africa home to over 95 percent. This is now mainly a tropical disease. Malaria causes fever, headache and chills one to two weeks after being bit by infected female Anopheles mosquitoes. Only female mosquitoes bite us because they need blood protein to produce eggs. The malaria agent is not a bacterium or virus, but a one-celled protist in the genus Plasmodium. Five species are known to be spread by mosquitoes to humans. Only two pose a major threat. Plasmodium falciparum is deadliest and most common in sub-Saharan Africa. Plasmodium vivax is the most dominant elsewhere. According to the CDC, malaria “caused 627,000 deaths in 2020, with 96 percent in Africa. And 80 percent of those deaths were in children under five years old.”

Malaria poses an unusual problem because it has different stages and can evade standard treatments. Surgeon-Major Ronald Ross (1857–1932) of the British Indian Medical Service conducted experiments on birds infected with a malaria parasite and discovered sporozoites in the salivary glands of mosquitoes that had fed on malarious birds. Ross received the Nobel Prize in 1902 for discovering the mosquito stages of malaria.

The malaria agent transforms into different stages: 1) sporozoites injected by the mosquito travel in the blood to the liver, 2) then released by the liver as merozoites and travel to the heart and lungs, 3) then return to invade the red blood cells, and 4) some then develop into gametocytes and circulate in the blood stream until withdrawn by a mosquito. When they cross the mosquito gut wall, they then form oocysts that produce thousands of sporozoites, and the cycle repeats when the mosquito bites another victim. 

There are many genera of mosquitoes including Culex and Aedes, but only Anopheles can transmit malaria. Maintaining research on the many insects that are yet to be described in the world is critical.

The research complexity is explained in “The Malaria Capers” published in 1991 by the late Robert S. Desowitz (1926–2008). He notes how fake promises of biotechnology have led Third World health officials to expect a quick fix-the malaria vaccine “just around the corner” but explains the failure of science. Since October 2021, a RTS,S/AS01 malaria vaccine has finally been found to be about 30% efficient in providing protection, but poses cost barriers as well. 

However, in June of 2021, the World Health Organization awarded China malaria-free certification. This only comes after three prior years of no internal transmission of malaria cases and an exhaustive investigation to confirm the results of 70 years of efforts to rid China of this major tropical disease. Southern China is subtropical, and suffered 30 million cases over 70 years ago. 

How did China go from 30 million to zero today? Similar to their response to the recent COVID-19 pandemic, the southern population followed a wide array of standard anti-malarial behaviors, using insecticide-treated nets for protection while sleeping, draining water sources necessary for mosquito breeding, and improving housing. In addition, the first Nobel Prize to a Chinese researcher working in China went to Tu Youyou in 2015. In the 1970s, Tu modified an ancient medicinal plant to develop artemisinin. Today, artemisinin-based combination therapies (ACTs) are the most effective antimalarial drugs available and are today being used widely in Africa.

Because I often traveled in a southern China in 1994-2017 that had malaria, I could not donate blood. With malaria in China totally eradicated since 2017, I can now donate blood in the U.S. However, if malaria continues to spread in the U.S., that could now become a whole new issue for non-traveling Americans.

Sources: 

Center for Disease Control and Prevention, “Elimination of Malaria in the United States (1947–1951)” at: https://www.cdc.gov/malaria/about/history/elimination_us.html

NIH: National Library of Medicine; “A Brief History of Malaria” at: https://www.ncbi.nlm.nih.gov/books/NBK215638/

UNESCO, “From 30 million cases to zero: China is certified malaria-free by WHO”; 30 June 2021 at: https://www.who.int/news/item/30-06-2021-from-30-million-cases-to-zero-china-is-certified-malaria-free-by-who