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Vol. LXIII, No. 17
August 19, 2011

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U.S. Not Spared
Worm Infections Plague World’s Poorest Populations

On the front page...

Dr. Peter Hotez speaks at Natcher on July 28.
Dr. Peter Hotez speaks at Natcher on July 28.
In front of a standing-room-only audience in Natcher Bldg. on July 28, Dr. Peter Hotez admitted that he planned to go outside his comfort zone. While he frequently addresses groups on neglected tropical diseases (NTDs) in the world’s low- and middle- income countries, he has not spoken extensively about similar neglected infections of poverty in the United States.

The World’s Neglected Tropical Diseases

The NTDs are chronic parasitic and related infections that plague the world’s poorest populations. The 17 members of the class, many of which are associated with parasites (usually worms), are not in themselves killers but instead make life so miserable that the human cost is calculated in DALYs—disability-adjusted life years. And there are many millions of them.

Unlike AIDS and malaria, which can kill and which draw much public attention and funding, the NTDs get comparatively little attention, Hotez argues. They also lack robust research funding.


Hotez, who is president of the Sabin Vaccine Institute and a world authority on tropical diseases who was recently recruited to Baylor College of Medicine from George Washington University, said NTDs were first identified as a category only 6 or 7 years ago. “They are the most prevalent infections of poor people,” he noted.

The most widespread infection is ascariasis, or roundworm, which afflicts an estimated 807 million people globally; trichuriasis (whipworm) places second with 604 million people infected, followed by hookworm, with 576 million victims.

The infections tend to cluster in low- and middle-income nations such as those of sub-Saharan Africa, where many people are “polyparasitized,” hosting multiple infections, Hotez said. NTDs account for the loss of some 56.6 million DALYs annually, he reported.

“These diseases are actually a cause of poverty,” Hotez explained; victims are often unable to work because of their illness. “Farmers are too sick to work in the field.” Further, hookworm alone has been shown to lower IQ, in addition to harming physical development.

“A cancer cell [is], like Grendel, a distorted version of our own selves,” said author Mukherjee.

Hotez said, “I get very frustrated when I see the press focusing on diseases that disproportionately affect wealthy people living in the suburbs.” photos: ernie branson."

Photos: Ernie Branson

“These are some of the stealth reasons why the so-called ‘Bottom Billion’ can’t escape poverty,” he said.

Hotez, who is editor-in-chief of the scientific journal PLoS Neglected Tropical Diseases, said NTDs “are the opposite of emerging infections”— they have been around for millennia. “They are the most common infections in developing countries.”

But their longevity in the human population has not earned the attention of the pharmaceutical industry, Hotez said; his institute is stepping into the gap with the goal of providing “the right of access to innovation.” The Sabin institute has in the pipeline vaccines for human hookworm infection, schistosomiasis and Chagas disease.

The institute has its manufacturing arm in Brazil, which itself has high rates of NTDs. “Brazil is known as an innovative developing country, or IDC,” Hotez explained. “There is lots of talent and innovation, but also a lot of poverty.”

Because hookworm is almost always found in tandem with schistosomiasis, Hotez and his colleagues hope to create a “multivalent, anthelminthic antipoverty vaccine.”

He then made note of interesting trends that he worried were more about generating than testing hypotheses.

Hotez has observed that NTDs appear to be the legacy of the so-called “Middle Passage,” or mid-Atlantic slave trade. “Brazil is ground zero for NTDs that are endemic to Africa’s west coast,” he said. “You show me extreme poverty and I’ll show you NTDs.”

Neglected Infections of Poverty in the U.S.

Hotez said his recent analysis shows that pockets of parasitic diseases exist in poor parts of the U.S., which currently has an estimated 44 million people living in poverty, including 16 million in “abject poverty,” or subsisting on less than $50 per week for food.

“The U.S. has the world’s highest relative poverty rate for a developed country,” he reported. He cited a 2005 research paper from Chris Murray and his colleagues showing that the U.S. is actually a mosaic of 8 countries, including 4 socio-economically disadvantaged ones: Appalachia/ Mississippi Valley, the Indian reservations of the American West, poor black communities of the rural South (Cotton Belt) and poor black high-risk urban neighborhoods.

Other researchers add the Mexico borderlands and the post-Katrina Gulf to this list and think only a Marshall Plan-type effort could reverse the problems.

Many NTDs are not considered reportable diseases by the Centers for Disease Control and Prevention and there is no active surveillance of their prevalence, Hotez said. There are, nonetheless, seven diseases that are “incredibly common in African Americans and Hispanics.” They are known as “3 Cs and 3 Ts,” to which Hotez adds a seventh—dengue fever. They include:

  • Chagas disease, which has “globalized” in recent years. There are an estimated 300,000 cases in the U.S. It can cause sudden cardiac death and is spread by triatomines, or “kissing bugs,” which have a broad range in the U.S. The Carlos Slim Institute of Health is financing a recombinant Chagas disease vaccine known as Cruzmexvax. There is only one center in the U.S. (in Los Angeles) where patients can receive drugs to treat Chagas disease, Hotez said.
  • Congenital cytomegalovirus infection, which when transmitted from mother to child can result in hearing loss and severe intellectual deficits. l Cysticercosis, which is transmitted by worms and has been shown to cause epilepsy in Hispanic Americans.
  • Toxocariasis is caused by worms from the feces of dogs and cats. It affects the eyes and viscera, also the lung, where it causes a Loeffler’s pneumonitis that resembles asthma. It is also thought to harm the brain and result in developmental delays. The highest rates of toxocariasis are found in the South, affecting some 3 million African Americans. Hotez asked, “Shouldn’t we be doing more active studies working to link toxocariasis and asthma and developmental delays?”
  • Toxoplasmosis, a parasitic disease transmitted mainly by cats.
  • Trichomoniasis, a sexually transmitted disease affecting some 880,000 African-American women, with high rates found in Louisiana.
  • Dengue fever, too, has emerged in the U.S. in types 1 and 2 and is transmitted by mosquito. Hotez worries about what will happen when the two types genetically combine.

The most urgent public health needs are assessing the NTD burden in the U.S. and determining the extent of transmission and ecology of the 3 Cs and 3 Ts, Hotez said.

“We also have a huge R&D agenda,” he added, “that would include improved diagnostics and accelerated development of vaccines and drugs.”

Quoting Mahatma Gandhi, Hotez said, “A civilization is judged by the treatment of its minorities.”

He continued, “If wealthy white people were affected by these diseases, it would be on Sanjay [Gupta] and Oprah every night…but it goes sight unseen…I get very frustrated when I see the press focusing on diseases that disproportionately affect wealthy people living in the suburbs.”

Hotez’s talk was part of the NIH Health Disparities Seminar Series sponsored by NIMHD and was taped for viewing at NIHRecord Icon

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