DDT, the Environment, and the Law of Unintended Consequences

Spraying DDT against the body louse, WWII.

Rachel Carson warned the world in the early 1960s, through her now classic book "Silent Spring", about the dangers of single use pesticides, specifically Dichlorodiphenyltrichloroethane (DDT).

This product won the 1948 Noble Prize for its developer, Paul Hermann Müller, given its successful use against arthropods, including by U.S. Allies in WWII to reduce exposure of military troops to debilitating louse-borne typhus and mosquito-borne illnesses, like malaria and dengue fever.

DDT also became popular in the 1950s and 60s as an agricultural pesticide, with tens of thousands of tons of product sprayed on crops for human consumption.  This was because DDT is a lipophilic persistent organic pesticide, which means it bio-accumulates in fatty tissue of animals and moves up the food chain, is found in human breast milk, and also bio-concentrates in the soil, being present for 15+ years.  Carson also warned that DDT was decimating bird populations due to its effect of weakening the egg shell.  In essence see foresaw a "silent spring" coming if DDT continued to be used as an agricultural pesticide.

She also warned, prophetically, that reliance on a single strong pesticide would disrupt ecological systems and have unintended consequences.  Many countries, including the U.S. in 1972, banned the agricultural use of DDT, at the same time the World Health Organization was having initial success in eradicating malaria with the use of DDT.  To date, DDT has been banned in 34 countries and severely restricted in 34 others.

See this NY Times Video clip for an in-depth discussion of this issue.

Take care,

Jim

Fall 2016

Welcome New and Continuing Students! 

A warm welcome to new and continuing students at the Gillings School of Global Public Health this fall semester 2016.

This is Jim Herrington and I have the humble honor of leading the Gillings Global Gateway™team here at the School. The mission of the Gillings Global Gateway™is to promote and facilitate the global public health activities of the School by connecting faculty and students with research, teaching, and service opportunities in global public health, both domestically and overseas.   Naya Villarreal, Program Coordinator, oversees the Global Health Certificate, Global Internships and Funding, and Student International Travel requirements, among other programs in the Gillings Global Gateway™and is a great resource for you.  Dr. Dilshad Jaff, is a Kurdish physician who worked previously for the International Committee of the Red Cross (ICRC) and serves as an Advisor to the Gillings Global Gateway™ on Conflict Prevention and Disaster Preparedness research and programs.  Elisia Black is our administrative assistant who will make you feel welcome when you stop by our offices in 104 Rosenau Hall to seek advice, ask questions, or share your ideas about our global public health.  Also, be sure to check out the Student Global Health Committee (SGHC), led by Christine Pettitt-Schieber, which is "committed to creating awareness and understanding of global health issues among the UNC community through education, advocacy, and service."

A few SGHC members plus Jim and Naya (in glasses)

I came to UNC about a year and a half ago from a 27 year career as a public health practitioner with CDC and the NIH (read my personal story here).  My goal is to use the Gillings Global Gateway™ to build a strong global public health platform with the fantastic students, faculty, and staff at UNC.  This global public health effort at UNC has been long in the making with the School's Associate Dean for Global Health, Peggy Bentley, at the vanguard for over a decade in promoting global public health at UNC with the mantra that "global health is local health."

What's in a Name?

So, what's in a name? What does it mean to you as a student that UNC Chapel Hill is the only public health school in the US (and the world) with "global" in its name?

For starters, just consider the fact that there are over 100,000 daily commercial international flights around the world and over 29,000 daily domestic commercial flights in the US alone. According to the World Bank, air transport carried almost half the world's population or 3.44 billion passengers in 2015.  As you will learn, "person, place, and time" are central tenets to understanding how a disease is distributed in a family, community, or nation.  We have all three when considering air transport.

"Breakbone Fever"

https://en.wikipedia.org/wiki/Aedes

Let's use the dengue virus to illustrate the effect of globalization and why this is important to you as a student at Gillings. A recent article in the Lancet by researchers at Brandeis and Univ of Washington estimates that in 2013 there were a total of 58 million symptomatic dengue virus infections, including 13,586 fatal cases, in the world at a total annual global cost of $8 - 9 billion.   How is it that a little mosquito can wreak such havoc?    In a word: "globalization."

USS North Carolina (1941-1947) had a complement of 2,339 men.

Earlier in my career, I worked at the CDC vector-borne disease lab under Duane Gubler, a dengue expert who taught me much about this pernicious disease. Here are a few important facts that explain, in part, why the dengue burden is so large.

There are five dengue virus serotypes and they are all transmitted in a human-mosquito-human cycle, primarily by the daytime biting, anthrophilic, female Aedes aegypti mosquito, also a vector of Zika virus (a disease with very similar symptoms).

Dengue illness typically presents 4-7 days after infection (indicating rapid viral replication) as a severe fever with muscle and joint aches (hence the nickname “breakbone fever”) and, less frequently, as fatal dengue hemorrhage fever (mainly in children and adolescents), a result of low blood platelets and blood plasma loss. The physiopathology for this shock syndrome is poorly understood.

Discarded containers favored by female Aedes aegypti. Photo: CNN

The spread of dengue increased dramatically during and after WWII, as military troops and troop transport vessels facilitated the movement of the virus and vector, respectively, from southeast Asia to the Pacific Islands, Central and South America, and the Caribbean Islands.  Beginning in June 1945, "Operation Magic Carpet" transported millions of soldiers, marines, and sailors back home, with a peak of 700,000 troops returning in December 1945 from the Pacific theater.   Some researchers suggest that dengue's distribution continued during and after the Vietnam War and other military operations, "From the 1960s into the 1990s, dengue often occurred in US troops in Vietnam, the Philippines, Somalia, and Haiti. We found attack rates as high as 80% and periods of convalescence up to 3-1/2 weeks beyond the acute illness."

Dengue is now endemic in most tropical latitudes around the globe where Aedes aegypti mosquitoes are present. The female Aedes aegypti mosquito can lay eggs in small containers, such as discarded bottle caps, tin cans, and tires.  She is more common in urban tropical environments, given her preference for humans as blood meals (blood protein is necessary for egg production).

Environmental control and health behavior are the primary keys to preventing dengue infection, given there is no treatment for the illness nor a vaccine against the virus, though Drs. Ralph Baric and Doug Widman, UNC Department of Epidemiology, are actively conducting research for a suitable vaccine candidate.

So, I hope using dengue and the Aedes aegypti mosquito help illustrate what "global" means in terms of person, place, and time, and why this is important to you as a student of "global" public health, whether you are working in Sampson County, North Carolina, or  Sédhiou, Senegal.


Very best wishes for a successful year at Gillings!

Jim

99% effective, lasts a lifetime, costs <$1, and can save > 70,000 lives - What is it?

The Answer: A vaccine that for over 70 years has protected 99% of vaccinees against yellow fever, a deadly hemorrhagic viral infection spread by Aedes aegypti and Aedes albopictus female mosquitoes (males do not seek a bloodmeal, unlike females which need the blood protein for egg production).

Aedes aegypti female. Photo credit: James Gathany, CDC.

The Problem:  In case you are not aware, there is a yellow fever (YF) vaccine shortage problem in the DRC and Angola (and likely expanding elsewhere), and the on-going YF outbreak in the Africa region (see below).

Aedes albopictus female.
Photo credit: James Gathany, CDC.

One key objective in “implementation science” is to “…investigate and address major bottlenecks (e.g., social, behavioral, economic, management) that impede effective implementation, test new approaches to improve health programming, as well as determine a causal relationship between the intervention and its impact.”

The YF vaccine shortage offers a prime example of an intervention that is ~99% percent effective, likely producing lifelong immunity, fairly cheap at < $1 per dose in Africa, yet is not accessible to populations that need it, resulting in >70,000 unnecessary deaths annually.  

I recently spoke with Institute Pasteur of Dakar leadership a few weeks ago during my visit to Dakar.  

They are at max YF vaccine production capacity (10 million doses per year) with their current facility (one of 4 in the world) which will need to shut down for several months for renovations to build a newer production unit.

Meantime, the YF shortage continues which Jack Woodall, retired virologist formerly with CDC and WHO, says, “I hate being alarmist, but this is something I’m really panicking about.”

The Solution: This implementation problem should give one pause when an Ebola or Zika vaccine is a “proposed solution” to prevent these devastating diseases, and yet the YF “known solution” cannot meet current demand, even with a diluted 1/5 dose in the interim. 

Considered as an opportunity, this YF implementation science issue would make for a really interesting and usesful thesis or dissertation topic for a UNC student!

Any takers?

Jim