“Spillover” by David Quammen

Regular readers don’t need to be told that I’m a bit obsessed with zoonotic disease. It’s what I study, and it’s a big part of what I teach. I run a Center devoted to the investigation of emerging diseases, and the vast majority of all emerging diseases are zoonotic. I have an ongoing series of posts collecting my writings on emerging diseases, and far too many papers in electronic or paper format in my office to count. Why the fascination? Zoonotic diseases have been responsible for many of mankind’s great plagues–the Black Death, the 1918 “Spanish” flu pandemic, or more recently, HIV/AIDS. So you can imagine my delight when I read about Spillover, a new book by David Quammen on zoonotic diseases.

I’ve previously highlighted some of Quammen’s work on this site. That link goes to a 2007 story he wrote for National Geographic on “infectious animals,” which really serves as a preview to “Spillover,” introducing some of the concepts and stories that Quammen elaborates on in the book.

“Spillover” is wide-ranging, tackling a number of different infectious agents, including viruses like Nipah, Hendra, and Ebola; bacteria including Coxiella burnetii and Chlamydia psittaci; and parasites such as Plasmodium knowlesi, a zoonotic cause of malaria. HIV is a big part of the story; Quammen devotes the last quarter or so of the book to tracing the discovery and transmission of HIV from primates to humans, and from 1900 to present-day. He even takes the time to explain the basic reproductive number–something that’s not always a page-turner, but Quammen manages to do it well and without being too tangential to the rest of the story; much more of a Kate-Winslet-in-Contagion than Ben-Stein-in-Ferris Bueller delivery.

Indeed, “Spillover” is somewhat unique in that it doesn’t read quite like your typical pop science book. It’s really part basic infectious disease, part history, part travelogue. Quammen has spent a number of years as a correspondent for National Geographic, and it shows. The book is filled with not only well-documented research findings and interviews with scientists, but also with Quammen’s own experience in the field, which gives the book a bit of an Indiana Jones quality. In one chapter, he details his adventure tagging along with a research team to capture bats in China, entering a cave that “felt a little like being swallowed through the multiple stomachs of a cow.” This was after an earlier dinner in which he describes his encounters with the an appetizer of the “world’s stinkiest fruit” (I’ll keep the description of the smell to myself) with congealed pig’s blood for a main dish (bringing to mind the scooping out of monkey’s brains in “Temple of Doom”–and the various zoonotic diseases that could be associated with those, come to think of it).

Quammen’s book is an excellent, and entertaining, overview of the issues of zoonotic disease–why do they emerge? Where have they come from? How do they spread? The only thing that’s missing is more of a cohesive discussion about what to do about them. However, that’s rather understandable, as we certainly have less of a grasp of this question than we do about the others (and even with some of those, our knowledge is spotty at best). I hope “Spillover” will inspire another generation of future germ-chasers, as “The Coming Plague” did almost 20 years ago.

“The Fever” by Sonia Shah

Malaria is one of mankind’s most ancient scourges. A century after the discovery of its cause, various species of the parasite Plasmodium, humanity still remains in its deadly grip in many areas of the world. Malaria is estimated to have caused 225 million illnesses and almost 800,000 deaths in 2009, making it one of the top infectious disease killers. Many of these deaths occurred in children under the age of five.

Shah traces the history of malaria from the introduction of the parasite into the human population to modern-day controversies about malaria treatment, research, and funding. It’s a fast-paced read; informative but never dry. Indeed, Shah makes much use of metaphor; sometimes, to the detriment of the scientific narrative, in my opinion. However, that’s more of a minor issue to me.

Shah begins the book with an anecdote about her own childhood as an American visiting her relatives in India; sleeping under a bed net while her cousins sleep in the open, fearing mosquitoes, and India, and being ashamed of her fears. She notes later that, when her family hears she is writing a book about malaria, they ask her why–to them, it seems as silly as writing a book about the common cold. Shah notes this several times throughout the book–for example, explaining that many in malaria-endemic regions, people would rather use their bednets for fishing than to protect from mosquitoes, so while programs which deliver such nets can tout high numbers of bednets distributed it doesn’t necessarily mean that everyone who receives one is using them correctly.

Indeed, much of the book is spent discussing the limitations and missteps of anti-malarial programs, past and present, from issues of mosquito resistance to pesticides, to parasite resistance to chemotherapy. Another repeated thread is political will, or lack thereof, in anti-malarial programs, and the ping-pong that is played by many funding agencies. When programs demonstrate success and malaria is reduced, there is little will to continue such programs–which may be hampered in any case by the emergence of resistant mosquitoes or parasites. It’s a messy business, and today’s programs don’t seem to be much better off than those carried out in the previous century.

Shah’s book is a thoughtful read for anyone interested in global health–not only for the history of Plasmodium‘s detection and eventual proof as the cause of malaria (after many false starts), but also for the thoughtful descriptions of global health programs carried out by outsiders throughout the decades, and possible ways to change these and avoid repeating the mistakes already made by predecessors.

Psychological Disorders Associated with Cerebral Malaria

Student guest post by Laura Vonnahme

As a part of traveling to a developing nation, we are often required to take medical precautions. This generally includes a line-up of shots for various diseases, a few other tests, and various regimens of prophylaxis for possible diseases. I have often left these doctors appointments with a line of band-aids on my arm, a handful of prescriptions and a little weakness in my knees. However, I will readily admit that my malaria prophylaxis is often pushed to the back burner; in fact the last time I went to a developing nation, I didn’t even get the malaria prophylaxis until I was in the country and I didn’t even bother taking it for the prescribed amount of time. However, as I readily admit my shortsightedness in the past, I have become more aware of the chronic conditions that can be caused by a single malaria infection.

Malaria is a mosquito-borne disease caused by a parasite, and there are four different species of parasites that cause malaria, Plasmodium falciparum (which is the most fatal), P. vivax, P. malariae, and P. ovale. When initially infected, parasites first enter the liver, then multiply quickly and enter the bloodstream, where they continue to multiply and rupture blood cells2. While P. falciparum causes the most severe symptoms, P. vivax and P. ovale can cause chronic malaria which is characterized by profound anemia, enlargement of the spleen, emaciation, mental depression, sallow complexion, edema of ankles, feeble digestion, and muscular weakness.

In addition, there is a more serious form of malaria caused by P. falciparum, called cerebral malaria, which can be deadly quickly if left untreated. However, a more controversial disease has been linked to malaria as of late. Recently there have been links to cerebral malaria, posttraumatic stress disorder (PTSD) and other psychological disorders in soldiers who have returned from service in areas where malaria is endemic. In particular several studies have been conducted on soldiers who had contracted malaria while in service during the Vietnam War. Dr. Nils R. Varney conducted one of these first studies here at the University of Iowa and reported that many cerebral malaria survivors from the Vietnam War have a number of neuropsychiatric symptoms that can persist for years after the acute illness has been treated. “Cerebral malaria does a number of different things to a patient’s brain that cause a variety of neurological problems,” Varney says. “…patients who survived the illness frequently developed depression, impaired memory loss, personality change and proneness to violence as long-term effects of the disease. These are symptoms that have been reported by many Vietnam veterans for years and are often treated strictly as PTSD.”

The journal article compared the neuropsychiatric status of 40 Vietnam combat veterans who contracted cerebral malaria between 1966-1969 with 40 Vietnam veterans with similar wartime experience who suffered gunshot or shrapnel wounds during the same period. The participants underwent numerous tests for sensory, cognitive and behavioral symptoms. Findings indicate that cerebral malaria results in multiple, major, substantially underappreciated neuropsychiatric symptoms in Vietnam veterans, including poor dichotic listening, “personality change,” depression, and, in some cases, partial seizure-like symptoms. Findings strongly suggest that history of malaria should be considered in any medical, psychological, or psychiatric workup of a Vietnam War veteran because a positive response could result in substantial changes in diagnosis and treatment. Interestingly, these results seen in Vietnam veterans are similar to those seen in British troops stationed in India during in the 19th century during the height of the British Empire. Nineteenth-century physicians documented these cases and considered malaria a leading cause of mental illness in British-occupied regions

Therefore, continued prophylaxis is extremely important for anyone traveling to an area where malaria is thought to be endemic. Thus, while you may think prophylaxis is a nuisance, the pills make you have weird dreams, you cant remember to take the pill every week or you just plain think your invincible, none of these are valid excuses for skipping a necessary malaria prophylaxis.

References

1. CDC – Malaria. (n.d.). Centers for Disease Control and Prevention. Retrieved April 11, 2010, from http://www.cdc.gov/malaria/

2. Malaria. (n.d.). Penn State Hershey. Retrieved April 11, 2010, from http://www.hmc.psu.edu/healthinfo/m/malaria.htm

3. UI/VAMC study says patient’s history of malaria may be a clue to many Vietnam vets’ psychological and other health problems. (n.d.). Retrieved April 11, 2010, from http://www.newswise.com/articles/uivamc-study-says-patients-history-of-malaria-may-be-a-clue-to-many-vietnam-vets-psychological-and-other-health-problems

4. Varney, N., Roberts, R., & Springer, J. (1997). Neuropsychiatric Sequelae of Cerebral Malaria in Vietnam Veterans. The Journal of Nervous & Mental Disease, 185(11), 695-703. Retrieved April 11, 2010, from http://journals.lww.com/jonmd/Abstract/1997/11000/Neuropsychiatric_Sequelae_of_Cerebral_Malaria_in.8.aspx