Chapter 10 - Shoes, Window Screens, and Meat
522. Parasitic Diseases — Diagnostic Laboratory Methods, Clinical Aspects and Control Measures. A course of lectures, demonstrations and laboratory exercises in which the animal parasites of man, their vectors and the diseases which they produce are studied. The biological activities of parasites are emphasized. Patients and case histories are used wherever possible; methods of treatment may be discussed, and prevention and control are stressed. Five hours a week during the second trimester of the second year.
Joint clinics may be held in conjunction with the Department of Medicine for the purpose of integrating the teaching of preventive and clinical medicine. These clinics have not been provided in formal schedule but may be held when patients are admitted to the Hospital suffering from such conditions as typhoid fever, malaria, undulant fever, endemic typhus fever, tularemia, and lead poisoning.
Catalogue for 1952–1953, School of Medicine, Vanderbilt University
Parasitology disappeared from the Vanderbilt catalogue course listings the year following the entry above. Our class took the next to last course in parasitology offered at the school. In a few years parasitology would cease to be a course in most medical schools in the United States. It would no longer be necessary. Parasitic diseases—now very rare in the United States—were still present, though in diminishing numbers, in the 1950s, especially in the rural South. The disappearance of parasitic diseases is a story of the extraordinary power of the scientific method in action, coupled with the extreme power of public education. Above all, it is a story of prevention over cure.
The dramatic reduction in the prevalence of parasitic diseases is paralleled by the differences in the amount of written material in the text books then and now. In the 1950 first edition of Harrison's Principles of Internal Medicine, there are more than sixty pages devoted to parasitic diseases, making up nearly 4 percent of the whole book. Four entire sections of the book were devoted to the four classes of parasites infesting man. There was a section for protozoans (malaria being one), a section on nematodes (round worms), a section on flukes, and a section on cestodes (tapeworms).
In contrast, the 2002 Fifth Edition of Cecil's Essentials of Medicine contains a mere four pages under the title “Infectious Diseases of Travelers; Protozoal and Helminthic Infections.” The parasitic diseases are lumped with other diseases that are now limited to third-world and underdeveloped countries. The South of my youth in the 1930s was a third-world, underdeveloped country, still suffering the human ravages, destruction, and remnant diseases of the Civil War and the years of federal occupation that followed.
Dr. Alvin Keller, our professor of parasitology, had served as a public health officer in the South in the 1920s and '30s. He had seen the human misery and devastation produced by parasitic diseases and malnutrition. The principle parasitic diseases affecting so much of the rural South were hookworm, round worms, and malaria. There was another pandemic disease of nutritional origin—pellagra. All of these were completely eradicated by the early 1960s. Dr. Keller made the story of the elimination of these diseases vivid and fascinating.
Most parasites are carried in human feces and must be identified in stool specimens. Malaria, an exception, is carried in the blood. It would be our job as clinical clerks in the third year to be able to find and identify all of the North American parasites in the feces of our patients. Stool lab made up half the parasitology course.
Human parasites are highly variable organisms, and they are very different from bacteria. In the first place, parasites are animals; in contrast to bacteria, most of which can be classified as plants. Parasites range from unicellular protozoans, like the malaria parasite, to highly developed worms that can grow to nearly twenty feet long, like the tapeworm. There is something nauseous, bordering on horror, about a worm taking up residence inside the human body. Somehow, that life form is getting too evolved, too close to a higher form of life for comfort. Bacteria are passively swept into our bodies in air or food or water. Parasites, however, especially worms, often have to find us, crawl through our skin, and then burrow inside us. There is a low-grade dread that they are actually stalking us or, worse, that they have some conscious intent to get us. Finally, there is something really unsettling and alien about an infection inside you that can still crawl around. At least bacteria and viruses tend to stay put, once they settle down.
These unsettling thoughts were vividly brought out when I saw pictures of a round worm crawling out of the nose of a little girl, already bloated from combined hookworm, chronic malaria, and malnutrition. Her mother, in her thirties, stood by her side. She was haggard and looked to be in her sixties. Both were barefooted. Walker Evans and James Agee captured similar images of the rural South in their poetic prose and photographic classic, “Let Us Now Praise Famous Men.” Nearly a fourth of rural Southerners, black and white alike, had the vicious and lethal combination of all three diseases: hookworm, chronic malaria, and malnutrition.
Evans and Agee were taking their pictures and writing about people who lived in the same section of south Alabama where I grew up. They could just as well have been in my grammar school. I recall coming home one day in the third grade in 1939. I asked my mother why the children who came into town from the country were so pale and yellow, but those of us from town were pink. She thought a minute, with a very sad look on her face. She told me they were poor and did not have food or shoes or clothing like us. She did not know of the pandemic of hookworm or malaria or pellagra, and the resulting anemia that underlay their pallor.
It was only when I learned of the high prevalence of these diseases across the South that I understood what had afflicted so many of my classmates. Dr. Keller made the epidemiological figures vivid when he told stories of families and patients he had treated earlier in his career.
In addition to my epidemiological interest in the diseases, the lives of the parasites themselves fascinated me. Nothing in science fiction can outdo the life cycle of any parasite. Over and over, I was amazed at the complexity of their circuitous lives. I was even more in awe of the many scientists who unraveled these almost unbelievable transformations in life forms. Take, for example, the life of the hookworm, Ancylostoma duodenale in the old world and Necatur americanus in the new world. These worms, almost a half inch long, are carried in the human intestinal tract, where the worm hooks its mouth parts onto the lining of the intestine and begins to suck blood. Periodically, the worm releases its hold and moves progressively down the intestines. Each adult worm drinks about 0.5 ml of blood a day, or a teaspoon in about ten days. The “disease” produced is an iron deficiency anemia from the blood loss. In children, the anemia is often coupled with malnutrition, and those who survived to puberty often showed delayed physical, mental, and sexual development. In the early 1930s, 36 percent of Southerners, black and white, had hookworm infestations.
The life cycle of the hookworm reads like something from an alien world. The adult female hookworm, after copulation (if you can imagine that!) and fertilization, lays about ten thousand eggs per day. The eggs are discharged, unhatched, with the feces. If the ground conditions are moist, the eggs hatch into larvae after a few days, and in a few more days they are infectious. They lay in wait for any bare feet, burrow into the skin, and then make their way into the blood stream. There is sometimes intense itching of the feet, called “ground itch,” in the affected areas. The larvae then find their way to the lungs, where they burrow into the small air sacs. Then they migrate up the trachea into the pharynx and are swallowed. During this phase, the patient may develop a cough. Finally, in three to four weeks, the larvae mature in the intestines, attach, begin to suck blood, and lay eggs. The creepy and bizarre life cycle starts all over.
In addition to hookworm infestation, nearly a third of the inhabitants of the rural South had chronic malaria from living in houses with no window screens. Malaria, a word meaning “bad air,” is carried by a mosquito. It produces recurrent chills and fever and great chronic debility. My mother had suffered with chronic malaria for many years of her life, and was partially blind from too much quinine in her youth.
As if malaria and hookworm were not enough, add to those the scourge of malnutrition, specifically in the form of pellagra. About 25 percent of the Southern population had pellagra, a disease caused by lack of tryptophan, an essential amino acid, in the diet. The diet of Southern tenant farmers then consisted almost entirely of corn bread and hog fat belly, neither of which had any significant amount of tryptophan. A deficiency of tryptophan produces pellagra, which is manifested by severe chronic diarrhea and a vicious skin eruption on the exposed body parts. The final phase of pellagra is mental deterioration, dementia, and death.
By the mid-1930s, not only was the source of hookworm known, but equally important, scientists had unraveled the causes and prevention of pellagra and malaria. Through the efforts of the Rockefeller Foundation and the public health departments of the states, a massive education campaign was set into motion. The final result of that campaign was to render the South free of all three of its ravaging diseases: malaria, by controlling mosquito reproduction and screening doors and windows; pellagra, by teaching the need for meat in the diet and by vitamin supplementation; and hookworm, by the wearing of shoes. I don't know of a more dramatic and successful story of the use of science and education to eliminate disease on such a wide scale. The modernization of the South could not have been considered until those three diseases were controlled.
In addition to learning the life cycles and epidemiology of the parasites, we learned to identify the parasites under the microscope. The stool lab sessions in parasitology stood in stark contrast to the fascinating lectures of Dr. Keller. Every Tuesday afternoon, immediately after lunch, we gathered along the long black benches of the student lab. We were to learn to recognize all of the parasites that infested humans, at least those found in feces.
As junior and senior clinical clerks, we would be responsible for examining all stools on every patient we saw. The purpose of the afternoon lab was to teach us how to do that. We would be required to look for and identify all ova and parasites, called “stool for O and P” on the intern's yellow student order sheet. In addition we would test each stool for occult blood. Stool lab, as we called it, became—above all else—a test of our willpower over more visceral reactions.
Some poor soul, somewhere deep in the basement of the medical school, kept each parasite sustained in vats of human feces. Each Tuesday, these large ceramic vats were wheeled into the lab on a large pushcart. One vat was marked “hookworms,” another “ascaris” (round worms), another “tenia solium” (human tapeworm), and still another “giardia” (“when available” was taped underneath).
By two o'clock, the odor of the lab (stench is more accurate) was overpowering. It took all the stamina and determination I could muster to stay at my desk looking down into the drop of black fluid spread out on the slide. This put the fecal specimen only a few inches from my nostrils. It was like sticking my head into a cesspool or septic tank. Survive the stool lab, and you could handle nearly any kind of filth and remain functional. The faculty told us over and over that nothing human is repugnant. The stool lab in parasitology was the acid test for that statement.
Gagging was contagious. When a single gag happened, it swept throughout the lab, going out of control within seconds. One gag and then two gags and then three gags, then a whole bench gagging. By that time, one or more students ran to the hallway for some relief and fresh air. No one actually vomited, but some came very close to it. The gagging brought hysterical laughter from the remaining classmates, and then the cycle would repeat itself. Gradually, over the course of several weeks, the gagging ceased as we became more and more immune to the foul smells or wretched appearances of the worms. In addition to learning to deal with an unpleasant task, stool lab gave me great respect for what the preceding scientists had endured in their search for truth about parasites.
Both Dr. Kampmeier, who would teach us physical diagnosis, and Dr. Keller impressed over and over that no disease had ever been eliminated by any treatment. Diseases cannot be eliminated by treatment. The reason is obvious. Until the reservoir of a disease is contained, removed, or barred from human contact, the disease will persist. Treatment is always an action downstream from the cause. Treatment is always an after-the-fact reaction.
I cannot think of a better example of the power of the scientific method, of prevention, and of public education than the story of the unraveling and elimination of parasitic diseases and pellagra from the rural South. No treatment was involved. All it took was wearing shoes, installing window screens, and eating lean meat.
Reprinted with permission from Hillsboro Press.
Copyright 2003 by Clifton K. Meador, MD
