Parasitology and Vegetarianism

 

By sister initiate Hsu Weilin,
Taipei, Formosa.

        Foreword: At a banquet, a lady ordered only a dish of vegetables because she was a vegetarian. A gentleman whom she didn't know and who was sitting next to her also had only a dish of vegetables before him. The gentleman asked her, "Madam, are you a vegetarian?" She answered, "Yes, how about you?" The gentleman said, "No, I'm not; I'm a meat inspector."

        Being a vegetarian and a medical student, over the years I have acquired a deeper understanding and greater affirmation of the benefits and necessity of a vegetarian diet for human beings. Through studying scientific research, I hope that more people will come to realize the importance of a vegetarian diet, the relationship between cause and effect, and the harm that a meat-based diet can cause to the body and mind. Since ancient times, traditional Chinese medicine has emphasized, "With the positive energy within us, the negative force cannot annoy us." Therefore, it is better to prevent than to cure illness. If humans choose to consume food that is beneficial to the body, mind and spirit, adopt a correct, healthy and nutritious concept of vegetarianism, and ensure the hygiene of their diet, they should have no fear of harm from toxins, and thus live a freer, healthier, happier and more relaxed life.

        Some people defend meat eating with the excuse that the human body needs it for proper nutrition and good health, but hospitals are still packed with patients, most of whom are meat eaters. In these cases, meat eating obviously failed to relieve their painful situations and symptoms. Conversely, they have acquired many undue illnesses thanks to meat-based diets. This reminds me of a statement made by the famous vegetarian physician Dr. J. H. Kellogg at a vegetarian banquet: "How delightful it is for us to eat vegetarian food, in that we don't have to worry about from what cause the things that we eat died!" After gaining a better understanding of the truth, shouldn't we be more cautious before picking up our forks and spoons to dine?

The relationship between parasites and their hosts and the forms of infection.

        Depending on their relationship with their hosts, parasites can be classified into six categories, the first being ectoparasites, such as lice, which live on the surface of the body. Another group, the endoparasites, including tapeworms, threadworms protozoa, and other organisms, live in the body cavities, intestines, organs and cells of their hosts.

        Since these latter parasites largely live in body cavities and intestines, we can easily imagine that their origin is directly related to the living habits and diets of their hosts. Eating the flesh of carnivores and herbivores, including the surface and interior parts of cows, pigs, fish, and shrimp, is one of the major causes of parasitic infection in the human body. The most common pathway for human infection is the mouth. For example, the eggs of roundworms and whipworms and the mature cysts or larvae of some other parasites enter the human body through contaminated food or drinking water. Infection from plants is mainly due to eating them raw, which can be easily avoided. However, as for the other categories of parasites, unless you are a vegetarian, please be cautious about acquiring them. Besides these sources, livestock excrement is also a source for many types of parasites. Humans can be infected through the skin, through food or water by mosquitoes and flies, through human and animal waste, through contaminated water, and other means.

       Other examples of parasites harmful to the human body are the helminthes, which are classified as follows:

1. Nematodes (worms): Ascaris lumbricoides (roundworm); Enterobius vermicularis (pinworm); Ancylostoma duodenale (European hookworm);
2. Trematodes (flukes): Clonorchis sinensis (Chineses liver fluke); Fasciolopsis buski (intestinal fluke);
3. Cestodes (tapeworm): Taenia solium (pork tapeworm); Taeia saginata (beef tapeworm).
Protozoa (one-celled creatures) that invade the body cavities: Entamoeba histolytica; Entamoeba coli.

       Parasites cause illness to the host through the following three actions:

1) Extracting nutrients: Parasites derive nutrients from their hosts for food, for their growth, for reproduction and for survival. This is one of the most common harmful effects that parasites have on their hosts. For example, roundworms and pork tapeworms live in the intestines and rob the body of nutritious substances in the intestines, thus causing malnutrition.

2) Mechanical action: Parasites can endanger the host through obstruction, compression and direct damage. For example, a large quantity of roundworms in the intestines can cause intestinal obstruction; cysticercus cellulosa can apply pressure to the brain tissues, causing epilepsy; intestinal flukes stick to the mucosa of the intestine with suckers, which can cause inflammation, hemorrhaging or even destruction of intestinal tissue.

3) Chemical action: The stimulating action of metabolites (products of metabolism), excretions and secretions from parasites, and chemical substances generated from dismembered dead parasites can cause many types of damage to the human body. For example, the protozoon Entamoeba histolytica secretes histolytic enzymes that dissolve the intestinal mucosa and submucosa (mucous membranes in the intestines and the tissue underneath), causing ulcers. If there is a large quantity of larval secretions in the tissues, severe allergic reactions may result, causing anaphylactic (allergic) shock. When some parasites suck blood from the human body, they inject secretions, which have the functions of thinning the blood and creating local irritation which causes tissue inflammation.

        When the defensive power of a host is greater than the invasive power of parasites, the parasites entering the organism are totally destroyed or expelled from the body. When the defensive power of the host is temporarily equal to the invasive power of the parasites, a small number of parasites can live or reproduce in the body. Though they may not cause harm or clinical symptoms to the organism, the host will become a carrier of pathogens (disease-causing agents). When the defensive power of the host is weaker than that of the invading parasites, obvious pathological changes and clinical symptoms will appear in the host, turning the host into a parasite-infected patient.

        The tapeworms most commonly found in the human alimentary canal are Taenia solium (also called the pork tapeworm or armed tapeworm), Taenia saginata (the beef tapeworm or unarmed tapeworm), and Hymenolepis nana (the dwarf tapeworm). Now we will use the pork tapeworm (Taenia solium) as an example. The adults live in the small intestines of humans causing tapeworm disease. Their larvae, which are called cysticerci, live in the flesh of pigs or humans, causing cysticercosis. When people eat raw or incompletely cooked pork containing cysticerci, the cysticerci are stimulated by the bile in the alimentary canal and retract their heads so as to hook onto the intestinal mucosa. Proglottids (segments) grow continuously from their necks and form adult worms in two to three months. Usually, there is one adult worm in the human body, but there may also be several of them. The life span of adult worms can be over twenty-five years. Their larvae living in the human body cause cysticercosis (tapeworm larva infestation), and do more damage to the human body than do adults, depending on which part of the body they live in, and their quantity.

        The number of cysticerci (tapeworm larvae) living in a human body may range from just one to tens of thousands. The parts of the body the larvae live in, in sequence, are subcutaneous tissue (tissue beneath the skin), the muscles, the brain, the heart, the liver, the lungs, and the peritoneum (abdominal wall). When they live in the subcutaneous tissue and muscles, subcutaneous nodules form, often in groups, mostly in the head and torso, and less likely in the limbs. Usually, there are no obvious symptoms, only some muscular soreness. If tapeworm larvae live in the brain, they cause increased pressure in the head, headache, nausea, vomiting, unconsciousness, blurred vision, and epilepsy. More severely, they can even cause hemiplegia (partial paralysis), paraplegia (paralysis of the lower body), aphasia (inability to communicate) and mental problems. If they live in the eyes, vision is affected, very often the movement of worms can be seen, and in severe cases, loss of sight can occur.

        Entamoeba histolytica is also called Amoeba dysenteriae, and lives mainly in the colon of humans. Under certain conditions, it can penetrate the intestinal wall and enter the blood stream, causing amebic dysentery and various types of amebiasis (infection with amebae).

        In recent years, threatened by the so-called "Mad Cow Disease," the chicken plague in Hong Kong, and other cases of livestock and poultry contamination, people have become more alert and aware of the severe problem of parasites, bacteria, and viral infection. Thus, for the sake of health and safety, more people have chosen to replace their meaty diet with a nutritious vegetarian diet. Vegetarianism therefore is not only a trend of our times, but also a kind of awakening.