The most under diagnosed health problem in the West, parasites may be responsible for a multitude of conditions from joint pain and chronic fatigue to many general disorders of the gut and immune system
Few of our doctors in civilised Western nations are trained to recognise the signs of parasitic infestation. Yet parasites do live among us. According to a number of experts, they may be the single most under diagnosed and under appreciated health threat in the West.
Parasites, which can be broadly classified as either protozoa (such as Giardia and Cryptosporidium), worms (including roundworms, or nematodes and tapeworms, or cestodes), or flukes (also called trematodes, which attack various body tissues with powerful suckers), have been associated with a wide range of diseases. Eminent doctors, such as WDDTY panellist Dr Leo Galland, have spent many years researching the effects of human parasites on health. Indeed Dr Galland has gone on record suggesting that "every patient with disorders of immune function, including multiple allergies (especially food allergies), and patients with unexplained fatigue or with chronic bowel symptoms, should be evaluated for the presence of intestinal parasites".
As recently as 1987, a group of American researchers from the Centers for Disease Control and Prevention analysed the results of 216,275 stool specimens, examined by state laboratories across the US. They found parasites in 20 per cent of the samples (Am J Trop Med Hyg, 1994; 50: 705-13).
The most common were Giardia intestinalis, Entamoeba coli, Endolimax nana, Blastocystis hominus and Entamoeba histolytica, but nematodes were also found. Their conclusion was that parasites were being overlooked as an important cause of gastrointestinal (GI) illness in the US.
Other reviews clearly illustrate the extent of the problem. According to the report Parasitic Diseases (Despommier, et al, New York: Springer Verlag, 1995), the number of people worldwide who are infested with the different classes of parasites is: nematodes, 1 billion individuals; cestodes, 300 million; trematodes, 300 million; and protozoa, 1 billion. This gives some credence to the oft quoted statistic that at least 50 per cent of the world's population is infested with at least one parasite.
Although parasites, when they do occur in the West, have been considered largely a problem of rural areas, this is also untrue. Recent outbreaks of Crypto-sporidia, Cyclospora and Giardia in metropolitan and relatively affluent areas, such as New York City, Las Vegas and London, suggest that no area and no social class is exempt. Indeed, the largest outbreak in US history, affecting over 400,000 people and killing 100, occurred in Milwaukee, Wisconsin.
Parasites latch on to those whose immune systems are functioning poorly. Generally, individuals whose immune systems are already compromised from chemotherapy for cancer or from immune suppressing drugs for AIDS are especially vulnerable to parasitic infections. But because we are all bombarded daily with substances which overstimulate and exhaust our immune systems, we are all vulnerable.
Most doctors have no training in tropical medicine or parasitology, and simply would not recognise the signs of parasitic infestation. Many common symptoms, such as nausea, gastrointestinal upset, insomnia and constipation, can easily be attributed to other diseases. Consequently, doctors rely on routine tests to provide a diagnosis. Such tests will commonly yield false results, leaving the real cause of the illness uncovered.
Should a patient undergo a stool test, this may also prove to be misleading. Single stool tests are unlikely to be conclusive. To be reliable, it may be necessary to test three or more samples since the shedding of eggs in human faeces tends to be cyclical. A single test would only be reliable if the sample was taken around the time that the adult parasite lays its eggs. Also, those parasites which inhabit muscles and other tissues will not show up in a stool test. To detect these parasites, tissue samples must be obtained.
The standard stool test is also unlikely to be helpful in detecting those parasites which inhabit the upper GI tract. This is why some physicians believe that the purged stool test, involving the use of a powerful laxative, may be a more conclusive tool, particularly when searching for Giardia, amoeba, roundworm, threadworm, tapeworm, flukes, Cryptosporidium and hookworm. This test should not, however, be administered in cases of intestinal obstruction, pregnancy, appendicitis, high blood pressure or debilitation.
It is believed that taking samples of rectal mucous, which the eggs adhere to, is the most reliable way of determining whether an individual is suffering from parasitic infestation, especially for those who are greatly debilitated. A recent study showed that when this method was used, almost 50 per cent of patients previously diagnosed as having irritable bowel syndrome were discovered to actually be suffering from giardiasis. The patients had been suffering with misdiagnosed bowel problems for an average of seven years (AL Gittleman, Guess What Came To Dinner, New York: Avery, 1993).
Blood tests can only be a general indicator of parasitic infection. Most parasites, except for Giardia and amoeba, will elevate levels of the white blood cell eosinophil, which is produced in response to allergens and infections, in this case the parasite. Blood tests can also be used to detect specific antibodies to such organisms as Entamoeba histolytica, Toxoplasma gondii, Leishmania, Strongyloides and flukes. However, these may not be entirely reliable in individuals who are already so immune compromised that they cannot produce antibodies.
But at the moment, diagnosis is almost a moot point since the majority of doctors simply would not consider the search for parasites as a first option in treatment. Because of this, patients can be left with damaging parasites infesting their tissues and organs, leeching essential nutrients from their system and causing extensive gut damage. But more importantly, a misdiagnosis leads physicians to prescribe powerful drugs which can further depress the immune system leaving the individual open to more prolific infestation.
Once parasites take up residence, symptoms may appear immediately, within a few days or, in some cases, not for months of even years. Infected individuals may also be asymptomatic, showing no symptoms themselves but still capable of transmitting parasites to others. In latent cases, it is usually another illness, surgery or stress, which further challenges the immune system and may, in turn, bring on symptoms of infestation.
Links with other diseases
A number of doctors who now believe that parasites are implicated in a number of the diseases which plague modern society, such as cancer, AIDS and Crohn's disease. A recent study of over 400 chronic fatigue immune deficiency syndrome (CFIDS) patients in New York revealed that an incredible 93 per cent had some form of parasitic infestation (J Nutritional Med, 1990; 1: 27-31).
Although we tend to associate giardiasis primarily with gastrointestinal symptoms, severe hypothyroidism may also result from infection with Giardia lamblia (Exp Clin Endocrinol Diabetes, 1996; 104: 180-2).
The largest of the intestinal nematodes (worms), Ascaris lumbricoides, migrates within the body tissues. As this parasite progresses through the lungs, the allergic response which is generated may cause pneumonia, and in animal models it has been linked with the development of idiopathic bronchial asthma. Children born to infected mothers have a much higher susceptibility to the same infection later in life (Nat Arch Allergy Immunol, 1996; 109: 3-10).
In immune compromised patients, Cryptosporidium and Giardia infestation can cause malabsorption and nutrient loss (Clin Microbiol Rev, 1992; 5: 93-100; Schweiz Med Wochenschr, 1995; 125: 899-908). In those with AIDS, deaths due to diarrhoea approach 80 per cent. Among those who survive, other problems such as chronic coughing and low grade fever may occur.
Dr Hulda Clarke, author of The Cure For All Diseases (San Diego, California: ProMotion Pubishing, 1995), believes that the most dangerous of all the parasites is Fasciolopsis buski. This intestinal fluke lives among water plants, such as water chestnuts, bamboo shoots, watercress and lotus root plants, and enters the body when an individual ingests these. Although this fluke is traditionally found in Southeast Asia, Dr Clarke claims to have found it in every case of cancer, HIV infection, Alzheimer's, Crohn's disease and endometriosis that she has examined.
Dr Clarke's work centres mostly around flukes, so she cannot say whether the water pollution link is also applicable in tapeworms and roundworms. It is fair to say that conventional practitioners view her conclusions as a red rag to a bull. Nevertheless, she reports high success in curing disease through a programme of detoxification and the use of high frequency electronic "zapping" as part of a recovery programme for parasites (see box p 2).
Where do they come from?
Perhaps the most disturbing aspect of parasite infestations is that they come from many of the things which we need in order to survive: the water we drink and bathe in, the food we eat, the air we breathe. Pets, sexual practices, crowded day care centres and international travel are also implicated.
Drinking water is increasingly becoming an act of faith. Apart from being polluted with high levels of toxic chemicals, studies by American water authorities have shown that the Giardia cyst can survive for up to three months in cool or cold water, while the Cryptosporidium cyst can survive for between 12 and 18 months (Journal AWWA, Feb 1988: 14-27). Cryptosporidium is now the leading cause of water borne illness in the US, with over 80 per cent of surface water samples and 28 per cent of drinking water samples taken from hundreds of sites across the eastern and western US found to be contaminated with this parasite (Appl Environ Microbiol, 1994; 57: 2617-21).
While water is the most common source for parasites such as Cyclospora, food can also harbour this parasite. In the spring of 1996 and 1997 in the US and Canada, an outbreak of cyclosporiasis was associated with the consumption of fresh Guatemalan raspberries (Ann Intern Med, 1999; 130: 210-20). The outbreak affected more than 1000 individuals.
Cryptosporidiosis has also been associated with the consumption of school milk. In West Yorkshire in 1995, 50 children became ill with gastrointestinal symptoms after drinking school milk. Lengthy questionnaires pinpointed the source as being a small scale local producer who had an on farm pasteuriser (Lancet, 1997; 350: 1005-6). Other studies have associated Cryptosporidium with drinking unpasteurised milk (BMJ, 1990; 300: 774-7; Eur J Clin Microbiol, 1987; 6: 56-9).
Cryptosporidium oocysts (eggs in an enclosed sac) cannot survive the pasteurisation process (App Environ Microbiol, 1996; 62: 2866-8), so it is likely that the West Yorkshire outbreak was due to inadequate pasteurisation.
Access to food from many other countries means that we are exposed to the parasites which are common to those cultures. Toxoplasmosis due to Toxoplasma gondii is a latent parasitic infection. In pregnant women it is related to a higher risk of congenital abnormalities. While the usual advice is to avoid contact with cat litter boxes, contact with contaminated meat is considered by some to be an even more important cause of T gondii (Emerging Infective Dis, 197; 3: 443-52).
Drug treatments, which are often oral pesticides, are not always effective. Indeed, in every case of infestation, the need for treatment must be weighed against the often high toxicity of the drug. A decision to withhold therapy may also be wise, given the number of side effects which pesticides can cause (Med Let Drug Ther, 1992: 1). For instance, mebendazole, often chosen to treat roundworm infections in children as it can be administered in a single dose, can cause abdominal pain, diarrhoea and skin reactions.
Metronidazole (Flagyl), which is used to treat giardiasis, amebiasis and trichomoniasis, can cause nausea, headaches, disorientation, and can leave a metallic taste in the mouth. It can also encourage yeast growth, further depressing an already compromised immune system.
The parasite expert Dr Louis Parish has warned of the misconception that "treatment with a single course of metronidazole is 90 per cent effective". Twenty five years ago this may have been true, but the protozoa rapidly become resistant. Today, the single course cure rate is less than 5 per cent. Furthermore, approximately half of the patients treated with metronidazole complain of side effects, and 10 per cent flatly refuse to ever take it again (Townsend Letter Docs, 1990; 89: 832-5).
The ability of parasites to adapt is actually quite remarkable. Like bacteria, parasites can use their encysted or resting periods to toughen their cell walls to a nearly impermeable state. This adaptability was dramatically illustrated after several outbreaks of Cryptosporidia infection rocked American towns in the late 1980s and early 1990s. As awareness grew that the outbreaks were linked to water quality, debates raged about the "proper" use of chlorine and how this powerful disinfectant could keep outbreaks at bay. Many outbreaks were from water sources which met all current standards for quality.
There followed a sudden surge of outbreaks of legionnaires' disease, cryptosporidiosis and giardiasis among people who used chlorinated hot tubs, public spas and swimming pools (Am J Epidemiol, 1984; 120: 809-17; JAMA, 1985; 253: 535-9). The Centers for Disease Control and Prevention was forced to admit that "Cryptosporidium oocysts are resistant to disinfection by chlorine". Environmental Protection Agency laboratory studies later showed that Cryptosporidium could actually live on Clorox (an extremely strong household bleach).
In fact, the main treatment for parasites is prevention and, failing that, a cocktail of herbal remedies (see box, p 4). This centres around keeping our immune system strong and our guts healthy so that parasites are both less inclined and less able to take hold. In the meantime, practitioners must be much more sensitive to the problem of parasites. In the coming years we may find that our recognition of parasites may parallel that of candidaneglecting it for many years before finally admitting how fundamentally it can affect human health.