Genesee Bird And Pet Clinic 

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The Book-People, Pets, and Parasites—A New Awareness of infections shared by people and their pets.

I   The Big Four

          June 12, 2003 marked my thirty fifth anniversary as a veterinarian. After 3 years in the US Army veterinary corps and seven years of small animal practice, I felt that the practice of veterinary medicine was for me very unfulfilling. I suppose one could say that I had the fantasy that I really would effect the true healing of my patients. But that, as it turns out, has really been my quest these past 35 years. The question has really been, “Why all the suffering, why are so many creatures ill?”

After I had been out of veterinary school for ten years I began looking at chiropractics, physical therapy, and massage (I took a massage certification course in 1978) as possible alternatives to veterinary practice. The end of my quest for the satisfaction of my need to understand optimal health found me studying Chinese medicine and becoming a licensed acupuncturist, all the while remaining in private veterinary practice. This was the beginning of my career in human medicine.  It was 1994.

          One afternoon, sometime during the second year of my acupuncture studies, I was assigned to monitor a patient during his acupuncture treatment. He was an older man lying supine on a treatment table and had a full array of acupuncture needles in place, not unlike what one might have seen at Custer’s last stand. I stood behind his head facing toward his feet, and my mind began to wander from the description of his illness. It was then that a voice, not unlike the booming voice which handed down the commandments to Moses, shouted to me. “They’re all doing it to themselves,” it said.

          This experience left no small impression on me, and I reflected upon it frequently. One question that occurred to me during one of those reflections was, “What about the animals? Are they doing it to themselves, too?” In a way, which I will explain soon, they are doing it to themselves, but through us-----their masters, companions, and often their best friends.  So, more accurately, we are doing it to them too!

          So what is this “IT” that we are all doing to ourselves and our dear friends the animals?  To understand “IT”we must first look at the common threads of all illness.

          Since I began my medical career anew a number of years ago tending to the medical needs have both man and animals, I have learned more about animals by working with humans than vice versa. And as my new career progressed, I began noticing those common threads which composed “IT.”   Aha!

          Those common threads of which I speak, common to all creatures in less than optimal health, are mental-emotional-spiritual stress, putting imperfect food into an imperfect tube(stomach and intestines), somatic(musculoskeletal) dysfunction, and the biggy---where are the parasites? Carrying one or more parasites will keep you or your pet forever from realizing optimal health and will lock one into a chronic disease state forever. We have found in our laboratories that just about everyone who has a chronic disease such as fibromyalgia, arthritis, chronic fatigue, and so on, will usually be carrying at least one and often up to four parasites.

           To summarize, these four factors and their effect on our hormones or endocrine system, first and foremost the adrenal glands and the autonomic nervous system (that part of the nervous system which runs our organs such as secretions and movement of intestines—which can be thought of as the “automatic” nervous system) are the precipitators of all disease processes of animals and man. Please note that we have not mentioned environmental pollutants such as heavy metals like lead, mercury, and cadmium. These too, affect the body as part of the imperfect food put into the imperfect tube.

The Biggest Part of “IT.”

           In my opinion the commonest emotion that people in American society carry is fear, with fear of financial failure or loss leading the pack. In Chinese medicine, i.e., the emotion of fear is synonymous with the kidney organ system. The kidney is our life force, composed of the energy we are born with and that which we generate throughout life. The energy we generate throughout life comes from the food we eat and the air we breathe (oxygen). All things in Chinese medicine are composed of yin (cooling, moistening, nourishing, and resting attributes, solid substances and organs) and yang (moving, transporting, warming, transforming energy and hollow organs). The kidney yin is the fuel or body substance, like blood and tissues, and the yang is the flame that we feel as active energy. If stress goes on long enough, the flame will first burn brighter, but as the fuel in exhausted, the flame dims.  

 The Chinese kidney translates into the pituitary-adrenal axis in western physiology-- the endocrine system.

           The concept or the need to rest and not work and worry so much is not awareness new to the twentieth century.  It is   mentioned in the Bible thousands of years ago (Genesis, Psalm 127, the Book of Matthew (6:26), and amply throughout Taoist thought as well 2000 years ago. Constant stress (needing to be “up” all the time, the use of stimulants, etc,) leads first to the over stimulation of the adrenal glands and later to their exhaustion. Remember, this is the Chinese kidney or the endocrine system which is burning out.  This phenomenon opens the door for the next three aspects of “IT” and can also in turn be affected by them.

            So how do we contribute this part of “IT,” emotional stress, to our beloved pets and their illnesses?  In the past 30 years the intimate relationship between people and their pets has become recognized and studied extensively. An organization was formed some twenty five years ago for the study of the human-companion bond. It has now evolved into the Delta Society (www.deltasociety.org), a wonderful association involved in animal assisted activities and therapy such as service dogs that work with invalids, visit nursing homes, and so on.

            Then there are the senses of dogs and cats. Dogs can hear things a lot farther away than humans, and also a larger range of sounds (the dog whistle is twice the frequency range than that which can be heard by humans. Dogs and probably cats have 25 times more olfactory(smell) receptors than humans, and can see twice as good as humans in the dark. But there is more. What about the sixth sense of animals---things that cannot be explained, like dogs and cats finding their way home from hundreds of miles away, and knowing when storms and earthquakes are coming?

            I often recall the story I saw on one episode of the series “Nature” on PBS television (Also see the book entitled, “Dogs That Know When Their Owners are Coming Home,” by Rupert Sheldron, Three Rivers Press).  The documentary was about a lady in England who worked a twenty minute drive away from home. She lived in the same house as her father.  Her little dog, a black sheepdog mix, about 30 lbs or so, would sleep almost constantly during the day, but became animated when his mistress left her place of work.  This excited behavior would occur no matter what time of day she left the office. He knew, among other things, that dinner would soon be on the table. But how did he know? She was so far away.

           I often tell the story of animals that are spending the day in my clinic for one procedure or another.  They sit there in boredom like a “lump” all day until the moment their “owner” (we now call them companions or guardians) pulls up in front of the clinic.  They are separated from their companions by the five doors in my clinic (six if you count the car door).  The minute that companion’s car pulls up in front of the clinic, the animal is up and animated—he knows who’s here to take him home.  How did he know?  They are so far away.

           So how hard is it to understand that these animals, dogs and cats, take on or share the mental-emotional stresses and neuroses of their owners?  I have had cats end up in the hospital with projectile diarrhea and bladder “infections” when hubby and wife would have their battles. Add to that the environmental stresses of pollutants-----chemical, noise, and electromagnetic forces. And we haven’t even gotten to poor diet yet.

Putting Imperfect Food into an Imperfect Tube

             Or, “How can a little thing like the stomach cause so much trouble?”  Ever hear the statement, “He doesn’t have the stomach for it?”  Sounds like the question is really about one’s intestinal fortitude (there’s another allusion to the role of the gut again) or will power or “stick-to-itiveness.  How can the stomach or intestines be involved with ones will power?

         In Chinese medicine, the stomach is actually the area that is considered to be imbalanced when one is in a state called manic depression, and is treated in Chinese medicine by purging the stomach with herbs that cause vomiting---and it works.

         Let’s start our conversation of the modern western version of the problem by talking about a problem called chronic atrophic gastritis, a condition which results in hypochlorhydria, or not enough stomach acid to digest food in the stomach. I came to learn about this problem in 1989 when I was diagnosed with the problem. We should understand at this point, that anatomically (how the stomach is built) and physiologically (how the stomach works biochemically) is virtually the same in humans, dogs and cats, with only a few subtle differences. This condition is mentioned in a medical manual known as the Merck Manual (for humans) as well as Dr Donald Strombeck’s book, “Strombeck’s Small Animal Gastroenterology.” (Dr Strombeck is a foremost authority on small animal gastroenterology)

           In my experience, and apparently Dr Strombeck’s, hypochlorhydria (not enough stomach acid to properly digest food in the stomach) occurs in our canine as well as our feline friends. In humans, as I mentioned, this condition is referred to as chronic atrophic gastritis. I say this because I have seen a large numbers of chronically ill animals, especially those with chronic vomiting, many of whom have even had gastric and intestinal biopsies.  The first thing I give them is hydrochloric acid supplementation.  Ninety nine percent of these animals get better with hydrochloric acid supplementation.

          Causes for this condition are a decrease in parietal cells (the acid secreting cells in the stomach lining) either in activity or number. Sometimes perhaps, they just wear out.  In humans, for instance, according to the Merck Manual, 40% of people over 40 years, and 50% of those over 50 years of age, have this problem. In other cases, they may be inhibited by food intolerance or food allergies. In one study of asthmatic children, stomach acid production was shut down for 8 days following the ingestion of one glass of milk.

          We have all heard of Dr Adkins diet, which suggests a low carbohydrate diet for people. These carbohydrates, almost all of which originate from grains, are refined or ground into flours.  This equates into the feeding of sugar because these substance all have a high glycemic index. A high glycemic index means that the substance quickly gets into the bloodstream and causes a rise in blood sugar similar to what happens when one ingests refined sugar.  If one were to examine the ingredients on the label of commercial dog and cat kibble, one would find that these contain high percentages of these same refined grains.  Why are we feeding carnivorous animals refined starches when the overwhelming opinion of human medical doctors in the United States is that “we are killing ourselves (humans) with high carbohydrate diets?  What then are these types of foods doing to the stomachs of dogs and cats—obligate meat eating animals? As we mentioned earlier, their stomach anatomy and physiology is almost identical to that of humans, except that the stomach is 25% of the entire gastrointestinal tract in carnivores versus 10 % in humans.

           When mammals are deficient in stomach acid, a multitude of physiological processes do not happen. When we don’t digest our food properly in the stomach, the stomach does not empty in a timely manner. Emptying of food from the stomach is totally dependent upon acidity of its contents and not the automatic opening of the orifices of the stomach controlled by nerves. The opening of the stomach valve into the small intestine (the orifice leading from the stomach to the small intestine is called the pylorus) depends upon how acidic the partially digested food in the stomach gets. The pylorus does not automatically open after the food spends a standard amount of time in the stomach. When food sits in the stomach unacidified, it putrefies and forms acid products. This is the phenomenon which is the main cause of esophageal reflux disease, or heartburn and bloating and gas after eating.

           Also, without adequate stomach acid, whole cascades of other processes don’t happen. B vitamins, especially B12 (due to a lack of stomach intrinsic factor-the B12 carrier) aren’t absorbed. Long before we get megaloblastic anemia, larger than normal red blood cells from lack of B12, we get the breakdown of the nervous system itself.  B12, along with folic acid, is essential for the maintenance of the health of our nerve cells.  The result is symptoms like insomnia, irritability, depression, and lack of energy.  Do you know anyone with those symptoms?

            Next, without adequate gastric acid, minerals are harder to ionize and are therefore harder to absorb.  The gallbladder also is not stimulated to release bile. Bile emulsifies fats that pick up ionized calcium and other minerals. It is hard to find humans and pets in American society that are not demineralized. Many people have heard of osteoporosis and perhaps the stage preceding it called osteomalacia (bone “softening”).  This results in bone pain and arthritic changes because the bones are soft and the body is trying to shore up and stabilize joints by bringing in more calcium. All bones are covered with a membrane called periosteum, and this periosteum is laden with pain receptors. These pain receptors are very sensitive to the stretching of the periosteum, not only when a bone is broken, but also when it bends in the slightest way, as when the bone is soft. Test your pets bone mineralization by pressing on any bones---long bones of the legs, the skull, or spine. If they are all sore when pressure is applied, this is likely due to demineralization of the bones. This is especially common in cats. These cats do not like to be petted and are very sensitive to being touched along the back, are usually grouchy, and some have even been known to have seizures. If you have known a person who has osteoporosis, they will tell you that they are in constant pain everywhere.

          Calcium is also a major player in the relaxation process, exerting a calming influence upon muscles and the nervous system. We use calcium supplementation along with other minerals to reduce or eliminate seizures in our practice.

           And how about this?  When we are deficient in calcium, we itch------think of it.  How many itchy dogs does the average veterinarian see daily?

           Also, when fats and calcium are mixed together in a basic medium, they form soap. In soap manufacturing, the basic medium is lye. This is exactly the situation which exists in the small intestine when fats and minerals go unabsorbed. The intestinal contents are basic or non acidic like lye. Soap it seems would be damaging to the lining of our intestines don’t you think?

           Could this be one of the origins of our leaky gut syndromes? Leaky gut syndrome is the excess permeability of the intestines which allow large molecules to enter the body from the intestines or leave the body via the intestines. These are substances which ordinarily would not pass the intestinal barrier. And how about the loss of secretory IgA from damage to the intestinal lining? The lining of the gastrointestinal tract and every mucous membrane in the body secretes an immune substance called secretory IgA. This is one of our basic protective barriers to foreign substances (food particles) and microbes trying to get into our bodies inappropriately. This is true of all humans and mammals. If the lining of the intestines is damaged then we are minus this protective barrier. Some people theorize that this is really the origin of all allergies. Substances gain entrance into the body which shouldn’t be there and are too large for the body’s white blood cells, the garbage men of the blood, to remove.  We then form antibodies to these large sized foreign substances in our bloodstream, resulting in chemical-immune combinations called immune complexes. The results of the reactions to these immune complexes depend on the part of the body where those substances and their reactions are found, such as the lungs (asthma), intestinal tract (diarrhea), or skin (itching).

              On still another front, a major barrier to infection with bacteria and parasites is stomach acid. Another factor in this area is Helicobacter pylori, a bacterium which can grow in the stomachs of humans and pet animals. This bacterium is estimated to infect the stomachs of 70% of the world’s human population and 90% of people with gastric ulcers. Gastric ulcers are known to occur in dogs, cats, horses, and swine.  In the latter two species there is a high correlation of gastric ulcers with psychological stress. They occur in high numbers in pigs just before time of slaughter. It is estimated by some that up to 90% of racehorses have gastric ulcers.  Helicobacter species also contain an enzyme system which neutralizes stomach acid, which could make it a major contributor to gastric acid deficiency. Helicobacteria are commonly found in dogs and cats. In one study in fact, it was cultured from 100% of all cats studied.

 Musculoskeletal Dysfunction

              Very few people have been spared the experience of musculoskeletal pain, either from the direct effect of an acute injury or a “bum” back “going out” or the effects of arthritis, especially that which is associated with aging.

            What we need to be aware of in this category is the part that visceral or internal organ dysfunction plays in the precipitation of musculoskeletal pain.   There is a nervous system connection between our internal organs and our musculoskeletal system, especially along the spine.  There is also a residual connection left over from our days as embryos. There is, for instance, a system of acupuncture that treats pain by placing acupuncture needles very distant from the area of pain. I personally have successfully treated calf pain in a human patient by placing needles in the forearm and not where the pain was—in the legs. Did you know that in the earlier stages of development of the mammalian embryo, the arms and legs were all part of the neck?  

          There are also sets of reflexes or neurological connections that we know about that will cause a problem in one part of the body and show up or be manifest as pain in another part of the body. The first is the viscero-somatic (organ to body) reflex.  Here for instance, a problem in the stomach may reflect to the lower part the midback.

           Next we find the somato-visceral (body to organ) reflex.  In this situation, we find, for instance, that a problem in the last thoracic vertebra can result in pain in the external genitalia.

           In a viscero-visceral (organ to organ) reflex, the pain in the gall bladder can cause pain in the liver.

           Lastly, somato-somatic (body to body) reflexes mean that pain in one part of the musculoskeletal system will show up in another part of the musculoskeletal system. Dysfunction in the pelvis may cause problems in the shoulders.

Where are the Parasites?

           This is perhaps the most important and surely the least appreciated part of the paradigm we have named “IT.” Work in our laboratory and a number of others have shown that 22%(one study found an incidence of 38%) of the American populations studied harbored intestinal worms(roundworms, hookworms, whipworms, tapeworms) and one-celled parasites such as Amoebas and parasites named Giardia and Cryptosporidium.  All of these parasites are listed by the Communicable Disease Center(CDC) in Atlanta, Georgia as having the potential of being shared by humans and their animal pets. Parasitism has been demonstrated to be a key factor in the resolution of chronic and difficult to cure illness. For instance, a number of scientists are suggesting a correlation with the feline parasite Toxoplasma gondii and human schizophrenia. So, in other words, resolve the first three factors of “IT” and you can still find yourself with your chronic disease or illness in place. These parasites are also well known for causing internal organ problems, especially stomach, intestinal, and liver disease.  Amoebas also like to live in the brain.

          Many parasites are transmissible from animals to man.  The term for this phenomenon is called zoonosis.  We will hear a lot more later on zoonosis, which is really the subject of our book.

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II   Emerging Diseases (Infectious Maladies on the Rise) and the Big Picture Regarding Parasites

          At the beginning of the twenty-first century, we find emerging disease in all parts of the globe. Seventy five percent of these emerging diseases are zoonotic, as we said, capable of spreading from animals to man. These emerging diseases are manifest in several ways. They may show up as new diseases never seen before, old diseases showing up in a new way, and old diseases showing up in a new place or population. I would add that there are some old diseases the key to which we just overlooked.

          In the first category, most of us are aware that there is a “new disease “called SARS that just came upon us. In the early stages of the study of this disease, SARS is thought to be caused by a distinct virus---- coronavirus.  This family of viruses, incidentally, also commonly affects the lining of the thoracic cavity that houses the respiratory systems of our feline friends.

          Next, we have old diseases showing up in a new way. Although perhaps a less than natural example is the anthrax mailbox terrorism of 2002 in the United States. Anthrax is an ancient disease mentioned in the Old Testament of the Bible. It is most commonly found in cattle but is listed by the CDC under diseases that can be transmitted by house cats.

          Now we come to old diseases that show up in new species. Mycobacterium bovis, cattle tuberculoses, is now a huge problem in deer in Michigan. Bluetongue, originally a bovine disease, has now been found in dogs. Six percent of bats in Australia carry lyssavirus, causing a rabies-like disease. This has now spread to humans.

                   Lastly, in the last ten years we have a multitude of old diseases showing up in new places. We mentioned earlier that Lyme disease was first discovered in Lyme, Connecticut. As of this date, California has more cases of Lyme disease than all other states combined. Leishmaniasis, a parasitic disease found only in the Mediterranean and the Middle East (also implicated in the Gulf War Syndrome) has been found in foxhounds in the United States. Hydatid disease, caused by a tiny tapeworm, used to be found only in arctic foxes.  It has now spread to many species in the US, Canada and Europe. Most recently, monkey pox virus has showed up in the United States, the first time ever in the western hemisphere.

          Sometimes, it’s simply that we didn’t look closely enough at what was going on or need to look at things from a different angle. Take toxoplasmosis, for instance, mentioned earlier. Toxoplasmosis is a one celled parasite for which the house cat is the primary host. We already know that 50% of humans with this disease develop cysts in the brain. Recently, as we mentioned earlier, an article was presented to me that suggested very strongly the association between toxoplasmosis and schizophrenia in humans.  Other researchers are suggesting that multiple sclerosis is a sequel to Lyme disease and other infections. High numbers of multiple sclerosis patients also have significant antibody levels to the canine distemper virus. 

           Why are these phenomena occurring? The answer to this question is to be found by looking at four aspects of human behavior that impact our planet. These phenomena are increased human population, increased mobility of those populations, changes in economics and husbandry of the planet and its creatures, and lastly, changes in information and finance.

          Large increases in population, coupled with increased population movement, have caused various environments to be disrupted. This increase in numbers of humans and their increased movement, have in turn increased movement of indigenous creatures all over the planet.  So for instance, we have the spread of leptospirosis, a spirochete affecting the liver and kidneys of its hosts.  It is the most common disease transmitted by rats. It has increased especially in areas which have seen the advent of adventure tourism. We have seen the spread of West Nile Virus occur in the past several years. Originally found only in the Middle East, it is a viral disease spread by mosquitoes. It affects the central nervous system of animals and man bitten by mosquitoes carrying the virus, and has caused disease and death in over 14000 horses in the United States as well as a significant number of deaths in humans in America. Lyme disease, a tick bourn disease originally discovered in Lyme, Connecticut, has spread to the west coast of the United States. California now has more cases of Lyme disease than all other states combined.  

          One change in husbandry, besides our almost complete ignorance of it, is the feeding of ground up beef carcasses as a feed supplement to cattle in England.  The unfortunate result is that the source of the ground up feed was cattle which were infected with bovine spongiform encephalitis virus, or mad cow’s disease. Also, many people are aware of the commercial overpopulation of breeding swine in North Carolina.  This has led to nitrogenous waste and microbial contamination of ground water supplies as far away as Oklahoma. This is the result in the increase of husbandry efficiency. 

          Closely related to changes in husbandry are changes in information and finance. Mad cow disease mentioned above was allowed to spread further in Europe because of failure of the an eastern European government to monitor its cattle, that is, failure to institute a formal testing or monitoring system for this disease.  It was assumed by this eastern European government that they just didn’t have the disease. When it was finally pickup up by the institution of testing, mad cow disease had spread more extensively throughout Europe. It is assumed that this balking at the initiation of testing was to protect this countries livestock industry.

          With emerging and missed diseases as a backdrop, let’s get ready to move on to our favorite subject: ZOONOSIS-- especially those associated with family pets.  Five percent of visits to human medical clinics are because of infections with animal parasites----too low a number in our experience. Well beyond such diseases as scabies (skin mites that cause intense itching) and fungal infections (ringworm), our recent studies show that many humans with chronic debilitating disease are sharing parasites with their canine and feline family members. Medicine has long known about visceral larval migrans, the migration the larvae of roundworms of dogs and cats in the bodies of humans. The studies, to which I am referring, in addition to roundworms, include Giardiasis, Cryptosporidium infections, and amoebiasis. These last three are one celled parasites which like to live in, but are not limited to the gastrointestinal tract. Amoebas for instance, like to invade the liver, joints, and the brain.

          The highest risk groups for these zoonoses are children, cancer patients, especially those undergoing chemotherapy and radiation therapy, HIV patients, and people with immune system diseases such a fibromyalgia, deep infections, rheumatoid arthritis, scleroderma, and those who have had organ transplants and are taking immune suppressants.

III  The Villains-----common parasites and the way they get around.

          One categorization of zoonoses is by how they are spread. They may be bite related, gastrointestinal, or skin related.

          Generally, Children most frequently encounter zoonotic diseases because they are closer to the ground. That is, they most often provoke biting and scratching by improperly approaching and contacting animals, frequently play in the dirt, go barefoot, and fail to wash their hands after the latter two activities. 

          Zoonotic diseases which are spread directly by animal bites. In this category we find rabies virus that we have all at least heard of. This disease brings a fatality rate of four people for every ten bitten by a known rabid animal. Pasteurella multocida is a highly contagious bacterium found in the saliva of cats. While cats are responsible for only 10 % of humans bitten by animals (dogs are responsible for 80% of humans bitten), 30% of persons bitten by cats become infected, compared with an infection rate of only 6% of dog bites.

          Our next category of zoonotic diseases is composed of those spread by contamination with gastrointestinal contents, usually feces, and which end up in the gastrointestinal tract of the host. Most of these problems are associated with what we call parasites.

          Parasites are those creatures that live on or in another, called a host. The parasite lives off of the host (you, your child or your pet) by feeding off of, or absorbing, the hosts’ energy, food, and destroying the cells of the host itself. The parasite offers no known benefit to the host.

          In this category, we find bacteria such as campylobacter and helicobacter, roundworms, tapeworms, amoebas and one celled parasites called protozoa. Roundworms, tapeworms, and hookworms are worms common to humans, dogs, and cats. The specific names for these worms are Toxocara canis, Toxacara cati (roundworms), Dipylidium caninum (the dog tapeworm), Ancylostoma caninum and braziliens (Hookworms).

            Giardia, cryptosporidium, and some of the amoebas are the most common one celled or protozoon parasites found in people and their pets. In a study done at the University of Colorado, 2.4% of cats harbored Giardia, 5.4% were found to have Cryptosporidium parvum, and 3.9% had the cat roundworm Toxacara cati. As we head east of the Rockies the incidence of hookworms in pets goes up dramatically. In a similar study of dogs and cats at the University of Pennsylvania, 16% of cats harbored roundworms, 0.9% had hookworms, 4% had tapeworms, and 2.4% had Giardia. Of the dogs in the same study, 5.7% had roundworms, 9.7% had hookworms, 1.8% had tapeworms, and 4.7% had Giardia. In a third study of cats done at Cornell University in New York state,

33% had roundworms, 7.3% harbored Giardia, and 3.8% had Cryptosporidium.  The parasites have a worldwide distribution. In a study done in Czechoslovakia, 39% of dogs and approximately 36% of cats had positive serum antibodies to Giardia. In a study done in Japan, Giardia cysts were detected in 16.4% of dogs and 8.8% of cats studied.

          Let us now take a look at each one of these parasites individually.

           Roundworms of dogs and cats have long been recognized as a potential cause of disease in humans. There are three main species of these worms in dogs and cats, and their lifecycles vary somewhat as do the appearance of their microscopic eggs.  Toxacara canis is the primary roundworm of the dog. It can be passed from dog to dog in four different ways. One, the eggs are passed in feces and ingested by the new host. These eggs are extremely resistant to environmental conditions and may remain viable on the ground for up to five years. The infective larvae, premature or baby roundworms, still inside the egg, hatch within the intestines and migrate to the liver. Then it’s off to the heart through the circulatory system, and from here they enter the lungs.  From the lungs they migrate to the windpipe, are coughed up, and are swallowed. After being swallowed, they enter the intestines where they develop into adult worms that begin laying eggs and the cycle repeats itself. The feline roundworm, Toxascaris leonina does not migrate outside the intestine. 

          From the time that the larva enters the intestine until infectious eggs are passed in the stool by adult worms is two weeks for Toxacara canis(the dog roundworm) and five to eleven weeks for Toxascaris leonina(the cat roundworm. The shorter period is the result of paratenic hosts, such as rodents. We will talk more of these hosts later.  

          The most important form of transmission of T. canis finds larval forms of this parasite being passed to puppies while they are still in the uterus. Larval forms which have encysted in the mother lie “dormant” until she becomes pregnant. These cyst forms then become activated and migrate into the lungs of yet unborn puppies, where they go through further development that we saw above in the larva that developed from swallowed eggs. Interestingly, these reactivated larvae can also migrate to the intestine of the mother and mature there.  The cat roundworm, Toxacara mystax, does not exhibit this form of infection.

           A third form of transmission of this parasite is transmammary. The larval forms which have activated as in the previous scenario also migrate into the mammary tissue and are passed in the mothers’ milk, still another devious means that a parasite can use to keep its home. This, by the way, is the primary mode of transmission for the feline roundworm Toxacara mystax, but not for Toxascaris leonina.

          Lastly, we have a minor form of transmission by what is called a paratenic host. This host is not a normal part of the life cycle of a particular parasite, but ingests or otherwise carries the eggs or larvae of a parasite and spreads them when he is eaten by a host specific for that parasite. An example of this would be an earthworm ingesting soil contaminated with the eggs of the dog roundworm.

          Clinical signs of dog roundworm infestation can vary from no signs at all, especially in the adult dog, to signs of unthriftiness, weight loss, diarrhea, vomiting, and respiratory symptoms such as coughing and pneumonia from migrating larvae.

          About 45 years ago roundworms of the dog were discovered to cause human disease.  The Centers for Disease Control and Prevention (CDC) estimates this infection in humans causes approximately 750 cases of blindness per year and hundreds more less permanent forms of illness as well.  These are usually in children.  As we have mentioned earlier, children are close to the ground and dirt where the eggs of these worms are hiding and children will be more likely to touch the areas on pets which may contain these eggs such as the mouth or near the anus. We have all seen dogs licking the faces of children and I dare say many adults. Dogs commonly lick and share the food of humans in the house. All this remembering that a dog’s washcloth is his tongue.

          What problems do roundworms cause in humans?  Many species of animals such as the pig, dog, cat, horse, and human have species of roundworms which are specific to them. When the roundworm larva or egg enters the body of a creature for which it is not specific, it does not mature in the normal manner which we described above. Instead, for some reason it migrates aimlessly in the body instead of the standard path through the liver, heart, lungs and into the intestine. One place these wandering larvae commonly end up is the retina of the eye. Many children had their eyes surgically removed years ago because they were thought to have a form of eye cancer called a retinoblastoma.  When these eyes were removed and examined microscopically by pathologists, they were found not to be cancerous, but to contain cysts of roundworm larvae which had migrated to the eye.

          These roundworm larvae also like to end up in the brain. The roundworm of raccoons, Baylisascaris procyonis, which probably all raccoons have, seem to have the brain as the end organ to which they especially like to migrate.

          The hookworm is another commonly found nematode (the name for the roundworm family), also one of the most common intestinal parasites in dogs and cats. They are found throughout North America, even in dry sunny southern California, although they are much more common in areas of high temperature and humidity such as the Southeastern United States.

          The adult worms live in the small intestine where they attach themselves and feed on the host’s blood by means of saw tooth like plates. Hookworms’ saliva contains an anticoagulant so that blood at the site at which the worm attaches does not clot. Thus, common symptoms of hookworms are black tarry or bloody stools, and if the infection goes on long enough, weakness and pale gums from anemia.

          Adult worms lay eggs which are passed in the feces. In one to three weeks they hatch and form larvae. These larvae live in moist grass or dirt, wait for a host to come along and ingest them. When they are ingested, they will go directly to the intestine to develop or may first migrate throughout the tissues of the body and ultimately to the trachea, where they are coughed up and swallowed, also ending up in the intestine, where they will develop into adult worms. These infectious larvae will hop onto an available host and migrate to the intestines via the lungs and trachea as before by first burrowing through the skin.

          Fortunately, each species has its own specific type of hookworm, including man, dogs and cats. But like roundworm larvae of the dog which can migrate aimlessly throughout the human body, hookworm larvae of the dog and cat can, without ultimately causing intestinal disease, migrate aimlessly in the skin. This causes winding tortuous skin rashes called cutaneous larval migrans or creeping eruption. There have also been a few cases of intestinal disease in humans which have been found to be caused by immature dog hookworms both in the United States and Australia. Symptoms in the human patients were abdominal pain, diarrhea, abdominal distension, weight loss, and rectal bleeding. All the hookworms found in these cases, were found in the lower gastrointestinal tract and were immature forms of the worm. Their removal led to prompt recovery of the patients.  In the United States two young children with eosinophilic enterocolitis associated with hookworms have been reported.

          Now let’s go on to the smaller parasites, the one celled organisms called protozoa. First let’s look at a one celled parasite called Giardia.  These one celled organisms are, as we mentioned in the scientific studies studied above, found through out the world in many species, including man, dogs, cats, livestock and most species of wild animals. The infective stage of this organism, called an oocyst, is passed in the stools of infected humans or animals, and can be found everywhere from drinking water (chlorinated water is not sufficient to kill these parasites) to the most pristine mountain stream. They are so infectious that the ingestion only one oocysts can cause infection. Once ingested, the oocyst develops into the mobile tadpole-like feeding phase of this organism called a trophozoite. This form of the organism contains a sucker-like disc by which it attaches to the cells which line the intestines. These organisms proliferate so much that they prevent the host from absorbing digested nutrients.  These unabsorbed nutrients along with the physical presence of the organism, cause light colored, greasy diarrhea.

          Another one of those emerging diseases is an intestinal condition caused by an organism called Cryptosporidium. It is a one celled parasite that has gained much attention in the last 20 years. The first known case of the disease was in a three year old girl from rural Tennessee who suffered severe gastroenteritis (stomach and intestinal inflammation causing nausea, vomiting, abdominal cramps, fever, weight loss, and diarrhea). Illness is more severe in immune compromised persons such as AIDS patients and those taking immune suppressants for organ transplants, where the disease can become pulmonary as well as intestinal. It gained even more attention in the 1980’s when it was noted that cryptosporidium infections were very common in individuals with weak immune systems.  This discovery showed that cryptosporidium was a ubiquitous pathogen----it’s everywhere, that is, worldwide in its distribution.

          This organism can be transmitted via water contaminated with feces (it is not killed by chlorination of drinking water), animal to person contact and person to person contact.  Cryptosporidium, unlike many other intestinal parasites, can infect a number of different hosts. While it has been found in seventy nine different species, it is most commonly found in man, cattle, birds, cats, dogs (especially kittens and puppies that are immune compromised due to other disease and parasites), and mice. The avian and mouse varieties are incapable of infecting humans. It has recently shown that cats have their own species specific or species adapted type of cryptosporidium.

          This organism produces infectious cells called oocysts, which are ingested by the host, grow in the lining or surface cells of the intestine, proliferates in and severely damages these cells, and when the lining cells rupture, a new crop of infective oocysts are passed in the feces of the infected host.

          This organism is very infectious. Its size is only one half that of a red blood cell, but it can cause infection from the ingestion of as little as 10 organisms. As we mentioned earlier, animal to person transmission is possible. The organism is present in upwards of 90% of dairy farms and is passed primarily from calves who, because of their immature immune systems become infected and pass infective oocysts.  This type of infection is unusual in dogs and more common but still unusual in the housecat. Household pet to human transmission is considerably less, probably rare, though possible.

IV    Parasite Prevalence or Are They Everywhere?

          In the last chapter, we mentioned several studies done at universities that quoted the prevalence or percentage of parasites in pets in a given population. In those cases these were animals that had entered university veterinary clinics. Figures for percentages of pets with parasites in a given area can be misleading and will vary somewhat from study to study for the following reasons: 1) populations studied are different. Pets studied at universities are usually there by referral from other veterinarians, are from private hones, and thus have usually already been exposed to deworming programs. The prevalence of this group will probably be different from animals coming from a humane shelter or dog pound.

2) Results of various studies differ because different testing methods have been used. In a study done at the Atlanta, Georgia animal shelter, nearly 100% of dogs 7 weeks to 3 months of age were infected with Toxacara (Roundworms). Eighty percent of dogs six weeks of age or younger had roundworms in their intestines, but upon stool examination using the flotation methods used in most veterinary hospitals, only 20% of this less than six week group were positive for roundworms.  This is partially due to the accuracy of the flotation test, and the fact that these dogs were very young, and their roundworm parasites were not all producing eggs yet. Eggs, you might remember, are what we are looking for in the fecal flotation tests. Test results may also vary because stool samples taken are too small. That is, insufficient amounts of fecal sample are taken.  Some parasite studies are best done on stool samples taken from the patient on four consecutive days.

          One study, done nationally on dogs from shelters in the United States, utilized a fecal test which first centrifuged the stool sample to concentrate the eggs, followed by the fecal flotation test as done by most veterinary clinics in the United States. The number of dogs was over six thousand. This study found that 36% of dogs sampled when the United States as a whole was considered, harbored Toxacara (roundworms), Ancylostoma (hookworms), and whipworms (worms found in the cecum ,an appendix-like structure in the intestine). This number jumped to 52% in the Southeast when individual regions were considered.

          Remember those one celled guys we mentioned earlier called Giardia, Cryptosporidium, and Amoebas? In a word they are indeed everywhere. They have a worldwide distribution (found in just about every country in the world). If you remember they have a direct or simple life cycle. Many of the parasitic worms you may remember need to go through multiple hosts or enter the body by unusual routes. Not our one celled friends. These parasites are found in the intestine, shed in the feces, and therefore are readily picked up by anyone or anything (they also infect many species other than man, dogs, and cats) from anyone or anything contaminated with these microscopic organisms, or from stools containing them, including and especially water. For instance, there virtually is no pristine mountain stream in North America that does not contain them as I found out when I contracted Giardia in the Gila wilderness of New Mexico twenty years ago.

Two great websites to visit for a description of these parasites are:

http://wlapwww.gov.bc.ca/wat/wq/reference/protzoans.html

http://www. cdc.gov