Parasites - Part 1

                             

What are parasites?

The word “parasite” was first used in English in 1539. It comes from the Medieval French word parasite and from the Latin parasites and greek parasitos “one who eats at the table of another”. A parasite is an organism that lives on or in a host organism and gets its food from or at the expense of its host. Are parasites something new?

People have known about parasites such as roundworms and tapeworms since ancient Egypt, Greece and Rome. In 1668, Francesco Redi was the first to recognize and correctly describe details of about 180 internal and external parasites including sheep liver fluke and ticks. Up until the end of the 1950’s it was commonplace to give children “worm powder" to clear their body from parasites.

How do humans get parasites?

Parasite infections are an insidious and underestimated health problem, affecting millions of people worldwide. In fact, estimates report that at least half the world’s population has some type of worm infection. (1) Many of the world’s most deadly parasites exist in tropical and subtropical climates and under-developed countries, in unclean water that people either drink, bathe in or consume raw foods that have been washed in it. 

In North America it is estimated that at least 50 million of us are harbouring parasites in their systems right now.

Without a host, a parasite cannot live, grow and multiply. For this reason, a parasite rarely kills the host, but it can spread diseases, some of which may be fatal. We get parasites from some unexpected sources such as:

Raw or undercooked foods 

Some parasites are blood-born or live in faeces and can be transmitted by food service workers using unsanitary food handling practices, such as working with a cut finger or not washing their hands after using the bathroom. 

Pork 

It contains a variety of parasites, including the protozoa, Toxoplasma gondii and Sarcocystis, and the helminths Trichinella and Taenia. Only consume fully cooked pork. 

Certain types of fish

Saltwater and freshwater fish such as cod, swordfish, trout, pike, and salmon can contain parasites such as roundworm or tapeworm larvae. Therefore, fish should always be consumed fully cooked. (2)

Unclean water 

Do not swallow water from swimming in lakes, ponds or rivers.

Pets

Pets transmit parasites to humans via direct contact.

Insects

Fleas, ticks, lice, and mites can transmit parasites to humans through biting, burrowing, or bloodsucking.

Blood transfusions 

As per the Centers for Disease Control, donated blood is not screened for all types of parasites, so, parasitic infections can be transmitted via transfusions. (3) 

Soil 

Protozoa and (more commonly) helminths like pinworms, can be transmitted via contact with the soil.

Sexual contact

Trichomoniasis, for example, is a prevalent STD caused by the protozoan parasite: Trichomonas vaginalis. According to the CDC, approximately 3.7 million Americans are infected with “Trich,” and may not realize it. (4) 

Contact with faecal matter 

Daycare or healthcare workers can pick up faecal-borne parasites if they’re not taking the proper precautions.

Do all parasites make us sick?

In a word, no. For example, Tiny mites called skin mites, live on almost all humans and mate on our skin. They are a fraction of a millimetre long and are found in the hair follicles on the face and nipples. The mites, called Demodex folliculorum, feed on sebum, a substance that coats the skin which is naturally released by cells inside our pores. At night, they leave their hiding place to mate on our foreheads, ear canal, wings of our noses and nipples while we sleep

 

Around 90 per cent of humans have these mites living on them, and they are passed on at birth. They’re usually harmless and go unnoticed, but in large numbers they may irritate the skin, make it flaky and cause redness and itchiness. Scientists who research these mites are saying that they may be evolving from parasites who extract nutrients at our expense, to creatures that share a symbiotic, or mutually beneficial relationship with us. Apparently, they keep pores in our face unplugged and help keep our faces healthy.

On the other side, however, parasitic infections cause a tremendous burden of disease in both the tropics and subtropics as well as in more temperate climates. Of all parasitic diseases, malaria, with about 200 million cases per year, causes the most deaths globally, killing more than 400,000 people each year, most of them young children in sub-Saharan Africa. Thankfully, just like with bacteria and other pathogens not everyone who is exposed to a parasite or even consumes a parasite, will develop an infection because of the variable states of everyone’s immune system. A staggering number of people in developed and underdeveloped countries are living with compromised immune systems. This may take the form of digestive health issues, autoimmune disease, malnutrition, and other chronic conditions. A compromised immune system is a desirable parasite home.

Which type of parasites do we want to avoid?

The three main classes of parasites that can cause disease in humans are protozoa, helminths, and ectoparasites. 

Protozoa are microscopic, one-celled organisms that can be free-living or parasitic in nature. They are able to multiply in humans, which contributes to their survival and also permits serious infections to develop from just a single organism. Transmission of protozoa that live in a human’s intestine to another human typically occurs through a faecal-oral route (for example, contaminated food or water or person-to-person contact). Protozoa that live in the blood or tissue of humans are transmitted to other humans by an arthropod vector (for example, through the bite of a mosquito or sand fly).

The protozoa that are infectious to humans can be classified into four groups based on their mode of movement:

• Sarcodina – the amoeba, e.g., Entamoeba
• Mastigophora – the flagellates, e.g., Giardia, Leishmania 
• Ciliophora – the ciliates, e.g., Balantidium 
• Sporozoa – organisms whose adult stage is not motile e.g., Plasmodium (malaria), Cryptosporidium 

Helminths are large, multicellular organisms that are generally visible to the naked eye in their adult stages. Like protozoa, helminths can be either free-living or parasitic in nature. In their adult form, helminths cannot multiply in humans. There are three main groups of helminths (derived from the Greek word for worms) that are human parasites:

• Flatworms (platyhelminths) – these include the trematodes (flukes) and cestodes (tapeworms).
• Thorny-headed worms (acanthocephalins) – adult forms of these worms reside in the gastrointestinal tract. 
• Roundworms (nematodes) – adult forms of these worms can reside in the gastrointestinal tract, blood, lymphatic system or subcutaneous tissues. Alternatively, the immature (larval) states can cause disease through their infection of various body tissues. Some consider the helminths to also include the segmented worms (annelids)—the only ones important medically are the leeches. Of note, these organisms are not typically considered parasites.

Ectoparasites can broadly include blood-sucking arthropods such as mosquitoes (because they are dependent on a blood meal from a human host for their survival), this term is generally used more narrowly to refer to organisms such as ticks, fleas, lice, and mites that attach or burrow into the skin and remain there for relatively long periods of time (e.g., weeks to months). Arthropods are important in causing diseases in their own right, but are even more important as vectors, or transmitters, of many different pathogens that in turn cause tremendous morbidity and mortality from the diseases they cause.

 Who are the top 10 parasites to look out for in North America?     

                                                    

1. Bed Bugs

Furniture, wallpaper, mattresses, and clutter provide nesting spots for these small, flat insects. They like to live near people or pets, and they come out while you’re asleep to feed on your blood. Bedbugs don’t cause disease, but you might have an allergic reaction to their bite. If you scratch too much, the bitten area could get infected. Use antiseptic creams or lotions, or take an antihistamine, to ease the itch.  

2. Lice

These insects live on your blood. There are three types: head, body, and pubic. Only body lice spread diseases. Since they crawl, you can get lice through close contact with someone. They lay eggs on you, and the itching starts when they hatch. You can treat them with over-the-counter and prescription medications and shampoos.

3. Scabies Mite 

A relative of the tick that digs into your body and lays eggs causes this condition. You get it from skin-to-skin contact with an infected person. Symptoms include itching at night, a pimply rash, sores, and crusty patches. You can treat it with a prescription medicine that kills the mites called scabicide.

4. Pork Tapeworm 

You can get these bugs from eating raw or undercooked pork. Both people and pigs carry them, but they’re spread when you swallow the eggs from tainted food and water. You can also get them if you come in contact with the faeces of someone who has them. They infect the intestines and brain, which can lead to a disease that causes headaches and seizures, called cysticercosis. Some people get better without treatment. Others need medication or surgery.

5. Roundworms        

       

        

 

Common diseases from roundworms/nematodes and their symptoms include:

• Ascariasis -- belly pain
  •   Hookworm -- blood loss, abdominal pain
  •   Pinworm -- anal itching
  •   Trichinosis -- (Trichinella Spiralis) pain, fever, face swelling, pink eye, rash
  •   Whipworm -- mucus, water and blood in stool, rectal prolapse
• Tapeworm — nausea, vomiting, diarrhea, dizziness, belly inflammation-survives up to 25 years in humans
• Strongyloides/Threadworm — abdominal pain, sometimes kidney and heart problems (can be life-     threatening to those who are taking corticosteroids or immune-suppressive medications)

6. Giardia Iamblia 

If you’ve ever been camping and you came down with diarrhea, gas, stomach cramps, bloating, and nausea, you’ve likely caught this bug. You get it through food or drinking water, or from contact with the faeces of an infected person or animal. The illness can be treated with prescription drugs.

7. Ticks 

Ticks are parasites that feed on warm-blooded hosts by biting them. A tick bite can infect humans and animals with bacteria, viruses and protozoans (organisms made up of one cell) that can cause diseases. Some of these conditions can be very serious and may include Lyme disease, Tularemia, Ehrlichiosis (can be fatal), Rocky Mountain spotted fever (life-threatening), Anaplasmosis and Tick paralysis. Ticks are typically small and difficult to see until they have been attached for some time. A tick will feed until it becomes full and then fall off. This usually takes anywhere from three to six days. 

8. Entamoeba Histolytica 

This single-celled organism predominantly infects humans and other primates causing a disease called amoebiasis. It can be found in water, damp environments and in soil, and can contaminate fruits and vegetables. It spreads through faecal contamination. Other than the malarial parasite, it causes more deaths than any other protozoan.
Symptoms: abdominal pain, weight loss, weakness, diarrhoea, liver abscess

9.  Trichomonas Vaginalis 

This parasite causes a sexually transmitted disease called trichomoniasis, the most common curable STD. Most infected people don’t have any symptoms, but some may notice itching, burning, or irritation of their penis or vagina. It’s treated with antibiotics.

10. Toxoplasma Gondii 

This crescent-shaped bug makes its home in meat, water, and infected cat faeces. It causes an illness called toxoplasmosis, which can feel like the flu. Pregnant women and people with weak immune systems can have serious symptoms as it invades the central nervous system, as cysts in the muscles, brain, and eyes. Usually untreated, a doctor can decide to prescribe medication if the case is severe.

 

Just to let you know… we, North Americans, are actually fortunate, because in Southeast Asia, there is a brain-eating amoeba known as N. fowleri, that lives in warm freshwater and enters the body through the nose. It causes a condition that destroys brain tissue called primary amoebic meningoencephalitis.  Symptoms include headache, fever, vomiting, confusion, stiff neck, seizures,  and loss of balance. Only experimental treatments are available now, so the survival rate is low.

Are fungi parasitic?

We tend to think that fungus is not dangerous and couldn’t kill us because there are so many good ones that we eat and that we take as medicine. However, fungal infection (mycosis) is widespread in animals including humans; it kills some 1.6 million people each year.

The fungus kingdom includes all those organisms that are known as mushrooms, yeasts and moulds. Fungi are either saprophytic (they feed on dead plant and animal material), parasitic (they feed off a living host) or symbiotic (they share a mutually beneficial relationship with another organism). Saprophytic fungi release enzymes to soften the dead plant or animal. Fungi of the genus Aspergillus or Candida albicans carry infections to humans.

About one hundred of the thousands of known species of fungi are pathogenic to man, causing infections that are called mycoses. A large part of mycoses is transmitted through inhalation, ingestion or the infection of skin wounds and attacks the skin, hairs, nails and mucosa. When inhaled, the spores of the genus Aspergillus transmit a serious lung infection, Aspergillosis, while the mycoses of the skin, hairs and nails are called Tineas (e.g., ringworm). The mouth, the digestive and the reproductive systems can be infected by the genus Candida albicans; in new-born children, this infection is called thrush and causes white patches on the mouth mucosa.

Ergot is a type of fungus (Claviceps purpurea) that grows on grains such as rye and wheat and produces toxic alkaloids. As it grows, it replaces individual kernels of grain with dark hard “ergots” which contaminate the grain. Ergot can affect the nervous system (dizziness, headaches, convulsions, psychosis and coma), digestive system (nausea, vomiting, abdominal pain, cramping and diarrhea) and the cardiovascular system (vasospasm in arteries to the kidneys, neck, retina and heart, legs and feet), constricting blood vessels which can lead to gangrene.

For parasitic infection symptoms, treatments and food tips, check out Parasites Part 2.