Parasites - Questions & Answers Part 2

What are parasites?

• Parasites are organisms that derive nourishment and protection from other living organisms known as hosts. They may be transmitted from animals to humans, from humans to humans, or from humans to animals. Several parasites have emerged as significant causes of foodborne and waterborne disease. These organisms live and reproduce within the tissues and organs of infected human and animal hosts, and are often excreted in feces.

How are they transmitted?

• They may be transmitted from host to host through consumption of contaminated food and water, or by putting anything into your mouth that has touched the stool (feces) of an infected person or animal.

How do they vary?

• Parasites are of different types and range in size from tiny, single-celled, microscopic organisms (protozoa) to larger, multi-cellular worms (helminths) that may be seen without a microscope.

What are some common parasites?

• Some common parasites are Giardia duodenalis, Cryptosporidium parvum, Cyclospora cayetanensis, Toxoplasma gondii, Trichinella spiralis, Taenia saginata (beef tapeworm), and Taenia solium (pork tapeworm).
  
  Toxoplasma gondii: Toxoplasma gondii, cause of the disease, toxoplasmosis (TOX-o-plaz-MO-sis), is a single-celled, microscopic parasite found throughout the world. It is interesting to note that these organisms can only carry out their reproductive cycle within members of the cat family. In this parasite-host relationship, the cat is the definitive host. The infective stage (oocyst) develops in the gut of the cat. The oocysts are then shed into the environment with cat feces.

How do people get toxoplasmosis?

• People get toxoplasmosis the following ways: By consuming foods (such as raw or undercooked meats, especially pork, lamb, or wild game) or drinking untreated water (from rivers or ponds) that may contain the parasite.
  
  Fecal-oral: Touching your hands to your mouth after gardening, handling cats, cleaning a cat’s litter box, or anything that has come into contact with cat feces.
  
  Mother-to-fetus (if mother is pregnant when first infected with T. gondii).
  Through organ transplants or blood transfusions, although these modes are rare.
  
  Symptoms of toxoplasmosis and severe toxoplasmosis: Toxoplasmosis is relatively harmless to most people, although some may develop "flu-like" symptoms such as swollen lymph glands and/or muscle aches and pains. In otherwise healthy individuals, the disease is usually mild and goes away without medical treatment. However, dormant tissue stages can remain in the infected individual for life.
  
  However, persons with weakened immune systems such as those with HIV/AIDS infection, organ transplant recipients, individuals undergoing chemotherapy, and infants may develop severe toxoplasmosis. Severe toxoplasmosis may result in damage to the eyes or brain. Infants becoming infected before birth can be born retarded or with other mental or physical problems.

When will symptoms appear? What is the duration?

• The time that symptoms appear varies, but generally symptoms will appear 1 week to 1 month after consuming the parasite.
  
  The duration of the illness depends on the health and immune status of the host. Persons with weakened immune systems may experience illnesses of long duration, possibly resulting in death.

Who is at risk for contracting severe toxoplasmosis?

• Those at risk include: Persons with weakened immune systems including those with HIV/AIDS infection, organ transplant recipients, or those individuals undergoing chemotherapy.
  
  Infants born to mothers who become infected with T. gondii shortly before becoming pregnant or during pregnancy. Those mothers exposed to T. gondii longer than 6 months before becoming pregnant rarely transmit toxoplasmosis to their infants.
  
  How to prevent toxoplasmosis: If you are pregnant or if you have a weakened immune system, you should discuss your risk of contracting toxoplasmosis with your health care provider.
  
  Wear clean latex gloves when handling raw meats, or have someone who is healthy, and not pregnant, handle the meats for you.
  
  Cook all meats thoroughly to 160 °F.
  
  Wash hands, cutting boards, and other utensils thoroughly with hot, soapy water after handling raw meats.
  
  Clean cat litter boxes daily because cat feces more than a day old can contain mature parasites.
  Wash hands thoroughly with hot, soapy water after handling cats, cleaning and cat litter boxes, especially before you handle or eat food.
  
  Wear gloves when you handle garden soil or sandboxes. Cats may use gardens or sandboxes as litter boxes.
  
  Cover sandboxes to prevent cats from using them as litter boxes.
  
  Help prevent cats from becoming infected with T. gondii by discouraging them from hunting and scavenging.
  
  Feed cats commercially made cat foods or cook their food.
  
  Trichinella spiralis: Trichinella spiralis, cause of trichinosis (TRICK-a-NO-sis) is an intestinal roundworm whose larvae may migrate from the digestive tract and form cysts in various muscles of the body. Infections occur worldwide, but are most prevalent in regions where pork or wild game is consumed raw or undercooked. The incidence of trichinosis has declined in the United States due to changes in hog feeding practices. Presently, most cases in this country are caused by consumption of raw or undercooked wild game.

How do people get trichinosis?

• People get trichinosis by consuming raw or undercooked meats such as pork, wild boar, bear, bobcat, cougar, fox, wolf, dog, horse, seal, or walrus containing Trichinella larvae. The illness is not spread directly from person to person.
  
  Symptoms of trichinosis: The first symptoms are nausea, diarrhea, vomiting, fever, and abdominal pain, followed by headaches, eye swelling, aching joints and muscles, weakness, and itchy skin. In severe infections, persons may experience difficulty with coordination and have heart and breathing problems. Death may occur in severe cases.

When will symptoms appear? What is the duration?

• Abdominal symptoms may appear within 1 to 2 days after eating contaminated meat. Further symptoms (eye swelling and aching muscles and joints) may begin 2 to 8 weeks after infection. Mild cases may assumed to be flu.

Who is at risk for contracting trichinosis?

• Persons consuming raw or under cooked pork or wild game. Persons with weakened immune systems including those with HIV/AIDS infection, organ transplant recipients, or those individuals undergoing chemotherapy may be at a greater risk for infection.
  
  How to prevent trichinosis: Cook pork and wild game to 160 °F to kill any Trichinella larvae that may be present.
  
  Taenia saginata/Taenia solium (Tapeworms) Taenia saginata (beef tapeworm) and Taenia solium (pork tapeworm) are parasitic worms (helminths). Taeniasis is the name of the intestinal infection caused by adult-stage tapeworms (beef or pork tapeworms). Cysticercosis is the name of the tissue (other than intestinal) infection caused by the larval-stage of the pork tapeworm only.
  
  It is interesting to note that humans are the definitive hosts of both organisms. This means that the reproductive cycle, and thus egg production by the organisms, occurs only within humans. Eggs are passed in human feces and they may be shed into the environment for as long as the worms remain in the intestines (for as long as 30 years). In addition, the eggs may remain viable in the environment for many months.
  
  These diseases are more prevalent in underdeveloped countries where sanitation practices may be substandard and in areas where pork and beef are consumed raw or undercooked. They are relatively uncommon in the U.S., although travelers and immigrants are occasionally infected.

How do people get Taeniasis?

• People get Taeniasis by consuming infected beef or pork (raw or undercooked).
  
  Symptoms of Taeniasis: Most cases of infection with adult worms are without symptoms. Some persons may experience abdominal pain, weight loss, digestive disturbances, and possible intestinal obstruction. Irritation of the peri-anal area can occur, caused by worms or worm segments exiting the anus.

When will symptoms appear? What is the duration?

• T. saginata (beef tapeworm) infections appear within 10 to 14 weeks. T. solium (pork tapeworm) infections appear within 8 to 12 weeks.
  
  Taeniasis may last many years without medical treatment.

Who is at risk for contracting Taeniasis?

• Anyone consuming infected beef or pork (raw or undercooked).
  
  
  Persons with weakened immune systems including those with HIV/AIDS infection, organ transplant recipients, or those individuals undergoing chemotherapy may be at a greater risk for infection.
  
  How to prevent Taeniasis
  Cook beef and pork to 160 °F to kill encysted tapeworm larvae that may be present.

How do people get cysticercosis?

• People get cysticercosis the following ways:
  
  By consuming food or water contaminated with the eggs of T. solium (pork tapeworm). Worm eggs hatch and the larvae then migrate to various parts of the body and form cysts called cysticerci. This can be a serious or fatal disease if it involves organs such as the central nervous system, heart, or eyes.
  
  By putting anything into your mouth that has touched the stool of a person infected with T. solium.
  Some persons with intestinal tapeworms may infect themselves with eggs from their own feces as a result of poor personal hygiene.
  
  Symptoms of cysticercosis: Symptoms may vary depending on the organ or organ system involved. For example, an individual with cysticercocis involving the central nervous system (neurocysticercosis) may exhibit neurological symptoms such as psychiatric problems or epileptic seizures. Death is common.

When will symptoms appear? What is the duration?

• Symptoms usually appear from several weeks to several years after becoming infected with the eggs of the pork tapeworm (T. solium). Symptoms may last for many years if medical treatment is not received.

Who is at risk for contracting cysticercosis?

• Persons traveling to countries where sanitation may be substandard and the water supply may be unsafe.
  
  Persons with weakened immune systems including those with HIV/AIDS infection, organ transplant recipients, or those individuals undergoing chemotherapy may be at a greater risk for infection.
  
  How to prevent cysticercosis
  
• Drink water only from treated municipal water supplies.
  
• When traveling to countries where the water supply may be unsafe, either avoid the water or boil it for 1 minute to kill parasite eggs. Drinking bottled beverages or hot coffee and tea are safe alternatives.
  
• Do not swallow water while swimming.
  
• Do not swim in community swimming pools if you or your child are infected with tapeworms.
  
• Wash, peel, or cook raw fruits and vegetables before eating.
  
• Make sure that infected individuals wash their hands frequently to reduce the spread of infection.

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