Parasites - Questions & Answers Part 1

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).
  
  Giardia duodenalis: (formerly called G. lamblia)
  Giardia duodenalis, cause of giardiasis (GEE-are-DYE-uh-sis), is a one-celled, microscopic parasite that can live in the intestines of animals and people. It is found in every region throughout the world and has become recognized as one of the most common causes of waterborne (and occasionally foodborne) illness.

How do people get giardiasis?

• People get giardiasis the following ways:
  
  By consuming food or water contaminated with G. duodenalis cysts (the infective stage of the organism).
  
  By putting anything into your mouth that has touched the stool of a person or animal with giardiasis.
  
  Symptoms of giardiasis: Diarrhea, abdominal cramps, and nausea are the most common symptoms. Some cases may be without symptoms.

When will symptoms appear? What is the duration?

• Symptoms will usually appear 1 to 2 weeks after ingestion of a G. duodenalis cyst. They may last 4 to 6 weeks in otherwise healthy persons, but there are cases of chronic illnesses lasting months or even years.

Who is at risk for contracting giardiasis?

• Those at risk include: persons working in child daycare centers and children attending daycare centers; international travelers (traveler’s diarrhea);
  hikers, campers, or any other persons who may drink from untreated water supplies; and
  persons with weakened immune systems including those with HIV/AIDS infection, organ transplant recipients, or those individuals undergoing chemotherapy.
  
  How to prevent giardiasis: Wash hands with hot, soapy water before handling foods and eating, and after using the toilet, diapering young children, and handling animals.
  
  Make sure infected individuals wash their hands frequently to reduce the spread of infection.
  Drink water only from treated municipal water supplies.
  
  When hiking, camping, or traveling to countries where the water supply may be unsafe to drink, either avoid drinking the water or boil it for 1 minute to kill the parasite. Drinking bottled beverages or hot coffee and tea are safe alternatives.
  
  Do not swallow water while swimming.
  
  Do not swim in community pools if you or your child has giardiasis.
  
  Drink only pasteurized milk, juices, or cider.
  
  Wash, peel, or cook raw fruits and vegetables before eating.
  
  Do not use untreated manure to fertilize fruits and vegetables.

Cryptosporidium parvum: Cryptosporidium parvum, cause of the disease cryptosporidiosis (KRIP-toe-spo-RID-e-O-sis), is a one-celled, microscopic parasite, and a significant cause of waterborne illness worldwide. It is found in the intestines of many herd animals including cows, sheep, goats, deer, and elk.

How do people get cryptosporidiosis?

• People get cryptosporidiosis the following ways:
  
  By consuming food or water contaminated with C. parvum oocysts (infective stage of the parasite). The oocysts are the environmentally resistant stage of the organism and are shed in the feces of a host (human or animal).
  
  By putting anything into your mouth that has touched the stool of a person or animal with cryptosporidiosis
  
  Symptoms of cryptosporidiosis: Symptoms include watery diarrhea, stomach cramps, upset stomach, and slight fever. Some cases may be without symptoms.

When will symptoms appear? What is the duration?

• Symptoms appear 2 to 10 days after ingestion of C. parvum oocysts. The illness usually goes away without medical intervention in 3 to 4 days, but in some outbreaks in daycare centers, diarrhea has lasted 1 to 4 weeks. In people with AIDS and other individuals with weakened immune systems, cryptosporidiosis can be serious, long-lasting, and sometimes fatal.

Who is at risk for contracting cryptosporidiosis?

• Those at risk include: persons working in child daycare centers and children attending daycare centers;
  
  persons with weakened immune systems including those with HIV/AIDS infection, organ transplant recipients, or those individuals undergoing chemotherapy;
  international travelers (traveler’s diarrhea); and
  hikers, campers, or any other persons who may drink from untreated water supplies.
  
• How to prevent cryptosporidiosis: Wash hands with hot, soapy water before handling foods and eating, and after using the toilet, diapering young children, and handling animals.
  
  Make sure infected individuals wash their hands frequently to reduce the spread of infection.
  Drink water only from treated municipal water supplies.
  
  When hiking, camping, or traveling to countries where the water supply may be unsafe to drink, either avoid drinking the water or boil it for 1 minute to kill the parasite. 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 has cryptosporidiosis.
  
• Drink only pasteurized milk, juices, or cider.
  
• Wash, peel, or cook raw fruits and vegetables before eating.
  
• Do not use untreated manure to fertilize fruits and vegetables.

Cyclospora cayetanensis: Cyclospora cayetanensis (SIGH-clo-SPOR-uh KYE-uh-tuh-NEN-sis), cause of cyclosporiasis, is a one-celled, microscopic parasite. Currently little is known about this organism, although cases of cyclosporiasis are being reported from various countries with increasing frequency.

How do people get cyclosporiasis?

• People get cyclosporiasis the following ways: By consuming food or water contaminated with C. cayetanensis oocysts (the infective stage of the organism).
  By putting anything into your mouth that has touched the stool of a person or animal with cyclosporiasis.
  
  Symptoms of cyclosporiasis: Symptoms include watery diarrhea (sometimes explosive), stomach cramps, nausea, vomiting, muscle aches, low-grade fever, and fatigue. Some cases are without symptoms. Symptoms are more severe in persons with weakened immune systems.
  
  When will symptoms appear? What is the duration? Symptoms typically appear about 1 week after ingestion of C. cayetanensis oocysts. If untreated, the symptoms may last a week to more than a month. Symptoms may return.

Who is at risk for contracting cyclosporiasis?

• Persons of all ages are at risk for infection. Persons with weakened immune systems including those with HIV/AIDS infection, organ transplant recipients, or those individuals undergoing chemotherapy may be at greater risk for infection.
  
  How to prevent cyclosporiasis: Wash hands with hot, soapy water before handling foods and eating, and after using the toilet, diapering young children, and handling animals.
  
  Make sure infected individuals wash their hands frequently to reduce the spread of infection.
  Drink water only from treated municipal water supplies.
  
  When hiking, camping, or traveling to countries where the water supply may be unsafe to drink, either avoid drinking the water or boil the water for 1 minute to kill the parasite. 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 has cyclosporiasis.
• Wash, peel, or cook raw fruits and vegetables before eating.
• Do not use untreated manure to fertilize fruits and vegetables.

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