Just the thought of parasites can make your skin crawl. These uninvited passengers burrow, hook and hunker down to feast on the blood and body of unsuspecting hosts. However, some host-parasite relationships can be mutually beneficial: The bacteria living quietly in our gut help us with digestion and immune function.
But not all parasitic relationships are love affairs, and although many people think parasites only affect those in underdeveloped countries, infection and disease is common everywhere, even in places where sanitation, personal hygiene and safe food-handling practices are routine.
When it comes to human disease there are 3 types of parasites that feast at the human table.
- Protozoa - one-celled organisms that live and multiply in the blood or tissue of humans. They infect the body via mosquitoes and flies, and are found in soil and water.
- Helminths - parasitic flatworms, flukes, tapeworms, thorny-headed worms, roundworms and pinworms. They live in the gastrointestinal tract, blood, lymphatic system and other tissues.
- Ectoparasites - ticks, fleas, lice, and mites that live on the surface of a human host and attach or burrow into the skin.
There are a host of parasitic infections that cause disease in humans. The effect can range from mildly annoying to life threatening. Malaria is the most prevalent parasitic disease worldwide killing more than 1 million people each year, while trichomoniasis, a common vaginal infection, is the most common parasitic infection in the US.
Here are some parasitic diseases found on our doorstep.
Ascariasis (roundworm) - The eggs produced by roundworms living in soil are transmitted to humans when they are swallowed. The eggs hatch into worms in the intestines, that cause pain and vomiting, and can also travel through the bloodstream to the lungs to cause wheezing and coughing. The eggs can be transmitted via human feces found in fields, streets, and back yards.
Pediculosis (lice) - Lice can infect the human head, body and pubic hair. They are spread by close contact with another infected person or contaminated furniture or clothing.
Giardiasis (giardia) - Giardiasis comes from drinking or coming into contact with water, feces (human and animal), food, hands or objects contaminated with the giardia larvae. It causes diarrhea, abdominal cramps, greasy stools, dehydration and weight loss.
Trichomoniasis (trich) -The trichomonas parasite is a sexually transmitted disease that infects the vagina and urogential tract.
Cryptosporidiosis (crypto) - A protozoa that infects the gastrointestinal tract causing life-threatening diarrhea, particularly in immunocompromised people.
Toxoplasmosis - Is primarily transmitted when infected undercooked meat is eaten. It also infects domestic cats, who can release eggs in their feces to later infect their human caretakers. The parasite does not become infectious until 1 to 5 days after it is shed in a cat's feces. It can cause mild aches and pains and severe damage to the brain, eyes, or other organs.
Scabies (mites) - Mites burrow into the upper layer of the skin to lay eggs. The pimple-like "S-shaped" rash is intensely itchy. It is easily contracted through skin-to-skin contact with an infected person and can be acquired during sexual encounters.
Enterobiasis (pinworm) - Is cause by a roundworm (nematode) and infects the colon and rectum. Female pinworms crawl out of the intestines through the anus and deposit their eggs on the surrounding skin, usually when a person is sleeping. The eggs are transferred to the mouth of a new host from hands that have come in contact with egg-contaminated food, clothing or bedding where they can survive for 2 to 3 weeks.
Besides the obvious - avoiding direct contact with an infected person or contaminated items - there are some effective weapons for keeping parasitic diseases out of range.
- Don't drink water or use ice made from lakes, rivers, springs, streams or poorly monitored or maintained wells
- Avoid swallowing recreational water in swimming pools, water parks, hot tubs, spas and fountains
- Do not swim if you are infected or are experiencing diarrhea to protect others
- Pay attention to public health department water advisories and do not drink untreated tap water during community-wide outbreaks of disease
- Heat water to a rolling boil for at least 1 minute or use a NSF-rated filter that has an absolute pore size of 1 micron or smaller if water potability is uncertain
- Use uncontaminated water to wash all food that is to be eaten raw, or peel them
- Avoid drinking unpasteurized milk or dairy products
- Avoid eating food from street vendors
- Cook beef, lamb, veal roasts and steaks to 145degF; pork, ground meat, and wild game to 160degF, and poultry to 180degF in the thigh (can also freeze meat for a few weeks)
- Do not taste meat until it is fully cooked
- Wash hands thoroughly and frequently with soap and water especially after using the toilet, before handling or eating food and before and after every diaper change
- Wear gloves when doing gardening or working in soil and sand
- Keep fingernails clean and short and avoid biting nails
- Avoid scratching the skin in the anal area
- Clean anything that may be contaminated with feces such as bathroom fixtures, changing tables, diaper pails and toys regularly
- Wash cutting boards, dishes, counters, utensils, and hands with hot soapy water after contact with raw meat, poultry, seafood, or unwashed fruits or vegetables
- Change litter boxes daily and avoid getting a new cat or cleaning a cat's litter box if you are pregnant