Emerging Diseases Lecture 10:

Parasite Diseases-on the Way Out or Making a Comeback?

10.1: Overview10.2: “Pork” Tapeworm

10.3: Guinea Worm Disease10.4: Parasites as Medicine?

10.5: Relevance10.6: Summary

10.1: Most Multicellular Parasitic Diseases Provide Examples of Gastrointestinal Transmission

• Internal parasitic infections frequently caused by animals that are classified as worms.

• The adult animals can be quite large.

• A heavy “worm load” debilitates the victim.

• These diseases have been known since antiquity.

Supposedly this child passed all of these parasites upon receiving worm-killing medicine. True story or legend? No one knows.

10.2: Pork Tapeworms Were Once Very Common

• Human infection named as a pig parasite• Very widespread infection in developing countries

but now rare in industrialized nations.• May be acquired through undercooked (measly) pork

or via unsanitary conditions.

Life Cycle of “Pork” Tapeworm

Humans are usually the primary or definitive host. Pigs are secondary or intermediate hosts

Then how did this happen?

Usually found where pigs live close to peopleWith poor sanitation

And pork is a dietary favorite

Neurocysticercosis in an Orthodox Jewish Community in New York City

Peter M. Schantz, V.M.D., Ph.D., Anne C. Moore, M.D., Ph.D., José L. Muñoz, M.D., Barry J. Hartman, M.D., John A. Schaefer, M.D., Alan M. Aron, M.D., Deborah Persaud, M.D., Elsa Sarti, M.D., Marianna Wilson, M.S., and Ana Flisser, D.Sc. N Engl J Med 1992; 327:692-695September 3, 1992DOI: 10.1056/NEJM199209033271004

3 Key points:

Primary host: host in which sexual reproduction of parasite occurs

Secondary host: parasite grows but does not sexually reproduce

Parasites can move back and forth between host species

10.3: Dracunculiasis is Another Parasite Disease

• Caused by another type of worm: roundworm.• Dracunculus medinensis: little dragons

because infection is so painful.• First described in antiquity• Once widespread-now restricted to some

regions of Africa• Named “Guinea Worm Disease” by explorers

from Europe

Life Cycle of DracunculusLarvae are theJuvenile formsOf the animal

AquaticCrustaceansAre theIntermediate Hosts.

Humans infected via contaminated water

Parasites reach Sexual maturityIn human host.

Grow to large size in body then crawl to surface

The exiting parasite has to be removed manually and carefully.

If the worm gets broken during removal severe burningand itching result.

Disease PreventionContaminated water can be treated to kill crustaceans-

Or just filtered through panty hose mesh.

Eradication of Another Disease?• Since 1986, The Carter Center has led the international

campaign to eradicate Guinea worm disease, working closely with ministries of health and local communities, the U.S. Centers for Disease Control and Prevention, the World Health Organization, UNICEF, and many others.

• Guinea worm disease is set to become the second human disease in history, after smallpox, to be eradicated. It will be the first parasitic disease to be eradicated and the first disease to be eradicated without the use of a vaccine or medicine.

• 148 cases reported in 2013• 126 in 2014• 15 in first half of 2015

Linkshttp://www.youtube.com/watch?

v=nu3z7mRyLRchttps://www.youtube.com/watch?

v=8nOuAUfXjzQhttps://www.youtube.com/watch?

v=u4kQWvUv_Ns

10.4: Parasites as Medicine?by Krissi Maarx, eHow Contributor The tapeworm, a parasite that lives in the intestine, can

grow up to 30 feet in length, according to the Merck Manual. Tapeworm infection in humans can cause diarrhea, abdominal pain and release of tapeworm egg sacs in excrement; but because it can also lead to weight loss, dieters purchase and ingest tapeworm cysts in an effort to shed extra pounds.

HistoryIn 2007, the Los Angeles Times reported that rumors of

tapeworm's weight loss power have persisted for a century and that druggists supposedly sold them in pill form during the 1910s. Tapeworm pills were sold and advertised throughout the early 20th century, but according to Snopes.com, there's no verifiable evidence that the pills actually contained tapeworms. The "poster girl" of the tapeworm diet, opera singer Maria Callas, supposedly lost 66 pounds from intentional ingestion of tapeworms, though it's more likely that she was infected from her love of eating raw meat.

Helminthic Therapy (worm therapy) Helminthic therapy, or less accurately worm therapy, is an idea derived

from the hygiene hypothesis. It is impossible to understand helminthic therapy without first understanding the hygiene hypothesis. What the hygiene hypothesis suggests us is that a lack of early childhood exposure to infectious agents and parasites increases susceptibility to allergic diseases by preventing the natural modulation of immune reactions.

Does deliberate infection with worms cause the immune system to calm down?

10.5: RelevanceWhy are you reading about worm diseases when they are so rare in

the United States?

Answer One: Watch “Monsters Inside Me” on Animal Planet and be careful when you travel.

Answer Two: See Next Slide

Raccoon Roundworm-an emerging disease in the US

Humans are intermediate hosts.The larvae are very stable in the environment.Humans may acquire disease from contact with raccoon feces or with contaminated materials orfrom other secondary hosts.Larvae cause serious symptoms or death in intermediate hosts.

Your pets can be carriers.

10.6: Summary:Pathogens that cause parasitic

diseases (e.g. worms) have complex life cycles that include

alternate hosts. They can be dangerous to humans!