{Infections Journal

We have discussed many types of infectious agents from bacteria to viruses to protists. Is there any other disease causing pathogens we have neglected to discuss?

Let’s check out some facts! More than 25% of the worlds population is suffering from

helminth infections Eggs are found in human fecal matter which can

contaminate soil in areas where sanitation is poor The greatest number of cases occur in sub-Saharan

Africa, the Americas, China and east Asia During the adult stage, this parasite bores itself into the

hosts’ intestines where it feeds and grows

CAN YOU GUESS WHAT HELMINTH MEANS?

Helminth parasites!

WORMS!!!

“Helminth” = “worm” Eukaryotic Multicelluar Invertebrates Bilateral symmetry w/ tube-like or flattened

bodies Triploblastic – 3 distinct

layers of cells

General Characteris

tics

3 Main Types:

Biodiversity

Nemathelminthes

(nematodes)

Platyhelminthes (flatworms) subdivided into the Cestoda (tapeworms)

and the Trematoda (flukes)

cestode trematode

Long, thin, unsegmented, tube-like bodies

Anterior mouths and longitudinal digestive tracts.

Nematodes

(roundworms)

Fluid-filled internal body cavity (pseudocoelum) acts as a hydrostatic skeleton providing

rigidity great and easy way to circulate nutrients

Nematodes (roundworms)

Adult worms form separate sexes with well-developed reproductive systems.

Nematodes (roundworms)

A Variety of Nematodes

(roundworms)

Nematode Infections! QUIZ

Nematoda:1. Ascaris2. Dracunculus3. Enterobius 4. Capillaria5. Trichuris6. Loa loa7. Wuchereria

Matching Choices:A. Endemic to the Phillipines B. The female sex of this organism can

make up to 20,000 eggs per day!C. Unlike most parasitic helminths, this

species is highly prevalent in temperate zones and developed countries.

D. The largest intestinal roundwormE. Passed on by the bite of a deer fly and

can be observed nestled in the eye tissue

F. Very careful to remove worm in its entirety … why?

G. This parasite infects the lymphatic system of the host and causes swelling of the lower limbs a disease commonly referred to as elephantasis.

Nematode Infections! QUIZ

Nematode Infections! QUIZ

Nematode Infections! QUIZ

Nematode Infections! QUIZ

WORMS!!!

3 Main Types:

Biodiversity

Nemathelminthes

(nematodes)

Platyhelminthes (flatworms) subdivided into the Cestoda (tapeworms)

and the Trematoda (flukes)

cestode trematode

Live in digestive tract Over 1,000 species have been described

Parasitize humans consumption of undercooked meat meat prepared in conditions of poor hygiene

Tape worm infecting humans can grow over 30ft long! T. saginata, the beef tapeworm, can grow up 65 ft! The whale tapeworm, Polygonoporus giganticus, can grow

100 ft!

Platyhelminthes: Cestoda

Tapeworms

SCOLEX1. Scolex (“head”): attaches to intestines of digestive host

Includes hooks or suckers (like suction cup) Most prominent feature but hard to identify

LACK DIGESTIVE TRACT! feed off of already digested food through absorption across body “skin”

PROGLOTTIDS2. Body plan composed of segments called proglottids (sum of all

proglottids = strobila resembles tape Each proglottid has male and female reproductive structures

Can reproduce independently Tapeworm a colony of proglottids?

Anatomy and Identification

Once anchored to the host’s intestinal wall, the tapeworm absorbs nutrients through its skin as the food being digested by the host flows past it and it begins to grow a long tail, with each segment containing independent reproductive system.

Older segments are pushed toward the tip of the tail as new segments are produced by the neckpiece. By the time a segment has reached the end of the tail, only the reproductive tract is left.

It then drops off, carrying the tapeworm eggs to the next host, since, by that point, the proglottid is, in essence, a sac of eggs.

A colony of proglottids?!

Life Cycle Includes intermediate host and primary/definite host

The Tapeworm Diet