1. Beware of potentially graphic content.
Parasites
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2. Helminths - WORMS Life Stages egg, larva, adult; complex life cycles
infective stage: egg or larva
definitive host: harbors adult stage
intermediate hosts: may be more than one
Classifications:
Nematodes - roundworms
Platyhelminthes - flatworms
Trematodes - flukes- nonsegmented
Cestodes - tapeworms- segmented

3. Cestodes, including tapeworms, have a head region called a scolex.
Tapeworms generally live in the host’s intestine, absorbing nutrients and absorb directly.
Figure 18 (C) T. saginata showing the suckers and hooks
© Dennis Kunkel Microscopy, Inc./Phototake/Alamy Images

4. Tapeworms survive in the human intestines.
Beef and pork tapeworm disease are caused by Taenia saginata and Taenia solium, respectively.
They are acquired by eating poorly cooked beef or pork. The scolex attached to the intestine, causing obstruction and mild diarrhea. Longest is 37 feet long. .

5. Figure 19: Roundworms in intestines.
Roundworms (Phylum Nematoda) live in every habitat on Earth.
Damage to the host often occurs by large worm burdens in vessels or intestines.
Figure 19: Roundworms in intestines.
© R.F. Ashley/Visuals Unlimited

6. Nematodes - roundworms
Ascaris lumbricoides- adult stage

8. Trichinella spiralis - roundworm

9. Enterobius vermicularis – Pinworms – a type of roundworm
Figure 12.29

10. Hookworms have a set of hooks or suckers to attach to the upper intestine.
Hookworms suck blood from intestinal capillaries.
This causes blood loss and anemia.
Humans are the only host.
Larvae in soil penetrate the skin of bare feet and enter the bloodstream. You get this by playing outside without shoes on.
Figure 24: A Hookworm.
© Dennis Kunkel Microscopy, Inc./Phototake/Alamy Images

11. Figure 26: Elephantiasis.
Filariasis is caused by Wuchereria bancrofti.
It is transmitted by mosquitoes. Larvae infect the lymphatic system.
They damage vessels and glands.
After years of infestation, arms, legs, and scrotum swell and distort.
elephantiasis,
Figure 26: Elephantiasis.
© John Greim/Photo Researchers, Inc.

12. Arthropods as Vectors Kingdom: Animalia
Phylum: Arthropoda (exoskeleton, jointed legs)
Class: Insecta (6 legs)
Lice, fleas, mosquitoes
Class: Arachnida (8 legs)
Mites and ticks
May transmit diseases (vectors)
Figure 12.31, 32

13. Arthropod Vectors
Figure 23.24

14. Arachnids Adult arachnids have four pairs of legs
Ticks and mites resemble each other morphologically
Ticks are the most important arachnid vectors
Serve as vectors for bacterial, viral, and protozoan diseases
Second only to mosquitoes in the number of diseases they transmit
Transmit Lyme disease, Rocky Mountain spotted fever, tularemia, relapsing fever, and tick-borne encephalitis
Parasitic mites are found wherever humans and animals coexist
Transmit rickettsial diseases among animals and humans

15. Insects
Adults have three pairs of legs as well as a head, thorax, and abdomen
Fleas
Most fleas are not associated with humans but a few do feed on humans
Bubonic Plague is the most significant disease transmitted by fleas. Killed ½ of Europe in middle ages
Body lice
Parasites that can also transmit disease
Most common among poor or overcrowded communities

16. Insects Flies Among the most common insects
Those that transmit disease are generally bloodsuckers
Mosquitoes
Most important arthropod vector of disease
Carry some of the world’s most devastating diseases

17. Eukaryotic Microbes
Table 12.1