Helminths (Parasitic Worms)

 

   Kingdom: Animalia

Phylum: Platyhelminthes (flatworms)

Dorsoventrally flattened; incomplete/no digestive tract

   Class: Trematodes (flukes)

Leaf-shaped body, oral and ventral suckers

Named for tissue they live in (definitive host)

   Class: Cestodes (tapeworms)

Long and thin, with scolex and proglottid sections

Intestinal parasites, but can invade tissues

Phylum: Nematoda (roundworms)

Cylindrical shape; complete digestive tract

Infective egg or infective larvae

 

Characteristics of Helminths

   Reduced digestive system

   Reduced nervous system

   Reduced locomotion

   Complex reproduction

 

Life Cycle of Helminths

   Monoecious (hermaphroditic)

Male and female reproductive systems in one animal

   Dioecious

Separate male and female

   Egg → larva(e) → adult

 

Important Helminth Diseases

   Fluke – Lung Fluke

   Tapeworm – Taenia saginata, Echinococcus

   Nematode – Pinworm, Trichinellosis*

*    CDC pathogen

 

Arthropods as Vectors

   May transmit diseases (vectors)

   Kingdom: Animalia

Phylum: Arthropoda (exoskeleton, jointed legs)

   Class: Insecta (6 legs)

Lice, fleas, mosquitoes

   Class: Arachnida (8 legs)

Mites and ticks

 

Arthropods Vector Types

   Mechanical transmission

   Biological transmission

Microbe multiplies in vector

   Definitive host

Microbe’s sexual reproduction in vector

 

Important Arthropod-Vectored Diseases

   Flea – Plague

   Mosquito – Dengue, Malaria, Yellow Fever

   Tick – Ehrlichiosis, Lyme Disease, Rickettsiosis, Tularemia