Parasitic Helminths

• Trematode Parasite (Fluke) - flat worms
• Cestodes (tapeworms)
• Nematodes (round worms)

Trematode Parasite (Fluke) (flat worm)

1. Clonorchis sinensis - Oriental Liver Fluke
2. Paragonimus Westermani - Lung Fluke
3. Schistosoma mansoni - Blood Fluke

Cestode Parasite (tape worm)

• Dipylidium caninum
• Hymenolepis nana
• Echinococcus granulosus
• Taenia spp.
  • Taenia Saginata Proglottid
  • Taenia Solium Scolex

Clonorchis (Opisthorchis) sinensis 

Oriental Liver Fluke / Trematode Parasite (Fluke)

• Causes clonorchiasis, a liver disease.
• Infection typically occurs when under-cooked infected fish is ingested.

Clonorchis sinensis - (Oriental Liver Fluke)

pic.: egg in a fecal specimen

Clonorchis sinensis Adult

Oriental Liver Fluke

pic.: adult

Infection typically occurs when under-cooked infected fish is ingested

Causes clonorchiasis, a liver disease

Paragonimus Westermani

Lung Fluke

Trematode Parasite (fluke)

• Causes paragonimiasis
• Infected when eating under-cooked crabs or crayfish infected with the cysts
• Symptoms: local inflammatory response followed by ulceration, cough with discolored or bloody sputum, difficulty breathing

Paragonimus Westermani - lung fluke

pic.: egg in a fecal specimen

Paragonimus Westermani - lung fluke

pic.: Adult

Infected when eating under-cooked crabs or crayfish infected with the cysts.

Causes paragonimiasis

Schistosoma mansoni / Blood Fluke

Trematode Parasite (fluke)

• Infection occurs via contact with fecally contaminated water containing juveniles of the species
• Symptoms: bloody diarrhea, abdominal pain, and lethargy

Schistosoma mansoni / Blood Fluke

pic.: egg in a fecal specimen

Schistosoma mansoni / Blood Fluke

pic.: Adult

Dipylidium caninum

Cestode Parasite (tape worm)

• common parasite of cats and dogs
  
• infection usually occurs in children
  
  Symptom: asymptomatic, mild abdominal discomfort, loss of appetite, indigestion
• Dog, cat, or child ingests one of these fleas

Dipylidium caninum

pic.: Egg Packet

Dipylidium caninum

pic.: Scolex

Dipylidium caninun Proglottids

Echinococcus granulosus

• Definitive host is a carnivore.
• Intermediate host usually an herbivorous mammal
• Develop hydatid disease.

Echinococcus granulosus

pic.: cyst in lung tissue

Echinococcus granulosus -

hydatid disease

Echinococcus granulosus

pic.: Adult

Hymenolepis nana

Dwarf Tapeworm

Infection may involve hundreds of worms

symptoms are usually mild

Hymenolepis nana

pic. Scolex

Hymenolepis nana

pic. Proglottids

Hymenolepis nana

pic.: egg in a feces

Taenia saginata

Taenia saginata

Beef Tapeworm

Cysticercosis

Taenia saginata

pic. Proglottids

Taenia solium

pic. scolex

Pork Tapeworm
T. solium life cycle is similar to T. saginata.
Cysticercosis

Ascaris lumbricoides

Large Nematode
1. Ascaris pneumonia occurs in heavy infections due to the lung damage.
2. If secondary bacterial infections occur, the pneumonia can be fatal.

Enterobius vermicularis

Human Pinworm
1. Favor fecal-oral transmission of the parasite.
2. Poor sanitary habits of children make them especially prone.
3. Transmission may also involve eggs being
carried on air currents.

Ancylostoma duodenale
Necator americanus

Hookworm

Eggs are passed in the feces.

Strongyloides stercoralis

Intestinal Threadworm
1. Infection occurs by penetration of the skin by infective juveniles from fecally contaminated soil.

Wuchereria bancrofti

Filarial Worm
1. causes lymphatic filariasis.
2. Infection occurs from the bite of a mosquito harboring infective juveniles.
3. obstruction of lymphatic vessels occurs and results in elephantiasis.
Abundant at night when the mosquito vector is
active.