Final Examination Review: Parasitology with
Life Cycles
Helminths (Worms)
1. Ancylostoma duodenale & Necator
americanus (Hookworms)
Transmission: Skin penetration by
filariform larvae in soil contaminated with
feces.
Symptoms: Anemia, fatigue, abdominal
pain due to blood loss.
Diagnosis: Eggs in stool.
Life Cycle:
1. Eggs in feces hatch in soil,
releasing rhabditiform larvae.
2. Larvae mature into filariform
(infective stage).
3. Penetrate human skin, enter
bloodstream, travel to lungs.
4. Larvae are swallowed, mature into
adults in the small intestine.
Treatment: Albendazole or mebendazole.
2. Ascaris lumbricoides (Roundworm)
Transmission: Ingestion of eggs in
contaminated food/water.
Symptoms: Malnutrition, intestinal
blockage, respiratory symptoms during
larval migration.
Diagnosis: Eggs in stool.
Life Cycle:
1. Eggs hatch in the intestine,
releasing larvae.
2. Larvae migrate to lungs via blood,
causing respiratory symptoms.
3. Larvae are swallowed and mature
into adults in the intestines.
4. Adults lay eggs excreted in feces.
Treatment: Albendazole or mebendazole.
3. Clonorchis sinensis (Chinese Liver Fluke)
Transmission: Consumption of
raw/undercooked freshwater fish infected
with metacercariae.
Symptoms: Biliary obstruction, jaundice,
hepatomegaly.
Diagnosis: Eggs in stool.
Life Cycle:
1. Eggs ingested by snails hatch into
miracidia, develop into cercariae.
2. Cercariae infect fish, forming
metacercariae (infective stage).
3. Humans ingest fish; metacercariae
mature into adults in bile ducts.
Treatment: Praziquantel.
4. Diphyllobothrium latum (Fish Tapeworm)
Transmission: Consumption of
raw/undercooked freshwater fish
containing larvae.
Symptoms: Vitamin B12 deficiency,
anemia.
Diagnosis: Eggs or proglottids in stool.
Life Cycle:
1. Eggs in water hatch into coracidia,
ingested by crustaceans.
2. Fish eat infected crustaceans,
larvae develop into plerocercoid
larvae.
3. Humans ingest infected fish, larvae
mature into adults in intestines.
Treatment: Praziquantel or niclosamide.
5. Dipylidium caninum (Dog Tapeworm)
Transmission: Ingestion of infected fleas.
Symptoms: Asymptomatic or mild
gastrointestinal discomfort.
Diagnosis: Proglottids in stool or perianal
region.
Life Cycle:
1. Eggs ingested by fleas develop into
cysticercoids.
2. Fleas are ingested by humans or
dogs.
3. Cysticercoids mature into adults in
the intestine, shedding proglottids
with eggs.
Treatment: Praziquantel.
6. Echinococcus granulosus & E.
multilocularis (Hydatid Disease)
Transmission: Ingestion of eggs in dog
feces or contaminated food.
Symptoms: Cyst formation in liver, lungs,
or brain; symptoms depend on location.
Diagnosis: Imaging (CT/MRI), serology.
Life Cycle:
1. Eggs ingested by humans hatch
into oncospheres.
2. Oncospheres migrate to tissues,
forming hydatid cysts.
3. Dogs acquire infection by eating
infected animal organs.
Treatment: Surgery, albendazole.
