Parasitology Midterm 2 Review

Ingested eggs source of infection

• Taenia solium

• Hymenolepis nana

• Echinococcus granulosis

• Echinococcus multilocular

Vegetables source of infection

• Fasciolopsis buski

• Fasciola hepatica

• Gastrodiscoides hominis

Skin penetration source of infection

• Schistosoma mansoni

• Schistosoma haematobium

• Schistosoma intercalatum

• Schistosoma japonicum

• Schistosoma mekongi

Fish source of infection

• Diphyllobothrium latum

• Spirometra sp. (sparganosis)

• Clonorchis sinensis

• Opisthrochis viverrini

• Heterophyes heterophyes

• Echinostoma sp.

• Nanophyetes salminocola

Crustacean source of infection

• Paragonimus westermani (freshwater crabs and crayfish)

Pork source of infection

• Taenia solium

Paratenic host

• Spirometra sp. (sparganosis)

Excretory system

• Cestodes – flame cell

• Trematodes – flame cell

Diseases

• Katayama fever – Schistosoma japonicum

• Swimmer’s Itch  - Ornithobilharzia, Austrobilharzia, Dendrobilharzia

Anthelminthics

Praziquantel

• Platyhelminthes except Fasciola

Mode of action

Praziquantel

• effects permeability of worms to calcium causing paralysis due to tonic muscle contractions

Cestodes           and             Larval stages

Cestodes Stage

• Taenia solium

• Taenia saginata

• Taenia asiatica

• Echinococcus granulosis

• Echinococcus multilocularis

• Hymenolepis nana

• Hymenolepis diminuta

• Dipylidium caninum

Larval Stage

• Cysticercus

• Cysticercus

• Cysticercus

• Cystic hydatid

• Alveolar hydatid

• Cysticercoid

• Cysticercoid

Trematodes

Fasciola hepatic

• Liver (tissue migration)

Fasciolopsis buski 

• Small intestine

Clonorchis sinensis

• Liver

Dicrocoelium dendriticum

• Liver

Opisthorchis viverrini

• Liver

Gastrodiscoides hominis

• Large intestine

Echinostoma sp.

• Small intestine

Heterophyes heterophyes

• Small intestine

Paragonimus westermani 

• Lung (tissue migration)

Schistosomes

Schistosoma mansoni

• Inferior mesenteric vein

Schistosoma haematobium

• Inferior mesenteric to visceral plexus

Schistosoma japonicum

• Superior mesenteric vein

Migrations

• Fasciola hepatic - penetrates small intestine → Glisson’s capsule (liver) → biliary ducts

• Paragonimus westermani - penetrates small intestine → abdominal cavity → penetrate diaphragm → pleural cavity → penetrate into lungs and airways

• Schistosoma – penetrates skin → Venous/lymphatics → Right heart → lungs → left heart → liver (        pair)  → mesenteric veins

Laboratory

Sheather’s or ZnSO4 floatation

• Concentration (no good for Schistosoma)

Ether/ethyl acetate sedimentation

• Concentration

Kato-Katz quantitative egg count

• Worm burden estimate

Stoll’s dilution quantitative egg count

• Worm burden estimate

Primary lesions

Romana’s sign

• Trypanosoma cruzi

Chagoma

• Trypanosoma cruzi

Winterbottom’s sign

• Trypanosoma brucei gambiense

Trypanosomal chancre

• Trypanosoma brucei

Malaria clinical    and    P. falciparum sequestration

Malaria clinical

• The classical (but rarely observed) malaria attack lasts 6-10 hours. It consists of:

  • a cold stage (sensation of cold, shivering)

  • a hot stage (fever, headaches, vomiting; seizures in young children)

  • and finally a sweating stage (sweats, return to normal temperature, tiredness).

  • Hepatosplenomegaly

• Severe forms

  • Black water fever

  • Cerebral malaria

  • Severe anemia

P. falciparum sequestration

• Sequestration, the adherence of infected erythrocytes containing late developmental stages of the parasite (trophozoites and schizonts) to the endothelium of capillaries and venules

• Proteins on RBC Surface interact with endothelial surface to effect adhesion

• Most of these proteins are of parasite origin (PHEMP1, KAHRP)

• Disappearance of plasmodia from blood stream

• Pathogenesis related to microvascular blockage

Vectors

• Reduviid bug (Reduviidae)

• Sand fly (Phlebotomus, Lutzomyia)

• Mosquito (Anopheles)

• Hard tick (Ixodes)

• Tsetse fly (Glossina)

• Trypanosoma cruzi, T. rangeli

• Leishmania donovani, L. major, L. tropica

• Plasmodium species

• Babesia species

• Trypanosoma brucei

African sleeping sickness

• West African sleeping sickness

  • Trypanosoma brucei gambiense

  • West and Central Africa

  • Rivers and streams

  • Chronic – years

  • Winterbottom’s sign

  • Encephalitis lethargica

  • Test – lymph node, CSR

• East African sleeping sickness

  • Trypanosoma brucei rhodesiense

  • East Africa

  • Savanah

  • Subacute – months

  • Trypanosomal chancre

  • Pericarditis

  • Test – blood, pericardial fluid

Malaria

Hemoglobin S

• Africa, Mediterranean, Middle East, India

Hemoglobin C

• West Africa

Hemoglobin E

• South East Asia

Thalassemia

• Africa, Mediterranean, Middle East, Asia

G6PD deficiency

• Mediterranean, Middle East, China

Duffy negative

• Africa

Southeast Asian ovalocytosis

• Malaysia, New Guinea

larvae

Larvae

• Cysticercus

• Cysticercoid

• 'Hydatid

• Coenurus

• Procercoid

• Plerocercoid

Stages in life cycle

• Egg

• Miracidia

  • Sporocyst

•  Daughter sporocyst

  • Redia

•   Mother redia

•   Daughter redia

• Cercaria

• Metacyst

• Schistosomula (schistosomes only)

• Adult

Malaria Antigen detection

• Histidine-rich protein II (HRP-II)

  • P. falciparum

  • Present for weeks/months after treatment

• Aldolase

  • All species

  • Clears  quickly with treatment

• parasite Lactate dehydrogenase (pLDH)

  • All species

• Low level parasitemia (<100 parasites/µl)

• microscopists can diagnose infections with parasitemia as low as 5-10 parasites/µl

• Good sensitivity & specificity

• Lateral flow technology

• 5-20 minutes

5 Parasitic Diseases Targeted CDC

• Chaga’s disease – Trypanosoma cruzi (hemaflagellate)

• Cysticercosis – Taenia solium (cestode)

• Toxocariasis – Toxocara canis (nematode)

• Toxoplasmosis – Toxoplasma gondii (coccidian protozoan)

• Trichomoniasis – Trichomonas vaginalis (flagellate protozoan)