Parasitic Protozoa and Helminths
Introduction
Protozoa |
Helminths |
Biologic properties |
|
Small |
Variable in size |
Unicellular |
Multicellular |
Multiply in host |
Usually do not multiply in host |
Short generation time |
Long generation time |
High basic reproductive rate |
Low basic reproductive rate |
Clinical properties |
|
Random or behavior influenced distribution |
Aggregated distribution |
Infection is usually transient |
Tend to induce persistent infection |
Disease may be initiated by a small innoculum |
Disease is related to intensity of infection |
Varies from asymptomatic to acute disease |
Asymptomatic to chronic disease |
Immunological properties |
|
Strong transient immune response |
Moderate, sustained immune response |
Solid immunity is rare |
Partial immunity may occur |
Infection is not associated with eosinophilia |
Tissue infective stages are associated with eosinophilia |
Elaborate evasive mechanisms |
Unclear evasive mechanisms |
Protozoa
Helminths
"worms"Pathogenesis and Host Response
Host Immune Response
"Examples of effective acquired resistance"
|
Leisch recidivans |
Diffuse cutaneous Leisch |
# lesions |
Usually one |
++++ |
# lymph/lesion |
+++ |
+/- |
Skin test |
+++ |
- |
In vitro response |
+++ |
- |
# parasites/macrophage |
+ |
++++ |
Evasion
"Examples of how protozoa escape host defenses"