Read Disease Questions by Agent and Route
Identify the pathogen group, the body site or route involved, and the clue that distinguishes one disease from another.
Living-system questions are solved by matching a structure or organism to its function, process and stated condition.
Match organism and affected site
Ascaris is an intestinal helminth and heavy infection may cause blockage, bleeding and anaemia. Entamoeba histolytica is a protozoan of the large intestine; it can invade tissue and feed on red blood cells. Ringworm is a fungal skin infection caused by dermatophytes including Trichophyton, Microsporum and Epidermophyton—not Ancylostoma.
Trace route and barriers
Dysentery can be bacterial or protozoan and sanitation plus safe water reduce faecal-oral spread. Ingested pathogens must withstand the stomach's acidic pH and digestive enzymes. Common cold spreads through droplets and contaminated objects. Pneumonia affects the lower respiratory tract and alveoli; contaminated food is not its usual route.
Count infectious conditions carefully
From the listed conditions, swine flu, ringworm, pneumonia, typhoid, common cold, leprosy and rabies are infectious. Cancer and rheumatoid arthritis are not infectious, giving seven.
OlympIQ exam lens
- ✓Ascariasis: intestinal roundworm; can obstruct the gut.
- ✓Amoebiasis: Entamoeba invades the large intestine.
- ✓Ringworm: dermatophyte fungi; Ancylostoma is a worm.
- ✓Separate respiratory droplet spread from food/water transmission.
- ✓Seven of the nine listed diseases are infectious.
Classify each disease by its actual pathogen and route; a symptom alone does not tell you whether it spreads by food, water, air or contact.
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