The causative agent of Poliomyelitis is

Step 1: Analyze the question The question asks which type of organism or agent causes poliomyelitis (polio).

Step 2: Explain the concept Disease-causing agents (pathogens) fall into different groups:

• Viruses: e.g. polio, HIV/AIDS, measles, yellow fever, influenza
• Bacteria: e.g. tuberculosis, cholera, typhoid, tetanus
• Protozoa: e.g. malaria (Plasmodium), sleeping sickness (Trypanosoma), amoebic dysentery
• Fungi: e.g. ringworm, athlete's foot, candidiasis

Step 3: Apply it to the question Poliomyelitis is caused by the poliovirus, an enterovirus. It spreads mainly through the faecal-oral route, through contaminated food and water, and attacks the nervous system. It can damage motor neurons in the spinal cord, leading to muscle weakness or paralysis, especially in the legs.

Eliminating the other options:

• B (Fungus): fungi cause skin infections like ringworm, not polio.
• C (Protozoan): protozoans cause malaria and sleeping sickness.
• D (Bacterium): bacteria cause diseases like cholera and TB.

Step 4: Answer The causative agent is a virus, so the correct option is A.

Exam tip: Remember the common viral diseases with the phrase "PHIM-CY": Polio, HIV, Influenza, Measles, Chickenpox, Yellow fever. Polio vaccines (like the oral polio vaccine given to Nigerian children) are also a good clue, since vaccines are widely used against viral diseases.