**Question:** Conjunctivitis is caused by all except -

A. Viral conjunctivitis (e.g., herpes simplex virus)
B. Bacterial conjunctivitis (e.g., Haemophilus influenzae)
C. Fungal conjunctivitis (e.g., Aspergillus)
D. Protozoal conjunctivitis (e.g., Toxoplasma gondii)

**Core Concept:** Conjunctivitis is an inflammation of the conjunctiva, the transparent mucous membrane that covers the white part of the eye (sclera) and the inner surface of the eyelids. It is caused by various pathogens, including bacteria, viruses, fungi, and protozoa. However, the question is asking about pathogens that are NOT involved in causing conjunctivitis.

**Why the Correct Answer is Right:** The correct answer is D, as protozoal conjunctivitis is caused by Toxoplasma gondii, which is a parasite, not a virus, bacteria, fungi, or a fungal infection. Toxoplasma gondii is known to cause ocular infections, but not conjunctivitis specifically.

**Why Each Wrong Option is Incorrect:**

A. Viral conjunctivitis (e.g., herpes simplex virus) - Viral infections are known to cause conjunctivitis, such as herpes simplex virus.
B. Bacterial conjunctivitis (e.g., Haemophilus influenzae) - Bacterial infections can cause conjunctivitis, like Haemophilus influenzae.
C. Fungal conjunctivitis (e.g., Aspergillus) - Fungal infections can lead to ocular and even systemic infections, but not exclusively conjunctivitis.

**Clinical Pearl:** Understanding the causes of conjunctivitis helps in differentiating between primary ocular infections and secondary infections involving the eye as part of a generalized disease. This distinction is important for appropriate diagnosis, treatment, and management of ocular infections.