Which Brucella species is the most pathogenic to humans?

Introduction:
Brucellosis is a zoonosis caused by Brucella spp. Human disease severity varies by species due to differences in virulence and host preference.

Given Data / Assumptions:

• We compare pathogenicity of common Brucella species in humans.
• Species include B. melitensis, B. abortus, B. suis, and others.

Concept / Approach:
B. melitensis (from goats/sheep) is most virulent to humans, causing acute, severe disease; B. abortus (cattle) and B. suis (pigs) are typically less severe; B. canis is generally milder.

Step-by-Step Solution:
Consider human clinical severity rankings. Recognize B. melitensis as the most pathogenic for humans. Select Brucella melitensis as the correct option.

Verification / Alternative check:
Standard epidemiology sources rank B. melitensis highest in human virulence.

Why Other Options Are Wrong:

• B. abortus / B. suis: Cause human disease but generally less severe than B. melitensis.
• B. canis / B. ovis: Typically milder or rarely cause human illness.

Common Pitfalls:
Assuming prevalence in livestock equates to human virulence; virulence and host tropism differ among species.

Final Answer:
Brucella melitensis is the most pathogenic to humans.