Brucellosis can be transmitted by all of the following modes, except-
**Core Concept**
Brucellosis is a zoonotic disease caused by the bacterium Brucella, primarily transmitted to humans through contact with infected animals or contaminated animal products. The disease can be acquired through various routes, including inhalation, ingestion, and cutaneous exposure.
**Why the Correct Answer is Right**
Brucellosis can be transmitted through inhalation of aerosols contaminated with Brucella bacteria, which can occur in laboratory settings or during animal handling. Ingestion of contaminated animal products, such as unpasteurized dairy or undercooked meat, is also a common mode of transmission. Cutaneous exposure can occur through direct contact with infected animals or contaminated materials. Additionally, Brucella can be transmitted through the placenta from mother to fetus, as well as through organ transplantation from an infected donor.
**Why Each Wrong Option is Incorrect**
- **Option A:** Incorrect because Brucellosis is not primarily transmitted through vectors like ticks or mosquitoes, which are more commonly associated with other zoonotic diseases.
- **Option B:** Incorrect because Brucellosis is not typically transmitted through casual contact with an infected person, unlike some other infectious diseases.
- **Option C:** Incorrect because Brucellosis is not commonly transmitted through contaminated water or food, although ingestion of contaminated animal products is a known risk factor.
**Clinical Pearl / High-Yield Fact**
It is essential to note that Brucellosis can have a prolonged incubation period, often ranging from 1-3 weeks, and can manifest with nonspecific symptoms such as fever, fatigue, and headache, making early diagnosis challenging.
**Correct Answer: A.