True about epidemiology of leprosy -a) If high prevalence of cases seen in childhood, it means disease is under controlb) Lepra bacilli cannot survive outside hman bodyc) Bacterial load is high in tuberculoid varietyd) Insect can transmit the diseasee) Relapse rate is indicator of efficacy of the drug regimen

**Core Concept**
Leprosy, also known as Hansen's disease, is a chronic bacterial infection caused by *Mycobacterium leprae* that primarily affects the skin, mucous membranes, and peripheral nerves. The epidemiology of leprosy involves understanding its transmission, distribution, and control.

**Why the Correct Answer is Right**
Option **C** states that the bacterial load is high in tuberculoid variety. This is correct because in the tuberculoid form of leprosy, the immune response is more effective, but the bacterial load is still relatively high, typically ranging from 10^2 to 10^4 bacilli per skin smear. This is in contrast to the lepromatous form, where the bacterial load is much higher, often exceeding 10^7 bacilli per skin smear.

**Why Each Wrong Option is Incorrect**
* **Option A:** This statement is incorrect because a high prevalence of cases in childhood does not necessarily mean the disease is under control. In fact, a high prevalence in childhood often indicates poor access to healthcare, lack of early diagnosis, and inadequate treatment, which can lead to the spread of the disease.
* **Option B:** This statement is incorrect because *Mycobacterium leprae* can survive outside the human body for a short period, typically up to 72 hours, but it is highly susceptible to environmental factors such as temperature, humidity, and sunlight.
* **Option D:** This statement is incorrect because leprosy is primarily transmitted through close contact with an infected person, not through insects. Insect vectors like mosquitoes and flies can transmit other diseases, but not leprosy.
* **Option E:** This statement is incorrect because the relapse rate is not a reliable indicator of the efficacy of the drug regimen. Relapse rates can be influenced by factors such as the duration of treatment, the quality of care, and the patient's adherence to treatment.

**Clinical Pearl / High-Yield Fact**
It's essential to note that leprosy has a long incubation period, typically ranging from 3 to 5 years, which can make early diagnosis challenging. A high index of suspicion and early detection are critical in controlling the spread of the disease.

**Correct Answer:** C. The bacterial load is high in tuberculoid variety.