Biology: Zoology: UPSC Previous Year Questions (Science and Technology)

Explanation

Option (b) is correct: The major challenge in developing a malaria vaccine is that humans do not achieve complete immunity through natural infection. Partial immunity can develop after repeated exposure but it is not sufficient to prevent reinfection as the immune system fails to completely clear the parasite. The malaria parasite’s high mutation rate enables it to evade the immune system, further complicating efforts to develop an effective vaccine.

Option (a) is incorrect: Although malaria is caused by various Plasmodium species (e.g., P. falciparum, P. vivax) but this diversity is not the primary obstacle to vaccine development. Vaccines can target shared stages of the parasite’s lifecycle, allowing scientists to address multiple species. While species variation presents a challenge, it is not the main barrier in creating an effective vaccine against malaria.

Option (c) is incorrect: Vaccines have been successfully developed for a wide range of pathogens, including viruses, bacteria, and parasites like malaria.

Option (d) is incorrect: Though humans are the intermediate host for the Plasmodium parasite, they are also crucial in the parasite’s lifecycle. The mosquito is the definitive host, where the parasite undergoes sexual reproduction. In humans the parasite undergoes asexual reproduction inside the liver and red blood cells, making humans essential in the lifecycle.

Explanation

Hepatitis B is a viral infection that primarily affects the liver and can lead to chronic disease. HIV is a virus that attacks the immune system, weakening the body’s ability to fight infections.

Statement 1 is correct: Hepatitis B transmission occurs through contact with infected blood, semen, or other body fluids. It’s 50 to 100 times more contagious than HIV because it can survive longer outside the body and can be transmitted with a smaller amount of the virus. HIV (Human Immunodeficiency Virus) needs a higher viral load and specific conditions to spread.

Statement 2 is correct: The Hepatitis B virus attacks and damages the liver, causing inflammation and scarring (called cirrhosis). This chronic inflammation weakens the liver and makes it more susceptible to liver cancer. Liver cancer specifically hepatocellular carcinoma (HCC) is strongly associated with chronic HBV infection. People with chronic Hepatitis B infection have a much higher risk of developing HCC compared to those who do not have the infection.