Final answer:
Vaccinating individuals in a reservoir species can be effective in controlling a parasite by stimulating the immune system to develop immunity and subsequently reducing pathogen transmission through herd immunity. Option 1 is correct answer.
Step-by-step explanation:
It can be effective to control a parasite by vaccinating individuals in a reservoir species infected by the parasite. The concept of using a vaccine in an already infected individual is not aimed at treating the damage caused by the infection, nor does the vaccine attack and destroy the parasites directly. Instead, vaccines work by stimulating the immune system to develop an immune response against the pathogen responsible for infection. This is true for both human-immunizing vaccines as well as those meant for reservoir species in zoonotic infection scenarios.
Vaccines may contain weakened forms of the living pathogen, dead pathogens, viral proteins, or genetically engineered pieces of a pathogen, aimed at generating an immune response and developing immunity. Through herd immunity, when a significant portion of a population is immune, this reduces the number of susceptible individuals and the pathogen's ability to spread, which could effectively control the disease spread within the reservoir species as well.
Considering this information, the correct option is 1) Yes, because the vaccine would heal damage from the infection and leave individuals healthy and immune. However, the explanation is slightly misleading in that while the vaccinated individuals may become immune, the primary function of the vaccine is not directly to heal the existing damage but to prevent future infections and reduce transmission of the pathogen.