Biology questions

Prompt 1— (Chapter 15) What is a reservoir host species? Please define it clearly. If a parasite has a reservoir host species, how effectively will the parasite population be controlled by immunizing a susceptible host species? Please use an example to make your argument. (Hint: Contrast the outcome of control with vs. without a reservoir host species.)

• A reservoir host species is a species that  acts as a hub for a pathogen/parasite but does not negatively affect the host.
• Being able to immunize a susceptible host species will allow for better control of spread for a pathogen/species, due to the fact that these host species act as a hub for pathogens/parasites.  Without the reservoir host species, the pathogen has no way to persist through its life cycle. For example, the pathogen plasmodium, which causes malaria, has to have the Anopheles species mosquito as a host to complete its life cycle and infect other species. Without having the mosquito host, plasmodium can not reproduce.
• For another example Beavers are a reservoir for Giardia (a parasite that causes severe diarrhea among other symptoms) , if the beavers were to be immunized from giardia then they would not be a carrying host. Water streams that are habitats for beavers would not be an active source of giardia vs. if no immunization was given, humans would have to continue to be careful with contact with beavers and the streams they live in. (There will still be other sources of giardia, but less if beavers are immunized).

Prompt 2— (Chapter 15) What is an emerging infectious disease? Please define it clearly. Why might we continue to discover new emerging infectious diseases? Please give at least 2 reasons, and explain them clearly.

• An emerging infectious disease is a newly discovered or rare disease that increases in abundance. It often occurs when a mutation allows a pathogen to jump to a new species.
• We might continue to discover new emerging infectious diseases because…
  • Larger and denser human populations allow diseases to spread easier and faster. Therefore, as our population continues to increase, we may see more new infectious diseases, especially in areas with urban poverty where sanitation and health care is typically lacking. In addition, the increase in urbanization will decrease and blur the boundaries between wildlife seeking refuge in urban cities, ex. monkeys habituating in urban cities.
  • Humans are unique in the fact that we can easily travel and spread viruses across the globe in a matter of weeks, further contributing to the spread of new diseases.
  • Close contact to animals in unsanitary conditions is a regular experience in many countries around the world and can lead to the spread of  zoonotic diseases. The number of factory farms and wet markets are increasing in order to meet the demand for meat consumption and these places typically involve humans being in close contact with animals and any diseases they may carry. When the boundaries between animals and humans get blurred, the chances of new emerging infectious diseases increases.
  • As the average temperature of the planet increases, there will be a greater increase in emerging infectious diseases. One reason for this is because as temperatures increase, vector-borne diseases such as malaria will increase. The reason for the increase is because the distribution of the host, mosquitos, will expand.  (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1539106/)

Prompt 3— (Chapter 15) The S-I-R model of parasite and host dynamics that you have learned is a simple model. For example, it does not consider the situation that allows new susceptible individuals to be added (via immigrate or be born) into the population. So, how would the outcome change if we allow new susceptible individuals to be born into the population? (Note: This would be closer to the real situation as we have seen in COVID-19). (Hint: Contrast the outcome of the model before vs. after allowing susceptible individuals to be added.)

• The S-I-R model (Susceptible Infected Resistant) is the simplest model of infectious disease transmission that incorporates immunity. In this model, all individuals begin as susceptible to the pathogen (S). Of those, some number become infected (I). Of those, some number develops resistance via immunity (R)
• Essentially, this model can be used to examine the conditions that favor an epidemic versus the conditions that cause a disease to decline
• In the basic S-I-R model, when the infection is introduced at the beginning of the time period, there is an initial rapid growth in the number of infected individuals. As some infected individuals recover and become resistant, there are fewer susceptible individuals left to infect, so the number of infected individuals declines. But this basic model does not take new susceptible individuals (immigration or birth) to be added into the population.
• When taking into consideration immigration/births, they act as possible hosts that continue the spread not allowing that community to achieve immunity.  Allowing for the spread of infections will increase the chances of a mutation occurring making it that much harder for a community to reach immunity.

Prompt 1— (Chapter 15) What is a reservoir host species? Please define it clearly. If a parasite has a reservoir host species, how effectively will the parasite population be controlled by immunizing a susceptible host species? Please use an example to make your argument. (Hint: Contrast the outcome of control with vs. without a reservoir host species.)

Prompt 2— (Chapter 15) What is an emerging infectious disease? Please define it clearly. Why might we continue to discover new emerging infectious diseases? Please give at least 2 reasons, and explain them clearly.

Prompt 3— (Chapter 15) The S-I-R model of parasite and host dynamics that you have learned is a simple model. For example, it does not consider the situation that allow new susceptible individuals to be added (via immigration or birth) into the population. So, how would the outcome change if we allow new susceptible individuals to be added into the population? (Note: This would be closer to the real situation as we have seen in COVID-19). (Hint: Contrast the outcome of the model before vs. after allowing susceptible individuals to be added.)