Coronaviruses, Horses, and COVID-19 Part 2

 Part 1 covers what information is currently available regarding COVID-19.  This post, part 2, covers coronaviruses in general and this pandemic's origin, and part 3 will cover how this strain can affect horses, dogs, and cats, and what other coronaviruses they can contract.

  While I do possess a BSc. in Biology, I am not a doctor nor a veterinarian, and this will not contain medical advice, just some interesting science to help fight misconceptions about the pandemic.  In times of fear, our greatest weapon is knowledge.  If you have a fever, cough, fatigue, or other upper respiratory symptoms, call your local medical facilities and inquire about next steps.

Accurate as of May 17th, 2020

  There are many strains of coronaviruses, including MERS, SARS, the Flu, COVID-19, and many others.  These are all RNA-based viruses belonging to the Family coronavirus.  This family is broken into alpha-, beta-, gamma-, and (possibly) deltacoronavirus genera (Masters, 2006).  There are many strains of coronavirus that infect mammals and birds, with bats and birds being the biggest vectors.  COVID-19 belongs to the betacoronavirus genera, and originates in bats.  However, if it originates in bats, how did it come to infect humans?

  Zoonotic diseases are diseases that originate in non-human animals and make a jump to infect people.  However, this takes a very long time with a great amount of exposure to infected organisms.  If an animal is sick though, wouldn’t we know to avoid it?

  Many organisms evolve along side others, whether it be a mutualistic relationship, or a parasitic one, co-evolution involves organisms evolving together.  They can adapt to each others physiology and environment, and may even become dependant on each other.  For example, there is a species of moth that is endemic to sloth fur (only lives in that one area) and no where else in the world.  It is completely dependant on the sloths camouflage and protection to live, and the sloths faeces to lay its eggs in to reproduce.  Viruses also co-evolve with many organisms.  They adapt to the hosts environment (body temperature, pH, immune functions etc.) and the host organism’s immune system adapts to keep the virus in check, so it is not really affected by it.

  Viruses, bacteria, and parasites do not want to kill you.  If a virus kills off its host before it has had the time to spread to other people or other populations, then it can’t replicate much or at all.  They need your body to sustain themselves and reproduce, therefore, when given a lot of time to adapt to a specific, suitable host, they can replicate and thrive without killing off their supply of food and shelter.  Why is it then that so many of these viruses and parasites can be so deadly to us?  

  Since these pathogens have adapted to certain environments, the ways that they function and replicate are best suited to this environment.  A pathogen infecting certain types of cells or organs may have no effect on its intended host, but the same functions may be detrimental to another being.  For example, Eschricia coli (E. coli) lives quite happily in all of our lower digestive tracts, but if it manages to get into our blood stream, it can easily kill us.  The functions and purpose it serves in our colon helps our digestive tract as a whole, but elsewhere in the body, those same functions can prove fatal.  This same idea applies to all viruses as well, but rather than moving between organ systems, the jump is between species.

  So how, and why, do viruses make the jump from one species to another?  

  It is a very slow process, and is likely completely unintended.  If an organism is able to take advantage of a new pool of resources, why wouldn’t it?  However, it takes a long time and a lot of exposure for this jump to occur.  Exposure to animals in unsanitary conditions for generations of time increases the likelihood of a disease being passed on from one species to another.  This is because this gives the virus a lot of exposure time to a new environment and immune system.  It my not be enough time, however, for the virus to adapt in such a way that it is not harmful to us.  COVID-19 is a virus that has made the jump, but likely is still acting as if in a bat or a secondary host which is why it has deleterious effects on humans.  A secondary host animal hasn’t yet been identified, but there are some speculations that an infected civet was at the Wuhan market (Fores, 2020).  This only means that we need to limit exposure to infected animals, especially in tight quarters and unsanitary conditions (like the live animal markets).  If we decide to try and eradicate vectors/hosts, we will only be risking ourselves to more exposure and more deadly diseases, so please, I don’t want anybody to take this information regarding zoonotic diseases the wrong way.  

  I hope that this has been helpful to some, and the next post will detail what zoonotic diseases (especially COVID-19) mean for our various pets, and what we can do to help them.

Citations:

Fores, F. (2020).  And now for something completely different: from 1029-nCoV and COVID-19 to 2020-nMan.  Pulmonology. 26: 114-115.

Masters, P. S. (2006).  The Molecular Biology of Coronaviruses. Advances in Virus Research.  66: 193-292.