chapter 12 is on parasites or as I like to call it the heie jebi chapter these are all of these nasty things Things That Go Bump in the night so this is going to be an overview of parasites we could spend an entire semester talking about parasitology this is just going to be a little overview you are going to see a lot of organisms and again this is really recogn so if I mention an organism you should be able to recognize if that is a helmouth a worm if it's a protest or if it's a fungi I have also posted many videos just so that you can see these things in action my parasitology professor used to love to horrify us with gory stories um I promise that I won't do that although maybe some of you might like that there is one video that I'm going to caution you is is kind of a gory video but I tried to pick some nice animated um videos with some nice music well at least that's the stuff that that I like so I'm going to try not to gore you too much with all of these chapters we have a lot of definitions so I'm going to go through these definitions but I'm going to use an example of something that we are very familiar with in the Northeast really in all of um in all of the United States and this is the tick so I have a little picture of the tick there now it used to be that we only saw ticks in spring and summer but as um as because of climate change now we're actually seeing them year round ticks can carry many diseases and so this is a concern not only for our health um but are pets as well so what is a parasite a parasite is an organism that lives at the expense of the host organism meaning that the parasite is going to benefit but the host is going to be at a detriment so they're going to have some damage so I'm going to use the tick as an example so that we can tick off the boxes of these definitions so if we take a look at the first definition ectoparasite this means that the organism can live on the surface so we know that ticks can do this lice like headlice can do this as well so the tick will actually burrow its head underneath the skin to feed off of the host um but that's going to be on the surface it's not something that you're going to have to ingest or consume it's not going to be living inside of you we're going to be talking about helmets so different types of worms worms something like a tapeworm would be an endoparasite where it will live inside the host it will latch on to your intestines and then you're going to have to take some super strong drugs to to actually get rid of them um ticks are also going to be temporary parasites so they will feed on the host and then they will actually leave mosquitoes which we're seeing um a lot of of course in the Northeast um they will do the same thing an obligate parasite is something that has to spend at least part of its life cycle in or on a host we're going to see an example of that with malaria malaria is a protest um with the fungi that we will be talking about they are more facultative so they could live on their own but you know given the chance to get some nutrients they'll take it I often call Ticks accidental parasites as well so really what their host is are the wildlife so deer moose um Fox those types of things if we're walking through the woods and that tick can sense a warm body it's going to go for us same thing as our pets that's not necessarily what the tick is going for um but again if there's a warm organism and it's got blood it's going to feed on that them we also know that tix can carry parasites so they are an example of hyperparasitism so there's many different diseases that tix can actually carry um so limes disease being one of those um anop plasmosis biosis there's a lots of tickborne illnesses Rocky Mountain spotted fever we are mostly concerned in this area with limes disease of course we know if you have pets um there are some other tickborne illnesses that we need to be concerned of as well we'll also be seeing hyperparasitism when we talk about malaria and malaria has a biological Vector which is a mosquito and so that mosquito is a parasite and it could actually be carrying malaria so I mentioned the biological Vector the mosquito and malaria some parasites need to be transmitted by way of these vectors they're going to be doing the transporting so a biological Vector like mosquitoes with malaria they're going to be carrying the parasite during a part of its life cycle there are lots of life cycles with parasites we are not going to go through them all it would literally take us a semester to go through them the only life cycle that we're really going to be talking about is the mosquito some of these vectors are going to be mechanical vectors so this is when a vector is transmitting a parasite from one place to another but not during any part of its life cycle sometimes I think of this as an accidental Vector so if you have a fly and it lands on a surface and some parasitic egch stick to those fly legs now it can fly and it can land on like maybe you're at a picnic it land on your sandwich and now it can drop up those eggs and now you are consuming those parasitic eggs so it's almost like the parasite is kind of hitching a ride so this these are different ways that parasites can be transmitted we also know that parasites are going to need host to live on or in so a definitive Host this is going to be kind of like the end game for the par parite as we will see with malaria we are the definitive host so we are going to be a place for that parasite to reproduce some of these life cycles employ an intermediate host so it's kind of like a temporary home often times we can see this with crustations like crabs um we will look at one life cycle that uses a snail as an intermediate host and then a reservoir Host this is when we've got an infected organism and it can actually provide parasites to other organisms so for example our dogs and cats can be like this so um I know that my dogs are actually treated for um ticks and fleas but if that parasite is kind of on them as they come indoors and they bite and then because of their treatment it falls off and now it finds me in the house now I'm going to be infected by that parasite so parasites can be very very sneaky they can actually evade the host immune response some can form cysts so this is almost like a little cocoon and outer protective covering so that the immune system can't find them um some can change their surface markers this is what's called antigenic variation we talked a little bit about this with flu um malaria can actually do this so I'm going to attempt to draw a cell surface so if that malaria parasite if it has certain antigens and now our immune system recognizes those antigens and starts to make antibodies towards them it can be kind of like a chameleon where it actually changes its surface an so I'm trying to draw like a little kind of circular antigen there this is what we call antigenic variation and this is what has proved to be very difficult in developing malaria vaccines because they do undergo antigenic variation so as soon as the immune system gets a lock on it now it's like a chamele and that's changed those antigens so this proves really difficult with with trying to de V vaccines some parasites can also kind of make decoy antibodies so they'll kind of um throw up these decoy antigens so that the immune system starts making antibodies um but those antibodies AR really going to recognize the actual antigens on the parasite some can also be very sneaky like retsas that can actually hide in the immune system some will hide in cells so that the immune system can't find them I mentioned that we could spend an entire semester talking about parasites life cycles um there are different ways that they can divide so many of them will make multiple visions of themselves this is just some parasitology terminology schizogony so a parasite can make many copies of itself some some are hermaphroditic so they can contain both male and female reproductive parts so that they can actually reproduce we're going to talk a little bit about that with these prits in tapeworms and how these pred SE little sections with eggs actually can fall out they can fall to the ground and that's how it kind of repeats the life cycle so just a couple of things on life cycles I'm not going to hold you to knowing all of the life cycles really the only one that we're going to be talking about a lot is going to be malaria