Commensalism: The relationship in which parasite driving nourishment from a Virulent agent cause disease when introduce into the host in small number. Types of parasitism (pathogenicity, being pathogenic). – obligate parasites: in defined host (range of hosts) always pathogenic, never found in the normal flora. Lecture outcomes: at the end of this lecture you should know: • the terms used in describing host-parasite relationships. • the four phases of an infectious disease.
This is the life cycle of one type of human parasite. Parasite eggs that pass in the feces hatch into free living larvae and can survive for a short time in moist, warm soil. These larvae can then invade a host via skin in this case penetrating bare feet. Once inside the intestines of the host, the worms mature and lay eggs to perpetuate the cycle.
Parasite/Host Relationships - ppt download
Note that this particular parasite has no intermediate host. The parasite moves to many different places inside horse as it grows and feeds off the animal host, sometimes making animal sick.
The animals eats the eggs that are now on the pasture grass. Tick shown on lower left, tapeworm top middle, and roundworm on the far right. Mutual evolutionary adaptations of parasite and host may lead to a parasite becoming less damaging and the host becoming more resistant! This means that both the host and parasite change over time!!! Just like many other organisms on the planet!
Sounds like a big statement, take this time to ask students what this means. They have had exposure to adaptations, so they should be able to generate thoughts as to why this also applies to parasites and their hosts. Why would each need to change?
HOST PARASITE RELATIONSHIP - ppt video online download
Prompt students to think about how environmental factors may change and therefore so do the species living within them in order to survive. Medications for parasite treatment may also cause the parasite to change and mutate over time, becoming more resistant to the current medications.
You must first know what a niche is. What does it do to survive? Allow students time to discuss or ask questions about niche and understand it completely before moving on.
Have students explain or discuss the Niche of the three pictures on slide. Use terms like heterotroph, autotroph, predator, prey, consumer, producer… Go to this link for more detailed information on niche: The parasite must find a place within the host to survive. A particular parasite may occupy a specific site and utilize certain host resources and this defines its niche.
So a niche is a description of the parasites requirements, not of host attributes. Where would the tick live on the deer? What would it do to survive? Each causes different symptoms and different infections.
As host is treated for parasite, both can build up immunities. The host to the parasite and the parasite to the treatment.
That is why new methods of treatment must constantly be created!! Roundworms — dogs, cats, sheep, cows, humans! Basically almost all mammals can get some type of roundworm! Tapeworms — basically all mammals again Hook worms — all mammals Heartworms — dogs, cats Dysentery carrying amoeba — most commonly contracted by people eating contaminated food and drinks by poor hygiene.
Flies — all mammals, and many other kinds of animals Fleas - all mammals and many other animals Bugs, lice, mites, ticks — all animals 16 Parasites in a food chain or food web: Contact and Entry Into Host 2.
HOST PARASITE RELATIONSHIP
Gaining a suitable niche In the host where it lives to gain nutrition 6. Development in environment or intermediate host.
Continued survival in Host. May have to move to different areas within host body. Escape from host, released back into environment.
Host can eat eggs that are on grass or other plant life, or if parasite is on grass or other plant life, it can crawl on to host. Ask as a class discussion question: What do you think the effects of over-grazing might be?
What do you think the effects of leaving a pasture idle for a long time might be? More exposure to parasite eggs and greater degree of infestation. They can't survive indefinitely outside a host and at some point they must invade the primary host in order to sustain the cycle.
Skin Contact Biting insects, passes in to blood stream or, Parasite can penetration through skin. From the mother to the baby while in the womb. Human lesions from hookworm migration 20 Examples of Specific Niche Needed for Protection and Nutrition The babesia parasite is only found within red blood cells Human head lice only reproduce on humans and prefer areas of skin with lots of hair, like the head 21 Contact with Host: Starts and Restarts Life Cycle!
Animals come to the eggs or larva that can not move Active Contact: Some parasites move to areas where they are more likely to come into contact with an animal. Fleas actually detect vibration and carbon dioxide and will move towards it because it means that a potential host is near by One species of roundworm larvae crawl up vegetation onto the leaves to increase their chances of being eaten 22 Survival in Host Evade the immune system long enough to reproduce.
Methods to avoid the immune system: Live inside cells of the host Mimic host substances so they are not recognized Live in the gastrointestinal tract of the host out of reach of the immune system Form a protective cyst which cannot be penetrated by the host immune system Roundworms in Intestines 23 Reproduction Produce numerous numbers of offspring Most of which will not complete their life cycles Tapeworm eggs 24 Escape from Host The larva, eggs, or cysts have to have a way to leave the host Most common way is through the feces Can also leave through urine, saliva, semen, milk, mucous membranes, or blood 25 Development in Intermediate Host Some parasites require another host to complete their life cycle, this is called an Intermediate Host.
This particular parasite has the cow or sheep as the direct host and a snail as the indirect host An intermediate host often helps to increase the spread of the parasite and protect the parasite from spending too much time in the environment.
Intermediate Hosts are very common and essential to the survival and spread of the parasite. They allow the parasite to travel further in environment and be in the environment with less chance of dying before it reaches a new host. It will not reproduce on the intermediate host, it is a step used by the parasite to ensure survival until a new host is found. These areas can be transiently infected but normal clearance mechanisms exist to get rid of the intruders.
The above are examples of mutualism IV. Susch as when one sees peritonitis after a ruptured appendix.
The agent must be observed in every case of the disease. The agent must be isolated from a diseased host and grown in pure culture. When purified agent is inoculated into a healthy but susceptible host, it must cause the same disease. The agent must be reisolated from the newly infected, diseased host, and be identical to the previously identified causative agent. Identification of disease agents, according to the postulates requires growing the organism; this can be difficult or impossible for some: Treponema pallidum, Mycobacterium leprae, and so this cannot be an inflexible approach.
How they behave within a population? NOT all communicable diseases are equally contagious. Contagiousness depends on several factors. II Frequency in a population: Diseases in a population: Typhoid fever b Endemic disease: This term reflects the spread of the disease. Total of cases of disease in a population at any given time.