Medical Parasitology - Lecture Notes

Medical Parasitology - Lecture Notes

• Parasitology is the study of parasites and parasitism, which is the dependency of organisms on each other for sustenance and survival.
• A parasite is an organism that lives in or on another organism, called a host. It depends on its host for survival, and might cause disease or other negative effects on the host.
• Parasitism is a non-mutual symbiotic relationship where the parasite benefits at the expense of the host, and the host is harmed.
• Medical parasitology is the study of parasites that live on humans, especially those that affect humans.
• Parasites can be categorized into ectoparasites (external), endoparasites (internal), extracellular parasites (outside cells), intracellular parasites (inside cells), hyperparasites (parasites living on other parasites), accidental parasites (occasional), obligatory parasites (depend on the host), and facultative parasites (opportunistic).
• Hosts provide accommodation/residence and nourishment to parasites, and parasites might result in harm, damage, or death to the hosts.
• Hosts can be humans, animals, or plants.
• Hosts are usually larger than the parasite.
• Parasites can be categorized based on their role in the parasite life cycle: definitive host, intermediate host, reservoir host, transport/paratenic host, and dead-end host.
• Definitive hosts are where parasites reproduce sexually.
• Intermediate hosts are where parasites reproduce asexually or have larval stages.
• Reservoir hosts hold the parasites while they grow and multiply, acting as a source of infection to other hosts.
• Transport/paratenic hosts are temporary refuge for parasites.
• Dead-end hosts are where parasites cannot complete their life cycle.

Parasites Types

• Micro-parasites - too small to see with the naked eye, require a microscope (malaria and typhus parasites, HIV, hepatitis, corona, and ebola virus)
• Macro-parasites - large enough to see with the naked eye (worms, leeches, ticks, lice, fleas, bed bugs, and some birds).

Symbiotic Relationships

• Mutualism - both species benefit (e.g., aphids and ants, woolly bats and pitcher plants, bees and flowers)
• Commensalism - one species benefits, and the other is unaffected (e.g., orchids growing on branches, sharks and remora fish, cow and cattle eaglet, barnacle larvae and whales)
• Predation - one species (predator) kills and eats another (prey) (e.g., lions attacking elephants, dolphins chasing fish, orca hunting seals)
• Competition - individuals struggle over a limited resource (e.g., interference competition, exploitation competition, and apparent competition).
• Parasitism - a relationship where one species (parasite) causes harm to another (host) and benefits from it (e.g., tapeworms, fleas, and barnacles).

Host-Parasite Interactions

• Parasites have adaptations to locate their hosts and survive in the host.
• Hosts have adaptations to defend against parasitic infection.
• Parasites often affect their host's reproduction, growth, maintenance, and reproduction, disrupting the host's energy budget.
• Hosts respond to parasites with various defense mechanisms.

Zoonosis

• Zoonosis is a disease that can be transmitted to humans from animals.
• Zoonotic diseases are classified by the type of causative agent, or the mode of transmission.
• Modes of zoonotic transmission: contact-borne, food-borne/water-borne, air-borne, and vector-borne.
• Examples of zoonotic diseases: tuberculosis, anthrax, rabies, Lyme disease.

Explore the fascinating field of medical parasitology, which focuses on the organisms that live in or on humans and their impact on health. This quiz covers key concepts of parasitism, types of parasites, and their relationships with hosts. Dive deep into the world of ecto- and endoparasites, and learn about how these organisms can affect human well-being.