Parasit LC2

• Parasitology is the area of biology concerned with the dependence of one living organism on another
• Parasitology specifically studies animal parasites
• Medical Parasitology focuses primarily on the animal parasites of humans and their medical significance
• Tropical Medicine deals with tropical diseases and other special medical problems of tropical regions
• Most diseases found in tropical regions/countries
• Tropical diseases can be indigenous to or endemic in a tropical area but can also be sporadic or epidemic in non-tropical areas
• Malaria is a significant parasitic disease endemic in the Philippines, causing approximately half a billion deaths per year
• Symbiosis is the "living together" of unlike organisms, providing protection or other advantages to one or both partners
• Commensalism involves two species living together where one benefits without harming the other, like Entamoeba coli in the intestinal lumen
• Mutualism is when two organisms mutually benefit from each other, like termites and flagellates
• Parasitism is when one organism (parasite) lives in or on another organism (host) for survival, usually at the expense of the host
• A parasite is an organism that lives on or in a host, providing physical protection and nourishment
• Endoparasites live inside the host's body, causing infection
• Ectoparasites live outside or on the host's body, causing infestation (e.g., lice)
• Erratic parasites are found in organs that are not their usual habitat, like Ascaris in the brain or liver
• Obligate parasites need a host at some stage of their life cycle to complete development and propagate their species (e.g., tapeworms)
• Facultative parasites may exist in a free-living state and become parasitic when necessary
• Accidental/Incidental parasites establish themselves in hosts where they do not ordinarily live, like pig parasites transferred to humans by consumption
• Permanent parasites remain on or in the host's body for their entire life and cannot survive without a host
• Temporary parasites live in the host for a short period of time
• Spurious/Coprozoic parasites are free-living organisms passing through the digestive tract without infecting the host
• Hosts are organisms that harbor parasites and are classified as definitive/final, intermediate, paratenic, or reservoir hosts based on their role in the parasite's life cycle
• Vectors are responsible for transmitting parasites from one host to another, either biologically or mechanically/phoretically
• Biologic vectors transmit the parasite only after it has completed its development within the host, like the Aedes mosquito transmitting Plasmodium
• Mechanical vectors only transport the parasite, like a mosquito carrying a parasite from food to a person
• Pathogens are harmful parasites causing disease and mechanical injury to hosts
• Carriers harbor a pathogen without showing signs or symptoms, like an asymptomatic carrier of Entamoeba histolytica
• Exposure is the process of inoculating an infecting agent, like a mosquito carrying Plasmodium falciparum biting someone
• Infection is the establishment of an endoparasite in the host, like when a female Anopheles mosquito injects Plasmodium falciparum into someone
• Infestation is the presence of an ectoparasite on a host's body, like lice on the surface of the host
• Clinical Incubation Period is the time between infection and evidence of symptoms, like with Plasmodium infection until fever and chills appear
• Biologic Incubation Period is the time between infection and evidence of infection, like the period before demonstrating infection after acquiring the parasite
• Autoinfection occurs when an infected individual becomes its own direct source of infection, like with Enterobiasis (hand-to-mouth transmission)
• Superinfection/Hyperinfection is when an already infected individual is further infected with the same species, leading to massive infection with the parasite
• Modes of transmission include mouth, skin penetration, bites, congenital transmission, inhalation of air-borne eggs, and sexual intercourse
• Contaminated soil and water are common sources of infection, especially in third world countries with poor hygiene practices
• Food may contain the infective stage of parasites, leading to infections like intestinal and liver fluke infections from undercooked or raw freshwater fish
• Vectors like mosquitoes, triatoma bugs, sandflies, cats, and house rats can transmit parasites to humans causing diseases like malaria, Chagas disease, Leishmaniasis, Toxoplasma infection, and Hymenolepis nana
• The mouth is the most common mode of transmission for parasites like Taenia solium, Taenia saginata, and Diphyllobothrium latum through eating contaminated food
• Skin penetration can introduce parasites like hookworms and Strongyloides through exposure to soil or water