Introduction to Parasitology

• Parasitology is the study of parasites, their hosts, and the relationship between them.
• Parasitology also deals with the parasite that infect humans, the diseases it causes and the response generated by the humans against them.
• A host is an animal or plant on or in which a parasite or commensal lives.
• A parasite is an organism that lives in or on another organism and benefits by deriving nutrients at the host’s expense.
• Definite host is a host where the sexual or adult stages of the parasite are found or seen.
• Immunodiagnostic methods are used to identify the parasitic antigen or the antibody that is produced in response to the parasitic infection.
• Immunoassays are available in three formats: EIA, DFA, and Lateral Flow (Immunochromatography).
• Antigen detection in stool samples is usually performed using fecal immunoassay, which is sensitive compared to routine O&P examination.
• Immunodiagnostic methods include Enzyme Immunoassay (EIA), Indirect Immunofluorescence Assay (DFA), Western Blot, Radial Immunoassay (RIA), and Immunodiffusion.
• Intermediate host is a host where the sexual (immature) or larval stages are seen or found.
• Predator is the attacker or the one that attacks other living animal or organism but not necessarily killing them.
• Prey is the victim.
• Fresh, soft, loose, watery – 3 procedures should be done.
• Direct wet mounts of preserved feces may allow detection of parasite that do not concentrate well.
• Formed – examined by concentration method.
• Direct saline wet mounts of fresh feces allow detection and observation of motile protozoan trophozoites and helminth larvae.
• Microscopic Examination can be performed by direct wet mounts of fresh material, wet mounts of concentrate or permanent stains.
• Concentration procedures increase the examiners ability to detect protozoan cysts and helminthes ovum and larvae but unsatisfactory for detecting protozoan trophozoites.
• Watery – concentration by centrifugation rather than by flotation formalin ethyl acetate concentration.
• Permanent stains are useful for detection and morphologic examination of protozoan trophozoites and cysts.
• Scavenger are those that devour the dead of natural causes taking the leavings of the predator.
• Symbiosis means living together and usually involves protection.
• Commensalism is a form of symbiosis usually it is beneficial to one partner and at least not disadvantageous to the other.
• Mutualism is a type of commensalism that is usually beneficial to both.
• Parasitism is a symbiotic relationship usually injured the host to some degree through the activities of the other animal.
• Ectoparasite is a parasite that colonizes the superficial area of the body.
• Endoparasite is a parasite that is found within the body.
• Vector is a carrier or transmitter of the parasite, usually a blood sucking insect.
• Portals of Entry are the common ways through which a parasite enters the body.
• Mode of Transmission or Exposure to Infection is the way through which a parasite infects a person.
• Contaminated soil and water are common ways through which a parasite enters the body.
• Food containing the immature infective stage of the parasite is another common way through which a parasite enters the body.
• Blood sucking insect is a common vector that inoculates the infective stage of the parasite into the skin.
• In venipuncture, the anticoagulant of choice is EDTA and should be done within an hour after collection.
• Trauma can be either external or internal and can be categorized as slight, moderate or severe.
• Ground itch, Amoebic colitis, Balantidiasis are examples of diseases caused by parasites.
• Blood is also the specimen of choice for making a good thick and thin blood smear/film.
• The host cell and parasite’s chromatin stains vividly but the hemoglobin in erythrocytes will appear as pale red and it’s the only stain that allows visualization of the RBC stippling that occurs with infection by certain malarial parasite.
• Lytic Necrosis is a process where lytic enzymes are produced by certain parasites to lyze tissues and incorporate them to their cytoplasm.
• Examination is done at the feathered edge of the film as erythrocytes are pushed through the edge during the smear preparation.