Intro

• Parasitology is the area of biology concerned with the phenomenon of dependence of one living organism on another
• It is a scientific discipline that studies the biology of parasites and parasitic diseases
• Clinical parasitology is primarily concerned with the animal parasites of humans and their medical significance
• It focuses on important parasites that cause diseases in humans, including classification, symptoms, disease, lifecycle, transmission, and treatment
• Biological relationships in parasitology include symbiosis, which has 3 forms: commensalism, mutualism, and parasitism
• Commensalism: Two species live together and one benefits without harming or benefiting the other (e.g., Entamoeba coli)
• Mutualism: Two organisms mutually benefit from each other
• Parasitism: A relationship where one (parasite) benefits at the expense of the other (host) (e.g., Entamoeba histolytica)
• Host-parasite relationships involve different kinds of hosts: definitive/final host, intermediate host, paratenic host, and reservoir host
• Definitive/final host harbors the sexual or adult stage of the parasite's life cycle (e.g., Human)
• Intermediate host harbors the asexual or larval stage of the parasite (e.g., Snail)
• Paratenic host does not allow the parasite to develop further but can infect another host (e.g., Wild boar)
• Reservoir host allows the parasite's life cycle to continue and serves as additional sources of human infection (e.g., Pig)
• Parasites can be categorized as endoparasites (inside the host's body) or ectoparasites (outside the host's body)
• Erratic parasites are found in organs not in their usual habitat
• Obligate parasites need a host at some stage of their life cycle to complete their development
• Temporary parasites live on the host for a short period, while permanent parasites remain in the host's body for their entire life
• Accidental/incidental parasites establish themselves in hosts where they do not usually live
• Vectors are responsible for transmitting parasites from one host to another, including biologic vectors (transmit after parasite development) and mechanical vectors (only transport the parasite)
• Exposure is the process of inoculating an infective agent, while infection is the establishment of the infective agent in the host
• Carrier harbors a pathogen without showing signs or symptoms
• Incubation period is the time between infection and symptom appearance, while pre-patent period is between infection and evidence of infection
• Autoinfection occurs when an infected individual becomes their own source of infection (e.g., Enterobiasis)
• Sources of infection include contaminated soil and water, lack of sanitation, consumption of undercooked/raw food, arthropods, cats, rats, and modes of transmission like contaminated food & water, ingestion of raw fish, and portal of entry through the mouth or skin penetration
• Modes of transmission include contaminated food & water, arthropods, congenital transmission, inhalation of airborne eggs, sexual intercourse, and life cycles of parasites
• Epidemiologic measures in parasitology include epidemiology, incidence, prevalence, cumulative prevalence, intensity of infection, and morbidity
• Treatment methods in parasitology include deworming, selective treatment, targeted treatment, and preventive chemotherapy
• Prevention and control strategies involve morbidity control, information-education-communication, environmental sanitation, sanitation, disease eradication, and disease elimination
• Coverage refers to the proportion of the target population reached by an intervention, and efficacy and effectiveness are measures of drug effects against infective agents
• Drug resistance is the loss of susceptibility to a drug in a parasite population that was previously sensitive to it