Introduction to Parasitology Flashcards
❖ An area of science, which deals with the study of organisms living permanently or temporarily on or within another organism.
❖ The branch of biology or medicine concerned with the study of parasitic organisms, their hosts, and the relationship between them.
Parasitology
Divisions of Parasitology
Protozoology
Helminthology
Medical Entomology
Medical Parasitology
Tropical Medicine
Tropical disease
Parasite
Host
A study of protozoans which are small, unicellular organisms, which contain nucleus and functional organelles.
Protozoology
A study of worms which are larger, multicellular organisms normally visible to the naked eye in their adult form.
Helminthology
A study of insects and arthropods.
Medical Entomology
Concerned primarily with the parasite that affects humans and their medical significance, as well as their importance in human communities.
Medical Parasitology
Branch of medicine, which deals with tropical diseases and other special medical problems of tropical regions.
Tropical Medicine
An illness, which is indigenous to or endemic in tropical area but may also occur in sporadic or epidemic portions in areas that are not tropical.
Tropical Disease
Lives on or in the host usually on a larger organism, which provides physical protection and nourishment.
Parasite
Harbors parasite and gives nourishment.
Host
What are the host-parasite relationship?
Symbiosis
Mutualism
Commensalism
Parasitism
Living together of unlike organisms, protection or other advantages to one or both partners.
Symbiosis
Relationship is beneficial to both organisms (ex. Termites)
Mutualism
Parasite derives benefit without reciprocating and without injury to the host or both (ex. Entamoeba coli).
Commensalism
Relationship where one organism, the parasite, lives in or another, depending on the latter for its survival and usually at the expense of the host (ex. Entamoeba histolytica).
Parasitism
Parasites according to the Mode of Living
Ectoparasites
Endoparasites
Facultative Parasites
Obligate Parasites
Accidental/Incidental Parasite
Occasional/Periodic
Saprophytes
Erratic
Zoonotic
Living outside the body of the host.
⮚ Infestation
Ectoparasites
Living inside the body of the host.
⮚ Infection
Endoparasites
Able to live outside or inside the host and lead both to a free and parasitic existence.
Facultative Parasites
Completely dependent to the host for its existence throughout its life.
Obligate Parasite
Establishes itself in the host in which it does not ordinarily live.
Accidental/Incidental Parasite
Seeks its host intermittently to obtain nourishment.
Occasional/Periodic
Live in organic substances in state of decomposition.
Saprophytes
Those that live in an organ different from the one it usually parasitize.
Erratic
Animal parasites, non-human parasites that may cause human infections.
Zoonotic
Parasites according to Duration of Parasitism
Temporary Parasites
Permanent Parasites
Free living during part of existence, larval stage has different host from its adult stage.
Temporary Parasite
Remain on the body of the host in all stages of its life cycle.
Permanent Parasite
Parasites according to Pathologic Conditions
Spurious/Coprozoic parasite
Coprophilic parasite
Hematozoic parasite
Cytozoic parasite
Coelozoic parasite
Enterozoic parasite
Passes digestive tract of humans without infecting them.
Spurious/Coprozoic parasite
Parasite multiply in fecal matter outside the human body.
Coprophilic parasite
Lives inside the red blood cells
Hematozoic parasite
Lives inside the cells or tissues
Cytozoic parasite
Lives in the body cavities
Coelozoic parasite
Lives in the intestine
Enterozoic parasite
Types of Host
DRIP
Definitive Host
Reservoir Host
Intermediate Host
Paratenic Host
It is a final host, harbors the adult and sexually mature form.
Definitive Host
harbors the larvae or asexual stage of the parasite ∙
Intermediate Host
Animal that harbors the same parasite of man (ex. Balantidium coli).
Reservoir Host
Harbors a stage of the parasite where in no further development in parasite takes place (ex.Angiostrongylus cantonensis).
Paratenic Host
Sources of Exposure to Infection
❖ Pathogens
❖ Carrier
❖ Exposure
❖ Infection
❖ Incubation
❖ Pre-patent period
❖ Autoinfection
❖ Superinfection or Hyperinfection
❖ Coinfection
can be animal parasites that are harmful and frequently cause mechanical injury to their host.
Pathogens
Harbors a particular pathogen without manifesting signs and symptoms.
Carrier
Process of inoculating an infective agent.
Exposure
Establishment of the infective agent in the host .
Infection
Period between infection and evidence of symptoms.
Incubation Period
Biological incubation period, period between infection and acquisition of the parasite and evidence or demonstration of infection.
Pre-patent period
Infected individual becomes his own direct source of infection (ex.Enterobius vermicularis).
Autoinfection
Already affected individual is further infected with the same species leading to the massive infection with the parasite.
Superinfection or Hyperinfection
Simultaneous infection of a host by two or more parasite (Ex. Presence of Ascaris lumbricoides and Trichuris trichiura in the stool sample).
Coinfection
Lack of sanitary toilets and use of night soil.
Contaminated soil and water
Parasites in contaminated soil and water.
Soil: Ascaris lumbricoides, Trichuris trichiura, Hookworm, Strongyloides stercoralis
Water: Amoeba, Flagellates, Blood flukes
Consumption of undercooked or raw freshwater fish, crab, snail, beef and pork.
Food containing immature ineffective stage of parasite
Example of Arthropods, blood sucking insects and other wild or domesticated animals
Mosquitoes (Filaria and Malaria)
Triatoma bugs ( Trypanosoma cruzi)
Sandflies (Leishmania)
Cats, dogs and house rats
Source of infection from:
Beddings and clothing
Immediate environment he has contaminated.
Another Person
Self is the source of infection (Ex. Enterobius vermicularis, Hymenolepis nana, and Strongyloides stercoralis).
One’s self or Autoinfection
Responsible for transmitting the parasite from one host to another.
Vector
Types of Vector
❖ Biological Vector
❖ Mechanical Vector
Parasite is seen inside the body of this organism and the parasite needs this organism for its development. Ex: mosquitoes, tsetse flies
Biological Vector
Responsible only for transporting the parasite, the parasite is only seen on the surface of this organism and there will be no development on the parasite. Ex: cockroaches, house flies
Mechanical Vector
Modes of Transmission
❖ Soil transmitted
❖ Arthropod/Vector transmitted
❖ Food-borne
❖ Water-borne
❖ Skin penetration
❖ Congenital Transmission
❖ Direct contact
Portal of Entry
❖ By mouth
❖ Skin penetration
❖ Intranasal: inhalation of eggs
❖ Transplacental infection
❖ Transmammary
❖ Sexual intercourse
Portal of entry that is most common area of invasion for the entrance of intestinal protozoa.
By mouth
Portal of Exit
❖ Stool
❖ Urine
❖ Sputum
❖ Blood
❖ Tissue aspirates and biopsy
❖ Orifice swab
❖ Discharge
Naming of Parasites or its nomenclature is classified by?
International Code of Zoological Nomenclature
Scientific name is written in?
Latinized
Generic and Specific name written format
Consist of a single word written in initial capital letter.
Specific name always begins with a small letter.
Names of genera are written in what format?
Italicized if printed
Underlined if written.
Types of Life Cycle
❖ Simple
❖ Complicated
Most parasitic organisms attain sexual maturity at the
Definitive Host
Larval stage of parasite may pass through different stages in an
Intermediate Host
As life cycle becomes complicated,
The lesser chances are for the individual parasite to survive
Life Stage of a Parasite
- Ova
- Egg
- Larva
- Trophozoite
- Cyst
- Adult
MODE OF REPRODUCTION
❖ Sexual
❖ Asexual
In sexual reproduction, it is called as an “egg birth”, give birth to eggs that must develop before hatching.
Oviparous
Ones that produce eggs but retain them inside the female body until hatching occurs, so that “live” offspring are born.
Ovoviviparous
Being born alive without eggs.
Larviparous or Viviparous
In asexual reproduction, it is called when division is in half.
Binary fission
Unfertilized ovum develops directly into a new individual, natural form of asexual reproduction in which growth and development of embryos occur without fertilization by male sex cell.
Parthenogenesis
Epidemiologic Measures
❖ Epidemiology
❖ Incidence
❖ Prevalence
❖ Cumulative prevalence
❖ Intensity of infection
Science concern with the propagation of the disease, study of patterns, distribution and occurrence of disease.
Epidemiology
Number of new cases of infection appearing in a population in a given period of time
⮚ Absolute number
Incidence
Usually expressed in percentage, number of individuals in a population estimated to be infected
with a particular parasite at a certain time.
Prevalence
Percentage of individuals in the population infected with at least one parasite.
Cumulative prevalence
Number of worm per infected person (worm burden) ∙
Intensity of infection
Direct procedure for intensity of infection.
Counting expelled worms during treatment.
Indirect procedure for intensity of infection.
Counting helminth egg excreted in feces, expressed in egg per gram.
Distribution of Diseases
❖ Sporadic
❖ Endemic
❖ Epidemic
❖ Pandemic
Appears only occasionally in one or at most a few members of the community ( ex. Tetanus and rabies).
Sporadic
There is a steady moderate level of disease in human population (Ex. Malaria in Palawan).
Endemic
There is a sudden outbreak or rise of incidence in human population (Ex. SARS-CoV and MERS-CoV )
Epidemic
When the disease have been disseminated in extensive area of the world (Ex. COVID-19, AIDS and HIV)
Pandemic
Pathophysiology and symptomology of parasitic infections.
❖ Traumatic or physical damage
❖ Lytic Necrosis
❖ Tissue reactions
❖ Toxic allergic phenomena
❖ Deprivation of the host’s essential nutrients and substances
When parasites invade the skin and other tissues causing destruction.
Traumatic tap or physical damage
It is a a skin infection caused by hookworms.
Creeping eruption
Secretory and excretory products elaborated by many parasites allow them to metabolize nutrients obtained from the host and store these for energy production.
Lytic necrosis
What enzyme does Entamoeba histolytica secretes to digest cellular materials and degrade epithelial basement membrane facilitating tissue invasion.
Cysteine proteinase
Cellular proliferation, white cell infiltration at the side of the parasite.
Tissue reactions
When proteins or other metabolites of the parasites are introduced into the body, there is sensation to the foreign substance, which may produce hypersensitization to anaphylactic shock. (ex. Punctuate keratitis)
Toxic allergic phenomena
The parasite competes with its host for the available supple of vitamin.
Deprivation of the host’s essential nutrients and substances
Parasite that competes on Vitamin B12
Diphyllobothrium latum
Factors that determine the intensity of parasitic infection.
❖ Topography of locality
❖ Social condition
❖ Age
❖ Hygienic measure
❖ Sewage disposal
❖ Water supply
Should consider when selecting a proper treatment.
❖ Antiparasitic medications
❖ Change in diet
❖ Vitamin supplements
❖ Fluid replacement
❖ Blood transfusion bed rest
Treatment
❖ Deworming
❖ Selective Treatment
❖ Targeted Treatment
❖ Universal Treatment
❖ Coverage
❖ Drug Resistance
❖ Efficacy
❖ Effectiveness
Use of anti-helminthic drugs in an individual or public health program.
Deworming
Usually expressed in percentage, number of previously positive subjects found to be egg-negative in examination of a stool or urine sample using a standard procedure at a set time after deworming.
Cure rate
Percentage fall in egg counts after deworming based on examination of a stool or urine sample using a standard procedure at a set time after deworming.
Egg Reduction Rate
Individual-level deworming with selection of treatment based on a diagnosis of an infection or based on presumptive grounds.
Selective Treatment
Group-level deworming where the risk group to be treated (with or without prior diagnosis) may be defined by age, gender or other social characteristics irrespective of infection status.
Targeted Treatment
Population-level deworming in which the community is treated irrespective of age, gender, infection status or other social characteristics.
Universal Treatment
Proportion of target population reached by an intervention.
Coverage
Genetically transmitted loss of susceptibility to a drug in a worm population that was previously sensitive to the appropriate therapeutic dose.
Drug Resistance
Effect of a drug against an infective agent in deal experimental conditions and isolated form of any context.
⮚ Performance of intervention under ideal or control circumstances mostly used in research or in trial.
⮚It answers the question Is the drug working or not?
Efficacy
Measure of the effect of a drug against infective agent in a particular host, living in a particular environment with specific ecological, immunological, and epidemiological determinants.
It answers the question Is the drug working or not? Is it effective or safe?
Effectiveness
Prevention and Control
❖ Morbidity Control
❖ Information-education-communication (IEC)
❖ Environmental management
❖ Environmental sanitation
❖ Sanitation
Avoidance of illness caused by infections, may be achieved by periodically deworming individuals or groups, known to be at risk of morbidity.
Targeted treatment may be given
Morbidity Control
Health education strategy that aims to encourage people to adapt and maintain healthy life practices.
Information-education-communication (IEC)
Planning, organization, performance and monitoring of activities for the modification and/or manipulation of environmental factors or their interaction with human beings
Preventing or minimizing vector and intermediate host propagation
Reducing contact between humans and the infective agent
Environmental management
Intervention to reduce environmental health risk.
Safe disposal and hygienic management of human and animal excreta, refuse and waste water.
Control of vectors, intermediate host and reservoir of diseases.
Provision of safe drinking water and food safety.
Housing that is adequate in terms of location, quality of shelter and indoor living conditions.
Facilities for personal and domestic hygiene.
Safe and healthy working conditions.
Environmental sanitation
Provision to access to adequate facilities for safe disposal of human excreta, usually combined with access to safe drinking water.
Sanitation
Eradication and Elimination
❖ Disease eradication
❖ Disease elimination
Permanent reduction to zero of the worldwide incidence of infection caused by a specific agent, as a result of deliberate effort. Once this is achieved, continued measures are no longer needed (ex. Smallpox)
Disease Eradication
Disease elimination: reduction to zero of the incidence of a specified disease in a defined geographical area as a result of deliberate effort. Continued intervention and surveillance are still required.
Disease Elimination
