CHAPTER 1: Introduction to Medical Parasitology and Basic Terminologies

Parasitology

________________ is the study of parasites and is traditionally limited to parasitic protozoa, helminths and arthropods. It is the area of science which deals with the study of organisms that lives within the body of another organism for survival. 

Human parasitology

______________ is focused on medical parasites and includes their morphology, life cycle, and the relationship with host and environment. 

Endoparasites

_______________ live within the host. They may be obligate parasites (dependent on their hosts and cannot live without the host), facultative parasites, and accidental parasites.

Ectoparasites

______________ are parasites which live on the outer surface of the host.

Definitive or final host

____________ is the one which harbors the adult parasite and where the parasite reproduces sexually. 

Intermediate host

______________ is the host which harbors the larval stage or the asexual forms of the parasite.

Predation

_______________ it may attack another living animal, consuming part or all of its body for nourishment. The attacker is the predator, and the victim is called the prey. 

Scavenging

__________________ an animal deriving its nutrition from already dead animals, either devouring those dead of natural causes or taking the leavings of a predator.

Symbiosis

______________ (living together) this refers to association of two species for food and shelter. Different forms of symbiosis may be distinguished on the basis of whether or not the association is detrimental to one of the two partners.

Commensalism  

____________ latin for “eating at the same table”, denotes an association that is beneficial to one partner and at least not disadvantageous to the other. 

Entamoeba coli that lives in the lumen of the intestine, subsists there on the bacterial flora of the gut, and does its host no appreciable harm.

Example of Commensalism:

Mutualism

______________ a specialized type of symbiosis that occurs when associations are beneficial to both organisms. 

Parasitism

_____________ symbiotic relationship in which one animal, the parasite lives at the expense of the other animal, the host. 

MEDICAL PARASITOLOGY 

_______________ is a branch of biology that is focused on the animal parasites of human and their medical significance and public health impact. It also covers phenomena of dependence among living organisms. 

Host

____________ is known as the organism that provides physical protection and nourishment to the parasite. 

Human

______________ is definitive host for lymphatic filarial worms that cause elephantiasis and trypanosomes that cause African trypanosomiasis.

Anopheles mosquito

___________ is the definitive host for Plasmodium spp. that causes malaria.

Intermediate host

_____________ harbors the larval stages or asexual forms of the parasites.  

First intermediate host (1st IH)

______________ harbors the early larval stage of the parasites. 

Snail

__________ is an intermediate of all the trematodes.

Vector 

____________ is a blood feeding arthropod. The term mechanical vector is used to describe a vector which assists in the transfer of a parasitic form between hosts but is not essential in the life cycle of a parasite. This means that no parasitic development occurs in the vector. 

Vector

No parasitic development occurs in the _________.  

Mechanical Vector

A good example of a __________ is a fly that transfers amoebic cysts from infected feces to food/drink that is consumed by humans.

Transport or Paratenic host

Non-arthro pods mechanical vector is called ____________. In such a host, a parasite remains viable but does not develop.

Second intermediate host (2nd IH)

______________ harbors the infective larval stage of the parasite.

snail, fish, vegetable, crabs, ants

Examples of Second Intermediate Host (2nd IH)

Paratenic host 

 

______________ harbors the parasite in an underdeveloped or in arrested state of development. It will only continue the life cycle of parasite only if this paratenic host carrying the parasite is consumed by a susceptible definitive host. 

Reservoir host 

_____________ is an alternative host to a parasite that is harbored normally by humans. Host continues the life cycle of the parasite and acts as an additional source of infection. Must be considered in parasite control measures.

Balantidium coli.

Pigs are known reservoir host of ____________.

Zoonosis

A parasitic infection in which the normal host is an animal but can produce disease in human if they become infected accidentally is known as _________.

PARASITE

___________ these are organisms that depend on the host for survival. 

Obligate parasite

_____________ organism that cannot survive in any other manner in the absence of a host.  Parasites that can’t survive without a host

Facultative parasite

_______________ organism that may exist in a free-living state or as a commensal and that, if opportunity presents itself, may become parasitic. Parasites that can live with or without a host

Temporary parasite

________________ parasites that are obligatory at one or more stages of their life cycles but free living at others. 

Intermittent parasite

______________ small organisms, such as mosquitoes, which must periodically seek out other and larger forms on which to nourish themselves. These are parasites that visit their host during feeding time. 

Endoparasites

____________ are parasites living within the host. 

Ectoparasites

_____________ are parasites that are found on the surface of the body.

Pathogenic

_____________ those that can cause diseases, and those that can inflict injury to the host.

Non-Pathogenic / Commensal

_____________ those unable to cause any disease

Zoonotic

____________ animal parasites/ non-human parasites that can also infect man

Erratic

_____________ parasite that becomes fixed in an unusual organ different from that which it ordinary parasitize. 

Incidental

___________ one that establishes itself in the host in which in does not ordinary live

Permanent

_____________ those found within the host from early life to maturity

Transitory

___________ type of parasite wherein the larval stage develops in a host while the adult is free living.

Periodic

__________ type of parasite wherein the larval stage develops in a host different from that of adult. 

ENDEMIC

____________ there is a steady, moderate level of disease in human population.

PANDEMIC

____________ when communicable disease has been disseminated over an extensive area of the world.

Infection

______________ invasion made by endoparasites

Infestation

_____________ invasion made by ectoparasites

Infective stage

_____________ morphologic form that invades humans

Diagnostic stage

______________ forms that can be detected via laboratory retrieval methods

Carrier

______________ usually an individual harboring the parasite but does not show any signs and symptoms, it is a state wherein the parasite lives in or on the tissues of its host without causing evident harm.

Epidemic

___________ there is a sudden rise in the incidence or an outbreak of considerable intensity occurs in a disease in human population.