Parasitology Exam 1

Parasitology

The study of a parasite (Organism 1) and its relationship to its host (Organism 2)

Symbiosis

the living together in more or less intimate association or close union of two dissimilar organisms

Mutualism

an interaction between two or more species where each species has a net benefit (+,+)

Commensalism

an association between two organisms in which one benefits and the other derives neither benefit nor harm (+,0)

Parasitism

a relationship between species, where one organism, the parasite, lives on or in another organism, the host, causing it some harm, and is adapted structurally to this way of life (+,-)

Mutualism Example

food (bird) and dental hygiene (alligator) (+,+)

Commensalism Example

food (pilot fish) and (shark) nothing (+,0)

Parasitism Example

food (tick) and blood lose and pathology (human)

Facultative

type of parasite - an organism that may resort to a parasitic lifestyle, however, it does may not rely on a host for completion of its life cycle, type of parasite

Obligatory

type of parasite - a parasitic organism is one that cannot complete its lifecycle without a relationship with a suitable host

Endo-parasite

type of parasite - a parasite that lives within a host and causes an infection

Ecto-parasite

type of parasite – a parasite that lives on a host and causes an infestation

Definitive

a host that supports the adult or sexually reproductive stage of a parasite. This stage is necessary for parasite survival.

Intermediate

a host that supports the immature or non-sexual reproductive forms of a parasite. There may be asexual reproduction. This stage is necessary for parasite survival.

Transfer

a host that can move or relocate parasite stages from one location another – most often reproductive stages such as eggs. Insects such as flies and cockroaches are good transfer host.

Vector

a host that acts as an definitive or intermediate host for a parasite, but more importantly transfers the parasite to the next host. Good examples of vectors are the mosquito in transmitting malaria and ticks in transferring Lyme disease

Reservoir

a host that serves as a source of infection and potential reinfection of humans, and as a means of sustaining a parasite within a population and ecosystem

Exposure

being in contact with an infectious organism

Colonization

the presence of an infectious agent (bacteria) on / in a body surface (like on the skin, mouth, intestines or airway) without causing disease in the person

Infection

the invasion and growth of infectious agents germs on / in the body

Sign

a sign is any objective evidence of a disease that can be observed by others (for example a skin rash, lump, fever, pulse, blood pressure)

Symptom

a symptom is subjective evidence of a disease, that is, apparent only to the patient (for example back pain or fatigue)

Incubation Period

the period between exposure to an infection and the appearance of the first signs and symptoms

Latency

the time from infection to infectiousness or being able to pass the infection

Infectivity

ability of an organism to establish an infection

Invasiveness

ability of an organism to spread to adjacent or distant tissues

Pathogenicity

ability to produce substances that damage tissues, e.g. toxins

Utilization of Host Food

Rare – Most parasites do not feed on food you ingest they feed on you

Destruction of Host Tissue Through Feeding

Blood feeders – Hookworms

Lytic necrosis

Destruction of Host Tissues, Digestion of tissue – Entamoeba hystolytica

Traumatic damage

Destruction of Host Tissues, Mechanical damage to host tissue

Obstruction of Lumen

Destruction of Host Tissues, Blockage of tubes within the body

Obstruction of Lumen Example

Ascaris lumbricoides - Small Intestine and Bile Duct

Penetration of Host Tissues Example

E. histolytica

White blood cells

Increased production of WBCs as a result of parasite induced inflammation

Eosinophilia

Increased production of eosinophils, a white blood cells, that is part of host defence against parasitic infections

Erythropoiesis

Increased production of red blood cells due to anaemia caused by parasite feeding

Neoplasia

Uncontrolled proliferation of cells due to excessive parasite induced tissue damage and repair

Parasite Density and Distribution

Flora, Fauna, Water

Entamoeba histolytica

nuclear division in cyst stage versus normal division in pond Amoeba

Nematodes

Roundworms

Cestodes

Tapeworms

Trematodes

Flukes

(Protozoan) Amoeba

Sarcodina

Ciliates

Ciliata

Flagellates

Mastogophora

Sporozoans

Sporozoa

Enterobius vermicularis

Pinworm

Trichuris trichiura

Whipworm

Ascaris lumbricoides

Giant Roundworm

Toxocara canis/cati

Dog/Cat Roundworm

Baylisascaris procyonis

Raccoon Roundworm

Ancylostoma duodenale

Hookworm

Ancylostoma caninum

Hookworm

Necator americanus

Hookworm

Strongyloides stercoralis

Threadworm

Trichinella spiralis

Pork Roundworm

Dirofilaria immitis

Heartworm

Loa Loa

Eye Worm

Wuchereria bancrofti

Causes Elephantiasis

Onchocerca volvulus

Causes River Blindness

Dracunculus medinensis

Firey Serpent/Guinea Worm