The Language of Parasitology Flashcards
Symbiosis
association (temporary or permanent) between two organisms of different species; each member is called a symbiont
List the 5 types of symbiont relationships
Predator-prey Phoresis Mutualism Commensalism Parasitism
Predator-prey
short term relationship in which one symbiont benefits at the expense of another (ex. tiger and water buffalo)
Phoresis
relationship in which the smaller member of the relationship is mechanically carried about by the larger member (ex. bacterium Moraxella bovis carried by facefly Musca autumnalis)
Mutualism
association between two organisms of different species in which both are benefitted (ex. tick birds on rhinos; ciliate in rumen of cow)
Commensalism
association between two organisms of different species in which one partner is neither benefitted nor harmed (ex. sharks and remoras)
Parasitism
association between two organisms of different species in which one member (the parasite) lives on or in the other member (the host) and may cause harm; parasitism implies metabolic dependency
Parasitiasis
association between two organisms of different species in which one organism is potentially pathogenic, but does not cause outward signs of disease (ex. healthy cattle on pasture harbor GI parasites, but do not exhibit outward signs)
Parasitosis
association between two organisms of different species in which one organism injures the other and produces outward signs of disease (ex. emaciated cow exhibits outward signs of parasitism)
Parasitology
the study of parasitic relationships
Endoparasite
parasite that lives within the body of the host (ex. Dirofilaria immitis- heartworm)
Ectoparasite
parasite that lives on the outside of the body of the host (ex. fleas and ticks)
Erratic/Aberrant parasite
parasite that has wandered into an organ or tissue in which it does not normally live
Incidental parasite
parasite in a host which it does not usually live
Facultative parasite
organism that is capable of living either free or as a parasite
Obligatory parasite
organism that must live a parasitic existence
Periodic parasite
parasite that makes short visits to its host to obtain nourishment or other benefit
Pseudoparasite
object that is mistaken for a parasite (ex. pollen grain on a fecal)
Life cycle
development of a parasite through its various life stages
Definitive host
the host that harbors the adult, sexual or mature stages of the parasite
Intermediate host
host that harbors the larval, asexual, or immature stages of the parasite
First intermediate host
first host parasitized by the larval stages of the parasite
Second intermediate host
second host parasitized by the larval stages of the parasite
Transport/Paratenic host
host in which the parasite does not undergo any further development, usually remaining encysted until eaten by the definitive host
Reservoir host
vertebrate host in which a parasite (or disease) occurs naturally and which is a source of infection for human beings and their domestic animals
Infection
parasitism by an internal parasite
Infestation
parasitism by an external parasite
Homoxenous/monoxenous parasite
a parasite that has only one type of host- the definitive host
Heteroxenous parasite
parasite that has more than one type of host- the definitive host and one or more intermediate hosts
Stenoxenous parasite
parasite that has a narrow host range (ex. Eimeria tenella will only infect chickens)
Euryxenous parasite
parasite that has a wide host range (ex. Toxoplasma gondii will infect over 300+ species of mammals)
Hyperparasitism
parasite infecting parasites (ex. Dirofilaria immitis microfilariae in a mosquito)
Zoonosis
any disease that is transmissable from lower animals to human beings
Prepatent period
time from infection of a parasite until diagnostic stages can be recovered from the host (i.e. eggs, oocysts, cysts, larvae, trophozoites) generally recovered from feces, urine or blood (in definitive host)
Hypobiosis
the ability of nematodes to arrest their development and go dormant for a variable period of time
Direct lifecycle
there is no intermediate host, only the definitive host
Indirect lifecycle
there is one or more intermediate hosts
Scientific name
comprised of two Latin words, and is usually written in italics or underlined; the first word is capitalized and is the Genus name, and indicates the group to which a particular type of animal belongs; the second word is not capitalized and is the specific epithet and indicates the type of animal itself
ex. dog- Canis familiaris; cat- Felis catus; housefly- Musca domestica; heartworm- Dirofilaria immitis
List ways parasites injure their hosts
- feed on blood, lymph or exudates (ex. lice,tick)
- feed on solid tissues, directly or after liquefying them (ex. fluke)
- compete with host for food host ingested, either by ingesting the intestinal contents or by absorbing them through the body wall (ex. tapeworms)
- mechanical obstruction of the intestine, bile ducts, blood vessels, lymph channels, bronchi, or other body channels (ex. heartworms)
- produce pressure atrophy (ex. parasite that resides in kidney)
- destroy host cells by growing inside them (ex. apicomplexans)
- produce various toxic substances, such as hemolysins, histolysins, and anticoagulants (ex. ticks)
- produce allergic reactions (ex. fleas)
- produce various host reactions such as inflammation, hypertrophy, hyperplasia and nodule formation
- (directly or indirectly) promote the neoplastic transformation of cells (ex. Spirocerca lupi- osteosarcoma)
- carry diseases and other parasites including malaria, swine influenza, salmon poisoning, and heartworm (ex. mosquito)
- reduce host’s resistance to other parasites and to other diseases (ex. Criptosporidium)
List types of parasites
Protozoa
- Amoebas
- Ciliates (found in pigs/rumen in ruminants-beneficial)
- Flagellates (Giardia)
- Apicomplexans (Coccidia)
Helminths
- Platyhelminths (flatworms)
- Nematodes (roundworms)
- Acanthocephalans
Arthropods
- Insects*
- Acarines*
- Pentastomes (mostly found in snakes/reptiles)
- Crustacea (fish lice)
Types of zoonotic cycles
Sylvatic: involve parasites of wild animals
urban/domestic: involve parasites of companion animals
Evolution of parasitism
2 general methods:
parasite evolves with the host (less likely to be pathogenic)
parasite recently colonized the host (more likely to be pathogenic)
Patterns of parasitism
Overdispersion
Increased susceptibility
The host environment
Overdispersion
not all animals in a herd harbor the same number of parasites
Increased susceptibility
based on factors such as age, immune status, mother/pregnancy
Host environment
how parasites escape immunity
- molecular mimicry: mimic self epitope
- antigenic variation: express new surface proteins
- secretion of substances that disable the local immune response: helminths secrete proteins such as proteases/protease inhibitors; adult flukes secrete thoredoxin peroxidase which stimulates alternative activation of macrophages
List external factors that affect a parasites ability to infect the host.
- Parasites ability to survive outside of intermediate/direct host
- Intermediate host being present in the local environment
List 2 ways parasites try to increase the likelihood of completing their life cycle/make it to direct host.
- Produce large number of eggs
- hermaphroditism
- asexual reproduction
- change behavior of intermediate host to make IH more susceptible to ingestion by DH
List potential routes of transmission of parasites and give examples
- Oral route- eggs (Toxascaris leonina)
1a. Oral route- intermediate host (coprophagous flies with Draschia sp. larvae)
1b. Oral route- transmammary route (Ancylostoma caninum-hookworms) - In utero- Toxocara canis
- Vector bourne transmission- Dirofilaria immitis (Heartworm)
- Skin penetration- Ancylostoma caninum (Hookworms)
List ways parasites use to stay in place.
Suckers Hooks Spines "Take a huge bite" (oral attachment) Claws (endoparasites)
Site specificity
Some parasites may be more or less specific about the site within the host they infect
- Generalists can use nearly any tissue
- some parasites utilize niche partitioning
- specialization in different parts of the gut (reduces competition among parasites)
