Key Terminology & Definitions - Parasites Flashcards
Parasite
An organism that lives on or in another living organism (host), obtaining from it part or all its nutrition or needs of existence and imposing some degree of damage on host
Endoparasites
Parasites that live inside of host e.g. protozoa, helminths (worms)
Ectoparasites
Live on the host
Protozoan parasites
(Endoparasite) - Singe-celled, microscopic and motile, two taxonomic groups: excavata and alveolata
Obligate parasites
Excavata e.g.
Trypanosoma spp., leishmania spp., giardia spp., trichomonas spp.
Alveolata e.g.
Apicomplexa, babesia canis
Apicomplexa
Complete apical complex, obligate parasites, includes haematozoa (bloodborne) e.g. Plasmodium, leucytozoon, Babesia, Theileria, and coccidia e.g. Eimera, Toxoplasma
Helminth
Worm (endoparasite)
Trematode
Fluke (flat)
Cestode
Tapeworm (flat), segmented
Nematode
Roundworm
Direct lifecycle
One host e.g. Sarcoptes scabiei, ascaris (tick)
Indirect lifecycle
Two or more hosts, leishmania, echinococcus granulosus
Definitive host
Host in which the adult reaches maturity (& reproduces sexually)
Intermediate host
Host harbouring developing stages
Pathogenesis
The biological mechanism(s) leading to a diseased state; parasite pathogenesis = how a parasite infection causes disease
Dioecious
There are males and females e.g. nematodes
Miracidium
Life stage in which trematode infects snails
Cercariae
Life stage in which trematode is shed by snails
Metacercariae
Life stage that encysts on plants (trematode)
Diagenetic
Two or more generations in different hosts to complete the life cycle (trematodes)
Proglottid
Segment of cestode - become more mature as go down tapeworm
Parasite burden
Density of parasite
Commensal
Less damaging to completely benign relationship between two species (work together)
Symbiotic
Both species rely on each other for survival
Micropredator
Species that prey on tissues rather than whole organism
Arthropod
Mobile animals with jointed legs or limbs, poikilothermic, three main classes - acari, insects, crustacea
Poikilothermic
Cold-blooded
Acari
Mites and ticks
Insects
Lice, fleas, flies
Obligate
Completely parasitic, on host all times
Facultative
Can be free-living or parasitic e.g. Blowflies (‘fly strike’) usually feed on decaying meat but can infect live hosts by mistake (think host is decaying matter)
Permanent
Spends the entire life cycle on host e.g. lice, passive spread by host-to-host contact; treat host
Semi-permanent
Spends part of life cycle off of host (e.g. fleas), actively seeks host, treat host and/environment, stages off host are more prone to environmental stress
Clinical host
Supports survival and development of an ectoparasite with the presentation of associated adverse effects
Reservoir host
Supports survival and development of an ectoparasite without experiencing apparent adverse effects (don’t see clinical signs, just harbours host)
Transport host
Host provides environment to increase ectoparasite survivability off the clinical or reservoir host without development or adverse effects e.g. sheepdogs for sheep scab mites
Spiracles
Stigmata (opening)
Peritreme
Open canal/groove
Astigmata
Free-living frugivorous mites (skin and respiratory allergies), ecto or endoparasites, often found in stale animal feed (mites and ticks)
Stigmata, peritreme and tracheal system absent, breathe through cuticle (high moisture environment)
E.g. Otodectes, chrioptes, psoroptes
Prostigmata
Free-living and parasitic species (mites and ticks)
Stigmata located on gnathosoma (mouthparts), peritreme typically ‘M’-shaped
E.g. Cheyletiella, demodex, psorobia
Oribatidae
Free-living soil dwellers (‘beetle mites’) - have a shell, intermediate hosts of mammalian tapeworms (mites and ticks)
Stigmata hidden from view
Mesostigmata
Free-living predators, ectoparasites, often fast-moving (e.g. poultry red mites) (mites and ticks)
One pair of stigmata located laterally in region of coxae II and III, peritremes run laterally down side of mite, absorb H2O from environment, can live in dry environments
Ixodida (metastigmata)
Ticks, highly specialised blood-feeders
Stigmata situated on ventrolateral surfaces, posterior to coxae IV on a spiracular (astigmatic) plate
Mange
Skin disease caused by mites
Semi-permanent tick
Not always on host - vectors of disease, anaemia, paralysis
One host ticks
Rhipicephalus (Boophilus) spp.
Multi-host ticks
Ixodes spp. - infected from bloodmeal + whatever pathogen it’s vectoring remains in tick after it moults/in next stage
Vector ticks
Trans-stadial, trans-ovarial - when adult female becomes infected by feeding + pathogen affects progeny when eggs produced
Argasid ticks
Legs don’t usually extend past the confines of the body (soft tick)
Ixodes ticks
Head and legs are easily seen (head sticks out) (hard tick)
Scutum
Hardshell of ticks
Pthiraptera
Lice - permanent parasites (spend whole life cycle on host)
Pediculosis
Disease caused by lice
Bloodsucking lice
Vectors of disease (not via feeding - pathogen is passed in faeces and rubbed into wounds inflicted by scratching), transmit typhus in humans, rickettsia in animals, sensitive to systemic insecticides
Narrow head than body, thorax is ‘A’ shaped
Chewing lice
Not prone to systemic insecticide
Broader head compared to body
Siphonaptera
Fleas - semi-permanent, blood-sucking, vectors of disease e.g. myxomatosis in rabbits, cannot jump repeatedly in rapid succession (must restore energy in between)
Complete metamorphosis
Adult and larva look completely different
Nidicolous
Associated with nest-dwelling animals
Flies
Semi-permanent parasites, blood-sucking, secretophagous (especially eyes and nose) and or myiaisis
Myiaisis
Infestation of living tissue by larvae (maggots of true flies (Diptera)
Obligate flies
Larvae must infest living tissue e.g. warble flies (Hypoderma spp.), horse bots (Gasterophilus spp.), sheep nasal bots (Oestrus ovis)
Facultative flies
Usually only infect dead tissue but can cause bystander live tissue damage (gets confused) e.g. Sheep blowfly strike (Lucilia spp. - green bottle)
Accidental flies
Usually not a parasite of living tissue e.g. hoverfly and crane fly larvae
Crustacea
Fish ‘lice’ e.g. Lepeophtheirus salmonis and Caligus elongatus
