Intro to Parasitology

Symbiosis, 5 types

Living together

Predator/prey

short term relationship one benefits at expense at other

Phoresis

smaller member of relationship is mechanically carried by larger

Mutualism

both organisms benefit

Commensalism

one benefits, other is neither benefitted nor harmed

Parasitism

two organisms of different species, one lives on or in the other member and may cause harm

what is a parasite?

smaller organism that lives on or in at the expensive of a larger organism called the host

infection

may be caused by parasite within body

infestation

outside/on body or in the environment

ectoparasite

parasite lives outside/on body of host

endoparasite

parasite lives within body of host

how is host affected?

expense may be trivial, substantial, or unbearable

how is hosts expense determined by?

number of parasites, kind and degree of damage parasite inflict, vigor or nourishment of host

multiple parasitism

parasites of different species infest/infect animal

superparasitism

excessive parasitization of the same species

erratic or aberrant parasite

when parasite wanders from usual site of infection into organ or location it doesn’t normally live

aberrant parasites

may not be able to survive or migrate abnormally if enter wrong host

aberrant parasites effect

may cause an over reaction in body of wrong host, serious disease can result

incidental parasite

when a parasite occurs in host that it normally does not live

obligatory parasite

a parasite that must lead a parasitic existence, not capable of leading free living

periodic parasite

parasite that does not live on or in host

makes short frequent visits to obtain nourishment

pseudoparasite

living creatures or objects mistaken for parasites

definitive host

host that harbors adult, mature stage of parasite

intermediate host

host that harbors larval, juvenile, immature or asexual stage of parasite

life cycles and transmission of parasites?

describes how organism develops from immature stage to adult

parasite life cycle

some produce live young and others produce eggs

one celled parasite life cycle

may reproduce by dividing into 2 identical parts

direct life cycle

immature form of parasite can infect same host it came from

indirect life style

immature form of parasite must past through intermediate host before it can infect def host

transport hosts

intermediate host where no development occurs

ex) rodents can transport roundworms to dogs/cats

migration → somatic/trachael

parasites with life cycles that include phase of migrating through body

ex) hookworms lung → system → tissues

zoonoses

infections can be passed from animals to humans

sometimes humans have same symptoms of dog and cat

prepatent period

infection to detection

cannot be tested until incubation period over

incubation period

time from when parasite enters host and develop of symptoms occur

infect until symptoms

major classes of parasites

helminths, arthropods, protozoa

helminths - “worms”

nematodes

tapeworms

flukes

arthropods

insects

arachnids

nematodes characteristics

are round in cross section, long, unsegmented

variety of lengths

sig cause of disease in dogs and cats

varied life cycles

tapeworms

flat worms that are segmented

head has suckers or grooves attach to animal intestine

each segment has own reproductive organs

no digestive system

intermediate host

flukes

• flat, leaf shaped

• suckers, hooks attach to organs

• eggs have trapdoor → operculum

• dog and cat flukes have indirect life cycles

• generally do not cause srs issues unless high numbers

arthropods

• jointed legs

• include insects and arachnids

insects

• 70% of all known species of animals

• have antennae, compound eyes and body

• many have wings

arachnids

• include ticks and mites

• carnivores feeding on tissue and blood

protozoa

• over 450,000 species

• composed of nucleus and cytoplasm

• may move with assistance of flagella

• 
  

• ex. giardia