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93 Cards in this Set
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- Back
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Define Parasite
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smaller organism that lives on or in and at the expense of a larger organism called the host
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What differentiates parasites from bacteria/viruses/fungi?
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No replication in primary host for most helminths, there is also a metabolic dependence on the host
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What determines the disease state?
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Number and pathogenicity of the parasite
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What are the three types of infection?
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1) no effect on host
2) subclinical infection: no obvious signs, slight decrease in performance 3) clinical infection: disease manifestation |
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What is clinical judgement?
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Is the effect on the host important enough to justify treatment
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How is classification done?
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By morphology
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What are the characteristics of Helminths?
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Multicellular, soft body
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What are the three genus' of helminths?
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1) Nematoda
2) Trematoda 3) Cestoda |
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Describe Nematoda
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(Helminth: multicellular, soft body)
Body cavity pass-through alimentary canal surface cuticle male and female Round worms |
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What do 'round worms' belong to?
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Helminths (multicellular, soft body)
Nematoda (pass through alimentary, body cavity, male/female, surface cuticle) |
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Describe Trematoda
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(Helminth: soft body, multicellular)
no body cavity blind pouch digestive tract surface tegument mostly hermaphroditic (Flukes) |
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What do 'flukes' belong to?
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Helminth (multicellular, soft body)
Trematoda (hermaphrodites, blind pouch digestive, surface tegument, no body cavity) |
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Describe Cestoda
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(Helminth: multicellular, soft body)
no body cavity no digestive tract surface tegument all are hermaphroditic (Tapeworms) |
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What do 'tapeworms' belong to?
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(Helminths: multicellular, soft body)
Cestoda (all hermaphrodites, no digestive, no body cavity, surface tegument) |
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Which helminths have a body cavity?
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Nematoda (roundworms)
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Which helminths have a digestive tract?
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Nematoda (pass through)- roundworms
Trematoda (blind pouch)- flukes |
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Which helminths have male/female?
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Nematoda (roundworms)
Trematoda (some, flukes) |
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Which helminths are hermaphrodites?
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All Cestoda (tapeworms)
Most Trematoda (flukes) |
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Which helminths have surface tegument?
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Trematoda (flukes)
Cestoda (tape worms) |
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What are the characteristics of protozoa?
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Unicellular
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What are the platyhelminths?
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Trematoda (flukes)
Cestoda (tapeworms) |
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What are the genus' of protozoa?
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Apicomplexa (coccidians, hemosporidians)
Sarcomastigophora (mastigophora) Ciliophora (ciliates) Sarcodina (amoebas) |
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Describe Apicomplexa
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(Protozoa- unicellular)
coccidians and hemosporidians (Malaria) |
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Describe Sarcomastigophora
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(Protozoa- unicellular)
mastigophora (Giardia) |
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Describe Ciliophora
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(Protozoa- unicellular)
ciliates |
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Describe Sarcodina
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(Protozoa- unicellular)
Amoebas |
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What are the characteristics of arthropods?
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chitinous exoskeleton
usually with legs |
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Describe genus Arachnida
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(Arthropod- chitinous exoskeleton, legs)
Adults- 8 legs Mites- lateral stigmata absent or variable Ticks- blood suckers, lateral stigmata |
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Describe Mites
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Arthropod (chitinous exoskeleton), Arachnida (8 legged adult)
Lateral stigmata absent or variable |
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Describe Ticks
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Athropod (chitinous exoskeleton)
Arachnida (8 legged adult) Lateral stigmata behind 4th leg |
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Describe genus Insecta
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(Arthropod- chitinous exoskeleton)
Adult has six legs Lice Fleas True bugs Flies/mosquitos |
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Describe Lice
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Arthropod (chitinous exoskeleton)
Insecta (adult has 6 legs) Chewing (mallophaga) or sucking (anoplura) |
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What does anoplura mean?
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Sucking form of lice
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What does mallophaga mean?
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Chewing form of lice
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What is the importance on knowing life cycles of parasites?
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1- control of disease
2- diagnosis 3- prediction of disease 4- cross host-species infection 5- environmental management 6- when to treat/repeat treatment |
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Define prepatent
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time before sexual maturity and generation of offspring by parasite in its host
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Define patent
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an infection where sexually mature parasites are generating offspring
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Define Larval stage
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sexually immature form of parasite
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Define Adult stage
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sexually mature form of parasite
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Define Primary/definitive host
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animal infected by the adult stage parasite
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Define intermediate host
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animal infected by larval stage that continue development but do not mature to adult stage in that animal
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Define paratenic host
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"Transporter host". Animal infected by a larval stage that does not proceed in development
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Define larval migration
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movement of immature stage within the tissues of a host
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Define Direct life cycle
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parasite does NOT require an intermediate host
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Define Indirect life cycle
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parasite DOES require an intermediate host
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Describe a Direct life cycle
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No intermediate host
Free living or no free-living |
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What is a free living cycle?
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Form of direct life cycle
motile form of parasite outside of host |
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What is a non free-living cycle?
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Form of direct life cycle
sessile form of the parasite, usually in egg |
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Describe an Indirect life cycle
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Requires an intermediate host
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What is a vector?
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Not necessarily a required intermediate host
Either mechanical or biological (living, supports infective stage in some way) |
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What kind of life cycle is Dirofilaria immitis?
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Indirect life cycle (mosquitos)
Dirofilaria immitis =heartworm |
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Nematodes have which kind of life cycle?
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Direct life cycle
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Describe a free living cycle of a nematode
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Direct life cycle
Egg hatches to L1, L1-3 molt and grow free in the environment outside of host, L3 infects host |
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Describe a non-free living life cycle of a nematode
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Direct life cycle, no free living:
Egg containing either L1/2 infects host, resistant eggs accumulate in environment, larvae released from egg inside host |
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Describe an indirect life cycle of a nematode
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MUST have appropriate intermediate host for development of L3 infective larval stage.
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Can you infect a dog with heartworm from a blood transfusion?
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NO! there would not be any infective larva in the blood, these mature in the indirect host (mosquitos)
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Which nematodes have no stages external to the host?
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Trichinella
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Which nematodes have replicating free living stages?
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Strongyloides
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What kind of life cycle do Trematodes have?
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Digeneic life cycle
All trematodes infecting warm blooded animals absolutely require a Snail as an intermediate host |
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What do Trematodes use as an intermediate host?
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Snails
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Describe the life cycle of a trematode
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Infected animal has adult fluke (hermaphrodite) -> fluke sheds ova in feces -> ova turns into a motile stage and infects snail -> asexual replication within snail releases spores -> motile form exits snail and lives on vegetation and is ingested by host
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What kind of life cycle do Cestodes have?
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All require intermediate hosts
INDIRECT life cycle |
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What determines the timing or treatment and retreatment?
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The time required for development to adult, egg laying/larva producing stage determines.
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What determines the parameters of environmental management?
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The time require for development of pre-infective stages to infective stages
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What is the general cycle for all helminths?
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1) Contamination of hosts environment (habitat or food source)
2) Development of parasite preinfective stages (fresh dog feces dangerous?) 3) Infection 4) Maturation of adult parasitic stage (prepatent time) |
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What are usually the definitive hosts in Cestodes?
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Definitive host is often a predator of the intermediate host
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Define Pseudocoelom
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Body cavity, fluid filled under pressure, used so worm can move when muscles contract
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What are the dorsal and ventral cords for?
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Major nerves
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What are the lateral cords for?
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Excretory system
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What do most antihelmintics target?
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nerves of the dorsal and ventral cords
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Describe the buccal cavity of nematodes
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with or without teeth, can be well developed or vestigial
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Dscribe the rhabditiform esophagus
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Rhabditiform: extra structure on top
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Strongyliform Esophagus
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Most of adult strongydida
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Filariform
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Single tube associated with infective larval stages of nematodes and parasitic form of strongylodes, differentiates strongylodes and trich
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Describe the intestine of a nematode
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A straight tube, no bends
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How do nematodes reproduce?
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There are males and females
Males grasp females and use spicules to transport sperm |
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Describe the female reproductive tract of a nematode
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Females are larger than males
Long, tubular winding reproductive tract, location of opening can vary |
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Describe the copulatory bursa in male nematodes
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varies from vestigial to well developed by genus, used to grasp the female
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Describe the order Rhabditida
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Free living generation
Sexual replication Have rhabditiform esophagus Adults less than 10 mm |
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How do first/second stage larva differ from third stage and parasitic females
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1st/2nd: rhabditiform esophagus
3rd/parasitic females: filariform esophagus |
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What is exclusive to Strongyloides of the nematodes?
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A sexually reproducing free-living stage
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What kind of esophagus would be in free living Strongyloides adults?
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Rhabditiform
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What kind of esophagus would be in parasitic adult Strongyloides females
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Filariform
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What is the difference between heterogenic and homogenic?
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Heterogenic: in environment replication
Homogenic: in host |
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Describe the life cycle of Rhabditis strongyloides
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Free living soil nematode
Replicates in manure Larva can penetrate epidermis Clinical signs: like mites but can see larvae on scrapings of lesions |
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What is unique about Strongyloides in man, dog and cat?
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L1 larvae are found alive in the feces, which allows for auto-infection to occur
This leads to hyprinfection |
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How can hyperinfection occur?
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When the ova hatch in the intestines and reinfect the animal without leaving, auto-infection
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What kind of cycle is seen in autoinfection?
What kind of cycle from Strongyloides in animals other than dogs, cat, man? |
Autoinfection= homogonic
Heterogonic cycle in other species, as eggs don't hatch prior to defecation |
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Which cycle leads to an increase in infective L3 larvae in the environment?
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Heterogonic
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How is Rhabditida strongyloides transmitted?
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2 ways:
Lactogenically: through milk Transdermally: through skin |
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What is the risk of immunosuppresants if the animal has Strongyloides?
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Immunosuppressed adult host is susceptible to hyperinfection and clinical signs
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Which animals express clinical signs of strongyloides?
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Neonatal and young animals; immunosuppressed animals
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What is the source of environmental contamination with Rhabditida Strongyloides?
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Young animals
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