Parasitology Flashcards
Classification of parasites
Predator
Obligate
Facultative
Temporary
Accidental/incidental
-spurious
-erratic
-host specificity
Predator
Organism that attacks another living animal not necessarily killing them(attacker)
Obligate
Cannot exist without host
Facultative
Not entirely dependent on host for survival - opportunistic
Temporary
A parasite that lives for only part of its life on host
Accidental/incidental
Appears in unusual host
Spurious
Pass through the digestive system without affecting host (may be unknown to its presence)
Erratic
Wander and reach into organs in which not usually found due to potential boroughing or laying dormant
Host specificity
Parasite can only utilise a certain range of hosts
Host types
Intermediate host
Paratenic/transport/carrier host
Reservoir host
Definitive host
Accidental host
Compromised host
Host specificity
Vector
Intermediate host
Parasite needs to spend part its life in intermediate host which may get ingested by final destination to sexually mature
Paratenic/transport/carrier host
Take advantage of another host not wanting to kill /harm in order to survive for wider goal
Reservoir host
Remain alive and can develop but don’t want to kill it or harm it as not end goal
Definitive host
Final host where they want to be (dog cat pets etc) reach sexual maturity and reproduce
Accidental host
Not expecting to find the host can survive partly
Compromised host
Old, young, human - opportunistic parasites
Host specificity
Host is specific to that parasite
Horse lice on horse
Vector
Disease transmitter living organisms
Symbiosis
2 closely living organisms
Parasitism
Symbiotic relationship - one is of detrimental health to other
Non mutual relationships
Symbiont
Smaller of the two (symbiosis) usually the parasite
What are the different relativist symbionts have
Commensalism
Mutualism
Parasitism
Predation
Commensalism
One benefits from the other without harming host
Example - vultures eating carcasses and disease (clean up crew)
Mutualism
Both host and symbiont are benefiting
Example - ox pecker eating bugs off rhinos
Predation
Host is negatively impacted and can be killed by symbiont
Parasitism
Host negatively impacted by symbiont but does not die
Example - fleas and ticks
Parasite transmission types
Passive
Active
Inoculative
Passive transmission
Parasite doesn’t travel to host
May eat contaminated food/water
Accidental ingestion
Active transmission
Move to host like fleas
Inoculative transmission
Inject / blood suckers carry the disease
Malaria with mosquitos
Lime disease with ticks
Location and time spent on the host
Ectoparasite - Infestation
Endoparasite - infection
Extracellular parasite (endo parasite)
Live on or within host tissue
Intracellular parasite (endoparasite)
Live inside a host cell
Harmful effects of parasites
Blood loss
Hypersensitivity (sweet itch)
Toxicity (maggots)
Cutaneous lesions (secondary invasion of pathogens)
Disease transmission
Irritation (behaviour/itchy)
Interference with human animal bond
Life cycle of parasites
The entire sequence of stages in the life of a parasite from adults of one generation to adults of the next
Direct life cycle - lives on one moves to another
Indirect life cycles - intermediate host needed to grow first
3 main groups of Ectoparasites in uk
Fleas
Ticks
Mites (Mosquitos and lice also part of insect group)
Temporary Ectoparasite
Visit host for food then leave
Ticks flies midges mosquitos
Stationary Ectoparasite
Spend some time in host but may not spend all their life on the same one
Ticks egg
Permanent Ectoparasite
Live permanently on host lice and mites
Arthropods Ectoparasite
Joined appendages
Exoskeleton - chitin
3 classes of arthropods
Class Crustacean - crustacean - no parasites
Class arachnida - arachnids (spiders) ticks also
Class insecta - insects - fleas flies mosquitos mites and lice
Insects - lice
Wingless
Permanent parasite
Dorsoventrally flattened
Claw for clasping feathers/hair
Host specific
Sucking type lice
Elongated head
Narrow mouth parts for piercing skin and sucking blood
Biting lice
Broad head
Mouthparts adapted to chewing
Lice lifecycles
4-6 week
Passed by direct contact with infested host
Adult lice live on host at all times
Adult lice lay eggs called nits that stick to hair
Nit develops to immature adult (nymph) then adult
Lice epidemiology
Highly host specific
Transmission is host to host contact/sharing brushes
Clinical signs of lice
Poor coat appearance
Presence of eggs/lice
Restlessness bad temper and itchy
Alopecia and skin lesions dermatitis
Lice diagnosis
Visual detection
Lice treatment and prevention
Licensed insecticide
Wash all equipment/bedding etc
Fleas - insects
Wingless
Laterally flattened
Dark brown
1-6mm long
Rapid movers through coat
Ability to jump (specialised legs)
Mouthparts adapted for piercing skin and sucking blood
Head detail is characteristic of the species
Some species are host specific
Life cycle of fleas
12-14 days (can extend to 140days)
Adult fleas seek host
Mate and feed on host (lay eggs)30 eggs/ days
Eggs fall off host
Larva spins cocoon off host
Pupal stage cocoon
Adult flee emerges in response to vibrations and CO2
Epidemiology fleas
Host specific
Pre emerged fleas highly protected from environmental conditions
Emergence depends on presence of appropriate stimuli and can be rapid
Clinical signs of fleas
Variable - itchy/dermatitis
Fleas diagnosis
Combing animal then wipe onto white tissue to see Flea dirt and maybe fleas
Fleas treatment and prevention
Correct targeted use of a species specific and approved Ectoparasiticide
Treatment of other household pets
Treat environment
Ectoparasite insects - Flies
Winged
Some fly larvae are facultative parasites (can but don’t have to infest living animals)
Obligate parasite (cannot complete lifecycle without animal host)
Fly strike (rabbits and sheep during summer)
Life cycle of flies
12 days
Adult lays eggs
Eggs turn to larvae (maggots)
Form cocoon called pupa
They hatch and become adult flies
Ectoparasite insects midges
Winged
Wings patterned with light and dark markings
Biting -mouth parts well adapted for cutting skin and sucking blood
Measure 1-3mm
Crepuscular - active at dawn and dusk
More frequently horse in uk - causes sweet itch
Vectors of disease through transmission of viruses/bacteria etc
Breed round water
Life cycle of midges
28-32 days
Adult lay eggs
Eggs hatch to Larvae
Turn to pupae
Turn to adults
Ectoparasite arachnids - mites
Single sac without definition of head or thorax
Mouthparts protrude
4 pairs of legs
Surface dwellers have long legs
Suckers or claws on end of legs
Subsurface dwellers have short legs with pegs/spines on legs
Life cycle occurs on host
Transfers from host to host close contact
Acquired from environment
Life cycle of mite
10 days to 3 weeks
Adult lives on host
Lays eggs 3-4 days eggs hatch
Larvae hatch (only 3 pairs of legs )
Larva molts to nymph and has 4 pairs of legs
Mites epidemiology
Direct skin contact bedding or brushes
Some can survive in the environment
Clinical sites of mites
Mainly lessons at ears elbows and hocks
Redness on skin
Crust formation and alopecia
Self inflicted trauma
Mites diagnosis
Skin scraping and microscopic examination
Treatment and prevention of mites
Licensed systematic treatment most effective
Isolation from other and treat all
Ectoparasite arachnids -ticks
Single sac without definition of head thorax or abdomen
Mouthparts developed for piecing skin and removing blood
Larvae 1mm
Adult 1cm
Most ticks are hard tick (scutum) shell
Life cycle of tick
3 months to 3years
Female lays eggs in environment then dies
Eggs hatch (3 pairs of legs)
Larvae feed on host
Molt into nymph in environment
Nymphs feed on host
Molt into adult in environment
Adult spends majority in environment
Mate Then feed on large mammal
Ticks epidemiology
Temporary parasite
Variable time on host
Highly seasonal
Clinical signs of ticks
Main sites will be non hairy and thin haired areas
Anaemia in heavy burdens
Infected wounds
Ticks diagnosis
Visual
Treatment and prevention of ticks
Careful removal - remove head parts so no infection (limes disease)
Disposal
Endoparasite groups in uk
Nematodes
Cestodes
Trematodes
Protozoa
(Zoonotic)
Nematode
Roundworms - cylindrical and featureless
Example - ascarids, hookworms, shipworms, strongyles, pinworm
Nematodes-ascarids
Largest round worm found in dogs cats and horses
Found in small intestine
Toxocara canis
Found in dogs
Up to 20cm long
Of white/pinkish
Stout
Toxocara cati
Cats
8-15cm long
More pronounced arrow head than canis
Toxascaris leonina
Dogs and cats
2-10cm
Parascaris equorum
Horses
40-50cm long
Life cycle of Toxocara canis
3months
Direct or indirect ingested by dog
Eggs passed in faces into soil
Eggs containing larva ingested by humans or dogs
Life cycle of canis for humans
Humans = migration to eyes, organs via circulation causing inflammation
Undercooked meat
Unwashed veg
Life cycle of canis for dog
Dogs = migrate via circulation to organs if lungs can be coughed up and swallowed then passed by feces
Pregnant dog = placenta, milk, infect puppies
Life cycle of Toxocara cati
Same as dog but no placenta passing when pregnant
3 months
Lifecycle of toxascaris leonina
Passes egg in feces
Larva develop in environment
Ingests by transport/intermediate host
Or cat/dog ingests larvae or egg
Life cycle of parascaris equorum
80days
Females lay up to 200,000 eggs per day in small intestines
Eggs passed in manure (embryo may live for 10years without hatching)
Mature egg eaten then hatch when swallowed
Go through intestine wall into liver
Blood carries larva to lungs and airways
Coughed up and swallows some become adults
Nematodes ascarids - hookworm
Large Mouthparts set at angle for hook with cutting plates and pairs of teeth
Many species
Infect small intestine
Infection from ingestion of larvae
Penetrating skin
Larval leak
Transmammary transmission in milk
Zoonotic
Life cycle of hookworms
14-30days
Lay eggs in small intestine
Passed in feces
Hatch in environment
Larvae ingested from environment or direct penetration
Larvae can remain in muscle waiting for pregnancy
Ingested via milk
Nematodes - ascarids whipworms dog
Trichuris vulpis (canine)
Found in large intestine (colon and caecum)
Anterior end is long and narrow like the lash of whip
Burrow into mucosa
Posterior end is broad like whip handle
Take Up to 12weeks to shed eggs in faeces
Nematodes - ascarids whipworms horse
Strongyloides westeri
Tiny hair like worm (intestinal head worms)
Oesophagus one third of length of worm
Develop in small intestine
1cm long
Life cycle of whipworms dog
12weeks
Eggs ingested
Hatch and begin development in intestine
Mature to adults in caecum
Eggs passsd in feces
Develop infective larvae
Lifecycle of whipworm in horses
Few weeks
Ingested or penetrates skin
Can pass to milk
develop to adults in foal in small intestine
Eggs pass in feces
Nematodes ascarids - strongyles (small red worm)
40+ different species can inhabit large intestine1cm length
Ingestion of larvae from the pasture
Burrow into wall of large intestine
Adults feed on superficial layers of intestinal mucus
Nematodes ascarids - strongyles (large red worm)
3 species that can inhabit the equine large intestine
1.5cm to 5cm
Migratory life cycle
Acquired through ingestion of larvae
Burrow into wall of large intestine
Migrate to abdomen then cranial mesentric artery then LI
cause considerable damage/ulcers/death to intestines and horse
Lifecycle of small red worm
Eggs in faeces develop
Larvae in grass ingested
Larvae Enter large intestine mucus
Develop into adults and lay eggs
Eggs pass out in faeces
Life cycle of large red worm
Same as small red worm but may migrate to abdomen and cause colic before migrating to intestine
Nematodes pinworms oxyuris equi
A gastrointestinal parasite of adult horses
Associated with perianal pruritis
Lay eggs round anus
Pale yellow eggs viewed under microscope
10cm female 1cm male
Cleanliness is essential prevention
Life cycle of oxyuris equi
Eggs pass in faces and mature in soil then ingested
Adults stay in rectum and lay egg in Anus
Clumps of 8000 to 60000
Cestodes - tapeworms
Flatworm
Head (scolex) has hooks and suckers that attach to intestine wall
Chain (strobili)
Segments (proglottids)
Each contain male and female parts which once mature drop off as bag of eggs
Passes to environment
When are you species infected by tapeworm
Horses = ingest mites carrying tapeworm
Dogs/cats = when fleas or lice carry tapeworm and bite host
Cats = when ingest rodents carrying tapeworm
Indirect life cycle of tapeworm in horses
Mites will ingest tapeworm eggs
Eggs hatch inside mite
Horse ingests mites
Mites release hatches eggs where they mature and begin to reproduce
Mature tapeworm release eggs internally
Eggs released in manure cycle begins again
Indirect life cycle tapeworms cats
Infected adult flea ingested by dog or cat
Adult worm develops in small intestine
Posterior part of adult worm passes in faeces
Segments an egg packets in faeces and on fur
Eggs ingested by flea larvae
Flea develops into adult and contains immature tapeworm
Endoparasite trematodes - flukes
Flat worm
Parasite a number of organs (intestine,bile ducts, blood, lungs)
Wet ground with standing water increases risk of
Life cycle of liver fluke
Eggs shed 8-12 weeks after infection
Host is mud snail which picks them up on grass
Cow eat the grass then ingests eggs
Endoparasite Protozoa
Small unicellular organism
Different species pararsite different tissues and organs of bod (intestine, liver, muscle, NS, RBC, brain)
Have complex series of reproductive stages and life cycles
May be zoonotic
Life cycle of toxoplasma gondii
Asexual and sexual reproduction
Raw undercooked meat
Contaminated veg/water
Cats eat prey carrying Protozoa
Contain in faeces
Contaminates pregnant humans
