Parasites Flashcards
Larval stage of Tania saginata
Cysticercus bovis
Name the definitive host and intermediate host of Tania saginata
DH = human
IH = cows
Lifecycle of taenia saginata
Human eats Cysticerci in undercooked, infected muscle
Scolex attaches to the intestinal wall
Adult worms develop in the intestines and produce eggs
Eggs in faeces are passed into the environment
Cattle become infected by ingesting contaminated vegetation
Eggs hatch in the cattle intestines releasing oncospheres
Oncospheres penetrate the intestinal wall and migrate into striated muscle via blood
In the muscle, oncospheres => Cysticerci
Name commonly affected tissues of taenia saginata
Muscles: heart, tongue, masseter, diaphragm
Give PM results of taenia saginata
Localised infection - partial rejection
Rest of carcass has to undergo freezing treatment
Generalised infection - total rejection
ABP category 2
Is there a zoonotic risk of taenia saginata
Yes
Humans only become infected by eating raw/undercooked beef containing the cysticerci
Give costs to the farmer of taenia saginata
Partial rejection
Total rejection if generalised
Advice to farmer - taenia saginata
Zoonoses
- Cook beef well before consumption
- Don’t eat meat which could potentially be contaminated
Reducing cases
- Treat cows with praziquantel monthly
- Make sure all human sewage is disposed of properly
larval stage of taenia ovis
cysticercus ovis
Name the definitive host and intermediate host of taenia ovis
DH= dogs
IH = sheep
lifecycle of taenia ovis
Eggs in dog faeces are passed into the environment
Sheep ingest the eggs from pasture and become infected
Eggs hatch within the sheep intestines => oncospheres
Oncospheres travel in the bloodstream to muscles where they develop => cysticerci
Dogs become infected by eating raw meat/offal which contain the cysts
Commonly affected tissues taenia ovis
Muscles: heart (mostly), masseter, diaphragm
PM results taenia ovis
Partial rejection of affected area
Total rejection if found in 3 or more locations
ABP category 2
is taenia ovis zoonotic
NO
Cost to farmer of taenia ovis
Tends to be total rejection so large cost
Advise to farmer taenia ovis
No risk of zoonoses
Reduce cases
- Worming all dogs with praziquantel monthly
- Don’t feed dogs raw offal
- Dispose of all carcasses rapidly to stop dogs scavenging
- Fence off footpaths to reduce risk of other dogs defecating in fields
larval stage of taenia hydatigena
cysticercus tenuicollis
Name the definitive host and intermediate host of taenia hydatigena
DH = dogs
IH = sheep, other livestock
lifecycle of taenia hydatigena
Eggs In dog faeces pass into the environment and contaminate the pasture
IH ingest the eggs, which hatch in the intestines => oncospheres
Oncospheres penetrate intestine wall and travel to the hepatic portal system
Develop into cysticerci and migrate to the liver parenchyma
Migrate until they reach the surface of the liver or the diaphragm
Dogs become infected by ingesting raw, infected meat
Cysticercus => adult in dogs intestine and produce eggs which are shed in faeces
Commonly affected tissues taenia hydatigena
Liver - will see migration tracts
Surface of other abdominal organs
PM results of taenia hydatigena
partial rejection of organ
ABP cat 2
Is taenia hydatigena zoonotic
NO
taenia hydatigena costs to farmer
Infection leads to major economic looses => poor livestock performance
- Loss of appetite
- Increased feed costs
- Poor carcase weight/daily weight gain
Partial rejection at PM
Advice to farmer taenia hydatigena
No risk of zoonoses
Reduce cases
- Worming all dogs with praziquantel monthly
- Don’t feed dogs raw offal
- Dispose of all carcasses rapidly to stop dogs scavenging
- Fence off footpaths to reduce risk of other dogs defecating in fields
larval stage of taenia solium
Cysticercus cellulosae
Name the definitive host and intermediate host of taenia solium
DH = humans
IH = pigs and humans
lifecycle of taenia solium
Eggs in infected human faeces are shed into the environment
IH becomes infected by eating eggs
Eggs hatch => oncospheres in the intestine
Oncospheres penetrate the intestinal wall and migrate to striated muscle, brain or liver
In these target tissues => cysticerci
DH becomes infected by eating raw, infected muscle where cysticerci => adults which produce eggs, which are passed in faeces
commonly affected tissue taenia solium
Muscle: Heart, brain, liver
PM results taenia solium
TOTAL rejection
Even if just in one location as humans are an intermediate host, we can spread it to other humans and reinfect ourselves
ABP cat 2
is taenia solium zoonotic
yes
advice to farmer taenia solium
Prevention in pigs
- Make sure all human sewage is disposed of correctly
- Vaccinate pigs
- Worm pigs with praziquantel/ oxfendazole
- Ensure good sanitation and husbandry
Human treatment
- Praziquantel
- Don’t eat undercooked meat
taenia multiceps larval stage
Coenurus cerebralis
Name the definitive host and intermediate host of taenia multiceps
DH = dog
IH = sheep and other livestock
lifecycles of taenia multiceps
Eggs in infected dog faeces are passed into the environment
Sheep ingest the eggs which hatch in the small intestine into oncospheres
Oncospheres penetrate intestinal wall and circulate to brain and spinal cord via blood stream
Oncospheres => coenuri in the intermediate host tissue
Dogs become infected by ingesting infected brain or spinal cord
Coenuri => adults in the intestine of dogs which produce eggs which are shed in faeces
commonly affected tissues taenia multiceps
brain
spinal cord
PM results taenia multiceps
Partial rejection of the affected tissue
ABP cat 2
If sheep >12 months, brain and spinal cord = SRM => ABP cat 1
is taenia multiceps zoonotic
Yes
Human infection via eating infected faeces of dogs
Advice to farmer taenia multiceps
Zoonotic via dog faeces, not sheep
Reducing cases
- Treat dogs with fenbendazole or praziquantel monthly
- Do not allow dog access to sheep carcasses
- Fence off footpaths
- Do not allow dogs to defecate in sheep fields
larval stage of echinococcus granulosus
hydatid cyst
Name the definitive host and intermediate host of echinococcus granulosus
DH = dogs
IH = sheep
lifecycle of echinococcus granulosus
Eggs in infected dogs faeces are shed into the environment
Sheep ingest eggs from pasture
Egg hatches => oncosphere in the intestine of sheep
Oncosphere penetrates intestinal wall and migrates to target tissues where they develop into cysticerci
Dogs become infected by eating raw, infected meat containing the cysts
Cysticerci => adult in dog intestine which produces eggs which are shed in faeces
commonly affected tissues echinococcus granulosus
Liver, lungs, other organs
PM results echinococcus granulosus
Partial rejection of affected organ
Total rejection if multiple organs
ABP cat 2
is echinococcus granulosus zoonotic
yes
Humans become infected by contact with infected dog faeces
No risk from being in contact with sheep
cost to farmer of echinococcus granulosus
Condemnation of affected organs
Total rejection as can be found with emaciation
Poor carcase weight
Poor meat yield
Advice to farmer echinococcus granulosus
Zoonotic risk
- Not via contact with sheep, human risk from infected dog faeces
- Wash hands well, don’t allow dogs to defecate where children play
- Don’t consume potentially contaminated food/water
Reduce cases
- Worm all dogs with praziquantel monthly
- Don’t feed dogs raw offal
- Dispose of all carcasses rapidly to stop dogs scavenging
- Fence off footpaths to reduce risk of other dogs defecating in fields
which parasite is notifiable
echinococcus multicocularis
name the larval stage of echinococcus multicocularis
Cystic echinococcosis
Name the definitive host and intermediate host of echinococcus multicocularis, and describe the lifecycle
DH = fox
IH = rodents
Eggs are shed into the environment in infected fox faeces
Rodents ingest the eggs which hatch into oncospheres in the intestine
Oncospheres penetrate the intestinal wall and migrate to target tissues
Form alveolar hydatid cysts
Foxes become infected by ingesting infected tissues, and the adult develops in the small intestine and produces eggs
commonly affected tissues echinococcus multicocularis
liver
PM results echinococcus multicocularis
Partial rejection of affected tissue
ABP cat 2
Notifiable
is echinococcus multicocularis zoonotic
yes
how to prevent spread of echinococcus multicocularis
Prevent dogs feeding on rodents
Avoid contact with wild animals
what is the common name for ascaris suum
milk spot
name the larval stage of ascaris suum
ascarids eggs
Name the definitive host and intermediate host of ascaris suum
DH = pigs
IH = none
lifecycle ascaris suum
Ascarids eggs in soil mature and are ingested by the pig
Eggs with L3 ingested by a pig
L3 hatches and penetrates in the intestinal mucosa and travels to the liver and hepatic portal vein
Migrating L3 causes pathology
Migration to the lungs to the bronchial tree –> coughed, swallowed and back into the intestine
Adults in the intestine mate and produce highly resistant eggs
commonly affected organs ascaris suum
liver
lungs
PM results ascaris suum
Partially reject the affected liver/lungs as ABP cat 3
No risk to animal health
is ascaris suum zoonotic
Yes - but very low risk to farmer/family
which pigs are most at risk for ascaris suum
Free range pigs
Because the eggs are highly resistant and paratenic hosts makes it much more difficult to clean effectively to reduce the risk
advice to farmer ascaris suum
Benzimidazoles to kill intestinal adults
Full cleaning and destruction of faeces 3-4 days after treatment
Request abattoir to give report on efficacy of treatment
Use faecal counts to assess problem in vivo
name the larval stage of trichinella spiralis
doesn’t have one
Name the definitive host and intermediate host of trichinella spiralis
DH = pigs
IH - not one as direct lifecycle
lifecycle of trichinella spiralis
Pigs ingest meat containing cysts with larvae inside
Cyst walls are broken by the stomach and free larvae penetrate the SI
Larvae sexually mature
Females penetrate deeper into the intestinal mucosa and release larvae after mating
Young larvae migrate into lymphatic system and penetrate muscle cells
Encyst in striated muscle
Ingested larvae infiltrate striated muscle cells and become cyst
commonly affected tissue trichinella spiralis
Striated muscle
PM results trichinella spiralis
Cysts are only seen microscopically
Requires testing before going into the food chain
- Samples taken from diaphragm, tongue, masseter, foreleg
Carcasses must be held in chiller until a negative test result is received
Partial rejection of affected tissue
- Rest of carcass must be frozen
ABP cat 2
is trichinella spiralis zoonotic
yes
advice to farmer trichinella spiralis
Don’t feed pigs raw meat scraps
Cook meat thoroughly before human consumption
Rat control important as they can spread it
name the larval stage of fasciola hepatica
Encysted metacercaria
Name the definitive host and intermediate host of fasciola hepatica
DH = livestock
IH = Lymnea snail
lifecycle of fasciola hepatica
Eggs shed in livestock faeces
After 2 weeks, eggs hatch => miracidium which migrate in the environment to find the Lymnea snail
In the snail they develop and multiply, and then are shed from the snail as Cercaria after 6 weeks
They then live in the vegetation where they are ingested by livestock grazing
Immature fluke travel to the liver and migrate to the bile ducts => adult fluke
Adult fluke produce eggs which are shed in faeces
commonly affected tissues fasciola hepatica
liver
PM results fasciola hepatica
Partial rejection of the liver
ABP cat 3 - as doesn’t pose a risk to animal health
is fasciola hepatica zoonotic
Not really - only by ingesting plants contaminated with the immature larvae
fasciola hepatic cost to farmer
PM rejections
Poor performance
Animals can become anaemic
Reduced milk yield
advice to farmer fasciola hepatica
Pasture management/rotation
Avoid grazing in wet seasons - more likely to be snails
Fence off wet areas
Increase soil drainage
Treat sheep using Triclabendazole
