Introduction to Parasitic Diseases of Food Animals Flashcards
disease sign
symptoms that can have different underlying causes
disease
manifestation of an infection
parasite phyla diversity
nematodes, tapeworms, flatworms, and protozoa
metazoa
multicellular, nematodes, tapeworms, and flatworms
protozoa
single celled
nematodes
or roundworms, economically important if food animals
nematode disease presentation
parasitic gastroenteritis and hemonchosis, problem in younger animals
nematode characterisitics
numerous species, direct life cycle, some are more pathogenic than others
nematode host species
some species affect sheep and cattle, wildlife species may carry domestic animal nematode parasites
direct life cycle
one host involved in the parasitic life cycle
adult tapeworms
cause mild intestinal disease with not much economical significance
tapeworm larval stages
cause non-intestinal disease
tapeworm characteristics
mainly direct lifecycle, tapeworms easily identified in feces, segmented parasites
flat worms
liver flues in ruminants are important in wet and temperate areas of the USA
liver fluke lifecycle
indirect, two hosts involved in lifecycle, snails ingest liver fluke, offspring in pasture, cow ingest offspring
why is understanding lifecycle important?
for prevention and control of parasites
liver flukes: sheep
cause acute to chronic liver disease, can cause significant morbidity and mortality in a flock
liver flukes: cattle
more resistant than sheep, disease is uncommon, livers are often condemned at processing plants
protozoa
unicellular eukaryotic organisms that need host cells to replicate
protozoa: coccidia
cause scours and enteritis in young sheep, goats, cattle, pigs, and poultry
coccidia importance
commercially important disease, worldwide distribution including Wyoming, preventative treatment is often used with intensive farming systems
protozoa: cryptosporidia
causes scours and enteritis in neonates
cryptosporidia importance
common cause of neonatal diarrhea in ruminants and pigs, zoonotic mainly in the young and immune suppressed
protozoa: toxoplasma gondii
important cause of abortion in sheep and goats
toxoplasma gondii importance
zoonotic, important risk for pregnant women
protozoa: neospora caninum
causes abortion in cattle
neospora caninum importance
problematic in dairy farms, prevalent in california
questions to ask about parasitic disease cases
grazing history
lambing and breeding season
symptoms
what they treated with
environment/location
new animals
pre-risk disease history
why is weakness and pale skin a disease sign of parasitism?
blood suckers can cause anemia
hemonchus contortus
or barber’s pole worm, are blood consuming leading to severe anemia in the host, settle in the abomasum
hemonchus contortus environment
prevalent in warm, moist, subtropical, and tropical areas
hemochus contortus importance
most important disease affecting some sectors of goat and sheep farming industry, can be a problem in cattle, not the only parasite of the abomasum
hemonchus contortus lifecycle
direct lifecycle, eggs pass through feces and ruminant consumes larval phase while adults develop in the abomasum
hemonchus contortus control
good treatment and pasture management, treat during adult stages and then move pastures
monitoring for hemonchus contortus
fecal parasite counts and evaluating eyes for anemia
control of hemonchus contortus disease
anthelminthic program, pasture management
what does pasture management look like to control disease?
rotational grazing, strip grazing, crop rotations, avoid overgrazing, and avoid grazing young or susceptible animals on contaminated pastures
why may a response to anthelmintics be poor?
reinfection from larvae on pasture, parasite resistance, wrong dosage, improper administration, degraded drugs
hemonchus key points
cause of serious disease and economical loss in small ruminants, worldwide, uncommon in WY, control includes deworming, breed resistance, and pasture management
why are fungi important?
directly invade animal tissues, direct ingestion of mycotoxins on food material causes disease in animals, mycotoxins ingested by animals may pass into human food chain
fungi directly invade animal tissues
ringworm in cattle, aspergillosis in poultry
direct ingestion of mycotoxins on food material causes disease in animals
fescue foot in cattle where fungus grows on tall fescue (ergovaline), ergotism in cattle where fungus grows on wheat and rye grass (ergotamine)
mycotoxins ingested by animal may pass into human food chain
mycotoxins secreted into milk, some mycotoxins are carcinogenic leading to liver cancer, liver cancer rates are high in humans in countries with less regulation, mycotoxins in animal and human feeds are regulated by the FDA
the most common way that humans ingest mycotoxins
grain
ringworm in cattle
can affect many other species, form spores that survive for prolonged periods in porous surfaces, highly infectious with housed cattle but has self limiting infection
ringworm in cattle susceptibility
common in young animals, zoonotic causing mild skin disease
ringworm in cattle treatment and control
antifungal drugs in feed, will resolve on its own, keep buildings clean to prevent build up of spores and have proper ventilation
Aspergillosis in poultry linked with
contaminated buildings, spores of Aspergillus fumigatus contaminate buildings
aspergillosis disease signs
trouble breathing, inflammation and invasion of fungi in air sacs
aspergillosis in poultry
often causes loss with high stocking density, cause sever outbreaks in young birds under six weeks
aspergillosis remedy
difficult to treat so tolerate low level losses or try to eradicate or suppress by building disinfection, fumigation, good sanitation and good ventilation
aspergillosis dangers
can cause outbreaks that spread quickly with high mortality rate, really hard to get rid of it through disinfection
ergotism/fescue foot
mycotoxins survive in hay, cases can occur during winter feeding, most important impact is on production at lower doses, summer slump
ergotism/fescue foot disease sign
mycotoxins cause vasoconstriction and loss of blood supply (ischemia), swollen feet and non-weight bearing lameness
prions
infectious misfolded prion proteins that due not have nucleic acid
what disease do prions cause?
transmissible spongiform encephalopathies
Human prion disease
kuru, mid 50’s in New Guinea, infectious through cannibalism
Sheep prion disease
scrapie, 1930s, not zoonotic
Deer and elk prion disease
chronic wasting disease, not thought to be zoonotic, reported in farmed deer
Cattle prion disease
bovine spongiform encephalopathy, zoonotic and derivatives, 180,000 cattle cases, 1987-2015, peak in 1992
BSE transmitted to humans
vCJD, 180 cases, outbreak peaked in 2000
misfolded prion protein
insoluble, aggregates, difficult for cells to degrade and remove
the prion replication cycle
spontaneous misfolding to form PrPsc (sporadic disease) is extremely rare, infectious PrPsc converts normal prion proteins
prion disease presentation
misfolded prions accumulate in the brain and cause degeneration, prions accululate in lymphoid tissues
prion diagnosis
dead: microscopy of brain tissue
live: biopsy of third eyelid in sheep or rectal tissue in deer, antibody staining
would PCR work for prion diagnosis?
No, prions do not contain nucleic acid to sequence
scrapie
cause wasting and itchiness in sheep and goats, vertical transmission from placental ingestion or directly to fetus, close to eradicated in the US
CWD
mainly wasting in deer, elk, and moose, horizontal transmission through ingestion of prions in contaminated environment, expanding in distribution in WY, CO, NE, overseas, farmed deer
how are prions inactivated?
autoclaving, heating, soaking in bleach
is it possible to eradicate prions from the environment?
it is not currently possible to inactivate prions when there is large scale environmental contamination
