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ASC 320 > final exam > Flashcards

final exam Flashcards

1
Q

short pastern bone

A

P2-middle phalanx

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2
Q

coffin bone

A

P3-distal phalanx or pedal bone

gives shape, porous, light weight

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3
Q

navicular bone

A

distal sesamoid bone, non-weight bearing, acts as a fulcrum for the deep digital flexor tendon, source of lameness

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4
Q

hoof wall

A

keritinized tubular structure that has sensitive and insensitive laminae, grows from coronary band, weight bearing structure

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5
Q

coffin bone

A

connected to hoof wall via the sensitive/insensitive laminae and the white line

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6
Q

hoof sole

A

concave in shape, expands and contracts, bears weight on solid ground, 3/8-1/4 inches thick.

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7
Q

white line

A

junction of laminae from sole and wall

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8
Q

frog

A

tubular, keritinized, higher moisture content, absorbs shock, supports structure.

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9
Q

digital cushion

A

flexible tissue, interacts with frog, shock absorber, lateral spread, expansion, contraction

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10
Q

blood flow in hoof

A

hoof pumps venous blood to the heart, venous plexus, compression (lateral cartilage, coffin bone) forces blood up, blood enters the hoof when the foot is raised

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11
Q

hoof growth

A

occurs from coronary band down, growth rate correlated with age, nutrition, season, avg. growth rate is 1/4-3/8 inches per month

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12
Q

under-run heels

A

crushed heels, poor digital cushion, greater risk of tendon injury

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13
Q

contracted heels

A

frog cannot make contact with the ground, poor shock absorption, heel cannot expand

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14
Q

cracks

A

due to unbalanced hoof , environment or hot quality, may be superficial or deep

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15
Q

bruises

A

on the sole or wall of hoof, can lead to abscessing, may result from over-trimming, may be prevented with shoes or pads

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16
Q

abscesses

A

painful infection in hoof, may lead to acute lameness, many causes, remedied by pressure relief

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17
Q

thrush

A

bacterial infection of the frog, foul odor, thick black discharge, results from poor hoof care, diseased tissue may be cut away, killed by chemical agents

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18
Q

white line disease

A

fungal and/or bacterial infection of the white line, associated in wall separation that may lead to coffin bone rotation, must expose infected area to air

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19
Q

navicular disease

A

chronic degenerative disorder of navicular bursa and navicular bone, apparent on radiographs, can be managed but not cured

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20
Q

laminitis

A

painful inflammation of the sensitive laminae, , blood clots, edema in closed space, trauma to hoof, abscesses, may lead to shock

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21
Q

founder

A

separation of laminae that leads to rotation or sinking of the coffin bone-PAINFUL

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22
Q

ectoparasites

A

outside parasites, “bugs”

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23
Q

endoparasites

A

inside parasites, “worms”

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24
Q

black flies

A

small size, gray/black/brown, breeds in running water, worst in spring, cuts skin then laps blood, bleeding/crusts in bitten areas, use repellent to protect horses

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25
Q

stable flies

A 
Medium size
•  Similar to housefly
– Grayish brown
– Feed on any warm-blooded animal
•  On horses, legs and belly
– Worst in mid-late summer – Breed in manure/decaying plant material – Prevent with sanitation, covering compost
piles (also silage bunks), insecticides
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26
Q

face fly

A

Adults: 1/4 inch long -  Dull gray color, similar to a house fly -  Feeds on mucus and the watery
secretions around the eyes, nose and mouth
-  Host for Thelazia lacrymalis (eyeworm)
-  Common in areas with cattle -  Prevent with fly mask

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27
Q

deerflies

A

Medium size
•  Slightly bigger than housefly •  Black markings on wings
– Worst during summer – Breeds near water – Feeds on mammals, reptiles and birds – Painful bite, cuts skin then laps blood – Prevent with repellent, control difficult

28
Q

horseflies

A

Large size
•  Up to hummingbird size •  Dark, color varies
– Breeds near water – Feeds on mammals, reptiles and birds – Painful bite, cuts skin then laps blood – Very disturbing to horses – Vector for equine infectious anemia (EIA) – Prevent with repellent, control difficult

29
Q

Mosquitoes

A

– Sucks blood
– Feeds on many species
•  Can cause allergic reactions in horses
– Vector for EEE, WEE, VEE, WNV – Breeds in water – Control by draining standing water, using
insecticides
– Prevent with repellent, don’t leave lights on near horses unless necessary

30
Q

horn flies

A

1/2 to 1/3 the size of a house fly – Pierce the skin and suck blood – Scabs on midline area
•  Horn fly biology
– Female lays eggs on fresh manure – Eggs hatch, pupate and emerge as flies – Adults stay close to host
•  Becoming resistant to sprays
– Manure removal helpful

31
Q

Lice

A

Small (2-3 mm long) – No wings, flat – Biting or sucking (different species)
•  Suck blood •  Chew on skin and secretions of host
– Lay eggs on hair close to skin
– Horse will look poorly groomed
•  Infestation starts around head, neck, mane and tail, will spread over entire body
•  Treat with topical insecticides
–  Ivermectin for sucking lice

32
Q

mites

A

Several species in horses – Sarcoptic, chorioptic and psoroptic – Very small – Extremely irritating
•  Cause mange
– Spread by grooming implements and tack – Leads to hair loss – Identified under microscope from skin
scrapings

33
Q

bots

A

Gastrophilus species
•  G. nasalis, G. intestinalis, G. haemorrhoidalis
– Eggs laid on hair by botfly
•  Flies do not bite
– Larvae emerge when horse’s mouth contacts the eggs
•  Warmth •  Moisture
– Larvae invade mouth tissues
•  Migrate, molt and are swallowed •  Larvae spend ~1 month in mouth Larvae attach to dorsal part of stomach
•  Above the fluid line •  Spend winter in the stomach
– Larvae release their hold and are passed in manure in late winter/early spring
– Pupate and mature to adult flies

34
Q

bots clinical signs

A

Usually none, unless heavy burden – Can cause inflammation of staomach – Can cause colic when dewormed while
heavily infested

35
Q

tapeworms

A

noplocephala species
•  A. perfoliata, A. magna
•  Small for tapeworms
– Adult worms attach near ileocecal junction – Not normally pathogenic – Heavy infestations can cause inflammation
of gut, overactive peristalsis and sometimes intussusception of ileum into cecum

36
Q

tapeworm life cycle

A

Eggs shed in feces by infected horse – Eggs taken up by mites in soil – Eggs develop to infective cysticercoid
stage inside the mite – Horses ingest infected mites while grazing – New tapeworm develops – Species specific
•  Only infects horses
– Life cycle requires mite

37
Q

Ascarids (roundworms)

A

Parascaris equorum
– Large, white worm (6-8 inches or more) – Affects young horses up to 1 ½ years old – Causes pot-belly, anorexia, coughing
•  Pneumonia
– Large masses can obstruct bile duct and
intestines

38
Q

Ascarid life cycle

A

10-12, weeks, Infective larvae ingested in egg in soil – Larvae emerge, penetrate gut wall – Larvae migrate to liver – Larvae migrate to the lungs – Larvae develop and are coughed up – Larvae are swallowed and return to
intestinal tract
– Larvae develop into adult worms and begin producing eggs
threAscarid eggs remain viable in soil for years
•  Although young horses are susceptible, immunity develops during yearling year
•  Some horses that are not exposed to ascarids when young will get infections as adults

39
Q

threadworms

A

Strongyloides westeri
– Passed from mare to foal in milk
•  After colostrum
•  Stimulated to move from mare’s tissue by parturition
– Free-living larvae can also penetrate skin
•  Migrate through lungs, get coughed up and swallowed
– Adult stages live in small intestinean cause diarrhea, poor growth
•  No longer believed to be the cause of “foal heat diarrhea
– Life cycle takes

40
Q

pinworms

A

Pinworms
– Oxyuris species
•  0.8-1.3 cm in length
– Direct life cycle
•  Fecal-oral transmission
•  Spends most of its life in large intestine and anus
•  5-month life cycle
– Female worms migrate out of the anus and lay eggs on perianal skin
•  In sticky fluid
Cause intense itching, tail-rubbing
•  Rat tailed appearance
– Not usually harmful – Worst in late summer – Spread by grooming sponges, eggs on
pasture, eggs rubbed on objects
– Species-specific
•  Children get pinworms from other children

41
Q

large strongyles (bloodworms)

A

trongylus vulgaris, S. edentatus. S.
equinus– Once the leading cause of colic – Destructive worms that migrate to various
organs and damage tissues as they go
•  Plug feeders – with teeth!
– Clinical signs
•  Diarrhea •  Depression •  Gastrointestinal disturbances
damage done
– Cutting tissue and sucking blood – Poor overall condition – nutrient losses – Liver damage – Arterioles damaged
•  Leads to reduced blood flow to the bowel •  Blood clots in bowel
– Colic due to
•  Decreased gut motility
–  (Impaction)
•  Blood clot episodes

42
Q

large strongyle lifecycle

A

Direct life cycle – only horses involved – Infective larvae ingested by horse – Larvae penetrate intestinal wall – Larvae migrate to liver, molts (9 weeks) – Larvae encyst in right flank – Larvae excyst and migrate to colon – Mature to adult stage – Begin producing eggs

43
Q

small strongyles

A

Cyathostomes – many species (> 50)
– Less harmful than large strongyles
•  Smaller, takes smaller bites •  No tissue migration beyond gut
– The focus of most adult equine parasite control programs today
– Very common in horses on pasture
– Clinical signs
•  Colic, diarrhea, emaciation •  Most horses have subclinical infections

44
Q

small strongyle life cycle

A

Direct life cycle (similar to large strongyles)
•  Without the tissue migration •  Larvae on pasture
– Horse ingests infective larvae – Larvae develop in large colon – Encyst to emerge later – Excyst to develop into adult worms – Mass excystation causes damage to gut
wall
•  Diarrhea, colic, anorexia, emaciationSmall strongyle excystation
– Survival strategy for overwintering – Triggered by
•  Favorable season •  Reduced worm burden in gut •  Deworming
– Some dewormers target the encysted stage to prevent this
•  Effectiveness of these drugs in doubt

45
Q

parasite risk factors associated with housing

A

Pastures
– Nature’s most perfect home for horses and parasites
•  Stalls
– Not a good environment for small strongyles
– Ascarid eggs can stick to floors, walls and buckets
Dirt paddocks
– Not a good environment for small strongyles
– Ascarid eggs can persist in soil for years
•  Traveling horses bring their parasites with them
– Mares with foals at side – Shared paddocks – Trail camp sites

46
Q

parasite risk by age

A

  Foals – ascarids, threadworms, small strongyles, bots
•  Yearlings to 3-year-olds - small strongyles, bots tapeworms
•  4+ years – as horses mature, they usually become more resistant to small strongyles
– A few will not – High egg shedders

47
Q

anthelmintics (dewormers)

A

Most modern dewormers are considered to be “broad spectrum”
– Control multiple species of parasites
•  One is specialized
– Praziquantel for tapeworms – Sold in combination with other drugs
•  Ivermectin moxidectin (Quest) for bots, but are also broad spectrum
Most modern dewormers have been on the market for 15-40+ years
•  Drug resistance has been reported for many species of parasite
– Small strongyles– Ascarids
•  Labels do not reflect current state of drug resistance trends

48
Q

fenbendazole (panacur, safeguard)

A

 Broad-spectrum (including ascarids)
•  Not effective against bots or tapeworms
– Active against parasites in gut (not tissues) – Wide margin of safety – Fenbendazole Powerpac (2x dose for 5
days)
•  All of the above, plus encysted small strongyles - according to label
•  Expensive

49
Q

pyrantel (strongid)

A

 Broad-spectrum (not bots)
•  Kills tapeworms at 2x dose
– Active against parasites in gut (not tissues)
– Sold in paste (P) and pelleted form (C)
•  Strongid C daily dewormer
– Wide margin of safety

50
Q

macrocyclic lactones

A

Ivermectin

•  Broad-spectrum, including bots, but not tapes •  Wide margin of safety

51
Q

Moxidectin (Quest)

A

Broad-spectrum, including bots, but not tapes •  Effective against encysted small strongyles (?) •  Narrower margin of safety •  Can cause massive die-off, colic •  Originally kept horses from shedding eggs for
up to 12 weeks – could be used less often

52
Q

praziquantel

A

Used for tapeworms
– Combined with other drugs for broad-spectrum control
•  Ivermectin (Zimectrin Gold) •  Moxidectin (Quest Plus)
– No know resistance problems

53
Q

ascarid drug resistance

A

Ivermectin/moxidectin
– No longer effective on many farms – Not recommended for this parasite
•  Fenbendazole at 2x dose
– Some resistance reported – Oxibendazole may work better
•  Pyrantel pamoate
– Some resistance reported

54
Q

drug resistance in small strongyles

A

Fenbendazole
•  Resistance reported in multiple studies conducted all over the world
•  No longer recommended for strongyles
•  Powerpac dose is no more effective than regular dose
•  Double dose for 5 days •  Cost: ~$65
Pyrantel
– Paste was ineffective on 40% of 44 farms in Southeast US in a study that included Kentucky
•  Effective on 45% of farms •  Greater efficacy in Europe and the UK
– Daily pyrantel showing resistance problems, too
•  Some blame this product for the rapid decline in this drug’s efficacy

55
Q

drugs that still work on small strongyles

A

Macrocyclic lactones
– Effective on 100% of 44 farms in Southeast US in a study that included Kentucky (ivermectin)
– Using a 2-week time period for evaluation
•  Egg reappearance times are getting shorter for ivermectin and moxidectin
– 4 weeks ivermectin, 5 weeks moxidectin – Resistance is developing

56
Q

multiple drug resistance

A

Multiple drug resistance is possible
– Parasites combine genes when they mate – Triple resistence reported in Brazil
•  No selection against drug-resistant parasites
– Resistance is forever – 40 years made no difference (Lyons, et al)
•  You are selecting for resistance every time you deworm

57
Q

fecal egg count

A

Can identify the parasites that are present
– Can identify which horses require treatment
– Only way to know which drugs work on your farm
– New deworming strategies require knowledge of fecal egg counts

58
Q

targeted treatment for small strongyles

A

 Test for eggs in manure
– Treat only horses with moderate to high egg counts and above
•  200- 500 EPG
– By targeting moderate to high shedders you can reduce total contamination of pastures by 95%

59
Q

rationale for strategic deworming

A

Rationale for this approach
– Reduces selection pressure for resistance
– Buys time as new drugs are brought to market
•  Nothing in the near future
– Resistance to the best drugs is developing in small strongyles – we must slow this progression if possible
– Untreated horses dilute the effects of the selection pressure through ‘refugia

60
Q

refugia

A

Refugia is the proportion of a population of parasites that escapes the selection by the anthelmintic
•  Encysted stages in horses not receiving a drug that kills them
•  Migrating stages in horses treated with a drug that only acts in the gut
•  Parasite larvae on pasture •  Parasites in untreated horses

61
Q

strategic deworming pros and cons

A

Pros:
– Horses aren’t being treated unnecessarily – Problem horses are being identified – Reduced larval load on pasture – Cost savings over time
•  Cons:
– Fecal egg counts may cost more than dewormer
– Testing lab or equipment required – Sample handling is critical

62
Q

adult horse parasite treatment

A

Start with fecal egg counts (FECs) on all adults to identify high strongyle egg shedders
•  Only deworm horses with FECs above approximately 500 eggs per gram (EPG)
–  Your vet may use a different cutoff
–  Recheck after 4-6 weeks to see if high FEC has returned
Deworm all adult horses twice per year with ivermectin or moxidectin with praziquantel
–  Fall, early spring (Zimectrin Gold, Quest Plus, etc.)
•  Occasionally check a portion of your low egg shedders for changes in status
–  Late spring, early fall, winter
–  After the effects of previous dewormer have passed

63
Q

foal and weanling parasite control

A

Ascarid control
–  Start deworming at 60 days, then every 60 days thereafter
–  Fenbendazole (Panacur, SafeGuard) –  Pyrantel (Strongid paste or Rotectin) –  Oxibendazole (Anthelcide EQ).
•  These drugs should be given at double the dose
•  Use fecal testing to check drug efficacy
Small strongyle control
–  Start deworming at 90 days, then every 45-60 days thereafter, depending on egg reappearance time
–  Ivermectin (Eqvalan, Zimectrin) –  Moxidectin (Quest)
•  If foal is at least 6 months of age

64
Q

yearling to 3 yr old parasite control

A

Expect this group to have more high strongyle egg shedders
–  Ascarid egg shedding should end
•  Will require more frequent treatment than older horses
•  Follow suggestions for adult horses

65
Q

parasite management in pastures

A

Rotate with
non-equids
– Parasites are species-specific
•  Put your youngest horses on your cleanest pasture Remove manure from pasture
– Labor intensive! – Effective!
•  Dragging and mowing
– Timing critical - summer – Roughs have higher larvae counts
Rest pastures or use for hay one year
•  Avoid putting foals in the same pastures year after year

ASC 320 (4 decks)

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