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PARASITOLOGY - 2 > 11 – Horses Helminths II > Flashcards

11 – Horses Helminths II Flashcards

1
Q

Large strongyles resistance

A

NOT resistance:
- Benzimidazoles
- Pyrantel
- ML

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2
Q

Small stronglyes resistance

A

Resistant to:
- Benzimidazoles
- Pyrantel
- ML (early): shortened egg reappearance period

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3
Q

Parascaris resistance

A
  • NOT resistant to benzimidazoles
  • Resistant to: pyrantel and ML
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4
Q

How do we prevent resistance?

A
  • Maintain and monitor drug efficacy
  • Use strategic treatments to maximize effect and minimize shedding
  • Use non-drug methods of control (pasture and manure management)
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5
Q

Maintain and monitor drug efficacy

A
  • Determine which horses contribute to most eggs (typically old and young have the most)
  • Leave parasite refugia by using targeted selective treatment
  • Monitor drug efficacy (by FEC reduction test)
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6
Q

Which horses produce the most eggs? (distribution)

A
  • Clumped distribution
    o 22% (medium to) high shedders: minority of animals but contribute a lot of eggs!
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7
Q

Individual fecal egg counts (FEC)

A
  • Test adult horses at least TWICE a year (spring and fall)
  • Test at least 9 weeks post treatment (BZ, PR), 12-16 weeks (ML)
    o Egg reduction period: did it work?
  • Use McMaster or other quantitative methods
  • Categorize into low, medium and high shedders OR create herd specific frequency profile
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8
Q

FEC low, medium and high shedders: values

A
  • Low: <200
  • Medium: 200-500
  • High: >500
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9
Q

Targeted Selective Treatment (TST)

A
  • Don’t treat those with low FEC
  • Treat those with moderate to high FEC
  • *refugia from those NOT treated
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10
Q

What can your option for targeted selective treatment be based on (2)

A
  • FEC
  • % herd
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11
Q

Targeted selective treatment: based on FEC

A
  • Treat all above threshold
  • Treat all above a higher threshold
  • Treat all animals above a herd-specific FEC threshold
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12
Q

Targeted selective treatment: based on % herd

A
  • Treat all but bottom 20% of shedders
  • Treat top 50% of shedders
  • Treat top 20% of shedders
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13
Q

Fecal egg count reduction test (FECRT)

A
  • Test at least 6 horses per farm
  • Use horses with highest FEC
  • Use quantitative technique
  • Test, treat, re-test in 14 days
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14
Q

What is the equation of % FECRT?

A
  • % FECRT= ((pretreatment-post treatment eggs per gram (EPG))divided by pretreatment EPG MULTIPLE BY 100
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15
Q

What is anthelmintic resistance for a FECRT?

A
  • Less than 95%
  • *herd level diagnosis
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16
Q

When do you test and treat adult horses in western Canada?

A
  • Test and treat all horse in fall (with Moxidectin to get encysted larval stages of small strongyles and bots)
  • Test and treat moderate/high shedders in spring (and maybe 2-3 months later)
  • Do FECRT at least every 3 years to ensure efficacy
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17
Q

When do you test and treat horses <3 years of age in western Canada?

A
  • Treat up to 4 times a per
  • Treat at:
    o 1-2 weeks if Strongyloides
    o 2-3 months and 6 months for Parascaris
  • Subsequently treat with drug effective against small strongyles (ivermectin still OK in SK, but still check if it is working)
  • Do FECRT yearly to ensure efficacy
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18
Q

Shedding of GI nematodes in 1st year of life for foals: ‘order’

A
  • Strongyloides
  • Parascaris
  • Strongyles
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19
Q

Deworming program

A
  • No one true way
  • Geography
  • Pasture vs. stable
  • Number of horses per acre
  • Pasture management
  • Any known resistance
  • *owner risk tolerance
  • Weighing horses accurately to avoid underdosing
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20
Q

Pasture and manure management

A
  • don’t relocate recently dewormed horses to ‘clean’ pasture
  • reduce stocking density
  • dispose of manure regularly (twice a week)
  • don’t feed off the ground
  • do NOT spread fresh manure on fields that horses are grazing
  • mow and harrow pastures periodically
  • separate weanlings from yearlings, adults
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21
Q

When do you always treat for parasites?

A
  • Coughing foal with no bacterial or viral cause
  • Diarrhea in 2-3 week old foal
  • Diarrhea, weight loss, low protein/albumin, edema
  • Spasmodic colic of unknow origin
  • Pruritus ani (explore non parasitic causes!)
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22
Q

What are the large intestinal nematodes?

A
  • Oxyuris equi
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23
Q

Oxyuris equi

A
  • Pinworm of horses
  • Caecum, colon, rectum, perianal region
  • Worldwide distribution, including western Canada
  • Eggs environmentally RESISTANT
  • NOT zoonotic
24
Q

What is the life cycle of Oxyuris equi?

A
  • Eggs in feces
  • L1-L3 in environment over a few days
  • Infective=L3 in egg
  • Mucosal migration
  • Adults in large intestine
    o Females: go out of anus and lay eggs before they die: ITCHY BUM
  • *PPP: 5 months
25
Q

What are the clinical signs with Oxyuris equi?

A
  • Many show NO adverse effects
  • Usually associated with stabled horses with poor hygiene
  • Some: itchy bum
26
Q

‘itchy bum’ in horses due to Oxyuris equi

A
  • Egg-laying by females
  • *pruritius ani
    o Leads to attempts by affected horses to relive itching (back into something or someone)
    o Hair loss due to rubbing
27
Q

How do you diagnose Oxyuris equi?

A
  • Rarely floatation
  • **Usually swab or tape mount from perianal region
28
Q

How do you treat Oxyuris equi?

A
  • HYGIENE (environment and perineal washing)
  • Many labeled products
29
Q

What is the connective tissue nematode of horses?

A
  • Onchocerca cervicalis
30
Q

Onchocerca cervicalis

A
  • ARTHROPOD TRANSMITTED
  • Present in W. Canada where suitable climate and vectors exist (ex. BC)
  • Many wont show signs
31
Q

Onchocerca cervicalis lifecycle

A
  • L3 from midge IH
  • Adults live in nuchal ligament
  • **Microfilaria (L1) make way to dermis in areas favored by local midge species
    o L1 to L2 to L3)
32
Q

How do you diagnose Onchocerca cervicalis?

A
  • Microfilariae in skin histological section
  • OR culture from biopsy
33
Q

Cutaneous onchocerciasis location and signs

A
  • Face, neck and ventral midline
    o BC: face and neck
    o Other areas of world: ventral midline
  • Alopecia
  • Crusting
  • Pruritus
  • *most obvious in SUMMER
  • *due to microfilaria
34
Q

What signs can Culicoides be associated with as well?

A
  • Specific disease affect the skin (Queensland itch or sweet itch) that is caused by HYPERSENSITIVITY to antigens in midge saliva
35
Q

How do you treat Onchocerca cervicalis?

A
  • ML will kill larvae but NOT ADULTS
36
Q

What is the lung nematode of horses?

A
  • Dictyocaulus arnfieldi
37
Q

Dictyocaulus arnfieldi

A
  • Rare in Canada (if are seen=in BC)
  • **Dyspnea and cough (respiratory signs)
  • Not usually patent in adult horses
  • *reservoir is DONKEYS and HORSES <3 years old
  • *pasture transmitted
38
Q

Dictyocaulus arnfieldi lifecycle

A
  • L1 pooped out
  • L1 to L2 to L3 in environment
  • Infective stage: L3 ingested
  • *tracheal migration to lungs
39
Q

Dictyocaulus arnfieldi diagnosis

A
  • Test: baermann on fresh feces from foal or yearly
    o Usually NOT patent in adult horses
40
Q

How do you treat Dictyocaulus arnfieldi?

A
  • Who: foals with a cough
  • What: extra label ivermectin (fenbendazole?)
41
Q

What are the cestodes (cyclophyllids) of horses?

A
  • Anoplocephala perfoliate
  • Anoplocephala magna
  • Paranoplocephala mammillana
42
Q

Anoplocephala perfoliate

A
  • Ileum and caecum
  • MOST common species
  • *has lappets
  • *linked to ileal impaction and spasmodic colic
43
Q

Anoplocephala magna location

A
  • Proximal SI
44
Q

Paranoplocephala mammillana location

A
  • Proximal SI
45
Q

Anoplocephala and paranoplocephala lifecycle

A
  • Eggs with hexacanth larva
  • Free-living mite with cysticercoid (INFECTIVE): 2-4 months
  • **acquire=Ingest mite and get adults
46
Q

Anoplocephala and paranoplocephala eggs

A
  • RARELY seen on fecal floatation
  • Hexacanth larvae
47
Q

What are the clinical signs of equine tapeworms? (Anoplocephala and paranoplocephala)

A
  • Often none in the DH (horses)
  • Will see in foals with other health issues
48
Q

What is a risk factor with Anoplocephala perfoliate?

A
  • Ileal impaction and spasmodic colic
49
Q

Diagnosis of Anoplocephala and paranoplocephala

A
  • *eggs not reliably shed
  • **Do fecal float following treatment with cestocide (praziquantel) and test feces about 24hrs later
  • Coproantigen and serology (n/a in Canada)
50
Q

Treatment of Anoplocephala and paranoplocephala

A
  • Single ANNUAL treatment with praziquantel in LATE FALL
51
Q

What is Potomac horse fever caused by?

A
  • Neorickettsia risticii (gram-negative bacterial endosymbionts of flukes of bats)
52
Q

Potomac horse fever

A
  • Freshwater snail first IH
  • flying aquatic insects as second IH
  • *horses accidently ingest N. risticii inside cercaria in water or metacercaria in aquatic/adult insect
  • **severe acute diarrhea, laminitis, abortion
53
Q

How do you diagnose Potomac horse fever?

A
  • PCR blood/feces
54
Q

How do you treat Potomac horse fever?

A
  • Oxytetracycline
  • Vaccines?
55
Q

What is the most common strongyle seen that stays ‘strong’ across age groups?

A
  • Cylicostephanus longibursatus
56
Q

Male bias for parasites? Treatment considerations

A
  • Attributed to immunosuppression by androgens
    o But most are geldings
  • *but mares were more likely to be infected
57
Q

Seasonal variations and treatment

A
  • Higher prevalence and intensity in fall vs. spring
  • *could indicate species specific epidemiology differences with pathological consequences
    o Spring: Due to emergence after wintering as hypobiotic larvae (DEADLY)
  • Those with increased prevalence in fall: may be more resistant to heat and drought in the summer?

PARASITOLOGY - 2 (13 decks)

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