Important parasitic diseases of small ruminants

Question 1

Drugs approved for internal parasites of sheep in Canada
- admin route?

Answer 1

ALL ORAL!
Ivermectin (+injectable)
Closantel
Lasalocid
Monensin
Decoquinate
Toltrazuril
Sulfamethazine

Question 2

Diarrhea differentials

Answer 2

A. Coccidiosis
B. Parasitic gastroenteritis

Question 3

Coccidiosis
- pathogens for sheep and goats?
- PPP
- severity of disease depends on…

Answer 3

Eimeria spp.
- sheep/goat specific + multiple species
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Sheep:
* 11 species
* 2 pathogenic – E. crandallis, E. ovinoidalis
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Goats:
* 9 species
* many pathogenic – E. ninakohlyakimovae, E. caprina, E. arloingi, etc
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- Severity of disease proportional to level of environmental contamination
- Pre-patent periods = 2-3 weeks

Question 4

Coccidiosis
- prevalence
- who is affected
- clinical signs
- types of infections?
- Dx

Answer 4

• very common
• typically lambs/kids @ 1-4 months of age
• usually poor growth, often pasty/diarrheic feces, dullness, abdominal pain, occasionally bloody diarrhea
• pot bellied, open fleeced
• subclinical infections > production impact
• often other diseases (e.g. pneumonia, urolithiasis)
• Diagnosis – clinical signs + fecal flotation (oocysts – yes/no)

Question 5

Coccidia infection of lambs
- oocyst survival
- shedding, how lambs get infected
- risk factors for disease
- Tx

Answer 5

(a) oocysts may overwinter in environment
(b) ewes shed small #s oocysts in periparturient period > subclinical infections in lambs born early > disease in lambs born late
* intensification increases likelihood of clinical coccidiosis outdoors + indoors
* stress > disease (e.g. dietary change, weaning, shipping)
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Treatment – isolate clinically affected – fluid therapy? - treat entire group with coccidiocide (sulfa (approved), amprolium) - move to clean bedding/grazing

Question 6

Coccidiosis - prevention

Answer 6

• good hygiene in barns – clean dry bedding, feed off ground
• house/graze late lambs in different areas from early lambs
• coccidiostat in lamb creep feed until 90 days old or until market - lasalocid, decoquinate, monensin (!) - correct dosage > monensin is cheap, but can kill sheep if given the wrong dose!
• if no creep feed or intake problems – toltrazuril one week before expected disease

Question 7

Parasitic gastroenteritis
(gastro-intestinal nematodes)
Most important?

Answer 7

– Teladorsagia (diarrhea)
– Trichostrongylus (diarrhea)
– Haemonchus (NO diarrhea)

Question 8

gastro-intestinal nematodes life cycle

Answer 8

• Adult nematodes in the digestive tract of sheep lay eggs
• Eggs passed onto pasture in manure
• Eggs hatch, and larvae develop to infective 3rd stage (L3)
• Infective larvae are ingested by grazing sheep

Question 9

Sudden death/Severe anemia - caused by what GI nematodes?

Answer 9

A. Haemonchosis
(B. Fasciolosis)

Question 10

Haemonchosis
- pathogen
- disease presentations?
- seasonality?
- who dies?

Answer 10

• Sheep + goats – Haemonchus contortus (barber’s pole worm)
• Acute disease – sudden death, severe anemia - lethargy, no diarrhea
• Chronic disease – edema, weight loss, poor growth, anemia
• Highest pasture L3 levels - late summer (July/August)
• Losses - lambs, yearlings (+/- adult sheep)

Question 11

Haemonchosis
- diagnosis
- PM
- control

Answer 11

Diagnosis
– anemia, hypoproteinemia,
- usually high gastro-intestinal nematode (GIN) egg counts
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PM – hyperemic abomasal mucosa + parasite #s > 1 parasite = 50μl blood loss/day
> 1000+ parasites = significant burden
> any animal on pasture will have hemonchus - must be a significant number
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Control – FAMACHA system used to identify animals that require treatment.
> anemia = significant burden

Question 12

Parasitic gastroenteritis
- how does pasture get contaminated?
- when do we see disease?
- drug resistance?

Answer 12

• ewes = significant source of pasture contamination in spring (“peri-parturient relaxation of immunity”: 2-4 weeks before lambing to 4-8 weeks after lambing)
• disease seen primarily lambs mid summer onwards (+/- older animals)
  > ewes usually have disease around lambing
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• globally – drug resistance in Teladorsagia and Haemonchus = major concern:
  > Ontario (2011)
  – resistance to fenbendazole on 100% (20/20) farms
• resistance to ivermectin on 93% (27/29) farms - all resistance in Haemonchus

Question 13

GIN egg shedding of Canadian sheep over year if no deworming

Answer 13

ewes - shed Feb, March, peak in April…
lambs - shed June, July, August…> this is where we see peak disease for them
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pasture infectivity big peak in June-July, then smaller peak in spetember

Question 14

Control of parasitic gastroenteritis
- most important considerations
- objectives

Answer 14

Recognize that:
* ewes = primary source of pasture contamination in spring
Objectives of control program:
* minimize drug use
* ideally, only treat animals that require treatment - reduces risk of selection for drug resistance (“Selective deworming”)

Question 15

Anthelmintic use in Canada
Targeted Selective Treatment:

Answer 15

• Ideally, treat ewes at lambing: - if possible, only treat ewes that require treatment (e.g. FAMACHA score)
• Monitor 4+ weeks after turnout
• Monitor lambs in early July and treat accordingly
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  If control periparturient rise in ewe egg output – not usually necessary to treat lambs until weaning

Question 16

when to deworm ewes and lambs for hemonchus

Answer 16

ewes - May-June
lambs - June-July

Question 17

rubbing wooled areas / wool loss?

Answer 17

> lice or sheep keds, NOT mange

Question 18

lice in sheep and goats
- what are they?

Answer 18

SHEEP:
Biting louse - Damalinia ovis
Sucking louse - (Linognathus ovillus)
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GOATS:
Biting louse - Damalinia caprae
Sucking louse - Linognathus stenopsis

Question 19

when do we see lice on sheep and goats?
signs?
risk factors?
transmission?

Answer 19

• winter months
• signs = pruritus, wool loss, > weight, (anemia)
• more severe if debilitated (malnutrition/GI parasitism)
• transmitted – direct contact
• contaminated environment (~2 weeks)

Question 20

Lice treatment, control

Answer 20

Treatment:
* permethrin (e.g. Boss Pour-On), cyfluthrin (CyLence)
* 2 treatments 10-14 days apart if non residual
* injectable ivermectin (only for sucking lice)
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Control:
* shearing
* preventive treatment in fall > just ONE treatment for prevention
* quarantine treatment ?

Question 21

Melophagus ovinus (ked)
- when do we see them?
- life cycle?
- transmission?
- clinical signs?
- prevention
- treatment

Answer 21

• winter months, poor condition
• entire 6-week life cycle on sheep/goats
• transmission – direct contact
• pruritus, stained wool > fleece damage, anemia, odour, decrease value
• shearing – removes larvae + pupae
  hot climate – kills keds (remain ventral neck, breech)
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  Treatment:
• as for lice – shearing, permethrin, cyfluthrin injectable ivermectin (not an option for biting lice)

Question 22

chorioptic mange in sheep and goats
- areas affected
- signs in sheep, goats
- signs
- when we see them?
- hosts?

Answer 22

• foot mange; scrotal mange
• reservoir is often intact males
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• alopecia, erythema, crusts, pruritus – non-wool areas:
  > sheep – scrotum, distal limbs
  > goats – lower limbs, abdomen, hindquarters
• restless, chew at feet
• temporary infertility in rams > thought to be reversible - heat associated
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• Chorioptes ovis
  – host specific
• peak numbers in winter months

Question 23

chorioptic mange
- transmission
- life cycle
- Dx
- Tx

Answer 23

• transmission – direct contact - live off host a few days
• life cycle = 2-3 weeks Diagnosis: skin scrapings at edge of lesions
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  Treatment:
  (i) topical permethrin, repeat @ 10 days
  (ii) oral moxidectin (US only)
  Note: ivermectin does not work well
  > mites live superficially, oral and injectable ivermectin wont get to these superficial layers (no pour-on approved)

Question 24

psoroptic mange for sheep and goats in canada

Answer 24

= very uncommon in Canada (annually notifiable)