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Parasitology #2 > GI nematodes in Sheep > Flashcards

GI nematodes in Sheep Flashcards

1
Q

GI nematodes in sheep

A

-worse for younger animals
-pasture transmission
-more common and widespread clinical disease (worse in goats)
-anthelmintic resistance

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2
Q

Clinical signs of GI nematodes in sheep

A

-bottle jaw
-anemia
-death
-reduced production
-weight loss
-diarrhea

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3
Q

Peri parturient rise

A

L4 reactivation phase and egg release- occurs in Ewes when immunity goes down when they are about to lamb

After peri parturient rise, will see increased pasture larval count

Then lambs will become infected

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4
Q

Why do goats have more widespread disease than sheep?

A

-Sheep are grazers so are more exposed to parasites
-goats are browsers so less exposed and will have higher clinical disease

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5
Q

GI nematode diseases

A
  1. Parasitic Gastroenteritis- reduced weight gain and diarrhea
  2. Haemonchosis- acute aneamia, edema, lethargy, death
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6
Q

Haemonchus contortus

A

-typical trichostrongylid life cycle
-cause of disease in western Canada in ewes and lambs
-blood feeders
-Fecal egg count can be high or low

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7
Q

Clinical signs of Haemonchus contortus

A

Hyperacute: sudden death due to haemorrhagic anemia

Acute: anemia, bottle jaw, ascites, dark feces, anorexia

Chronic: weight loss, weakness, anorexia

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8
Q

Diagnosis/detection of Haeminchus contortus

A

-L3 at coproculture
-PCR/Nemabiome
-Adults at necropsy
-Fluorescein-labeled peanut-agglutinin

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9
Q

Detecting anemia

A

-Use FAMACHA system
-provides guidelines for detected anemia through colour of mucous membranes

*alternative to PCV in resource limited areas

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10
Q

Nematodirus battus

A

-develop to L3 inside egg
-eggs overwinter on pasture
-hatching triggered by sudden rise in temperature in Spring
-illness and death in lambs in PPP

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11
Q

Nematode species abundance in Western Canada

A
  1. Haemonchus
  2. Teladorsagia
  3. Trichostrongylus
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12
Q

Control of GI nematodes in sheep

A
  • maximize overall health, good nutrition and pasture management

-breed resistant hosts

-chemical treatments: limited drugs available

-strategic treatments: monitor egg counts, ID species when needed, no “one fits all”

-targeted selective treatments to slow development of drug resistance

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13
Q

Nematodes of Abomasum in sheep

A

-Teladorsagia circumcincta
-Trichostrongylus axel

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14
Q

Nematodes of sheep in small intestines

A

-Trichostrongylus colubriformis
-cooperia sp
-trichostrongylus vitrinus

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15
Q

Nematodes of large intestines

A

-Oesophagostomum spp
-chabertia ovina
-trichuris spp

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16
Q

Chemical control of GI nematodes in sheep

A

**Multi drug resistance evolving! Mechanism is unknown

  1. Benzimidazoles
    2.Macrocyclic lactones= IVERMECTIN
  2. Imidazothiazoles/Tetrahydroxypyrimidines
  3. Salicylanilides= CLOSANTEL (targeted activity)
17
Q

Anthelmintic resistance

A

A heritable reduction in efficacy of a drug against a particular species of a parasite
-ability of parasite population to tolerate dose of drug that would be lethal to most parasites in a sensitive population
-when drug efficacy is <95%

18
Q

H. contortus resistance

A

Reported to be resistance to all classes of drug

19
Q

How does anthelmintic resistance develop?

A

When a population of worms is submitted to a treatment pressure selecting for the individuals with the resistant genotype over time

20
Q

Refugia

A

**Good to try and reduce resistance

  1. Susceptible subset of population present on pasture, not exposed to the anthelmintic treatment that will subsequently re-infect the flock
  2. Population on refugia has susceptible worms, then it will dilute concentration of resistant worms delivered on pasture after treatment

**the larger the in refugia population, the less selection pressure BECAUSE resistant nematodes breeding with susceptible nematodes=dilution of resistant genes

21
Q

Factors determining the rate of resistance

A

-underdosing
-length of time used
-frequency of treatment
-pasture management (open/closed flocks)
-size in inrefugia population

22
Q

In refugia during temperate climates

A

Most parasites are in refugia due to high survival in pasture

23
Q

In refugia in clean, dry climates

A

Few parasites in refugia, resistance deveops rapidly

24
Q

Post-treatment during clean, dry environments

A

Treatments during the spring= low refugia so treatment at this time may mean high selection pressure

25
Q

Treat and move method

A

Treat and move animal to a clean pasture… will result in strong selection for resistance =DONT WANT THIS!

Instead, treat and move to contaminated pasture of leave on contaminated pasture. This allows for diluting out the resistants

26
Q

Diagnosis of antihelminthic resistance

A
  1. Suspected when there is poor response to anthelmintic treatment
    -when resistant strains make up large proportion of population
    -resistance goes undetected in early phases
    -first sign is shortening of egg reappearance period
  2. In vitro tests= low specificity, time consuming
    -egg hatch test, larval development test, larval migration test
  3. molecular markers of resistance- early stages
  4. FEC reduction test wildly used- with species ID method
    -morphology, PCR, DNA sequencing
27
Q

Fecal egg count reduction test

A

-individually for all animals in herd (pooled fecal samples; 20 animals)

-use quantitative, centrifugation Wisconsin technique

-test, treat, re test in 14 days

28
Q

Drug resistance and Fecal egg count reduction test

A

Drug resistance when FECRT is less than 95%

% efficacy= (pre treat FEC- post treat FEC)/ pre treat FEC x100

29
Q

Recommendations to reduce development of Anthelmintic resistance

A
  1. quarantine and anthelmintic treatment of purchased livestock
    -treat all incoming animals with combination of drugs, isolate and test FEC prior to introducing to herd
  2. good nutrition and management
    -lower stocking densities
    -avoid using same pasture in spring as used in fall
    -mix age groups and/or species BUT not sheep and goats
  3. minimize anthelmintic use
    -treat specific groups, not whole flock
  4. targeted selective treatment
    -leave large refugia
    -treat only those with high FEC, poor BCS, high FAMACHA scores
30
Q

How to pick for targeted selective treatment?

A
  1. Can use absolute FEC
    -treat all animals with FEC above a certain threshold
    -high shedders are major source of pasture contamination
  2. Can use proportion of shedders
    - treat only the top 20-30% of shedders
    -dont treat bottom 20-30% of shedders

Parasitology #2 (12 decks)

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