Transcript Symbiosis - NCSU Veterinary Parasitology

VMP 920
Infection & Immunity II
Veterinary Parasitology
Nematoda
Haemonchus contortus
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Barber-pole worm (Haemonchosis)
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Morphology
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Dimorphic Male (bursate) & Female Nematodes
Life Cycle
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Life cycle image
Life Cycle
Direct Life Cycle (Goats & Sheep - abomasum)
• Transmission -- ingestion of infective larvae (L3)
(deadly dew-drop)
• From eggs in feces to infective L3 takes 4-6 days on
pasture
• Pasture-borne parasite
• 3 week prepatency
• But peracute dz in young hosts in less than 1 week
Life Cycle
Arrested (hypobiotic) larvae in host
• Survive harsh seasons
• Periparturient rise “targets” very young animals
• Premunition
• Inhibits development of arrested larvae
• May result in Post-treatment DZ
Pathology
• Hemorrhagic anemia
• Hypoproteinemia
Facial edema
“Bottle-jaw”
Severe pallor (anemia)
Pathology
Morbidity & Mortality
Pathology
@ necropsy
Severe pallor (anemia)
throughout organs
Very thin,
non-clotting blood
Abundant worms
in abomasum
Pathology – Peracute DZ
• “extremely large number of immature
worms”
• FWEC = 0 epg to very low epg (eggs per gram of feces)
• young goats, lambs exsanguinated before
worms mature.
• Severe hemorrhagic gastritis.
• May remove 1/5 of circulating erythrocyte
volume per day.
• Sudden death from acute blood loss.
Pathology – Acute DZ
• 1,000 to 10,000 worms
• FWEC = As high as 100,000 epg
• Young susceptible animals become heavily
infected.
• Anemia develops rapidly.
• Expansion of the erythropoietic response.
• Generalized anemia and hypoproteinemia.
• May remove 1/10 of circulating
erythrocyte volume per day.
Pathology – Chronic DZ
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100 to 1,000 worms
FWEC = <2,000 epg
Older animals
100% morbidity but low mortality
Morbidity depends on animal’s
erythropoietic capacity, iron and
nutritional metabolic reserves.
Anemia & Hypoproteinemia may or may
not be severe.
Clinical Signs &
Diagnosis
• Signs of anemia, tarry feces, pale mucus
membranes, bottle-jaw, (not diarrhea)
• McMasters = Fecal Worm Egg Count (FWEC)
• At what FWEC would you treat?
• Resistance/Efficacy check with McMasters.
• FAMACHA = “Grade” of pale mucous
membranes
Clinical Signs &
Diagnosis
SHEEP or GOAT
Clinical Signs &
Diagnosis
Normal feces
Clinical Signs &
Diagnosis
McMasters Quantitation
Fecal Worm Egg Count
(FWEC)
Strongyle-type eggs
Clinical Signs &
Diagnosis
FAMACHA
FAMACHA is an acronym derived from the name of
the creator of this system, Dr. Faffa Malan; CHA stands for chart.
For Grading pallor of mucous membranes
Treatment
• Fenbendazole, Pyrantel, Ivermectin, etc.
• Dewormer Resistance a major problem
• Spring treatment of pregnant females to
target periparturient rise.
Control
• Pasture “Sanitation” (impractical)
• Regular scheduled Deworming [Ex. Deworm
monthly] (may result in resistance)
• Pasture rotation (requires 2-6 month rest =>
much land needed)
• Co-species grazing
• Test (McMasters) & Treat (selective deworming)
• FAMACHA, Test & Treat (selective deworming)
– provides refugia
=> inhibit large population of resistant worms.
- slows development of resistant worm population
Control:
McMasters
McMasters Quantitation
Strongyle-type eggs
• Use for making selective deworming decisions
• deter resistance & promote refugia
• Use to identify hosts that shed a lot of worm eggs
• Use to determine dewormer efficacy
Control: FAMACHA
• Use for tactical deworming
• Use for making selective deworming decisions
• deter resistance & promote refugia
Control
• Refugia image
Challenges to Control
 Infective Larvae on Pasture
 Hypobiotic Larvae in Host
 Worm resistance to Dewormers
 Prevent “contamination” of
pasture & host through selective
strategic deworming.
Important Points
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Direct Life Cycle – Pasture-borne parasite (L3) (deadly-dewdrop)
 Sanitation by deworming strategy.
Special life cycle concerns: Prepatent period, Hypobiotic larvae
“overwinter”, Peripartureint rise  targets neonates.
Blood-feeding worms  Pathology (Peracute, Acute, Chronic) 
anemia. Clinical Signs.
Diagnostics: Response to treatment, McMasters & FWEC,
FAMACHA
Control: Advantages & disadvantages of each control strategy.
Control: Understand concept of refugia to inhibit resistant
populations
Equine
Small Strongyles
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over 40 species

Dimorphic Male (bursate) & Female
Nematodes
Life Cycle
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Life cycle image
Life Cycle
Direct Life Cycle (Horse – large intestine)
• Transmission -- ingestion of infective larvae (L3)
(deadly dew-drop)
• From eggs in feces to infective L3 takes 4-6 days on
pasture
• Pasture-borne parasite
• 2.5 to 3 months prepatency
Life Cycle
Arrested (hypobiotic) larvae in host
• Premunition inhibits development
• “prepatency” of arrested larvae
- as few as 18 days post-reactivation
• Post-treatment DZ
• Periparturient rise “targets” very young
animals
Pathology
Mainly caused by emerging larvae.
• Acute -- severe enteritis & diarrhea,
hypoalbuminemia
• Post-treatment -- severe enteritis,
colitis & diarrhea, hypoalbuminemia
• Chronic -- granulomatous colitis
ACUTE
Pathology
Severe Colitis
Clinical Signs &
Diagnosis
• Persistent diarrhea, edema, poor body condition,
COLIC
• McMasters = Fecal Worm Egg Count (FWEC)
• At what FWEC would you treat?
• Will only show adult burden, not DZ causing
emerging larvae.
• Resistance check with McMasters.
Clinical Signs
Signs of colic
Diarrhea
Diagnosis
McMasters Quantitation
Fecal Worm Egg Count
(FWEC)
Strongyle-type eggs
(maybe negative
in acute pathology)
Treatment
• Fenbendazole, Pyrantel, Ivermectin, etc.
• Dewormer Resistance a major problem
Control
• Pasture “Sanitation” (removal of feces)
• Regular scheduled Deworming [Ex. Deworm
every 2 months] (may result in resistance)
• Pasture rotation (requires months of rest =>
much land needed)
• Co-species grazing
• Test (McMasters) & Treat
– provide refugia
=> inhibit large population of resistant worms.
- slows development of resistant worm population
Challenges to Control
 Infective Larvae on Pasture
 Hypobiotic Larvae in Host
 Worm resistance to Dewormers
 Prevent “contamination” of
pasture & host through selective
strategic deworming.
Important Points







Direct Life Cycle – Pasture-borne parasite (L3) (deadly-dewdrop)
 Sanitation by deworming strategy.
Special life cycle concerns: Prepatent period adult worms &
Arrested larvae, Hypobiotic larvae  “overwinter”, Peripartureint
rise  target young, Premunition + Arrested larvae  Posttreatment DZ
Emerging larvae  Pathology (Acute, Post-treatment, Chronic),
Clinical Signs – COLIC, Enteritis
Diagnostics: McMasters & FWEC,
Control: Advantages & disadvantages of each control strategy.
Control: Understand concept of refugia to inhibit resistant
populations