Nematoda

VMP 920Infection & Immunity II

Veterinary Parasitology

Haemonchus contortus

Barber-pole worm (Haemonchosis) Morphology

Dimorphic Male (bursate) & Female Nematodes

Life Cycle

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

Severe pallor (anemia)Facial edema“Bottle-jaw”

Pathology

Morbidity & Mortality

Pathology@ necropsy

Severe pallor (anemia)throughout organs

Very thin, non-clotting blood

Abundant wormsin 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

• 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 is an acronym derived from the name of the creator of this system, Dr. Faffa Malan; CHA stands for chart.

FAMACHA

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 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

EquineSmall Strongyles

over 40 species Dimorphic Male (bursate) & Female

Nematodes

Life Cycle

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 CycleArrested (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 negativein 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 Post-treatment 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