Superfamily Trichostrongyloidea Flashcards
(29 cards)
1
Q
Superfamily Trichostrongyloidea
A
- Parasites of grazing animals
- Usually found in the GI tract (abomasum and anterior small intestine) = “predilection site”
- Direct life-cycle
- Hair worms, wire worms, and thread-necked worms
- Mixed infections are common
2
Q
Trichostrongyloidea adult morphology
A
- Buccal capsule (small or absent)
- Small to medium size worm (5-8 mm - 20-30 mm)
- Cuticular specializations
- Well developed male bursa with spicules
3
Q
Trichostrongyles of ruminants
A
Abomasum
- Haemonchus spp. (sheep, goat, and cattle)
- -Largest
- Marchallagia sp. (sheep and goat)
- Ostertagia spp. (cattle)
- Teladorsagia spp. (sheep and goat)
- Trichostrongylus axei (sheep, goat, and cattle)
- -Smallest
Small intestine
- Nematodirus spp. (sheep, goat, and cattle)
- -Largest
- Cooperia spp. (sheep, goat, and cattle)
- Trichostrongylus spp. (sheep, goat, and cattle)
- -Smallest
4
Q
Trichostrongyle-type eggs (except Nematodirus spp.)
A
- Eggs of different genera look alike
- 70-100 um x 35-50 um
- Oval to ellipsoidal shape
- Thin-shelled
- Smooth
- Colorless
5
Q
Nematodirus spp. eggs
A
- 150-230 um x 80-100 um
- Oval to ellipsoidal with tapering ends
- Thick-shelled
- Smooth
- Colorless
6
Q
Trichostrongyle life-cycle
A
- Adults in the abomasum and small intestine
- Trichostrongyle type eggs in feces (4-32 cell stage morula)
- After 1-2 days, L1 hatch and feed on microbes (EXCEPTION: Nematodirus L3 hatch from the egg)
- L3 (infective larvae) are ingested
- Penetrate the abomasal glands or small intestinal mucosa
- L4 exit to the lumen
- Develop to adults in the abomasum and small intestine
- -No migration occurs inside the animal
7
Q
Trichostrongyle ecology and epidemiology
A
- Development on pasture is crucial to epidemiology
- “Cool weather group”
- -Trichostrongylus spp., Ostertagia, and Teladorsagia spp.
- –Larvae can overwinter on pasture
- –Optimal temperature range for L3 development (40-70)
- “Warm weather group”
- -Haemonchus spp. and Cooperia spp.
- –Optimal temperature range for L3 development (60-100)
- –Haemonchus spp. - not just tropical/subtropical distribution
- Nematodirus spp.
- -Hatching of infective L3 requires an environmental stimulus (cold shock), then warm temperatures for hatching in certain species
- -Thus usually only one generation per year (spring)
8
Q
Trichostrongylus spp.
A
- 5-8 mm
- Trichostrongylus axei (cattle, sheep, goats, horses, pigs)
- Trichostrongylus spp. (sheep, goats, cattle)
- Same parasite crosses multiple hosts
9
Q
Cooperia spp.
A
- 5-6 mm
- Cooperia punctate (cattle)
- Cooperia oncophora (cattle and sheep)
- Cooperia curticei (sheep and goats)
10
Q
Nematodirus spp.
A
- 15-25 mm
- Nematodirus helvitianus (cattle)
- Nematodirus spathiger (cattle, sheep, goats)
- Nematodirus filicolis (cattle, sheep, goats)
- Nematodirus battus (sheep, goats)
11
Q
Ostertagia, Teladorsagia, and Trichostrongylus spp. pathogenicity
A
- Affects food intake
- Protein absorption and utilization
- Protein-losing enteropathy
12
Q
Haemonchus spp.
A
-Blood feeders (result in anemia)
13
Q
Nematodirus spp.
A
- Induce hypersensitivity
- Shedding of villi (affects absorption of nutrients)
- Diarrhea
14
Q
Trichostrongyle clinical signs and disease
A
- Some species cause more noticeable clinical signs and severe disease than others
- Synergism among trichostrongyles
- -Mixed infections are common
- -In such cases, renders pathogenic net effects of species of (normally) low pathogenicity
- Subclinical mixed infections are especially important due to:
- -Poor feed efficiency
- -Decreased weight gains
- Economic losses (can be very significant)
15
Q
Ostertagia morphology
A
- Cattle only
- Cervical papillae
- Spicules (with equal shape and length) in males
- Cuticular striations
16
Q
Ostertagiasis clinical signs and disease
A
- Ostertagia ostertagi of cattle
- Most important helminth parasite of cattle in the US
- Type I
- -L3 develop directly into adults
- -Pastured young cattle - early grazing season
- -Coincides with summer and fall
- -“Summer” ostertagiasis
- Type II
- -Hypobiotic larvae are reactivated and establish in the abomasum
- -Occurs in adult cattle
- -Coincides with late winter
- -“Winter” ostertagiasis
17
Q
Ostertagia spp. lesions of the abomasum
A
- Abomasitis
- -“Morocco-leather” appearance of abomasal mucosa (pathognomic lesion)
- -Greyish-white pinhead to peahead size nodules with worm protruding out
- Altered abomasal pH (neutrality) — Leads to:
- -Hypoproteinemia – submandibular edema (bottle-jaw in small ruminants)
- Profuse watery diarrhea
- Anemia
- Emaciated
18
Q
Haemonchus contortus morphology
A
- Female uterus and intestine spiral to resemble a “barber pole”
- -Uterus is full of parasite eggs
- -Intestine is full of blood
- Lancet or stylet at the anterior end (damages the host and pumps blood into the esophagus)
- Presence of prominent cervical papilla
- Female vulvar flap
- Male tail - copulatory bursa and barbed spicules (characteristic of Haemonchus)
19
Q
Haemonchosis pathology and disease
A
- Haemonchus contortus
- -Voracious blood-sucking
- -Multi-focal hemorrhagic abomasitis
- Anemia (leads to signs dependent on the stage of pathogenesis)
- -Acute blood loss
- -Regenerative
- -Iron-deficiency
- Hypoproteinemia
- -Blood loss
- -Protein-losing enteropathy
- -Bottle jaw
- -+/- emaciation
- -Weakness
- -Morbidity more than mortality
- -Poor body condition leads to prolonged breeding interval after lambing/kidding/calving
20
Q
Haemonchosis diagnosis
A
- Clinical signs
- Fecal exam
- Larval culture
- Necropsy findings (including parasite recovery)
- Fecal egg counts (FEC) and fecal egg count reduction tests (FECRT) sometimes used for rough estimates of treatment (can be misleading)
- Test for high, low, and no shedding
- -ONLY treat the high shedders
- Can ID larvae using Baermann technique
- Fluorescein-labeled peanut agglutinin test (fluoresces the egg and larva of Haemonchus contortus)
21
Q
Haemonchus contortus treatment and control
A
Goals:
- Decrease pasture contamination
- Prevent exposure to heavy infections
- Discourage evolution of resistance (inadvertent selection of resistance-conferring alleles)
- -Strategic (selective/targeted) deworming
- -Deworming/control programs should be designed for specific management conditions:
- –Feedlot
- –Cow-calf
- –Ewe-lamb flock
- –Larval ecology (geographic locale and climatic conditions)
22
Q
Strategic deworming
A
FAMACHA
- Scores degree of anemia in small ruminants due to Haemonchus contortus infection
- IDs those animals needing to be dewormed
- -Based on PCV
- –1-2 treatment not indicated
- –3 may need treatment
- –4-5 treatment required
- Frequency of exam depends upon season and weather
- -GI nematodes develop to the infective L3 stage faster during periods of increased temperatures and moisture
- -Increase testing frequency in warm months (weekly to biweekly)
23
Q
Determining resistance
A
DrenchRite (done at UGA)
- Larval development assay
- Exposes trichostrongyle-type eggs and L1 larvae to various concentrations of anthelmintics
- Anthelmintics are in agar wells of a microtiter plate
- The concentration of a drug that stops development of the L3 larvae is measured
- Expensive, but detects resistance to benzimidazole, levamisole, benzimidazole/levamisole combination, avermectin/milbemycin
- Repeat test every two years
- May be more cost effective when compared to price of repeating FECs
24
Q
How to differentiate Trichostrongylid nematodes
A
- Where were they collected from (on necropsy)?
- What is the size of the adult?
- Need to be able to ID Haemonchus v. Ostertagia
25
Arrested development of L4 larvae
- Also called "inhibition" or "hypobiosis"
- Slowed metabolism of L4
- Influenced by several factors
- -Immune response of the host
- -Population dynamics (are adults already present)
- -Climatic effects on L3 (winter)
- Resumption of development of L4
- -Coming of spring
- -Reproductive cycle of host
- -Clearance of adult worms from abomasum or small intestine
- --Natural clearance
- --Anthelmintic treatment
26
Spring rise and periparturient rise phenomena (arrested larvae)
- Increased fecal egg output
- -Occurs in spring
- --Around parturition (2 weeks prior to and 8 weeks after parturition)
- Mainly due to maturation of the hypobiotic L4 stages
- Guarantees:
- -Presence of infective larvae on pasture
- -At a time when population is susceptible (first season at pasture)
- Poorly understood, but hormones associated with parturition are thought to influence the phenomena
27
Self-cure phenomenon (incoming L3)
- Sudden expulsion of adult worms following ingestion of large numbers of L3 stages
- Thought to be due to abomasal/intestinal hypersensitivity reaction
- Best known for Haemonchus contortus infections of sheep
28
Premunition (adult worms)
- First season at pasture --> ingest L3 --> acquire infection
- -May result in disease and death or natural host resistance
- -Acute infection transforms to a chronic infection
- -Premunition occurs (lasts as long as infection with adult worms persists in the hosts)
- -Moderate numbers of adult worms present in the abomasum or small intestine
- --Reject incoming larvae
- --Some become adults
- --Small portion are arrested as L4
- -Lasts as long as infection of adult worms persists
- -Slow resistance by only deworming the higher population sample
29
Hypobiosis
=Slowed metabolism
