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Parasitology > Strongyloides > Flashcards

Strongyloides Flashcards

1
Q

Strongyloides species

A
  • S. ransomi: swine
  • S. westeri: equids
  • S. papillosus: ruminants
  • S. stercoralis: canids
  • S. tumefaciens: felids
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2
Q

Strongyloides classification

A

Order: Rhabditida

  • rhabditiform esophagus: bulb, isthmus, corpus
  • free living stages (L1 and L2) have rhabditiform esophagus
  • precede infective stage (L3)
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3
Q

Heterogonic ______ life cycle

A

Free living, rhabditiform larvae (L1)

  • L1 in eggs passed in feces
  • L1 and L2 in feces
  • filariform larvae (L3) in contaminated soil
  • free living male and female adults
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4
Q

Homogonic _____ life cycle

A

Parasitic, filariform larvae (L3)

  • larvae in contaminated soil penetrate skin
  • infective L3 larvae
  • parthenogenesis: parasitic females only! clones of eggs
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5
Q

Percutaneous route

A

L3 penetrate skin –> circulatory –> lymphatic system –> lungs –> alveoli –> migrate or coughed up and swallowed –> mature in SI

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6
Q

Preoral route

A

Penetrate oral mucosa and migrate or ingest infective L3 and go directly to SI

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7
Q

Transmammary route

A

Some larvae arrest

  • reactivated after parturition
  • migrate to mammary glands, ingested by neonates
  • no extraintestinal migration
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8
Q

Transplacental route

A

Reactivated larvae migrate to fetus in utero

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9
Q

Strongyloides ransomi infection

A

Infection in all age groups

  • percutaneous or peroral: filariform larvae, tracheal migration to maturation or somatic migration that accumulate as arrested larvae (adipose tissue, esp. mammary tissue)
  • mature gilts: store larvae in adipose tissues, shed larvae later in colostrum and milk
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10
Q

Strongyloides ransomi transmammary infection

A

Key to epidemiology in swine!!

  • larvae in colostrum and milk
  • larvae arrive at intestinal mucosa without migration
  • shorter PPP
  • nursers: eggs found 2-4 days after birth, initial transmammary infection contaminates environment, augments mature worm burden of piglets, rebuilds sows tissue store of arrested larvae for next litter
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11
Q

Transplacental infection

A

Larvae also transmitted directly to fetuses, presumably during periparturient period

  • shorter PPP
  • piglets separated from sow at birth
  • reared artificially, no eggs in feces
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12
Q

Strongyloides ransomi - clinical signs

A

Pathogenicity usually in nursing piglets

  • inapparent in older animals
  • skin: erythema, pustules, peak at 2-3 weeks and disappear at 5-6 weeks
  • acute enteritis: bloody diarrhea, anemia, severe weight loss with economic loss
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13
Q

Strongyloides ransomi - treatment and prevention

A
  • Benzimidazoles and levamisole: effective against intestinal infections, administered in feed before/after parturition to reduce lactogenic transmission to suckling piglets
  • Ivermectin: effective against adults, give to sow 1-2 weeks before farrowing to suppress larval excretion in milk
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14
Q

A high level of hygiene is necessary to diminish ________

A

Larval development

- also need multiplication of free living generations in pens

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15
Q

Strongyloides westeri - general characteristics

A

Mostly in suckling and weanling foals

  • dam of infected foal does not shed eggs!!
  • transmammary transmission is most important: foals shed eggs at 10-14 days after birth
  • infections peak at 4-6 weeks, disappear at 20-25 weeks
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16
Q

Strongyloides westeri - clinical signs

A

Catarrhal enteritis, diarrhea (foal heat)

  • not related to alteration in chemical composition of mare’s milk due to first postparturient estrus of mare
  • heavy infection in foals persists 10 weeks, lighter infection may last 2-3 x longer
  • may see light infection in yearlings and older horses
  • percutaneous infection in hosts not exposed as sucklings
17
Q

Strongyloides westeri - zoonotic potential

A

Creeping eruption

  • allergic response to free living L3 in humans
  • repeated exposure, hypersensitivity, swollen hand
  • also seen with S. ransomi and S. papillosus –> CLM
18
Q

Strongyloides papillosus - clinical signs

A

Occurs in warmer climates

  • peak in 1-3 month old calves and 2-6 week old lambs
  • diarrhea
  • ataxia due to brain lesions in goats, sheep
  • calves, lambs: cardiac arrest associated with adult stages
  • anorexia
  • percutaneous transmission: bacteria more readily enter interdigital skin (foot rot)
19
Q

S. ransomi, S. westeri, S. papillosus - diagnosis

A
  • fecal float: do not collect feces from ground!
  • eggs are oval, thin shelled
  • adults: small, embedded in SI mucosa, need a skin scraping of mucosa
20
Q

S. ransomi/westeri/papillosus - treatment and control

A

Maintain clean, dry environment

- larvae cannot survive drying for 5 minutes or direct sunlight for 1-2 hours

21
Q

Strongyloides stercoralis autoinfection

A

Rare, happens only if bitch is infected while lactating

  • hyperinfection, or uncontrolled autoinfection is also rare
  • corticosteroid use
  • other factors that affect immunocompetence
  • immunocompromised dogs or neonates
22
Q

S. stercoralis - diagnosis

A

Third stage larvae (L3)
- autoinfective L3a
- infective L3i
L3a: develop within intestine of dog, invade dog thru wall of LI
L3i: develop in environment, invade dog thru skin

23
Q

Strongyloides stercoralis - clinical signs

A

Inapparent in older animals, could be asymptomatic to serious

  • dermatitis
  • catarrhal enteritis
  • necrosis of intestinal mucosa
  • mucoid or blood diarrhea
  • dehydration
  • bronchopneumonia
  • death
24
Q

Strongyloides stercoralis - diagnosis

A
  • autoinfective L3a in lung of host (blood filled alveolar spaces)
  • only a few L3a can cause severe lung damage
25
Q

Strongyloides stercoralis - diagnosis stage

A

L1 in feces of infected host!

- pointed tail, short mouth tube, very large genital primordium

26
Q

Which technique is used to find L1?

A

Baermann technique

- use fresh L1, can be stained with iodine solution

27
Q

Stronglyoides stercoralis differentials

A
  • L1 of Ancylostoma caninum

- Filaroides osleri

28
Q

Strongyloides stercoralis - adult diagnosis

A

Mucosal scraping, looking for parasitic females (long esophagus)

  • immunofluorescent antibody test
  • ELISA
29
Q

Strongyloides stercoralis tends to be a _____ problem

A

Kennel

  • summer with hot/humid weather
  • usually, infections are associated with warm, wet, crowded, unsanitary housing
30
Q

S. stercoralis zoonotic potential

A

Cutaneous larva migrans

  • isolate infected dogs
  • possibly intestinal infections in humans
  • species found most often in dogs is identical to that found in people
31
Q

Strongyloides stercoralis - treatment and control

A

Dogs: off label anthelmintics, monitor fecals monthly for 6 months after first neg fecal

  • maintain clean, dry environment
  • larvae cannot survive drying for 5 min, direct sunlight for 1-2 hours
32
Q

________ is the treatment of choice in dogs with naturally acquired Strongyloides stercoralis infection

A

Fenbendazole

33
Q

Strongyloides tumefaciens

A

Affects cats in US (rare)

  • unknown life cycle
  • grossly visible tumor like nodules in large intestine
  • rhabditiform larvae

Parasitology (28 decks)

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