Strongyloides Flashcards
Strongyloides species
- S. ransomi: swine
- S. westeri: equids
- S. papillosus: ruminants
- S. stercoralis: canids
- S. tumefaciens: felids
Strongyloides classification
Order: Rhabditida
- rhabditiform esophagus: bulb, isthmus, corpus
- free living stages (L1 and L2) have rhabditiform esophagus
- precede infective stage (L3)
Heterogonic ______ life cycle
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
Homogonic _____ life cycle
Parasitic, filariform larvae (L3)
- larvae in contaminated soil penetrate skin
- infective L3 larvae
- parthenogenesis: parasitic females only! clones of eggs
Percutaneous route
L3 penetrate skin –> circulatory –> lymphatic system –> lungs –> alveoli –> migrate or coughed up and swallowed –> mature in SI
Preoral route
Penetrate oral mucosa and migrate or ingest infective L3 and go directly to SI
Transmammary route
Some larvae arrest
- reactivated after parturition
- migrate to mammary glands, ingested by neonates
- no extraintestinal migration
Transplacental route
Reactivated larvae migrate to fetus in utero
Strongyloides ransomi infection
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
Strongyloides ransomi transmammary infection
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
Transplacental infection
Larvae also transmitted directly to fetuses, presumably during periparturient period
- shorter PPP
- piglets separated from sow at birth
- reared artificially, no eggs in feces
Strongyloides ransomi - clinical signs
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
Strongyloides ransomi - treatment and prevention
- 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
A high level of hygiene is necessary to diminish ________
Larval development
- also need multiplication of free living generations in pens
Strongyloides westeri - general characteristics
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
Strongyloides westeri - clinical signs
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
Strongyloides westeri - zoonotic potential
Creeping eruption
- allergic response to free living L3 in humans
- repeated exposure, hypersensitivity, swollen hand
- also seen with S. ransomi and S. papillosus –> CLM
Strongyloides papillosus - clinical signs
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)
S. ransomi, S. westeri, S. papillosus - diagnosis
- 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
S. ransomi/westeri/papillosus - treatment and control
Maintain clean, dry environment
- larvae cannot survive drying for 5 minutes or direct sunlight for 1-2 hours
Strongyloides stercoralis autoinfection
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
S. stercoralis - diagnosis
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
Strongyloides stercoralis - clinical signs
Inapparent in older animals, could be asymptomatic to serious
- dermatitis
- catarrhal enteritis
- necrosis of intestinal mucosa
- mucoid or blood diarrhea
- dehydration
- bronchopneumonia
- death
Strongyloides stercoralis - diagnosis
- autoinfective L3a in lung of host (blood filled alveolar spaces)
- only a few L3a can cause severe lung damage
Strongyloides stercoralis - diagnosis stage
L1 in feces of infected host!
- pointed tail, short mouth tube, very large genital primordium
Which technique is used to find L1?
Baermann technique
- use fresh L1, can be stained with iodine solution
Stronglyoides stercoralis differentials
- L1 of Ancylostoma caninum
- Filaroides osleri
Strongyloides stercoralis - adult diagnosis
Mucosal scraping, looking for parasitic females (long esophagus)
- immunofluorescent antibody test
- ELISA
Strongyloides stercoralis tends to be a _____ problem
Kennel
- summer with hot/humid weather
- usually, infections are associated with warm, wet, crowded, unsanitary housing
S. stercoralis zoonotic potential
Cutaneous larva migrans
- isolate infected dogs
- possibly intestinal infections in humans
- species found most often in dogs is identical to that found in people
Strongyloides stercoralis - treatment and control
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
________ is the treatment of choice in dogs with naturally acquired Strongyloides stercoralis infection
Fenbendazole
Strongyloides tumefaciens
Affects cats in US (rare)
- unknown life cycle
- grossly visible tumor like nodules in large intestine
- rhabditiform larvae
