Lecture 8 syngamus, hook worms

Series of Presentations on Nematodes from Veterinary Parasitology By Urquhart, Jenning

1. Strongyloidea

2. Syngamus trachea(GAPEWORM)
Definitive Host Spectrum
•Domestic fowl and game birds as pheasant
Intermediate Host
•Earthworms, snails, flies, other arthropods are
paratenic hosts
Geographic Distribution
•Worldwide
Morphology
Adults -bright red, permanently in copula forming a Y
shape; males 2-6 mm, females 5-20 mm
They are the only parasites found in the trachea of the
birds
•Eggs -morulated, with a thickened operculum at each
pole, 70-100 x 43-46 microns

6. Life Cycle (Stages)
•Eggsarepassedinthefecesofinfected
birds.Unlikeotherstrongyloids,S.trachea
larvadevelopswithintheegguntilitreaches
theL3stage.
•Infectionmayoccurinoneofthreeways.
1.ByingestionofaneggcontainingaL3(A).
2.ByingestionofthehatchedL3(B).
3.Byingestionofatransporthostcontaining
encapsulatedL3s(C).
•Followingingestion,theL3sexsheathinthe
duodenum(D)ofthefinalhost.

7. Theypenetratetheintestineandtravelfirsttotheliver
andthentothelungs(E)viathebloodstream.
Twoparasiticmoultstakeplaceinthelungswithin4-7
daysafterinfection.Adultmalesandfemalesmoveup
tothetracheaandstartcopulationinthebronchiand
trachea(F).
Eggsescapefromthevulvaunderthebursaofthe
permanentlyattachedmaleandarecarriedupthe
tracheaintheexcessmucusproducedinresponseto
infection.Theyarethenswallowedandpassedinthe
feces,completingthecycle.
Theprepatentperiodisapproximatelytwoweekswitha
rangeof12-17days.

8. Site of Infection
•Trachea
Pathogenesis/Clinical Signs
•Migrationinthelungscauses
hemorrhagesandedema
•Adultssuckbloodandmaycausebirdto
bleedout,causetracheitis;excessmucus
mayblockairpassagesleadingto
dyspneaandagapingmouthposture
•Clinicalsigns-gaping,dyspnea,head
shaking,emaciation,weakness

10. Diagnosis
•Based on clinical signs, perhaps necropsy or eggs
found in feces
Treatment
•Levamisole(narrow safety margin),
•fenbendazole(very effective, but poorly soluble so
cannot be administered in drinking water),
•ivermectin
Other Control Measures
•Keep birds off moist land where earthworms and
snails, occur
•Attempt control of wild birds
•Keep chickens and turkeys separated

11. Ancylostoma caninum
(HOOKWORM)
Definitive Host Spectrum
•Dogs and other canids (target parasite)
Intermediate Hosts
•None; usually direct life cycle with possibility of paratenic
host
Geographic Distribution
•Tropical to southern temperate, has moved into
temperate areas where there is heated housing.

12. Morphology
•Adults -anterior end bent dorsally
•Buccal capsule deep and supported by thick cuticle;
contains 3 pairs of teeth on ventral rim
•Males with copulatory bursa; 2 large lateral lobes and 2
equal spicules
•Males 1/2 inch long
•Females 1/2-3/4 inches with no vulvular flap
•Eggs -60 x 40 microns; ovoid; thin-shelled; morulate
embryo

14. Life Cycle (Stages)
•Embryonatedeggspassedinfeces;7000to28,000
eggs/day
•L1hatch,feedonbacteriainfeces;molttoL2,also
microbivorous;L3appearin3weeks
•L3ensheathed,nonfeeding,infective
•Infectbyskinpenetrationorbyingestion(thisthe
usualmethod);byingestioncouldbetranscolostral
•Infectioninvolvestransportthruthevasculature,
routedeterminedbyrouteofentry:
Infection via ingestion: larvae travel through gut wall, into
circulation, then through liver, heart, and lungs, where
penetration into alveoli occurs, then coughed up and
swallowed, finally to small intestine

15.  Infectionthroughskin:larvaepenetrateskinandintothe
circulation,thenthroughthehearttothelungswhere
penetrationintoalveolioccurs,thencoughedupand
swallowed
Somelarvaemaygodormantinthegutwallorthoracicor
abdominalmusculaturetobereactivatedlaterbysome
unknownsignal
•Transcolostralisthemostcommonmeansforpupsto
becomeinfected;
Atday4post-parturition,abitch'sarrestedL3migrateto
mammmaryglandsandareingestedbynursingpups
•Adultssecreteanticoagulentsandingestblood
(approximately.25ml/adulthookworm)frommultiple
bitesites-approximately90%ofthebloodingestedbya
hookwormpassesthroughwithoutbeingdigested
•Prepatentperiod-3to4weeks

16. Sites of Infection
Dermis (larvae)
Respiratory tract (larvae)
Small intestine (adults)
Pathogenesis/Clinical Signs
•Primarilyadiseaseofpuppies,duetopresence
ofarrestedlarvae
Dermatitis
Puppy pneumonia
Enteritis,bloodydiarrhea,bloodlossanemia
Lifethreateningforpups-mayshowsignsasearly
as2to3weeksofageinaperacutecase(puppy
crasheswithoutpriorsignsofdisease)ormayoccur
inanacutestageat3weekstoweaningwhere
thereareeggsinthefeces,bloodystool

17. Diagnosis
–Eggs in feces
–Clinical signs
Treatment
–Supportive care is often necessary, including blood
transfusions
–There is no known resistance to any approved
treatment
–fenbendazole
–pyrantel
–Ivermectin

18. Ancylostoma braziliense
Definitive Host Spectrum
•Dogs, cats
Intermediate Host
•Paratenic hosts possible; none necessary
Geographic Distribution
•Tropical, subtropical (beware in Florida, Louisiana)
Morphology
•Adults -anterior end bent dorsally
•Buccal capsule with 2 pairs of ventrally located teeth -
lateral ones being large and prominent
•Males with large lateral lobes of copulatory bursa,
spicules equal
•Males and females -about 1/4 inch long

20. Life Cycle (Stages)
–Eggsdepositedinfeces
–L1hatchwithinafewdays;L1andL2microbivorous
–L3infective,ensheathed,nonfeeding
–L3usuallyinfectthruskin
–Migratethrucirculatorysystem,heart,lungs
–Tosmallintestine,moltandmature
–Prepatentperiod-about3weeks
Sites of Infection
»Skin,lungs-larvae
»Smallintestine-adults

21. Pathogenesis/Clinical Signs
–Dermatitis
–Pneumonia
–Enteritis; little if any blood loss anemia
–Not life-threatening
Diagnosis
–Eggs -one of largest of hookworm eggs
–Larvae could be cultured
Treatment
–Fenbendazole
–Milbemycin
–Pyrantel
Public Health Significance
–Cutaneous larval migrans (CLM) known as "plumber's
itch"

22. Uncinaria stenocephala
Definitive Host Spectrum
•Dog and other canids, cats
Geographic Distribution
•Northern temperate zones, including Missouri, although
less prominent than A. caninumhere
Morphology
•Adults -anterior end bent dorsally; buccal capsule bowl-
like, pair of cutting plates on ventral margin; male bursa
with 2 large lateral lobes and 1 small dorsal lobe; spicules
are equal, filariform; males 1/4 inch long; females 1/2 inch
•Eggs -80 x 45 microns; ovoid; thin-shelled; morulate
embryo

23. Life Cycle (Stages)
–Adults in posterior 1/3 small intestine
–Eggs passed in morulate stage
–Most eggs hatch in 1 week
–L 1 , L 2 microbivorous
–L 3 ensheathed, infective; usually by oral route
–No extraintestinal migration
–Prepatent period -2 weeks
Site of Infection:Posterior 1/3 small intestine -low numbers
Pathogenesis/Clinical Signs
•Some inflammation, little if any blood loss, low
significance
Diagnosis:Eggs
Treatment
•Benzimidazoles-very susceptible
•Pyrantel
•Milbemycin
–May be difficult to treat successfully

24. Bunostomum spp. (HOOKWORMS OF
RUMINANTS)
Definitive Host Spectrum
–Specific for cattle, sheep, goats
Intermediate Hosts
–None of significance; usually direct life cycle
Geographic Distribution
–Worldwide
Morphology
–Adults -anterior end bent dorsally
–Buccal capsule with 2 pairs of ventral cutting plates
–Copulatory bursa with 2 lateral lobes, slightly developed
asymmetrical dorsal lobe, spicules equal
–Males 10 -12 mm long
–Females 16-19 mm long

25. Life Cycle (Stages)
–Eggs passed in feces
–L 1 hatches in 1-2 days; reach ensheathed L 3 in 1 week
–L 3 penetrate skin; go thru heart, lungs, molt to L 4 in lungs
–L 4 passed to small intestine, molt, mature
–Prepatent period -2 months
Sites of Infection
–Dermis, lungs -larvae
–Small intestine –adults
Pathogenesis/Clinical Signs
•Possibly dermatitis
•Possibly pneumonia and enteritis, blood loss anemia

26. Diagnosis
–Eggs
Treatment
–Benzimidazoles
–Ivermectin, doramectin, eprinomectin
–Levamisole
Other Control Measures
–Rotation of pastures
–Strategic deworming along with other
gastrointestinal nematodes
Public Health Significance
–None