Nematodes of Dogs & Cats
Toxocara sp.
Significance
• the most important parasites
• infection at birth
• death: first two weeks (lung migration)
• larval migration
Morphology
male
female
=
=
4-10 cm
5-18 cm
T. canis
cervical alae:
- long & narrow
- semilanceolate
cervical alae:
- broader
- arrow head
Life cycle
• modes of transmission: T. canis
• transplacenta
• transcolostrum
• direct ingestion
• paratenic host
Direct life cycle
10-15 d
tracheal migration
age < 3 mths
prepatent period
4-5 weeks
Indirect life cycle
(age > 3 mths)
prepatent period
3-5 weeks (neonates)
10-15 d
somatic migration
transplacenta
transcolostrum
paratenic hosts
> 42 d gestation
Life cycle
• Toxocara cati:
• direct ingestion
• paratenic host
• no prenatal transmission
Effect on host
• adult: no clinical signs
• puppies: severely affected, pneumonia
signs: vomiting, emaciation, potbelly,
obstruction, dull coats
death: 2-3 weeks after birth
Diagnosis
T. canis
T. cati
Infective stage
Ascarid egg
SEM differentiation
large, coarse pitted surface
small, fine pitted surface
Uga et al., Vetrinary Parasitology 92(2000): 287-294
Treatment
ivermectin
fenbendazole
pyrantel
dichlorvos
febantel
piperazine
• Saprophytic soil fungi
• Paecilomyces sp.
• Ovicidal activity of T. canis
(Basualdo J.A., 2000)
• Use of ivermectin during pregnancy
1) dose: 300 mcg/kg on day 0, 30,
and 60 of gestation
- reduce # worms by 90%
- reduce # eggs by 99.8%
• Use of ivermectin during pregnancy
2) dose: 300 mcg/kg on day 0, 30,
60 of gestation, 10 d post whelping
- reduce # worms by 100%
- no eggs were passed in environ.
(Payne P.A., 1999)
• Selamectin
• topical administration
• dose: 6 mg/kg (6-12 mg/kg)
• reduce # adults by 93.9-98.1%
• reduce # eggs by 90-95%
(McTier T.L., 2000)
Control
• good sanitation
• regular deworming
• anthelmintics:
•2, 4, 6 weeks
of age
Public Health
• visceral larva migrans (T. canis):
• children: chronic granulomatous
– liver, lung, brain, eye
• ocular larva migrans
• choroidoretinitis
Toxascaris leonina
(arrowhead worm)
head: lanceolate cervical alae
male: up to 7 cm
female: up to 10 cm
Life cycle
• transmission:
• direct ingestion
• paratenic host
• no larval migration
• prepatent period = 8-10 weeks
Effect on host
• puppy: potbelly, intermittent diarrhea,
poor condition, intestinal obstruction
Diagnosis
T. canis
T. leonina
Treatment
piperazine
dichlorvos
pyrantel
fenbendazole
febentel + praziquantel
Ancylostoma caninum
(Hookworm)
Ancylostoma caninum
• Geographic
distribution
– temperate
climates
– worldwide
• Significance
– very important
– causes deaths
(all ages)
– causes heavy
blood losses
Morphology
• worms: red or gray
• size: up to 1.6 cm
• mouth: 3 pairs of
prominent teeth
Life cycle
modes of infection:
1. eating (infective eggs)
2. skin penetration (larvae)
tracheal migration
Life cycle
modes of infection:
• intrauterine infection
• transcolostrum
• paratenic host
prepatent period = 15-18 days
H
O
O
K
W
O
R
M
S
A
N
C
Y
L
O
S
T
O
M
A
คัน!
moist eczema
&
ulceration
Larval penetration
effect
on
dog
“pale mucous membrane”
effect
on
dog
“severe blood loss”
effect
on
dog
blood vessels rupture &
hookworms feed on the
released blood (0.25 ml/day)
Ancylostoma caninum
Clinical signs
• factors: dose, age, immune status
• dermatitis
• puppy pneumonia
• diarrhea: dark in color (blood & mucus)
Clinical signs
• severe blood loss:
•iron-deficiency anemia
•edema, weakness, weight loss
•poor coat condition
heavy infection:
frequently fatal
within 2 weeks of
birth in puppies
Diagnosis
• clinical signs
• fecal examination:
•fresh direct smear
60 x 40
microns
•simple floatation ovoid, thin-shelled,
morulate embryo
Treatment
• supportive care: blood transfusions, iron
supplement
• anthelmintics: fenbendazole, ivermectin,
tetrahydropyrimidine (pyrantel)
• Ivermectin + pyrantel
• ivermectin = 6 mcg/kg
• pyrantel pamoate = 5 mg/kg
• 99.6 % reduction of adult
hookworms
(Nolan T.J. et. al, 1992)
• Doramectin
• 1 mg/kg on d30 of gestation
reduce somatic larvae in bitches
and adult hookworms in bitches
and puppies
(Schnieder, T. et al, 1996)
• Moxidectin
• 1 mg/kg on d55 of gestation
(5-8 d before parturition):
completely prevent lactogenic
infections in puppies.
(Epe, C., 1999)
Deworming program
• CDC recommendation:
rd
• bitch: fenbendazole in the 3
trimester (kill migrating larvae)
• pups: 2, 4, 6, and 8 weeks of
age
Control
• feces elimination
• keep kennel-floor dry
• regular deworming
• treat bitch with ivermectin
Effect on man
• Adult Ancylostoma caninum
•excretory/secretory antigens
•causes hypersensitivity in man
•human eosinophilic enteritis
Cutaneous larval migration
Cutaneous larval migration
Trichuris vulpis
(whipworms)
Morphology
size: 4.5-7.5
cm.
anterior part: 3/4 of body, long & slender
Life cycle
• location: caecum
• infection: direct ingestion of
infective egg
L
I
F
E
C
Y
C
L
E
prepatent period = 11-12 weeks
T
R
I
C
H
U
R
I
S
Effect on host
• intestine: irritation of caecum & large
intestine
• profuse diarrhea, loss of weight,
unthriftiness
• anemia in heavy infection
Diagnosis
70-90 x 30-40 microns
Lemon-shaped with bipolar plugs
Treatment
mebendazole
dichlorvos
fenbendazole
febantel
avermectins are not as effective.
Spirocerca lupi
(esophageal worm)
• Definitive host
• dogs
• Intermediate host
• coprophagous beetles
• lizards, chickens, mice
(paratenic host)
morphology: red, coiled nematode
3-8 cm long
esophagus
thoracic aorta
coeliac artery
gastroepiploic artery
prepatent period
5-6 mths
adults in nodule
(L1)
beetles
encyst larvae
(L3)
Effect on host
• larval migration: aorta
•haemorrhage
•granuloma, stenosis
•aneurysm, rupture
Effect on host
• adult: embedded
in the walls of
aorta, esophagus
and stomach
Effect on host
• adult: nodules, tumor
• nodules: interfere
with swallowing,
respiration and
circulation
• signs: persistent
vomiting, wt. loss,
hemoptysis
• aneurysm burst
causes sudden
death
“esophageal sarcoma”
10% of infected dogs
Diagnosis
•
•
•
•
floatation method
radiography
endoscopy
necropsy
Diagnosis
• egg: small, oblong in shape,
thick-shelled, larva inside
30-38 x 11-15 microns
Treatment
• fenbendazole
• avermectins
Control
• isolate infected animals
• dispose of the vomit and feces
• keep dogs from eating beetles,
paratenic hosts
Strongyloides stercoralis
(threadworms)
Morphology
• parasitic stage: pathenogenetic female
• size: 2-9 mm. long
• filariform esophagus
Life cycle
• host: dogs, cats, men
• direct life cycle: free-living, parasitic
• prepatent period = 7 days
Life cycle
• modes of infection:
• skin penetration
• ingestion (rare)
• hyperinfection (mucosal migration)
• autoinfection (perianal area)
Significance
• reinfection: kennel situation
• causes severe disease only in
young animals
• heavy infection: death in puppies
Effect on host
• skin: dermatitis
intestine: irritation, catarrhal
inflammation, mucosal erosion,
necrosis
signs: diarrhea (blood), low appetite,
weight loss, dehydration, weakness,
death
lung migration: alveoli destruction,
ecchymotic hemorrhage, pneumonia
Diagnosis
• fecal examination
•larvae, eggs containing larvae
40-50 microns
Treatment
Dichlorvos
Fenbendazole
Control
clean & dry floor
Gnathostoma spinigerum
G. spinigerum
• size: 1-3 cm. long
• head bulb: “ballonets”
• head & anterior part: spines
Life cycle
•
•
•
•
prepatent period: 7 months
st
1 int. host: Cyclops
2nd int. host: fresh water fish, reptiles
location: stomach
Gnathostoma spinigerum
cats, dogs
nodule in the gastric wall
eggs (L1)
fish, frog, snake (L3)
man
Cyclops (L2)
Effect on host
• Cutaneous larva migrans:
– cause intermittent, migratory,
painful, priritus swelling
Effect on host
• visceral larva migrans:
• cough, hematuria,
• ocular involment
• eosinophilic meningtitsis
• myeloencephalitis
Pathogenesis
• larval migration: liver damage,
mesentery, diaphragm, thoracic cavity
• adult: migrate in stomach wall
• cavity, pus, cyst
Diagnosis
• egg: rare in feces
Treatment
• no specific drug (albendazole)
Physaloptera praeputialis
Morphology
• size: 1.5-4.8 cm long
• body: large, thick, stout nematodes
• egg: contain a larva when laid
Life cycle
• host: dogs, cats, other carnivores
• intermediate hosts:
•crickets, cockroaches, beetles
• prepatent period = 41-83 days
• location: stomach,
duodenum
• worldwide distribution
Effect on host
• adult
•irritation: firmly attach to the lining
of the gastric mucosa
•bleeding, mucosa erosion
•digestion interference
Clinical signs
• loss of condition
• vomiting (possibly bloody, mucoid)
• anorexia
Diagnosis
• fecal examination (floatation)
•small, oblong eggs containing
larvae
40-58 x 30-34 microns
Treatment
• anthelmintics
•dichlorvos, benzimidazoles,
avermectins
• control pets’ eating habits