Parasitology - Visceral Larva Migrans

1. VISCERAL
LARVA
MIGRANS

2.  typically found in young children.
 occurs when a nematode larvae gain
entry to extraintestinal viscera of the
host.
 results in phagocytic attack on the
larvae.
 caused by: Toxocara canis
Toxocara cati

3. Toxocara canis (dog ascarid)
• DH: Dogs and other canids
• PH: Rodents
• AH: Human
Morphology
o Male
 4-6 cm long
 posterior end is curved ventrally
 tail is bluntly pointed
 single tubular testis
 simple spicules (allows for direct
sperm transfer)

4. oFemale
 6.5-10 cm long
 has ascarid lips
 cervical alae are longer than
broad
 vulva is about 1/3 of the
body length from the anterior
end
 ovaries are very large and
extensive
 uteri contain up to 27 million
eggs

5. o Eggs
 85x75 µ
 subglobose and pitted
superficially
 dark brown in color
 unembryonated when laid
 very resistant to various
weather and chemical conditions.

6. Life Cycle

7. Cross-section of Toxocara
Larvae in liver tissue

8. Toxocara cati (cat ascarid)
• DH: Cats
• PH: Earthworms, Ants and Other soil-
dwelling invertebrates
• AH: Human
Morphology
o Male
 4-6 cm long
 has typical slender shape
 thin head and tail
 has simple chitinous spicules

9. o Female
 4-12 cm long
 has ascarid lips
 pair of broad, lateral cervical
alae
 large ovaries
 uteri contain up to 30 million
eggs

10. o Eggs
 65x70 µ
 almost spherical in shape
 thin shelled and delicately
pitted
 contain single cell

11. Life Cycle

12. Symptoms
 Physical symptoms: includes fatigue,
anorexia, weight loss, pneumonia, fever,
cough, bronchospasm, abdominal pain,
headaches, rashes, and, occasionally
seizures
 Clinical symptoms: depend on the
localization and degree of pathological
changes and include non-specific and
varied conditions such as eosinophilia,
leukocytosis, hepatomegaly, mild
gastrointestinal disorders, asthmatic
attacks, pneumonic symptoms, urticarial
skin changes, central nervous disorders
with paralyses

13. Diagnosis
 Clinical Picture – ectopic foci
 ELISA using secretory excretory
antigen
 Biopsy – liver (demonstrate the
characteristic granuloma surrounding
a juvenile)
 Serology – hemagglutination test
– microprecipitation test

14. Prevention
• Periodic deworming of household
dogs and cats
• Wash your hands with soap and
water after playing with your pets or
other animals, after outdoor
activities, and before handling food.
• Clean your pet's living area at least
once a week.
• Prevent children from eating dirt.