Roundworms
Parasitology IV.
Enterobius vermicularis
Ascaris lumbricoides
Trichuris trichiura
Toxocara
Ancylostoma duodenale
Necator americanus
Strongyloides stercoralis
Trichinella spiralis
Filariae
Judit Szabó
2013.
Life cycle of Toxocara
Toxocara canis,
Toxocara cati
visceral larva migrans (VLM)
definitive host:
T. canis
dog
T. cati
cat
human is accidental (dead-end)
intermediate host
transmission:
ingestion of egg (with contaminated
soil)
10-18 cm
egg
Symptoms I.
larvae in human body migrate to many
organs (liver, brain, eyes)
Ocular toxocariasis:
blindness (retinal granulomas )
eosinophilia
Symptoms II.
Visceral toxocariasis:
fever
eosinophilia
hepatomegaly
encephalitis
myocarditis
pneumonia
Diagnosis and treatment
Diagnosis:
serological reactions, demonstration
of larvae in tissues by histological
techniques
Treatment:
thiabendazole
Ancylostoma duodenale
Necator americanus
Ancylostoma duodenale (Old World hookworm)
Necator americanus (New World hookworm)
worldwide
geohelminth
2 larva stages:
rhabditiform (non infective)
filariform (infective)
7-15 mm
Life cycle of
Ancylostoma/Necator
Symptoms
ground itch: pruritic papule or vesicule
(larva entry into skin)
pneumonia (larva migration)
due to feed on blood from the
capillaries:
microcytic anemia (weakness,
headache, pallor)
Diagnosis and treatment
Diagnosis: demonstration of the egg in
the stool, occult blood in the stool
Treatment:
levamizole, mebendazole (adult
worm)
thiabendazole (larva)
Prevention:
wearing shoes
Strongyloides stercoralis
geohelminth
strongyloidiasis can occur in
tropics (mainly in Southeast
Africa)
2 mm
2 life cycles :
in humans
in soil (free-living worms)
egg
Life cycle of
Strongyloides stercoralis
Symptoms
usually asymptomatic
eosinophilia
pruritus (larval entry through the
skin)
pneumonia (larva migration)
diarrhea
Diagnosis and treatment
Diagnosis:
demonstration
of larvae from the stool
or serological reactions
(ELISA)
Trichinella
Trichinella spiralis
Trichinella nativa
Trichinella nelsoni
Treatment:
thiabendazole
Trichinosis
reservoirs: pigs (in Alaska bears)
worldwide (mainly eastern Europe)
the worm is 1-3 mm in size
vivipar (female deposits larvae)
transmission:
ingestion of raw or undercooked pork meat
Geographical distribution of
Trichinella species
Life cycle of Trichinella
Symptoms
eosinophilia
fever
muscle pain
periorbital edema
subconjunctival hemorrhages
cardial symptoms
respiratory paralysis
Diagnosis and treatment
Diagnosis:
muscle biopsy
serological reactions
Intestinal nematodes
-Enterobius
- Trichiuris
- Ascaris
transmitted by ingestion of EGGS
- Necator, Ancylostoma
- Strongyloides
- Trichinella
Treatment:
thiabendazole
transmitted by LARVAE
• rhabditiform larvae (1st, 2nd stage): noninfectious, feeding forms
• filariform larvae (3rd stage): infectious, feeding forms
NO insect vector!
Filariasis
Wuchereria bancrofti
Loa loa
Onchocerca volvulus
Dracunculus medinensis
Wuchereria bancrofti
elephantiasis
the vector is mosquito (Anopheles or
Culex)
the worm is 2-3 cm in size
vivipar (the female deposits larvae so
called microfilariae)
in the tropical area 200-300 million
people are infected
Geographical distribution of
Wuchereria bancrofti
Life cycle of Wuchereria
bancrofti
Symptoms
fever
lymphangitis
celullitis
edema (due to obstruction)
eosinophilia
Diagnosis and treatment
Diagnosis:
thick blood smear
taken at night
Treatment:
diethylcarbamazine
Prevention:
mosquito control,
protective clothing,
mosquito netting
200-300 micrometer
Loa loa
loiasis
the vector is deer fly
(Chrysops)
vivipar (the female deposits
larvae, so called
microfilariae)
the worm is 3-7 cm in size
can occur mainly in central
and west Africa
Life cycle of Loa loa
Symptoms
•eosinophilia
• subcutaneous edema
(Calabar swellings)
• the worm can occur
on the conjunctiva
Diagnosis and treatment
Diagnosis:
demonstration of the microfilariae from
the blood smear
Treatment:
diethylcarbamazine
Geographical distribution
of Onchocerca volvulus
Onchocerca volvulus
onchocerciasis (river blindness)
the vector is blackfly (Simulium)
vivipar (the female
deposits larvae,
so called microfilariae)
the worm is 3-4 cm (male)
25-40 cm (female)
can occur in Africa and Central
America
Life cycle of Onchocerca
volvulus
Symptoms
•dermatitis
• dermal nodules
• eosinophilia
• blindness
Sufferers being led by guides: in some villages
15 per cent of people may be blind.
Diagnosis and treatment
Diagnosis:
biopsy of affected skin ( demonstration of
microfilariae )
Treatment:
ivermectin
surgical
Life cycle of Dracunculus
medinensis
Dracunculus medinensis
(guinea fire worm)
dracunculiasis
there is no arthropode vector
vivipar (the female deposits larvae)
the worm is 2-3 cm (male) 1 m (female) in size
can occur in tropical area (Africa, Middle East,
India)
transmission:
ingestion of crustaceans (copepods) with drinking
water
Symptoms
inflammation of the skin (ulceration,
blistering)
the papule burns and itches
bacterial infections of the ulcer can
occur
Diagnosis and treatment
Prevention
Diagnosis: clinical (finding of the head of the worm in skin
ulcer
Treatment: extracting the worm (time-honored)
filtering or boiling
of the drinking water
Guinea worm has been
successfully eradicated
in Togo according to the
National programme
Frequent questions I.
Geohelminths:
Ascaris lumbricoides
Trichiuris trichiura
Toxocara canis/Toxocara cati
Ancylostoma /Necator
Strongyloides stercoralis
Frequent questions III.
Larvae enter the human body by
penetratring the intact skin:
Schistosoma spp. (trematodes)
Ancylostoma duodenale
Necator americanus
Strongyloides stercoralis
Frequent questions II.
Larva migration through the human lungs:
Ascaris lumbricoides
Ancylostoma duodenale
Necator americanus
Strongyloides stercoralis
Frequent questions IV.
Parasites which can cause anaemia:
Plasmodium spp.
Diphyllobotrium latum (fish tape worm)
Ancylostoma duodenale
Necator americanus
Frequent questions V.
Transplacental transmission:
Plasmodium spp.
Toxoplasma gondii