helminths Flashcards
Pathogenesis of H.heterophyes
1) Light infection: pass unnoticed
2)heavy infection: intestinal irritation
3)Excessive mucus secretion & hyperplasia of mesenteric lymph nodes
4)ectopic lesions by the eggs outside the intestine may occur leading to myocarditis, brain granuloma, and pulmonary embolism
Describe egg of H. heterophyes
1)Size: 30*15 micro
2)Shape: Oval, operculated, thick shelled, with post. knob
3)color: yellowish brown
4)Contents: mature ovum conataining miracidium
What are the intermediate hosts of H.heterophyes?
1st: pirenella conica snail
2nd: Tilapia nilotica=boulty & mugil cephalus=boury
Diagnostic stage of H. heterophyes
mature (embryonated) eggs in feaces
Infective stage of H. hetrophyes
Encysted metacercaria in fish muscle
Mode of infection of H. heterophyes
ingestion of encysted metacercaria with improperly cooked or inadequately salted : feseekh
What does paratenic host mean?
animals that harbor the parasite without further development
What is the paratenic host for D. latum?
Bears and other carnivores
Why does D. latum does not have gravid segment?
as eggs are expelled through the uterine pore
Describe egg of D. latum
1)Size: 70*50 micro
2)Shape: Oval, operculated, thick shelled
3)color: yellowish brown
4)Contents: immature ovum conataining germ cells
What are the intermediate hosts of D. latum?
1st: cyclops(water flea)
2nd: fresh water fish(salmon)
Diagnostic stage of D. latum
immature eggs and rarely terminate segments pass in feaces
infective stage of D. latum
plerocercoid larva
Clinical picture of D. latum
1) Light infection : asymptomatic
2)heavy infection: intestinal disturbances, megaloblastic anemia due to Vit. B12 intake by the parasite make it unavailable for the host –> later cause neurological sequale as peripheral neuropathy
3)massive infection(uncommon): intestinal obstruction –> cholangitis and cholecystitis
4)
D. latum treatment
1)Praziquental
2)Niclosamide
3)Vit. B12 IM injection
Define Sparganosis
Infection of human tissues by plerocercoid larva of D. proliferum and D. mansoni. Man acts as accidental host
Man act as what host in sparganosis?
Accidental host
Who is more dangerous sparganum proliferum or sparganum mansoni? explain why?
Sparganum proliferum as it multiplies by budding giving lateral branches and new larva
Clinical picture of Sparganosis
Symptoms depend on the tissue invaded and number of larvae
1)Skin: inflammatory tender swellings, which may form an abscess that can discharge the sparganum
2)eyes: conjuctivitis, peri-orbital edema
3)fever, urticaria, eosinophilia
4)Death of larvae cause intense local reaction
What are the other names of Taenia Saginata?
(Beef)Bald tapeworm
How many uterine branches are there in gravid segment of Taenia saginata?
15-30 lateral branches
How many uterine branches are there in gravid segment of Taenia solium?
5-10 lateral branches
Describe the egg of Taenia
Size: 30*40 micro
Shape: spherical with radially striated shell
colour: yellowish brown
contents: hexacanth oncosphere
Infective stage of T.saginata
Cysticercous bovis
mode of infection of T.saginata
ingestion of undercooked beef
Clinical picture of T.saginata
1)Maybe asymptomatic
2)white motile segment felt emerging from the anum unbidden causing irritation and peri-anal itching
3)intestinal disturbance
4)obstruction–> cholangitis and apendicitis
What is the stain used to identify the eggs of T.saginata
Ziehl-Neelsen
What is the stain used to identify the gravid segment of T.saginata
India ink
What is the intermediate host of Taenia Solim?
pig
What is the infective stage of T. solium
Cysticercus cellulosa
What is the most important risk in T. solium
cysticercosis
What stains are used to identify T. solium and what are the results?
1) eggs —> Ziehl Neelsen: does not stain
2)Gravid segment –> india ink –> stains
treatment of T.solium
1)Praziquental
2)Niclosamide
then bowel purge after two hours to prevent egg release from the gravid segment
medications induce vomiting are avoided –> to prevent cysticercosis from retrograde peristalsis
which host does the man act in cysticercosis?
blind intermediate host
blood picture of cysticercosis
high eosinophilia
ttt of cysticercosis
1)Albendazole (drug of choice) or praziqeuntal
2)corticosteroids are used to decrease the neurological reactions from disintegration of cysts
3)surgical removal if possible
what is the other name of H.nana?
Dwarf tapeworm
Describe egg of H.nana
size: 30-40 micro
shape: spherical with 2 coverings, from the inner covering 2 polar thickening arises from each arise 4-8 filaments
color: translucent
content: mature containing hexacanth oncosphere
Definitive host of H.nana
man
Reservoir host of H.nana
rodents
Intermediate host of H.nana
man (occasionally some insects)
Diagnostic stage of H.nana
mature eggs + gravid segments
Infective stage of H.nana
mature egg
ttt of H.nana
1)Praziquental
2)Niclosamide: should be repeated after 2 weeks to kill the newly developed worms
Adult morphology of Ascaris Lumbricoides
pale pink/creamy in colour
15-40 cm in size
Describe egg of A.lumbricoides
Fertalized, unfertilized, decorticated (see page 35)
Definitive, intermediate, reservoir hosts of A.lumbricoides
DH: Man
RH: NONE
IH: NONE
Diagnostic stage of A.lumbricoides
immature eggs, larva and adult
infective stage of A.lumbricoides
mature eggs
Mode of infection of A.lumbricoides
ingestion of mature egg containing 2nd stage rhabditiform larva w/contaminated food or drink, through soiled fingers, especially in children
How many eggs does the female A.lumbricoides release after mating?
200,000egg/day/worm
Is A.lumbricoides a Geohelminthic parasite?
yes
Pathogenesis & clinical picture of A.lumbricoides
A)Migrating larva:
1)Ascaris pneumonitis “Loeffler syndrome”: break out of alveolar capillaries causing Hge & cellular infiltrates–> fever, urticaria, blood-tinged sputum, asthamtic wheezing
2)in liver or reaching systemic circulation–> granuloma formation –> visceral larva margins
B)Adult worms:
1)GIT disturbance
2)interferes with digestion (secretion of ANTIENZYMES as an adaptive or protective mechanism) –> promote ptn energy malnutrition & Vit. A deficiency AND symptoms of lactose intolerance
3)Hypersensitivity
4)Complications:
-intestinal obstruction, volovulus, intususseption
-fever , certain drugs or anaesthetic agents cause it to migrate to abdominal or extra-intestinal
–> perforation of bowel=peritonitis
–>appendicitis
–>gastric,duodenal trauma
–> blockage of ampulla of vater=pancreatic necrosis
–>Biliary ascariasis: colic,cholangitis,cholecystitis, obstructive jaundice, biliary stone formation
–>diverticulitis
–> invade liver parenchyma=liver abscess
–> esophagus
perforation
migrate upward and come out of the mouth & external nares
crawl into trachea –> respiratory obstruction
blood picture of A.lumbricoides
High eosinophilia in larval stage
little or none in adult worm ascariasis
What are the imaging techniques to find A.lumbricoides
1)Barium meal; appear as cylindrical filling defect as it appears radiopaque dur to barium ingestion
2)US
3)MRCP & ERCP
In mixed infections with ascaris what should be treated first and why?
Ascaris in order not to stimulate adults to migrate
Drug of choice to treat A.lumbricoides
1)Albendazole
2)Mebendazole
Infective stage of Ancylostoma Duodenale
(3rd stage)filariform larva
Mode of infection of A.duodenale
penetration of the skin
what larva has +ve hydrotropism, +ve thermotropism & -ve geotropism?
larva of A.duodenale
Is A.duodenale a geohelminthic parasite?
yes
What are the most unique symptoms of ancylostoma duodenale?
1)Blood loss of 0.3 cc of blood per day:
–> sucking blood
–>prolonged bleeding at the site of attachment as worm secretes anticoagulase substance
–>the worm leaves the bleeding-oozing site to another spot where it sucks more blood forming more minute ulcer
2)Hyprochromic microcytic anemia: due to chronic blood loss and depletion of iron stores
3)melena and occult blood in stool
4)Pica
Compare btw A.duodenale and N.americanus
see page 47
What is the other name of strongyloides stercoralis?
Dwarf threadworm
Diagnostic stage of S.stercoralis
Rhabditiform larva
Infective stage of S.stercoralis
filariform larva
mode of infection of S.stercoralis
skin penetration
What are the geohelminthic parasites that small intestine is their habitat?
1)Ascaris lumbricoides
2)ancylostoma duodenale
3)Strongyloides stercoralis
Does S.stercoralis exert autoinfection?
yes externally(penetrating peri-anal skin after exiting from the anus) and internally (rhabditifrom charnge to filariform due to its presence in the intestine for a long time such as constipation)
clinical picture of S.stercoralis
1)external autoinfection; cutaneous larva margins–> larva currens
2)loeffler syndrome
3)GIT disturbance
4)Weight loss
5)S.stercoralis may be present in ectopic sites as it may pass Lt side of the heart or in immunocomprimised patients (opportunistic infection)
ttt of S.stercoralis
Ivermectin (drug of choice)
thiabendazole
Infective stage of Trichostrongylus Colubriformis
Filariform larva
DH of T.colubriformis
Herbivorous animals and occasionally man
Diagnostic stage of T.colubriformis
Immature eggs in feaces
Mode of infection of T.colubriformis
Ingestion of filariform larva with vegetables and water
T/F: Filariform larva of T.colubriformis undergoes pulmonary migration for development
False
DH of Capillaria philippinensis
Man
RH of C.philippinensis
Fish eating birds
IH of C.philippinensis
small fresh water fish
Diagnostice stage of C.philippinensis
Egg, larva and adults in stool
Infective stage of C.philippinensis
infective larva in fish intestine
Mode of infection of C.philippinensis
eating raw or improperly cooked WHOLE INFECTED FISH and internal auto infection
Pathogenesis of C.philippinensis
invasion of intestinal mucosa leading to enteropathy with chronic inflammatory reactions and atrophy of the villi –> malabsorption of fats, ptn, electrolytes, and sugars
Parasitological findings of C.philippinensis
eggs
larva
adult
charcot-leyden
Host of Gardia Lamblia
Man especially children
Diagnostic stage of G.lamblia
Cyst and trophozoite
Infective stage of G.lamblia
cyst
What is the most common protozoa that causes waterborne outbreaks of diarrhoea? and why?
1)Gardia
due to use of inadequately treated surface water, raw sewage is mixed with water intended for drinking, recreational exposure to water in lakes and swimming pools
Mode of infection of Gardia lamblia
*Heteroinfection:
-Contaminated food & vegetables
-contaminated water
-person-to-person feaco-oral
-food handlers
-insects
*autoinfection: feaco-oral
What are the factors that increases risk of giardiasis?
1)Hypogammaglobulinemia
2)IgA deficiency
3)Impaired gastric acid secretion–>achlorhydria
4)blood group A
5)Malnutrition in children
Clinical picture of G.lamblia
1)Duodenitis
2)Epigastric pain
3)Malabsorption
4)Steatorrhea
5)cholangitis,cholecystitis
what stage of Gardia appear in what stool?
1)Trophozoites in diarrhoeic stool
2)Cyst in formed stool
shedding in stool is irregular (intermittent excretion) so multiple stool samples may be required
Are blood or PNL present in Gardia?
No as it is not an invasive pathogen
What are the examinations for duodenal content in gardia lamblia?
1)String test (Entero-test)
2)duodenal aspiration
ttt of G.lamblia
1)Tinidazole(single oral dose)
2)Metronidazole (flagyl)
3)Atebrine
