MEKANISME INFEKSI
PARASITE
DEWI M. DARLAN
PARASITOLOGY DEPARTMENT
• Gastrointestinal route
• Introduced percutaneously• Introduced percutaneously
• Others
e.g.
• Nematodes: A. lumbricoides, T. trichiura, E. vermicularis
e.g.e.g.
• Cestodes: T. saginata, T. solium
• Intestinal protozoans: E. histolytica, G. lamblia, B. coli
• Toxoplasma gondii thru cat’s infected feces
: e.g.
• Trematodes: Fasciolidae, C. sinensis, O. viverrini
• Hookworms • Hookworms
(Ancylostomatidae) thru
filariform larvae
• Strongyloides stercoralis thru
filariform larva
• Schistosoma sp. thru cercaria
• Enterobius vermicularis
• Toxoplasma gondii
• Plasmodium sp.
• Trichomonas vaginalis
Transmission of the parasites
� Parasite can be transmitted thru vector or
intermediate host
� An intermediate host is one that is required for
parasite development but one in which the parasite development but one in which the
parasite does not reach sexual maturity,
though it remains alive and infective to
another host
� A vector is a host that transmits parasite to
human in active way
Transmission of the parasites
� Classification of vector:
• Mechanical vectors: the pathogens are
carried thru the surface appendages of body,
e.g.: legs, wings, scales, furls, etce.g.: legs, wings, scales, furls, etc
• Biological vectors: the pathogens undergo
developments and/ multiplication within the
vector
Transmission of the parasites
� Cockroaches
� Houseflies
�Propagative:• No developmental changes of pathogens
• Multiplication of pathogens
• E.g.: dengue virus in Aedes mosquitoes
�Cyclo-propagative:�Cyclo-propagative:• Pathogens undergo development & multiplication
• E.g.: malaria parasites in Anopheles mosquitoes
�Cyclo-developmental:oPathogens undergo developmental changes without multiplicatioN
oE.g.: filaria worm in mosquitoes
� Transovarian:• Pathogens transmitted to off-springs of the vector
• E.g.: scrub typhus, dengue virus in mosquitoes
� Exposure may not necessarily lead to disease state
� Parasite that is exposed to human may be
established. Though the person doesn’t develop
signs and symptoms, he is still infected, but in carrier
statestate
� Parasite exposed established infection
develop pathological changes, with or without signs
and symptoms disease state
� Parasite that is exposed may also be destroyed (not
established). Thus the person is not infected, and
will not develop disease
SOIL TRANSMITTED HELMINTHS
� STH is helminths (nematodes) that are
exposed to human thru their infective forms
in soil
� These nematodes include:
• A. lumbricoides• A. lumbricoides
• Ancylostomatidae (hookworms)
• T. trichiura
• S. stercoralis
• Toxocara sp. (zoonotic)
� Transmissions of A. lumbricoides, T.trichiura,
and Toxocara sp. are acquired by ingestion of
infective (embryonated) eggs from
contaminated soilcontaminated soil
� Ancylostomatidae and S. stercoralis require
skin penetration by filariform larvae
� Infection occurs when embryonated eggs of A. lumbricoides are swallowed with contaminated food and water
� Hatch in duodenum (L1) penetrate mucosa and submucosa enter lymphatics or venulessubmucosa enter lymphatics or venules
� Passing thru the right heart pulmonary circulation molt twice (10 days) become L3
� Move up the respiratory tree molt to L4 swallowed
� L4 juveniles are resistant to the acidity of gastric juice pass thru to intestine adults
� If Toxocara sp. gain entry to improper host
do not complete the migration
developmental arrest random wanderingdevelopmental arrest random wandering
thru various body organs and tissues
� T. trichiura after swallowed, infective juveniles
hatch and enter the large intestine mucosa.
After penetration, worms begin to grow and
the tunnel back toward the lumenthe tunnel back toward the lumen
� As the worm approach maturity, the
enlarging posterior portions breaks out the
epithelium and protrudes into the intestinal
lumen.
TAENIA SP.
� Gravid segment detach and either pass out with feces or migrate out of the anus
� As the segment begins to dry up, it becomes rupture allowing eggs to escaperupture allowing eggs to escape
� When eaten by suitable host, eggs hatch in the duodenum
� Hexacanths penetrate the mucosa intestinal venule carried out throughout the body enter muscle fiber cysticerci(2 months)
� When the infected beef meat eaten by a
person, the invaginated scolex of cysticerci
evaginate in response to bile salt
� The bladder is digested by the host, and � The bladder is digested by the host, and
budding of proglottid begins, and shedding
gravid proglottid within 2-12 weeks
� When the infected pork meat eaten by a
person, the invaginated scolex of cysticerci
evaginate in response to bile salt
� The bladder is digested by the host, and � The bladder is digested by the host, and
budding of proglottid begins, and shedding
gravid proglottid within 2-12 weeks
� Since human serve as intermediate host as
well, infection with eggs results in
development of cysticerci in man’s tissue