MC 1 LECTURE
 Classify different types of parasites and hosts.
 Give examples of adaptations for parasitic existence.
 Parasites are organisms that lives on or inside the body
of the host from which they derive food or shelter.
They can be microscopic or macroscopic.
 They exhibit morphological, physiological, and
behavioral adaptations that enable them to
successfully thrive, perpetuate, and spread.
 Attachment organ – prevent parasites from being
dislodged from organs they inhabit.
 Proteolytic enzymes – released from glands that enable
organisms to penetrate tissues and organs.
 They reproduce at a faster rate than their host and can
use asexual reproduction to increase their numbers in
the intermediate host.
 Ectoparasite
 Live on the surface of their hosts
 Endoparasite
 Access to hosts by:
 Consumption of contaminated food
 Penetration of the skin by infective stage during contact with
contaminated soil and water
 Inoculation by an infected hematophagous vector
 Obligate parasite
 Cannot exist outside of their host
 Facultative parasite
 Living free but can transfer into parasites when
accidentally ingested or enter the host through wound
or openings of the body.
 Naegleria fowleri and Acanthamoeba spp. - can cause
serious or fatal disease in humans
 Permanent parasite
 Spend their entire life span within their hosts.
 Temporary/intermittent parasites
 Associate into their host only when feeding and then
leave them after - Bedbugs
 Accidental/Incidental parasites
 Enter or attach to the body of host that are different
from their preferred hosts.
 Toxocara – causes serious visceral migrans.
Host are organisms where parasites live, feed, and obtain
shelter from and is therefore disadvantaged in the
association
 Intermediate host
 Caters the juvenile stages or asexual stages of the parasite
 Definitive host
 Caters the adult stages that releases eggs.
 Paratenic host
 Bridge the gap between the intermediate and definitive hosts.
 For parasites to survive and thrive, they need to cross over the
definitive host from the intermediate host.
 Vectors
 They are intermediate hosts that introduce the infective
stages of the parasite to the definitive host through their
bites for their blood meal.
 Mosquitoes – malaria and filariasis
 Sandflies – Leishmaniasis
 Tsetse flies – African trypanosomiasis
 Triatomid bug – American trypanosomiasis
 Benign effects that foil to show symptoms of infection
to more serious and extreme outcomes that affects
hosts survival.
 Infection – presence of parasite without accompanying
symptoms. This aggravates into disease when the host
manifest signs and symptoms associated with
parasitism.
 Immune evasion – such as coating with host
substances and antigenic variation (mechanism by
which parasite successfully escape the effects of the
host response)
 Immune-mediated pathologies
 A result from hyperactivity of the immune system
 Predisposition to cancer (cholangiocarcinoma – CCA)
 Group I carcinogens by the International Agency for
Research on Cancer (IARC)
 Clonorchis sinensis
 Opisthorchis viverrini
 Schistosoma haematobium
 Feces
 Sputum
 Blood
 Tissue biopsies
 Microscopy (gold standard)
 Serologic technique (antigen & antibodies)
 Serum
 Saliva
 Feces
 Molecular means by DNA detection
 Feces
 Blood
 Respiratory tract
 Specimen: sputum & aspirates
 Detect: Pneumocystis carinii, Cryptosporodium parvum,
Echonococcus spp., and Microsporodia
 Gastrointestinal tract
 Specimen: feces & aspirates (duodenal contents), fresh
stool
 Parasites: protozoans, nematodes, and trematodes
 Developmental stages: cyst, trophozoites, oocysts,
spores, adult, larvae, and eggs
 Genitourinary tract
 Specimen: urine & genital discharges
 Parasites: trepanosoma vaginalis, Schistosoma
haematobium, and Microsporidia
 Central nervous system
 Specimen: CSF
 Parasites: Taenia solium cystecerci, Echinococcus spp.
hydatid, Naegleria fowleri, Acanthamoeba spp.,
Toxoplasma gondii, Microsporidia, and Trypanosoma
spp.
 Tissue biopsy
 Histologic preparations and impression smears
 Skin, muscle, cornea, intestine, liver, lung, and brain
 Blood
 Collected through venipuncture and finger puncture
and processed either through thin film, thick film, and
blood concentrations.