1. INTRODUCTION TO PARASITOLOGY
Definition of Terms:
Clinical Parasitology – deals with the parasites
of man and their medical significance
1.Parasitology - is the area of biology
concerned with the phenomena of
dependence of one living organism on
another.
2.Host – a larger organism which provides
physical protection and nourishment.
Ex. Mosquito, man
• Definitive host- parasite undergoes
sexual maturity
• Intermediate host – harbors the larval
stages of the parasite
• Paratenic/transport host - no
development occurs but parasite
remains alive and infective
• Reservoir host- allows the parasite’s
life cycle to continue; any animal that
harbors an infection that can be
transmitted to humans
3.Commensalism – only one partner benefits
from the association but the host is neither
helped nor harmed.
4.Mutualism – relationship is beneficial both to
the parasite and host
5.Vector – transmits parasites to
humans/animals
6.Zoonosis – parasites found in animals are
transmitted to humans
7.Obligate parasites – organisms that can’t
exist without a host
8.Free living stage- parasites live outside the
host in an external environment within a
protective eggshell or cyst
8.Facultative parasites–may live either a
parasitic or free-living existence
9.Infection – prodiced by endoparasites
10.Infestation – produced by ectoparasites
11.Parasitosis – state of infection or infestation
with an animal parasite) some parasites are
harmless commensals, others are pathogenic
12.Superinfection– if an individual harboring a
parasite is reinfected with the same species of
parasite
13.Autoinfection – the infected person is his
own direct source of reexposure via oral anal
route
14.Epidemiology – body of knowledge
concerning disease in human populations or
communities rather than an individual
15.Endemic – when disease in the human
population maintains a steady, moderate level
16.Hyperendemic – if the prevalence is high
17.Epidemic – a sharp rise in the incidence or
an outbreak of the disease
18.Sporadic – appears only occasionally in
one or a few members of the community
19.Pandemic – disease is disseminated over
extensive areas of the world ex. H1N1, cholera
20.Carrier – host harbors the parasite without
demonstrating symptoms
21.Polyparasitism – multiple infections of 2 or
more species of parasites occurring
simultaneously.
22. Helminths– multi-cellular parasites
Classification of Helminths:
a.) Nematodes (roundworms)
b.) Platyhelminths (flatworms)
*trematodes (flukeworms)
*cestodes (tapeworms)
c.)Acanthocephalans (thorny-headed worms)
23. Protozoa – unicellular parasites
Classification of Protozoa:
a.)Sarcodina – movement through
pseudopods b.)Mastigophora – the flagellates
c.)Ciliophora – the ciliates
d.)Sporozoa – organisms whose adult stage is
not motile.
2. TYPES OF HOST-PARASITE
RELATIONSHIP:
1. Commensalism – the host and the parasite
live in harmony with each other and neither
the host nor the parasite is harmed.
2. Mutualism – the host and the parasite both
benefit from a relationship with each other.
3. Parasitism – one partner benefits at the
expense of the other.
LOCOMOTOR ORGANELLES:
1. Pseudopodia – temporary extensions of the
cell/plasma membrane and used for
locomotion and feeding; movement is like
protoplasmic streaming
2. Flagella – slender whip-like structures
3. Cilia – tiny, hair-like structures composed of
kinetids(basic unit of cilia).
REPRODUCTION
A. Asexual Reproduction
1. Binary fission – 2 daughter cells
2. Multiple fission – the nucleus of the
parent divides into many daughter
nuclei by repeated divisions.
B. Sexual Reproduction
1. gametogony – meiosis; sexual
reproduction by union of 2 whole cells
daughter cells are called gametes
RISK FACTORS FOR GETTING
INTESTINAL PARASITES:
1. Living in or visiting an area known to have
parasites.
2. International travel to endemic areas
3. Poor sanitation (for both food and water)
4. Poor hygiene
5. Age -- children and the elderly are more
likely to get infected
6. Exposure to child and institutional care
centers .
7. Having a weakened immune system
8. HIV or AIDS
SOURCES OF EXPOSURE TO INFECTION
OR INFESTATION:
1. Contaminated soil or water
2. Food containing the infective stage
3. Blood-sucking insect
4. Domestic or wild animal harboring the
parasite
5.Another person
6.One’s self
PORTAL OF ENTRY INTO THE BODY:
1. Mouth (most common)
2. Skin (skin penetration)
3. Nose
4. Transplacental
5. Genitalia
6. Transmammary
DAMAGE PRODUCED BY PARASITOSIS:
1. Traumatic Damage – when the parasite
punctures the skin producing wounds; may
cause slight physical damage when parasite
enters the body or extensive trauma with
hemorrhage
2. Lytic necrosis – enzymes released by
parasites make it possible for them to digest
food available in the environment
3. Stimulation of Host-Tissue Reaction –
cellular proliferation and infiltration at the site
of the parasite
4. Toxic and Allergic Phenomena –
arthropods/vectors introduce toxins to the skin
5. Opening of Pathways for Secondary
Invaders – the entry of an animal parasite may
open pathways in the skin or the intestinal
tract for invasion by other pathogenic
microorganisms.
CLINICAL EVIDENCE OF PARASITISM
The physician obtains information concerning
the effect of parasitic diseases in the patient
based on clinical history and physical
examination. Majority of the symptoms are not
diagnostically specific.
The presenting symptoms may be acute or
chronic in nature. There may be initial toxic
3. manifestations, high fever, evidence of
inflammation, generalized or localized pain or
tenderness, gradual weight loss, and anemia.
Clinical effects of most parasitoses often
develop slowly and builds up gradually with a
few exceptions.
THE BLOOD PICTURE IN PARASITIC
INFECTIONS:
1.Anemia
2.Leukocytosis
3.Neutreopenia
DIAGNOSIS OF PARASITOSIS
1. Clinical history/ clinical picture
2. Laboratory diagnosis
SPECIMEN CONSIDERATION FOR STOOL:
1. Should be free of oil, magnesium, barium or
bismuth, without contamination of urine
2. Placed inside a sterile container
3. Should be fresh, esp. if stools are diarrheic
4. If delay in diagnosis is anticipated, stools
should be preserved.
TREATMENT OF PARASITOSES:
Phyisician should consider the ff:
1. severity, duration, and intensity of infection,
and the probability of reinfection
2. Efficacy, availability, toxicity, acceptability of
the treatment
METHOD OF TREATMENT:
1. Chemotherapy
2. Surgical Intervention – removing lesions in
the brain or eye, or other organs of the body
CONTROL OF PARASITIC DISEASES:
1.Timely detection of infection and provide
accurate diagnosis and evaluation of the
clinical importance of the disease in the patient
2. Adequate treatment of the patient
3.Search for other cases in the patients’ family
and provide treatment
4. Determine the source of infection and report
it to health officials
5. Patient education
6.Support and cooperate in community
preventive measures
7.Educate the patients in ways of utilizing and
strengthening local health departments
