parasite 3
DESCRIPTION
Parasite 3TRANSCRIPT
Adaptations can be classified as either progressive or
regressive, or biological.
•Progressive adaptations -
Parasite has developed certain of its parts to a higher level
of functionality.
•Regressive adaptations -
Involve the simplification or disappearance of certain organs
of the parasite.
•Biological adaptationsEnable the parasites to survive better, but cannot be
explained as simply atrophy or development of new organs
for the parasites.
MORPHOLOGICAL ADAPTATIONS OF PARASITES
NATURAL CIRCULATION OF PARASITES
In order to survive, ecto- and endoparasites have evolved to be able
to leave the host and to change hosts. The range o possible hosts
and the way parasites leave and enter their hosts determine the
travel paths of parasites in nature, as well as those of the diseases
they cause.
The typical natural sources of infectious disease-causing agents are
the people and animals already hosting the disease, or carriers of
parasites who spread them in the outside environment.
E. coli
pasiutligės
virusas
gripo sukėlėjas
Bacteriphages penetrate
into E. coli bacterium
• The process by which an organism is entered by disease-
causing agents is known as infection, and the resulting diseases
as infectious diseases.
Cold
snuffle
The process by which parasites (that is protozoa, helminths,
arthropods) enter the host is known as infection, and parasitic diseases
are also termed as infective diseases.
Balantidium coli
Echinococcus
granulosus
Cimex lectularius
Trichomonas vaginalis
Pediculus vestimenti
•An organism (human or animal) in which a
disease-causing parasite lives (viruses, bacteriae,
riketsiae, fungi, protozoa, helminths, arthropods),
develops or reproduces is termed as an infection
source.
Autoinvasion – when individual themselves can become the
sourse for self infection.
Reinvazija – when individual catches repeated infection after
recovery.
It somethimes occurs that a parasitic disease moves from a
symptomatic to an asymptomatic form. A disease without clinical
symptoms is known as a latent disease, and the period it lasts as the
latent period.
If the symptoms of disease, after recovery, take a turn for the
worse, such a situation is termed a relapse of the disease.
An organism in which parasites can accumulate and survive for extended
periods of time is known as a reservoir host.
A natural reservoir is a habitat suitable for sustaining parasite life in the
natural environment.
There are several types of natural reservoir:
• Soil reservoir
• Aquatic reservoir
• Above-ground (terraneous) reservoir
• Technogenic reservoir
Technogenic reservoir
Blatta orientalis
Blatella germanica
Mechanical vectors simply transport
disease-causing agents from host to host.
No development of the parasites occurs in
these vectors.
Vectors are critical to the natural circulation of many
parasites. Most vectors are bloodsucking arthropods
(insects and arachnids). Vectors may be classified into:
•mechanical vectors
•specific vectors.
Musca domestica
Specific vectors are intermediate hosts as well: the
parasites develop in them and are typically passed on at
the end of that development. Consequently, there is
normally a very limited number of spieces (perhaps only a
single spieces) that may serve as specific vectors for any
given parasite
Glossina morsitans Anopheles freeborni
THE CLASSIFICATION OF INFECTIOUS DISEASES
Infectious diseases may be classified by their causing
agents:
1. Viral diseases - caused by viruses
2. Bacterial diseases - caused by bacteria
3. Fungal diseases - caused by fungi
4. Parasitic diseases - caused by parasitic protozoa,
helminths, arachnids and insects.
5. Transmissional diseases are those infectious diseases
which are transferred host-to-host by some transmitting
organism (the vector).
There are two types of transmissional diseases:
obligate transmissional and facultative
transmissional.
•Obligate transmissional are those diseases that
can only be transmitted through a vector,
•Facultative transmissive are those diseases which
may be transmitted with or without a vector, i.e. the
vector is not absolutely necessary.
Infectious diseases may also be classified according to
organism they infect.
1. Anthroponoses are human-only diseases, such as
amoebiasis or trichomoniasis.
2. Anthropozoonoses are diseases of both humans
and animals, such as tick-borne encephalitis,
leishmaniasis, toxoplasmosis.
3. Zoonoses are diseases passed from animal to
animal. Humans can serve as mechanical vectors for
these, as in the examples of cattle lung plague or bird
malaria, or horse breeding disease