Conference 5 Parasitology Introduction-1.ppt

General Parasitology
Zoology
Dr. Miguel Alcántara Vila
2023

Introduction to Parasitology
• Each animal is a host of many parasites;
thus, there are far more parasitic
organisms on Earth than non-parasitic
organisms.
• It has been estimated that more than 50%
of all living plants and animals are
parasitic at some stage during their life
cycle.

Introduction to Parasitology
In this topic we will concentrate on 3 major groups
of parasites:
1. Protozoa - flagellates, amebas, malarial
organisms.
2. Helminths - parasitic worms such as the
flukes, tapeworms and roundworms.
3. Arthropods - insects and arachnids that are
ectoparasites and carriers (vectors) of diseases.

Why do we study parasites?
• Parasites provide unique examples
of biological phenomena not found
in free-living organisms.
ADAPTABILITY

1. Medical Importance
Homeostasis
Diseases

2. Veterinary Importance
Farming
organisms Infectability

• Parasites provide unique examples of
biological phenomena not found in free-
living organisms.
2. Veterinary Importance
3. Economic Importance

Medical Importance of Parasites
• Humans are hosts to many species of
parasites.

Medical Importance of Parasites
• Humans are hosts to many species of parasites.
• Many of these parasites are causative agents of
major public health problems of the world.

Ascaris 1.3 billion
Hookworms 1.3 billion
Whipworms 1 billion
Filarial worms 657 million
Malaria 500 million
Schistosomes 270 million
Amebiasis 50 million
Taenia tapeworms 50 million
Clonorchis 20 million
Chaga’s Disease 15 million
These parasites cause untold suffering and death in
the world today.
Recent estimates of the number of people
infected with parasites in the world are:

Examples of Medical Importance
in the World

in the World
• The life expectancy of an Egyptian is in the mid-
60's due to Schistosomes.
-. Schistosoma eggs are released with feces or urine, depending on
species, the eggs hatch and release Miracidia, which swim and
penetrate specific snail intermediate hosts. This stages include two
generations of sporocysts and the production of Cercariae. the
infective Cercariae can swim, penetrate the skin of the human host
becoming Schistosomulae. The schistosomulae migrate via venous
circulation to lungs, then to the heart and develop in the liver, exiting
the liver via the Portal vein system when mature. Male and female
adult worms copulate and reside in the Mesenteric venules, the
location varies between species

in the World
• The life expectancy of an Egyptian is in the
mid-60's due to Schistosomes.
• 15 million children in the world will die this
year from a combination of malnutrition and
parasites.

in the World
parasites.
• Over 1 million African children will die this
year from the effects of malaria.

Examples of Medical Importance in
the World
parasites.
• Over 1 million African children will die this
year from the effects of malaria.
• Many cases of plague, transmitted by fleas, still
occur throughout the world.

Examples of Medical Importance in U.S
and developed countries.
• The comfort of the U.S and the European
countries are not immune from parasites.
• Chagas disease, cyclosporiasis, cysticercosis,
toxocariasis, toxoplasmosis, schistosomiasis
and trichomoniasis are especially common in
tropical areas where people do not have access
to clean water or safe ways to dispose of
human waste.

1. Buruli Ulcer
2. Chagas Disease
3. Cysticercosis
4. Dengue Fever
5. Dracunculiasis (Guinea
Worm Disease)
6. Echinococcosis
7. Fascioliasis
8. Human African
Trypanosomiasis (African
Sleeping Sickness)
9. Leishmaniasis
10. Leprosy (Hansen’s
Disease)
11. Lymphatic Filariasis
12. Mycetoma
13. Onchocerciasis
14. Rabies
15. Schistosomiasis
16. Soil-transmitted
Helminths (STH)
(Ascaris, Hookworm, and
Whipworm)
17. Trachoma
See below for more information on selected
neglected tropical diseases:

Some common parasitic diseases in the
U.S. include:
Pinworms Giardia Dog roundworms Ticks

Import of Parasites from Tropics to
other countries
• Movement of persons from all areas of the
world have introduced parasitic diseases into
the U.S and Europe, and vice versa. Also
another diseases were exported from Asiatic
countries to the rest of the world, specially to
African continent.
– Numerous cases of malaria, cholera and Chaga’s
are brought back by vacationers from the tropics.

other countries
the U.S and Europe, but also another diseases
were exported from asiatic countries.
– Numerous cases of malaria cholera and Chaga’s are
brought back by vacationers from the tropics.
– Service personnel and health workers are often
employed in endemic areas with many parasites.

other countries
the U.S and Europe, but also another diseases
were exported from asiatic countries.
– Numerous cases of malaria are brought back by vacationers
from the tropics.
– Service personnel and health workers are often employed in
endemic areas with many parasites.
– Many immigrants have brought their parasites
with them.

Veterinary Importance of Parasites
We only see the tip of the
ICEBERG

• In Africa, cattle cannot be raised properly due
to Trypanosomes (sleeping sickness).

to Trypanosomes (sleeping sickness).
• A poultry farmer can be wiped out by
Coccidia.

Coccidiosis is caused by protozoa of the phylum Apicomplexa,
family Eimeriidae. In poultry, most species belong to the
genus Eimeria and infect various sites in the intestine. The
infectious process is faster (4–7 days) and is characterized by
parasite replication in host cells with extensive damage to the
intestinal mucosa. Poultry coccidia are generally host-specific,
and the different species parasitize specific parts of the
intestine. However, in game birds, including quail, the coccidia
may parasitize the entire intestinal tract. Coccidia are distributed
worldwide in poultry, game birds reared in captivity, and wild
birds.
A diagnosis of clinical coccidiosis is warranted if oocysts,
merozoites, or schizonts are seen microscopically and if
lesions are severe. Subclinical coccidial infections may be not
important, and poor performance may be caused by other flock
disorders.

Eimeria acervulina eggs
Eimeria acervulina lesions in chickens
Intestinal hemorraghe in chickens

to Trypanosomes.
Coccidia.
• Cattle, pigs and sheep infected with parasites
fail to gain weight and may not reproduce and
cause economic damage.

to Trypanosomes.
Coccidia.
• Cattle, pigs, and sheep infected with parasites
• Dogs may become infected with heartworm
and die if untreated.

to Trypanosomes.
Coccidia.
• Cattle, pigs, and sheep infected with parasites
• Dogs may become infected with heartworm
and die if untreated.
• Cats are infected by many species of
Protozoan's and Helminths.

Heartworm (HW) disease can affect dogs and cats indistinctly

Conference 5 Parasitology Introduction-1.ppt

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