2. Inroduction To Parasitology
Study of those parasites which cause or produce disease.
Parasitology is further divided into two parts.
parasitic protozoa
unicellular
parasitic helminths (worms)
multicellular
3. History
Parasites first evolved long before humans evolved, and early
writings from Egypt mention ones such as roundworms and
tapeworms.
In the 17th century, scientists such as Francesco Redi and
Antonie van Leeuwenhoek began to study them in greater
detail and created an early version of parasitology.
4. History of parasitology
In 1681, Antonie van Leeuwenhoek first discovered the
giardia in feces (stool) by using single lens microscope
Giardia is a tiny parasite (germ) that causes the diarrheal
disease giardiasis. Giardia is found on surfaces or in soil,
food, or water that has been contaminated with feces (stool)
from infected people or animals. You can get giardiasis if you
swallow Giardia germs.
5. Parasites
Parasites are organisms that live in or on a living host of
another species. They survive by taking nutrients from this
host.
There are three main classes of parasites that can cause
disease in humans: protozoa, helminths, and ectoparasites.
6. Protozoa
Protozoa are microscopic, one-celled organisms.
hey are able to multiply in humans, which contributes to their survival and also
permits serious infections to develop from just a single organism.
Transmission of protozoa that live in a human’s intestine to another human
typically occurs through a fecal-oral route
(for example, contaminated food or water or person-to-person contact).
Protozoa that live in the blood or tissue of humans are transmitted to other
humans by an arthropod vector
(for example, through the bite of a mosquito or sand fly).
7. Helminths
Helminths are large, multicellular organisms that are generally
visible to the naked eye in their adult stages.
Like protozoa, helminths can be either free-living or parasitic
in nature.
In their adult form, helminths cannot multiply in humans.
8. Parasitic Infections
Parasitic infections cause a tremendous burden of disease in both
the tropics and subtropics as well as in more temperate climates. Of
all parasitic diseases, malaria causes the most deaths globally.
Malaria kills more than 400,000 people each year, most of them
young children in sub-Saharan Africa.
The Neglected Tropical Diseases (NTDs), which have suffered from a
lack of attention by the public health community, include parasitic
diseases such as lymphatic filariasis, onchocerciasis, and Guinea
worm disease.
9. Parasitic Infections
The NTDs affect more than 1 billion people worldwide, largely
in rural areas of low-income countries. These diseases extract
a large toll on endemic populations, including lost ability to
attend school or work, stunting of growth in children,
impairment of cognitive skills and development in young
children, and the serious economic burden placed on entire
countries.
However, parasitic infections also affect persons living in
developed countries, including the United States.
10. Transmission of Parasitic Diseases
Animals (Zoonotic)
Pets can carry parasites and pass parasites to people. Proper handwashing can
greatly reduce risk.
Foods can be the source for some zoonotic infection when animals such as cows
and pigs are infected with parasites such as Cryptosporidium.
People can acquire cryptosporidiosis if they accidentally swallow food or water that
is contaminated by stool from infected animals. For example, this can happen when
orchards or water sources are near cow pastures and people consume the fruit
without proper washing or drink untreated water.
11. How do I know if I have parasites?
Signs and Symptoms
Abdominal pain.
Diarrhea.
Nausea or vomiting.
Gas or bloating.
Dysentery (loose stools containing blood and mucus)
Rash or itching around the rectum or vulva.
Stomach pain or tenderness.
Feeling tired.
