Parasites of medical importance

(ASSIGNMENT# 01 SPRING-2025)

SUBMISSION DATE (April 21st 2025)

BY

ISHTAR LIAQAT

ROLL # 23017114-045

Zoo-430 (Principals of parasitology)

BS Zoology 5th Induction IV (Section A)

Mam Shamaila Irum

Department of Zoology

UNIVERSITY OF GUJRAT

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 TABLE OF CONTENTS
CONTENTS PAGE

LIST OF FIGURES……………………………………………… ii

1.Introduction...................................................................... …………04

2. Plasmodium Soo.…………………..................................................04

3. Entamoeba histolytica ……………………………...……………05

4. Giardia lamblia ………………………………………………...…07
5. Ascaris lumbricoides……..,………………………………………………09
6.Taenia solium……………………………………………….………11
7.References……………………………………………………….. ..15

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 LIST OF FIGURES PAGES

1. Life cycle of Plasmodium………………….……………………………………..05

2. Life cycle of Entamoeba histolytica……………………..………………………..07

3. Life cycle of Giardia lamblia………………………………………..…………….09

4. Life cycle of Ascaris lumbricoides……….,………………………………………11

5.Life cycle of Taenium solium……………………………………………………....13

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1- Introduction

Parasites are living organisms that depend on a host for survival, often harming the host in the
process. Many of these parasites have serious medical significance, contributing to a large
number of infections and diseases worldwide, particularly in regions with poor hygiene and
inadequate healthcare systems (CDC, 2023). They are classified into groups such as protozoa,
helminths, and ectoparasites, each capable of affecting different parts of the human body.
Understanding these parasites is essential for identifying their transmission methods, life
cycles, symptoms, and prevention strategies. This assignment focuses on five major parasites
that are of particular concern in the field of medical parasitology.

2- Plasmodium spp.

Disease: Malaria

Malaria is a severe, often fatal disease caused by protozoan parasites of the genus
Plasmodium(World Health Organization [WHO], 2023). The primary species responsible for
human malaria include Plasmodium falciparum P. vivax P. malariae and P. ovale Of these, P.
falciparum is the most dangerous, leading to severe complications such as cerebral malaria
and organ failure, which can be fatal if untreated (Centers for Disease Control and Prevention
[CDC], 2022).

Transmission:

Bite of infected Anopheles mosquito

Malaria is transmitted when an infected female Anopheles mosquito bites a human and injects
sporozoites the parasite’s infective stage, into the bloodstream (CDC, 2022). These
sporozoites travel to the liver, where they mature and multiply. The infection cannot spread
directly from person to person; the mosquito serves as the vector for transmission (WHO,
2023).

Symptoms:

Fever, chills, sweating, headache

The typical symptoms of malaria appear 10 to 15 days after infection and include fever,
chills, sweating, and headache, often occurring in cyclical patterns (CDC, 2022). These
symptoms result from the synchronized rupture of red blood cells as the parasite matures

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 inside them. Additional symptoms may include muscle pain, nausea, and fatigue. Severe
cases of P. falciparum infection can lead to complications such as anemia, kidney failure, and
even death (WHO, 2023

Life Cycle:

Involves mosquito (vector) and human (host); liver and blood stages

Fig 1:Plasmodium

(CDC, 2022)

The life cycle of Plasmodium is complex, requiring both human and mosquito
hosts. The cycle begins when an infected mosquito injects sporozoite into the
human bloodstream. These sporozoites travel to the liver, where they mature
into merozoites.Monzonites are released into the bloodstream, invading red
blood cells, where they reproduce. Some parasites develop into gametocytes
which are ingested by mosquitoes when they feed on an infected person (WHO,
2023). In the mosquito, sexual reproduction occurs, resulting in new sporozoites
that can be transmitted to another human (CDC, 2022)

Prevention:

Mosquito nets, repellents, antimalarial drugs

Preventing malaria involves reducing mosquito exposure and controlling mosquito populations.
Using insecticide-treated bed nets (ITNs) and applying mosquito repellents are effective methods to
prevent bites, especially at night (WHO, 2023). Environmental control measures, such as draining

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stagnant water, help limit mosquito breeding sites. Additionally, antimalarial medications like
chloroquine, doxycycline, and artemisinin-based combination therapies (ACTs) are used for both
prevention and treatment, particularly for travelers and those in endemic regions (CDC, 2022)

2- Entamoeba histolytic

Disease:

Amoebiasis (Amoebic Dysentery) Entamoeba histolytica is a protozoan

parasite responsible for amoebiasis, also known as amoebic dysentery.
This infection primarily targets the intestines, causing symptoms such as
bloody diarrhea, stomach cramps, and abdominal pain. It is a major cause
of gastrointestinal diseases in tropical and subtropical areas, particularly
in regions with poor sanitation. If not treated effectively, the parasite can
spread beyond the intestines, resulting in severe complications like
liver abscesses (Cunningham & Ajayi, 2021).
Transmission:
Via Contaminated Food/Water The infection is transmitted through the
ingestion of cysts, the infective form of Entamoeba histolytica. These
cysts are often found in contaminated food and water, which is common in
regions with substandard sanitation and hygiene (WHO, 2022). After being
ingested, the cysts pass through the stomach into the intestines, where
they release trophozoites, the active form of the parasite. The
trophozoites can then invade the intestinal lining, causing damage. In
addition to contaminated food and water, the parasite can spread through
contact with fecal matter, emphasizing the importance of proper hygiene,
particularly handwashing (CDC, 2022).
Affects the Intestines and Sometimes the Liver
In the intestines, Entamoeba histolytica attaches to the intestinal lining
and causes significant tissue destruction. This leads to bloody diarrhea,
abdominal cramps, and other gastrointestinal issues. In severe cases, the
infection may lead to colitis, which is inflammation of the colon, or even
perforation of the intestinal wall. Although the intestines are the primary
site of infection, the parasite can spread to other organs, with the liver

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being the most commonly affected. Liver abscesses, which are painful
collections of pus in the liver, can form and may require surgical drainage
(Gupta et al., 2020
Prevention:
Safe Drinking Water, Good Hygiene Practices Preventing amoebiasis relies
on controlling the spread of cysts through contaminated food and water.
Key preventive measures include ensuring access to safe drinking water,
improving overall sanitation, and promoting hand hygiene, especially after
using the bathroom and before handling food. Food preparation should be
done carefully to avoid contamination, particularly in areas with poor
water quality. In regions where Entamoeba histolytica is endemic,
travelers are often advised to avoid consuming raw or undercooked food
and may also be prescribed preventive medications (CDC, 2022).
Fig 2:Entamoeba Hisolytica

(Cunningham & Ajayi, 2021)

3- Giardia lamblia
Disease: Giardiasis
Giardia lamblia is a protozoan parasite that causes giardiasis, a
gastrointestinal infection. Giardiasis is one of the leading waterborne
diseases globally, often referred to as beaver fever due to the parasite’s
presence in wild animal reservoirs like beavers. Infected individuals can

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experience a range of gastrointestinal issues, from mild discomfort to
more severe symptoms. Common signs of giardiasis include diarrhea
abdominal cramps bloating nausea, and occasionally vomiting. Other
symptoms may include fatigue, weight loss, and malabsorption, where the
body struggles to absorb nutrients from food (CDC, 2022).

Transmission:
Spread through Contaminated Water
The primary route of transmission for Giardia lamblia is via the ingestion
of cysts which are the infectious stage of the parasite. These cysts are
commonly found in contaminated water sources, particularly in areas with
poor water treatment and sanitation. The parasite can be present in
surface water (rivers, lakes, and streams) or well water as well as on
contaminated food, surfaces, or through direct contact with infected
individuals (WHO, 2022). Once the cysts are ingested, they pass through
the digestive system, where they release trophozoite the active form of
the parasite. These trophozoites then attach to the lining of the intestines,
causing inflammation and the typical symptoms of giardiasis.
Symptoms:
Leads to Diarrhea and Abdominal Cramps
The onset of giardiasis symptoms typically occurs 1 to 3 weeks after
infection. Common symptoms include watery diarrhea abdominal cramps
bloating and nausea. These symptoms are caused by the parasite
disrupting normal digestion and nutrient absorption in the small intestine.
Additional symptoms may include fatigue, weight loss, and a general
feeling of illness. In some cases, the infection can become chronic and
lead to long-lasting digestive issues such as irritable bowel syndrome (IBS)
and malabsorption making prompt treatment essential (CDC, 2022).
Life Cycle:
Involves Cysts and Trophozoites
The life cycle of Giardia lamblia consists of two stages: the cyst and the
trophozoite

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1. The cyst is the dormant, infectious stage of the parasite, capable of
surviving outside the host, especially in water. When a person consumes
contaminated water or food, they ingest these cysts.
2. Inside the intestines, the cysts transform into trophozoites, the active,
disease-causing form. These trophozoites attach to the intestinal wall and
multiply, leading to the symptoms associated with giardiasis.
3. Some trophozoites convert back into cysts, which are excreted in the
stool, continuing the transmission cycle to new hosts (CDC, 2022)
Fig 3: Giardia lamblia

(WHO, 2022)
Prevention:
Clean Water, Proper Hygiene
Preventing giardiasis involves avoiding exposure to contaminated water
and practicing proper hygiene. The most effective preventive strategy is
ensuring access to clean, treated water and avoiding drinking from
untreated sources such as lakes and streams. In endemic areas, boiling or
filtering water can effectively eliminate the cysts. Additionally,
maintaining good hygien including handwashin after using the restroom
and before eating, is crucial in preventing the spread of the parasite.
Avoiding raw or unwashed fruits and vegetables, as well as ensuring
proper sanitation, can further reduce the risk of infection. Travelers to
areas with endemic giardiasis should also conside medications(WHO,
2022).

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4-Ascaris lumbricoides
Disease: Ascariasis
Ascaris lumbricoides is a large roundworm that causes ascariasis one of the most prevalent
soil-transmitted helminth infections worldwide. This parasite primarily affects the intestines,
though its larvae can migrate to other organs, including the lungs. The severity of the
infection varies based on the worm burden. Mild cases may have minimal symptoms, but
more severe infections can lead to significant gastrointestinal discomfort, malnutrition, and
even other complications (CDC, 2023).
Transmission:
Ingestion of Eggs from Contaminated Soil or Food
The infection is primarily transmitted through the ingestion of eggs which are the infective
form of the parasite. These eggs are commonly found in contaminated soil or food, especially
in regions with poor sanitation. Eggs can contaminate vegetables, fruits, and water supplies,
and they remain viable for long periods in the environment. This persistence in the soil poses
a constant risk, particularly in areas with open defecation or inadequate waste disposal
systems (WHO, 2022).
Symptoms:
Abdominal Pain, Malnutrition, Cough (in Lung Phase)
Ascariasis manifests in two distinct phases: the intestinal phase and the lung phase During the
intestinal phase, when the eggs hatch in the intestines, the larvae mature into adult worms,
causing symptoms such as abdominal pain nausea, vomiting, and malnutrition Infected
individuals may also experience bloating and diarrhea due to intestinal obstruction or
irritation from the large number of worms. In the lung phase, the larvae migrate to the lungs,
where they can cause symptoms such as a cough wheezing and difficulty breathingThis
migration is part of the normal life cycle of the parasite, which involves traveling through the
respiratory tract before being swallowed back into the gut to complete their development into
adult worms (CDC, 2023).
Life Cycle:
Eggs Hatch in Intestines, Larvae Migrate to Lungs, Then Return to Gut
The life cycle of Ascaris lumbricoides involves several stages. Once eggs are ingested
through contaminated food or water, they reach the small intestine, where they hatch into
larvae. These larvae penetrate the intestinal wall and enter the bloodstream, where they travel
to the lungs. After maturing in the lungs, they ascend the respiratory tract to the throat and are

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swallowed back into the intestines. There, they grow into adult worms, which can measure up
to 30 cm in leng
the These adult worms produce eggs that are excreted in the feces, completing the cycle. The
eggs then contaminate the environment, continuing the cycle by infecting new hosts (CDC,
2023).

Fig 3: Ascaris lumbricoides

(CDC, 2023)
Prevention:
Handwashing, Avoid Open Defecation
Preventing ascariasis primarily involves improving sanitation and hygiene. Key prevention
methods include handwashing with soap and water, especially before eating or preparing
food and after using the restroom, to prevent the ingestion of infective eggs. Avoiding open
defecation and ensuring proper sanitation help prevent the contamination of food and soil
with Ascaris eggs. In areas with high prevalence, using sanitary latrines is essential for
controlling the parasite's spread. Additionally, washing and cooking vegetables and fruits
thoroughly, especially those grown in areas with poor sanitation, can reduce the risk of
infection. In endemic regions, mass drug administration programs using anti-helminthic
drugs such as albendazole or mebendazole are implemented to reduce the burden of ascariasis
(WHO, 2022).
5-Taenia solium
Disease:
Taeniasis and Cysticercosis

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Taenia solium commonly known as the pork tapeworm, causes two primary diseases in
humans: taeniasis and cysticercosis
Taeniasis happens when humans consume undercooked or contaminated pork containing
larvae of the tapeworm (cysticercus), which then develop into adult tapeworms in the
intestines. These tapeworms can grow to lengths of up to 7 meters and live in the small
intestine, where they produce eggs that are later passed in the feces.
Cysticercosi occurs when a person ingests Taenia solium eggs, usually via contaminated food
or water. Once ingested, the eggs hatch, and the larvae spread to various organs like muscles
and the brain, leading to serious complications. Specifically, neurocysticercosis, which affects
the brain, can result in seizures, headaches, and significant neurological damage (CDC,
2023).
Transmission:
Humans Get Infected by Eating Undercooked Pork or Through Fecal Contamination
Transmission of Taenia solium occurs via two primary methods:
1. Ingestion of Undercooked Pork People can contract taeniasis by consuming undercooked
or raw pork containing cysts of the tapeworm. These cysts develop into adult tapeworms
within the human intestines, where they begin to reproduce.
2.Fecal-Oral Transmission of Eggs Infected individuals pass Taenia solium eggs in their
feces, which can contaminate food, water, or surfaces. When another person ingests these
eggs, the larvae hatch and migrate throughout the body. Instead of becoming an adult
tapeworm, they form cysts in various tissues, including muscles and organs, potentially
leading to cysticercosis (WHO, 2022). This mode of transmission is especially concerning in
areas with poor sanitation.
Symptoms:
Abdominal Pain, Weight Loss, Seizures (in Neurocysticercosis)
The symptoms of Taenia solium infections depend on the type of infection:
Taeniasis: Individuals infected with adult tapeworms may experience mild symptoms such as
abdominal pain nausea, loss of appetite, and weight loss. Some may even notice segments of
the tapeworm in their stool. However, many individuals remain asymptomatic, particularly
with a mild infection.
Cysticercosis:
The symptoms of cysticercosis depend on where cysts form. When cysts form in the brain
(neurocysticercosis), they can cause seizures, headaches confusion and other neurological

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symptoms. If cysts form in muscles or under the skin, they may result in muscle pain or
visible lumps. In severe cases, cysticercosis can lead to significant disability or even death
(CDC, 2023).
Life Cycle:
Humans Are the Definitive Host, Pigs Are the Intermediate Host
The life cycle of Taenia solium involves both humans and pigs
1. Adult Tapeworms in Humans Humans act as the definitive host, meaning that the adult
tapeworms live in their intestines. After consuming undercooked pork containing cysticerci,
the cysts develop into adult tapeworms that release eggs, which are then passed out of the
human body through feces.
Fig 5:Taenia solium

(CDC, 2023)
2. Eggs in the Environment Eggs excreted by humans contaminate the environment and can
be ingested by pigs, the intermediate host Pigs ingest these eggs through contaminated food
or water. Once inside the pig, the eggs hatch into larvae that migrate to the muscles, where
they form cysts (cysticercus).
3. Transmission to Human : Humans become infected by eating undercooked or raw pork
containing these cysts. Once consumed, the cysts hatch and mature into adult tapeworms in
the human intestines. Additionally, humans can ingest Tabenia solium eggs, which leads to
cysticercosis when the larvae travel through the body and form cysts (WHO, 2022).
Prevention:

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Proper Cooking of Pork, Good Sanitation Practices
Preventing infection with Taenia solium requires a combination of proper food handling,
hygiene, and sanitation measures:
1. Proper Cooking of Pork: Cooking pork to an internal temperature of at least 63°C (145°F)
ensures that cysts are killed, preventing taeniasis.
2. Sanitation and Hygiene: Proper sanitation practices, including using toilets, avoiding open
defecation, and washing hands after using the bathroom, help reduce the risk of spreading
Taenia solium eggs.
3.Treatment for Infected Individuals Anti-parasitic medications such as praziquantel or
niclosamide, are effective for treating taeniasis by eliminating adult tapeworms. For
cysticercosis, treatment often involves a combination of antiparasitic drugs and surgery to
remove cysts, particularly in cases of neurocysticercosis (CDC, 2023).
4. Control in Pigs Preventing pigs from consuming human feces and improving overall
sanitation in pig farming are essential measures for reducing the risk of transmission.

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7-Reference

1. Center of disease control and prevention https://www.cdc.gov/parasites/index.html

2. Centers for Disease Control and Prevention. (2022). *Malaria*.

https://www.cdc.gov/malaria

3. World Health Organization. (2023). *Malaria*.

https://www.who.int/news-room/fact-sheets/detail/malaria

4. Centers for Disease Control and Prevention. (2022). Amoebiasis.

https://www.cdc.gov/amoebiasis

5. Centers for Disease Control and Prevention. (2022).

*Giardiasis*. https://www.cdc.gov/parasites/giardia

6. Centers for Disease Control and Prevention. (2023). *Ascariasis*.

https://www.cdc.gov/parasites/ascaris

7. Centers for Disease Control and Prevention. (2023). *Taenia solium*.

https://www.cdc.gov/parasites/taeniasis

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