Diseases caused by protozoa Questions in English

(D) $Entamoeba \ histolytica$ is a protozoan parasite that infects the human large intestine. It causes a disease known as amoebiasis or amoebic dysentery. The parasite lives in the lumen of the large intestine,where it feeds on bacteria and mucosal cells,leading to symptoms such as abdominal pain,cramps,and stool with excess mucus and blood clots.

(B) Charles Laveran was a French army surgeon who discovered the malaria parasite $(Plasmodium)$ in the blood of a patient in $1880$. He observed the parasite in the red blood cells,which was the first time a protozoan was identified as the cause of a human disease. For this discovery,he was awarded the Nobel Prize in Physiology or Medicine in $1907$.

(C) The life cycle of the malarial parasite $(Plasmodium)$ involves two hosts: humans and female $Anopheles$ mosquitoes.
Sporogony refers to the sexual phase of the life cycle where sporozoites are formed.
This process occurs within the stomach wall of the female $Anopheles$ mosquito.
After fertilization and development,the sporozoites migrate to the salivary glands of the mosquito to be transmitted to a new human host.

(C) The life cycle of $Plasmodium$ involves two hosts: humans and female $Anopheles$ mosquitoes.
When an infected female $Anopheles$ mosquito bites a human,it injects the $Sporozoite$ stage of the parasite into the human bloodstream along with its saliva.
Therefore,the $Sporozoite$ is the infective stage of $Plasmodium$ for humans.

(A) Kala-azar, also known as visceral leishmaniasis, is caused by the protozoan parasite $Leishmania \text{ donovani}$.
This disease is transmitted to humans through the bite of an infected female sandfly, which belongs to the genus $Phlebotomus$.
$Glossina$ (tsetse fly) transmits sleeping sickness, $Pediculus$ (louse) transmits typhus, and $Aedes$ (mosquito) transmits diseases like dengue and chikungunya.

(D) The malarial parasite,$Plasmodium$,is transmitted to humans through the bite of an infected female $Anopheles$ mosquito.
Male mosquitoes feed only on plant juices and nectar,not on blood,and therefore do not transmit the parasite.
Since none of the options list the female $Anopheles$ mosquito,the correct answer is $D$.

(B) $Leishmania \ donovani$ is the protozoan parasite that causes Kala-azar,also known as visceral leishmaniasis.
It is transmitted to humans through the bite of infected female sandflies ($Phlebotomus$ species).
The parasite primarily affects the internal organs such as the spleen,liver,and bone marrow.

(C) An intracellular parasite is an organism that lives inside the host's cells to complete its life cycle.
$Plasmodium$ is a well-known intracellular parasite that infects human red blood cells and liver cells during its life cycle.
$Entamoeba$ $histolytica$ is primarily an extracellular parasite that lives in the lumen of the large intestine.
$Ascaris$ is an intestinal parasite that lives in the lumen of the small intestine and is not intracellular.
Therefore,the correct answer is $Plasmodium$.

(A) $Entamoeba \ histolytica$ is a pathogenic intestinal parasite that occurs in the colon of humans and causes amoebic dysentery or amoebiasis.
It is a protozoan parasite that infects the large intestine,leading to symptoms such as abdominal pain,diarrhea,and the presence of blood or mucus in the stool.

(C) In the life cycle of the malarial parasite $(Plasmodium)$,the parasite undergoes asexual reproduction (schizogony) inside the $R.B.Cs.$ of the human host.
As the schizont matures and ruptures the $R.B.Cs.$,it releases a toxic substance known as $Haemozoin$.
This $Haemozoin$ is a byproduct of the digestion of haemoglobin by the parasite and is responsible for the characteristic chills and high fever associated with malaria.

(B) The life cycle of the malaria parasite $(Plasmodium)$ involves two hosts: humans and mosquitoes.
In humans,the infection begins when an infected female $Anopheles$ mosquito injects $Sporozoites$ into the bloodstream.
These $Sporozoites$ travel to the liver and undergo the exo-erythrocytic cycle.
After the liver stage,the parasite is released into the blood as $Merozoites$.
These $Merozoites$ then invade the red blood cells $(RBCs)$ to initiate the erythrocytic cycle (the asexual cycle in the blood).

(C) Amoebiasis is a protozoan disease caused by $Entamoeba \text{ histolytica}$.
It is transmitted primarily through the fecal-oral route, often via contaminated food and water.
Drinking boiled water and maintaining proper sanitation are effective preventive measures to avoid the ingestion of cysts of the parasite.
Therefore, drinking boiled water is the correct preventive measure among the given options.

(C) The rupture of infected $R.B.Cs$ leads to the release of $Merozoites$ and a toxic substance called $Haemozoin$ into the blood.
$Haemozoin$ is responsible for the chills and high fever associated with malaria.

(B) The $Tse-tse$ fly ($Glossina$ species) acts as a vector for the protozoan parasite $Trypanosoma$ $gambiense$.
This parasite causes African Sleeping Sickness in humans.
$Leishmania$ $donovani$ is transmitted by the sandfly,$Entamoeba$ $histolytica$ is transmitted through contaminated food and water,and $Plasmodium$ $vivax$ is transmitted by the female $Anopheles$ mosquito.

(A) Cerebral malaria is a severe neurological complication of malaria infection.
It is specifically caused by the protozoan parasite $Plasmodium \ falciparum$.
This species is known for its ability to cause sequestration of infected red blood cells in the brain capillaries,leading to inflammation and cerebral dysfunction.

(D) Quartan malaria is a type of malaria characterized by a fever cycle that recurs every $72$ hours (every fourth day).
This specific pattern of fever is caused by the infection of $Plasmodium malariae$.
In contrast, $Plasmodium vivax$ and $Plasmodium ovale$ cause tertian malaria (fever every $48$ hours), and $Plasmodium falciparum$ causes malignant tertian malaria.

(A) Malignant tertian malaria is a severe form of malaria characterized by high fever and potential complications.
It is caused by the protozoan parasite $Plasmodium$ $falciparum$.
$P. vivax$ and $P. ovale$ typically cause benign tertian malaria,while $P. malariae$ causes quartan malaria.

(A) The female $Anopheles$ mosquito acts as a vector for the malarial parasite $(Plasmodium)$ because it requires a blood meal to obtain the proteins necessary for egg production. In contrast,the male $Anopheles$ mosquito feeds exclusively on plant nectar and fruit juices. Since it lacks the specialized blood-sucking mouthparts required to pierce human skin and ingest blood,it cannot transmit the malarial parasite.

(D) $Entamoeba$ $gingivalis$ is a commensal protozoan found in the human mouth, specifically in the gingival pockets and tartar of teeth.
Unlike other species of $Entamoeba$, it does not form cysts.
Because it lacks a cyst stage, it cannot survive outside the host for long periods.
Therefore, the transmission of the parasite occurs primarily through direct contact, such as kissing or sharing contaminated utensils.

(A) $Entamoeba histolytica$ is a protozoan parasite that causes amoebiasis.
Infection occurs primarily through the ingestion of food or water contaminated with faecal matter containing the tetranucleated cysts of $E. histolytica$.
These cysts are the infective stage of the parasite.

(B) The malarial parasite $(Plasmodium)$ is considered digenetic because its life cycle is completed in two different hosts.
The primary or principal host is human ($Homo$ $sapiens$),where the asexual cycle occurs.
The secondary,intermediate,or vector host is the female $Anopheles$ mosquito,where the sexual cycle occurs.

(D) The erythrocytic cycle (also known as the asexual cycle in humans) of $Plasmodium$ $vivax$ involves the invasion of red blood cells by merozoites, their development into trophozoites and schizonts, and the subsequent release of new merozoites upon the rupture of the host cell.
This cycle in $Plasmodium$ $vivax$ typically takes approximately $48$ hours to complete, which corresponds to the periodicity of the fever associated with this species (tertian malaria).

(B) Schuffner's dots are small,red-staining granules observed in the cytoplasm of red blood cells (erythrocytes) infected with $Plasmodium$ $vivax$ or $Plasmodium$ $ovale$.
These dots represent areas of altered membrane permeability and are a characteristic diagnostic feature of $Malaria$ caused by these specific species of $Plasmodium$.

(A) The life cycle of $Plasmodium$ is digenetic,involving two hosts: humans and female $Anopheles$ mosquitoes.
In the human host,the parasite undergoes asexual reproduction (schizogony and gametogony).
In the female $Anopheles$ mosquito,the parasite undergoes the sexual cycle,which includes fertilization and the formation of the zygote (ookinete) and sporozoites.
Therefore,the sexual cycle occurs within the female $Anopheles$ mosquito.

(C) The life cycle of $Plasmodium$ involves two hosts: humans and the female $Anopheles$ mosquito.
In the human host,the parasite undergoes two main cycles: the exo-erythrocytic cycle (occurring in the liver) and the erythrocytic cycle.
The erythrocytic cycle refers to the asexual reproduction phase of $Plasmodium$ that takes place within the Red Blood Cells $(RBCs)$.
During this stage,the parasite multiplies,leading to the rupture of $RBCs$,which releases toxins like hemozoin,causing the characteristic chills and high fever associated with malaria.

(B) $Plasmodium$ is a digenetic parasite that requires two hosts to complete its life cycle.
$1$. The primary host is the human,where the asexual cycle occurs.
$2$. The secondary (or intermediate) host is the female $Anopheles$ mosquito,where the sexual cycle (fertilization and development of sporozoites) occurs.
Therefore,the female $Anopheles$ mosquito acts as the vector and the secondary host.

(A) $Entamoeba \ coli$ is a commensal organism that inhabits the human colon. It feeds primarily on bacteria and organic debris present in the large intestine.
It does not cause any disease in humans,making it neither harmful nor beneficial to the host. In contrast,$Entamoeba \ histolytica$ causes amoebic dysentery,$E. \ gingivalis$ is associated with periodontal issues,and $Plasmodium \ ovale$ is a causative agent of malaria.

(B) In malaria,the causative agent is the $Plasmodium$ parasite.
When the $Plasmodium$ parasite infects human red blood cells $(RBCs)$,it consumes hemoglobin and releases a toxic substance called $Haemozoin$.
This $Haemozoin$ is released into the blood when the infected $RBCs$ rupture.
The release of $Haemozoin$ is directly associated with the characteristic chills and high fever that recur every $3$ to $4$ days in malaria patients.

(D) The development and maturation of $Plasmodium$ gametocytes (gametogony) within the mosquito's gut are highly sensitive to environmental factors.
$1$. Temperature: The metabolic rate and developmental speed of $Plasmodium$ are directly influenced by the ambient temperature. Optimal temperatures are required for the successful fertilization of gametes.
$2$. Food: The mosquito's blood meal provides the necessary nutrients for the parasite's survival and development.
$3$. Position: The physical location within the mosquito's midgut is crucial for the parasite to encounter the appropriate environment for fertilization and subsequent development into an ookinete.
Therefore,all these factors play a significant role in the life cycle of the parasite within the vector.

(B) Sir Ronald Ross was awarded the Nobel Prize in Physiology or Medicine in $1902$ for his work on malaria,by which he successfully demonstrated how the parasite enters the organism and thereby laid the foundation for successful research on this disease and methods of combating it. He discovered the oocysts of $Plasmodium$ in the stomach wall of the $Anopheles$ mosquito.

(D) The correct answer is $D$.
Sporozoites are spindle or sickle-shaped,uninucleated organisms capable of wriggling movement.
Each sporozoite has a covering formed by an elastic pellicle that contains longitudinal contractile microtubules,which facilitate their motility.

(C) $Entamoeba$ $histolytica$ is the causative agent of amoebiasis (amoebic dysentery).
It is a water-borne and food-borne disease transmitted through the fecal-oral route.
The cysts of the parasite are carried by houseflies from feces of infected persons to food and food products, thereby contaminating them.
Therefore, the infection can be prevented by consuming clean, uncontaminated food and water, and by maintaining proper personal and public hygiene.

(D) The $Plasmodium$ parasite undergoes various stages in the human host.
After the initial development in the liver cells (exo-erythrocytic cycle),the merozoites are released into the blood.
These merozoites invade the $R.B.Cs$ (Red Blood Corpuscles).
Inside the $R.B.Cs$,the parasite transforms into a young trophozoite stage,which then feeds on hemoglobin and grows.
Therefore,the trophozoite stage of $Plasmodium$ is found within the $R.B.Cs$.

(B) The asexual cycle of $Plasmodium$ that occurs in the human host is known as schizogony.
This process takes place in the liver cells (exo-erythrocytic schizogony) and red blood cells $(RBCs)$ (erythrocytic schizogony).
Schizogony is a specific type of multiple fission where a single parent cell divides into many daughter cells simultaneously.

(A) The life cycle of $Plasmodium$ involves two hosts: humans and female $Anopheles$ mosquitoes.
In the human host,the $Plasmodium$ parasite undergoes asexual reproduction in liver cells (exo-erythrocytic cycle) and red blood cells (erythrocytic cycle).
After several cycles of asexual reproduction in the red blood cells,some merozoites differentiate into gametocytes (male and female gametes).
Therefore,the development of gametocytes from merozoites occurs within the red blood corpuscles $(RBCs)$ of the human host.

(D) The life cycle of $Entamoeba histolytica$ involves the formation of a quadrinucleate cyst. When this cyst is ingested by a human host,it passes through the stomach and reaches the small intestine. In the small intestine,the cyst wall undergoes excystation. The four nuclei within the cyst divide,and the cytoplasm divides accordingly,resulting in the formation of $8$ small,active trophozoites (metacyclic trophozoites) from a single quadrinucleate cyst.

(A) $Entamoeba \ histolytica$ is a protozoan parasite that causes amoebiasis (amoebic dysentery).
Symptoms of this infection include constipation,abdominal pain,cramps,and stools with excess mucus and blood clots.
Relapsing fever is a vector-borne disease caused by $Borrelia$ species,not by $Entamoeba \ histolytica$.
Therefore,relapsing fever is not a symptom of this infection.

(D) $Plasmodium$ $ovale$ is a species of $Plasmodium$ that causes malaria in humans. It is primarily found in West Africa and has also been reported in parts of South America and Southeast Asia. Unlike $P. falciparum$ or $P. vivax$, it is less common globally but has a distinct geographical distribution.

(A) In malaria,the periodic recurrence of high fever and chills is caused by the release of toxic substances known as $hemozoin$ into the blood. This release occurs when the $Plasmodium$ parasite completes its $erythrocytic$ $schizogony$ cycle,leading to the rupture of infected red blood cells. The cycle of fever corresponds to the time taken for the parasite to complete this asexual reproduction phase within the human red blood cells.

(B) $Haemozoin$ is a yellow-brown to blackish,insoluble polymer of ferriprotoporphyrin.
It is formed as a byproduct of the breakdown of haemoglobin by the malaria parasite $(Plasmodium)$.
These toxic crystals accumulate in various tissues of the host,such as the spleen,liver,and skin,leading to the characteristic symptoms and pigmentation observed during malaria infection.

(A) In malaria,the high fever and chills are caused by the release of a toxic substance called $hemozoin$ into the blood.
This release occurs when the $Plasmodium$ parasite completes its $erythrocytic$ $schizogony$ (the cycle within the red blood cells).
As the infected red blood cells rupture to release the merozoites and the metabolic waste products (hemozoin),the host experiences a sudden spike in body temperature.

(D) $Plasmodium$ is inoculated into humans by the female $Anopheles$ mosquito.
This occurs because the female $Anopheles$ mosquito injects saliva into the human bloodstream while puncturing the skin to obtain a blood meal.
The infected mosquito carries a large number of $sporozoites$ in its salivary glands,which are then transmitted into the human blood.

(D) The tetranucleate (quadrinucleate) cyst is the infective stage of $Entamoeba$ $histolytica$.
Infection occurs through the oral route by consuming food and water contaminated with these cysts.

(A) $Leishmania \ donovani$ is the protozoan parasite that causes $Kala-azar$ (also known as $Dum-dum$ fever).
This parasite is transmitted to humans through the bite of an infected female sandfly ($Phlebotomus$ species).

(D) $Leishmania$ $tropica$ causes skin lesions or ulcers known as Oriental sores or Delhi sores. These are transmitted to humans through the bite of an infected female sand fly ($Phlebotomus$ species).

(D) Chloroquine is an antimalarial medication.
It is primarily used to prevent and treat malaria caused by mosquito bites.
It works by interfering with the growth of parasites in the red blood cells of the human body.

(A) $Entamoeba \ coli$ is a non-pathogenic protozoan that lives as a commensal in the human large intestine (colon).
It feeds on bacteria and food particles without causing any harm to the host.
In contrast,$Plasmodium \ vivax$ is a parasite causing malaria,and $Aedes \ aegypti$ is a mosquito vector,not a protozoan.

(D) The symptoms of malaria,such as chills and high fever (paroxysms),are caused by the release of a toxic substance called $hemozoin$ into the blood.
This release occurs when the $Plasmodium$ parasite completes its $erythrocytic$ $cycle$ (the cycle within red blood cells) and ruptures the host's red blood cells.
Therefore,the correct answer is the $erythrocytic$ $cycle$.

(B) Relapsing malaria is caused by the presence of dormant liver stages known as hypnozoites.
These hypnozoites remain inactive in the liver cells and can reactivate later to cause a relapse of the infection.
$P. vivax$ and $P. ovale$ are the two species of Plasmodium that are known to form hypnozoites in the human liver,leading to relapsing malaria.