Diseases caused by protozoa Questions in English

(C) World Malaria Day is an international observance celebrated every year on $25^{th}$ April.
It is recognized by the World Health Organization $(WHO)$ to highlight the need for continued investment and sustained political commitment for malaria prevention and control.

(A) The incubation period is the time interval between the entry of the parasite into the human body through the bite of an infected female $Anopheles$ mosquito and the appearance of the first symptoms of the disease (such as fever).
For $Plasmodium$ $vivax$,the incubation period is generally about $10$ to $14$ days.
Among the given options,$10-11$ days is the most accurate range for the clinical manifestation of malaria.

(B) Mepacrine (also known as quinacrine) and paludrine (proguanil) are antimalarial drugs.
These medications are specifically used in the treatment and prevention of $Malaria$,a disease caused by $Plasmodium$ parasites.
Therefore,the correct option is $B$.

(A) $Entamoeba \ coli$ is a commensal protozoan found in the human large intestine. It is generally considered non-pathogenic and does not cause disease in healthy human beings.
$Plasmodium \ ovale$ is a parasite that causes malaria.
$Entamoeba \ histolytica$ is the causative agent of amoebic dysentery (amoebiasis).
$Entamoeba \ gingivalis$ is found in the human mouth and is often associated with periodontal diseases.

(A) Malaria is a protozoan disease caused by the parasite $Plasmodium$ (e.g.,$Plasmodium$ $vivax$,$Plasmodium$ $malariae$,$Plasmodium$ $falciparum$).
It is transmitted to humans through the bite of an infected female $Anopheles$ mosquito.
$Hookworm$,$Ascaris$,and $Filaria$ $worm$ are helminths that cause other types of diseases,not malaria.

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

(D) $Entamoeba \ gingivalis$ is a commensal protozoan parasite that resides in the human oral cavity,specifically in the gingival pockets and between the teeth.
It feeds on bacteria,food particles,and epithelial cells.
Unlike $Entamoeba \ histolytica$,which causes amoebic dysentery,$Entamoeba \ gingivalis$ is generally considered non-pathogenic,although it is often found in higher numbers in individuals with poor oral hygiene or periodontal disease.

(B) $Plasmodium$ is a protozoan parasite that causes malaria in humans.
It is an intracellular parasite because it completes a part of its life cycle inside human red blood cells $(RBCs)$ and liver cells.
$Ancylostoma$ is a helminth (roundworm) that lives in the intestine.
$Mosquito$ is a vector,not a parasite of humans.
$Entamoeba$ $histolytica$ is an intestinal parasite that lives in the lumen of the large intestine,not inside the cells.

(C) $Entamoeba \ histolytica$ causes amoebiasis,which is transmitted through the fecal-oral route by the ingestion of contaminated food and water containing cysts.
By washing hands before taking meals,we can prevent the transfer of these cysts from contaminated surfaces to the mouth,thereby checking the infection.

(B) The malarial parasite,$Plasmodium$,was first discovered by the French army surgeon Charles Louis Alphonse Laveran in $1880$.
He observed the parasite in the blood of a patient suffering from malaria.
Ronald Ross later discovered the role of the $Anopheles$ mosquito as a vector for the transmission of malaria.

(A) $Entamoeba \ histolytica$ is a parasitic protozoan that causes amoebic dysentery in humans.
$Paramecium \ caudatum$ is a free-living ciliate protozoan.
$Euglena \ viridis$ is a photosynthetic flagellate protozoan.
$Ascaris \ lumbricoides$ is a parasitic nematode (roundworm),not a protozoan.

(A) The life cycle of the malaria parasite $(Plasmodium)$ involves two hosts: humans and the female $Anopheles$ mosquito.
In the human host,the parasite undergoes asexual reproduction (schizogony) in the liver cells (exo-erythrocytic cycle) and in the red blood cells (erythrocytic cycle).
The stage known as the $Schizont$ is a multinucleated stage formed during the process of schizogony,where the parasite divides into multiple merozoites.
This stage occurs within the $RBCs$ (erythrocytes) and liver cells of the human host.

(A) $Entamoeba histolytica$ is a monoxenous parasite,meaning it completes its life cycle in a single host,which is the human.
$Plasmodium vivax$ is a digenetic parasite requiring two hosts: humans and the female $Anopheles$ mosquito.
$Taenia solium$ (pork tapeworm) is also digenetic,requiring humans as the definitive host and pigs as the intermediate host.
$Trypanosoma gambiense$ requires two hosts: humans and the tsetse fly ($Glossina$ species).

(C) Malaria is a protozoan disease caused by the genus $Plasmodium$ (e.g., $Plasmodium$ $\text{vivax}$, $Plasmodium$ $\text{malariae}$, $Plasmodium$ $\text{falciparum}$).
The female $Anopheles$ mosquito acts as a vector that transmits the parasite from an infected person to a healthy person.
Therefore, the causative agent of the disease is the $Plasmodium$ parasite, not the mosquito itself.

(A) Sleeping sickness, also known as African trypanosomiasis, is caused by protozoan parasites of the genus $Trypanosoma$.
These parasites are flagellated protozoans, meaning they possess flagella for locomotion.
$Trypanosoma brucei$ is the specific species responsible for this disease in humans, transmitted by the tsetse fly.

(C) $Plasmodium$ is the causative agent of malaria.
It is a protozoan parasite that requires two hosts to complete its life cycle: humans and the female $Anopheles$ mosquito.
The female $Anopheles$ mosquito acts as a vector.
When the female $Anopheles$ mosquito bites a human,it injects the infectious stage of the parasite,known as sporozoites,into the human bloodstream along with its saliva.
Male mosquitoes feed only on plant juices and do not bite humans.

(C) Malaria is caused by the genus $Plasmodium$,which is a protozoan parasite.
It is transmitted to humans through the bites of infected female $Anopheles$ mosquitoes.
Since $Plasmodium$ belongs to the group of protozoa,the correct answer is $C$.

(B) The malaria parasite,$Plasmodium$,is a digenetic parasite,meaning it requires two hosts to complete its life cycle.
$1$. The primary host is the female $Anopheles$ mosquito,where the sexual phase of the life cycle (gametogony and syngamy) occurs.
$2$. The secondary (intermediate) host is the human,where the asexual phase of the life cycle (schizogony and exo-erythrocytic cycle) takes place.

(A) The malaria parasite,$Plasmodium$,infects human red blood cells $(RBCs)$.
Inside the $RBCs$,the parasite breaks down hemoglobin into globin and heme.
The heme is toxic to the parasite,so it polymerizes it into a non-toxic,insoluble crystalline pigment known as $Haemozoin$.
When the $RBCs$ rupture,$Haemozoin$ is released into the bloodstream,which triggers the characteristic chills and high fever associated with malaria.

(B) Haemozoin is a toxic substance released during the infection of malaria.
It is produced by the breakdown of hemoglobin within the red blood cells $(RBCs)$ by the malarial parasite $(Plasmodium)$.
When the parasite consumes the globin part of hemoglobin,the remaining heme group is toxic and is converted into a crystalline,non-toxic pigment called haemozoin.
Therefore,it is derived from the colour pigment (heme) of the $RBC$.

(A) Chloroquine is a well-known antimalarial medication.
It belongs to the class of drugs called aminoquinolines.
It works by interfering with the growth of parasites in the red blood cells of the human body,specifically targeting the $Plasmodium$ species that cause malaria.
Therefore,it is primarily used for the treatment and prevention of malaria.

(D) Malaria is a protozoan disease caused by species of $Plasmodium$ (e.g.,$P. vivax$,$P. malariae$,$P. falciparum$).
These parasites are transmitted from an infected person to a healthy person through the bite of an infected female $Anopheles$ mosquito.
The female $Anopheles$ mosquito acts as a vector because it requires blood for the maturation of its eggs,while male mosquitoes feed only on plant juices and do not bite humans.

(C) The malarial parasite,$Plasmodium$,completes its asexual cycle in human red blood cells ($RBC$s).
As the parasite multiplies,the $RBC$s eventually rupture.
Upon rupture,they release a toxic substance called haemozoin,which is responsible for the chill and high fever that recurs every $3$ to $4$ days in malaria patients.

(C) Amoebiasis,also known as amoebic dysentery,is an infection of the intestinal tract caused by the protozoan parasite $Entamoeba \ histolytica$.
This parasite is transmitted through the fecal-oral route,typically by consuming contaminated food or water.
It infects the large intestine,leading to symptoms such as abdominal pain,diarrhea,and stools with mucus and blood.

(D) Kala-azar,also known as visceral leishmaniasis,is a protozoan disease.
It is caused by the parasite $Leishmania \ donovani$.
This parasite is transmitted to humans through the bite of an infected female sandfly ($Phlebotomus$ species).

(C) Cerebral malaria is a severe complication of malaria infection that affects the brain.
It is specifically caused by the protozoan parasite $Plasmodium$ $falciparum$.
This species is known for causing the most lethal form of malaria, often leading to neurological symptoms such as coma, seizures, and death if left untreated.

(B) The correct answer is $B$.
$Anopheles culicifacies$ is a vector for Malaria, not Leishmaniasis.
Leishmaniasis (Kala-azar) is transmitted by the sandfly, $Phlebotomus$ species.
$Aedes aegypti$ is the vector for Yellow fever and Dengue.
$Glossina palpalis$ (Tsetse fly) is the vector for African Sleeping sickness caused by $Trypanosoma brucei$.
$Culex pipiens$ is a common vector for Filariasis (Wuchereria bancrofti).

(C) In malaria,the fever is caused by the release of a toxic substance called $hemozoin$ from the infected red blood cells $(RBCs)$.
When the $Plasmodium$ parasite completes its erythrocytic cycle,the $RBCs$ rupture to release the merozoites into the bloodstream.
Along with the merozoites,the $hemozoin$ toxin is also released,which triggers the release of cytokines and causes the characteristic chills and high fever associated with malaria.

(D) vector is an organism that transmits a disease-causing pathogen from one host to another.
Among the given options, the $Bug$ (specifically the Triatomine bug or 'kissing bug') acts as a vector for the parasite $Trypanosoma \, cruzi$, which causes Chagas disease.
$House \, fly$ is a mechanical carrier but not a parasite itself.
$Fasciola$ and $Ascaris$ are endoparasites that do not act as vectors for other pathogens.

(D) The correct pair is $Culex - Filariasis$.
$1$. $Culex$ mosquitoes are the primary vectors for $Wuchereria bancrofti$,the parasite that causes $Filariasis$ (also known as $Elephantiasis$).
$2$. $House fly$ is a mechanical carrier for diseases like $Typhoid$ and $Cholera$,not $Yellow fever$.
$3$. $Bed bug$ is not a vector for $Kala-azar$; $Kala-azar$ (Leishmaniasis) is transmitted by the $Sand fly$ $(Phlebotomus)$.
$4$. $Sand fly$ transmits $Kala-azar$,whereas $Amoebic dysentery$ is caused by $Entamoeba histolytica$ through contaminated food and water.

(A) $Entamoeba \ histolytica$ is a protozoan parasite in the large intestine of humans which causes amoebiasis (amoebic dysentery).
When the parasite invades the intestinal mucosa,it can enter the bloodstream and travel to other organs like the liver,lungs,and brain.
In these organs,it causes the formation of abscesses (tissue destruction and pus formation),which is a serious complication of extra-intestinal amoebiasis.

(A) Malaria is a disease caused by protozoan parasites belonging to the genus $Plasmodium$.
Typhoid is caused by the bacterium $Salmonella$ $typhi$.
Tetanus is caused by the bacterium $Clostridium$ $tetani$.
Yellow fever is caused by a virus (Flavivirus).

(C) The life cycle of $Plasmodium$ involves two hosts: humans and female $Anopheles$ mosquitoes.
In the mosquito's stomach,the gametocytes fuse to form a zygote.
The zygote undergoes further development to form an oocyst.
These oocysts are embedded in the wall of the mosquito's stomach,where they undergo sporogony to produce sporozoites.

(D) Cerebral malaria is a severe complication of malaria that affects the brain. It is specifically caused by the protozoan parasite $Plasmodium falciparum$. This species is known to cause the most lethal form of malaria,often leading to neurological symptoms and coma.

(B) The recurrence of malaria,often referred to as relapse,is primarily caused by the persistence of dormant stages of the parasite in the liver cells,known as hypnozoites. These hypnozoites are associated with the pre-erythrocytic cycle (specifically the exo-erythrocytic phase) of $Plasmodium$ species like $P. vivax$ and $P. ovale$. After a period of dormancy,these parasites are released into the bloodstream,initiating a new erythrocytic cycle and causing a recurrence of symptoms.

(C) The genus $Plasmodium$ includes several species that cause malaria in humans.
Among these,$Plasmodium \ falciparum$ is responsible for the most severe and life-threatening form of the disease,known as malignant malaria.
It can lead to cerebral malaria,which is often fatal if not treated promptly.
Therefore,$Plasmodium \ falciparum$ is considered the most lethal species.

(B) The incubation period is the time interval between the entry of the parasite into the human body through the bite of an infected female $Anopheles$ mosquito and the appearance of the first symptoms of malaria.
For $Plasmodium$ $vivax$,the incubation period typically ranges from $10$ to $14$ days,with an average of about $10$ to $12$ days.
Therefore,among the given options,$10$ days is the most accurate representation of the incubation period for $Plasmodium$ $vivax$.

(A) The life cycle of the malaria parasite $(Plasmodium)$ involves two hosts: humans and the female $Anopheles$ mosquito.
In the human host,the parasite undergoes asexual reproduction.
After entering the human body via a mosquito bite,the sporozoites infect liver cells (exo-erythrocytic cycle) and subsequently infect red blood cells $(RBCs)$ (erythrocytic cycle).
Inside the $RBCs$,the parasite develops into a trophozoite and then into a schizont.
The schizont undergoes multiple fission to produce merozoites,which are released upon the rupture of the $RBCs$.

(B) $Plasmodium$ is a protozoan parasite that infects human red blood cells $(RBCs)$ and liver cells.
Since it lives and reproduces inside the cells (specifically erythrocytes),it is classified as a cytozoic parasite.
'Cyto-' refers to cell and '-zoic' refers to animal/living,thus 'cytozoic' means living within cells.

(A) Entamoeba histolytica is a protozoan parasite that infects the large intestine of humans,not the small intestine. Therefore,statement $(1)$ is incorrect.
It causes amoebiasis (amoebic dysentery),which is characterized by symptoms like constipation,abdominal pain,and cramps. Therefore,statement $(4)$ is correct.
Houseflies act as mechanical carriers and serve to transmit the parasite from faeces of infected persons to food and food products,thereby contaminating them. Therefore,statement $(3)$ is correct.
Since statement $(1)$ is the only incorrect statement,the correct option is $(1)$.

(C) The life cycle of $Plasmodium$ involves two hosts: humans and female $Anopheles$ mosquitoes.
In the human host,$Plasmodium$ undergoes asexual reproduction.
In the mosquito host,$Plasmodium$ undergoes sexual reproduction.
The sexual stage,which includes the formation of gametocytes,fertilization,and the development of the zygote into an ookinete,occurs specifically within the $midgut$ (intestine) of the female $Anopheles$ mosquito.
Therefore,the correct answer is the intestine of the mosquito.

(B) Quartan malaria is a type of malaria caused by the parasite $Plasmodium$ $malariae$.
In this type of infection,the fever cycle repeats every $72$ hours (the $4$th day),which is why it is termed 'quartan' malaria.
$Plasmodium$ $vivax$ and $Plasmodium$ $ovale$ typically cause tertian malaria (fever every $48$ hours).
$Plasmodium$ $falciparum$ causes malignant tertian malaria,which is the most severe form.

(B) The life cycle of $Plasmodium$ begins when an infected female $Anopheles$ mosquito bites a human.
During this bite,the parasite is injected into the human bloodstream in the form of $Sporozoites$.
$Sporozoites$ are the infectious stage of the $Plasmodium$ parasite.
Once inside the human body,they travel to the liver to initiate the infection cycle.

(B) The life cycle of $Plasmodium$ involves two hosts: humans and female $Anopheles$ mosquitoes.
In the human host,$Plasmodium$ undergoes asexual reproduction (schizogony) in the liver and $RBCs$.
When the female $Anopheles$ mosquito bites an infected person,it ingests the gametocytes along with the blood.
Gametogenesis (formation of gametes) and fertilization occur within the gut (stomach) of the mosquito.
Therefore,the correct location for gametogenesis is the mosquito gut.

(D) In the life cycle of $Plasmodium$,the gametocytes are formed in the human blood.
These are of two types: microgametocytes (male) and macrogametocytes (female).
The differentiation between these two is based on several morphological characteristics:
$1$. Size: Macrogametocytes are generally larger than microgametocytes.
$2$. Position of the nucleus: In microgametocytes,the nucleus is large and centrally located,whereas in macrogametocytes,it is smaller and peripherally located.
$3$. Hemozoin granules: The distribution and appearance of hemozoin pigment granules also differ between the two types.
Therefore,all the given options are correct criteria for their differentiation.

(B) In the life cycle of $Plasmodium$,fertilization occurs in the gut of the female $Anopheles$ mosquito. The fusion of male and female gametes results in the formation of a diploid zygote. This zygote undergoes transformation into an elongated,motile form known as the $Ookine$ (or $ookinete$). The $Ookine$ then penetrates the mosquito's gut wall to develop into an $Oocyst$.

(B) The life cycle of $Plasmodium$ (the malarial parasite) involves two hosts: humans and female $Anopheles$ mosquitoes.
When an infected female $Anopheles$ mosquito bites a healthy human,it injects the infectious stage of the parasite,known as $Sporozoites$,into the human bloodstream along with its saliva.
These $Sporozoites$ then travel to the liver to begin the infection cycle.
Therefore,the correct option is $B$.

(A) The life cycle of $Plasmodium$ is digenetic,involving two hosts: humans (asexual cycle) and female $Anopheles$ mosquitoes (sexual cycle).
After the mosquito ingests the gametocytes from an infected human,the sexual reproduction (fertilization and development) occurs within the mosquito's gut.
This process,known as sporogony,typically takes about $10$ to $20$ days to complete,resulting in the formation of sporozoites that migrate to the mosquito's salivary glands.

(D) During a malaria infection,the body's immune system responds to the presence of the $Plasmodium$ parasite.
Monocytes are a type of white blood cell that plays a crucial role in phagocytosis,which is the process of engulfing and destroying pathogens.
As the $Plasmodium$ parasites are released into the bloodstream from ruptured red blood cells,the count of monocytes significantly increases to combat the infection.
Therefore,the correct answer is $D$ (Monocytes).

(B) When an infected female $Anopheles$ mosquito bites a human,it releases the $Plasmodium$ parasites in the form of $Sporozoites$ from its salivary glands into the human bloodstream.
These $Sporozoites$ then travel to the liver,where they infect liver cells and multiply,eventually leading to the release of $Merozoites$ into the blood.
Therefore,the infective stage for humans is the $Sporozoite$.