Biology Today — May 2017

Symptoms Fig.:^ Life^ cycle^ of^ Plasmodium

• Malaria is characterised by fever at intervals, each attack of malaria fever shows three successive stages:
(i) Cold stage - At the onset of fever, patient suffers a severe shaking chill and needs to be covered with huge pile of blankets.
It lasts for 20 minutes to one hour.
(ii) Hot stage - As chill subsides, the body temperature rises as high as 41-106°F. It lasts for 1-4 hours.
(iii) Sweating stage - As the temperature drops, patients sweats profusely. Finally the fever comes down and temperature
becomes normal.

• Malaria is also accompanied by nausea, headache, laziness and muscular pain. It also results in anaemia and splenomegaly.

Prevention and Treatment

Spraying DDT, BHC and

other insecticides

Fitting doors and windows

with wire nets

Using mosquito nets

and repellants

Use of drugs like chloroquine,

quinine, primaquine, etc.

Table: Other protozoan diseases

Disease Pathogen Mode of transmission/

Incubation period

Symptoms Control measures /

Treatment

1. Amoebiasis Entamoeba
   histolytica

Faecal - oral route, sexual

contact, vectors, e.g.,flies.

/ 2-4 weeks

Abdominal pain,

diarrhoea, blood in

faeces, passing out of

mucus

Sanitation, protection

of food from flies.

Emetine, stremetine and

metronidazole

2. Giardiasis Giardia
   intestinalis

Contaminated food and

water / 1-3 weeks

Epigastric pain,

headache, diarrhoea

Clean food and water/

Metronidazole, tinidazole

MOSQUITO

(PRIMARY HOST)

HUMAN

(SECONDARY HOST)

Sporozoites

Salivary glands

Mid-gut

Ookinete

Fertilised female gamete

becomes zygote which

further forms ookinete.

Sexual stage (gametocytes)

develop in red blood cells.

Parasites reproduce asexually in

red blood cells, bursting the red

blood cells and causing cycles

of fever and other symptoms.

Released parasites infect new

red blood cells.

Blood stage

Hepatic schizont Merozoites

Sporozoites

reach the liver

through blood

Erythrocyte

Liver The^ parasite^ reproduces^ asexually^

in liver cells, bursting the cell and

releasing into the blood.

Ruptured

schizont

Infected

hepatocyte

Early

trophozoite

(ring stage)

Ruptured

schizont

Schizont

Mature trophozoite

Ookinete attaches

to gut and

becomes oocyst

Fertilisation and development take

place in the mosquito’s stomach.

Oocyst ruptures to

release sporozoite.

Female mosquito

takes up gametocytes

with blood meal.

Mature infective stages

(sporozoites) escape from

intestine and migrate to the

mosquito salivary glands