ENVIRONMENTAL SCIENCE : HUMAN POPULATION AND ENVIRONMENT 235
Vibrio El tor: The other germ Vibrio el tor spreads in the Bay of Bengal and coastal
areas in large scale through direct contact, unhygienic conditions, over-crowding, fair and
feast on festivals incubation period: The duration of incubation period is very short, ranging
from a few hours to five days.
Period of communicability: Lasts until the patient is free from cholera germs.
Symptoms: Patient starts vomiting and suffers loose motions. This may lead to loss of
water and minerals in the body.
Immunization: Vaccine is prepared from dead Vibrio cholera and is given when there
is a danger of spread of cholera.
Prevention and Control
- All deject should be collected in the can in which quick lime is placed at the bottom.
- Anti-fly measures should be adopted.
- Avoid eating of rotten fruit, boiling of water and milk, protection from flies and
dust. - Phenyl, bleaching powder and other disinfectant should be sprayed in the area.
- Segregation and disinfections of soiled clothes, articles used by the patient.
- MALARIA
Malaria spreads in the rainy season. The malarial parasite is a protozoon named
‘Plasmodium’. It survives in the red blood corpuscles of the human blood. Man acquires
infection by the bite of an infected female anopheles mosquito, which inject the malarial
parasites in the form of spores.
The malarial parasite is of four types:
(i) Plasmodium: It has a life cycle of 48 hours causing fever after every two days..
(ii) Plasmodium malaria: It has a life cycle of 72 hours causing fever after every three days.
(iii) Plasmodium falciparum: Irregular fever may occur after every ’48 hours. The
symptoms are very severe and of malignant type: high fever, delirium and death
(iv) Plasmodium ovale: This virus produces mild kind of malaria. They are found mostly
in Africa.
Incubation Period: The time when the insect bites and till the symptoms appear is
called incubation period, which is as follows:
- Plasmodium vivex—14 days
- Plasmodium malaria—30 days
- Plasmodium falciparum—12 days
Spread of disease: Female anopheles mosquito spreads malaria disease. For the spread
of the disease, the optimum conditions are a mean temperature of 20° to 30°C with 63%
humidity. Economic conditions, insufficient food, over-crowding, increase the incidence of
malaria. Irrigation, leakage in canals, water logging, and rice cultivation may serve as the
breeding place for mosquitoes.