Infectious Disease

Infectious Disease are caused by PATHOGENS

FUNGI: e.g. Athlete's foot is caused by fungi                                                                     BACTERIA: e.g. cholera is caused by bacteria                                                                       VIRUSES: e.g. flu is caused by a virus


  • Caused by a protozoan. Carried by mosquitoes, which are insects that feed on the blood of animals, including humans.
  • The protozoan is a parasite- an organism that lives off another organism, often causing it harm.
  • Mosquitoes are VECTORS, meaning they carry the disease without getting it themselves. They pick up the malarial parasite when they feed on an infected animal. Everytime the mosquito feeds on another animal, it infects it by inserting the parasite into the animal's  blood vessels.                                                                                                                     WAYS TO TARGET MOSQUITOES:
  • Areas of water where mosquitoes lay their eggs can be drained or sprayed with insecticies
  • Fish can be introdused into water to eat mosquito larvae
  • People can be protected from mosquitoes using insecticides and mosquito nets.
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How the Immune System deals with Pathogens

White Blood cells are the most important part of your immune system, as their job is to destroy pathogens that try to invade your body. When they come across an invading microorganism, they have 3 lines of attack:

1) By Consuming Them: White blood cells can ENGULF foreign cells and DIGEST them.

2) Producing Antitoxins: They counter the effect of any poisons (toxins) produced by the invading pathogens.

3) Producing Antibodies: Every pathogen has unique molecules on the surface of its cells; no two pathogens have the same ones. These molecules are called pathogens.

When your wbc comes across a foreign antigen, they'll start to produce proteins called antibodies which lock on to and kill the invading cells. The antibodies produced are specific to that pathogen-they won't lock onto other pathogens.

Antibodies are then produced rapidly and flow around the body, killing all similar bacteria.

Some of the wbcs stick around in the blood after the pathogen has been fought off. These are called MEMORY CELLS. If the person is infected with the same pathogen again, these cells will remember it and immediately make antibodies to kill it.

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Continuation of previous card

ACTIVE IMMUNITY: Once wbc are familiar to a particular pathogen, they will produce the same antibodies much faster if that same pathogen is detected again. This provides future detection against the disease and is called ACTIVE IMMUNITY. Active immunity can also be achieved through vaccination.

PASSIVE IMMUNITY: This occurs when anibodies are put into a person's body. An example of this would be the breast milk from the mother, which is given to her baby through breastfeeding. Another example would be snake venom. The pathogen in snake venom acts very quickly and the white blood cells cannot produce antibodies for the pathogen very quickly, so the victim has to be injected with antibodies to kill the pathogen.

1. A weakened/dead strain bacteria is injected. The pathogen has been heat treated so it won't multiply inside the person. But the antigen molecules remain intact.
2. Even though they are harmless, the antigens on the pathogen trigger the wbc to produce specific antibodies.
3. The wbc, called memory cells, will now produce antibodies if the same pathogen was detected again.

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