Lesson 3: Prevention and Treatment Flashcards
(14 cards)
Immunity
Immunity is the result of the persistence of memory cells or antibodies after exposure to a pathogen.
Immunity may be considered active or passive depending on how the antibodies come to be in the body.
Passive Immunity
Passive immunity occurs when there is an introduction of antibodies into the bloodstream.
These antibodies are short lived and are not made by the immune system of the person.
This occurs naturally during fetal development and breastfeeding and artificially through injections of antibodies.
Active Immunity
Adaptive immunity is a result of pathogen exposure and the resulting memory cells to prevent future infection.
This is called active immunity as the immune system actively produces its own antibodies.
Exposure to antigens may occur naturally (by getting sick) or artificially (getting a vaccination).
Vaccination
Also called immunization.
A vaccine is either a live but weakened version of a pathogen or some derivative that contains the antigens.
The vaccine is introduced into the body which stimulates the primary immune response.
This produces memory cells that will trigger the secondary immune response if the actual pathogen is encountered.In many parts of the world routine childhood vaccinations have almost
eliminated many viral diseases.
Children in Canada begin receiving vaccinations soon after birth, these
include diphtheria/tetanus/pertussis (DTaP), polio, hepatitis, chicken pox and measles/mumps/rubella (MMR).
Smallpox
One of the major successes of
vaccination programs worldwide is the eradication of smallpox.
In the 1950’s, potentially fatal
smallpox was affecting 50 million people worldwide.
In 1959 a global initiative was
launched to eradicate smallpox through vaccination.
The last known case of naturally occurring smallpox was in 1977.
Development of the Smallpox Vaccine
Edward Jenner developed the vaccine in the 1800’s when he noticed that milkmaids who had been exposed to cowpox never got sick with smallpox.
He purposely infected an 8 year old boy with cowpox, who got sick and recovered easily. Then he infected him
with smallpox to confirm that he could not catch the disease.
Success of Smallpox Eradication Program
The program started in 1959 but was not well funded until 1967 so results were mixed until that point. The successful eradication of smallpox occurred for several reasons:
Only humans can catch and transmit smallpox
Symptoms of infection emerge rapidly and are visible
Immunity to smallpox is long-lasting
Zoonosis
Some pathogens are highly specific and can only infect a narrow range of hosts such as syphilis, polio and measles.
Other pathogens can cross the species barrier which means that these pathogens infect multiple species as well as humans.
These are called zoonosis and are a growing concern to global health.
There is increasing contact between animals and humans due to the expansion of humans into new areas of the planet.
There is also increased migration of animals into new areas caused by rising global temperatures and displacement from previously occupied areas.
Examples of zoonosis include Bubonic plague, Lyme disease, Bird flu, West
Nile, Zika and COVID-19.
Antibiotics
Most bacterial infections can be treated with antibiotics
Antibiotics are natural substances that slow the growth of bacteria.
Penicillin was the first to be
discovered in 1928 by Alexander Fleming. Today, about 50 different antibiotics are manufactured for medical use.
Antibiotic Function
Antibiotics work because eukaryotic and prokaryotic cells have different metabolic pathways.
Some antibiotics block the protein synthesis pathway in bacteria, others interfere with the formation of the bacterial cell wall
Antibiotics are not effective against viruses since they use host metabolic pathways to reproduce.
Antibiotic Resistance
Antibiotics can kill or block the growth of bacteria but not all bacteria are susceptible.
Some individuals will have a natural resistance to the antibiotic used to kill
them. This may arise by random mutation.
Both resistant and normal strains of bacteria can multiply in the host but only
the susceptible strain will be killed by antibiotics
Resistant strains require stronger doses of antibiotics or different antibiotics.
The more often antibiotics are used the greater the risk that resistance will
develop. The overuse and misuse of antibiotics are thought to have contributed to the rise of resistant strains.
Recently, strains of tuberculosis and gonorrhea have been found to be resistant to all the antibiotics used to treat them.
HIV and AIDS
AIDS (acquired immunodeficiency
syndrome) results from infection by HIV (human immunodeficiency virus).
First recognized in 1981, AIDS has killed more than 27 million people worldwide.
There are currently more than 33 million people living with HIV.
HIV
HIV most often infects helper T cells. This dramatically impairs both the cell
mediated and humoral immune response.
HIV is a retrovirus which means that once it enters a host cell its RNA
genome is reverse transcribed and the new DNA is inserted into the
genome of the T cell.
This enables the production of new viruses by the T cell.
The T cell eventually dies due to the damaging effects of virus production or
virus induced apoptosis.
This releases the newly made viruses to infect more T cells.
As T cells decrease the body is unable to fight the mildest infections.
It can take up to 10 years to develop AIDS symptoms after initial infection.
AIDS is incurable, however certain drugs can slow the reproduction of HIV.
The greatest success has been drugs that stop the transmission of HIV from
mother to child.
There has also been some success in slowing down the progress of AIDS
with combination drug therapies.
However, both of these options are expensive and often unavailable to
the vast majority of people who are most in need.
Antiviral Medications
Antibiotics are ineffective against viral infection.
Most antiviral drugs function as nucleoside mimics that interfere with viral
nucleic acid synthesis.
There is currently a nucleoside mimic called acyclovir that is effective
against the replication of the herpes virus. This inhibits viral polymerase
that synthesizes viral DNA but does not affect eukaryotic DNA production.
