Friday, November 4, 2016
Chapter 10 summay
Summary
■■ The term disease is defined as a disorder or illness that
disrupts the normal functioning of the body or mind.
Infectious diseases are caused by organisms known
as pathogens that invade the body. Non-infectious
diseases are all other diseases that are not caused by
pathogens. There are many categories of non-infectious
disease including genetic diseases (inherited) and
deficiency diseases (caused by malnutrition).
■■ Cholera, malaria, HIV/AIDS, tuberculosis (TB) and
measles are all examples of infectious diseases.
Smallpox was an infectious disease but was eradicated
in the late 20th century.
■■ Cholera is caused by the bacterium Vibrio cholerae and
is transmitted in water or food contaminated by the
faeces of infected people. Cholera can be controlled by
treating patients with intravenous or oral rehydration
therapy and making sure that human faeces do not
reach the water supply. The disease is prevented by
providing clean, chlorinated water and good sanitation.
■■ Malaria is caused by four species of Plasmodium. The
most dangerous is P. falciparum. Malaria is transmitted
by an insect vector: female Anopheles mosquitoes
transfer Plasmodium from infected to uninfected people.
Malaria is controlled in three main ways: by reducing the
number of mosquitoes through insecticide spraying or
draining breeding sites; by using mosquito nets (more
effective if soaked in insecticide); by using drugs to
prevent Plasmodium infecting people.
218
Cambridge International AS Level Biology
■■ AIDS is a set of diseases caused by the destruction
of the immune system by infection with human
immunodeficiency virus (HIV). HIV is transmitted in
certain body fluids: blood, semen, vaginal secretions
and breast milk. HIV primarily infects economically
active members of populations in developing countries
and has an extremely adverse effect on social and
economic development.
■■ The transmission of HIV can be controlled by using
barrier methods (e.g. condoms and femidoms) during
sexual intercourse. Educating people to practise safer
sex is the only control method currently available to
health authorities. Contact tracing is used to find people
who may have contracted HIV, so that they can be tested
and counselled.
■■ Life expectancy can be greatly extended by using
combinations of drugs which interfere with the
replication of HIV. However, such treatment is expensive,
is difficult to maintain and has unpleasant side-effects.
There is no vaccine for HIV and no cure for AIDS.
■■ TB is caused by the bacteria Mycobacterium tuberculosis
and M. bovis. M. tuberculosis is spread when people
infected with the active form of the disease release
bacteria in droplets of liquid when they cough or sneeze.
Transmission occurs when uninfected people inhale the
bacteria. This is most likely to happen where people live
in overcrowded conditions, and especially where many
sleep close together.
■■ Many people have the inactive form of TB in their lungs,
but they do not have the disease and do not spread it.
The inactive bacteria may become active in people who
are malnourished or who become infected with HIV. M.
bovis causes TB in cattle, but can be passed to humans.
Drugs are used to treat people with the active form
of TB. The treatment may take nine months or more
as it is difficult to kill the bacteria. Contact tracing is
used to find people who may have caught the disease.
These people are tested for TB and treated if found to
be infected. The BCG vaccine provides some protection
against TB, but its effectiveness varies in different parts
of the world.
■■ Measles is an extremely contagious disease caused
by a virus that inhabits the cells of the nasal cavity
and trachea. Infected people sneeze or cough out
droplets which contain millions of virus particles. If
these are inhaled by a person with no immunity, it
is almost certain that they will be infected with the
disease. Symptoms include fever and a rash. There is
no specific medicine for measles – treatment is rest and
medicine to reduce the fever. Measles is controlled in
economically developed countries by vaccination and
there are very few outbreaks of the disease, but is a
major disease in developing countries.
■■ Public health measures are taken to reduce the
transmission of all of these infectious diseases, but to be
effective they must be informed by a knowledge of the
life cycle of each pathogen.
■■ Antibiotics are drugs that are used to treat infections
caused by pathogenic bacteria. They are compounds
that are made by microorganisms and modified
chemically to increase their effectiveness. Penicillin
prevents the production of new cell walls in bacteria
and so does not affect viruses or human cells, neither
of which have cell walls. Not all antibiotics are effective
against all bacteria.
■■ Resistance to antibiotics can arise because some
bacteria may, by chance, contain a resistance gene. The
bacteria survive when exposed to the antibiotic and can
then reproduce to form a large population of bacteria all
containing this gene. This is called vertical transmission
of resistance. Resistance can also be spread between
bacteria by horizontal transmiss
■■ The term disease is defined as a disorder or illness that
disrupts the normal functioning of the body or mind.
Infectious diseases are caused by organisms known
as pathogens that invade the body. Non-infectious
diseases are all other diseases that are not caused by
pathogens. There are many categories of non-infectious
disease including genetic diseases (inherited) and
deficiency diseases (caused by malnutrition).
■■ Cholera, malaria, HIV/AIDS, tuberculosis (TB) and
measles are all examples of infectious diseases.
Smallpox was an infectious disease but was eradicated
in the late 20th century.
■■ Cholera is caused by the bacterium Vibrio cholerae and
is transmitted in water or food contaminated by the
faeces of infected people. Cholera can be controlled by
treating patients with intravenous or oral rehydration
therapy and making sure that human faeces do not
reach the water supply. The disease is prevented by
providing clean, chlorinated water and good sanitation.
■■ Malaria is caused by four species of Plasmodium. The
most dangerous is P. falciparum. Malaria is transmitted
by an insect vector: female Anopheles mosquitoes
transfer Plasmodium from infected to uninfected people.
Malaria is controlled in three main ways: by reducing the
number of mosquitoes through insecticide spraying or
draining breeding sites; by using mosquito nets (more
effective if soaked in insecticide); by using drugs to
prevent Plasmodium infecting people.
218
Cambridge International AS Level Biology
■■ AIDS is a set of diseases caused by the destruction
of the immune system by infection with human
immunodeficiency virus (HIV). HIV is transmitted in
certain body fluids: blood, semen, vaginal secretions
and breast milk. HIV primarily infects economically
active members of populations in developing countries
and has an extremely adverse effect on social and
economic development.
■■ The transmission of HIV can be controlled by using
barrier methods (e.g. condoms and femidoms) during
sexual intercourse. Educating people to practise safer
sex is the only control method currently available to
health authorities. Contact tracing is used to find people
who may have contracted HIV, so that they can be tested
and counselled.
■■ Life expectancy can be greatly extended by using
combinations of drugs which interfere with the
replication of HIV. However, such treatment is expensive,
is difficult to maintain and has unpleasant side-effects.
There is no vaccine for HIV and no cure for AIDS.
■■ TB is caused by the bacteria Mycobacterium tuberculosis
and M. bovis. M. tuberculosis is spread when people
infected with the active form of the disease release
bacteria in droplets of liquid when they cough or sneeze.
Transmission occurs when uninfected people inhale the
bacteria. This is most likely to happen where people live
in overcrowded conditions, and especially where many
sleep close together.
■■ Many people have the inactive form of TB in their lungs,
but they do not have the disease and do not spread it.
The inactive bacteria may become active in people who
are malnourished or who become infected with HIV. M.
bovis causes TB in cattle, but can be passed to humans.
Drugs are used to treat people with the active form
of TB. The treatment may take nine months or more
as it is difficult to kill the bacteria. Contact tracing is
used to find people who may have caught the disease.
These people are tested for TB and treated if found to
be infected. The BCG vaccine provides some protection
against TB, but its effectiveness varies in different parts
of the world.
■■ Measles is an extremely contagious disease caused
by a virus that inhabits the cells of the nasal cavity
and trachea. Infected people sneeze or cough out
droplets which contain millions of virus particles. If
these are inhaled by a person with no immunity, it
is almost certain that they will be infected with the
disease. Symptoms include fever and a rash. There is
no specific medicine for measles – treatment is rest and
medicine to reduce the fever. Measles is controlled in
economically developed countries by vaccination and
there are very few outbreaks of the disease, but is a
major disease in developing countries.
■■ Public health measures are taken to reduce the
transmission of all of these infectious diseases, but to be
effective they must be informed by a knowledge of the
life cycle of each pathogen.
■■ Antibiotics are drugs that are used to treat infections
caused by pathogenic bacteria. They are compounds
that are made by microorganisms and modified
chemically to increase their effectiveness. Penicillin
prevents the production of new cell walls in bacteria
and so does not affect viruses or human cells, neither
of which have cell walls. Not all antibiotics are effective
against all bacteria.
■■ Resistance to antibiotics can arise because some
bacteria may, by chance, contain a resistance gene. The
bacteria survive when exposed to the antibiotic and can
then reproduce to form a large population of bacteria all
containing this gene. This is called vertical transmission
of resistance. Resistance can also be spread between
bacteria by horizontal transmiss
Explain Diseases and immunity
Describe a pathogen as a disease-causing
organism
When harmful bacteria, viruses, prions, or viroids infect another organism, they become PATHOGENS, infectious organisms that can cause DISEASE . Pathogens can be deadly. They exist everywhere on Earth in various forms.
Describe a transmissible disease as a disease in
which the pathogen can be passed from one host
to another
State that a pathogen is transmitted:
(a) by direct contact, including through blood
and other body fluids
(b) indirectly, including from contaminated
surfaces, food, animals and air
Describe the body defences, limited to: skin,
hairs in the nose, mucus, stomach acid and white
blood cells
Explain the importance of the following in
controlling the spread of disease:
(a) a clean water supply
(b) hygienic food preparation
(c) good personal hygiene
(d) waste disposal
(e) sewage treatment (details of the stages of
sewage treatment are not required)
An infectious disease is a disease resulting from the presence of pathogens including viruses, bacteria, fungi, protozoa and multicellular parasites. These pathogens are able to cause disease in animals and/or plants.
Some disease affect us for short periods of time – common
cold measles, influenza
Others
are more chronic – TB, AIDs
- — Endemic: Describing a disease that is always present in a population
- — Incidence: The number of people diagnosed with a disease over a period of time
- — Prevalence: The number of people with the disease at any one time
- — Pandemic: An increase in number of cases throughout a continent or across the world
Infectious pathologies are usually contagious diseases due to their potentiality of transmission from one person or specie to another. Diseases can be transmitted in a variety of ways, from drinking contaminated water to sexual contact.
The four diseases you are required to know are relevant because they are the ones of current concern - they are all in epidemic or pandemic status. Due to international travel, diseases can be spread round the entire world very quickly, as in the SARS incident of 2002/2003. Some bacteria are growing resistant to the use of antibiotics, which used to be an effective way of stopping disease spreading.
Cholera
As Cholera is a water-borne disease, it occurs where people do not have access to proper sanitation, a clean water supply or uncontaminated food. The bacteria pass through the stomach (if the contents are sufficiently acidic (less than PH4.5) the bacteria is unlikely to survive) and reach the small intestine. Here they multiply and release a toxin know as choleragen, which disrupts the epithelium functions so that salts and water leave the blood.
This causes severe diarrhoea which leads to dehydration, and can be fatal within 24 hours. Fortunately, treatment for cholera is relatively simple; the disease can be controlled by giving a solution of salts and glucose intravenously to rehydrate the body (Oral Rehydration Therapy). There is a vaccine available for some strains of cholera, but it only provides short-term protection.
Strains
There are more than 60 different strains of the pathogen that causes cholera, and there have been 8 pandemics of cholera, mostly caused by untreated sewage water.
Features
| Pathogen | Vibro cholerae |
|---|---|
| Transmission method | food and water borne |
| Incubation | 1–5 days |
| Symptoms | Severe diarrhoea, loss of water and salts, dehydration. |
| Annual incidence/mortality worldwide | 5.5 million/ 120,000 |
Malaria
Infection stages
Take a look at the diagram , showing the infection cycle of malaria. Malaria is caused by Plasmodium parasites. The parasites are spread to people through the bites of infected female Anopheles mosquitoes.
There are four parasite species that cause malaria in humans:
1. Plasmodium falciparum
2. Plasmodium vivax
3. Plasmodium malariae
4. Plasmodium ovale.
Plasmodium falciparum and Plasmodium vivax are the most common. Plasmodium falciparum is the most deadly.
When a female mosquito stings a human (to take a blood meal), either of the following event may occur:
1.In case of an infected person, the mosquito obtains both male and female gametes of Plasmodium along the blood it sucks up. Then, the gametes fuse in the mosquito’s stomach, forming thousands of immature malarial parasites which invade the mosquito’s salivary glands.
2.The other event that could occur is that an already infected mosquito with immature malarial parasites, injects them into a healthy person. The immature malarial parasites then undergo maturation in the person's liver.
Obviously, the 2nd event then returns to the 1st event and eventually results in a transmission cycle.
Features
| Pathogen | Plasmodium |
|---|---|
| Transmission method | Insect vector |
| Incubation | 1 week - 1 year |
| Symptoms | Fever, nausea, headaches, sweating, spleen enlargement, muscle pain |
| Annual incidence/mortality worldwide | 300 million/1.5-3 million |
Control
There are 3 main ways of controlling the vector, and thus of controlling malaria;
- Avoid being bitten by mosquitoes, either by using insect repellent or mosquito nets.
- Reduce the number of mosquitoes, by destroying their breeding grounds, chemically (using a chemical that kills mosquito larvae) or physically (draining the water areas).
- Use drugs to prevent Plasmodium affecting people
- Draining swamps which serve as breeding sites for mosquitoes.
- Spreading oil on the ponds or swamps which prevents the larvae or pupa to breath, and eventually die.
Eradication program
Preventative drugs have been partially successful in breaking the transmission cycle - these drugs inhibit the parasite spreading in the body, some by inhibiting protein synthesis and some by stopping the sexual reproduction inside the mosquito.
Failures
- Many of the drugs used to treat it are now not working because malaria has built up a resistance
- Mosquitoes also became resistant to the insecticides used to treat it.
- The program was unpopular because due care towards indigenous people was not taken (at one point, teams spraying DDT were killed by villagers angry with them).
- When the disease was temporarily eradicated, people who had immunity lost it and when the disease returned (as the program was not successful) they suffered and some died as a result
Tuberculosis
Tuberculosis is an incredibly invasive disease - it starts with a primary infection in the lungs and quickly spreads to the lymph nodes, bones and gut. It often strikes HIV-positive people when their immune system begins to weaken.
It spreads via aerosol droplets and unpasteurised milk and is particularly prevalent in overcrowded areas. People suffering malnutrition are more susceptible. Infections have fallen now because of vaccine introduction in the 1950s. However it is estimated that 30% of the world's population is infected with TB without showing any symptoms of the infection; people with this inactive infection do not spread the disease to others.
Resistance
Tuberculosis is unfortunately showing a comeback, and this is thought to be due to a variety of factors.
These include;
- Breakdown in the tuberculosis vaccination and control program
- Poor housing causing overcrowding
- The AIDs epidemic weakening immune systems and allowing it to be more prevalent
- Some strains are now resistant to antibiotics
The last bullet point, about resistance, is particularly important. When antibiotics attack bacteria, any that are resistant to them survive, and thus multiply and possibly create a new strain of tuberculosis that is antibiotic resistant.
Features
| Pathogen | Mycobacterium tuberculosis, Mycobacterium bovis |
|---|---|
| Transmission method | airborne droplets |
| Incubation | 2–6 weeks |
| Symptoms | Coughing up blood, shortness of breath, fever, chest pain and sweating. |
| Annual incidence/mortality worldwide | 8 million/2 million |
Acquired Immune Deficiency Syndrome
Acquired Immune Deficiency Syndrome (AIDS), is a syndrome caused by the retrovirus Human Immunodeficiency Virus (HIV).
HIV
HIV pathogens infect and destroy the T helper cells of the immune system, and without these the immune system does not respond adequately to infection.
When T-Cell numbers are low, the body is particularly vulnerable to infection by anything from the common cold to tuberculosis. Thus, AIDS is not a disease, HIV is the virus that causes AIDS which is a syndrome. Affects the CD4 receptor cells.
Features
| Pathogen | Human immunodefieciency virus (HIV) |
|---|---|
| Transmission method | Exchange of body fluids (sexual intercourse, intravenous needle sharing, blood transfusions) |
| Incubation | HIV has a few weeks, but AIDs may not develop for up to ten years |
| Symptoms | HIV - fever and then none AIDs - hugely increased susceptibility to disease, such as pneumonia and TB. |
| Annual infected/new incidence/mortality worldwide | 33.4 million/6 million/2.5 million |
Treatment
HIV and subsequently AIDS cannot be cured, but the spread of AIDs can be slowed down with a variety of drugs, providing an increased life expectancy. This results in a virus that is difficult control, and is thus best prevented. People can be educated to use condoms and other means of reducing the risk of infection during intercourse.
Statistics
- 5.9 million children are estimated to have been orphaned by AIDs
- 25% of Zimbabwe is infected with HIV
- 34 million people are infected with HIV in sub-Saharan Africa.
Transmission and testing
Transmission is spread by intimate human contact and HIV cannot survive outside the body - transmission is only possible by direct bodily fluid exchange, most commonly during sexual intercourse, across the placenta and intravenous needle sharing. Testing is done via a blood test, but this only becomes available several days after the initial infection. This testing is offered to those who think they might have HIV, and they are often asked to contact sexual partners and inform them that they should get tested, as HIV caught early can be slowed down.
Pregnant women
HIV positive women in countries like the UK are advised to not breastfeed their children, since HIV can be transmitted this way as well since viral particles have been found in breast milk. However, third world countries have many more risks that breast-feeding negates that the risk of HIV is an acceptable one.
HIV positive women should take antiretroviral drugs (nevirapine) before delivery
Antibiotics
Antibiotics are selective toxins, killing or disabling the pathogen without harming the host. Only a few work on viral infections, and are derived from living organisms. Antibiotics are substances produced by the microbes to kill or retard the growth of other harmful microbes.
How they work
Antibiotics work against bacteria and viruses in the following ways;
- Synthesis of bacterial walls
- Plasma membrane function
- Protein synthesis
- Enzyme function
Resistance[edit]
Pathogens can develop resistance to antibiotics, by developing enzymes for destroying penicillin for example. An example of this is MRSA, which is a bacteria that is resistant to four of the most popular antibiotics due to their inappropriate use and people not finishing their course of antibiotics – leaving antibiotic resistant bacteria to grow and spread.
Chapter 10 Infectious Diseases
Infectious Diseases
1 MCQ: Tuberculosis (TB) is an example of
A. pandemic
B. prodemic
C. endemic
D. epidemic
2 MCQ: People who are infected with .....are likely to live their whole life
A. Acquired Immune Deficiency Syndrome (AIDS)
B. HIV
C. lungs cancer
D. All of above
3 MCQ: Vancomycin is
A. an infectious disease
B. is a virus
C. is an antibiotic
D. is an antiviral
4 MCQ: Oral rehydration therapy largely consists of water and
A. sodium ions
B. glucose
C. potassium magnate solution
D. All of above
5 MCQ: Annual worldwide incidence of cholera is
A. 1-2 million
B. 1-3 million
C. 1-5 million
D. 3 -5 million
6 MCQ: Which statement is incorrect? Effective antibiotics
A. show selective toxicity
B. kill host cell
C. kill pathogens
D. are useless against virus
7 MCQ: Childhood blindness can be caused due to
A. Acquired Immune Deficiency Syndrome (HIV/AIDS)
B. malaria
C. measles
D. tuberculosis
8 MCQ: Rice water is clinical name of
A. diarrhea
B. measles
C. Chronic Bronchitis
D. Emphysema
9 MCQ: Drug is ionized for treatment of
A. Cholera
B. Tuberculosis (TB)
C. measles
D. malaria
10 MCQ: Which strain is more virulent?
A. Classical strain
B. El Tor
C. V Cholerae 0139
D. All of above
11 MCQ: Total pandemics have been caused by Cholera virus
A. 5
B. 6
C. 7
D. 8
12 MCQ: Pathogen for Measles is known as
A. Variola Virus
B. Vibrio Cholerae
C. Plasmodium
D. Morbillivirus
13 MCQ: Infectious diseases include
A. malnutrition
B. cystic fibrosis
C. Retinoblastoma
D. Tuberculosis
14 MCQ: Variola virus has been known to cause
A. malaria
B. measles
C. smallpox
D. chickenpox
15 MCQ: Causes of cholera do not include
A. poor sanitation
B. unclean water
C. genetic disorder
D. infectious pathogens
16 MCQ: A sudden increase in number of people having disease is called as
A. pandemic
B. prodemic
C. endemic
D. epidemic
17 MCQ: Toxin choleragen causes
A. increase in pulmonary constrictions
B. salt and water leave blood
C. stomach lining gets disrupted
D. an increase in salt and water
18 MCQ: Bacteria are known to cause
A. Cholera
B. Acquired Immune Deficiency Syndrome (HIV/AIDS)
C. malaria
D. measles
19 MCQ: Incubation period of Vibrio cholerae has duration of
A. few hours to four days
B. two hours to five days
C. two hours to fifteen days
D. None of above
20 MCQ: Pathogens
A. are plant diseases
B. are not animal diseases
C. cause infectious diseases
D. are known to cause carcinogens
21 MCQ: Always present known disease is
A. pandemic
B. prodemic
C. endemic
D. epidemic
22 MCQ: Action site of cholera virus is
A. small intestine
B. large intestine
C. faeces of infected person
D. stomach
23 MCQ: Cholera can be fatal if it is not treated within
A. 12 hours
B. 24 hours
C. 36 hours
D. 48 hours
24 MCQ: Transmission cycle of cholera can be broken by
A. treating with medications
B. by destroying small intestine lining were cholera virus grows
C. by boiling all vegetables and fruits before consuming
D. chlorination of water
25 MCQ: Long term degenerative diseases are including
A. Coronary Heart Disease (CHD)
B. malnutrition
C. mental diseases
D. sickle cell anemia
26 MCQ: Protoctist are known to cause
A. Cholera
B. Acquired Immune Deficiency Syndrome (HIV/AIDS)
C. malaria
D. measles
27 MCQ: Number of people who have disease at any one time is refer to as
A. Incidence
B. Coincidence
C. Transmission cycle
D. Prevalence
28 MCQ: Vibrio cholerae bacterium can not survive if the
A. pH is below 4.5
B. pH is between 4.5 and 7
C. pH is between 7 and 11
D. pH is above 11
29 MCQ: Bacterial and fungal infections
A. are non-infectious diseases
B. can be cured by antibiotics
C. need to be helped through transmission cycle
D. None of above
30 MCQ: Vaccination is a major control measure for
A. infectious diseases
B. genetic diseases
C. long term degenerative diseases
D. deficiency diseases
31 MCQ: Function of Penicillinases is to
A. act as narrow spectrum antibiotic.
B. act as broad spectrum antibiotic.
C. resist and destroy penicillin.
D. destroy cross-links of peptidoglycan polymers in bacterial cell wall.
32 MCQ: Almost unknown disease in developed countries is
A. malaria
B. measles
C. smallpox
D. chickenpox
33 MCQ: A rapid increase in cases around world is called
A. pandemic
B. prodemic
C. endemic
D. epidemic
34 MCQ: In India, El Tor
strain of cholera replaced classical strain in a time period of
A. 2 to 14 days
B. 6 months
C. 12 months
D. 24 months
Answer D
35 MCQ: In Cholera, body can
be rehydrated
A. intravenously
B. orally
C. Both A and B
D. None of above
Answer C
36 MCQ: Viruses do not cause
A. Acquired Immune Deficiency Syndrome (HIV/AIDS)
B. small pox
C. measles
D. malaria
Answer D
37 MCQ: El Tor strain has
been replaced by
A. V Cholerae 0142
B. V Cholerae 0149
C. V Cholerae 0139
D. V Cholerae 0134
Answer C
38 MCQ: Bacteria are known to
cause
A. Acquired Immune Deficiency Syndrome (HIV/AIDS)
B. malaria
C. measles
D. tuberculosis
E.
39 MCQ: Methicillin Resistant
Staphylococcus Aureus (MRSA) is
A. an infectious disease
B. is a virus
C. is an antibiotic
D. is an antiviral
Answer A
40 MCQ: People who are
affected by an infection are called
A. translocators
B. pathogens
C. phagocytic individuals
D. carriers
41 MCQ: Which diseases can
be transmitted from infected to uninfected people?
A cholera and malaria
B lung cancer and tuberculosis
C measles and sickle cell anaemia
D sickle cell anaemia and smallpox
B lung cancer and tuberculosis
C measles and sickle cell anaemia
D sickle cell anaemia and smallpox
42 MCQ: Which row matches pathogens with the diseases they cause?
A
43 MCQ: How are the diseases cholera, malaria, TB and HIV/AIDS transmitted?
D
44 MCQ: Which treatment would not help villagers control the spread of malaria?
A
draining nearby marshes and covering water surfaces with oil
B stocking ponds and ditches with fish that eat insect larvae
C sleeping under nets treated with insecticide
D taking preventative drugs to which Plasmodium has developed resistance
B stocking ponds and ditches with fish that eat insect larvae
C sleeping under nets treated with insecticide
D taking preventative drugs to which Plasmodium has developed resistance
45 MCQ: Which measure would help control the spread of TB?
A preventing overcrowded conditions
B provision of clean water
C sewage treatment
D use of insecticides
B provision of clean water
C sewage treatment
D use of insecticides
46 MCQ: Which statements describe the transmission of human immunodeficiency
virus (HIV) from an infected to an uninfected person?
1 It is
transmitted by a vector.
2 It is transmitted by intimate human contact.
3 It is transmitted by sharing intravenous injection needles.
4 It is transmitted across the placenta from mother to fetus.
A 1, 2, 3 and 4
B 2, 3 and 4 only
C 1 and 3 only
D 3 and 4 only
2 It is transmitted by intimate human contact.
3 It is transmitted by sharing intravenous injection needles.
4 It is transmitted across the placenta from mother to fetus.
A 1, 2, 3 and 4
B 2, 3 and 4 only
C 1 and 3 only
D 3 and 4 only
47 MCQ: Which statements explain why injections of vaccine may not provide
protection against Vibrio
cholerae?
1 V. cholerae bacteria infect the intestine.
2 The toxin produced by V. cholerae acts within the intestine.
3 A vaccine providing protection against one strain of V. cholerae may not provide protection against another strain.
A 1, 2 and 3
B 1 and 2 only
C 2 and 3 only
D 3 only
48 MCQ: What explains why measles is not treated with an antibiotic?
A The pathogen causing measles can break down the antibiotic.
B The pathogen causing measles has become resistant to the antibiotic.
C The pathogen causing measles has no cellular structure.
D The pathogen causing measles is too large to be affected by an antibiotic.
MCQ: The malarial parasite must enter a red blood cell to divide and multiply. To enter, the parasite binds to a protein called basigin on the cell surface membrane of the red blood cell. What could prevent the parasite from entering a red blood cell?
A an antibiotic that inhibits the synthesis of bacterial cell walls
B an antiviral drug that prevents the parasite from multiplying
C a molecule which binds to basigin and blocks its binding site
D a molecule which binds to the cell surface membranes of mosquito cells
1 V. cholerae bacteria infect the intestine.
2 The toxin produced by V. cholerae acts within the intestine.
3 A vaccine providing protection against one strain of V. cholerae may not provide protection against another strain.
A 1, 2 and 3
B 1 and 2 only
C 2 and 3 only
D 3 only
48 MCQ: What explains why measles is not treated with an antibiotic?
A The pathogen causing measles can break down the antibiotic.
B The pathogen causing measles has become resistant to the antibiotic.
C The pathogen causing measles has no cellular structure.
D The pathogen causing measles is too large to be affected by an antibiotic.
MCQ: The malarial parasite must enter a red blood cell to divide and multiply. To enter, the parasite binds to a protein called basigin on the cell surface membrane of the red blood cell. What could prevent the parasite from entering a red blood cell?
A an antibiotic that inhibits the synthesis of bacterial cell walls
B an antiviral drug that prevents the parasite from multiplying
C a molecule which binds to basigin and blocks its binding site
D a molecule which binds to the cell surface membranes of mosquito cells
49 MCQ: Non-infectious diseases are best
defined as:
A diseases caused by malnutrition
B all diseases of old age
C all diseases that are not caused by a pathogen
D all diseases that can be transmitted from mother to child
A diseases caused by malnutrition
B all diseases of old age
C all diseases that are not caused by a pathogen
D all diseases that can be transmitted from mother to child
50 MCQ: An antibiotic sensitivity
test was carried out on bacteria isolated
from a patient with a blood disease.
Four antibiotics were tested, A, B, C and
D. The results are shown in the
figure.
Which antibiotic should be chosen to treat the blood disease?
Which antibiotic should be chosen to treat the blood disease?
51 MCQ: Which of the following
diseases is transmitted by an insect vector?
A cholera
B HIV/AIDS
C malaria
D TB
A cholera
B HIV/AIDS
C malaria
D TB
52 Rearrange
the order of the following statements to give a flow diagram showing the
evolution of resistance
to the antibiotic streptomycin by the bacterium Escherichia coli.
to the antibiotic streptomycin by the bacterium Escherichia coli.
1 Most of the population of E. coli is resistant to streptomycin.
2 A mutation in a DNA triplet of a plasmid, changing TTT to TTG, gives an E. coli bacterium resistance
to streptomycin.
3 The resistant bacterium divides and passes copies of the plasmid to its off spring.
4 Sensitive bacteria die in the presence of streptomycin as a selective agent.
5 The frequency of the mutated gene in the population increases.
6 The resistant bacterium has a selective advantage and survives.
53 a ) State three ways in which HIV is
transmitted. .
[3]
The table shows statistics for four regions of the world and the global totals for HIV/AIDS in 2010.
The table shows statistics for four regions of the world and the global totals for HIV/AIDS in 2010.
b Suggest
three sources of data that UNAIDS may use to compile the
data in the table. [3]
c Explain why it is important to collect the data on the HIV/AIDS pandemic shown in the table [3]
d i For North America, the ratio of the number of people dying from AIDS to the number of people living with HIV in 2010 was 20000:1.3 million or 0.015: 1.
Calculate the ratio for sub-Saharan Africa. [1]
ii Suggest reasons for the difference between the ratios for North America and sub-Saharan Africa. [3]
[Total: 13]
c Explain why it is important to collect the data on the HIV/AIDS pandemic shown in the table [3]
d i For North America, the ratio of the number of people dying from AIDS to the number of people living with HIV in 2010 was 20000:1.3 million or 0.015: 1.
Calculate the ratio for sub-Saharan Africa. [1]
ii Suggest reasons for the difference between the ratios for North America and sub-Saharan Africa. [3]
[Total: 13]
54 a Describe how malaria is
transmitted.
The
figure shows the global distribution of malaria
in 2010.
c Outline the biological reasons for the difficulties in developing and introducing control methods for malaria. [6]
[Total: 14]
55 a Describe
how cholera is transmitted.
[2] The table
shows the number of cases of cholera
and deaths from the disease for the
five countries with the
greatest outbreaks as reported to the WHO in 2010.
b With
reference to the table:
i calculate
the case fatality rate for Haiti in
2010
[1]
ii
suggest why the case fatality rate
varies between countries
[3]
iii explain
why it is important that the WHO collects
data on outbreaks of cholera. [3]
c
The WHO also collects data on
'imported' cases of cholera. Among countries
reporting these cases in 2010 were Australia,
Malaysia and the USA.
i
Suggest what is meant by the term 'imported
case'.
[1]
ii
Explain why there are no epidemics
of cholera in highly economically developed
countries
such as Australia and the USA.
[2]
[Total: 12]
56 a i Name the causative
organism of TB.
[1]
ii Explain
how TB is transmitted.
[2]
b i State the regions of the
world with the highest number of
cases of TB. [3]
ii Suggest reasons for the high number of cases of TB
in some parts of the world. [4]
[Total: 10]
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