4.1.1 immune system

Question 1

direct transmission

Answer 1

transmission that occurs through physical contact

Question 2

indirect transmission

Answer 2

transmission that occurs due to indirect contact such as with a vector

Question 3

tuberculosis

Answer 3

Tuberculosis is an infectious disease of the lungs, caused by bacteria. Without treatment, it can become very serious and potentially fatal.

Question 4

TB; Pathogen

Answer 4

Human tuberculosis is caused by Mycobacterium tuberculosis.

Tuberculosis in cattle is caused by Mycobacterium bovis, but this can also affect humans.

Question 5

TB; Treatment

Answer 5

Tuberculosis can be treated using antibiotics.

Vaccinations, such as the BCG vaccine, are available for some strains of tuberculosis, but not all of these are routine childhood vaccinations in the UK.

Question 6

TB; Transmission and Prevention

Answer 6

Tuberculosis is spread when infected droplets from the lungs are coughed into the air and breathed in by others.

Transmission can be prevented by using tissues when coughing or sneezing and having good handwashing practice.

Question 7

Meningitis

Answer 7

Bacterial meningitis results in the inflammation of the membranes surrounding the brain and spinal cord and is a very serious disease. Without treatment, it can result in sepsis and death.

Question 8

M: Pathogen

Answer 8

Bacterial meningitis can be caused by many different pathogenic bacteria, such as:

Neisseria meningitidis A, B, C, W, X, Y and Z.

Streptococcus pneumoniae.

Haemophilus influenzae type B (HIb).

Question 9

M: Treatment

Answer 9

As with most bacterial diseases, treatment is with antibiotics

Question 10

M: Transmission and Prevention

Answer 10

Transmission of bacterial meningitis is via direct contact.

Vaccinations are available to help prevent infection and spread of the disease.

Question 11

Ring Rot

Answer 11

Ring rot is a bacterial disease affecting potatoes and tomatoes in cool regions of Northern and Eastern Europe. With its devastating effects on agriculture, some fear it may soon be seen in the UK.

Question 12

RR: Pathogen

Answer 12

Ring rot is caused by:

Clavibacter michiganensis, subspecies sepedonicus in potatoes.

Clavibacter michiganensis, subspecies michiganensis in tomatoes.

In tomatoes, the disease is sometimes known as ‘bird’s eye’.

Question 13

RR: Transmission and Control

Answer 13

Transmission of ring rot is through planting infected material and indirect contact with contaminated equipment.

Control can be improved through rigorous cleaning of agricultural equipment.

Some insect vectors can also spread the bacteria causing ring rot.

Question 14

HIV/AIDS

Answer 14

As a viral disease, HIV/AIDS cannot be treated with antibiotics as the virus uses the cells of the host for replication.

Question 15

HIV/AIDS: Pathogen

Answer 15

Human Immunodeficiency Virus (HIV) is the virus which causes the infection known as HIV.

HIV attacks CD-4 cells of the human immune system, so that infections become progressively more difficult to fight.

Without treatment, HIV sufferers may develop Acquired Immunodeficiency Syndrome (AIDS), which is a life-threatening condition.

Question 16

HIV/AIDS: Treatment

Answer 16

Antiretroviral drugs are used to prevent the multiplication of the virus inside the body, but so far there is no cure for the disease.

Question 17

HIV/AIDS: Transmission and Prevention

Answer 17

Transmission of HIV is via direct contact with infected bodily fluids, such as blood, semen, vaginal secretions, and breast milk.

With no vaccine currently available, prevention relies on:

Promoting awareness of risks and how to reduce them.

By using condoms during sex, getting tested regularly and not sharing needles.

Identifying infection early.

This process includes screening donated blood.

Question 18

Influenza

Answer 18

Influenza is a viral disease caused by different strains of virus which vary in symptom severity but can cause serious outbreaks of flu each year.

Question 19

I: Pathogen

Answer 19

Influenza is caused by the influenza viruses A, B and C.

Influenza viruses mutate very frequently, giving rise to strains that are difficult for the immune system to recognise and produce vaccinations against.

Mutations mean that viruses which previously only infected animals can jump the species barrier to also infect humans, becoming zoonotic.

Question 20

I: Treatment

Answer 20

Treatment for influenza is with antiviral drugs.

Annual vaccination programmes are carried out for humans most at risk of contact with strains judged most likely to cause outbreaks in that year.

Question 21

I: Transmission and Prevention

Answer 21

Influenza can be spread through both direct and indirect contact.

In humans, good hygiene and handwashing practice, as well as using tissues for coughing and sneezing can help prevent the spread of influenza.

In agriculture, restricting the movement of farm animals can prevent transmission of influenza from wild animals outside.

Question 22

Tobacco Mosaic Virus

Answer 22

Tobacco mosaic disease is a viral disease affecting tobacco plants and tomatoes, among other plants.

Question 23

TMV: Pathogen

Answer 23

Tobacco mosaic disease is caused by the tobacco mosaic virus.

This was the first virus to be discovered and has been widely studied for years to gain insights into how viruses infect hosts.

Question 24

TMV: Treatment

Answer 24

The virus can survive for 50 years in infected material, making treatment of the disease very difficult.

There is currently no known fully effective chemical control.

Question 25

TMV: Transmission

Answer 25

Transmission happens directly between infected plants, as well as indirectly between contaminated soil, equipment and people. The virus can contaminate seed coats, also leading to infection of the developing plant.

Question 26

TMV: Control

Answer 26

Control of tobacco mosaic virus is achieved through removing and burning infected plant material and discarding infected soil. Thorough washing and bleaching of equipment, and avoiding touching plants when watering helps reduce cross-contamination. Inoculating young plants with less serious strains can help prevent infection later on.

Question 27

Malaria

Answer 27

Malaria is a disease caused by Protoctista, resulting in cyclical symptoms of fever, chills and ultimately death if left untreated. The parasite can also use birds, bats and other animals as hosts.

Question 28

Ma: Pathogen

Answer 28

Malaria is caused by several species of the Plasmodium genus. P. falciparum causes the most malarial deaths worldwide. P. vivax, P. ovale, P. malariae and P. knowlesi are much rarer, but P. vivax can remain in the liver for years without causing symptoms. The parasite grows and multiplies in erythrocytes, causing them to burst every 2-3 days, releasing Plasmodium into the bloodstream.

Question 29

Ma: Treatment

Answer 29

Malaria is treated using antimalarial medication such as Doxycycline and Mefloquine. A preventative course of this medication should be taken prior to travel to known high-risk regions - this can reduce the risk of malaria by up to 90%. Different antimalarial medication can be used to treat the disease if the preventative course does not work.

Question 30

Ma: Transmission

Answer 30

Malaria is transmitted by insect vectors, specifically the female Anopheles mosquito when it takes a blood meal from an infected person. Malaria is most common in Africa, Asia and South America because the climate is suitably warm for the mosquito to live in and the probability of biting an infected person is higher.

Question 31

Ma: Prevention

Answer 31

Removing the insect vector is 100% effective in preventing transmission, although this is not always practical on a large scale. Sleeping under mosquito nets, applying insect repellent and covering exposed skin help reduce the risk of being bitten in the first place.

Question 32

Late Blight

Answer 32

Late Blight is a disease caused by Protoctista that affects potatoes and tomatoes, which resulted in the Irish Potato Famine in 1845.

Question 33

LB: Pathogen

Answer 33

Late blight is caused by Phytopthora infestans. The Protoctista cause spores to develop on the leaves of infected plants and germ tubes to grow through the leaf epidermis. Wounds, eyes and lenticels on tubers also allow infection.

Question 34

LB: Treatment

Answer 34

Fungicides are most commonly used, although resistance to some fungicides has developed. Individual plants are unlikely to survive once they are infected, sometimes dying within a week.

Question 35

LB: Transmission and Control

Answer 35

Sporangia (spores) can be airborne or waterborne, infecting soil and plants. Spores can encyst if the conditions are too cold and develop only when temperatures are above 15oC. Developing blight-resistant cultivars helps to reduce susceptibility of plants to the pathogen and control its spread. Forecasting when weather conditions may promote transmission means that fungicides can be sprayed at optimal times.