Communicable Diseases (AQA GCSE Biology: Combined Science)

Read the following information about lungworm:

Foxes can be infected by a parasitic lungworm. The life cycle of the lungworm includes an adult stage, during which the lungworm reproduces in the fox and infects its lungs. The larvae (young stages of the worm) end up in the digestive system of infected foxes. Lungworm is spread through the faeces of infected foxes.

Slugs can pick up these larvae. If a fox comes into contact with a slug that carries lungworm larvae, it can become infected. 

Name the role of the slug in the spread of lungworm.

Give one way in which the spread of lungworm can be prevented.

Explain why it is not possible to use antibiotics to treat a fox infected with lungworm. 

Malaria is a disease characterised by a recurrent fever. Female mosquitoes are responsible for spreading the pathogen that causes malaria as they feed on blood, whereas males do not. 

Describe two ways in which the spread of malaria can be reduced. 

A biotechnology company has created male, genetically modified (GM) mosquitoes that carry a bacterial gene.

The bacterial gene affects the growth of mosquito larvae.

Larvae with this gene die before they reach adulthood.

Evaluate whether the scientists should release these GM mosquitoes into the wild. 

The immune system aims to destroy pathogens such as bacteria and viruses if they manage to enter the body and infect organs and tissues.

Pathogens make us feel unwell.

Give one reason why this is the case.

Outline the possible responses of white blood cells to infection caused by pathogens.

The measles virus can cause serious illness in humans. 

Vaccination can protect individuals and populations from diseases such as measles.

Explain how the measles vaccine works to prevent disease.

The measles vaccine will not give a child immunity against the influenza virus.

Explain why.

Parents are encouraged strongly by healthcare professionals to vaccinate their children.

In recent years, there has been a growing movement of parents who are not having their children vaccinated for diseases such as measles. These parents cite concerns about the side effects of vaccines. 

What might be a consequence of a reduction in the number of children who are vaccinated for measles?

Explain your answer. 

Many diseases can be cured with antibiotics and others can be prevented with vaccinations.

Explain why antibiotics should not be prescribed by doctors to individuals with a known viral disease. 

Immunisation against a particular disease is possible when a person is injected with a weakened or inactive form of the pathogen. 

Explain how this confers immunity to a disease. 

Scientists are continually developing new drugs and medicines. These must be trialled before they can be prescribed to patients.

Before clinical trials can begin, drugs are tested in the laboratory.

The laboratory trials are not trials on people. 

What are drugs tested on before they are tested on patients?

Drugs must be tested extensively before they can be prescribed routinely to patients.

Explain why.

Between 2013 and 2016, the Ebola virus was responsible for around 12 000 deaths.

Almost all of the victims were in Western Africa.

There is currently no clinically approved medicine available to treat individuals infected with the Ebola virus. 

Drug companies have developed a new drug to treat Ebola.

Describe the stages of testing this new drug must go through before it can be used on patients. 

How are new drug compounds discovered?

A potential vaccine for Ebola began development in 2003.

In 2014, the World Health Organisation ruled that it would approve the vaccine for use on individuals recently infected with Ebola.

At that time the vaccine had not yet been tested on humans.

Suggest two reasons reason why the World Health Organisation deemed it ethical to use the vaccine on infected individuals despite it not having been tested on humans.

Influenza viruses are responsible for causing 'the 'flu' in many different vertebrate species, including humans.

How do viruses cause illness?

An American TV crew visited a remote tribe in the Brazilian rainforest to make a documentary. 

Two weeks after the crew's visit, six members of the tribe died and many more were seriously ill.

The members of the TV crew did not show symptoms of influenza during their visit, but members of the remote tribe died from the disease.

Suggest an explanation for this. 

The Center for Disease Control and Prevention estimated that 3.55 × 10⁷ individuals were infected with influenza in the United States during the 2018-19 'flu season. 

Of those individuals affected, an estimated 3.42 × 10⁴ died, sadly.

Based on these estimated figures, what percentage of people infected with influenza died from the disease during the 2018-19 'flu season?

Show your answer to 2 decimal places and show your working.

Ignaz Semmelweis was a doctor in Vienna in 1846.

It was his job to oversee the treatment of women during childbirth in two maternity clinics at the Vienna General Hospital. 

It was very common in those days for women to die shortly after childbirth from a condition known as 'puerperal fever', which we now know to have frequently been caused by infection with the pathogenic bacteria Streptococcus pyogenes.

How do pathogenic bacteria negatively affect the body after the first infection?

Table 1 shows the number of births and deaths in the two clinics between 1841 and 1846. 

Table 1

Calculate the percentage death rate in the first clinic during the year 1843. 

In the middle of the 19th century, Ignaz Semmelweis, a doctor in Hungary, noticed that the first clinic had a much higher average death rate in comparison to the second clinic. 

He did some investigations and found that, in the first clinic, the doctors were learning anatomy through the dissection of dead bodies, often moving straight onto delivering babies immediately after. He hypothesised that there were "particles" on their hands that were being transferred to the patients from the dissection. 

He asked the doctors to wash their hands before delivering babies in the maternity unit to see if it made a difference to the number of mothers dying from 'puerperal fever'.

Figure 1 shows the death rate in the first clinic during the years 1846-1848.

Figure 1

Describe how introducing the handwashing policy affected the death rate from 'puerperal fever'.

At the time of Semmelweis' research, bacteria had not yet been discovered.

Given our modern-day knowledge of pathogens and their methods of spread, suggest two other strategies doctors should carry out in order to avoid infecting their patients. 

In order to feed the growing human population, farming practice has changed in recent years to be much more intensive. 

Animals are often kept in small barns with hundreds of other animals in close proximity. 

This has led to a rise in the number of farm animals suffering from diseases caused by pathogens. 

Explain why. 

To prevent the spread of these pathogens some farmers give antibiotics to their livestock even when they are not sick. This has increased antibiotic resistance in animal pathogens.

Explain how this has occurred.

In order to counteract this issue an organisation called "Responsible Use of Medicines in Agriculture" (RUMA) was set up in 1997. 

In 2019 RUMA made the announcement that the sale of veterinary antibiotics for use in food-producing animals was down 53% between 2014 and 2018.

In 2014 62.5 mg/kg veterinary antibiotics were sold for use in food-producing animals.

Calculate the mass of antibiotics that were sold in 2018.

Give your answer in mg/kg.

In 2022 there was a large outbreak of avian influenza in the UK, which is sometimes referred to a bird flu. 

Explain why the overuse of antibiotics was not related to this recent outbreak. 

Table 2 shows information about the number of deaths from malaria in a particular area of Africa. 

Table 2

Year	Number of deaths from malaria per 100 000 people
2005	159
2007	136
2009	114
2011	97
2013	94
2015	92

Complete Figure 2 using data from Table 2.

Figure 2

Malaria is a disease that is spread through the bite of female Anopheles mosquitoes. 

What is the name used to describe the role of the mosquito in this process? 

The mosquito is effective at infecting humans with the malaria pathogen because it is able to bypass the non-specific defence of the skin. 

Describe the how the skin acts as a non-specific defence against pathogens. 

Describe how the human body defends itself against pathogens in the blood. 

When someone is suffering from an infection it is possible for them to take painkillers and antibiotics at the same time.

Compare the mechanism of action of painkillers and antibiotics.

A trial was carried out to test the efficacy of a new type of painkiller drug. 

This is the method used.

1. Participants were asked to take a drug.
2. Half an hour later they were poked with a blunt needle.
3. They were asked to rate their pain on a scale of 0 - 5, with 0 being no pain at all and 5 being extreme pain.

It was a double-blind trial.

Of the 40 participants, 20 took the painkiller and 20 took a placebo. 

Table 3 shows the findings from the trial. 

Table 3

	Painkiller drug	Placebo
Average pain rating (scale from 0 - 5)	2.4	4.1

The researcher concluded:

"The painkiller stops people feeling pain". 

Give one piece of evidence that supports their statement. 

The researcher concluded:

"The painkiller stops people feeling pain". 

Suggest two reasons why the statement may not be valid. 

As well as efficacy, what else needs to be established before a new drug can be approved for use?

Pathogens such as measles and Covid-19 are spread through sneezes and coughs which travel through the air. 

Give the correct term for this method of spreading an infection.

The chance of dying from measles and Covid-19 can be reduced by getting vaccinated. 

When a vaccine enters the body, the body responds by producing antibodies. 

Explain why. 

Complete the graph in Figure 3 to show how the number of antibodies changes when a vaccinated person becomes infected with a live pathogen. 

After a lot of people were vaccinated against Covid-19, a new variant of the virus emerged that had different shaped antigens to the first version of the virus. 

This caused the vaccine to be less effective against the virus.

Why would having different shaped antigens cause the vaccine to be less effective against the virus?