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Types of Pathogens and Diseases

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Pathogens and Disease

TAQ 1

Pathogen is known as a microorganism that may cause disease to its host. Bacteria, viruses, fungi and protozoa are all microorganisms that cause disease.

1.2

Features

Virus

Bacteria

Fungus

Protozoa

shape

A typical bacterial cell

structure

Core which contains the DNA or RNA and coat of protein. Made up of short strands of DNA or RNA called Genome

Cell wall, bacterial (chromosomal) DNA, Plasmid (DNA), Flagellum. DNA contained in one long strand in two forms chromosome and plasmid

Protein coat which attaches and penetrates the host cell, genetic material. Contain a membrane-bound nucleus where there DNA is wrapped round the histone proteins.

Cell membrane, nucleus, cytoplasm and vacuole

Reproduction

Viruses are classed as not living as they aren’t made of cells and cannot produce they can only reproduce in a host cell.

Living things known as prokaryotes and classed as living and can cause disease to all living things, once they are the correct conditions they multiply quickly.

Fungi is a spore producing organism that can live as singled cell or a multi-cellular mould and reproduces by spores and absorbs nutrients

A singled cell organism and can live independently or be parasites and produces by binary fission which is an asexual mode.

Nutrients

Require to be inside another organisms cells

Some live off of other organisms, and others get their energy from photosynthesis

Obtains their nutrients from their surroundings

Breaks down organic matter and can produce both aerobic and anaerobic environments

Size

20-400 nanometres in diameter

0.2 - 1 micrometer in diameter

up to 1mm

5 – 500 micrometers

Functions

Replicate and cause disease in animals and plants

Guard cells against osmotic shock and physical damage, contains genome, bacterial mating, contains genetic information that can resist antibiotics, production of toxins, takes part in protein synthesis, moves cells.

Recycles the dead plants in the soil to be reused, excellent for plant growth. Fungi also a type of food for humans and some medicine is made from fungus.

Digestion by means of enzymes

respiration by the diffusion of dissolved gasses through cell membrane

reproduction through asexual by cell division of binary fission

(Word count 329)

Diagram References

Tony Crowther | MRC Laboratory of Molecular Biology. 2014. Tony Crowther | MRC Laboratory of Molecular Biology. [ONLINE] Available at: http://www2.mrc-lmb.cam.ac.uk/group-leaders/emeritus/tony-crowther/. [Accessed 12 August 2014].

Microbiology Online | Society for General Microbiology | About Microbiology - Introducing microbes - Bacteria. 2014. Microbiology Online | Society for General Microbiology | About Microbiology - Introducing microbes - Bacteria. [ONLINE] Available at: http://www.microbiologyonline.org.uk/about-microbiology/introducing-microbes/bacteria. [Accessed 12 August 2014].

Microbiology Online | Society for General Microbiology | About Microbiology - Introducing microbes - Protozoa. 2014. Microbiology Online | Society for General Microbiology | About Microbiology - Introducing microbes - Protozoa. [ONLINE] Available at: http://www.microbiologyonline.org.uk/about-microbiology/introducing-microbes/protozoa. [Accessed 12 August 2014].

TAQ 2 - Factsheets

Cholera - Acute diarrhoea disease

Cholera transmission can be associated to insufficient environmental management. Living in situations where there is poor sanitation and no clean water available contributes to higher risk of contracting cholera. It is spread when a person consumes fluid or food contaminated by faeces from an infected person.

Cholera has 2 life cycles, one in the environment and one in humans. Within the environment cholera attaches themselves to tiny crustaceans called copepods. The cholera travels naturally in coastal waters with their hosts as the crustaceans follow their food source; algae and plankton. Algae grow with the water temperatures by urea in sewage. Within humans, the bacterium is ingested, bacteria is then passed in their stool. When the faeces come into contact with fluid or food the bacteria breeds very quickly. The most common source of cholera infection is water, seafood, raw fruit and vegetables and grains of rice and millet.

Treatment – Oral salts rehydration and may require IV fluids in serious cases, antibiotics are required, prompt access to treatment should an outbreak happen. There is also a vaccination if a person is travelling to a country where cholera is more common. Prevention is the provision of safe drinking water and correct sanitation, safe food handling, clean and not overcrowded living conditions.

Athlete’s Foot – fungal infection of the foot

Fungal infection that lives naturally on the skin of the foot, should the organisms reproduce the skin may become infected. Dermatophytes; the fungi to blame and lives in and feeds off of deceased skin. The ideal conditions for the fungi to live and breed is warm, dark and humid, the human foot is perfect. They eat the dead cells and produce in the way of spores and can live for a long time. Athlete’s foot uses acid proteases, elastases and keratinases to attack the epidermis of the foot. The rate in which is grows depends on the nutrients available.

Athlete’s foot can breed in places such as swimming pools, changing rooms and showers and can be spread by direct contact.

Prevention – good foot hygiene, washing feet regularly with soap and water and drying properly. Clean socks and shoes and not sharing towels with others. Not walking bare foot in public places.

Treatment with an antifungal medication, if untreated the fungus can spread to other areas of the body and even enter the body if the skin is cracked and therefore leads to a more serious infection.

Malaria

Transmitted by the bite of a female mosquito and can be life threatening. Caused by the parasite plasmodium this enters the bloodstream.

The female mosquito bites the human, parasites grow in the liver cells first and then in the red blood cells. Successive broods grown and obliterate red blood cells and release daughter parasites (merosoites) that maintain with the attack of red blood cells. The blood stage makes the person feel unwell; the parasites (gametocytes) are selected up by a female Anopheles mosquito in a blood meal and start an additional different cycle of growth and reproduction in the mosquito. After 10 days the parasite (sporozoites) is in the mosquito salivary glands. The Anopheles has a blood meal on another human; the sporozoites are injected with the mosquito’s saliva and infect the human. The mosquito carries the disease from one person to another person acting as a vector, the host being the human.

Anti-malarial tables can be used for treatment and prevention. Depending on the type of malaria will depend on the length of treatment.

Malaria can be prevented by knowing an awareness of people travelling to countries where malaria is high. If travelling, use insect repellent, and take anti-malaria tablets. After visiting certain countries and feel poorly on returning, seek medical attention straight away.

Influenza

Is a common infection’s viral disease spread through small droplets of fluid coughed or sneezed into the atmosphere by an infected person and can travel about a metre. The flu can also be spread through touch person to person or on hard surfaces.

Influenza is an RNA virus which belongs to the “enveloped” viruses group. The virus is made of 8 separate pieces of RNA which allow different flu viruses to easily mate to form a hybrid progeny virus. The influenza virus works by invading living cells and growing in them. It produces thousands of virus particles and infects other cells. Hemagglutinin lets the virus infect the epithelial cells of the upper respiratory tract, its fuses the cell membrane with the membrane of the virus allowing the RNA of the virus to infect other cells. Once the viral duplication happens, the progeny virons are free from the cell and the cell then repeats the cell cycle of infection.

The flu can be prevented with good personal hand hygiene, regularly washing surfaces, and using tissues to cough into or sneeze and disposing of them correctly. There is also a free flu vaccine on the NHS for certain categories of people.

(Word count 823)

 

TAQ 4

How does the body defend itself against pathogens which cause infectious diseases?

The body has many ways of defending itself from pathogens which can cause infectious diseases, but there are times when the body can’t fight such diseases and requires a little medical intervention with antibiotics. From the immune system which a person is born with to how the body works together to fight infection and repairs itself or immunisation from infectious diseases, the body’s immune system is crucial for the survival against serious and dangerous infections which could potentially be life threatening.

Every person is born with an immune system passed through the placenta from their mother, this is called the innate immunity, which is inherited and will be used in the body regularly throughout the lifetime. Although contact with a pathogen is not necessary, T cells protects the person from diseases of other organisms. The innate immunity involves elimination of pathogens externally or internally.

The physical lines of protection of infections are the skin, chemicals in the body’s tears and sweat, and stomach acid. The whole body is covered in skin, and although the skin has many roles, it plays a vast part in not letting microbes to infiltrate the skins dry and lifeless surface cells. The skin also produces various chemical weapons like sweat so pathogens cannot enter, also pathogens can easily be washed off of the skin or even flake off. The other potential routes are the openings in the body, the digestive and respiratory tract and the urinary tract. The saliva’s lysozyme enzyme that destroys bacteria that may try to enter via the mouth and earwax catches and kills microbes in the ears. The acid in the urine is constantly washing bacteria away from the urinary tract and protecting it from bacteria. Eyes protect themselves with lysozyme which breaks down the bacterial wall. Should a pathogen manage to enter the system, the body is so clever in using its defence mechanisms to get rid of the pathogen either with vomiting, coughing or sneezing and diarrhoea.

Active and passive immunity are major immunities to the body. Passive is antibiotics given outside the body via vaccine and stimulates a primary response against the antigen and active immunity is when the person becomes open to the elements of the pathogen and becomes immune as a consequence of the primary immune response.

The second line in the body’s defence is the non-specific immunity and the specific immunity. The non specific immunity is also called innate immunity and begins to work on a pathogen within 12 hours. It is made up of cells and proteins that are ready and waiting to be mobilised and fight the pathogens at the site of the infection. The main components are the epithelial barriers, phagocytes, dendritic cells, NK Cell and plasma proteins. Some white blood cells (phagocytes) fight the pathogens that break the outer barrier; a phagocyte encages the pathogen and destroys it. The specific immunity also known as the adaptive immunity springs into battle against pathogens cannot be destroyed by the non-specific immunity. It works to the function of phagocytes and the elements of the non specific immunity. It makes a targeted response against a precise pathogen. Lymphocytes are important to the specific immunity, produced in the bone marrow and have numerous subtypes, T & B cells being most familiar. An antigen sparks a reaction from T & B cells, they work together and fit any shape required. The T cells supply the signal to B cells to begin growing and distinguish into plasma cells, this then produces the protein called antibody. These antibodies fight the antigens in the blood system. Some T Cells are known as killer cells and can stimulate cytotoxic T cells and can directly attack specific cells carrying unusual molecules or MHC molecules. They are also useful for attacking viruses. Memory cells are made from T cells and have learned to overcome a pathogen by remembering how the pathogen was destroyed the first time. The immunity becomes stronger after each exposure of a pathogen that has been successfully destroyed. The skill to learn and destroy is exploited during the procedure of vaccination.

The body has two responses to infection, primary and secondary infections. The primary infection is the initial original small dose of the virus to the normal host. This first blow can be minimal and may possibly lower the immune system. The first infection has made the person more susceptible to secondary infections and these occur after or through the primary infection and can occasionally be known as opportunistic infections. The secondary infection can possibly be resolved when the original pathogen is treated.

The body is very clever in fighting infections and viruses that can be harmful and cause illness. The immune system every person is born with stays within the body for the lifetime, along with the acquired and active immunity, pathogens are destroyed. Sometimes this cannot happen and the body is not strong enough, that’s where medical intervention is required; the passive immunity kicks in and destroys the pathogen. This type of antibody only lasts a few days, so then the body’s immunity steps back up again and keeps the body free from diseases and viruses.

(Word count 858)

TAQ 5

Immunity

Natural

Acquired

Similarities and Differences

* Present in the body from birth

* The immunity lasts a life time

* Contact with the pathogen isn’t essential

* Protects from contraction of diseases from other organisms

*

* Develops during the life time

* Very short lifespan

* Contact with pathogen is crucial

* Protects from pathogens

* In attendance on other members of the matching species

Immunity

Active

Passive

 

Similarities and Differences

* Direct contact with pathogen or its antigen is necessary

* requires to be initiated before it can be produced from the immune system

* A time period is compulsory for immunity development, can take a couple of days

* Antibodies are made in the body in reaction to pathogen or antibody

* It lasts for a long period of time

* Immunologic memory may consequence in life long immunity

* Not much side effects

* No direct contact with antigen is required. Antibiotics are injected from outside the body and are ready made with antibodies.

* Immunity develops immediately

* Antibiotics are injected

* The immunity lasts a few days

 

Both prepare the body to fight infection and diseases and for a lifetime.

(Word count 182)

References

Malaria - NHS Choices. 2014. Malaria - NHS Choices. [ONLINE] Available at: http://www.nhs.uk/Conditions/malaria/Pages/Introduction.aspx. [Accessed 13 August 2014].

WHO | Immunization. 2014. WHO | Immunization. [ONLINE] Available at: http://www.who.int/topics/immunization/en/. [Accessed 13 August 2014].

Natural passive immunity - definition from Biology-Online.org. 2014. Natural passive immunity - definition from Biology-Online.org. [ONLINE] Available at: http://www.biology-online.org/dictionary/Natural_passive_immunity. [Accessed 14 August 2014].

Viruses: Structure, Function, and Uses - Molecular Cell Biology - NCBI Bookshelf. 2014. Viruses: Structure, Function, and Uses - Molecular Cell Biology - NCBI Bookshelf. [ONLINE] Available at: http://www.ncbi.nlm.nih.gov/books/NBK21523/. [Accessed 14 August 2014].

Clostridium Difficile | Health | Patient.co.uk. 2014. Clostridium Difficile | Health | Patient.co.uk. [ONLINE] Available at: http://www.patient.co.uk/health/clostridium-difficile-leaflet. [Accessed 21 August 2014].

Infectious diseases: pathogens - ABPI - Resources for Schools. 2014. Infectious diseases: pathogens - ABPI - Resources for Schools. [ONLINE] Available at: http://www.abpischools.org.uk/page/modules/infectiousdiseases_pathogens/index.cfm. [Accessed 21 August 2014].

  • Ashley Wilcock

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