6.3 Defense against the Dark Arts (disease)

Or how our bodies stop being taken over by viruses, fungi and bacteria

And the cause, transmission and effects of HIV and AIDS

Pathogen : an organism or virus that causes a disease.The most common pathogens that affect humans are normally:

VirusesBacteriaFungiProtozoa

A pathogen

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Viruses – very simple ‘organisms’ made up of a protein coat surrounding a stretch of DNA or RNA.

They hijack the cells that they invade and use the host cell’s metabolism to make lots of copies of themselves.

A t-bacteriophage http://www.armageddononline.org/image/virus2.JPG

Influenza Virushttp://www.drugdevelopment-technology.com/projects/t705/images/1-influenza-virus.jpg

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Bacteria

Bacteria have many varied but relatively simple metabolisms. Some release enzymes that digest eukaryote cells, some just live in the ideal wet and warm conditions that are found in our bodies.

http://www.topnews.in/files/bacteria-4512.png

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Fungi

http://www.yellow-toe-nails.com/wp-content/uploads/2011/06/fungal_nail_infection.jpg

http://www.foothealthcare.com/shop/images/articles/editor/af1.jpg

http://doctorexclusive.com/wp-content/uploads/2011/02/Fungal-Infections.jpg

http://amazingdata.com/mediadata20/Image/interesting_nifty_funny_amazing_athletes_foot_danger_smelly200907241410422222.jpg

http://www.healthcentral.com/common/images/1/17141_13962_5.jpg

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Protozoa

http://library.thinkquest.org/06aug/01942/protists/mosquito.jpg

http://upload.wikimedia.org/wikipedia/commons/d/db/Symptoms_of_Malaria.png

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Protozoa are single celled eukaryotic organisms (Protists). Protozoan pathogens may live in the blood stream or gut

Antibiotics are effective against bacteria but not against viruses.

Antibiotics block specific metabolic pathways found in bacteria. Viruses reproduce using the host cell’s metabolic pathways, which are not affected by antibiotics.

http://www.antibioticsandalcohol.org/wp-content/uploads/2011/02/antibiotics-and-alcohol-drugs.jpg

Skin and mucous membranes are the first line of defense against pathogens.

The skin has a layer of dead Keratinised cells that constantly fall off. These form a barrier against pathogen entry. When the dead cells fall off they take attached bacteria with them.Arguably 70% of house dust is human skin. You shed 6g of skin a week.

http://medicineworld.org/images/blogs/2-2009/removing-those-skin-wrinkles.jpg

Mucus

Mucus is sticky and provides a protective layer keeping pathogens away from surfaces which cannot be keratinised:

In the nose, In the throat and

lungs,In the gut,In the vagina.

Antibody Production

The blood contains two types of white blood cell or leukocyte

Phagocytes ingest bacteria by endocytosis

Lymphocytes produce antibodies

Antibodies

• Antibodies are proteins that recognise and bind to specific antigens

• Antigens are foreign substances that stimulate the production of antibodies

• Many of the molecules on the surface of viruses and bacteria are antigens

Antibodies are specific – they usually bind to only one specific antigen.

Antigen

Antibodies

Microbe

Production of Antibodies by Lymphocytes

A lymphocyte can produce only one type of antibody so a huge number of different types are needed

Each lymphocyte has some of its antibody on its surface…

The antigens of a pathogen bind to the antibodies in the surface membrane of a lymphocyte…

…This activates the lymphocyte.

The active lymphocyte divides by mitosis to produce a clone of many identical cells

MITOSIS

The clone of cells starts to produce large quantities of the same antibody…

… the same antibody needed to defend against the pathogen!

Most microbes have more than one antigen on their surface, so…

…they stimulate more than one type of lymphocyte…

…resulting in the production of many different antibodies.

These are called polyclonal antibodies.

HL Stuff - Antibody Production: The Primary Response

Macrophages take in antigen by endocytosis

Antigen

Macrophage

The macrophage processes the antigen and attaches it to a membrane protein called a MHC protein

The MHC protein is moved to the cell surface membrane by exocytosis so that the antigen is displayed on its surface.

MHC protein

Step 1: Antigen Presentation

Helper T-cell binds to macrophage presenting the antigen

Step 2: Activation of Helper T-cell

Helper T-cells have receptors on their cell surface membranes which can bind to antigens presented by macrophages.

receptor

Helper T-cell

Macrophage sends a signal to activate the helper T-cell

Step 3: Activation of B-lymphocytes

B-cells have antibodies in their cell surface membranes

Inactive B-cell

Antibody

Antigens bind to the antibodies in the surface membranes of B-cells

Antigen

An activated helper T-cell with receptors for the same antigen binds to the B-cell

SIGNAL

The helper T-cell sends a signal to the B-cell, activating the B-cell.

Step 4: Proliferation

Plasma cells are activated B-cells with a very extensive network of rough endoplasmic reticulum.

Plasma cells synthesis large amounts of antibody, which they excrete by exocytosis.

The activated B-cell starts to divide by mitosis to form a clone of plasma cells.

The Secondary Response: Memory Cells

• If an antigen invades your body a second time, a much faster response occurs which produces much larger quantity of the required antibody.

•When activated B-cells are dividing during the primary response, some cells stop dividing and secreting antibody and become memory cells.

• Large numbers of memory cells remain in the body for a long time…• …they are capable of producing large amounts of antibody very quickly when stimulated.

B-cell

Macrophage

Antigen

Activate

Antigen

Helper T-cell

Activate

Clone

MemoryCell Plasma

CellAntibodies

Antibody Production: Summary

Human Immunodeficiency Virus

• The HIV is (as its name suggests) a virus – A protein coat around a stretch of RNA and a few enzymes.

http://upload.wikimedia.org/wikipedia/commons/6/63/HIV_Virion-en.png

AquiredImmunoDeficiencySyndrome

The HIV infects t-lymphocytes (an important part of the immune system).

Without an effective immune system opportunistic microbes can gain a foothold in the body.

AIDS is the collection of diseases and symptoms which is noticed to be caused by HIV.

TransmissionHIV is spread by sharing body fluids:

•1. through various sexual acts

•2. through sharing needles and blood transfusions

Censored

Exposure RouteEstimated infection rate

per exposure to an infected source

Blood transfusion 90% [34]

Mother-to-child, including pregnancy, childbirth and breastfeeding (no treatment) 25% [35]

Mother-to-child, including pregnancy, childbirth and breastfeeding (with treatment) 1%-2% [35]

Needle-sharing injection drug use 0.67% [36]

Percutaneous needle stick 0.30% [37]

Receptive anal intercourse (in order - 2009 & 2010 &1992 study) 1.7%[38] 1.4%[33] 0.5% [39][40

Insertive anal intercourse for uncircumcised men (2010 study) 0.62%[33]

Insertive anal intercourse for circumcised men (2010 study) 0.11%[33]

Insertive anal intercourse (based on data of a 1992 study) 0.065% [39][40]

Low-income country female-to-male 0.38%[38]

Low-income country male-to-female 0.3%[38]

Receptive penile-vaginal intercourse 0.1%[39][40][41]

Insertive penile-vaginal intercourse 0.05%[39][40]

Fellating a man 0.01%b[40]

Man being fellated 0.005%b[40]

The data shown represents transmission without the use of condoms. Risk increases substantially in the presence of genital ulcers, mucosal lacerations, concurrent sexually transmitted infections, or a partner with a high viral load of HIV. [42] Commercial sex exposure and national income levels may also impact risk.[38]

b Oral trauma, sores, inflammation, concomitant sexually transmitted infections, ejaculation in the mouth, and systemic immune suppression may increase HIV transmission rate.[45]

How easy is it to get infected with HIV?3233

^ Smith DK, Grohskopf LA, Black RJ, et al. (January 2005). "Antiretroviral postexposure prophylaxis after sexual, injection-drug use, or other nonoccupational exposure to HIV in the United States: recommendations from the U.S. Department of Health and Human Services". MMWR Recomm Rep 54 (RR-2): 1–20. PMID 15660015. Retrieved 2009-03-31

HIV / AIDS a global pandemic

Lois Jensen (2010). The Millennium Development Goals: Report 2010. New York, N.Y.: United Nations Department of Economic and Social Affairs.

Estimate Range

People living with HIV/AIDS in 2009 33.3 million 31.4-35.3 million

Adults living with HIV/AIDS in 2009 30.8 million 29.2-32.6 million

Women living with HIV/AIDS in 2009 15.9 million 14.8-17.2 million

Children living with HIV/AIDS in 2009 2.5 million 1.6-3.4 million

People newly infected with HIV in 2009 2.6 million 2.3-2.8 million

Adults newly infected with HIV in 2009 2.2 million 2.0-2.4 million

AIDS deaths in 2009 1.8 million 1.6-2.1 million

Orphans (0-17) due to AIDS in 2009 16.6 million 14.4-18.8 million

Who has HIV and AIDS?

Region

Adults & children

living with HIV/AIDS

Adults & childrennewly infected

Adult prevalence*

AIDS-related deaths in

adults & children

Sub-Saharan Africa 22.5 million 1.8 million 5.0% 1.3 million

North Africa & Middle East 460,000 75,000 0.2% 24,000

South and South-East Asia 4.1 million 270,000 0.3% 260,000

East Asia 770,000 82,000 <0.1% 36,000

Oceania 57,000 4,500 0.3% 1,400

Central & South America 1.4 million 92,000 0.5% 58,000

Caribbean 240,000 17,000 1.0% 12,000

East Europe & Central Asia 1.4 million 130,000 0.8% 76,000

North America 1.5 million 70,000 0.5% 26,000

Western & Central Europe 820,000 31,000 0.2% 8,500

Global Total 33.3 million 2.6 million 0.8% 1.8 million

Where is HIV and AIDS? (end of 2009)

The impact of AIDS on developing countries (especially Africa)?

Take a look at this website: http://www.avert.org/aids-impact-africa.htm

I have taken relevant bits of the article on the next pages:

Overview Impact on Hospitals

Impact on health workers Impact on Household income

Impact on Food productionImpact on Children

Impact on Education Impact on Teachers

Impact on Life expectancy

Impact of Aids

Two-thirds of all people infected with HIV live in sub-Saharan Africa, although this region contains little more than 10% of the world’s population.

During 2009 alone, an estimated 1.3 million adults and children died as a result of AIDS in sub-Saharan Africa.

Since the beginning of the epidemic more than 15 million Africans have died from AIDS.

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The impact on hospitals As the HIV prevalence of a country rises, the strain placed on its hospitals is likely to increase. In sub-Saharan Africa, people with HIV-related diseases occupy more than half of all hospital beds.5 Research in South Africa has suggested that, HIV-positive patients stay in hospital four times longer than other patients.6

Nurses working on the HIV ward at Kisiizi Hospital in Uganda

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The impact on Health care workers

While AIDS is causing an increased demand for health services, large numbers of healthcare professionals are being directly affected by the epidemic. Botswana, for example, lost 17% of its healthcare workforce due to AIDS between 1999 and 2005. A study in one region of Zambia found that 40% of midwives were HIV-positive.7 Healthcare workers are already scarce in most African countries. Excessive workloads, poor pay and migration to richer countries are among the factors contributing to this shortage.

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The impact on Household income

In Botswana it is estimated that, on average, every income earner is likely to acquire one additional dependent over the next ten years due to the AIDS epidemic. A dramatic increase in destitute households –with no income earners – is also expected.Individuals who would otherwise provide an income are prevented from working – either because they are ill with AIDS or they are caring for another sick family member. Children may be forced to abandon their education and in some cases women may be forced to turn to sex work ('prostitution'). This can lead to a higher risk of HIV transmission. B

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The impact on Food production

The AIDS epidemic adds to food insecurity in many areas, as agricultural work is neglected or abandoned due to household illness.

In Malawi, where food shortages have had a devastating effect, HIV and AIDS have diminished the country’s agricultural output. It was calculated in 2006 that by 2020, Malawi’s agricultural workforce will be 14% smaller than it would have been without HIV and AIDS. In other countries, such as Mozambique, Botswana, Namibia and Zimbabwe, the reduction is likely to be over 20%.

“I used to stay with the children, but now it is a problem. I have to work in the fields. Last year I had more money to hire labour so the crops got weeded more often. This year I had to do it myself.” - Angelina, Zimbabwe

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The impact on Children

As parents and family members become ill, children take on more responsibility to earn an income, produce food, and care for family members. It is harder for these children to access adequate nutrition, basic health care, housing and clothing.

Because AIDS claims the lives of people at an age when most already have young children, more children have been orphaned by AIDS in Africa than anywhere else. Many children are now raised by their extended families and some are even left on their own in child-headed households.

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The impact on EducationThe relationship between AIDS and the education sector is circular – as the epidemic worsens, the education sector is damaged, which in turn is likely to increase the incidence of HIV transmission. In Swaziland and the Central African Republic, it was reported that school enrolment fell by 25-30% due to AIDS at the beginning of the millennium.

Children may be removed from school to care for parents or family members, or they may themselves be living with HIV. Many are unable to afford school fees – this is particularly a problem among children who have lost their parents to AIDS, who often struggle to generate income.

Studies have suggested that young people with little or no education may be around twice as likely to contract HIV as those who have completed primary education.

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The impact on teachers HIV and AIDS are having a devastating effect on the already inadequate supply of teachers in African countries; for example, a study in South Africa found that 21% of teachers aged 25-34 were living with HIV.

Teachers who are affected by HIV and AIDS are likely to take periods of time off work. When ill, the class may be taken on by another teacher, may be combined with another class, or may be left untaught.

The illness or death of teachers is especially devastating in rural areas where schools depend on one or two teachers. In Tanzania in 2006 it was estimated that around 45,000 additional teachers were needed to make up for those who had died or left work because of HIV and AIDS. The greatest proportion of staff that have been lost, were experienced staff between the ages of 41 and 50.

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The impact on life expectancy

In many countries of sub-Saharan Africa, AIDS is erasing decades of progress in extending life expectancy. Life expectancy at birth in Swaziland is just 31 years - less than half of what it would be without AIDS.34

The impact of AIDS on average life expectancy is partly attributed to child mortality, as increasing numbers of babies are born with HIV infections acquired from their mothers.

The biggest increase in deaths, has been among adults aged between 20 and 49 years. (60% of all deaths in sub-Saharan Africa, compared to 20% between 1985 and 1990). By affecting this age group so heavily, AIDS is hitting adults in their most economically productive years and removing the very people who could be responding to the crisis. B

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