Pathogens

Disease causing agents

Plague!17th Century: Europe

Bubonic plague

outbreak, kills tens of

millions. People tried to prevent

catching it by filling nose-covers with fragrance

1900: Sydney

Bubonic plague: rats were killed to prevent the movement of the disease

1997 – 2004: worldwide

Avian influenza: particular strain (H5N1) infects

humans. Technology used to notify of changes in immigration of humans and animals. Relenza

(drug) used to treat human patients

2009: worldwide

H1N1 influenza virus (swine flu). Most common

human flu in 2009. Antiviral drugs like Zanamir used to

treat patients

Disease

Anything that harms an individual. Inherited: genetic disorders (Unit 4) Deficiencies: not enough of a particular

nutrient

Infectious disease: caused by pathogens Non-cellular (prions/viruses) Cellular (microorganisms like bacteria or fungi)

Pathogens

Are any parasites (organisms living off another) that cause harm or damage to the host.

Usually contagious (spread by person to person contact) or infectious (spread via the air)

Prions

Non-cellular pathogens (not alive in their own right) Abnormal proteins – slightly warped or twisted Abnormal protein has the ability to change the

shape and function of normal protein in neurons Not affected by agents such as enzymes Not killed by cell – eventually cause lysis and are

free to infect other cells

Animation: prions

http://www.1lec.com/Microbiology/Prion/index.html

The discovery of prions

1913: Dr Creutzfeld examines the body of a patient that died during an odd breakdown which involved shaking and jerking. There is extensive damage to her brain cells.

1957: New Guinea: natives are observed jerking, shaking and with uncontrollable facial tics. Disease locally called “laughing death”. Funeral rites included eating bodies of the dead. Brain cell damage was found in bodies. This disease is known as Kuru.

Continued…

1960s-80s: human growth hormone harvested from pituitary gland of cadavers and given as a fertility drug. Women who received treatment sometimes got disease described by Dr Creutzfeldt

1985: UK: people observed with similar symptoms. Have eaten beef, containing prions. Mad Cow Disease.

Viruses

Also non-cellular Must infect a host cell to reproduce

Source: http://www.csa.com/discoveryguides/avian/images/virus.jpg

Different viruses infect different cells Humans and mammals (flu, measles, cold

sores… hundreds more) Birds Reptiles Plants Even bacteria (bacteriophage) In fact, all living things are susceptible to

some kind of viral infection

Classification of viruses

Classification may include: Required host Kind of nucleic acid contained (DNA or RNA) Structures on protein coat

Life Cycle of a Bacteriophage

Source: http://www.nature.com/nrmicro/journal/v4/n5/images/nrmicro1393-i1.jpg

Life Cycle of a human virus

Source: http://www.ifpma.org/fileadmin/templates/influenza/images/replication_cycle.jpg

Papilloma virus (warts)Warts are spread by direct contact

The “normal” manifestation of the wart virus

Papilloma virus contains DNA, not RNA like the flu virus

The “tree man” is a result of the Papilloma virus attacking someone who is immuno-compromised. His body could not control the effects of the virus, so it took over.Picture sources:

http://www.pharmas.co.uk/blog/wp-content/uploads/2010/02/hpv_1.jpg

http://www.femalegenitalwarts.org/wp-content/uploads/2009/08/Human-Papillomavirus-hpv-300x225.jpg

http://www.geekologie.com/2008/04/16/tree-man-2.jpg

Measles/ RubellaAlso known as German Measles, Rubella manifests itself as painful red spots on the host’s skin.

Pregnant women who catch the virus are at risk of passing a variety of illnesses to their unborn child

In Australia and many other parts of the world, Rubella is controlled by vaccination programs where children are given deactivated viruses to promote immunity against infection.

Picture sources:

http://php.med.unsw.edu.au/embryology/images/thumb/2/2a/Infant_rubella_virus.jpg/400px-Infant_rubella_virus.jpg

http://wholefoodusa.files.wordpress.com/2009/03/vaccine_-_disease_decline.png?w=366&h=400&h=400

Poliomyelitis (polio)Polio has been effectively eradicated in Australia, due to rigorous vaccination programs.

It used to be common that children in particular would contract the polio virus, and muscles would weaken. In order to stay alive, some had to have a machine called and Iron Lung breathe for them.

The poliovirus only causes the disease if it enters the bloodstream. If not, it is asymptomatic. This is why vaccination must continue!!

Polio is spread oral-oral or intestinal-oral

Picture sources:

http://wholefoodusa.files.wordpress.com/2009/03/vaccine_-_disease_decline.png?w=366&h=400&h=400

http://www.thegeminigeek.com/wp-content/uploads/2009/06/polio.gif

Pest control (Rabbit Calicivirus)Rabbits have become a pest species in most regions of Australia. As a result, we have had to find an effective way of controlling their numbers. The most successful has been the introduction of lethal rabbit viruses, the most recent called Calici Virus (introduced in 1996).

Treatment of viruses

Many are fought by the body efficiently, so medication is not required (flu/cold)

Some are not efficiently fought by body, nor is medication available (Human Immunovirus)

Antiviral drugs available for some: May act to inhibit particular enzymes involved in disease

progress Relenza = anti-flu drug Cells may produce interferon when infected: blocks viral

protein synthesis in neighbouring areas

Plant viruses

“mosaics” – differential coloured splotches on plants

Usually transmitted via insect vectors

Pepino Mosaic Virus infection (PepMV). PepMV is a highly contagious agricultural pest causing significant destruction of plants in tomato production. Symptoms consist of distorted leaf development, mosaic, bubbling of the leaf surface and some chlorosis (loss of chlorophyll).

Source: http://www.sciencephoto.com/images/download_wm_image.html/C0015943-Tomato_plant_infected_with_mosaic_virus-SPL.jpg?id=670015943

Viroids

Naked RNA Only identified as pathogenic to plants Completely dependent on host cell for all

functions