Animal and plant diseases
Plant Diseases
- Plant diseases threaten people as if crop fail, people will not have food they need to survive. Also economies may suffer and jobs may be lost.
- Ring Rot; An example of a bacterial plant disease...
- Affects potatoes, tomatoes and aubergines and is caused by the gram positive bacteria C. michiganensis. It damages leaves, fruits and tubers and there is no cure. Once bacterial ring rot infects a field it cannot be used for at least two years.
- Tobacco Mosaic Virus; An example of a plant virus...
- Affects tobacco plants among 150 other species, damaging leaves, flowers and fruit, stunting growth and yield. There is no cure, but there are resistant crop strains.
- Potato Blight; An example of a plant protoctist...
- Caused by the fungus like oomycete P. infestans. its hyphae penetrate host cells, destroying leaves, tubers and fruit. There is no cure, but there are resistant crop strains. Careful management and chemical treatment reduces risk.
- Black Sigatoka; An example of a fungal disease in plants...
- Caused by the fungus M. fijiensis which attacks and destroys the leaves. Hyphae penetrate and destroy plant cells, causing the leaves to turn black unable to photosynthesise, causing a 50% reduction in yield. There is no cure, but fungicides, good husbandry and resistant strains can reduce chance of infection and spread.
- Plant diseases threaten staple crops such as rice, maize and banana.
- Bananas are grown in over 130 countries, where they are a staple for the economy and for survival. Plant diseases threaten economic stability and humanitarian welfare.
- 90% of bananas grown on small plantations are eaten locally; black sigatoka is accompanied by a threat of starvation.
- 10% of all bananas are produced on plantations for the West - these bananas are all clones of each other, the Cavendish variety. As they are all genetically identical, a single strain of a plant pathogen would be able to wipe them out completely as none of them would be resistant.
Animal Diseases
- Tuberculosis: an example of a bacterial animal disease...
- Caused by M. tuberculosis and M. bovis, it affects humans, cows, pigs, badgers and deer. It damages lung tissue and suppresses the immune system, making the suffer more susceptible to other illnesses. TB is curable with antibiotics and preventable with vaccination and good living conditions.
- Bacterial Meningitis: an example of a bacterial animal disease...
- Caused by S. pneumoniae and N. meningitidis affecting the meninges (protective membranes) of the brain, which can spread to the rest of the body causing septicaemia and death. Antibiotics can cure the disease if delivered early, and vaccinations protect against some strains.
- HIV/AIDS: an example of a viral animal disease...
- Acquired immunodeficiency syndrome caused by human immunodeficiency virus which targets T helper cells. It gradually destroys the immune system leaving people susceptible to other diseases, such as TB, pneumonia and some types of cancer. HIV is a retrovirus, meaning it has RNA as its genetic material, and contains reverse transcriptase enzyme to transcribe a single DNA strand in the host, interacting with the hosts own DNA. There is no cure or vaccination, but anti-retroviral drugs give years more life.
- Influenza: an example of a viral animal disease...
- Kills the ciliated epithelial cells in the ventilation system, leaving the sufferer more susceptible to other diseases. It can be fatal to the very young, old, and chronically ill. It affects mammals and birds, and the strains are classified as A, B or C, with A strains the most virulent and further classified by their surface proteins. Due to the frequent mutation of the flu virus, there is no vaccination or cure, but often the mutation is small enough to leave previous sufferers with some immunity the following year. Big mutations can cause epidemics.
- Malaria: an example of an animal protoctist...
- Caused by the Plasmodium protoctist, spread via the vector of the Anopheles Mosquito. The protoctist reproduces inside the mosquito, before being passed to humans when the mosquito bites. It invades the red blood cells, liver and brain; the disease then makes people weak to other infections. There is no vaccine and limited cures but preventative methods such as antimalarials in conjunction with controlling the vector through insecticides and mosquito nets can prevent the spread.
- Ringworm: An example of a fungal disease affecting mammals...
- Different fungi affect different species, causing grey, crusty, infectious areas of skin. It can be treated with anti-fungal creams.
- Athlete's Foot: An example of a human fungal disease...
- Caused by T. pedia it is a form of ringworm which grows on and digests the warm moist skin between the toes. It can cause cracking and scaling becoming itchy and sore. It can be treated with antifungal creams.
Applied Stuff
TB, Cows and Badgers
Zoonotic Influenza
Identifying Pathogens
TB, Cows and Badgers
- In 2013, 33000 cattle were killed due to the spread of bovine TB. Evidence suggest wild animals such as badgers are vectors of the disease. Culling the vectors can reduce infection rates, but if not done effectively it can lead to greater disease spread. Some people are against culling on ethical grounds.
- Tests for bovine TB cannot distinguish between the active pathogen and the vaccinated form, so the EU bans cattle vaccines.
Zoonotic Influenza
- A Zoonosis is a disease humans can catch from animals. E.G. The bird flu or swine flu virus is sometimes capable of mutating and infecting humans. New mutated strains are serious as people have no immunity to them.
- In 2009, 60% of Mexican villagers became infected with the H1N1 Swine Flu virus, which had never been seen before. It spread to 61 countries including the US and UK causing a pandemic. The mutation meant to vaccines were suitable in fighting the virus. It took 6 months to produce a vaccine, with up to 300,000 dying as a result.
Identifying Pathogens
- The key to a successful cure is identifying the pathogen involved in an outbreak.
- Originally, pathogens were cultured in a lab and identified under a microscope.
- Monoclonal antibodies can now be used to identify pathogens by their antigens.
- DNA sequencing can be used to identify pathogens down to a single mutation.
- If infections are different strains, we can know that the cases are not linked and no single carrier is responsible.