Animal And Plant Diseases Flashcards
How do plant diseases threaten people
When crop plants fail, people suffer. They may starve, economies may struggle and jobs are lost. Plant diseases threaten ecosystems too-entire species can be threatened.
Ring rot
A bacterial disease of potatoes, tomatoes and aubergines caused by gram positive bacterium. It damages leaves, tubers and fruit. It can destroy up to 80% of the crop and there is no cure. Once bacterial ring rot infects a field it cannon be used to grow potatoes again for at least two years.
Tobacco mosaic virus
(TMV) - a virus which infects tobacco plants and around 150 other species including tomatoes, peppers, cucumbers, petunias and delphiniums. It damages leaves, flowers and fruit, stunting growth and reducing yields, and can lead to an almost total crop loss. Resistant crop strains are available but there is no cure.
Potato blight (tomato blight,late blight)
Caused by the fungus-like protoctist. The hyphae penetrates host cells, destroying leaves, tubers and fruit, causing millions of pounds worth of crop damage each year. There is no cure but resistant strains, careful management and chemical treatments can reduce infection risk.
Black Sigatoka
A banana disease caused by the fungus, which attacks and destroys the leaves. The hyphae penetrate and digest the cells, turning the leaves black. If plants are infected it can cause a 50% reduction in yield. Resistant strains are being developed-good husbandry and fungicide (a chemical that kills fungi) treatment can control the spread of disease but there is no cure.
Animal diseases
The diseases that affect animals- in particular humans- have a profound effect on the human health and wellbeing-and on national economies. Communicable diseases range from mild to fatal.
Tuberculosis
A bacterial disease of humans, cows, pigs, badgers and deer. TB damages and destroys lung tissue and suppresses the immune system, so the body is less able to fight off other diseases. The global rise of HIV/AIDS has had a big impact on the numbers of people also suffering from diseases such as TB, because people affected by HIV/AIDS are much more likely to develop tb infections. In people tb is both curable by antibiotics and preventable by improving living standards and vaccination.
Bacterial meningitis
Bacterial infection of the meninges of the brain which can spread into rest of body causing septicaemia(blood poisoning) and rapid death. Mainly affects very young children and teenagers ages 15-19. Normally a blotchy red/purple rash that doesn’t appear when a glass is pressed against it is a symptom of septicaemia and immediate medical treatment is needed. 10% infected will die. 25% have permanent damage. Antibiotics will cure the disease if delivered early. Vaccines can protect against some forms of bacterial meningitis.
HIV/AIDS (acquired immunodeficiency syndrome)
Caused by HIV (human immunodeficiency syndrome) which targets T helper cells in the immune system of the body. It gradually destroys the immune system so affected people are open to other infections like tb as well as some types of cancer. HIV/AIDS can affect humans and some non-human primates. HIV is a retrovirus with RNA as its genetic material. It contains the enzyme reverse transcriptase, which transcribes the RNA to a single stand of DNA to produce a single strand of DNA in the host cell. The virus is passed from one person to another in bodily fluids eg unprotected sex or shared needles or mothers during pregnancy, birth, or breast feeding. No vaccine or cure, but anti-retroviral drugs slow the progress of the disease to give many years of healthy life. Girls or women are very high risk in many countries. Traditional practices such as female genital mutilation (FGM) increase the infection rate- if the same equipment is used, also more high risk during intercourse. Sub-Saharan Africa is worst.
Influenza (flu)
Viral infection of the ciliated epithelial cells in the gas exchange system. It kills them, leaving airways open to secondary infection. Can be fatal, especially young and old and people with chronic illnesses. Many of these deaths are from severe secondary bacterial infections such as pneumonia on top of the original viral infection. Flu affects mammals, including humans and pigs, and birds, including chickens. There are three main strains-A,B and C. Strain A viruses are the most virulent and they are classified further by the proteins on their surfaces. Flu viruses mutate regularly. The change is usually quite small, so having flu one year leaves you with some immunity for the next. Every so often, however there is a major change in the surface antigens and this heralds a flu epidemic or pandemic as there are no antibodies available. Vulnerable groups are given a flu vaccine annually to protect against ever changing strains. There is no cure.
Malaria
Caused by protoctista plasmodium and spread by bites of infected mosquitoes-vector. The plasmodium parasite has a complex life cycle with two hosts-mosquitoes and people. They reproduce inside the female mosquito. The female needs to take blood meals to provide her with protein before she lays her eggs- and this is when plasmodium is passed on to people. It invades the red blood cells, liver and even brain. The disease recurs, making people weak and vulnerable to other infections. There is no vaccine against malaria and limited cures, but preventative measures can be very effective. The key is to control the vector. Mosquitoes can be destroyed by insecticides and by removing the standing water where they breed. Simple measures such as mosquito nets, window and door screens and long sleeved clothing can prevent them biting people and spreading disease.
Ring worm
Fungal disease affecting mammals including cattle, dogs cats and humans. Different fungi affect different species. Caused grey-white, crusty, infectious, circular areas of skin. It is not damaging but looks unsightly and may be itchy. Antifungal creams are an effective cure.
Athletes foot
Human fungal disease caused by a form of human ring worm that grows on and digests the warm, moist skin between toes. It causes cracking and scaling, which is itchy and may become sore. Antifungal creams are an effective cure.
