Your dog licks your face to show his love and affection for you. But make sure you exercise caution to stop the spread of infectious diseases
[dropcap]D[/dropcap]id you know that a recent study revealed the origin of the SARS coronavirus as Chinese horseshoe bats? The study was conducted by an international team of CSIRO scientists from the United States, China, Australia and Singapore and published in October 2013. Samples were taken from a horseshoe bat colony in Kunming, China and carefully analysed. Seven different strains of the virus were found to be circulating
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Research suggests that the toxoplasmosis parasite may be responsible for triggering the development of bipolar disorders and schizophrenia in humans. The T. gondii parasite may affect the production of dopamine, norepinephrine and other neurotransmitters in the brain which control various cognitive and behavioural functions. The parasite could alter chemical messages in the brain which could in turn alter behaviour. Studies are continuing.[/box]
Severe Acute Respiratory Syndrome, or SARS, a serious viral infection of the airways and lungs, was first identified in 2003. The first cases were reported in Asia during February 2003. During a nine-month period between November 2002 and July 2003, over 8,000 cases of SARS were reported and 774 people died. The virus spreads through infected droplets dispersed into the air from coughs and sneezes. Cases were soon reported in Europe and North and South America.
From bats to humans
The two SARS-like coronaviruses that were identified in Chinese horseshoe bats are closely related to the pathogen that infects humans and binds to the same
receptor cell. Scientists now believe that the path from the original species to humans is more direct, without an intermediate species as once thought. People living in
close proximity to bats would create the ideal environment for the virus to jump between species as the virus is excreted in bat faeces. This new research can be used to learn more about the SARS virus and
possibly develop a vaccine.
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What is a zoonotic disease?
According to Dr Dorianne Elliott, head veterinarian at the Bird and Exotic Animal Hospital at Onderstepoort, a zoonotic disease is one that can be transferred from
animals to humans. The World Health Organisation (WHO) says there are over 200 zoonotic diseases. Many serious diseases responsible for large numbers of human deaths are caused by zoonoses. These include yellow fever, anthrax, the Ebola virus, Lyme disease, rabies, mad cow disease, malaria, avian influenza (bird flu) and the more recent H1N1 virus, commonly called swine flu. While some zoonotic diseases have been known for centuries, about 75% of emerging infectious diseases which affect humans, are zoonotic.
Pathogens and transmission
Zoonotic diseases are caused by various pathogens. These may be viral, bacterial, parasitic, fungal or vector-borne diseases, like malaria or the West-Nile virus. Depending on the agent, zoonotic diseases are spread through a variety of different ways. “Rabies is passed on through bite wounds or contact with the saliva of infected animals,” explains Dr Elliott. “Many other diseases, such as salmonella, are transferred from animal faeces to the mouth or nose of a human, and certain diseases such as chlamydia can be passed on when a human inhales aerosolised feather dust or faeces from an infected bird.” She also explains that while some viruses, like swine flu, must mutate to affect humans, many zoonotic organisms are adapted to affect multiple hosts without any changes to their physiology.
People working closely with animals, including livestock, wild animals and those with domestic pets, are at risk of contracting zoonotic diseases. Humans may also contract diseases through water and soil contaminated by infected animals or by ingesting foodstuffs like infected meat, unpasteurised dairy products or unpurified water