The bird's flu, AIDS (acquired immune deficiency syndrome) and the mad cow disease are threatening diseases which involve different routes of transmission.

As an individual, what can you do to avoid contracting diseases?

What can the government do to prevent and control the spread of these diseases?

Discuss the feasibility of developing vaccines for combating these diseases.

[2000 Paper II Question Number 9] 

What is Bird's Flu?

• bird's Flu is caused by virus
• belongs to group influenza A H5N1
• the virus was known to infect only various species of birds, including chicks and ducks
• first discovered in terns in South Africa in 1961
• in May 1997, influenza A(H5N1) virus was isolated from a child who died in Hong Kong

History of Influenza

• was first described in 412 BC
• first well-described influenza-like disease occurred in 1580
• three occurring in this century: in 1918, 1957 and 1968
• all originated from animals (1918 = swine, 1957 and 1968 = avian strains)
• the Spanish Flu between 1918 and 1920 killed 30 million people around the globe
• the virus is H1N1
• the latest outbreak of the Bird's Flu occured in 1997 in Hong Kong

Bird's Flu in Hong Kong

• two outbreaks in Hong Kong history
• the first happened in May 1997 and claimed 7 lives
• the second in 2001 did not infect any human being
• both resulted slaughter of millions of chicks and ducks in Hong Kong
• the Government lost a lot of money in compensation
• the virus is suspected to be brought in from China

Route of Transmission

• two words: air borne
• get into the body during inhalating air with presence of virus
• virus come out to air from host when sneezing

To see how body react when the virus get in

click to view a short film

So What Can We Do?

• avoid travelling to epidemic region
• it is a convention that governments will issue warnings to her citizen for not going to the epidemic region
• avoid contacting vector and infected person
• the disease transmitts through the air thus close contact to vector should be avoided
• should not go to public places such as schools, malls and swimming pools etc.
• of course, always exercises to keep yourself healthy

  　

And What Should / Have the Government Do?

• educate the public
• public should be educated on how to prevent getting the disease
• public should also be taught the differences between cold, flu and inhalation anthrax
• increase in knowledge on these diseases will reduce the money the government expenditure and the could-have-saved time on diagnosis
• eradicate infected poultry
• in both cases of Bird's Flu in Hong Kong, all chicks and ducks were killed
• however that may lead to the end of trace to the sources of disease
• it is an expensive method and cannot prevent another outbreak
• introduce a new system in investigation
• every farmland in Hong Kong is requested to have a license for having chicks and ducks
• even if a single chick is found to have Bird's Flu, all the poultry in the farmland will be killed
• full compensation is given to prevent the farmers not reporting the case
• identify potential epidemic region
• market selling poultry are now cleaning every month
• area occupied by each poultry in a cage is regulated
• real virus reservoir is not chickens because the infection in this species is fatal

Is There Any Vaccine?

• genetic Engineering is applied to produce vaccine against influenza
• it can isolate the genes encoded for the surface antigens of the viruses
• genes are cloned and expressed in production systems
• protein products are used as vaccines
• however, vaccine is not suitable in Bird's Flu case because the production of vaccine need fertilized eggs but virus can kill it
• researches are carrying on to find an alternative way in vaccine production
• specific vaccine is not recommended because virus undergo mutation quickly and the vaccine will become useless

What is Mad Cow Disease?

• Mad Cow Disease (MCD) is officially called Bovine Spongiform Encephalopathy (BSE)
• caused by a kind of protein called prion (proteinaceous infectious particle)
• a cow disease but get into human body after we eat beef
• first found in the United Kingdom in 1986, then Western Europe and now Japan
• has claimed at least a hundred lives with more than 80 in UK
• real figure is believed to be much higher as many are classified as encephalopathies
• not yet found in Hong Kong
• though BSE is newly found, similar diseases exist in animals for several centuries
• not a single victim has ever recovered

What is Prion?

• prion is protein
• we all have prion in our bodies, in the form PrP
• however if Prp changes its shape into Prp-sc, it will concentrate in the brain
• in cow's case, it becomes unstable and can't stand up, acts unpredictable and die
• their brain will become in spongy form like a Swiss cheese

BSE the Only Form?

• there are many kinds of spongiform encephalopathies in human
• CJD: Creutzfeld-Jacob Disease
• GSS: Gerstmann-Straussler-Scheinker syndrome
• FFI: Fatal familial Insomnia
• Alpers Syndrome
• Kuru

The First Prion Disease

• Kuru is the first Prion Disease in human
• in Papua New Guinea many people in a tribe died with a spongy brain
• it is found that they ingest brain tissue of dead relatives
• they ground up the brain into a pale grey soup, heated and ate it
• the disease almost disappear after they were encouraged not to eat brain
• however at that time the principle behind this was not understand
• now it is believed a member of the tribe develop the disease and it spread when the highly infected brain was eaten

What is the Origin of the Disease?

The Sheep.

How can the Sheep Cause the MCD?

• there are many different types of prion diseases in mammals
• TME (transmissible mink encephalopathy) in mink
• CWD (chronic wasting disease) in muledeer and elk
• BSE (bovine spongiform encephalopathy) in cows
• the one in sheep is called Scrapie
• normally the disease Scrapia, which is also a kind of spongiform encephalopathy, would only transmitt among the sheep
• to obtain higher milk yields and growth rates, the nutritional value of feed for farmed animals was routinely boosted
• how? by the addition of protein derived from waste meat products and bonemeal (MBM) prepared from animal carcasses
• including sheep and cows.

Figures of BSE

Where do We Get BSE?

• contaminated Food
• mad cow seems to comes from healthy cows eating remains from infected cows
• spinal cord, brain, eyes, tonsils and intestines of cattle are considered as the most dangerous part for containing prion
• it is not to be contagious person-to-person
• milk and milk products are considered safe as well as tallow and gelatin

The Truth is Out There?

Some say that prion comes from the deep universe. They fall on the Earth with the asteroid and the cows eat the grass covered by the dust.

 However, there is no solid proof for this idea.

Cook to Prevent MCD?

• cooking can kill most of the bacteria, but not prion
• some prion can survive at tempature above 300°C for half an hour
• it takes 10 minutes with 2M NaOH to denature most prion
• of course you can burn your food with 400°C for an hour and soak it with 18M NaOH solution for half an hour. But what will your food looks like after all that?

Is Vaccine Possible?

• difficult to produce vaccines as prion is a kind of protein
• research on prion blood test
• Amphotericm is discovered to delay prion disease in hamsters but has little effect on human
• two drugs, Quinacrine and Chlorpromazine are claimed to be the antibodies inhibiting prion propagation. No further information can be obtained at this stage

How do You Know Prion is Protein?

• experiments have be conducted to investigate the nature of prion. One of the simplier experiments is as the following
• under high dose of radiation, percentage of activity of all organisms decrease as the nucleic acid is destroyed
• however prion (in this case Scrapie) does not have a decrease in activity
• thus the agent to this disease has no DNA or RNA

Will We Get Prion?

• after all of this, you may wonder if we get prion easily even in our internal bodies
• because most mammals can develop prions inside
• but in fact the conversion of PrP to PrP-sc requires a large amount of energy, i.e. an energy barrier
• and even if we have prions in our bodies, it will take almost a decade before it really comes out to affect

How the Government Reacted?

• good question. That depends on which country you are in
• UK has banned the use of ruminant proteins since 1988
• US has killed thousands of sheep which is believed to have BSE
• use of sheep in cattle feed was banned in 1989
• many countries banned the import of British beef
• UK killed all cows and sheeps that is thought to have the disease and incinerated them
• however prions may still survive after the burning and enter the underground water
• the incineration may produce a large amount of dioxin which is carcinogenic
• but at least they are the positive reactions. Many can still remember, what the UK government said before...

What Did They Say?

"There is no conceivable risk of BSE being transmitted from cows to people." Stephen Dorrell, Minister of State for Health, 1995.12.3

"No conceivable risk, beef is safe..." John Major, Parliament, 1996.3

"British beef is the safest in the world." Just about anyone from the Prime Minister down who is concerned about the economics of the food industry just about all of the time

"Was the British Government responsible for the whole disastrous mess [BSE]? No it wasn't. In the main it was an act of God." Richard Packer, MAFF permanent secretary, 1999.10

"A previously unrecognised and consistent disease pattern." "Although there is no direct evidence of a link... the most likely explanation at present is that these cases are linked to exposure to BSE." UK Spongiform Encephalopathy Advisory Committee (SEAC) 1996

'Yes, we could face a major epidemic... Yes, it is possible that very many people will die... Yes, it could theoretically be hundreds of thousands.' Professor John Pattison, Chairman of SEAC, 1996

"... ministers and civil servants were guilty of repeatedly misleading the public about the threat to human health posed by mad cow disease." Official BSE inquiry, Lord Phillips, 2001

Am I Going to Die?

"Always look on the bright side of life.... dedo.. dedo.. dedo.. dedo.."

"Life of Brian", Monty Python, 1970s