Immune System and Vaccination Science Project.
Science Fair Project Idea - How the body acquires special power to fight disease.
You already have some information that proves to you that special ability to fight disease may be acquired by the body.A child has, had whooping cough, or mumps, or measles.Does this have any effect upon his chance of taking the disease again?What, therefore, is your conclusion as to the effect of having had a disease upon the ability of the body to fight that disease ?
Based upon this fact, it has been discovered that the body may be made immune to certain diseases or protected against them.You know of a number of such cases.Why is smallpox not the common disease it was several hundred years ago ?How are the soldiers protected against typhoid fever?Why is diphtheria not the dreaded disease it was twenty-five years ago?
The most striking cases of acquired immunity are for smallpox, typhoid fever, diphtheria, hydrophobia or rabies, and anthrax, a disease of animals.Efforts are being made to develop acquired immunity from other diseases, and considerable success has been obtained in the treatment of tetanus or lockjaw, boils and carbuncles, meningitis and plague.
(a) Vaccination against smallpox.Over a hundred years ago, Edward Jenner, an English physician, observed that dairymaids were not subject to smallpox, which at that time was a very common disease.His experiments based on this observation have led to the practice of vaccination to develop immunity from smallpox.Cattle may have a disease known as cowpox, during which small sores appear on the animals.These sores contain the germs of the disease.Jenner found that by scratching the arm of a person and rubbing into the slight wound some material from these sores on cattle, a mild disease, cowpox, was developed in the person thus vaccinated.During the process of the disease, something, evidently developed in the blood which protected the person from smallpox.
Since vaccination has been practiced, smallpox, previously one of the most common diseases, has become a very rare one, developing only when vaccination is neglected.Stricter regulations by boards of health, especially in regard to isola- tion of patients, has helped materially in bringing about this result.Formerly, when not so great care was taken as now to insure the purity of the vaccine, infection occasionally occurred from other germs introduced into the wound.This has now been obviated, and anyone who objects to vaccination is unwilling to perform his part as a good citizen to maintain the health of the community.
(b) Vaccination against typhoid fever.Vaccination in this case is performed by injecting into the body a large number of dead typhoid fever bacteria.Usually three injections are given at intervals of several days.Typhoid fever up to recent times has been the special scourge of army camps.The value of anti-typhoid vaccination may be appreciated if we compare the prevalence of the disease in the army before and after vaccination was practiced.
In the Franco-Prussian War, 60 per cent of the total German mortality was due to this disease.In the Spanish- American War the army of the United States consisting of 107,973 men had 20,738 cases of typhoid fever and 1580 deaths from the disease.During the summer of 1911, after the adoption of anti-typhoid vaccination by our govern- ment, an army division of over 12,000 men was encamped at San Antonio, Texas, for about four months.Among these men only one case of typhoid fever developed and that was of a soldier who had not completed the necessary inocula- tion.In the armies of the Great War, typhoid fever was an almost unknown disease.
(c) Immunity from diphtheria.The antitoxin which has curative as well as immunizing power against diphtheria is made in the following manner.The bacteria are permitted to develop in a culture medium until a considerable quantity of toxin, or the poison produced by the germ, is present.After all the living germs have been killed, a small amount of the toxin is injected into a healthy horse.The toxin evidently stimulates the blood of the horse to manufacture something called antitoxin which counteracts the poison so that the later injection of toxin may be greater in amount without injury to the horse.This process is continued until the amount of toxin injected into the horse is several hundred times as much as would have killed it at the begin- ning.
A certain amount of the blood which contains great quantities of antitoxin is now removed from a large vein in the neck of the horse.(All this is done without pain or injury to the animal.)The serum which separates from the blood when it clots contains the antitoxin.This serum is tested for the amount of antitoxin it contains, is sterilized, and put into vials ready for use by physicians.
The accompanying chart shows the effect of the use of antitoxin upon the death rate from diphtheria in New York City.
Antitoxin is of greater use as a curative than as an immunizing agent.Persons who have been exposed to diphtheria will be protected only from two to six weeks, but this is usually long enough to protect the members of a family in which there is a case of the disease.As a cure for diphtheria, it is most important that the antitoxin be given at a very early stage of the disease.
(d) Pasteur treatment for hydrophobia or rabies.This disease especially affects the nervous system.Pasteur, a noted French scientist, found that while the spinal cord of a rabbit having the disease contains a large amount of the poison of the disease, the virulence or power of the poison decreases if the spinal cord is removed from the rabbit and allowed to dry.As the disease does not develop for some time after a person is bitten by a mad dog, there is sufficient time for treatment.The treatment consists in the injection of material from a rabbit's spinal cord which has been permitted to dry until the poison has almost entirely disappeared.This is followed by more injections, for a period of about three weeks.The many cases which have been treated by this indicate the usefulness of vaccinations and anti-toxins.Just as in the case of the use of antitoxin for treatment of diphtheria, this treatment should be begun at the earliest possible time after infection has occurred.
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