Question

Anthrax is a fatal, contagious disease that affects farm animals and humans. This disease has received a lot of media attention because it’s one of several that can be used as biological warfare agents. To learn more about this disease, scientists at the Biological Warfare Research Center at Fort Dietrich, Maryland set up the following experiment:

One herd of 100 cows was injected with liquid containing anthrax bacteria that had been heated enough to weaken, but not kill the bacteria. A second herd of 100 cows was injected with the same liquid, minus the bacteria. A few weeks later, the scientists injected both herds of 100 cows with full strength anthrax bacteria. The cattle that had been previously injected with weakened bacteria showed no symptoms of the disease. The cattle from the second herd, however, became ill with anthrax and died.

1. What hypothesis was being tested in this experiment?

2. Why were both groups of cattle injected, even though one group didn’t receive any bacteria in the injection?

3. A Senator from the Armed Forces Appropriations Committee paid a visit to Fort Dietrich to evaluate the experiments. The Senator was critical of the large number of animals being used and suggested that it would b e cheaper to use only 10 animals in each group. How would you respond to the Senator?

Answer 1

1. The hypothesis being tested was that whether the animals could develop immunity against the anthrax bacteria if they were injected with the weakened germs. This is the same as vaccination. Vaccines are a small dose of weakened germs injected into a healthy person to trigger the immune system so that it could produce antibodies which would recognize and counter that particular germs when they actually infect the person.

The cows which were injected with the wakened anthrax germs developed immunity against the anthrax bacteria. This was possible because their immune system was activated and armed against those germs.

So, when they were actually injected with a full strength anthrax bacteria, they did not show any symptom of the disease.

The cattle from the second herd, who were not injected with the weakened germs, had not developed the immunity so, they became ill and died.

2] Both the herds were injected with the same liquid but the first one contained weakened anthrax bacteria while the second one did not. This was done to prove that it was the weakened bacteria that would develop the immunity in the cattle and not the liquid.

So, the liquid was used as the control in the experiment.

3] It is important to use a substantial number of specimen in any study or experiment to prove the viability of the study. A larger number of the population of cattle used in the experiment will give more authenticity to the study as chances of error will be reduced. So, the scientists at the institute will have to explain to the senator why they have to use a large number of cattle in their experiment and justify their point by explaining the technicalities of the experiment that they have conducted.