The answer to these questions requires knowledge of opportunistic infection and the normal microbial flora associated with the body. Mr Johnson’s problem probably occurred because of the suppression of his immune response. This suppression allows for the development of infections because of the lack of host defence. One of the common opportunistic infections is with fungi such as Pneumocystis.
Question A: The presence of oral thrush is an indicator of depressed or absent immune response. This immunodeficiency is apparent in one of the individuals but not the other indicating that only one may have this lack of immune capability.
Question B: There is no way to definitively prove why this would occur in one and not the other, but since both have similar backgrounds and have been in the same environment it could be possible that there could be a different problem going on in the immunocompromised individual.
Question C: The obvious worry would be that the patient with thrush might be infected with HIV and that he is beginning to show signs of AIDS. Since both men have been together for some time there is a possibility that the other man is also infected with HIV but has not yet shown signs of the infection. It is possible that the men are sexual partners or share needles. Both men should be tested and all contact with them should be according to the standard operating procedures used to treat AIDS victims.
This question involves the patient history and symptoms both of which are very important for making an accurate diagnosis.
Question A: The symptoms that the patient has described are common to infections of the digestive system, which could lead to a potential bacterial or viral infection of the digestive tract. However her history indicates extensive travel to Africa that opens the door for consideration of an intestinal parasite the symptoms of which would be similar to those she is experiencing.
Question B: The easiest way to find out if this type of parasitic infection is a possibility is by looking at the level of eosinophils in her blood. This white blood cell is increased in number in response to parasitic infection. An additional test that would be helpful in proving that a parasitic infection was ongoing would be examination of her stool for eggs. Remember that intestinal parasites will produce prodigious amounts of eggs in the stools of infected individuals.