Question

Upon completion of your nursing degree, you decided to try the country life, and moved to a rural town in West Virginia, working for a small family practice. Around mid-September, a man in his late 40’s comes in to your office. He has been suffering from an intermittent headache with a fever of 102-103°F for the past two weeks. The physician arrives while you are completing his vitals (nothing abnormal was noted). The physician takes the man’s history, and performs a physical exam. The only clinical findings were a wound in late stages of healing on his left thumb and swelling of the axillary lymph nodes that were tender. When asked about the cut, the man replied that he cut himself skinning a rabbit some three weeks ago. Based on these findings, the physician orders blood to be drawn now and again in 4 weeks, prescribes a ten day regiment of streptomycin and orders the patient to come back if his symptoms don’t get better after 1 week.

1) Based on the limited information above, the physician has made a diagnosis. What is it? What does it look like when gram stained?

2) What is the most likely reservoir of the causative agent in this case?

3) Why did the physician order blood to be drawn twice?

4) As part of the staff at the practice, there is a part time clinical microbiologist. Should they attempt to culture the microbe to confirm the diagnosis? Explain.

5) Infections like this one are zoonotic. Define zoonotic and list two additional zoonotic infections and their causative agents.

Answer 1

1) The physician diagonosed the patient is infected with bacteria Francisella tularensis, which cause Tularemia infection.

Tularemia infection is also called Fransis disease or Rabbit fewer or dee-fly fewer is transmitted by contact with the F. tularensis infected animals like rabbits, rodents . Francisella tularensis is a gram negative aerobic bacteria and gives negative result for gram staining showing a pink color.

2) The main causative agents of this disease is infected animals like rabbits and rodents or by infected tick bite or even from exposure while handling infected dead animals.

3)The physician ordered blood to be drawn twice one on the first day and after 4 weeks because during early stage of tularemia infection , only few antibodies may be detected. Antibody production increases during the course of infection and so a second blood test usually after 4 weeks is done again.

4) F.tularensis culture is not preferred diagnostic method because it is very difficult to culture and is very slow growing bacteria, so when a rapid result is required it is not feasible and also due to the risk associated with the laboratory work which requires a biological safety cabinet.

Usually serological test like latex agglutination or ELISA which show an increase in both IgM and IgG is done to diagnose the disease.

5) Zoonotic diseases are diseases which passed from infected animals to human.

Two examples of zoonotic infections are Rabies and Plague. Rabies is spread to human by the bite or scraching of animals mainly dogs which are infected with Rabies virus or Rabies lyssavirus. Plague is another zoonotic disease spread to human through infected rodent flea that is carrying plague bacterium Yersinia pestis.