Carl was excited. It was his first delivery as a senior veterinary student, and
although the instructor was there, Carl was in charge. The delivery was a difficult
one, and the result was a sickly-looking calf, but Carl still felt the adrenaline
rush. He didn’t even notice the tear in his glove and the scraped skin beneath
it as he helped clean the calf off and took its vital signs.
The calf was still alive a week later when Carl thought he was coming down with the flu. He had a headache and a fever and felt exhausted. A couple of days later he received a call from the County Health Department. The calf had died and its tissues had been examined. It had been infected with Brucella abortus Strain RB51, the vaccine strain of Brucella abortus. The cow had been pregnant when it was vaccinated, and the calf was infected in utero. Carl was tested and diagnosed with Brucellosis (undulant fever); he began immediate antibiotic treatment.
Brucellosis is caused by infection with Brucella abortus and other Brucella strains. It is predominantly a disease of animals: cows, sheep, goats, elk, pigs, and dogs. Humans are usually infected by contact with body fluids or by drinking unpasteurized milk from infected animals. Brucellosis is uncommon in the United States (100-200 cases a year). It is usually contracted from cattle or by hunters from butchering infected elk. Some of the bison in Yellowstone National Part are also infected.
Brucella abortus is a small Gram negative coccobacillus (very short rod). It is easily phagocytosed, but it is resistant to killing inside the phagocyte because it blocks fusion of the phagososme and the lysosome. Brucella can grow and replicate inside phagocytes, eventually killing them. It is spread this way into the lymph nodes and then throughout the body. Brucella is sensitive to some antibiotics. The vaccine strain is a live bacterium that can infect humans.
Using the information given above and in your text, answer the following questions as completely as possible.
1. How was Carl infected with Brucellosis? What would be the initial site of infection?
2. Describe in approximate chronological order the steps in Carl's innate response to Brucella. Include both the cells and the molecules that are involved in the response to the bacteria and what each does. Be as complete as you can. Bulleted list OK.
3. What characteristics of Brucella abortus (as described in the case) would either help the innate immune system eliminate the bacterium or limit the effectiveness of innate immunity?
4. From your reading of Chapter 1, what effector cells and molecules from adaptive immunity would probably be needed to fight a Brucella infection? Say what each of these cells and molecules would do. Bulleted list OK
OPTIONAL additional information about Brucellosis: http://www.cdc.gov/ncidod/dbmd/diseaseinfo/brucellosis_g.htm
Answer the questions and save as a Word document entitled YourNameExam1.doc. Send to jdecker@u.arizona.edu as an email attachment or in the body of the email by 10 AM Monday June 14. Make sure your name is in the document as well as in the title.