May Case Study
This month we are focusing on tick-borne diseases thanks to Dr. Chris Case of Skyline College. I've linked to some interesting sites in the list below. Further down the page is a good case study. See if you can sleuth this one. Hope you enjoy the page! Case reports are edited by NCASM, but not peer-reviewed. They are provided by NCASM members for educational purposes.
The most common tick diseases in the U.S.A.
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Case study:
1. On April 10, a 2-year-old girl who resided in Asotin County, Washington, was taken to the emergency department of a regional hospital because of a 2-day history of unsteady gait, difficulty standing, and reluctance to walk. On physical examination she was afebrile, alert, and active but could stand only briefly before requiring assistance. She exhibited ascending weakness and loss of reflexes that affected both sides of her body. Cranial nerve function was intact. Within several hours of hospitalization, she had onset of drooling and tachypnea.
What diseases are possible? What additional information do you need?
2. Protein levels in her cerebrospinal fluid were normal. Other than a recent history of cough, the patient had been healthy and had not been injured. She has not been given aspirin.
Do you need to modify your hypothesis based on this information?
4. A complete blood count showed a white blood cell count of 10,000/mm3, with 56% neutrophils, 3% band forms, and 30% lymphocytes, and 27% eosinophila. Her red blood cell count was 4.2 x 106/mm3.
Can you eliminate any diseases at this point?
5. A nurse incidentally detected an engorged tick on the girl’s hariline by an ear.
What should the nurse do?
6. Prompt removal of the feeding tick is essential. Ticks can be removed using forceps or tweezers to grasp the tick as closely as possible to the point of attachment. Removal requires the application of even pressure to avoid breaking off the body and leaving the mouth parts imbedded in the host. Gloves should be worn if a tick must be removed by hand; hands should be promptly washed with soap and hot water after removal of a tick.
Why is identification of the tick important?
7. The tick was not available for identification. However, vector-borne diseases are often arthropod-specific and prompt identification of the tick can provide information for diagnosis and treatment. Within seven hours after tick removal, tachypnea subsided and reflexes were present but diminished. The patient recovered fully and was discharged on April 11.
What disease did the patient have? How do you know?
8. Tick paralysis occurs worldwide and is caused by the introduction of a neutrotoxin elaborated into humans during attachment of and feeding by the female of several tick species. Onset of symptoms usually occurs after a tick has fed for several days. The pathogenesis of tick paralysis has not been fully elucidated. However, motor neurons probably are affected by the toxin, which diminishes release of acetylcholine. If unrecognized, tick paralysis can progress to respiratory failure and may be fatal in approximately 10% of cases. Prompt removal of the feeding tick usually is followed by complete recovery.
Why is surveillance and case-reporting of tick-borne diseases important in the United States?
9. In the United States, ticks transmit more vector-borne diseases that any other arthropod. In 1995, Lyme Disease was the ninth most frequently reported of the 52 diseases that are reportable to the Centers for Disease Control and Prevention, with 3.7 cases per 100,000 people.
Do you think ticks are carrying more diseases now than in the past? Discuss factors that have contributed to the increase in tick-borne diseases?
References:
D. H. Spach et al. "Tick-Borne Diseases in the United States."New England Joural of Medicine 329:936–947, Sept. 23, 1993.
CDC. MMWR 45:325–326, April. 26, 1996
Additional sites for surfing: Marin-Sonoma Mosquito and Vector Control, Rhode Island Tick Pickers, American Society for Rickettsology, University of Missouri.
Seen anything interesting in the lab lately? Submit case studies to Chuck Regeski.
This webpage was designed and
authored by Northern California ASM, which is fully
responsible for its contents. Please send comments or corrections to
Chuck
Regeski.
This page was originally created August 1997.
This page was last updated on
10/26/01.
This page was last updated on 10/26/01.