My Case Study Solution

Transcription

1 My Case Study Solution By Chiara Corey Amy and John, recent newlyweds and hiking enthusiasts from California, completed a backpacking road trip across the United States for their honeymoon. They started on the east coast, enjoying several days of hiking and camping along the Appalachian Trail. They took four weeks driving across country visiting many National State Parks and ending with the Pacific Crest Trail along the California coast. About one week into the trip Amy s backpack caused abrasions and a rash near the straps on her shoulder and thought nothing of it being that they were hiking with packs and showering a bit less than usual. She also was experiencing knee pain and John took on some of the weight of her pack on hikes to both alleviate rubbing where the rash was, and to avoid more pressure on her knee. While the trip was an amazing start to Amy and John s new life together, they both were quite sore and achy by the conclusion and decided to end the trip with massages for their sore muscles. While John was up and ready to get back to normal life quickly after their return, Amy was incredibly exhausted and her muscles continued to be sore and achy, even weeks after their trip. Amy needed to get back to work and so she started taking a pain reliever for her healing sore muscles and knee joint pain. After a couple weeks of continued joint pain, added fatigue, headaches, and the appearance of more rashes, Amy finally decided to make a doctor appointment. 1. Give a differential diagnosis of four infectious diseases Amy might have. For each, give your reasoning why it could be that disease and explain the likelihood of it being that one. Anaplasmosis is a tickborne disease that is often found in the northeast and upper midwestern United States. Symptoms include muscle aches, headache, fever, and a rash that rarely is present (12). Amy didn t report a fever but has many of the other symptoms. She may have been infected along her hike. Amy could have contracted another tickborne disease, Rocky Mountain spotted fever (RMSF) during her trip. The American dog tick and the Rocky Mountain wood tick are prevalent in south central US and other areas that Amy and John traveled to. Symptom onset begins at about 5 10 days and includes a classic rash (11). Another potential cause of Amy s symptoms could be fibromyalgia. Symptoms include widespread pain and fatigue that is chronic, lasting for a long time. Although the cause for fibromyalgia is unknown, it can be associated with a physically or emotionally stressful event (10). Amy s trip was certainly physically stressful and perhaps this triggered this response. Amy is most likely to have contracted Lyme disease based on her symptoms and exposure to the northeast where deer ticks that carry Lyme are located. The rash that Amy first experienced

2 on her trip was likely to have been erythema migrans, an early indication of Lyme that can appear anytime between 3 to 20 days after an infected tick bite. Other symptoms of Lyme that Amy presented where fatigue and body aches. The joint pain, especially in the knee, and the rash appearing in other parts of the body, and fatigue are symptoms of Lyme that has been present for weeks to months (5). Amy s doctor had suspicion of her illness based on her recent trip and symptoms and ordered a blood test for further confirmation. 2. Describe how Amy s disease is diagnosed and the recommended laboratory tests that are used to confirm diagnosis. Lyme disease diagnosis is often based on clinical representation of symptoms and exposure to blacklegged ticks. The signs and symptoms of Lyme disease include fever, chills, headache, fatigue, muscle and joint aches, and swollen lymph nodes. In addition, erythema migrans (EM) rash is present in about 70 to 80 percent of infected persons (1). Signs of Lyme disease that can be present months after a tick bite can include severe headache, joint pain, dizziness, nerve pain, facial palsy and additional rashes on other parts of the body. If the EM rash is present it is pathognomic of Lyme disease (2). There is no direct test for Lyme, however the CDC recommends a two-step indirect blood test for evidence of antibodies to react to any kind of Borrelia bacteria. The first step is an enzyme immunoassay, also called EIA or formerly ELISA. Less commonly an immunofluorescence Assay, called IFA, can be used. This first screening test detects the level of Lyme IgM or IgG in the blood (7). If this is negative then no further tests are recommended. If this step is positive or indeterminate then the second step called a Western blot test should be done. The Western blot detects IgM or IgG antibody levels (7). Results are only considered positive if both tests are positive (1). Amy s tests both came back positive. Explain why testing is done this way and the importance of an accurate diagnosis. A two-step test is done as symptoms of Lyme disease are nonspecific and are often found in many other conditions. Ticks that carry Lyme disease can often spread other diseases at the same time (5). The EIA test is considered insensitive as the bacteria, Borrelia, is fairly common as it also cause sinus and urinary tract infections (4). The Western blot is followed for more specificity, detecting antibodies of Borrelia burgdorferi bacterium. There is controversy over the effectiveness of testing for Lyme by these methods. The International Lyme and Associated Disease Society cites the EIA test as unreliable due to sensitivity, and states that Western blot should be performed by labs that test for all positive bands of Lyme, not just the CDC recommended bands of 31 and 34 (2).

3 If left untreated or undertreated, people with Lyme disease can experience more severe symptoms that impact quality of life and are often hard to resolve (2). The condition is often referred to as post-treatment Lyme disease (PTLD), post Lyme disease syndrome (PLDS), or chronic Lyme disease (CLD) (1, 3). What other infectious disease is found using the same testing method and why is it considered more reliable? The CDC also recommends a similar two-step testing process to diagnose HIV/AIDS. The sensitivity of diagnostic HIV testing is 99.5%, whereas Lyme disease patients tested at least 4 6 weeks after infection is only 44% to 56% according to reports published on lab sensitivity (6). Why would someone get a false negative? There are several reasons why someone may test negative for Lyme disease when they actually do have the disease. The accuracy of tests depend on the stage of the disease, as with other serologic tests for other infectious diseases, according to the CDC. In the early stages of Lyme disease the antibodies may not have developed and would not test positive on a screening EIA test. Antibodies usually take several weeks to develop and may yield a negative result if the test is done prior to 4 to 6 weeks of infection. If someone is tested who has already received antibiotics early in the disease, the antibodies may be too low to detect or did not develop at all (1). 3. Give the taxonomy for this microbe. Lyme disease is caused by the bacterium Borrelia burgdorferi, a microaerophilic spirochaetes. The disease was first found in 1975 in Old Lyme, Connecticut, and the bacteria was isolated by Willy Burgdorfer from blacklegged ticks (Ixodus scapularis and Ixodus pacificus) or deer ticks. Ticks can attach to any part of the body and in most cases, must be attached for hours or more before Lyme disease bacteria can be transmitted (1). Transmission can occur in any life stage but is most common to transmit during the nymph stage when the tick is small and difficult to detect. The tick is uninfected with the spirochaete until it feeds on an infected animal and continues to move on to infect more hosts (7). The main virulence factors of the bacteria include immune system avoidance by factors that reduce the effectiveness of the immune system to respond to an invader. The spirochaete virulence factors also include motility, adhesins, and chemotaxis (7). 4. Explain the epidemiology for Amy's disease. Lyme disease is concentrated heavily in the northeast and upper Midwest of the United States and instances of the disease have steadily increased. Lyme disease is the most commonly reported vectorborne illness in the United States and in 2015, 95% of confirmed cases were reported from 14 states. These states include: Connecticut, Delaware, Maine, Maryland, Massachusetts, Minnesota, New Hampshire, New Jersey, New York, Pennsylvania, Rhode

4 Island, Vermont, Virginia, and Wisconsin (1). It is estimated that Lyme disease infects 300,000 each year and was the sixth most common Nationally Notifiable disease in 2015 (1). 5. How is Amy s disease treated Lyme disease is treated with antibiotics and those who are treated in the early stages of the disease usually recover quickly and completely. Common antibiotics that are prescribed are doxycycline, amoxicillin, or cefurozime axetil are recommended for the adult patient and children over age 8, that shows early signs of the disease (2). A Later stage patients may require several courses of intravenous antibiotics lasting between 14 to 28 days (5). Are there any complications Without successful treatment, the bacterium can spread to other areas of the body, including the brain, where it can cause meningitis. Untreated Lyme can also lead to neurologic dysfunction. This can include paralysis of certain nerves, most commonly in the face known as Bell s palsy (4). Chronic joint inflammation, particularly in the knee, and cognitive defects, such as impaired memory are also complications (5). Lyme carditis can be fatal and impacts about 1% of Lyme cases and occurs when the bacteria enters the tissues of the heart and interferes with the normal movement of electrical signals (1). How is Amy s disease prevented? The best way to prevent exposure to Lyme disease is to not be in areas where deer ticks live, cover up and use insect repellent. Environmental measures can be taken such as keeping grass and bushes short, use deer fencing, and even use pesticides around the home (8). Personal preventative measures include frequently checking for ticks after being outside. Ticks are often found on the body in hidden areas like between the toes, back of the knees, armpits, and along the hairline. Pets should also be checked for ticks and use preventative medication to avoid exposure. If ticks are found, you should remove it with tweezers (8). Is there currently a vaccine available? There is no vaccine currently available for Lyme disease and there is one vaccine that recently received FDA clearance to begin clinical trials. The FDA approved a vaccine in 1998 called LYMErix that was delivered in three doses. The company that produced the vaccines claimed 80 percent effectiveness. In 2002, the vaccine was voluntarily withdrawn from the market citing low demand, however, there were many complaints and a class action lawsuit citing the vaccine caused harm (9).

5 References 1. Centers for Disease Control and Prevention. 9 May Lyme Disease Accessed May 3, International Lyme and Associated Diseases Society. About Lyme Accessed May 3, Lymedisease.org. Accessed May 3, Palermo, Elizabeth. 3 September Live Science. Lyme Disease: Symptoms and Treatment. Accessed May 6, Mayo Clinic. Lyme Disease. Accessed May 6, Johnson, L. Stricker, R Jan 7. Infection and Drug Resistance. Lyme Disease: The Next Decade. Accessed May 6, MicrobeWiki. Lyme Disease. Accessed May 11, Baker, D. 23 October Utah Department of Health. Lyme Disease. Disease Plan. Accessed May 10, Fisher, B.L. La Vigne, P. 26 January The Vaccine Reaction. FDA Gives Green Light to Test Lyme Disease Vaccines on Humans. Accessed May 11, National Institute of Arthritis and Musculoskeletal and Skin Diseases. July Accessed May 11, Columbia University Medical Center. Lyme and Tick-Borne Disease Research Center. Rock Mountain Spotted Fever. Accessed May 11, Centers for Disease Control and Prevention. 23 June Anaplasmosis. Accessed May 11, 2017.