Historical Background of Human Ehrlichiosis - Essay Example

appears here] appears here] appears here] appears here] Human Ehrlichiosis Introduction to Disease/Historical Background Human ehrlichiosis was first described in the United States in 1986. Since then, more than 215 cases have been reported, including some fatalities. Ehrlichia species belong to the same family as the organism that causes Rocky Mountain spotted fever. Human ehrlichiosis occurs most frequently in the southern mid-Atlantic and south-central states, during spring and summer months. The clinical presentation is similar to that seen in Rocky Mountain spotted fever although, with ehrlichiosis, leukopenia is more often found and skin rash is less often rioted. Definitive diagnosis is based on acute and convalescent serum antibody titers. Ehrlichiosis cannot reliably be distinguished from other common febrile illnesses on the basis of clinical, epidemiologic or laboratory features. Therapy must be initiated empirically in suspected cases. Both ehrlichiosis and Rocky Mountain spotted fever respond well to tetracycline and chloramphenicol, but not to penicillins or cephalosporins. (Bolan, Charles D, 1992) Ehrlichiosis is caused by rickettsiae like organisms, which are intracellular parasites. Co-infection with babesiosis and/or Lyme disease may occur. Human monocytic ehrlichiosis is caused by Ehrlichia (E.) chaffeensis. (David A. Poirier, Kenneth L. Feder, 2001) Method of Transmission Ehrlichiosis is transmitted by the bite of infected ticks, including the deer tick and the lone star tick. Ehrlichiosis cannot be spread from person to person. www.health.state.ny.us/nysdoh/communicable_diseases/en/erlich.htm The American dog tick, lone star tick, and probably the Western black-legged tick transmit the infection. Most cases are reported from the south central and southeastern United States. Human granulocytic ehrlichiosis is a related variation that is probably caused by an E. equi- related strain. It's transmitted by the black-legged tick and probably the Western black-legged and American dog ticks. Cases have been found nationwide. (David A. Poirier, Kenneth L. Feder, 2001) The epidemiology, response to antibiotics and clinical characteristics of human ehrlichiosis and Rocky Mountain spotted fever are similar but not identical, and these diseases must be differentiated from other febrile illnesses in patients who have a history of possible tick exposure. The diagnosis is currently based on antibody response in acute and convalescent sera and cannot be made with certainty on the basis of clinical features alone. Therefore, appropriate antibiotic therapy must be initiated empirically. (Bolan, Charles D, 1992) Etiology In the United States, human ehrlichioses may be caused by at least 3 distinct species of obligate intracellular bacteria. Human monocytic ehrlichiosis results from infection with E chaffeensis. Human granulocytic ehrlichiosis is caused by A phagocytophila and E ewingii. Ehrlichia species are gram-negative cocci that measure 0.5 to 1.5 m in diameter. http://aapredbook.aappublications.org Typical signs and symptoms Fever, malaise, headache, chills, severe muscle aches/pain, vomiting, anemia, lung infection, decrease in white blood cells, decrease in platelets, and elevated liver enzymes. A rash occurs in a small percentage of people. Neurologic symptoms include seizures, encephalopathy, meningitis, confusion, atazia, and change in mental status. Symptoms can also be nonspecific. (David A. Poirier, Kenneth L. Feder, 2001) Complications Symptoms typically last 1 to 2 weeks, and recovery generally occurs without sequelae; however, reports suggest the occurrence of neurologic complications in some children after severe disease. Fatal infections have been reported. Secondary or opportunistic infections may occur in severe illness, resulting in possible delayed recognition of ehrlichiosis and appropriate antimicrobial treatment. People with underlying immunosuppression are at greater risk of severe disease. http://aapredbook.aappublications.org Prognosis A timely diagnosis of ehrlichiosis is based on clinical findings. Appropriate treatment must never be withheld pending confirmation of the diagnosis. Numerous studies have clearly demonstrated that progressively longer delays in diagnosis are associated with progressively worse, or even fatal, clinical outcomes. Confirmation of the diagnosis can be obtained using serology and PCR amplification of the 16S rDNA. While methods of culturing Ehrlichia have improved, the process presently remains too prolonged (five to 12 days), too unavailable and too unreliable to be of clinical assistance in most cases. Serology uses an indirect fluorescent antibody (IFA) method and must include antigens to E. chaffeensis and E. equi. Since these organisms have many antigenic differences, a test for one organism will generally not detect the other. Traditionally, the diagnosis is made by comparison of paired acute and convalescent sera, showing a four-fold rise or fall with peak titer at least 1:64 or single titer at least 1:128. Obviously, this information comes too late to be of use in treatment, and an antibody response may never even develop in patients given tetracycline within the first 24 hours of illness. PCR, while faster and more sensitive than IFA, is generally not available in most laboratories, so blood samples must be sent to either local or state health departments, the CDC or a few selected research laboratories. (Weinstein, Raymond S, 1996) Medications and Nursing Care The effectiveness of tetracycline has been confirmed by both in vitro testing and in vivo observation, and this drug should be the treatment of first choice for ehrlichiosis. Doxycycline is the antibiotic used in most published reports. At this time, all published studies have been uncontrolled and retrospective, and no controlled clinical trials have looked at the effectiveness of the various antibiotics. Even so, no one disagrees that a tetracycline should be the first-line treatment of choice. Much controversy surrounds the question of which antibiotics constitute appropriate alternative therapy. Because of its effectiveness in other rickettsial diseases, chloramphenicol (Chloromycetin) has been used empirically in many patients with ehrlichiosis, and its use is sometimes advocated as an alternative therapy. Unfortunately, little scientific evidence supports this use, and a number of studies have demonstrated the ineffectiveness of chloramphenicol against Ehrlichia both in vitro and in vivo. (Weinstein, Raymond S, 1996) A danger exists of misinterpreting findings and drawing inaccurate conclusions when using retrospective reviews with no control group, in trying to determine the best treatment for a disease such as ehrlichiosis. The natural, untreated course of the illness is highly variable and incompletely known, making a valid interpretation of such studies difficult. One study shows that patient's defervesce in three days with chloramphenicol therapy compared with two days with tetracycline therapy and a median of seven days in patients treated with other antibiotics. Unfortunately, because most of these patients were treated with multiple antibiotics, such an analysis was difficult. (Weinstein, Raymond S, 1996) An earlier study that also recommends chloramphenicol as alternative therapy suffers from similar problems. Interestingly, that study reports on two patients who received no antibiotic therapy throughout the course of their ehrlichiosis. One patient defervesced in only two days, while the other's fever lasted 15 days. This, at least, demonstrates that even without treatment, fever may last only two days. In addition, seroconversion without apparent clinical illness has been well documented and may occur in up to 67 percent of all cases of ehrlichiosis. (Weinstein, Raymond S, 1996) Other antibiotics that demonstrated little or no efficacy against ehrlichia, in vitro or in vivo, are gentamicin (Garamycin), ceftriaxone (Rocephin), ciprofloxacin (C)pro), trimethoprim/sulfamethoxazole (Bactrim, Cotrim, Septra), erythromycin, metronida zole (Flagyl), clindamycin (Cleocin), penicillin and the sulfonamides. The susceptibility of Ehrlichia to rifampin (Rifadin, Rimactane) has been demonstrated by in vitro testing but has not yet been clinically tested. In addition, while ciprofloxin was not found to be bactericidal, in vitro testing showed it to be bacteriostatic. This also has not been clinically tested. (Weinstein, Raymond S, 1996) Tetracycline, 500 mg four times a day, or doxycycline, 100 mg twice a day (in children: 3 to 4 mg per kg per day in two divided doses), either orally or intravenously for 10 to 14 days, should be started in any patient suspected of having ehrlichiosis, unless tetracycline is absolutely contraindicated. Even in children, the risk of mild dental discoloration that accompanies tetracycline therapy must be weighed against the severity and potential lethality of ehrlichiosis, and tetracycline therapy should be considered if defervescence does not occur within the expected two to three days of therapy with a secondary agent. When tetracycline is absolutely contraindicated, rifampin, 600 mg per day, or chloramphenicol, 500 mg four times a day, may be tried, although the efficacy of these agents in ehrlichiosis has not been clearly established. No evidence supports the prophylactic use of antibiotic in patients with known tick bites. (Weinstein, Raymond S, 1996) Prevention Prevention is always preferable to treatment, and avoidance of ticks is the best means for preventing all tick-borne diseases. Prevention can be accomplished by using insect repellent, wearing long pants and long-sleeved shirts whenever venturing into potentially tick-infested areas, and performing a thorough search of skin, hair and clothing for ticks after a walk through wooded or brush-covered areas. Reference: Bolan, Charles D, 1992. Human ehrlichiosis: a newly recognized tick-borne disease. American Family Physician David A. Poirier, Kenneth L. Feder, 2001. Dangerous Places: Health, Safety, and Archaeology; Bergin and Garvey, 2001 Weinstein, Raymond S, 1996. Human ehrlichiosis. American Family Physician http://aapredbook.aappublications.org www.health.state.ny.us/nysdoh/communicable_diseases/en/erlich.htm Read More