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ehrlichiosis(ârlĭkēō`sĭs), any of several diseases caused by rickettsia of the genera Ehrlichia and Anaplasma. Ehrlichiosis is transmitted by ticks. Both human forms tend to develop about nine days after a tick bite. Symptoms include severe headache and chills and low white blood cell and platelet counts. The lack of a rash distinguishes them from Rocky Mountain spotted feverRocky Mountain spotted fever,
infectious disease caused by a rickettsia. The bacterium is harbored by wild rodents and other animals and is carried by infected ticks of several species that attach themselves to humans.
..... Click the link for more information. and Lyme diseaseLyme disease
or Lyme borreliosis,
a nonfatal bacterial infection that causes symptoms ranging from fever and headache to a painful swelling of the joints. The first American case of Lyme's characteristic rash was documented in 1970 and the disease was first identified
..... Click the link for more information. ; lack of upper respiratory and gastrointestinal symptoms distinguishes them from influenzainfluenza
acute, highly contagious disease caused by a RNA virus (family Orthomyxoviridae); formerly known as the grippe. There are three types of the virus, designated A, B, and C, but only types A and B cause more serious contagious infections.
..... Click the link for more information. . Many cases are mild, and all are treatable with antibiotics (tetracycline and doxycycline); however, ehrlichiosis can be fatal in some cases when diagnosis and treatment are delayed.
It was known for years that certain Ehrlichia species (some believe them to be variant strains of a single species) can cause disease in animals, for example E. canis and E. ewingii in dogs and E. phagocytophila in sheep and cattle. In the mid-1980s human ehrlichiosis was first recognized. The causative agent was found to be E. chaffeensis. This form is now known as human monocytic ehrlichiosis. In 1990 another form of the disease, human granulocytic ehrlichiosis, was identified. Althought the disease is now known as human granulocytic anaplasmosis (E. phagocytophilum, the causative agent, has been reclassified as Anaplasma phagocytophilum), the term ehrlichiosis continues to be used generically to describe the infection. Other species of Ehrlichia, such as E. ewingii, also cause ehrlichiosis in humans. The organisms invade various white blood cells (see bloodblood,
fluid pumped by the heart that circulates throughout the body via the arteries, veins, and capillaries (see circulatory system; heart). An adult male of average size normally has about 6 quarts (5.6 liters) of blood.
..... Click the link for more information. ; immunityimmunity,
ability of an organism to resist disease by identifying and destroying foreign substances or organisms. Although all animals have some immune capabilities, little is known about nonmammalian immunity.
..... Click the link for more information. ). E. chaffeensis commonly invades monocytes; A. phagocytophilum and E. ewingii invade granulocytes.