Human (Granulocytic) Anaplasmosis (HGA ... - Allina Health

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Laboratory-based diagnostic methods: Test Turnaround Time Sensitivity Comments LAB 453/EHL Ehrlichia Smear Identification of morulae in neutrophils or monocytes. LAB 2780/EDP Ehrlichia/Anaplasma PCR Detects and differentiates DNA of Anaplasma phagocytophilum, Ehrlichia chaffeensis, Ehrlichia ewingii, and Ehrlichia muris-like Same day Performed at Allina Medical Laboratories 1-3 days Test Referred to Mayo Medical Labs 20-80% sensitivity during the first week of infection 60-70% sensitivity during first week of illness. A positive test result is helpful but a negative test result does not rule out disease. This is an insensitive method (although dazzling when it works). A negative examination should NOT dissuade you from initiating treatment if the clinical presentation and routine laboratory findings support the diagnosis of HGA. Test of choice for Ehrlichia muris-like organisms. Treatment should not be withheld due to a negative result. This test should not be used to test asymptomatic individuals. LAB 2785/EHR Ehrlichia Antibody Panel Detects IgG and IgM antibodies to Ehrlichia and Anaplasma. 1-3 days Test Referred to Mayo Medical Labs 94-100% sensitivity after 14 days. Antibodies may not be detectable during the first week of illness (when patients typically present for treatment). A positive titer indicates current or past infection. Paired sera should be collected 2-3 weeks apart. A four fold rise in titer confirms acute infection. 4
BABESIOSIS Babesiosis (originally called “Nantucket fever” due to its initially recognized occurrence in the late 1960s on Nantucket Island) is a malaria-like illness caused by an apicomplexan protozoan. These organisms are found worldwide. Although there are many species, only a few are identified as causing human disease, including: B. microti, B. divergens, B. duncani (WA1 species), and a strain designated MO-1. Like malaria, Babesia species infect erythrocytes, but unlike malaria, babesiosis is transmitted by ticks, and the organism is found in a variety of animal species that serve as reservoirs. Our previously mentioned “friend” Ixodes scapularis (deer tick, blacklegged tick) is the usual tick vector. Human infections in the United States of America occur mainly in the upper Midwest and northeastern states due to infection by the rodent parasite Babesia microti (which infects the white-footed mouse and other small mammals and which is the main species that infects people in the United States). Tick larvae hatch in early summer from eggs laid in the spring by adult female ticks, and become infected when they take a blood meal from infected whitefooted mice. They molt into infected nymphs the following spring, and when they feed on mice or humans in late spring or early summer, these hosts then also become infected. The parasite is usually spread to humans by the young nymph stage of the tick (at which time the tick is about the size of a poppy seed). In the fall, the nymphs molt into adults that feed on white-tailed deer (that, according to some sources, do not become infected but nevertheless support/amplify the tick population by providing the blood meals); if these infected adult ticks feed instead on humans, they can infect humans at this time, as well. Thus, the main mode of transmission to humans is through the bite of an infected tick (usually nymph, sometimes adult), when humans engage in outdoor activities where Babesiosis is found. In human infection, the sporozoites which are introduced into the bloodstream by the biting tick attach to and enter the red blood cells (erythrocytes), where they mature into trophozoites that eventually bud to form four merozoites (these stages are visible via light microscopy, the four-merozoite stage sometimes characterized by the so-called “Maltese cross” formation in infected red blood cells). Babesia microti infection, Giemsa-stained thin smear 5
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Human (Granulocytic) Anaplasmosis (HGA ... - Allina Health

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