Anaplasmosis [an-a-plas-mo-sis] and Ehrlichiosis [ehr-lich-i-o-sis] are caused by Anaplasma and Ehrlichia species, which are members of the rickettsiae and are obligate intracellular coccobacilli. The spectrum of disease caused by these species ranges from asymptomatic to fatal. Wild and domestic stock are some of the reservoir-competent hosts.Human Granulocytotropic Anaplasmosis (HGA), formally known as Human Granulocytic Ehrlichiosis (HGE), is caused by Anaplasma phagocytophilum. This organism is also responsible for Tick-borne Fever in both cattle and sheep, and can cause clinical disease in other animals. It parasitizes the white blood cells of its host, weakening the immune system.

Signs & Symptoms

The onset of clinical disease usually begins within 1-3 weeks of the tick bite. Early symptoms can be non-specific, including flu-like malaise, fever, chills and myalgias. More acute symptoms can include vomiting, acute weight loss, abdominal pain, cough, diarrhoea, haemorrages and renal failure.

Another ehrlichiosis that affects humans is Human Monocytic Ehrlichiosis (HME), which is caused by Ehrlichia chaffeensis. HME is clinically similar to HGA.

Testing

Generally an indirect immunofluorescence assay (IFA) is the principle test used, but Anaplasma / Ehrlichia species can also be identified in infected tissues by using immunohistochemical staining. Polymerase Chain Reaction (PCR) is increasingly used to detect Anaplasma / Ehrlichia DNA.

Treatment

Anaplasma and Ehrlichia infections generally respond to tetracycline antibiotics.

Medical Abbreviations

Vaccines

There is currently no vaccine against Anaplasmosis.