Anaplasmosis

This article is about the ruminant disease. For anaplasmosis in dogs, see Ehrlichiosis (canine). For anaplasmosis in humans, see Human granulocytic anaplasmosis.

Anaplasmosis
Classification and external resources
MeSH	D000712

Anaplasmosis is a disease caused by a rickettsial parasite of ruminants, Anaplasma spp. The organism occurs in the red blood cells and is transmitted by natural means through a number of haematophagous species of ticks. It can also be transmitted iatrogenically by the use of surgical, dehorning, castration, and tattoo instruments and hypodermic needles that are not disinfected between uses.

Although the term is often associated with animal infection, it is also used to describe infection in humans.

Life cycle

The organism can go through a complete lifecycle in the gut of certain species of ticks but the flies appear to be only a mechanical vector, thus, not as important in maintaining the disease in any given area. The disease causes severe anemia and wasting in infected adult cattle. Young cattle and most other ruminants will not show clinical signs if infected but may serve as carriers.

Distribution

In the United States, anaplasmosis is notably present in the south and west where the tick hosts Ixodes spp. are found. Although vaccines have been developed, none are currently available in the United States. Early in the 20th century, this disease was considered one of major economic consequence in the western United States. In the 1980s and 1990s, control of ticks through new acaricides and practical treatment with prolonged-action antibiotics, notably tetracycline, has led to the point where the disease is no longer considered a major problem.

Cases of coinfection with tick-borne microorganisms are being increasingly reported in the last decade, perhaps explaining the variable manifestations and clinical responses noted in some patients with tick-transmitted diseases. In such clinical settings, laboratory testing for coinfection is indicated to ensure that appropriate antimicrobial treatment is given.

In 2005, Anaplasma ovis was found in reindeer populations in Mongolia. This pathogen and its associated syndrome (characterized by lethargy, fever and pale mucous membranes) was previously only observed in wild sheep and goats in the region, and is the first observed event of A. ovis in reindeer.

In Australia, bovine anaplasmosis, caused by Anaplasma marginale, is only found in the northern and eastern parts of Australia where the cattle tick is present. It was probably introduced as early as 1829 by cattle from Indonesia infested with the cattle tick Boophilus microplus.

Clinical signs and diagnosis

Anaemia may be severe and result in cardiovascular changes such as an increase in heart rate. Haematuria may occur due to the lysis of red blood cells. General systemic signs such as diarrhea, anorexia and weight loss may also be present. A blood smear stained with Giemsa should be observed for identification of infected red blood cells and will allow definitive diagnosis.

Treatment and control

Treatment usually involves a prescription of doxycycline or a similar class of antibiotics. Oxytetracycline and imidocarb have also been shown to be effective. Supportive therapy such as blood products and fluids may be necessary.

Vaccines against anaplasmosis are available. Carrier animals should be eliminated from flocks. Tick control may also be useful although it can be difficult to implement.

Notable cases

On July 30, 2009, David Letterman announced that he had been infected with anaplasmosis. He believes he was most likely bitten by an infected tick while camping with his 5-year-old son in their tree house.

External links

• CFIA Animal Disease Information
  • Anaplasmosis fact sheet
  • Biosecurity training video
  • Farm-level biosecurity practices