Anaplasma phagocytophilum in Ruminants in Europe

Abstract

The agent that causes tick-borne fever (TBF) in sheep was first described in 1940, 8 years after the disease was first recognized in Scotland. The same agent was soon shown to cause TBF in sheep and pasture fever in cattle in other parts of the UK, Scandinavia, and other parts of Europe. After the initial use of the name Rickettsia phagocytophila, the organism was given the name Cytoecetes phagocytophila to reflect its association with granulocytes and its morphological similarity with Cytoecetes microti. This name continued to be used by workers in the UK until the recent reclassification of the granulocytic ehrlichiae affecting ruminants, horses, and humans as variants of the same species, Anaplasma phagocytophilum. TBF and pasture fever are characterized by high fever, recurrent bacteremia, neutropenia, lymphocytopenia, thrombocytopenia, and general immunosuppression, resulting in more severe secondary infections such as tick pyemia, pneumonic pasteurellosis, listeriosis, and enterotoxemia. During the peak period of bacteremia as many as 90% of granulocytes may be infected. The agent is transmitted transtadially by the hard tick Ixodes ricinus, and possibly other ticks. After patent bacteremia, sheep, goats, and cattle become persistently infected "carriers," perhaps playing an important role in the maintenance of infection, in the flock/herd. Little is known about how efficiently ticks acquire and maintain infection in ruminant populations or whether "carrier" domestic ruminants play an important role as reservoirs of infection, but deer, other free-living ruminants, and wild rodents are also potential sources of infection. During the late 1990s serological evidence of infection of humans was demonstrated in several European countries, creating a renewed interest and increased awareness of the zoonotic potential of TBF variants. More recently, a few cases of human granulocytic anaplasmosis (HGA) have been reported in some European countries, but it remains to be established whether the variants causing HGA in Europe are genetically and biologically different from those causing TBF in ruminants. TBF is readily diagnosed by demonstrating intracytoplasmic inclusions in peripheral blood granulocytes or monocytes of febrile animals or by detecting specific DNA by polymerase chain reaction (PCR), and TBF variants of A. phagocytophilum can be cultivated in tick cell lines, but the differentiation of TBF variants from HGA variants awaits further investigations.

PCR detection of re-emerging tick-borne pathogen, Anaplasma phagocytophilum, in deer ked (Lipoptena cervi) a blood-sucking ectoparasite of cervids

“…Anaplasma phagocytophilum DNA and/or antibodies have been detected in humans (e.g., Chen et al 1994;Lotric-Furlan et al 1998;Blanco & Oteo 2002;Petrovec et al 1997;Kocianová et al 2008;Nováková et al 2010, etc. ) and in wide range of animals worldwide (e.g., Stuen et al 2003;Stuen et al 2007;Woldehiwet et al 2006). In Europe, red deer (Cervus elaphus) and roe deer (Capreolus capreolus) are considered as persistently infected with A. phagocytophilum and serve as the source of infection in natural foci (Liz et al 2002;Petrovec et al 2002;Polin et al 2004;Smetanová et al 2006;de la Fuente et al 2008;Štefanidesová et al 2008, etc.).…”

“…Transovarial transmission of these bacteria has not been observed yet. For the circulation and maintenance of the pathogen in natural foci the presence of competent as well as susceptible hosts is necessary (Woldehiwet 2006). Anaplasma phagocytophilum DNA and/or antibodies have been detected in humans (e.g., Chen et al 1994;Lotric-Furlan et al 1998;Blanco & Oteo 2002;Petrovec et al 1997;Kocianová et al 2008;Nováková et al 2010, etc.…”

Longitudinal field study on bovine Babesia spp. and Anaplasma phagocytophilum infections during a grazing season in Belgium

“…In cattle, A. phagocytophilum cause bovine granulocytic anaplasmosis (BGA), also called tick-borne fever (TBF), (Woldehiwet 2006). The symptoms associated with BGA are fever, a drop in milk production, joint swelling and abortion.…”

“…A. phagocytophilum causes hematologic changes characterized by bacteremia, leukopenia, and thrombocytopenia. The loss of white blood cells promotes suppression of the immune response and causes infected humans or animals to be more susceptible to other infectious pathogens (Woldehiwet 2006).…”

Anaplasma phagocytophilum and other tick-borne bacteria in wild animals in western Slovakia

“…Anaplasmosis caused by A. phagocytophilum is a disease of medical and veterinary interest with various clinical manifestations ranging from subclinical to life-threatening (Bakken & Dumler 2000). Since its discovery in the United States, and subsequently in Europe, various mammal species were implied as reservoirs and hosts of A. phagocytophilum (de la Fuente et al 2005;Woldehiwet 2006). High prevalences were detected especially in several species of deer.…”