Human granulocytic ehrlichiosis in Europe

Abstract

Ehrlichiosis comprises a group of emerging tick-borne infectious diseases caused by obligate intracellular Gram-negative bacteria that infect leukocytes. Infections caused by members of the genus Ehrlichia have been described in animals and humans, but to date there are no convincing reports of the presence of other types of human ehrlichiosis different from human granulocytic ehrlichiosis (HGE) in Europe. The European vector is the same as that of Lyme borreliosis, the hard tick Ixodes ricinus, and HGE has a similar epidemiology to that of Borrelia burgdorferi infection. Across Europe, I. ricinus is infected to a variable extent (0.4-66.7%) with the causative agent Ehrlichia (Anaplasma) phagocytophila genogroup, and since its first description in Slovenia in 1997, details of 15 patients have been published. Diagnosis requires careful consideration of all circumstances and symptoms (history of tick bite and the presence of a flu-like syndrome with variable degrees of anemia, thrombocytopenia, and leukopenia, and elevated liver enzymes). Some differences can be seen between US and European HGE patients. European HGE cases have a less severe course, and the presence of morulae is uncommon. In Europe, verification of HGE has been based on PCR and immunofluorescence antibody tests, because no isolation from humans has been reported.

Update on tick-borne bacterial diseases in Europe

“…By the end of December 2004, at least 2,871 cases of HGA were reported from 13 U.S. states to the Centers for Disease Control and Prevention (CDC) (Bakken & Dumler, 2008). In 2002, Blanco and Oteo (Blanco & Oteo, 2002) compared the clinical and laboratory features of 15 European patients to those reported for U.S. patients. Most patients report exposure to ticks or a tick bite between seven and 30 days before the onset of the disease.…”

“…Laboratory findings included leukopenia (16/24; 66.7 %), thrombocytopenia (20/24; 83.3 %), abnormal liver function (23/24; 95.8 %), elevated erythrocyte sedimentation rates (18/24; 75 %), and elevated concentrations of C-reactive protein (23/24; 95.8 %) (Lotric-Furlan et al, 2006). In Europe, verification of HGA has been based on PCR and immunofluorescence antibody tests, because no isolation of the etiologic agent from humans has yet been reported (Blanco & Oteo 2002).…”

Reservoir Competence of the Redwood Chipmunk (Tamias Ochrogenys) forAnaplasma Phagocytophilum

“…Reported reservoirs are whitefooted mice (Peromyscus leucopus) in the eastern United States (Telford et al 1996), woodrats (Neotoma fuscipes) and squirrels (Sciurus spp.) in the western United States (Nicholson et al 1999;Foley et al 2002;Nieto and Foley 2008), and bank voles (Myodes glareolus) and wood mice (Apodemus agrarius) in the Europe and Asia (Blanco and Oteo 2002;Bown et al 2003;Cao et al 2006).…”

Prevalence of Anaplasma phagocytophilum and its coinfection with Borrelia afzelii in Ixodes ricinus and Ixodes persulcatus ticks inhabiting Tver Province (Russia) – a sympatric region for both tick species

“…Since then, the number of patients has increased in the United States (Dumler et al, 2005). In Europe, the first human cases of this disease were described in 1997 (Petrovec et al, 1997), and serological and PCR analyses suggest that A. phagocytophilum is distributed throughout Europe and in some parts of the Middle East and Asia (Blanco & Oteo, 2002;Cao et al, 2000;Heo et al, 2002;Keysary et al, 1999). LB is the most common tick-borne infectious disease in the Northern Hemisphere (Masuzawa, 2004;Steere, 2001).…”

“…Prevalence rates of A. phagocytophilum in I. ricinus were found to be different among European countries (Blanco & Oteo, 2002). In Russia, A. phagocytophilum were detected from I. ricinus ticks collected in the Baltic region (Alekseev et al 2001) and from Ixodes persulcatus ticks collected in Vologda Province (Eremeeva et al, 2006), in Western Siberia (Rar et al, 2005), and in a survey area from the Urals to the Far East of Russia (Shpynov et al, 2006).…”