Anti-Hepatozoon canis serum antibodies and gamonts in naturally-occurring canine monocytic ehrlichiosis Mathios E. Mylonakis a , Leonidas Leontides b , Liat Gonen c , Charalambos Billinis d , Alexander F. Koutinas a, * , Gad Baneth c a Clinic of Companion Animal Medicine, School of Veterinary Medicine, Aristotle University of Thessaloniki, P.O. Box 16039, GR-54627, Thessaloniki 54401, Greece b Laboratory of Epidemiology, Biostatistics and Economics of Animal Production, School of Veterinary Medicine, University of Thessaly, GR-43100, Karditsa, Greece c School of Veterinary Medicine, Hebrew University of Jerusalem, Rehovot 76100, Israel d Laboratory of Microbiology and Parasitology, School of Veterinary Medicine, University of Thessaly, GR-43100, Karditsa, Greece Received 17 July 2004; received in revised form 30 December 2004; accepted 16 January 2005 Abstract The prevalence of IgG antibodies to Hepatozoon canis and the presence of gamonts in the blood and hemolymphatic tissues were studied in dogs with canine monocytic ehrlichiosis (CME) caused by Ehrlichia canis. Both pathogens are transmitted by the tick Rhipicephalus sanguineus. Forty-five out of 69 (65.2%) dogs with CME were seropositive to H. canis by an enzyme- linked immunosorbent assay (ELISA). Intra-neutrophilic gamonts of H. canis were found in 2 out of 69 dogs (2.9%) comprising 4.5% of the seropositive dogs. The present study indicated that the prevalence of antibodies to H. canis was high among dogs with CME in an area where both infections are endemic. However, previous exposure to H. canis was not found as an important contributor to clinical or clinicopathologic abnormalities found in dogs with CME. # 2005 Elsevier B.V. All rights reserved. Keywords: Dog; Ehrlichia canis; Hepatozoon canis; Co-infection 1. Introduction Hepatozoon canis infection has a global distribution (Kontos and Koutinas, 1990; Murata et al., 1993). This protozoan parasite is transmitted by infected Rhipice- phalus sanguineus ticks (Baneth et al., 2001). In two serosurveys for H. canis involving the general canine population, the seroprevalence was 33.1% in Israel (Baneth et al., 1996) and 4.2% in Japan (Inokuma et al., 1999). Studies on the prevalence of H. canis parasitemia in different regions of the world have shown a range from 1 to as high as 39.2% (Ezeokoli et al., 1983; Rajamanickam et al., 1984; Baneth et al., 1996; O’Dwyer et al., 2001). The pathogenicity of H. canis has been questioned, since sub-clinical infections, www.elsevier.com/locate/vetpar Veterinary Parasitology 129 (2005) 229–233 * Corresponding author. Tel.: +30 2310 994503; fax: +30 2310 994516. E-mail address: sanimed@vet.auth.gr (A.F. Koutinas). 0304-4017/$ – see front matter # 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.vetpar.2005.01.012