A New Hepatozoon Species from Dogs: Description of the Causative Agent of Canine Hepatozoonosis in North America

Abstract

A new species of Adeleina, Hepatozoon americanum, is described from the skeletal muscle, cardiac muscle, visceral organs, and blood of dogs (Canis familiaris) in the Southern United States. The organism was previously identified as Hepatozoon canis (James, 1905) Wenyon, 1926; however, differences in clinical signs, histopathological and serological findings, gamont size, and ultrastructure define the new species of Hepatozoon. Attempts to transmit the protozoan from infected dogs to nymphal Rhipicephalus sanguineus ticks, the definitive host of H. canis, were not successful.

A Hepatozoon Species Genetically Distinct From H. Canis Infecting Spotted Hyenas in the Serengeti Ecosystem, Tanzania

“…Our results and those from other studies (Vincent-Johnson et al, 1997;Perkins and Keller, 2001;Simpson et al, 2006b;Criado-Fornelio et al, 2006) demonstrate the value of molecular techniques to reveal the evolutionary relationship between morphologically similar Hepatozoon species.…”

“…Clinical signs consistent with those reported for Hepatozoon infections in domestic dogs (Hervas et al, 1995;Baneth et al, 1997;Vincent-Johnson et al, 1997) and experimentally infected coyote (Canis latrans) pups (Kocan et al, 2000) were observed in two young spotted hyena cubs. The death of both these young hyena cubs may indicate that Hepatozoon infection is mostly associated with mortality in young spotted hyenas, and if so, the effect of Hepatozoon infection on wild carnivore populations may be underestimated.…”

“…As Hepatozoon infections may compromise immune status, spotted hyenas infected with Hepatozoon sp. may be more susceptible to other pathogens (Simpson et al, 2006b) and individuals with compromised immunity may be prone to higher levels of Hepatozoon parasitemia (Hervas et al, 1995;Baneth et al, 1997Baneth et al, , 2001. Although Hepatozoon sp.…”

“…Infection of the vertebrate host normally occurs by ingestion of an infected invertebrate host such as a tick (Smith, 1996). Hepatozoon species are classified on the basis of morphologic characteristics, life history and host taxon, and molecular phylogenetic techniques are used to establish the evolutionary relationships among species (Vincent-Johnson et al, 1997;Perkins and Keller, 2001;Simpson et al, 2006aSimpson et al, , 2006bCriado-Fornelio et al, 2006).…”

“…Globally, Hepatozoon infections in domestic and wild carnivore species have been attributed to Hepatozoon canis or closely related undetermined species (Brocklesby and Vidler, 1965;McCully et al, 1975;Conceiçã o-Silva et al, 1988;Averbeck et al, 1990;Van Heerden et al, 1995), with the exception of the USA, where Hepatozoon americanum infects both domestic dogs (Vincent-Johnson et al, 1997) and wild carnivores (Kocan et al, 2000). Recent phylogenetic studies of unnamed Hepatozoon species in carnivores, including pine martens (Martes martes) in Scotland (Simpson et al, 2006a) and domestic cats in Spain (Criado-Fornelio et al, 2006), suggested that these Hepatozoon species were sufficiently genetically distinct from H. canis (96% sequence homology over a 656 bp sequence and a 908 bp sequence, respectively) to be considered distinct species.…”