title: Observations on tissue stages of Hepatozoon americanum in 19 naturally infected dogs.
abstract: Lesions and associated tissue stages of Hepatozoon americanum in 19 naturally infected dogs are described. Schizogony takes place in an unidentified host cell which, during the early stages of the asexual cycle, is contained within a broad, multilamellar mucopolysaccharide 'cyst.' Material forming the cyst appears to be host-derived. An intense inflammatory response follows rupture of the schizont and disintegration of the cyst wall. There is unusually intense angiogenesis associated with the resulting granulomatous inflammation initiated by the freed merozoites. Phagocytized zoites enter the canine circulatory system through the walls of these vessels. Evidence is presented that suggests a single infecting episode can cause prolonged (> or = 9 months) infection, and further, that infection is perpetuated by repeated asexual cycles. Parasites in peripheral blood leukocytes include both those with and without a visible nucleus.
authors.affiliation: Department of Anatomy, Pathology and Pharmacology, College of Veterinary Medicine, Oklahoma State University, Stillwater 74078-2006, USA.
authors.forename: R J
authors.initials: RJ
authors.lastname: Panciera
authors.forename: S A
authors.initials: SA
authors.lastname: Ewing
authors.forename: J S
authors.initials: JS
authors.lastname: Mathew
authors.forename: C A
authors.initials: CA
authors.lastname: Cummings
authors.forename: A A
authors.initials: AA
authors.lastname: Kocan
authors.forename: M A
authors.initials: MA
authors.lastname: Breshears
authors.forename: J C
authors.initials: JC
authors.lastname: Fox
mesh_terms: D000818:Animals; D003048:Coccidiosis / Q000469:parasitology / Q000473:pathology / Q000662:veterinary*; D004283:Dog Diseases / Q000469:parasitology*; D004285:Dogs; D016783:Eucoccidiida / Q000502:physiology / Q000648:ultrastructure*; D006099:Granuloma / Q000469:parasitology / Q000473:pathology / Q000662:veterinary; D006790:Host-Parasite Interactions; D018482:Muscle, Skeletal / Q000469:parasitology / Q000473:pathology