Hepatozoon fusifex sp. n., a Hemogregarine from Boa constrictor Producing Marked Morphological Changes in Infected Erythrocytes

Abstract

In a large proportion of Boa constrictor taken in the vicinity of Colima, Mexico, hemogregarines were visible in erythrocytes of the peripheral circulation. One characteristic of a majority of these infections was the marked fusiform or spindle shape of many infected red blood cells. Such cells closely resembled certain avian blood cells parasitized by Leucocytozoon. Developmental stages in the blood, and schizogony in the tissues are described. Schizogony occurs primarily in the endothelial cells of lung capillaries but may occur in this type of cell in other organs. The spindle shape of the infected erythrocytes is so distinctive that the organisms are placed in a new species, Hepatozoon fusifex. Culex tarsalis or Aedes togoi, biting B. constrictor with certain types of hemogregarines in their blood developed mature sporozoites in their hemocoels. Similar stages were found in a tick, Amblyomma dissimile, removed from a boa. The hemogregarines were transmitted to clean B. constrictor by feeding them infective C. tarsalis or A. dissimile. It has not been established with certainty whether these sporogonic stages are part of the life history of H. fusifex or belong to a separate hemogregarine species. Hemogregarine parasites frequently produce considerable hypertrophy of the infected blood cells. Marked changes in the morphology of the host cells apart from those associated with hypertrophy are less common. Wenyon (1908) reported that in Haemogregarina gracilis from Mabuya quinquetaeniata, the parasite had the property of pushing out the infected host cell at either end and thus elongating it considerably. In the same paper, Wenyon noted that another sporozoan blood parasite of African snakes, Haemocystidium najae, from Naja haje and from Naja nigricollis, altered the shape of the infected erythrocyte so that the latter came to resemble the fusiform shape of a red cell of the guinea fowl infected by Leucocytozoon. Laveran and Salimbeni (1909) pictured hypertrophied erythrocytes of a Brazilian lizard, Tupinambis teguixin, infected with Haemogregarina tupinambis. Some of these red cells reached a length of 35 yt and became spindleshaped. Other investigators have reported Leucocytozoon-like parasites in the blood of reptiles. However, this designation has been based Received for publication 7 March 1969. * Aided by Grants GB 414 and 7069 from the NSF, Training Grant E-70, U. S. Public Health Service, Grant Zoology 254, University of California, and Sigma Xi-RESA Grant in Aid of Research, 1963. t Present address: Gorgas Memorial Laboratory, P. 0. Box 2016, Balboa Heights, Canal Zone. either on the shape of the parasite or on its presence in leukocytes (Leger and Mouzels, 1917) and in no case did the infected blood cell show a spindle or fusiform shape. Yonge (1966) found round Leucocytozoon-like gametocytes in differentiating blood cells of Natrix sipedon sipedon infected with Cytotoddia. Arcay de Peraza (1968) erected a new genus and species, Paraleucocytozoon lainsoni, for a leukocyte-inhibiting sporozoan of Iguana iguana iguana; and Lainson and Shaw (1969) reported a leucocytozoid with round to oval gametocytes in blood cells of the Brazilian lizard Tupinambis nigropunctatus. The parasite described in the present communication produced much greater elongation of the infected host erythrocyte than was observed by previous investigators, and much more modification in the shape of the parasitized cell than has been noted for other hemogregarine infections. MATERIALS AND METHODS Fifty-five of 57 adult or subadult boas (Boa constrictor)* taken from 1963 through the spring * The host has been placed in either the genus Constrictor or Boa in recent herpetological papers. Our previous report used the designation C. constrictor (Ball, Chao, and Telford, 1967). The use of the generic name Boa instead of Constrictor now seems to be accepted by most herpetologists (Underwood, 1967) and therefore we are using this designation in the present paper.