Hepatozoon-Like Parasite (Schizonts) in the Myocardium of the Domestic Cat

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1 Vet. Path. 10: (1973) Hepatozoon-Like Parasite (Schizonts) in the Myocardium of the Domestic Cat U. KLOPFER, T.A. NOBEL and F. NEUMANN Department of Pathology, Kimron Veterinary Institute, affiliated with the University of Tel-Aviv, Bet-Dagan Abstract. In a survey of 100 necropsies on cats, 36 were found to have Hepatozoon sp. schizonts in the myocardium. The schizonts appeared to be located in the capillary 1Linien. Two forms of schizonts were seen, one containing peripheral rosettes of nierozoitelike formations and the other filled with them, showing a cyst-like structure. No parasites were seen in the peripheral blood, spleen, and lymph nodes. Hepatozoon canis (James, 1905), or other Hepatozoon sp., has been reported in wild animals [2, 3, 5, 7, 9, 11, 12, 14, 161 including wild felidae [2, 5, 7, 91, where it was also found in the myocardium [2, 5, 91. In the domestic cat, however, Hepatozoon sp. was reported only by PATTON in India [15, 161. He described the parasite in the peripheral blood, notably in the polymorphonuclear leucocytes, where, in his opinion, it presented morphological features identical with those of Hepatozoon canis, which was first described by BENTLEY [I] in the dog. PATTON [15, 161 called this parasite Hepatozoon, felis domestici. Schizonts of Hepatozoon sp. have not hitherto been reported in the domestic cat. Occasional findings in our laboratory of this parasite in the myocardium prompted a survey of its prevalence in the domestic cat in Israel. Materials and Methods Two groups of cats were studied. The first group included 50 dead cats submitted to the laboratory for rabies examination. Most of these cats died from panleukopenia,

2 I86 KLOPFER/NOBEL/NEUMANN gangrenous pneumonia, or undiagnosed diseases. The second group comprised 50 apparently healthy stray cats, which were killed after being used in various laboratory denionstrations. Blood smears were prepared from each cat after death and stained with Giemsa. All smears were examined microscopically and reexamined whenever the heart muscle proved to be infested with Heparozoon schizonts. Spleens, niesenteric lymph nodes and myocardia were harvested for histological examination. The heart was sectioned transversely, through both ventricles. The samples were fixed in 10% formalin. From each organ two paraffin blocks were prepared. From each myocardium sample an average of 10 sections, 7 pni thick, were cut by step and stained with hematoxylin and eosin. From the other organs two sections were prepared and stained as above. Periodic acid-schiff (PAS) reaction was studied on some sections containing parasites. The percentage of slides in which parasites were found was calculated from the total sections examined. A scoring system was developed to evaluate the degree of infestation according to the following: 0-10% sections found infestated = % sections found infestated = i--i % sections found infestated = % sections found infestated = ++-I- The diameter of 100 schizonts was measured with the aid of the projection attachment of the Zeiss photomicroscope. Results The histological examination of the heart muscle showed spherical bodies resembling schizonts of Hepatozoon sp. This parasite was constantly found in the lumen of capillaries, showing a partial patent lumen with erythrocytes (fig. l), often giving the impression of obstructing the capillaries. The capillaries in which the schizonts were seen were markedly dilated. Two forms of schizonts were seen: (1) schizonts with nucleated formations, resembling immature merozoites arranged as palisades inside a membrane, the center filled with a foamy material (fig. 1); and (2) schizonts whose lumen was either densely or loosely filled with merozoites (fig. 2). In the densely filled schizonts, all the merozoites except the nucleus were PAS-positive, whereas in the loose one, PAS-positive granules were constantly seen in one pole of the merozoites, which was opposed to that of the nucleus. The diameter of the schizonts was 22j4.8 pm, with a range of pm. More parasites were localized in the wall of the left ventricle than in the right or in the interventricular septum. In some sections schizonts were

3 Hepatozoon-Like Parasite 187 Fig. 1. Cat myocardium. Intravascular schizonts with merozoites at periphery; the center consists of foamy residual material. HE. Fig. 2. Cat myocardium. Hepatozoon schizonts, spherical body filled with merozoites within a capillary. HE. present in three to four adjacent capillaries. A mild perivascular infiltration of inflammatory cells surrounded some of the affected vessels. The prevalence of schizonts in the myocardium is summarised in table I. 30% of the cats submitted for necropsy and 42y0 of the apparently healthy cats were infested.

4 188 KLOPFER/NOBEL/NEUMANN Table I. Prevalence of Hepatozoon sp. in the myocardium of cats Scoring of results Group 1, dead cats Group 2, killed cats Total Total cats examined 50 Positive cats + 9 (ISYO,) +t 3 (6%) +-I-+ 2 (4%) +t++ I (2%) Total positives 15 (30%) 50 9 (ISYO) 10 (20%) 1 (2%) 1 (2%) 21 (42%) No parasites or lesions possibly related to this parasite were found in the blood smears, spleens and lymph nodes. Discussion LAIRD [13] in 1959 observed that no further infestations with Hepatozoon were reported in cats in half a century, after PATTON S report, and none came to light in LAIRD S examinations of blood films of 39 examples from Singapore and of 14 from Malaya. PATTON [15] examined 347 cats and found gametocytes in the polymorphonuclear leucocytes of nine. He called them Hepatozoon felis domestici because of the alleged absence of a capsule found in Hepatozoon canis. WENYON [18] and later BATHIA [4] considered this criterion inadequate, because they distinguished a capsule that PATTON failed to notice. Therefore, WENYON considered it impossible to differentiate between Hepatozoon felis domestici and Hepatozoon canis and suggested that both parasites were identical. Hitherto the Hepatozoon sp. was described only in the neutrophil granulocytes of the cat [15]. Our finding is the first report of Hepatozoon schizonts in the cat. This schizont was found to be localized in the capillaries of the myocardium and was morphologically identical to schizonts of Hepatozoon canis found in lymph nodes, spleen and liver of the domestic dog [6, 10, 17, 181 and in the myocardium of wild mammals [2,5,9]. Positive PAS reaction of the schizonts and merozoites seems also to support the hypothesis that we are dealing with a Hepatozoon sp. parasite [3]. Inflammatory reactions to the schizonts were scarce. If several schizonts were grouped together and partially obstructed capillaries, however, clinical symptoms could hypothetically occur.

5 Hepatozoon-Like Parasite 189 In our findings, which included reexamination of blood smears, no gametocytes were seen, either in the neutrophil granulocytes as was found by PATTON [I51 or schizonts in the lymph nodes, as in Hepatozoon canis. The favored sites of Hepatozoon sp. schizonts, according to the literature, are liver, bone marrow and lung [2, 31 but since these organs were not surveyed in this study, our findings may not reflect the true prevalence of the parasites in the domestic cat in Israel. Thus, pathological investigations as well as experimental work are necessary for further clarification of this problem. References I BENTLEY, C.A.: A new leucocytozoon of the dog. Brit. nied. J. i: 1018 (1905); cited by KRAMPITZ [I I]. 2 BASSON, P.A.; MCCULLY, R. M.; KRUGER, s. P.; VAN NIEKERK, J.W.; YOUNG, E.; DE Bos, V.; KEEP, M. E. und EBEDES, H.: Krankheiten beim sgdafrikanischen Wild. Neuere Untersuchungen. Vet.-med. Nachr. 43: (1971). 3 BASSON, P.A.; MCCULLY, R.M.; BIGALKE, R.D., and VAN NIEKERK, J.W.: Observation on a Hepatozoon-like parasite in the impala. J. sth. afr. vet. nied. Ass. 38: (1967). 4 BATHIA, B. L.: Protozoa: Sporozoa in the fauna of British India (Taylor & Francis, London 1938); cited by LAIRD [13]. 5 BROCKLESBY, D. W. and VIDLER, B. 0. : Some new host records for Hepatozoon species in Kenya. Vet. Rec. 75; 1265 (1963). 6 DISSANAIKA, A. S.: Hepafozoon ranis infection in dog in Ceylon. Ceylon vet. J. 9: (1961). 7 KEYMER, L. F.: Hepatozoon species in wild African mammals. Vet. Rec. 76: 641 (1964). 8 KEYMER, L.F. : Blood protozoa of insectivores, bats and primates in Central Africa. J. Zool., Lond. 163: (1971). 9 KEYMER, L.F.: Blood protozoa of wild carnivora in Central Africa. J. Zool., Lond. 164: (1971). 10 KLOPFER, U.: Unpublished data. I 1 KRAMPITZ, H. E.: Uber das Vorkoninien und Verhalten von Haemococcidica der Gattung Hepafozoon Miller, I908 (Protozoa adeleidea) in niittel- und sudeuropaischen Siiugern. Acta trop. 2/: (1964). 12 KRAMPITZ, H.E.; SACHS, R.; SCHALLER, S.B. Lind SCHINDLER, R.: Ziir Verbreitung von Parasiten der Gattung Hepatozoon Miller 1908 (Protozoa adeleidea) in ostafrikanischen Wild- und Saugetieren. 2. Parasitenk. 3/: (1969). 13 LAIRD, M.: Malayan protozoa and Hepatozoon Miller (Sporozoa: Coccidia) with an unusual host record for H. ranis (James). J. Protozool. 6: (1959). 14 PATTON, W. S.: On a parasite found in the white corpiiscules of blood in palm squirrels. Sci. Mem. Off. Med. Sant. Dept. Gov. India N.S., No 24, pp (1906); cited by LAIRD [13].

6 190 KLOPFER/NOBEL/NEUMANN 15 PATTON, W. S.: Mammalian leucocytozoon. Ann. Rep. Bact. Sect. King Inst. Protect. Med., Guindy 1907, Madras (1908); cited by LAIRD [13]. 16 PATTON, W. S.: The haemogregarinaes of mammals and reptiles. Parasitology I: (1908). 17 Rroux, J. A,, GOLVAN, Y. J., and HONIN, R.: Mixed Hepatozoon canis and Leishmania canis infection in a dog in the Sete area, France. Ann. Parasit. hum. comp. 39: (1964). 18 WENYON, C. M.: Protozoology, vol. 11 (Baillere, Tindall & Cox, London 1926). Request reprints from: Dr. U. KLOPFER, Kimron Veterinary Institute, P.O. Box 12, Bet-Dugan (Israel)