Hepatozoon canis infection of wild carnivores in Brazil

Nayro X. Alencar¹, Aguemi Kohayagawa¹, Vamilton A. Santarém².

¹Department of Clinical Veterinary, Faculdade de Medicina Veterinária e Zootecnia, UNESP, Botucatu, São Paulo, Brasil.

²Veterinary Hospital, Universidade do Oeste Paulista, UNOESTE, Presidente Prudente, São Paulo, Brasil.

Abstract

Hepatozoon canis was diagnosed in a crab-eating fox (Cerdocyon thous) found on a highway in the region of Botucatu, São Paulo, Brazil, after being hit by a car. The fox had bilateral fractures of the olecranon, which was corrected by ostheosynthesis. Hematologic findings included a neutrophilia, eosinophilia, monocytosis and mild anemia. In the Leishman-stained blood film, gametocytes of Hepatozoon canis in neutrophils were identified measuring 9.1 ± 0.54 x 5.3 ± 0.46 µm.

Hepatozoon canis (James, 1905), a protozoan parasite that currently is classified in the family Haemogregarinidae in the order Eucoccidia (Levine, 1982), is transmitted by the brown dog tick Rhipicephalus sanguineus (Latreille, 1806). This parasite has been described in rodents and some carnivores, such as the dog, cat, jackal, and hyaena (Soulsby, 1982). The host becomes infected by the ingestion of the infected tick which contains sporozoites (Georgi and Georgi, 1992). The sporozoites are released in the gut of the host, where they penetrate the intestinal wall and are carried by blood to the spleen, bone marrow, liver, lungs, lymph nodes and myocardium (Craig et al., 1978). Signs of hepatozoonosis include fever, anemia, lethargy (Gossett et al., 1985), muscular hyperesthesia, oculonasal discharges, diarrhea (which may be bloody), anorexia (Hoskins, 1991), hind limb paresis and ataxia (Baker et al., 1988), emaciation, nervous abnormalities (Prathaban et al., 1992), and death. The presence of Hepatozoon spp. gametocytes inside leukocytes has been described in several countries in wildlife, including hyaena, lion, leopard, cheetah, jackal (McCully et al., 1975) and fox (Maede et al., 1982).

This article describes a case of Hepatozoon canis in a Brazilian crab-eating fox (Cerdocyon thous) admitted to the Veterinary Hospital of the Faculdade de Medicina Veterinária e Zootecnia, UNESP, Botucatu, São Paulo, Brazil.

In february 1995, a 5-month-old male crab-eating fox, after being hit by a car on a highway near Botucatu, was admitted to the Small Animal Surgery Department. The clinical signs included forelimb paresis, apathy and hyporexia. Radiography demonstrated a bilateral fracture of the olecranon, which was lated corrected by ostheosynthesis.
The results of the hemogram are shown in Table 1. The main findings were: regenerative anemia, mild anisocytosis and polychromasia. The leukocyte increase was due to neutrophilia, monocytosis and eosinophilia; hyperfibrinogenemia (800 mg dl-¹) was also observed.

Table 1. Hemogram of the crab-eating fox (Cerdocyon thous) with Hepatozoon canis infection, and normal values for dog.

On Leishman-stained blood smears cytopasmic inclusion bodies were observed inside the neutrophils. The inclusions had a pale blue capsule (fig. 1), with an elliptical shape, and measured 9.1 ± 0.54 x 5.3 ± 0.46 µm. Infected neutrophils had nuclear degeneration and were larger than non-infected neutrophils.

After surgery, the animal was put on antibiotic theraopy (ampicillin 20 mg kg-¹, IV; benzylpenicillin 600.000 UI, SC). Five days later the fox developed diarrhea, complete anorexia, and rapid deterioration. The fox was euthanized on the seventh day after admission.

Macroscopic findings were: liver degeneration, petechial patches in the lungs, hemorrhagic cystitis and hyperplasia of white spleen pulp.

The pathogenicity of Hepatozoon canis varies from a mild or a non-apparent infection to a serious disease which may lead to death (Craig, 1984). Many authors consider that hepatozoonosis might be associated with diseases, such as canine distemper, erlichiosis and babesiosis, and immunosuppressed animals. Animals with neutrophilic dysfunction and animals under 4 months old are also susceptible (Hoskins, 1991).

McCully et al. (1975) studied hepatozoonosis in wildlife carnivores, observing schizonts of the parasite in lung, liver, spleen, lymph nodes, skeletal muscle, and myocardium, and gametocytes in neutrophils.

The anemia observed in this case is also described by Barton et al. (1985), Gossett et al. (1985) and Elias and Homans (1988), and the neutrophilic leukocytosis and monocytosis has been described in the reports of Craig et al. (1978), Barton et al. (1985) and Ibrahim et al. (1989). The elevated fibrinogen appeared to be related to the surgery and trauma suffered by the fox. Leukocyte dysfunction leads animals to become more susceptible to systemic infections. The morphological and degenerative changes of the leukocytes have been demonstrated by Ibrahim et al. (1989), murata et al. (1991), Murata et al. (1993).

The size of the parasites was smaller than described by Mundim et al. (1992) in dogs and Maede et al. (1982) in foxes, although dimensional variation of the protozoan was described in blood of dogs by Murata et al. (1991). The size, shape, and staining characteristics of the inclusion bodies found inside the neutrophils of this brazilian crab-eating fox is in agreement with the size range given by Soulsby (1982).

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