ACUTE HEAPTOZOONOSIS CAUSED BY HEPATOZOON CANIS IN DOGS IN SRI LANKA

Canine Hepatozoonosis is a tickborne disease caused by Five dogs aged between five months to seven years apicomplexan haemoprotozoan parasites of the Genus recently diagnosed with different disease conditions Hepatozoon. Two species of hepatozoons, namely presented to Veterinary Teaching Hospital, Peradeniya Hepatozoon canis (H. canis) and Hepatozoon with paresis, chronic emaciation, muscular pain, had americanum (H. amaricanum) are known to infect dogs Hepatozoon like gamonts (4-12%) in the peripheral (Baneth et al., 2003). Of these two species, H.canis circulation. Though H.canis is commonly known to cause transmitted by the brown dog tick Rhipicephalus clinical ly inapparent infect ion, the cl inical sanguineus is reported in Asian countries whereas H. manifestations, haematological parameters, serum amaricanum transmitted by Amblyomma maculatum is alkaline phosphate (ALP) levels and response to treatment limited to Southern United States. Comparatively, latter is of those five patients were evaluated to identify the factors known to cause severe infection characterized by which complicated the clinical presentation. exostosis and myositis (Vincent-Johnson et al. 1997). Signalements, clinical manifestations and the medical history of the five patients are given in Table 1. When first recognized in India in 1905, it was believed that H. canis only cause a milder disease resulting in Two of the five patients (patient 1 and 2) had been anaemia and lethargy (Vincent-Johnson et al. 1997). recently treated with immunosuppressive doses of However, it was later found out that certain factors corticosteroids. Third patient was on long-term including immunosuppression and co-infections can lead antimicrobial therapy (over five months) and the fourth to severe clinical manifestations due to Hepatozoonosis. A patient was on long term pancreatin. More than 4% (4number of nonspecif ic haematological and 12%) of the neutrophils in peripheral blood contained haemochemical changes including non-regenerative capsule like gamonts (Figure 1). Multiplex polymerase a n a e m i a , t h r o m b o c y t o p e n i a , n e u t r o p h i l i a , chain reaction (PCR) was performed as described in hyperproteinaemia, hypoalbuminaemia, polyclonal Kledmanee et al. (2009) in order to determine whether the gammopathy, and elevated serum creatine kinase (CK) clinical complications were due to concurrent infection and alkaline phosphatase (ALP) have been seen in dogs with Ehrlichia canis or Babesia species. Electrophoresis infected with H. canis (O'Dwye et al., 2006). The of PCR amplicons confirmed Hepatozoon canis as the detection of capsule-like gammonts in the cytoplasm of Hepatozoon species observed in peripheral blood and the the neutrophils in blood smears is routinely used to dogs were not concurrently infected with E. canis or diagnose hepatozoonosis. Molecular diagnostic Babesia (Figure 2). techniques, such as polymerase chain reaction (PCR) and sequencing are important for species identification. Peripheral vestibular syndrome (due to Malassezia pachydermatis, Otodectes cynotis), myasthenia gravis In recent times, we have observed that the Hepatozoon and intervertebral disk disease were included as causes emaciation, ataxia, paraplegia, circling differential diagnoses. Peripheral vestibular syndrome movements, difficulty in prehension and severe muscle was ruled out by the negative finding of parasites or fungi pain particularly among immunocompromised dogs. This in cytological examination of the external ear canals. The communication discusses the clinical manifestations and possibility of myasthenia gravis was also ruled out by the prognosis of five dogs affected with hepatozoonosis. negative response to oral neostigmine bromide test. SUMMARY: Canine hepatozoonosis caused by H. canis is usually recognized as a mild clinical disease characterized by mild anaemia and lethargy. Complicated clinical manifestations of H. Canis infection have been occasionally observed in dogs. This clinical communication describes acute hepatozoonosis in five dogs characterized by neurological symptoms, ataxia or paresis, emaciation and anaemia. http://doi.org/10.4038/slvj.v64i1A.19

The total white blood cell counts were within normal and age (control group) ( Figure 3). Serum Alkaline range and no significant variations of differential WBC Phosphatase (ALP) levels were moderately elevated in all counts were detected. All five patients were moderately to five and ranged between 233-750 U/L (normal 20-157 severely anaemic with a mean PCV of 19.4 + 2.5 (normal U/L). range 25-27) and mean haemoglobin of 6.98 + 1.5 (normal range: 9-19). The decreased platelet counts were the most All patients were given two I/M doses of Imidocarb significant finding in all five patients. We compared the dipropionate (6.6mg/Kg) at two weeks intervals as the platelet counts of the hepatozoon affected patients with specific treatment for H. canis. All five patients showed the breed and age matched healthy dogs (control). The significant improvement within first week of the platelet counts of the patients were significantly lower (p< treatment and recovered fully on completion of the 0.05) than that of the healthy dogs matched for the breed treatment schedule.

DISCUSSION
Acute hepatozoonosis caused by H. canis has been reported in several Asian countries often characterized by anaemia, lethargy and chronic emaciation (Murata et al., 1991;Sakuma et al., 2009;O'Dwyer et al., 2006). Clinical signs observed in the patients of the present study are different to those due to presence of various neurological manifestations which were more commonly reported in infections caused H. amaricanum. However Marchetti et al., (2009) has reported neurological s i g n s a n d s e v e r e p e r i o s t e a l inflammation in a dog in Italy due to H. canis. A high level of parasitaemia was consistent in a majority of reported cases of H. canis. In contrary, the level of parasitaemia observed in our patients were low, probably because they were either immunosuppressed or chronically ill. It has been known that the pathogenesis and the severity of H.canis infection are usually influenced by immunosuppression or concurrent infections 1997).
Radiographic examination of the appendicular bones of three patients did not reveal signs of periosteal inflammation which is a characteristic feature of H. amaricanum but observed occasionally in dogs with H. canis (Marchetti et al., 2009;Priya et al., 2004;Murata et al., 1991). Usually the , (Baneth and Weigler, increased ALP levels observed in the cases of H. canis are considered to be associated with the periosteal lesions. We also noted a moderate increment in serum ALP levels in these patients but it is important to determine the isoform of the ALP to identify the origin of the enzyme. Elevated serum ALP levels may originate from the liver (L-ALP) or bones (B-ALP). In addition, exogenous corticosteroids will increase the production of a unique form of ALP (C-ALP) in the liver The elevated ALP in two of the five dogs studied here may have an association with high doses of corticosteroids therapy in the past.
The neurological signs including circling movements, ataxia, paraplageia, tetraplegia and difficulty in prehension observed in these patients were difficult to explain. Difficulties in walking have been observed only in a few dogs infected with H. canis (Voyvoda et al., 2004) without confirmatory evidence for an association with the parasite. The limbs of the two patients who showed paraplegia and tetraplegia were stiff and extended and were painful on palpation. Therefore, it is most likely that the dysbasia and paresis were due to myalgia caused by parasitic cysts in muscle tissues, which would have been confirmed if serum creatinine kinase (CK) levels and aspartate aminotransferase (AST) levels were evaluated.
In consistent with the previous reports (Murata et al., 1991;Sakuma et al., 2009), we also noted some haematological changes such as low red blood cell counts, low PCV and low haemoglobin levels in the patients affected with H. canis. These changes could be mainly due to anaemia of chronic disease (ACD). It was not clear whether the cause of thrombocytopenia seen in all five patients was solely due to H. canis or another infection. Other haemoparasites including Anaplasmaplatys and Mycoplasma haemocanis as well as other infectious agents can cause thrombocytopenia in dogs, but we only tested the study patients for Babesia species and Ehrlichia canis.
Canine hepatozoonosis is usually treated with imidocarb dipropionate (5-6mg/kg) and the treatment needs to be repeated in 14 days until complete elimination of gamonts in peripheral blood smears ( ). Treatment with Doxycycline is stated as an alternative to imidocarb ( . In addition to the specific treatment, management of the clinical case should be done accordingly to achieve a good prognosis.
In contrary to the popular belief that the H.canis only causes mild clinically inapparent infection, the organism may cause clinically significant conditions particularly in immunocompromised cases. Most often these conditions may go undiagnosed and hence untreated due to non-specific clinical signs, lack of diagnostic facilities and lack of knowledge. Inclusion of Hepatozoonosis in the differential diagnoses in clinical cases with aforementioned manifestations will aid in diagnosis of the condition.