Short communicationFirst molecular characterization of canine hepatozoonosis in Argentina: evaluation of asymptomatic Hepatozoon canis infection in dogs from Buenos Aires
Introduction
Canine hepatozoonosis is a disease transmitted by the ingestion of ticks infected with apicomplexan protozoa of the genus Hepatozoon. Hepatozoon canis (James, 1905), described in Asia, Europe, Africa and Brazil, is transmitted by the tick Rhipicephalus sanguineus (Baneth et al., 2001). A second Hepatozoon species that infects dogs is Hepatozoon americanum (Vincent-Johnson et al., 1997). It is found in the southeastern United States, transmitted by the Gulf coast tick Amblyomma maculatum and causes severe myositis and lameness (Mathew et al., 1998).
H. canis infects leukocytes and hemolymphatic tissues. Infection has been reported to be associated with a variety of clinical signs ranging from sub-clinical infection to a severe life threatening disease with distinct hematological, biochemical and histopathological alterations (Baneth and Weigler, 1997, Gavazza et al., 2003). It has been suggested that the presence of clinical disease might be related to predisposing factors such as immunosuppressive conditions or therapy, genetic defect in neutrophilic function, associated infectious agents such as canine distemper virus (CDV) or immature immune system in animals younger than 4–6 months (Baneth et al., 1997). The most frequent clinical signs observed are fever, anorexia, severe weight loss and lethargy (Baneth and Weigler, 1997). Non-regenerative anemia and neutrophilic leukocytosis were the most frequent hematological alterations found in a preliminary study of canine hepatozoonosis carried out by the authors in Argentina (unpublished data).
Canine hepatozoonosis in Buenos Aires is an expanding infection. It was first described in 1999 (Silva et al., 1999) and subsequently, seven cases were reported in the western region of Greater Buenos Aires (Esarte et al., 1999). However, no species confirmation by molecular methods was carried out in either study.
The aim of the present study was to identify the Hepatozoon species found in dogs in Buenos Aires by molecular testing and to describe naturally occurring infection in six dogs that inhabit the same house in a southern suburb of Buenos Aires. Epidemiological and hematological data on these dogs were collected during nearly a 1-year follow up.
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Materials and methods
Six mixed-breed dogs, 1–12 years old, that live in the same household in Lomas de Zamora in southern Greater Buenos Aires, Argentina, were studied between April 2005 and February 2006. Circulating Hepatozoon gamonts had been detected in two of these dogs before the study began (dogs 1 and 3). Blood samples were obtained during four different dates (April, May and July 2005 and February 2006) and evaluated in the DIAP Laboratory. Clinical evaluation of the dogs including tick investigation was
Results
The dogs included in the study lived in a yard between a leather workshop and the owner's home. The environment included vegetation and was suitable for the development of ticks, however, none were found on the animals. According to the owner they had been parasitized by ticks during the previous year. Dog 1 was the mother of dogs 3 and 6; dogs 2, 4 and 5 were not related to each other.
The dogs showed no evidence of clinical signs of disease during the study period. However, five of the six
Discussion
This study describes apparently asymptomatic infection in six dogs living in the same household in Buenos Aires. A follow up of the dogs during 1 year revealed fluctuations in the level of parasitemia with no extreme hematological or biochemistry alterations. Sequencing of the 18S rRNA gene indicated that infection was caused by H. canis. This is the first genotypic characterization of Hepatozoon from Argentina.
Although most of the reports on H. canis infection are from Europe, Asia or Africa,
Acknowledgement
We would like to thank Mr. Solís, the dogs’ owner, for his collaboration.
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