Elsevier

Veterinary Parasitology

Volume 122, Issue 2, 21 June 2004, Pages 119-125
Veterinary Parasitology

Confirmation of occurrence of Babesia canis vogeli in domestic dogs in South Africa

https://doi.org/10.1016/j.vetpar.2004.03.019Get rights and content

Abstract

The prevalence of Babesia infections in domestic dogs in South Africa was studied using reverse line blot hybridization and 18S sequence analysis. Babesia canis vogeli was confirmed for the first time in domestic dogs in South Africa. Out of a total of 297 blood samples collected from domestic dogs in Bloemfontein, East London, Johannesburg, Durban and from the Onderstepoort Veterinary Academic Hospital, 31 were positive for Babesia canis rossi, whereas B. c. vogeli was detected in 13 dogs. None of the dogs carried both parasites. The detection of B. c. vogeli has implications with regard to prevalence and varied clinical manifestation of canine babesiosis in South Africa.

Introduction

Babesia species are intraerythrocytic protozoan parasites affecting a wide range of vertebrate hosts and are among the most common tick-borne pathogens of dogs in South Africa. Babesia canis, a large piroplasm, and B. gibsoni, a small piroplasm, are causing canine babesiosis characterized by significant hemolytic anemia (Yamane et al., 1993, Lobetti, 1998).

The trophozoites of B. canis are piriform and 4–5 μm in length or amoeboid and 2–4 μm in diameter (Levine, 1985). There are currently three recognized subspecies of B. canis, which differ on the basis of geographical distribution, vector specificity and antigenic properties (Uilenberg et al., 1989, Hauschild et al., 1995). Babesia canis canis is transmitted by Dermacentor reticulatus, Babesia canis vogeli is transmitted by Rhipicephalus sanguineus, and Babesia canis rossi is transmitted by Haemaphysalis leachi ticks.

Lounsbury (1901) identified H. leachi as a vector of B. canis in South Africa. In subsequent investigations Lewis et al. (1996) found that the South African B. canis isolate could not be transmitted by R. sanguineus. The statement by Howell et al. (1983) that the latter tick species was an important vector of B. canis in South Africa could therefore not be substantiated.

The subspecies also differ in pathogenicity. B. c. rossi causes a frequently fatal infection in domestic dogs, even after treatment; B. c. vogeli causes a moderate often clinically inapparent infection, and B. c. canis infections result in a more variable pathogenicity intermediate between B. c. rossi and B. c. vogeli (Uilenberg et al., 1989). Further evidence provided by several authors supports the recognition of B. c. rossi, B. c. vogeli and B. c. canis as separate taxa (Schetters et al., 1997, Zahler et al., 1998).

The other species that infects dogs is B. gibsoni, which occurs in Asia, North America, North and Eastern Africa and has also been reported in Europe (Casapulla et al., 1998). This parasite measures 1–2.5 μm in length and is either piriform or ring form (Conrad et al., 1991). Babesia gibsoni can be differentiated from B. canis based on morphology, but not from other small piroplasms of dogs. In fact, recent research has revealed that there are at least three genetically distinct small piroplasms occurring in dogs in the USA, Spain and Japan (Kjemtrup et al., 2000).

Molecular diagnosis has previously been used as a tool for the detection and characterization of B. canis infections in dogs (Caccio et al., 2002, Birkenheuer et al., 2003) and in tick vectors (Inokuma et al., 2003).

In this study, we report on a survey of Babesia parasites in dogs using molecular methods, wherein the occurrence of B. c. vogeli in naturally infected dogs was confirmed in South Africa.

Section snippets

Collection of samples

A total of 226 blood samples were collected from dogs in shelters of the Society for the Prevention of Cruelty to Animals (SPCA) (Table 1). The dogs had been abandoned by their owners or were found straying. An additional 55 samples were obtained from dogs at the Onderstepoort Veterinary Academic Hospital (OVAH) and 15 samples were from Keringa Kennels in Johannesburg. None of the dogs sampled displayed clinical signs of babesiosis, except for those sampled at OVAH. Approximately 2–4 ml of blood

Results

Three new probes to differentiate between B. c. rossi, B. c. canis and B. c. vogeli were tested on known positive reference samples (Table 2). There were no cross-reactions between the three species-specific oligonucleotides (results not shown). Screening of PCR products with the RLB showed that 18 samples from OVAH were positive for B. c. rossi and one was positive for B. c. vogeli. The latter dog was from the vicinity of Onderstepoort and had been admitted to OVAH suspected of ehrlichiosis.

Discussion

B. c. rossi was assumed to be the cause of canine babesiosis in South Africa based on its vector specificity (Uilenberg et al., 1989, Taboada and Merchant, 1991, Lewis et al., 1996). This is the first report of B. c. vogeli in South Africa and a confirmation that the most prevalent canine piroplasm is in fact B. c. rossi. Uilenberg et al. (1989) had suggested that B. c. vogeli parasites may occur in large parts of tropical and subtropical regions on all continents, coinciding with the global

Acknowledgements

The research reported here was conducted within the framework of the Memorandum of Understanding between the Faculty of Veterinary Science of the University of Pretoria and the Faculty of Veterinary Medicine of Utrecht University in The Netherlands. Financial support was provided by the National Research Foundation of South Africa, the Delta and Utrecht Scholarship Programme.

We also thank staff members of OVAH and SPCA who helped with the collection of blood samples.

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