Molecular detection and characterization of tick-borne pathogens of dogs

This thesis focuses on the molecular characterization of tick-borne parasites of dogs in South Africa. Emphasis is placed on Babesia, Erhlichia, incidental and novel parasite infections that may cause morbidity or mortality in infected dogs. An outbreak of canine babesiosis in the Netherlands is also reported in this thesis. Molecular techniques were employed to isolate, amplify and characterize genomic DNA of these parasites to species level. During preliminary screening of blood samples collected from various sites in the country, that included the Onderstepoort Veterinary Academic Hospital, SPCAs and private clinics throughout seven provinces in South Africa, it was discovered that domestic dogs harboured a wide variety of tick-borne pathogens. The most frequently encountered parasites in South Africa were Babesia rossi, a novel Theileria species of dogs, B. vogeli and Ehrlichia canis respectively. The parasites occurred as single or mixed infections. Incidental infections that included B. gibsoni and Trypanosoma congolense were also detected using PCR. Although it was anticipated that zoonotic Ehrlichial infections of dogs would be detected, none were found. Babesia vogeli was reported for the first time in South Africa although, without any clinical significance. An outbreak of autochthonous canine babesiosis in the Netherlands was confirmed to have been caused by Babesia canis. Dermacentor reticulates was implicated in the transmission of the parasite to naïve dogs. Clinical significance of B. rossi and the novel Theileria sp. of dogs was evaluated. Babesia rossi was found to be of significant clinical importance. Genotyping of B. rossi isolates revealed that parasite genotypes could be correlated to disease phenotype. Additionally, specific genotypes could also be associated with fatalities. Although the characterization of the Theileria sp. in dogs was a first report in South Africa, the clinical significance of this infection in dogs appeared to be poorly resolved. The dangers of having non-endemic species becoming established in South Africa was highlighted with the incidental finding of a B. gibsoni infection in an imported dog. The results of this thesis have shown therefore that populations of dogs that live in tickendemic areas are exposed to single or multiple tick-borne pathogens. These pathogens continue to cause morbidity and mortality in susceptible dogs. Correct diagnosis (supported by molecular diagnostic tools) followed by appropriate treatment offers a better understanding and management of these tick-borne pathogens. Preventative measures should be fully evaluated and applied to prevent these tick-borne pathogens from adversely affecting the canine population in South Africa and elsewhere.Thesis (PhD)--University of Pretoria, 2008.Veterinary Tropical Diseasesunrestricte

Occurrence and diversity of bovine coccidia at three localities in South Africa

Please read the abstract in the section 00front of this documentDissertation (MSc (Veterinary Science))--University of Pretoria, 2000.Veterinary Tropical Diseasesunrestricte

Assessment of sequence descriptions of selected Theileria parva hypothetical proteins retrieved from sequence similarity search databases

The protozoan parasite Theileria parva is the causative agent of cattle theileriosis, a disease with a destructive impact on the agricultural economy through mortality and morbidity of affected cattle. In cattle, T. parva infection results in varied disease syndromes depending on the parasite host of origin; cattle-derived T. parva causes East Coast fever while buffaloderived parasites cause Corridor disease. The differences in the resulting disease caused by T. parva infection have raised an interest to understand the proteins involved in the disease manifestations. Consequently, a transcriptome study comparing the cattle and buffalo-derived T. parva isolates was undertaken; differentially expressed genes were detected of which 74% (867) were hypothetical proteins (HPs). Since HPs could play a vital role in the pathogenicity and host-parasite interaction, the primary aim of the study was to identify biological roles of these proteins. A combination of in silico analysis tools was employed to annotate HPs according to sequence descriptions, confirmed by sequence homology in comparison with closely related species and conserved domains. Initial screening for sequence descriptions (SDs) based on sequence similarity search using Blast2GO retrieved results for 392 HPs. Comparison of this output to other databases (KEGG and KOBAS) detected consensus SDs for 229 HPs, of which 109 were further confirmed by inferring homology to related species. Sequence homology analysis also resulted in designation of SDs to 74 HPs from the remaining 163 without consensus SDs from database analyses. For HPs which did not meet the criteria employed in sequence homology analysis (209), conserved domain analysis facilitated assigning of SDs for 114 HPs. Overall, 297 (76%) HPs were successfully allocated SDs. Finally, the results from this study have showed that output from automated sequence similarity databases is not always reliable in assigning SDs for specific species, making confirmation using other approaches necessary.Poster presented at the University of Pretoria, Faculty of Veterinary Science Faculty Day, August 25, 2016, Pretoria, South Africa.ab201

A field trial evaluation of the prophylactic efficacy of amitraz-impregnated collars against canine babesiosis (Babesia canis rossi) in South Africa

South African canine babesiosis caused by Babesia canis rossi is a common clinical disease in dogs in South Africa and remains a significant cause of domestic dog mortality. To determine whether tick-repellent, 9% amitraz-impregnated tick collars (Preventic-Virbac) could prevent tick-borne exposure to B. canis rossi, 50 dogs were assigned to two groups. Group 1 (20 dogs), polymerase chain reaction (PCR)- and reverse line blot (RLB)-negative for B. canis rossi, were fitted with amitraz collars and blood samples collected monthly , over a 6-month period, and analysed for B. canis rossi. Group 2 (30 dogs) included 5 dogs selected on a month-by-month basis from a population of dogs from the same geographical area as the group 1 dogs, but with no history of previous tick control, which were blood-sampled together with the treatment group and analysed for B. canis rossi by PCR and RLB, to serve as the control group. Eight of the 30 control dogs (26.6 %) were PCR / RLB positive for B. canis rossi, indicating high pathogen exposure during the trial period. All twenty of the treatment group dogs remained negative for B. canis rossi throughout the 6 months of the trial. These results suggest that the use of amitraz-impregnated collars had a significant effect on reducing infection with B. canis rossi