Original Research

Characterisation of South African field Ehrlichia ruminantium using multilocus sequence typing

Zinathi Dlamkile, Luis Neves, Darshana Morar-Leather, Christopher Brandt, Alri Pretorius, Helena Steyn, Junita Liebenberg
Onderstepoort Journal of Veterinary Research | Vol 90, No 1 | a2119 | DOI: https://doi.org/10.4102/ojvr.v90i1.2119 | © 2023 Zinathi Dlamkile, Luis Neves, Darshana Morar-Leather, Christopher Brandt, Alri Pretorius, Helena Steyn, Junita Liebenberg | This work is licensed under CC Attribution 4.0
Submitted: 13 April 2023 | Published: 14 November 2023

About the author(s)

Zinathi Dlamkile, Department of Veterinary Tropical Diseases, Faculty of Veterinary Science, University of Pretoria, Pretoria, South Africa
Luis Neves, Department of Veterinary Tropical Diseases, Faculty of Veterinary Science, University of Pretoria, Pretoria, South Africa; and Centro de Biotecnologia-UEM, Eduardo Mondlane University, Maputo, Mozambique
Darshana Morar-Leather, Department of Veterinary Tropical Diseases, Faculty of Veterinary Science, University of Pretoria, Pretoria, South Africa
Christopher Brandt, Department of Vaccines and Diagnostics Development, Onderstepoort Veterinary Research Institute, Agricultural Research Council, Pretoria, South Africa
Alri Pretorius, Department of Veterinary Tropical Diseases, Faculty of Veterinary Science, University of Pretoria, Pretoria, South Africa; and Department of Vaccines and Diagnostics Development, Onderstepoort Veterinary Research Institute, Agricultural Research Council, Pretoria, South Africa
Helena Steyn, Department of Vaccines and Diagnostics Development, Onderstepoort Veterinary Research Institute, Agricultural Research Council, Pretoria, South Africa
Junita Liebenberg, Department of Vaccines and Diagnostics Development, Onderstepoort Veterinary Research Institute, Agricultural Research Council, Pretoria, South Africa

Abstract

Heartwater, one of the major tick-borne diseases of some domestic and wild ruminants in Africa, is caused by Ehrlichia ruminantium. The genetic diversity of E. ruminantium isolates renders the available vaccine ineffective against certain virulent isolates. To better understand the E. ruminantium genotypes in South Africa, a total of 1004 Amblyomma hebraeum tick deoxyribonucleic acid (DNA) samples from cattle in three South African provinces were tested by pCS20 Sol1 real-time polymerase chain reaction (qPCR) and characterised by multilocus sequence typing (MLST) using five housekeeping genes. Out of 1004 samples tested, 222 (22%) were positive for E. ruminantium. The occurrence of E. ruminantium in Mpumalanga, KwaZulu-Natal and Limpopo provinces was 19%, 22% and 27%, respectively. The E. ruminantium positive samples were screened for housekeeping genes and sequenced. Phylogenetic analysis revealed three main lineages: clade 1 made up of worldwide isolates (eastern, southern Africa, and Caribbean isolates), clade 2 comprised only West African isolates and clade 3 consisted of Omatjenne, Kümm2 and Riverside. Some study sample sequences were not identical to any of the reference isolates. However, they could all be grouped into the worldwide clade. Genetic variation in the sequenced regions was observed in the form of single nucleotide polymorphisms (SNPs). Using MLST to characterise E. ruminantium field isolates allowed the South African genotypes to be clearly distinguished from the distinct West African isolates.

Contribution: Characterisation of E. ruminantium field isolates is important for the control of heartwater and contributes to preliminary knowledge required for the development of a more practical vaccine against heartwater.


Keywords

Ehrlichia ruminantium; heartwater; characterisation; pCS20; multilocus sequence typing; MLST; phylogenetic; PCR

Sustainable Development Goal

Goal 15: Life on land

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