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More Sensitive PCR Revealed Rickettsia DNA in Six New South African Wildlife Hosts

White rhinoceros in Lalibela Game Reserve, South Africa
Research · Disease, parasites & microbiology

A more sensitive molecular test revealed Rickettsia DNA in six South African wildlife hosts in which these bacteria had not previously been recorded. Rickettsia are obligately intracellular bacteria, and several groups include tick- or other vector-borne pathogens that can infect animals and people.

A more sensitive test uncovered DNA missed by the earlier assay

The researchers re-examined spleen samples from 73 wild mammals representing 11 species in Kruger National Park, Timbavati Private Nature Reserve, Mountain Zebra National Park and Lapalala Wilderness Reserve. All 73 samples had previously tested negative with a reverse line blot assay.

The new method used nested PCR: two successive amplification rounds targeting a conserved part of the gltA gene, which increased the chance of detecting small amounts of Rickettsia DNA. The method found DNA in 32 of the 73 animals. This 44% value applies only to this deliberately selected set of previously negative samples and is not a prevalence estimate for South African wildlife.

Six wildlife species became new host records

First host records were reported for giraffe, common hippopotamus (Hippopotamus amphibius), impala (Aepyceros melampus), common warthog (Phacochoerus africanus), white rhinoceros (Ceratotherium simum) and plains zebra (Equus quagga). The single giraffe, hippopotamus and white rhinoceros samples were positive; four of 15 impalas, two of four warthogs and four of six plains zebras were also positive. Ratios based on one or a few animals describe the available samples and cannot be interpreted as population infection rates.

The giraffe record needs a taxonomic caveat. The sample came from Timbavati, within the South African range of southern giraffe (Giraffa giraffa), but the paper used the older collective name Giraffa camelopardalis and did not genetically identify the giraffe taxon. The link to southern giraffe is therefore based on geography rather than a species identification made by the study itself.

Sequencing succeeded for 27 positive PCR products. Most belonged to the spotted-fever group, three were closest to typhus-group bacteria and one resembled the transitional-group species Rickettsia felis. One zebra sequence could not be placed confidently, and one impala sample contained DNA signatures from both spotted-fever- and typhus-group bacteria. Because the short gltA fragment is highly conserved, most detections could not be resolved confidently to species or strain.

DNA detection did not establish active disease or reservoir status

Blood, liver, lymph-node and spleen material from two impalas was positive, which the authors interpret as preliminary evidence that rickettsial material can be distributed through several tissues. The study did not determine whether those animals were ill.

Detecting DNA alone cannot show whether live bacteria were present, whether infection was active, or whether a wildlife host can infect feeding ticks and maintain transmission in nature. Residual DNA after a cleared infection is another possibility. For that reason, the authors do not classify any of the six newly recorded species as reservoirs.

The authors recommend multi-gene sequencing, culture or RNA-based tests, together with pathology and vector surveillance, to determine what these detections mean biologically. The study therefore expands the known map of wildlife associations with Rickettsia in South Africa; it does not document a new outbreak.

Sources and image credit

  1. Cossu, C. A., Menandro, M. L., Mondin, A., Dotto, G., Bhoora, R. V., & van Heerden, H. (2026). Improved detection and sequencing of Rickettsia spp. DNA in South African wildlife. Veterinary Medicine and Science, 12(4), e71000. https://doi.org/10.1002/vms3.71000Primary peer-reviewed study first published 28 May 2026. Nested gltA PCR detected Rickettsia DNA in 32 of 73 previously reverse-line-blot-negative wildlife samples and produced new host records for six species; DNA detection alone did not establish active infection or reservoir status.

Image: Gail J. Cohen / Wikimedia Commons — white rhinoceros (Ceratotherium simum) at Lalibela Game Reserve, Eastern Cape, South Africa, photographed 21 February 2009; representative image of one of the six newly recorded wildlife hosts, not a study sample · CC BY 3.0 — https://creativecommons.org/licenses/by/3.0/ · Source

About this content: This story was produced with AI assistance within an editorial workflow developed by Wildlife Vagabond. Editorial responsibility remains with Wildlife Vagabond.How AI is used

Disease, parasites & microbiology

SPECIES IN THIS STORY

Species in this story

Southern Giraffe Giraffa giraffa Explore species Common Hippopotamus Hippopotamus amphibius Explore species Impala Aepyceros melampus Explore species Common Warthog Phacochoerus africanus Explore species White Rhinoceros Ceratotherium simum Explore species Plains Zebra Equus quagga Explore species

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