Abstract
In order to investigate the extent of genetic diversity among Ehrlichia ruminantium strains in Cameroon, a partial fragment (800 bp) of the E. ruminantium map1 gene was amplified by nested polymerase chain reaction in 121 of 156 E. ruminantium pCS20-positive DNA samples extracted from ticks and cattle collected from two ranches. Deoxyribonucleic acid sequencing of the map1 gene products indicated the presence of at least 21 genotypes at the nucleotide level and 16 genotypes at the amino acid level circulating within the study sites. Some of the genotypes were identical to Antigua (U50830), Blaaukrans (AF368000) or UmBanein (U50835), whilst the others were new genotypes. Twenty-four representative sequences were deposited in GenBank and given accession numbers JX477663 - JX477674 (for sequences of tick origin) and JX486788 - JX486799 (for sequences of cattle origin). Knowledge of E. ruminantium strain diversity could be important in understanding the epidemiology of heartwater.
Highlights
Ehrlichia ruminantium, the causative agent of heartwater in domestic and wild ruminants, is an obligate intracellular Gram-negative and pleomorphic bacterium
One hundred and fifty-six E. ruminantium-pCS20-positive deoxyribonucleic acid (DNA) samples were extracted from A. variegatum ticks (144) and cattle (12) originating from two ranches (Société de Développement et d’Exploitation des Productions Animales [SODEPA] Dumbo ranch [SDR] and Upper Farms ranch [UFR]), as previously described by Esemu et al (2013), were included in this study
Sequence analysis of map1 polymerase chain reaction (PCR) products revealed several genotypes of E. ruminantium circulating in A. variegatum ticks and the cattle host in the study sites
Summary
The causative agent of heartwater in domestic and wild ruminants, is an obligate intracellular Gram-negative and pleomorphic bacterium. It is transmitted by ticks of the genus Amblyomma (Dumler et al 2001; Uilenberg 1983), with Amblyomma variegatum being reported as the most efficient vector of this pathogen (Waghela et al 1991). In Cameroon, the economic impact of heartwater in domestic ruminants is recognised, but not yet well-documented (Ndi et al 1998). There has not been any report of the control of heartwater by immunisation
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