Ehrlichia ruminantium, Sudan

To the Editor: Ehrlichia ruminantium, the causative agent of heartwater, is transmitted by Amblyomma spp. ticks. Amblyomma variegatum ticks, which are found in the Caribbean and sub-Saharan Africa, except in certain areas of southern Africa, are major vectors of E. ruminantium (1–3). A. lepidum is also an important vector of heartwater, especially in eastern Sudan (4). However, few epidemiologic data exist on infection rates of Amblyomma spp. ticks and distribution of E. ruminantium in Sudan. A polymerase chain reaction (PCR) assay that uses DNA probe pCS20 has been developed for detecting E. ruminantium (5). Another PCR assay for the major antigen protein 1 gene (map1) has been used to differentiate strains of E. ruminantium (6,7). These PCR assays have high sensitivity and specificity for the amplification of E. ruminantium DNA (6,8). For epidemiologic study of E. ruminantium in Sudan, we used PCR to detect E. ruminantium DNA in ticks. We also sequenced PCR products to identify the genotype of E. ruminantium. The pCS20 DNA fragment of E. ruminantium was detected in 8 (8.2%) of 97 A. variegatum ticks and 2 (1.9%) of 106 A. lepidum ticks (χ2 = 3.123, by Yates correction). The nucleotide sequences (279 bp) obtained from 5 A. variegatum ticks and 1 A. lepidum tick were identical (GenBank accession no. AB218277). The sequences were similar to those of Welgevonden, Vosloo, and Ball3 strains from southern Africa and Gardel strain from the Caribbean islands (similarity = 99.64%). The pCS20 sequences obtained in this study were different from those of strains from western Africa. An 855-bp map1 nucleotide sequence obtained from 1 A. lepidum tick was provisionally named Gedaref (GenBank accession no. AB218278). The nucleotide sequence of Gedaref was found to be closely related to those of Senegal and Pokoase strains from western Africa and to South Africa Canine and Kümm1 strains from southern Africa (similarity = 90.53%– 97.43%). Gedaref clustered with these 4 strains and with 6 other strains, including Kiswani from eastern Africa and Antigua from the Caribbean islands (Figure). In contrast, the nucleotide sequence of Gedaref showed 84.8% similarity with that of Um Banein, which has been known as the only strain of E. ruminantium in Sudan. Um Banein formed another cluster with Gardel, Lutale, and Umpala strains from southern Africa (Figure). The map1