Repetitive sequences in the ITS1 region of the ribosomal DNA of Tunga penetrans and other flea species (Insecta, Siphonaptera)

Abstract

Different Tunga penetrans isolates from various hosts obtained from South America (Fortaleza. Brazil) have been studied by nucleotide sequence comparison of the first and the second internal transcribed spacer (ITS1, ITS2) of the ribosomal deoxyribonucleic acid (rDNA) and part of the mitochondrial 16S rDNA. Results show no significant host-dependent sequence differences. No indication for intraindividual and intraspecific polymorphisms could be detected. Comparing the ITS1 spacer region of T. penetrans from South America with that from Africa (Togo, Cameroon), distinct length variations have been observed caused by a repetitive sequence motif of 99 bp. The ITS1 from the South American T. penetrans contain two tandemly repeated copies, whereas four of these units are present in the spacer of the African T. penetrans. The absence of homogenization of these units indicates a recent separation of both populations. However, the different number of repetitions together with two base substitutions put the evolutionary distance of only 135 years as postulated for the transfer of T. penetrans from South America to Africa into question. Repetitive sequences could also be detected within the ITS1 rDNA region of other flea species Ctenocephalides felis, Echidnophaga gallinacea, Pulex irritans, Spilopsyllus cuniculi, and Xenopsylla cheopis. The repeat units with lengths from 10 to 99 bp are arranged in pure tandem or interspersed. The repetitive elements observed in the ITS1 of various flea species may serve as a valuable tool for phylogeographic studies.

Ctenocephalides felis and Ctenocephalides canis: introgressive hybridization?

“…Nevertheless, other authors such as Gamerschlag et al . () reported different lengths in the ITS1 nucleotide sequences in other species of fleas ( Tunga penetrans from Africa and South America).…”

Tungiasis-related knowledge and treatment practices in two endemic communities in northeast Brazil

“…Many informants were convinced that at least two different species of sand fleas exist, which could be differentiated by their colour and which differ somewhat in their capacity to cause inflammation and pain ( Table 2). In fact, recent evidence indicates that in the area where this study was performed, at least two variants of T. penetrans occur that show a considerable degree of genetic heterogeneity [25]. Interestingly, recently a new pathogenic Tunga species (Tunga trimamillata) has been described from Ecuador [26].…”

Sand flea (Tunga spp.) infections in humans and domestic animals: state of the art

“…A recent survey on Brazilian and African samples, based on length differences of ribosomal ITS1 (Gamerschlag et al ., 2008), further splits the ‘Atlantic’ clade into two groups, each of which belongs to the respective continent (Fig. 4).…”

“…The same sector's pattern within a pie indicates the same haplotype; the amplitude of each pie's sector is proportional to the frequency of the corresponding haplotype in the given population. The schematic tree indicates the phylogenetic relationships between Tunga populations as resulted from ITS2 nuclear markers analyses (black lines; Luchetti et al ., 2005c, 2007) and ITS1 (grey lines; Gamerschlag et al ., 2008).…”