versão impressa ISSN 0030-2465
Onderstepoort j. vet. res. vol.79 no.1 Cape Town Jan. 2012
Ivan G. HorakI; Heike LutermannII; Katarina MedgerII; Dmitry A. ApanaskevichIII; Conrad A. MattheeIV
IDepartment of Veterinary Tropical Diseases, University of Pretoria, South Africa
IIDepartment of Zoology and Entomology, University of Pretoria, South Africa
IIIUnited States National Tick Collection, Georgia Southern University, USA
IVDepartment of Botany and Zoology, Stellenbosch University, South Africa
The first collection of unengorged and fully engorged larvae of Nuttalliella sp. (N. namaqua?) from the murid rodents Micaelamys namaquensis, Aethomys chrysophilus and Acomys spinosissimus in Limpopo Province and from M. namaquensis in the Northern Cape Province, South Africa, is documented. A total of nine larvae were collected from two M. namaquensis in the Soutpansberg mountain range in the Limpopo Province during April 2009. During the last week of September 2011, 221 larvae were collected from rodents at the same locality and 10 of 48 M. namaquensis, 6 of 12 Ae. chrysophilus and 3 of 14 Ac. spinosissimus were infested. One of the M. namaquensis harboured 53 larvae. Five larvae were collected from two M. namaquensis in the Northern Cape Province. Total genomic DNA was extracted from two larvae and a region of the 18S rRNA gene was sequenced for these. BLASTn searches revealed similarity between these specimens and the Nuttalliella sequences published on GenBank.
The collection of larvae, nymphs and females of Nuttalliella namaqua during 2011, after many years in which none had been detected, has revived interest in the morphology, hosts and biology of this unusual tick (Mans et al. 2011). Nymphs and females from this collection have successfully been fed on laboratory-infested lizards (Mans et al. 2011).
Various papers on the role of murid rodents as hosts of immature ixodid ticks in South Africa have recently been published (Matthee et al. 2007; Matthee et al. 2010; Petney et al. 2004). The present communication records their role as hosts of the larvae of Nuttalliella sp. (N. namaqua?). Two studies were conducted in Goro Game Reserve (22º58'S, 29º25'E) located in the Soutpansberg mountain range, Limpopo Province, South Africa. Both studies focused on various aspects of the biology of rock elephant shrews (Elephantulus myurus), and included collecting ticks from these small mammals. Animals were trapped with baited Sherman live traps set overnight on rocky outcrops. In addition to the elephant shrews, a number of murid rodents were trapped and also examined for ticks. Animals were collected during April and May 2009, and during the last week of September 2011. The animals were collected under permit number CPM-333-00002 issued by the Department of Environmental Affairs, Limpopo Province, South Africa, and all procedures were approved by the Animal Ethics Committee of the University of Pretoria (EC028-07, V052-11).
A third study was conducted during 2009 on the farm Plaatfontein (31º02'S, 23º46'E) in the eastern region of the Northern Cape Province. It focused on collecting biological data and also ticks from Southern African hedgehogs, (Atelerix frontalis) (Horak et al. 2011), under permit FLORA 036/2009 issued by the Northern Cape Department of Tourism, Environment and Conservation. However, a number of murid rodents were also trapped and examined for ticks.
After removal from the traps the body of each animal was searched for ticks, and particular attention was given to the ear margins, legs and the base of the tail, where ticks aggregated. The rest of the body was searched by back-combing the fur. All ticks were removed using fine-tipped forceps and placed in 70% ethanol, after which the host animals were released.
In the first study, five Nuttalliella sp. larvae were collected during April 2009 from a Namaqua rock mouse (Micaelamys namaquensis) and four from another. Two of the nine larvae were engorged. These are the first recorded collections of the larvae of this tick from host animals. Not one of the 58 rock elephant shrews, or remaining 141 rock mice or 8 spiny mice (Acomys spinosissimus) examined at the same time was infested. In the second study, 221 unengorged and engorged Nuttalliella sp. larvae were collected. Of these, 154 larvae were recovered from 10 of 48 M. namaquensis examined, 58 from 6 of 12 red veld rats (Aethomys chrysophilus), and 9 larvae from 3 of 14 Ac. spinosissimus (Table 1). One of the M. namaquensis harboured a total of 53 larvae, whilst the comparatively large number of larvae collected from the 6 Ae. chrysophilus and the fact that 50% of the 12 examined were infested could imply that they are preferred hosts in Limpopo Province. Alternatively, but not mutually exclusive, this may be attributed to the greater body size of the Ae. chrysophilus (72.7 g ± 3.3, n = 12) compared to the M. namaquensis (39.0 g ± 0.9, n = 48). None of the 8 rock elephant shrews captured at the same time was infested. In the third study a total of five unengorged larvae were collected from two of an undisclosed number of M. namaquensis in the Northern Cape Province. Not one of the 12 hedgehogs examined at the same locality was infested.
Because the larvae of N. namaqua have not previously been collected from natural hosts, nor been described, we relied on morphological features resembling those described for the females to arrive at a diagnosis. As an adjunct to identification of the larvae on taxonomic features, total genomic DNA from two larvae collected from M. namaquensis was extracted using the Qiagen, DNeasy® Blood and Tissue kit. Polymerase chain reaction and sequencing was performed on the 18S rRNA gene fragment using conserved universal primers. Amplifications were performed following standard PCR protocols and cycle-sequencing reactions were performed using BigDye Chemistry. Products were analysed on an automated sequencer (ABI 3730 XL DNA Analyzer, Applied Biosystems).
A 466 base-pair region of the 18S rRNA gene was obtained for both larvae, and these sequences were aligned to the N. namaqua sequence on GenBank (Mans et al. 2011; JF751071.1). The region sequenced corresponds to positions 1093-1571 of the published sequence. The sequences generated for the two larvae in our study were identical. BLASTn searches on GenBank revealed 99.58% similarity (476/478) between the newly sampled individuals (GenBank Access Number JQ424828) and the 18S rRNA Nuttalliella sequence published on GenBank. Further support for the authenticity of our identification of the larvae was obtained by doing a GenBank BLASTn search against the entire database. The next closest alternative match to Nuttalliella would be the genus Ixodes, but in this instance the level of differentiation is more than 4% (614/640 identities between the larval sequences and that of Ixodes persulcatus: AY274888.1).
The larvae of a nuttalliellid tick, Nuttalliella sp. (N. namaqua?) can now be added to the immature stages of a large variety of ixodid tick species, which by preference feed on murid rodents.
We thank the management and staff of the Goro Game Reserve for permission to collect animals in the reserve and their continuous support. Stacey Hallam is thanked for collecting the ticks from mice in the Northern Cape Province. The sequences were generated by Lee-Gavin Williams and primers were provided by Anne Ropiquet. KM acknowledges a doctoral grant from the National Research Foundation (NRF), HL a Research Fellowship from the University of Pretoria and IGH funding from the University of Pretoria and the NRF.
The authors declare that they have no financial or personal relationship(s) which may have inappropriately influenced them in writing this paper.
I.G.H. (University of Pretoria) identified the ticks with the assistance of D.A.A. (Georgia Southern University), and also compiled the manuscript. H.L. (University of Pretoria) and K.M. (University of Pretoria) collected the ticks and did the statistical work, and C.A.M. (Stellenbosch University) was responsible for the molecular analysis.
Horak, I.G., Welman, S., Hallam, S.L., Lutermann, H. & Mzilikazi, N., 2011, 'Ticks of four-toed elephant shrews and Southern African hedgehogs', Onderstepoort Journal of Veterinary Research 78(1), Art. #243, 3 pages. http://dx.doi.org/10.4102/ojvr.v78i1.243 [ Links ]
Mans, B.J., De Klerk, D., Pienaar, R. & Latif, A.A., 2011, 'Nuttalliella namaqua: a living fossil and closest relative to the ancestral tick lineage: implications for the evolution of blood-feeding in ticks', PLoS ONE 6(8): e23675. http://dx.doi.org/10.1371/journal pone.0023675 [ Links ]
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Petney, T.N., Horak, I.G., Howell, D.J. & Meyer, S., 2004, 'Striped mice, Rhabdomys pumilio, and other murid rodents as hosts for immature ixodid ticks', Onderstepoort Journal of Veterinary Research 71, 313-318. PMid:15732458. [ Links ]
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Received: 18 Jan. 2012
Accepted: 23 Jan. 2012
Published: 02 Feb. 2012