Genetic evolution of Mycoplasma capricolum subsp. capripneumoniae strains and molecular epidemiology of contagious caprine pleuropneumonia by sequencing of locus H2     

Lorenzon S  Wesonga H  Ygesu L  Tekleghiorgis T  Maikano Y  Angaya M  Hendrikx P  Thiaucourt F 《Veterinary microbiology》2002,85(2):111-123

Contagious caprine pleuropneumonia (CCPP) is a major threat to goat farming in developing countries. Its exact distribution is not well known, despite the fact that new diagnostic tools such as PCR and competitive ELISA are now available. The authors developed a study of the molecular epidemiology of the disease, based on the amplification of a 2400 bp long fragment containing two duplicated gene coding for a putative membrane protein. The sequence of this fragment, obtained on 19 Mycoplasma capricolum subsp. capripneumoniae (Mccp) strains from various geographical locations, gave 11 polymorphic positions. The three mutations found on gene H2prim were silent and did not appear to induce any amino acid modifications in the putative translated protein. The second gene may be a pseudogene not translated in vivo, as it bore a deletion of the ATG codon found in the other members of the "Mycoplasma mycoides cluster" and as the six mutations evidenced in the Mccp strains would induce modifications in the translated amino acids. In addition, an Mccp strain isolated in the United Arab Emirates showed a deletion of the whole pseudogene, a further indication that this gene is not compulsory for mycoplasma growth. Four lineages were defined, based on the nucleotide sequence. These correlated relatively well with the geographical origin of the strains: North, Central or East Africa. The strain of Turkish origin had a sequence similar to that found in North African strains, while strains isolated in Oman had sequences similar to those of North or East African strains. The latter is possibly due to the regular import of goats of various origins. Similar molecular epidemiology tools have been developed by sequencing the two operons of the 16S rRNA gene or by AFLP. All these various techniques give complementary results. One (16S rRNA) offers the likelihood of a finer identification of strains circulating in a region, another (H2) of determining the geographical origin of the strains. These tools can make a very useful contribution to understanding the epidemiology of CCPP.  相似文献   

Catchment Rehabilitation and Hydro‐geomorphic Characteristics of Mountain Streams in the Western Rift Valley Escarpment of Northern Ethiopia     

Tesfaalem G. Asfaha  Amaury Frankl  Mitiku Haile  Jan Nyssen 《Land Degradation \u0026amp; Development》2016,27(1):26-34

The catchments in the western Rift Valley escarpment of northern Ethiopia are highly responsive in terms of hydro‐geomorphic changes. With deforestation, dense gully and scar networks had developed by the 1980s on the escarpment between the towns of Alamata and Korem, transporting huge amounts of runoff and sediment down to the fertile and densely populated Raya Valley. To reverse this problem, catchment‐scale rehabilitation activities were initiated in the mid‐1980s. In this study, we examine the major hydro‐geomorphic response of streams after catchment rehabilitation. Scar networks in 20 adjacent catchments were mapped on Google Earth imagery of 2005, and their density was explained in terms of its corresponding Normalized Difference Vegetation Index and slope gradient. Soil and water conservation measures and vegetation recovery have reduced discharge and sediment flow which in turn resulted in various hydro‐geomorphic changes. In a multiple regression analysis, scar density was negatively related with Normalized Difference Vegetation Index and positively with average gradient of very steep slopes (r² = 0·53, p < 0·01, n = 20). The size and amount of sediment supply to streams decreased, and various channel adjustments occurred. Notably, previously braided streams have changed to single thread streams, lateral bars have been stabilized and stream channels are narrowing and incising. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Land Use and Cover Dynamics Since 1964 in the Afro‐Alpine Vegetation Belt: Lib Amba Mountain in North Ethiopia     

Miro Jacob  Liên Romeyns  Amaury Frankl  Tesfaalem Asfaha  Hans Beeckman  Jan Nyssen 《Land Degradation \u0026amp; Development》2016,27(3):641-653

Human‐induced land use and land cover (LUC) changes threaten the ecosystem services of the vulnerable tropical afro‐alpine vegetation. Several LUC change studies are available for the Ethiopian highlands, but relatively little is known about LUC change in the afro‐alpine zones. In this study, LUC changes between 1964 and 2012 were mapped for the afro‐alpine zone of Lib Amba Mountain, part of the Abune Yosef Mountains in North Ethiopia. Historical LUC was derived from georeferenced aerial photographs of 1964 and 1982, and the present LUC (2012) from Bing Map satellite imagery. Based on these successive LUC maps a time‐depth map, LUC proportions, LUC transition matrices and LUC change trajectories were calculated. Two main phases of LUC change could be distinguished linked to the neo‐Boserupian perspective. (i) Between 1964 and 1982, there were large‐scale deforestation and general degradation of the vegetation above 3500 m, in a period of low population pressure; (ii) Between 1982 and 2012, an intensification of land use prevailed accompanied with a slight regeneration of the vegetation and the Erica arborea L. forest, under increased population pressure. Depth interviews indicated that local and governmental land management measures are very important for the protection against vegetation depletion and soil degradation. Quick recovery of the forest on Lib Amba provides confidence that degraded afro‐alpine areas would benefit in a short time from complete protection, given the vicinity of remaining patches of afro‐alpine vegetation. Management interventions are thus vital to restore the important ecosystem services of the afro‐alpine vegetation belt. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Combining isotopic signatures of n(Sr)/n(Sr) and light stable elements (C,N, O,S) with multi-elemental profiling for the authentication of provenance of European cereal samples     

Daniel Goitom Asfaha  Christophe R. Quétel  Freddy Thomas  Micha Horacek  Bernhard Wimmer  Gerhard Heiss  Christian Dekant  Peter Deters-Itzelsberger  Stefan Hoelzl  Susanne Rummel  Christophe Brach-Papa  Marleen Van Bocxstaele  Eric Jamin  Malcolm Baxter  Katharina Heinrich  Simon Kelly  Daniela Bertoldi  Luana Bontempo  Federica Camin  Roberto Larcher  Matteo Perini  Andreas Rossmann  Antje Schellenberg  Claus Schlicht  Heinz Froeschl  Jurian Hoogewerff  Henriette Ueckermann 《Journal of Cereal Science》2011

The aim of this work (from the FP6 project TRACE) was to develop methods based on the use of geochemical markers for the authentication of the geographical origin of cereal samples in Europe (cf. EC regulations 2081/92 and 1898/06). For the first time, the potential usefulness of combining n(⁸⁷Sr)/n(⁸⁶Sr) and δ¹³C, δ¹⁵N, δ¹⁸O and δ³⁴S isotopic signatures, alone or with key element concentrations ([Na], [K], [Ca], [Cu] and [Rb], progressively identified out of 31 sets of results), was investigated through multiple step multivariate statistics for more than 500 cereal samples collected over 2 years from 17 sampling sites across Europe representing an extensive range of geographical and environmental characteristics.  相似文献   

Sediment in Alluvial and Lacustrine Debris Fans as an Indicator for Land Degradation Around Lake Ashenge (Ethiopia)     

Sil Lanckriet  Tesfaalem Asfaha  Amaury Frankl  Amanuel Zenebe  Jan Nyssen 《Land Degradation \u0026amp; Development》2016,27(2):258-269

Sediments deposited by (paleo) flash floods can hold valuable information on processes of environmental change, land degradation or desertification. In order to assess the suitability of flash flood deposits as proxies for land degradation, we monitored a representative gully segment in North Ethiopia (Ashenge catchment), investigated a sequence of alluvial debris fans downstream of this segment and dated a neighbouring subaquatic debris fan using short‐lived ²¹⁰Pb isotope counting. During one rainy season (July–September 2014), we measured daily rainfall, peak discharge, bedload transport, suspended sediment load and sediment deposition rates. The data show that sediment deposition in the debris fans is significantly dependent on micro‐topography (net incision in micro‐channels) (p < 0·1) and position within the sequence (net incision farther away from the lake) (p < 0·05). As sediment transfer to the lake significantly depends on the balance between available water and sediment (ratio rainfall depth/bedload transport) (p < 0·05), we could reconstruct the hydro‐sedimentary evolution of the gully over the past half century and validate it with aerial photographs and semi‐structured interviews. The findings are consistent with the short‐lived isotope count results, indicating increased sediment supply from the 1970s onwards, when little amounts of clay were deposited in the lake (<5%), and a subrecent clear water effect that resulted in increased deposition rates of clay in the lacustrine debris fan. Overall, our analysis indicates that debris fan sediments can be used to estimate past environmental degradation rates, if the contemporary water and sediment behaviour is well understood. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献