Millennial-scale climate changes during the last glacial period and deglaciation were accompanied by rapid changes in atmospheric CO2 that remain unexplained. While the role of the Southern Ocean as ...a 'control valve' on ocean-atmosphere CO2 exchange has been emphasized, the exact nature of this role, in particular the relative contributions of physical (for example, ocean dynamics and air-sea gas exchange) versus biological processes (for example, export productivity), remains poorly constrained. Here we combine reconstructions of bottom-water O2, export production and (14)C ventilation ages in the sub-Antarctic Atlantic, and show that atmospheric CO2 pulses during the last glacial- and deglacial periods were consistently accompanied by decreases in the biological export of carbon and increases in deep-ocean ventilation via southern-sourced water masses. These findings demonstrate how the Southern Ocean's 'organic carbon pump' has exerted a tight control on atmospheric CO2, and thus global climate, specifically via a synergy of both physical and biological processes.
African swine fever (ASF) is an infectious transboundary disease of domestic pigs and wild swine and is currently the most serious constraint to piggery in Uganda. The causative agent of ASF is a ...large double-stranded linear DNA virus with a complex structure. There are twenty-four ASFV genotypes described to date; however, in Uganda, only genotypes IX and X have been previously described. Inadequate ASF outbreak investigation has contributed to the delayed establishment of effective interventions to aid the control of ASF. Continuous virus characterization enhances the understanding of ASF epidemiology in terms of viral genome variations, extent, severity, and the potential source of the viruses responsible for outbreaks. We collected samples from pigs that had died of a hemorrhagic disease indicative of ASF. DNA was extracted from all samples and screened with the OIE recommended diagnostic PCR for ASF. Partial B646L (p72), full-length E183L (p54) genes, and CVR region of the P72 gene were amplified, purified, and sequenced. Web-based BLAST and MEGA X software were used for sequence analysis. ASF was confirmed in 10 of the 15 suspected pig samples. Phylogenetic analysis confirmed circulation of genotype IX by both full-length E183 (p54) and partial B646L (p72) gene sequencing. Intragenotypic resolution of the CVR region revealed major deletions in the virus genome, in some isolates of this study. The marked reduction in the number of tetrameric tandem repeats in some isolates of this study could potentially play a role in influencing the virulence of this particular genotype IX in Uganda.
Rhipicephalus microplus, an invasive tick species of Asian origin and the main vector of Babesia species, is considered one of the most widespread ectoparasites of livestock. The tick has spread from ...its native habitats on translocated livestock to large parts of the tropical world, where it has replaced some of the local populations of Rhipicephalus decoloratus ticks. Although the tick was reported in Uganda 70 years ago, it has not been found in any subsequent surveys. This study was carried out to update the national tick species distribution on livestock in Uganda as a basis for tick and tick-borne disease control, with particular reference to R. microplus.
The study was carried out in Kadungulu, Serere district, south-eastern Uganda, which is dominated by small scale livestock producers. All the ticks collected from 240 cattle from six villages were identified microscopically. Five R. microplus specimens were further processed for phylogenetic analysis and species confirmation.
The predominant tick species found on cattle was Rhipicephalus appendiculatus (86.9 %; n = 16,509). Other species found were Amblyomma variegatum (7.2 %; n = 1377), Rhipicephalus evertsi (2.3 %; n = 434) and R. microplus (3.6 %; n = 687). Phylogenetic analysis of the 12S rRNA, 16S rRNA and ITS2 gene sequences of R. microplus confirmed the morphological identification.
It is concluded that R. microplus has replaced R. decoloratus in the sampled villages in Kadungulu sub-county, since the latter was not any longer found in this area. There is currently no livestock movement policy in force in Uganda, which could possibly limit the further spread of R. microplus ticks. Future surveys, but also retrospective surveys of museum specimens, will reveal the extent of distribution of R. microplus in Uganda and also for how long this tick has been present on livestock without being noticed.
Turbulent bottom currents significantly influence the formation of cold-water coral mounds and sedimentation processes on continental slopes. Combining records from coral mounds and adjacent slope ...sediments therefore provide an unprecedented palaeo-archive to understand past variations of intermediate water-mass dynamics. Here, we present coral ages from coral mounds of the Belgica province (Porcupine Seabight, NE Atlantic), which indicate a non-synchronous Holocene re-activation in mound formation suggested by a temporal offset of ∼2.7 kyr between the deep (start: ∼11.3 ka BP at 950 m depth) and shallow (start: ∼8.6 ka BP at 700 m depth) mounds. A similar depth-dependent pattern is revealed in the slope sediments close to these mounds that become progressively younger from 22.1 ka BP at 990 m to 12.2 ka BP at 740 m depth (based on core-top ages). We suggest that the observed changes are the consequence of enhanced bottom-water hydrodynamics, caused by internal waves associated to the re-invigoration of the Mediterranean Outflow Water (MOW) and the development of a transition zone (TZ) between the MOW and the overlying Eastern North Atlantic Water (ENAW), which established during the last deglacial. These highly energetic conditions induced erosion adjacent to the Belgica mounds and supported the re-initiation of mound formation by increasing food and sediment fluxes. The striking depth-dependent patterns are likely linked to a shift of the ENAW-MOW-TZ, moving the level of maximum energy ∼250 m upslope since the onset of the last deglaciation.
•Holocene cold-water coral mound formation started non-synchronous in Belgica province.•Coral mounds and slope sediments record changes in intermediate water mass dynamics.•Increased turbulent bottom currents steered slope erosion and mound formation.•Internal waves at the ENAW-MOW boundary enhance energy supply and particle flux.•Transition zone between the ENAW-MOW shifted 250 m upslope during the last deglacial.
Lumpy skin disease (LSD) is an infectious viral disease of cattle caused by a Capripoxvirus. LSD has substantial economic implications, with infection resulting in permanent damage to the skin of ...affected animals which lowers their commercial value. In Uganda, LSD is endemic and cases of the disease are frequently reported to government authorities. This study was undertaken to molecularly characterize lumpy skin disease virus (LSDV) strains that have been circulating in Uganda between 2017 and 2018. Secondly, the study aimed to determine the phylogenetic relatedness of Ugandan LSDV sequences with published sequences, available in GenBank.
A total of 7 blood samples and 16 skin nodule biopsies were screened for LSDV using PCR to confirm presence of LSDV nucleic acids. PCR positive samples were then characterised by amplifying the GPCR gene. These amplified genes were sequenced and phylogenetic trees were constructed. Out of the 23 samples analysed, 15 were positive for LSDV by PCR (65.2%). The LSDV GPCR sequences analysed contained the unique signatures of LSDV (A11, T12, T34, S99, and P199) which further confirmed their identity. Sequence comparison with vaccine strains revealed a 12 bp deletion unique to Ugandan outbreak strains. Phylogenetic analysis indicated that the LSDV sequences from this study clustered closely with sequences from neighboring East African countries and with LSDV strains from recent outbreaks in Europe. It was noted that the sequence diversity amongst LSDV strains from Africa was higher than diversity from Eurasia.
The LSDV strains circulating in Uganda were closely related with sequences from neighboring African countries and from Eurasia. Comparison of the GPCR gene showed that outbreak strains differed from vaccine strains. This information is necessary to understand LSDV molecular epidemiology and to contribute knowledge towards the development of control strategies by the Government of Uganda.
The largest coherent cold-water coral (CWC) mound province in the Atlantic Ocean exists along the Mauritanian margin, where up to 100 m high mounds extend over a distance of ∼400 km, arranged in two ...slope-parallel chains in 400–550 m water depth. Additionally, CWCs are present in the numerous submarine canyons with isolated coral mounds being developed on some canyon flanks. Seventy-seven Uranium-series coral ages were assessed to elucidate the timing of CWC colonisation and coral mound development along the Mauritanian margin for the last ∼120,000 years. Our results show that CWCs were present on the mounds during the Last Interglacial, though in low numbers corresponding to coral mound aggradation rates of 16 cm kyr−1. Most prolific periods for CWC growth are identified for the last glacial and deglaciation, resulting in enhanced mound aggradation (>1000 cm kyr−1), before mound formation stagnated along the entire margin with the onset of the Holocene. Until today, the Mauritanian mounds are in a dormant state with only scarce CWC growth. In the canyons, live CWCs are abundant since the Late Holocene at least. Thus, the canyons may serve as a refuge to CWCs potentially enabling the observed modest re-colonisation pulse on the mounds along the open slope. The timing and rate of the pre-Holocene coral mound aggradation, and the cessation of mound formation varied between the individual mounds, which was likely the consequence of vertical/lateral changes in water mass structure that placed the mounds near or out of oxygen-depleted waters, respectively.
•Enhanced formation of Mauritanian coral mounds during the last glacial and deglacial.•Coral mound aggradation reached rates of up to 16 m kyr−1•Mauritanian corals mounds are in a dormant state since the Early Holocene.•Dissolved oxygen concentrations represent an important control on mound formation.•Submarine canyons offer a refuge for cold-water corals and act as source for larvae supply.
Contagious bovine pleuropneumonia CBPP is a transboundary animal disease of cattle caused by Mycoplasma mycoides subsp. mycoides Mmm. CBPP causes severe economic losses to livestock producers in ...sub-Saharan Africa mainly due to high mortality, morbidity, reduction in productivity as well as livestock trade restrictions. This study aimed at determining seroprevalence of Mmm in cattle from Karamoja region, north-eastern Uganda; data that are required to design and implement risk based CBPP control program.
We randomly collected blood samples from 2,300 cattle spread across Karamoja region. Serum was extracted and screened for antibodies against Mycoplasma mycoides subsp. mycoides Mmm using the competitive enzyme linked immunosorbent assay cELISA.
A quarter 25.4%; 95% CI: 23.7-27.3 of the screened cattle n = 2,300 were sero-positive for Mmm. Amudat and Kaabong districts recorded the lowest 12.3% and highest 30.7% Mmm seroprevalence respectively. Increasing age, overnight stay in cattle kraals and location certain districts, villages, herds and sub counties of the cattle herds, the factors that promote animal commingling, were the most significant risk factors of seroconversion with Mmm.
Results from this study indicated a higher seroprevalence of Mmm in Karamoja region cattle herds. This could be due to the increased frequency of CBPP outbreaks in recent years. To be effective, CBPP vaccination programs should target high risk herds along the international borders and other hotspot areas e.g., parishes or sub counties where cattle commingling is high.
The continued endemicity of foot and mouth disease virus (FMDV) in East Africa has significant implications for livestock production and poverty reduction, yet its complex epidemiology in endemic ...settings remains poorly understood. Identifying FMDV dispersal routes and drivers of transmission is key to improved control strategies. Environmental heterogeneity and anthropogenic drivers (e.g., demand for animal products) can impact viral spread by influencing host movements. Here, we utilized FMDV serotype O VP1 genetic sequences and corresponding spatiotemporal data in order to (i) infer the recent dispersal history, and (II) investigate the impact of external factors (cattle density, human population density, proximity to livestock markets, and drought) on dispersal velocity, location, and direction of FMDV serotype O in East Africa. We identified statistical evidence of long‐distance transmission events, and we found that FMDV serotype O tends to remain circulating in areas of high cattle density, high human population density, and in close proximity to livestock markets. The latter two findings highlight the influence of anthropogenic factors on FMDV serotype O spread in this region. These findings contribute to the understanding of FMDV epidemiology in East Africa and can help guide improved control measures.
Neodymium isotopic compositions (143Nd/144Nd or εNd) have been used as a tracer of water masses and lithogenic inputs to the ocean. To further evaluate the faithfulness of this tracer, we have ...updated a global seawater εNd database and combined it with hydrography parameters (temperature, salinity, nutrients and oxygen concentrations), carbon isotopic ratio and radiocarbon of dissolved inorganic carbon. Archive εNd data are also compiled for leachates, foraminiferal tests, deep-sea corals and fish teeth/debris from the Holocene period (<10,000years).
At water depths ≥1500m, property-property plots show clear correlations between seawater εNd and the other variables, suggesting that large-scale water mass mixing is a primary control of deepwater εNd distribution. At ≥200m, basin-scale seawater T-S-εNd diagrams demonstrate the isotopic evolution of different water masses. Seawater and archive εNd values are compared using property-property plots and T-S-εNd diagrams. Archive values generally agree with corresponding seawater values although they tend to be at the upper limit in the Pacific. Both positive and negative offsets exist in the northern North Atlantic. Applying multiple regression analysis to deep (≥1500m) seawater data, we established empirical equations that predict the main, large-scale, deepwater εNd trends from hydrography parameters. Large offsets from the predicted values are interpreted as a sign of significant local/regional influence. Dominant continental influence on seawater and archive εNd is observed mainly within 1000km from the continents. Generally, seawater and archive εNd values form gradual latitudinal trend in the Atlantic and Pacific at depths ≥600m, consistent with the idea that Nd isotopes help distinguish between northern/southern sourced water contributions at intermediate and deep water depths.
Hydrocarbon seeps are common manifestations of gas leakage from the seafloor. However, the fate of methane seepage within the gas hydrate stability zone at active margins is poorly constrained. This ...study presents a 40‐thousand‐year record of hydrocarbon seepage archived by a ∼5‐m long core composed of authigenic carbonate from the Yam Seep area, Four‐Way Closure Ridge off SW Taiwan. Different carbonate microfacies could be distinguished: Consolidated microcrystalline aragonite representing lithified host sediments intercalated by pure aragonite present in 10–50 cm thick intervals in the core. These aragonite intervals are interpreted as having precipitated within former fractures in the host rock. High resolution U‐Th dating of these aragonites is interpreted to record the minimum age of the opening of these fractures. The chronology of aragonite precipitation throughout the core suggests a record of continuous seepage from ∼41 to 2 ka that fluctuated in intensity over this time period. The chronology of putative fracturing events and observed carbonate precipitation suggest (a) an active period of fracturing and seepage from ∼37 to 27 ka, (b) a more quiescent period from ∼27 to 16 ka, followed by (c) another active period from ∼16 to 12 ka. A schematic model illustrates the evolution of carbonate formation within the core influenced by faulting, fracturing, erosion, gas hydrate accumulation, and aragonite precipitation and provides a unique 40,000‐year‐old record of methane seepage and crucial insights into the dynamics of long‐term seepage systems at active margins.
Key Points
A 40‐thousand‐year history of hydrocarbon seepage at an active margin accretionary ridge off SW Taiwan
Uranium‐Thorium dating of authigenic carbonate reveals alternating periods of seepage activity and quiescence
Dating of fracture boundaries provides evidence for episodes of tectonic and seepage activities
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