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Dual stresses of flooding and agricultural land use reduce earthworm populations more than the individual stressors
Global climate change is leading to a significant increase in flooding events in many countries. Current practices to prevent damage to downstream urban areas include allowing the flooding of upstream agricultural land. Earthworms are ecosystem engineers, but their abundances in arable land are already reduced due to pressure from farming practices. If flooding increases on agricultural land, it is important to understand how earthworms will respond to the dual stresses of flooding and agricultural land use. The earthworm populations under three land uses (pasture, field margin, and crops), across two UK fields, were sampled seasonally over an 18-month period in areas of the fields which flood frequently and areas which flood only rarely. Earthworm abundance in the crop and pasture soils and total earthworm biomass in the crop soils was significantly lower in the frequently flooded areas than in the rarely flooded areas. The relative percentage difference in the populations between the rarely and frequently flooded areas was greater in the crop soils (β59.18% abundance, β63.49% biomass) than the pasture soils (β13.39% abundance, β9.66% biomass). In the margin soils, earthworm abundance was significantly greater in the frequently flooded areas (+140.56%), likely due to higher soil organic matter content and lower bulk density resulting in soil conditions more amenable to earthworms. The findings of this study show that earthworm populations already stressed by the activities associated with arable land use are more susceptible to flooding than populations in pasture fields, suggesting that arable earthworm populations are likely to be increasingly at risk with increased flooding
Role of Position 627 of PB2 and the Multibasic Cleavage Site of the Hemagglutinin in the Virulence of H5N1 Avian Influenza Virus in Chickens and Ducks
Highly pathogenic H5N1 avian influenza viruses have caused major disease outbreaks in domestic and free-living birds with transmission to humans resulting in 59% mortality amongst 564 cases. The mutation of the amino acid at position 627 of the viral polymerase basic-2 protein (PB2) from glutamic acid (E) in avian isolates to lysine (K) in human isolates is frequently found, but it is not known if this change affects the fitness and pathogenicity of the virus in birds. We show here that horizontal transmission of A/Vietnam/1203/2004 H5N1 (VN/1203) virus in chickens and ducks was not affected by the change of K to E at PB2-627. All chickens died between 21 to 48 hours post infection (pi), while 70% of the ducks survived infection. Virus replication was detected in chickens within 12 hours pi and reached peak titers in spleen, lung and brain between 18 to 24 hours for both viruses. Viral antigen in chickens was predominantly in the endothelium, while in ducks it was present in multiple cell types, including neurons, myocardium, skeletal muscle and connective tissues. Virus replicated to a high titer in chicken thrombocytes and caused upregulation of TLR3 and several cell adhesion molecules, which may explain the rapid virus dissemination and location of viral antigen in endothelium. Virus replication in ducks reached peak values between 2 and 4 days pi in spleen, lung and brain tissues and in contrast to infection in chickens, thrombocytes were not involved. In addition, infection of chickens with low pathogenic VN/1203 caused neuropathology, with E at position PB2-627 causing significantly higher infection rates than K, indicating that it enhances virulence in chickens