The influence of warp length on trawl dimension and catch of walleye pollock <Emphasis Type="Italic">Theragra chalcogramma</Emphasis> in a bottom trawl survey

ABSTRACT:   Variations in trawl dimension, bottom contact, and catch with differing warp lengths during walleye pollock surveys conducted by the Fisheries Research Agency were examined. The ratio of warp length to fishing depth (scope ratio) was set at 2.5, 3.0 and 3.5 at depths of 110 m. At a 2.5 scope ratio, the net mouth shape and footgear contact fluctuated, as the trawl door did not contact the bottom. Footgear contact was complete when the scope ratio was 3.0 or more. Walleye pollock, sculpins and flatfishes were the main catch in all tows, and the catch increased with scope ratio. There was no difference in the length frequency of walleye pollock ( n  = 300) captured at 2.5 and 3.0 scope ratio. However, the length frequency at 3.5 was significantly different from that of other scope ratios. These results suggest that at a scope ratio of 3.0 or more, the trawl door will not leave the bottom at any depths. To compliment echo surveys for walleye pollock, a 3.0 scope ratio would be optimal, since the catch data for a 3.5 scope ratio was dissimilar from that of scope ratios.     

The 3' terminal sequence of RNA1 of wheat spindle streak mosaic virus canadian isolate (WSSMV-C)

The sequence of the 3 terminal 1722 nucleotides (nts) of RNA1 of the type (Canadian) isolate of wheat spindle streak mosaic bymovirus (WSSMV-C) was determined. The sequence started within a single open reading frame (ORF), which was expected to encode the carboxyl terminus of the nuclear inclusion b protein (NIb) and the capsid protein (CP) of 294 amino acids, followed by a 3 untranslated region (UTR) of 237 nucleotides. The NIb and CP of WSSMV-C share 99 and 100% amino acid sequence identity with the corresponding proteins of WSSMV-French isolate (WSSMV-F), but only 89 and 77% with wheat yellow mosaic virus (WYMV-J), respectively. The 3UTR of RNA1 of WSSMV-C shares 94% nucleotide sequence identity with that of WSSMV-F but only 73% with WYMV-J and WYMV-Chinese isolate (WYMV-Chi). The results support the classification of WSSMV-C and WSSMV-F as strains of the same virus species which is distinct from WYMV.     

Further assessment of houseflies (Musca domestica) as vectors for the mechanical transport and transmission of porcine reproductive and respiratory syndrome virus under field conditions

The purpose of this study was to evaluate the potential for houseflies (Musca domestica) to mechanically transport and transmit porcine reproductive and respiratory syndrome virus (PRRSV) between pig populations under controlled field conditions. The study employed swine housed in commercial livestock facilities and a release-recapture protocol involving marked (ochre-eyed) houseflies. To assess whether transport of PRRSV by insects occurred, ochre-eyed houseflies were released and collected from a facility housing an experimentally PRRSV-inoculated population of pigs (facility A) and collected from a neighboring facility located 120 m to the northwest that housed a naïve pig population (facility B). All samples were tested for PRRSV RNA by polymerase chain reaction (PCR). To assess transmission between the 2 populations, blood samples were collected from naïve pigs in facility B at designated intervals and tested by PCR. A total of 7 replicates were conducted. During 2 of 7 replicates (1 and 5), PCR-positive ochre-eyed houseflies were recovered in facility B and pigs in this facility became infected with PRRSV. Chi-squared analysis indicated that the presence of PRRSV in an insect sample was significantly (P = 0.0004) associated with infection of facility B pigs. Porcine reproductive and respiratory syndrome virus was not recovered from other reported routes of transmission during the study period, including air, fomites, and personnel. In conclusion, while an insufficient number of replicates were conducted to predict the frequency of the event, houseflies may pose some level of risk for the transport and transmission of PRRSV between pig populations under field conditions.     

Diagnostic value of recombinant nanoluciferase fused Toxoplasma gondii antigens in Luciferase-linked Antibody Capture Assay (LACA) for Toxoplasma infection in pigs

Toxoplasmosis is a widespread protozoan zoonosis. Since ingesting undercooked meat harboring Toxoplasma gondii cyst is considered one of the major transmission routes to humans, the screening of T. gondii in meat-producing animals can reduce the risk of food-borne toxoplasmosis in humans. Among serological diagnostic methods, Luciferase-linked Antibody Capture Assay (LACA) has been found to be a promising platform with high sensitivity and specificity. In this study, we aimed to evaluate recombinant nanoluciferase fused-T. gondii antigens (rNluc-GRA6, rNluc-GRA7, rNluc-GRA8 and rNluc-BAG1) for their potential use in LACA for pigs. As a result, the sensitivity of GRA6-, GRA7-, GRA8- and BAG1-LACA were 70.0%, 80.0%, 80.0% and 30.0% with specificity 87.0%, 81.5%, 74.1% and 50.0%, respectively. The cocktail LACA using a mixture of rNluc-GRA6, rNluc-GRA7 and rNluc-GRA8 indicated higher sensitivity (90.0%) and a similar specificity (96.3%) in comparison with the commercial ELISA kit. Compared to the Dye-Test as a reference test, cocktail LACA showed strong agreement (kappa value=0.811) when we assessed pig sera collected at the slaughterhouse. In addition, we also successfully established the rapid LACA format for the detection of Toxoplasma infection in pigs (called Rapid-LACA) in which the test could be performed within 30 min. In Rapid-LACA, the protein A pre-coated/blocked plates could be preserved at −30°C, 4°C or room temperature conditions for at least two months without compromising on the quality of assay.     

Long-term evaluation of the groundwater recharge function of paddy fields accompanying urbanization in the Nobi Plain, Japan

The groundwater recharge function, one example of the multifunctionality of agriculture, is closely related to hydrogeological phenomena and socioeconomic factors such as pumpage and land use. A long-term evaluation of the groundwater recharge function is necessary to understand its role among the multiple functions of agriculture. The Nobi Plain, one of the largest coastal plains in Japan, was selected as the study area because it has experienced typical socioeconomic changes. We conducted a long-term evaluation of the groundwater recharge function based on simple water-balance equations using long-term data on groundwater levels and river flows. Leakage recharge from paddy fields in 1975 was about 2.8×10⁸ m³/year, decreased to 0.6×10⁸ m³/year in 1984, and ceased in 1985. Its monetary value of the function in 1975 was estimated by the replacement cost method, was about $56 million for 20 ha×10³ ha of paddy fields. The value per unit area of paddy fields was calculated as $2820/ha and that in Japan was calculated as $400/ha. Paddy fields in suburbs of big cities have a higher value than the average paddy field in Japan. However, this recharge value is no longer produced because no leakage recharge occurs at present owing to socioeconomic changes.     

Fluctuation of NO3-N in groundwater of the reservoir of the Sunagawa Subsurface Dam, Miyako Island, Japan

The Japanese government started to construct two subsurface dams on Miyako Island in 1988, and the project was completed in 2001. Before the construction of the dams, the NO₃-N concentration of groundwater on the island was about 10 mg/l, the upper limit for drinking water in Japan, owing to the application of fertilizer to sugarcane fields. Predicting the effect of these subsurface dams on the groundwater environment was difficult because they were probably the first mega-subsurface dams in the world. We measured the NO₃-N concentration in the groundwater at observation wells before and after construction of the Sunagawa Dam and after the groundwater began to be used. We also measured the NO₃-N concentration monthly at a typical observation well in the catchment over a period 14 years to evaluate the environmental impact of construction of the dam. The highest NO₃-N concentrations were downstream before completion of the subsurface dam, and a high NO₃-N concentration zone remained around the cut-off wall after its completion, but this high-concentration zone disappeared and the distribution of NO₃-N became uniform after pumping of the groundwater began. Overall, the NO₃-N concentration decreased gradually. These results show that the groundwater quality did not deteriorate as a result of the construction of the Sunagawa Subsurface Dam.     

Detection and molecular characterization of bovine leukemia virus in beef cattle presented for slaughter in Egypt

Bovine leukemia virus (BLV) is the etiological agent of enzootic bovine leukosis, the most common neoplastic disease of cattle worldwide and a serious problem for the cattle industry. Previous studies have shown the molecular prevalence of BLV and the coexistence of BLV genotype-1 and -4 in Egyptian dairy cattle; however, the molecular characteristics of BLV in Egyptian beef cattle are unknown. Therefore, we collected blood samples of 168 beef cattle from slaughterhouses in three governorates in Egypt. Based on BLV-CoCoMo-qPCR-2 targeting long terminal repeats and nested PCR targeting the env-gp51 gene, the BLV provirus infection rates were found to be 47/168 (28.0%) and 42/168 (25.0%), respectively. Phylogenetic analysis based on 501 bp of the BLV env-gp51 gene from 42 BLV isolates revealed that at least six distinctive strains (b, e, f, g, x, and z) were prevalent in cattle across the examined regions. Furthermore, phylogenetic analysis of the 420 bp sequence of the BLV env-gp51 region of the six strains against 11 known genotypes showed that the strains b, e, f, and g were clustered into genotype-1, and strains x and z were clustered into genotype-4. Our results also indicated that strains b and x exist in both dairy and beef cattle in Egypt. The present study is the first to detect and genotype BLV among beef cattle in Egypt.