Visible Light-Induced Reactive Yellow 145 Discoloration: Structural and Photocatalytic Studies of Graphene Quantum Dot-Incorporated TiO2.

Visible light-induced photocatalytic treatment of organic waste is considered a green and efficient route. This study explored the structural and photocatalytic performance of graphene quantum dot (GQD)-incorporated TiO2 nanocomposites to treat reactive yellow 145 (RY145) dye. For the effective removal of the RY145, efforts were made to better understand the kinetics of the process and optimization of the treatment parameters. Different GQD-doped TiO2 nanocomposites were synthesized employing the sol-gel method. Physicochemical characteristics of the synthesized nanocomposites were studied through FTIR, XRD, UV-visible spectroscopy, SEM, and EDX. Screening studies were conducted for synthesis and reaction optimization. The results indicated that GQD-TiO2 significantly enhanced the photocatalytic discoloration for RY145 dye. Among the synthesized nanocomposites, 15GQD-TiO2 calcined at 300 exhibited 99.3% RY145 discoloration in 30 min under visible light irradiation. Following the pseudo-first-order reaction, the photocatalytic reaction constant K app progressively declined with an increase in the concentration of RY145. The heterogeneous reaction system conformed to the Langmuir-Hinshelwood isotherm, as indicated by the K C (1.08 mg L-1 min-1) and the K LH (0.18 L mg-1) values. O2 •- was found to be the major contributor in GQD-TiO2-300 to decolorize RY154, while TiO2 and GQDs played a vital role in generation of electrons and holes. Additionally, after recycling to the seventh cycle, only 9% decline in photocatalytic performance was observed for the synthesized nanocomposite.

Genetic diversity of Ehrlichia ruminantium in Amblyomma variegatum ticks and small ruminants in The Gambia determined by restriction fragment profile analysis.

Understanding genetic diversity of Ehrlichia ruminantium in host and vector populations is an important prerequisite to controlling heartwater by vaccination in traditional livestock systems in sub-Saharan Africa. We carried out a study in two phases: (i) evaluating the usefulness of the PCR-RFLP assay based on the map1 coding sequence of E. ruminantium as a discriminatory tool to characterise genetic diversity, (ii) applying the technique to field samples from Amblyomma variegatum ticks and small ruminants to characterise genotypic diversity of the organism in three main agroecological zones of The Gambia, Sudano-Guinean (SG), Western Sudano-Sahelian (WSS) and Eastern Sudano-Sahelian (ESS). Restriction fragment length polymorphisms were observed among different strains of E. ruminantium supporting the usefulness of the PCR-RFLP technique for studying genetic diversity of the organism. Restriction enzyme map1 profile analysis indicated the presence in The Gambia of multiple genotypes (at least 11) of E. ruminantium with sites in the WSS and SG zones showing comparatively high number of diverse genotypes. Profiles similar to the Kerr Seringe genotype (DQ333230) showed the highest distribution frequency, being present at sites in all three agroecological zones, thereby making the strain a suitable candidate for further characterisation in cross-protection studies. An additional three genotypes showed relatively high distribution frequency and were present in all three zones making them equally important for isolation and subsequent characterisation. The study demonstrated the occurrence of mixed infections with E. ruminantium genotypes in ruminants and ticks.

Immunisation of sheep against heartwater in The Gambia using inactivated and attenuated Ehrlichia ruminantium vaccines.

Heartwater (cowdriosis) is a disease of ruminants caused by a rickettsial pathogen Ehrlichia ruminantium and transmitted by ticks of the genus Amblyomma. The purpose of this work was to evaluate the protective efficacies of inactivated and attenuated vaccines to protect sheep against heartwater in The Gambia. An inactivated vaccine, prepared from E. ruminantium (Gardel stock), and a live attenuated vaccine from E. ruminantium (Senegal stock), were evaluated in two independent on-station trials. A local stock of E. ruminantium (Kerr Seringe) was used as challenge material. Inactivated and live attenuated vaccines provided 43% and 100% protection, respectively, against virulent needle challenge. In a subsequent field trial, the attenuated vaccine protected 75% of sheep against virulent tick challenge, which was fatal for all control sheep. Quantification by real-time PCR showed that an immunising dose of approximately 23,000 attenuated E. ruminantium organisms was sufficient. Moreover, restriction fragment length polymorphism (RFLP) analysis indicated that the local Kerr Seringe genotype caused mortality amongst control sheep, whereas fatalities in the vaccinated group could be attributed to a different genotype.

Point seroprevalence survey of Ehrlichia ruminantium infection in small ruminants in The Gambia.

Using the MAP1-B enzyme-linked immunosorbent assay, we tested 1,318 serum samples collected from sheep and goats at 28 sites in the five divisions of The Gambia to determine the Ehrlichia ruminantium seroprevalence rates and to assess the risk for heartwater. About half (51.6%) of 639 sheep were positive, with seroprevalence rates per site varying between 6.9% and 100%. The highest seroprevalence was detected in the western part of the country (88.1% in the Western Division and 62.1% in the Lower River Division). Sheep in the two easterly divisions (Central River and Upper River divisions) showed the lowest seroprevalence of 29.3% and 32.4%, respectively, while those in the North Bank Division showed an intermediate prevalence of 40.6%. In goats, less than one-third (30.3%) of 679 animals tested were positive. The highest seroprevalence was detected in goats in the North Bank Division (59%) and Western Division (44.1%). Goats in the Lower River Division showed an intermediate level of 21.9%, whereas the lowest rates were found in the eastern part of the country (4.8% in the Central River Division and 2.3% in the Upper River Division). At nearly all sites, seroprevalence rates were higher in sheep than in goats. The results show a gradient of increasing heartwater risk for susceptible small ruminants from the east to the west of The Gambia. These findings need to be taken into consideration when future livestock-upgrading programs are implemented.