Biology subjects

Duodu, S.

Publications and source records attributed to Duodu, S..

3 recordsLinked to original sources

bioRxiv2022

Molecular epidemiology of Infectious Spleen and Kidney Necrosis Virus (ISKNV) in Ghanaian cultured tilapia

1Infectious Spleen and Kidney Necrosis Virus (ISKNV) is increasingly gaining more attention globally, due to its highly significant economic impact on the aquaculture industry. In late 2018, unusually high levels of mortality (60-90%) was reported in some intensive tilapia cage culture systems in Ghana. Preliminary investigations confirmed the involvement of ISKNV, a viral pathogen noted for fatal systemic infections in many fish species. As a follow-up on the outbreak situation, and post-mass vaccination of affected fish farms, the need to investigate further the molecular epidemiology and phylogeography of the virus across Lake Volta became paramount. In this study, a multiplexed PCR assay and MinION nanopore sequencing of the Major Capsid Protein (MCP) were performed to investigate the presence and genotype of ISKNV in tilapia collected from 30 randomly selected farms spread across Lake Volta. Fish with and without clinical signs were included in the molecular detection of the virus from brain, kidney and spleen tissues. ISKNV was detected at 80% prevalence with fry and juvenile fish being most affected. Phylogenetic analysis of the MCP revealed that all 35 isolates from 14 different farms were ISKNV genotype I with near- 100% homology to the 2018 outbreak strain. Vaccination and heat shock treatment; the main specific interventions currently employed to control the viral pathogen have not achieved much success and ISKNV remains a threat to the growth of the aquaculture industry in Ghana. The outcome of this study can be useful in improving fish health management and biosecurity policies in the aquaculture industry.

molecular biology↗

bioRxiv2022

Extraintestinal survival and host immune response to Vibrio cholerae

Vibrio cholerae is best known to cause the deadly disease cholera. However, in recent years this bacterial pathogen has been found to invade intestinal layers and translocate into the bloodstream of humans. The aim of this study was to investigate the molecular basis of V. cholerae bacteremia. Nine (9) strains of V. cholerae; six (6) environmental strains of non-O1/non-O139 serogroup and three (3) clinical strains of O1 serogroup and El-Tor serotype were screened for survival in serum obtained from immunocompromised patients. Serum from immunocompetent individuals with no known underlying conditions were used as healthy controls. Five (5) environmental strains and one (1) clinical strain of V. cholerae were identified to survive the bactericidal action of serum. Whole genome sequence analysis revealed the cholix toxin (ChxA) and genes encoding for siderophores (FepE and EntD) as possible virulence factors used by the environmental strains to cause invasive bloodstream infection. Peripheral blood mononuclear cells (PBMCs) stimulated with V. cholerae revealed increased expression of some cytokines; IL-1{beta} and IL-13 and the chemokine; RANTES especially among diabetics. The present study illustrates the potential survival of V. cholerae in blood, which could be aided by scavenging for iron from their host leading to severe infections.

microbiology↗

bioRxiv2019

First detection of Infectious Spleen and kidney Necrosis Virus (ISKNV) associated with massive mortalities in farmed tilapia in Africa

In late 2018, unusual patterns of very high mortality (>50% production) were reported in intensive tilapia cage culture systems across Lake Volta in Ghana. Samples of fish and fry were collected and analysed from two affected farms between October 2018 and February 2019. Affected fish showed darkening, erratic swimming and abdominal distension with associated ascites. Histopathological observations of tissues taken from moribund fish at different farms revealed lesions indicative of viral infection. These included haematopoietic cell nuclear and cytoplasmic pleomorphism with marginalisation of chromatin and fine granulation. Transmission electron microscopy showed cells contained conspicuous virions with typical Iridovirus morphology i.e. enveloped, with icosahedral and or polyhedral geometries and with a diameter c.160 nm. PCR confirmation and DNA sequencing identified the virions as Infectious Spleen and Kidney Necrosis Virus (ISKNV). Samples of fry and older animals were all strongly positive for the presence of the virus by qPCR. All samples tested negative for TiLV and Nodavirus by qPCR. All samples collected from farms prior to the mortality event were negative for ISKNV. Follow up testing of fish and fry sampled from 5 additional sites in July 2019 showed all farms had fish that were PCR positive for ISKNV, whether there was active disease on the farm or not, demonstrating the disease was endemic to farms all over Lake Volta by that point. The results suggest that ISKNV was the cause of disease on the investigated farms and likely had a primary role in the mortality events. A common observation of coinfections with Streptococcus agalactiae and other tilapia bacterial pathogens further suggests that these may interact to cause severe pathology, particularly in larger fish. Results demonstrate that there are a range of potential threats to the sustainability of tilapia aquaculture that need to be guarded against.

microbiology↗