Emmanuel Okello

Dr. Emmanuel Okello

University of California Davis
orcid

Research Focus & Metrics

Academic Career Length

13Years (2014-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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4 March 2021 in Animals
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Journal Article
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Lawrence OpioLawrence Opio
Lawrence Opio
Essam AbdelfattahEssam Abdelfattah
Essam Abdelfattah
JTJoshua Terry
Joshua Terry
SOSteven Odongo
Steven Odongo
EOEmmanuel Okello
Emmanuel Okello
Fascioliasis (liver fluke infestation) is one of the most important parasitic diseases affecting cattle, other ruminant animals and humans. Fascioliasis causes large, but usually neglected, economic losses to cattle farmers and traders. The objectives of this study were to assess the prevalence and associated risks for fascioliasis in slaughter cattle and estimate the financial losses due to liver condemnation at the Lira Municipal abattoir in Uganda. A total of 216 cattle were sampled during the study period. Animal breed and sex were determined by observing the phenotypic characteristics of the animals. Age was determined by assessing the eruption and wearing of permanent teeth. After slaughter, the liver was examined for presence of Fasciola spp. (liver flukes) by visual inspection, palpation, and incisions. The bile ducts and gall bladder were similarly examined for presence of mature Fasciola spp. The gross weight and amount of liver trimmed-off due to fluke infestation were determined. Of the 216 liver examined, 65.7% (n = 142) were infested with Fasciola spp. Cattle that were aged 4–5 years old at the time of slaughter had significantly greater odds (OR = 5.84; CI [2.79–12.22]) of being infested with Fasciola spp. compared to those that were younger than 3.5 years old. In contrast, cattle that had a body condition score of 3.5 or 4 had lower odds (OR= 0.42; CI [0.21–0.88] and OR = 0.22; CI [0.04–1.10]) of fascioliasis than those with a BCS of 3. Other tested variables including animal origin, breed, sex, and gross weight of the liver had no significant effect on the prevalence of fascioliasis. This study also revealed that the abattoir loses an estimated 38 million UGX annually due to condemnation of Fasciola-infested liver (one UGX= 0.00027 USD; July 2016). Our study showed that the prevalence of fascioliasis was high in Lira District, Uganda, which results in a large amount of liver being condemned and destroyed, leading to financial losses for affected farmers in the area. Therefore, there is a need to take the necessary preventive measures to control the disease and increase awareness among farmers and medical personnel in the area due to the zoonotic nature of fascioliasis.

6 May 2019 in PeerJ
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SJStephen N. Jenkins
Stephen N. Jenkins
EOEmmanuel Okello
Emmanuel Okello
PRPaul V. Rossitto
Paul V. Rossitto
TLTerry W. Lehenbauer
Terry W. Lehenbauer
JCJohn Champagne
John Champagne
Sharif S. AlySharif S. Aly
Sharif S. Aly
Background: Coagulase negativeStaphylococcus(CNS) species are currently the most prevalent intra-mammary pathogens causing subclinical mastitis and occasional clinical mastitis or persistent infection in lactating dairy cattle. More than 10 CNS species have been identified, but they are generally managed as one group on most dairies in the United States. However, improved management decisions and treatment outcomes may be achieved with better understanding of the prevalent species, pathogenicity and strain diversity within and across dairies.Methodology: A total of 604 CNS isolates were cultured from milk samples collected during a dry-cow treatment clinical trial conducted on 6 dairy herds in 4 states in the US. All the study cows were randomized to receive 1 of the 3 different intra-mammary antimicrobial infusions (Quatermaster, Spectramast DC or ToMorrow Dry Cow) at dry-off. Milk samples were collected at dry-off, calving (0–6 days in milk, DIM), post-calving (7–13 DIM) and at mastitis events within the first 100 DIM. The CNS isolates were identified to species level by partial sequencing of therpoβgene, and genetic relatedness within species was investigated by phylogenetic analysis of the pulse-field gel electrophoresis profiles of the isolates.Results: The major CNS species identified wereS. chromogenes(48.3%),S. haemolyticus(17.9%),S. simulansandS. epidermidis(each at 6.5%). Other CNS species identified at lower frequencies includedS. hominis,S. auricularis,S. sciuri,S. sppKS-SP,S. capitis,S. cohnii,S. warneri,S. pasteuri, S. xylosus, S. hyicus, S. equorum, S. microti, S. rostri, S. gallinarum, S. saprophyticusandS. succinus. Phylogenetic analyses of the major species types demonstrated an association between genetic relatedness and epidemiological distributions ofS. chromogenes, S. simulans, S. haemolyticusandS. auricularis.Additionally, identical strains ofS. chromogenesandS. simulanswere isolated from the same udder quarter of several cows at consecutive sample stages. The rest of the minor species had no deducible genetic-epidemiological link.Discussion: The observed association between genetic and epidemiological distributions indicated animal-adapted nature of four CNS species, suggesting possible host-adapted and environmental transmission of these species. Multi-stage isolation of the same udder quarter strain was evidence for chronic intra-mammary infection.Conclusion: The different CNS species and strains circulating on US dairy herds were genetically diverse. Four species identified were likely udder-adapted pathogens, 2 of which caused persistent infection. Our findings are important in guiding the design of effective mastitis control strategies.

19 September 2023 in Pathogens
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HOHedmon Okella
Hedmon Okella
KTKaren H Tonooka
Karen H Tonooka
EOEmmanuel Okello
Emmanuel Okello
Early detection of Mycoplasmal mastitis is greatly hampered by late seroconversion, slow growth of Mycoplasma organisms, intermittent shedding, and the high cost of diagnostic tests. To improve future diagnostic development, examining the available techniques is necessary. Accordingly, the present study systematically reviewed M. bovis diagnostic studies published between January 2000 and April 2023 utilizing the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) protocol. The protocol registration was performed according to the Open Science Framework (osf.io/ug79h), and the electronic search was conducted in the World Catalog, Mendeley, ProQuest, ScienceDirect, Semantic Scholar, PubMed, Google Scholar, Prime Scholar, and PubMed Central databases using a Boolean operator and inclusion and exclusion criteria. Of the 1194 pieces of literature retrieved, 67 studies were included. Four broad categories of up to 16 diagnostic approaches were reported: microbial culture, serological, DNA-based, and mass spectrometry. Overall, DNA-based techniques were the most published (48.0%), with recombinase polymerase amplification (RPA) and loop-mediated isothermal amplification (LAMP) as the most promising user-friendly, equipment-free techniques. On the other hand, mass spectrometry was reported as the least utilized (2.9%) given the high equipment cost. Though costly and laboratory-allied, DNA-based techniques, particularly PCRs, were reported as the most rapid and specific approach.

12 February 2024 in Foods
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ENEsther Nwanna
Esther Nwanna
RORoseline Ojo
Roseline Ojo
Nusrat ShafiqNusrat Shafiq
Nusrat Shafiq
Awais ALiAwais ALi
Awais ALi
EOEmmanuel Okello
Emmanuel Okello
GOGaniyu Oboh
Ganiyu Oboh
Introduction: Africa faces immense food and health insecurity challenges, a problem partly attributed to food loss and waste during postharvest handling and distribution. In the context of research to meet the sustainable development goals, this project specifically addressed the postharvest loss of the ripe indigenous eggplant (Solanum anguivi lam) fruit called “Igba Yinrin” by Yoruba in South-West Nigeria, which is usually discarded in farms. The study was carried out on ripe and unripe fruits to better understand their value by comparing their effects in diabetes treatment. Methods: The study sought to assess the effects of a diet including ripe or unripe mature eggplant fruits in the sucrose-induced diabetic-like fruit fly. Bioactive compounds were identified and quantified with HPLC–UV, while the antioxidant vitamin (A, C, E), carotenoid, and mineral (Na, K, Ca, Mg, Fe, P, and Zn) content was analyzed in the fruits. Extracts were used to investigate their in vitro anti-inflammatory properties on cyclooxygenases (COX 1 and 2), 5-lipoxygenase (5-LOX), and anti-diabetes enzymes [α-amylase and α-glucosidase], while extract-supplemented diets (0.25–1% concentration) were fed to the fruit flies for 14 days. Results: Interestingly, the results showed that the ripe fruits had a significantly (p < 0.05) higher total phenol and flavonoid content, as well as a higher content of vitamins, carotenoids, and minerals, than the unripe fruits. The in vivo activities of antioxidant enzymes [superoxide dismutase (SOD), catalase (CAT), and glutathione transferase (GST)] and the total thiol level increased, while the blood glucose, reactive oxygen species (ROS), and malondialdehyde (MDA) levels decreased in Drosophila melanogaster (fruit fly). An in silico docking analysis showed strong binding affinity of the above-mentioned enzymes under investigation with the ligands hesperidin, naringin, and myricetin, which are bioactive compounds contained in the examined extracts. Conclusions: There was no significant difference in the biological effects of the ripe and unripe fruit extracts on inflammatory and anti-diabetes enzyme activities, which means that the ripe fruit, usually discarded, could serve as a sustainable alternative source of food nutrients.

21 March 2019 in PeerJ
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RPRichard V Pereira
Richard V Pereira
DWDeniece R Williams
Deniece R Williams
PRPaul Rossitto
Paul Rossitto
JAJohn Adaska
John Adaska
EOEmmanuel Okello
Emmanuel Okello
Sharif S. AlySharif S. Aly
Sharif S. Aly
Background: In this study cull dairy cows from six California dairy herds were sampled seasonally over the course of a year. The objectives were to determine the prevalence of antimicrobial resistant (AMR) Salmonella spp. shed in cull cow feces, and the factors associated with fecal shedding of AMR and multidrug resistant (MDR) Salmonella. Methods: Six dairy farms located in the San Joaquin Valley of California were identified and enrolled as a convenience sample. On each dairy, and once during each of the four seasons, 10 cull cows were randomly selected for fecal sampling on the day of their removal from the herd. In addition, study personnel completed a survey based on responses of the herd manager to questions related to the previous 4 month’s herd management and the specific cattle sampled. Fecal samples were submitted to the California Animal Health and Food Safety laboratory for Salmonella isolation. Antimicrobial resistance was evaluated using broth microdilution method and a gram-negative assay plate following Clinical Laboratory Standards Institute (CLSI) guidelines and breakpoint references. All statistical models were survey adjusted for number of animals on sampling day. Results: A total of 62 Salmonella were isolated from 60 of the 239 fecal samples collected. For 12% (95% confidence interval (CI) [3–20]) of fecal samples a multidrug resistant Salmonella was isolated. The survey-weighted results for the two most common drug classes for which isolates were resistant were tetracycline (39%; 95% CI [27–51]) and ampicillin (18%; 95% CI [9–27]). An important finding was the identification of cephalosporin as the third most common drug class for which isolates were resistant, with ceftriaxone (10%; 95% CI [2–17]) being the most common drug associated with resistance in that class. At the cow-level, reason for culling, prior treatment with antimicrobial drugs as the reason for culling was associated with higher odds of isolating an AMR Salmonella isolate. At the herd-level, percent of animals monthly culled on the farm as well as number of milking cows in the herd were associated with isolation of antimicrobial resistant Salmonella in cull cows. Discussion: Salmonella isolated from fecal samples from cull cows were resistant to important antimicrobials, such as ceftriaxone. The most common drug classes for which isolates were resistant were tetracyclines and beta-lactams, with ampicillin, ceftriaxone and ceftiofur being the three most common drugs within the latter. Cow and herd level factors were associated with isolating antimicrobial resistant Salmonella that should be further investigated for their potential role in promoting occurrence of AMR Salmonella. Our results also highlight the importance of monitoring dairy cattle sent to slaughter for shedding of Salmonella resistant to medically important antimicrobial drugs.

24 February 2015 in Veterinary Research
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KMKristof Moonens
Kristof Moonens
IBImke Van Den Broeck
Imke Van Den Broeck
EOEmmanuel Okello
Emmanuel Okello
EPEls Pardon
Els Pardon
MKMaia De Kerpel
Maia De Kerpel
HGHenri De Greve
Henri De Greve
Enterotoxigenic Escherichia coli that cause neonatal and post-weaning diarrhea in piglets express F4 fimbriae to mediate attachment towards host receptors. Recently we described how llama single domain antibodies (VHHs) fused to IgA, produced in Arabidopsis thaliana seeds and fed to piglets resulted in a progressive decline in shedding of F4 positive ETEC bacteria. Here we present the structures of these inhibiting VHHs in complex with the major adhesive subunit FaeG. A conserved surface, distant from the lactose binding pocket, is targeted by these VHHs, highlighting the possibility of targeting epitopes on single-domain adhesins that are non-involved in receptor binding.