Data collection, analysis and development of a peri-harvest quantitative microbial risk assessment (QMRA) for Shiga toxin-producing Escherichia coli (STEC) in beef production

Doctor of PhilosophyDepartment of Diagnostic Medicine/PathobiologyMichael W. SandersonShiga-toxin-producing Escherichia coli (STEC), of which enterohemorrhagic E. coli (EHEC) are a pathogenic sub-group, are foodborne pathogens of significant public health importance in the United States. STEC belong to the family Enterobacteriaceae commonly found in the large intestine of humans and other warm-blooded animals. EHEC harbors shiga toxin (stx1 and/or stx2) and eae genes which confers the ability to cause human illnesses. The U.S. Department of Agriculture Food Safety and Inspection Service declared seven STEC (O26, O45, O103, O111, O121, O145, and O157) as adulterants in ground beef and non-intact beef products to reduce/eliminate the burden of the pathogens in the beef production chain. STEC control efforts in the U.S. include the development of quantitative microbial risk assessment (QMRA) to identify mitigation strategies that are effective and economical in reducing exposure and reduce occurrence and public health risk from STEC in the beef chain. Collection of accurate and unbiased data is critical for the development of a QMRA that is valid for decision making. Determining the prevalence and concentration of the seven STEC in the different cattle types and seasons is valuable for the development a valid QMRA for STEC in beef production in the U.S. Our systematic review and meta-analysis study of the prevalence and concentration of E. coli O157 along the beef production chain indicated differences in the fecal prevalence of E. coli O157 among cattle types and seasons, revealed decreasing prevalence and concentration of E. coli O157 on cattle hides and carcass surfaces from pre-evisceration to the final chilled carcass stage, and identified study setting, detection method, hide or carcass swab area, and study design as significant sources of heterogeneity among studies reporting prevalence of E. coli O157 along the beef production chain. Bayesian estimation of the diagnostic performance of three laboratory methods (culture, conventional PCR [cPCR], and multiplex quantitative PCR [mqPCR]) used for the detection of the seven STEC in the feces of cattle is necessary to estimate true prevalence of EHEC in cattle. The analysis revealed highest sensitivity of mqPCR, followed by cPCR, and culture for the detection of E. coli O157; the cPCR and mqPCR had comparable specificity, but specificity of mqPCR method was heavily dependent on prior specification. The mqPCR method was the most sensitive for the detection O26, O45, and O103 serogroups. The cPCR method was more sensitive than the culture method for serogroups O26, and O121, but comparable for serogroups O45, O103, O111, and O145. The cPCR method showed higher specificity than mqPCR within serogroups O45, O121, and O145 but no apparent differences within serogroups O26, O103, and O111. A second order quantitative microbial risk assessment was developed to quantify the prevalence and concentration of the seven STEC on pre-evisceration beef carcasses and evaluate the impact of peri-harvest interventions. Simulation scenarios of current industry peri-harvest intervention practices showed variable effectiveness in reducing STEC contamination on pre-evisceration beef carcass, however, a scenario of increased adoption of peri-harvest interventions was more effective at reducing STEC contamination. Fecal-to-hide transfer and hide-to-carcass transfer had a large effect on prevalence and concentration of STEC on pre-evisceration carcasses

Prevalence and risk factors for zoonotic helminth infection among humans and animals - Jos, Nigeria, 2005-2009

Background: Zoonotic infections are among the most common on earth and are responsible for over 60% of human infectious diseases, some of which are caused by helminth parasites. Infection may result from ingestion of infective stage of worms with food, contaminated soil; skin penetration or direct animal contact. This study estimates the prevalence of zoonotic helminth infections (ZHI) among animals and humans in Jos and identifies associated risk factors. Methods: We reviewed laboratory records from five hospitals, one veterinary clinic and meat inspection record at abattoir in Jos from 2005 - 2009. Prevalence was defined as the observed frequency of cases of zoonotic helminth in the sampled population within the study period. Odd ratio analysis was used to identify factors associated with ZHI. Results: Of 6689 humans tested, 524 (7.8%) were positive. Observed ZHI are: Ascaris species (4.5%), Taeniasis-Cysticercosis (1.5%), Schistosoma species (1.1%), Strongyloidosis (0.09%). Among animals, 3520 (18.1%) of 19508 tested/observed were positive; including Fasciola species (12.7%), Taeniasis-Cysticercosis (5.0%), Strongyloidosis (0.4%), Ascaris species (0.04%). The risk of infection was higher among humans aged 6-19 (OR: 3.2; 95% CI: 2.0-5.2) and 20-60 (OR: 2.3; 95% CI: 1.7-3.9). Peri-urban dwellers are at higher risk (OR: 1.5; 95% CI: 1.3-1.9); and so are farmers. Conclusion: The prevalence of zoonotic helminth infection is high among humans and animals in Jos. Risk of infection are higher among human age 6-60, peri-urban dwellers and farmers. This calls for the formulation of workable collaboration between human and veterinary medical disciplines for better control of zoonotic helminth infections.Pan African Medical Journal 2012; 12:

Effect of intervention on the control of Highly Pathogenic Avian Influenza in Nigeria

Introduction: The advent of HPAI in Nigeria was a traumatic experience for the poultry industry. Wealth and resources were lost to the ravages of the virus. The Government of Nigeria with the support of International donor agencies came up with a policy for the prevention of spread of the disease leading to the eventual control and eradication of the virus in Nigeria. The various measures implemented in the control of the outbreaks, and their effects on eradication of the virus in the country are highlighted. Methods: Using combined data from passive and active surveillance for HPAI in poultry farms, wetlands and live bird markets in Nigeria during 2006 – 2009, with laboratory diagnostic findings, we describe the characteristics of the control strategies implemented. The control measures include immediate reports of suspected outbreaks, prompt laboratory confirmation and rapid modified stamping out with compensations paid to affected farmers. Decontamination of infected farm premises, re-organization of live bird market were carried out, and bio security measures put in place before re-stocking. Results: Three years following initial outbreak, the number of laboratory confirmed cases drastically reduced from 140 in 2006 and 160 in 2007 to only 2 cases of field outbreak in 2008. Only one case of human infection was documented during the period and no field outbreak or detection by surveillance was reported throughout 2009 and 2010. Conclusion: The measures employed by the Government through its agencies in the control of HPAI in Nigeria brought the incidence of the disease to naught.Pan African Medical Journal 2012; 13:1

Features of Highly Pathogenic Avian Influenza (HPAI) H5N1 in Domestic Poultry

H5 and H7 subtypes are associated with the highly pathogenic form of AI (HPAI), which are extremely virulent, causing up to 100% mortality in domestic poultry. This virulence and ability to cause systemic infection have been attributed to the multibasic cleavage motif in their hemagglutinin molecule, which are recognized by subtilisin-like endoproteases that are virtually present in every tissue, making them capable of replicating in multiple tissue; hence, lesions are multisystemic (i.e., nervous, circulatory, respiratory, integumentary, musculoskeletal, hemopoietic, gastrointestinal, reproductive systems). The myriads of lesion that accompanied outbreaks of HPAI in domestic poultry as seen in Nigeria from 2006 to 2016 are as a result of the above findings. A critical look at the Nigerian HPAI situation not only revealed the general clinic-pathologic features in domestic poultry and factors that support the persistence of the virus in the environment but also gave insight to the flow of the virus in the country. A situation whereby poultry are kept in free-range, multispecies, multiage holdings with low biosecurity supports the spread of HPAI. Also, the live bird markets (LBMs) that have been fed by this unorganized poultry structure have consistently been the nidus for HPAI detection, be it in 2008 after the virus was thought to have been eradicated or in 2015, when the virus resurfaced in Lagos. It is proposed that all factors enhancing the propensity of the virus to remain in poultry should be giving the attention required. Therefore, it is important that the strict biosecurity measures that ensure prevention of HPAI incursion into poultry premises after 2008 are revamped while improving on the organization of the poultry and product supply chain in the country