Verotoxin producing Escherichia coli (VTEC) has emerged as an important foodbome pathogen since 1982. It causes diarrhoea, haemorrhagic colitis (HC), haemolytic uraemic syndrome (HUS) and thrombotic thrombocytopenic purpura (TTP). Children below 5 years of age and elderly people are more susceptible to this disease than the other age group. Since the emergence of VTEC there have been many illness and outbreaks throughout the world. Most of these outbreaks were associated with consumption of contaminated meat and meat products. The intestinal tract of cattle has been considered as a principal reservoir of this pathogen. Meat and meat products become contaminated during slaughtering and processing. Diseases caused by VTEC impact on the society and the economy. It imposes costs on the society both directly and indirectly. The direct costs result from medical expenses from patient and family, hospital costs, medicine and ambulance
costs, while the indirect costs include productivity loss from the patient and parent or carer. The great concern of VTEC caused disease is due to its higher level of severity in children and elderly people leading to either fatalities or chronic sequelae.
This study undertook a risk assessment of VTEC in Australia by a microbiological study in food, an analysis of potential socio-economic impact of an outbreak by examining the E.coli 1995 outbreak as a proxy and the economic viability of a hazard analysis critical control point (HACCP) based food safety programme.
In order to assess the risk of VTEC in food samples, this study conducted a survey to determine the prevalence of VTEC in Australian food. Twelve hundred samples (liver and heart) were collected from four abattoirs namely Dinmore, Pittsworth, Ipswich and Chinchilla in Southeast Queensland. The samples were processed for isolation and identification of
E.coli and characterised for identification as VTEC.
In order to isolate E.coli, the sample was processed in the laboratory and grown on MacConkey (MCA) agar overnight at 37° C for lactose positive colonies. The lactose positive colony was grown in MacConkey broth purple at 44 - 45° C. The isolated E.coli was then confirmed by indole and oxidase tests. Only nine per cent of the samples were found to be contaminated with E.coli. The isolated E.coli was characterised for biotyping, entrohaemolysin production and antibiotic sensitivity. The isolates were differentiated into five biotypes based on fermentation with carbohydrates and amino acid substrates. Most of the isolates did ferment sorbitol in 24 hours.
The isolate was tested for enterohaemolysin production in washed sheep blood agar. Enterohaemolysin production has been
considered as an epidemiological marker for verotoxin producing E.coli. However in this study none of the isolates produced enterohaemolysin.
The isolates were assessed for antibiotic sensitivity with common antibiotics. The antibiotic resistance pattern of the isolates varied with different antibiotics and between the abattoirs. Highest resistance pattern was observed for chloramphenicol and streptomycin followed by ampicillin and tetracyline. No isolate was resistant gentamicin. Among the isolates only 6 per cent were multiple resistant.
Isolated E.coli was examined for plasmid profile and identification of 60 MDa plasmid. Half of the isolates examined harboured plasmids and in all 32 plasmids profiles with different sizes were observed. However, the isolates did not contain any unique plasmid and most of the isolates lacked 60 MDa plasmid. A positive correlation between antibiotic resistant
isolates and big plasmid were noticed. A low probability of VTEC was observed in the food samples considered in this study.
Despite the low prevalence of VTEC in this study there has been increasing surveillance of VTEC in Australia. In addition, there had been an outbreak in 1995 in South Australia, which was reported to be linked with a meat product. This study estimated the socio-economic costs of the outbreak to oversee the economic loss from any potential outbreak and to emphasis the importance of a control programme.
The 1995 E.coli outbreak affected 200 people and of these 23 children developed HUS leading to death of a child. The cost of illness method (COI) was used to estimate the costs from this outbreak. An estimated $5.61 million loss incurred from this outbreak. Indirect costs contributed 60 per cent of the outbreak costs. A premature death of a 4-year old child alone contributed a major share of the
total costs. Productivity loss from patient and parents also significantly contributed to the costs. Chronic patient illness costs played a great role in direct medical costs.
Australia incurs an economic loss of $2.46 billion annually due to foodbome illnesses. Meat and meat product accounted for 68 per cent of these costs. Considering the socio-economic consequences of foodbome diseases, an efficient control programme was explored. HACCP-based food safety programmes were examined for their economic efficiency. The programme benefits were estimated from costs saving of the diseases and additional costs employing secondary sources. The viability of the programme was examined employing tools for social cost-benefit analysis, including net present value (NPV), internal rate of return (IRR), and benefit-cost ratio (BCR). The important variables relating to HACCP-based food safety programmes, which can influence the benefits, were examined. Input variables like
training, initial investment and project implementation period can change the net benefit of the programme. In most cases the programme appeared to be economically viable.