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Rebuttal of the Food Safety News Posting on Salmonellosis

05/31/2018

The May 26th edition of Food Safety News issued by the law firm of Attorney Bill Marler includes a commentary by Roy Costa.  A practicing sanitarian and professional expert witness, Costa is apparently out of his depth in commenting on the epidemiology of foodborne Salmonella infections. The topic is a lot more intellectually challenging than counting cockroaches and rodent droppings under the sinks of restaurants. His article denotes a non-objective bias against commercial egg production exemplified by his opening sentence, “The disgusting truth about industrial egg production is it stinks”.

 

The article contains numerous inaccuracies and misconceptions in relation to the recent case of Salmonella Braenderup infection among consumers involving 35 diagnosed cases over a three month period. The cluster of cases has been attributed by the FDA correctly or otherwise to a North Carolina complex holding three million hens. 

 

Costa should differentiate between vertically transmitted egg-borne infections such as SE and non-group D Salmonella serotypes which have an entirely different epidemiology. It is important at the outset to recognize that there is no epidemiologic commonality between the 2010 outbreak of Salmonella Enteritidis (SE) and the 2018 case involving Salmonella Braenderup. In the 2010 SE outbreak approximately 2,000 cases were diagnosed within a two month period and the incidence rate declined precipitously within a week of the mandatory recall. The Iowa flocks in question had at least a five-year history of infection with SE, a Group-D serotype known to be vertically transmitted from the reproductive tract of hens to their eggs.  The outbreak was probably amplified by improper handling of product including failure to maintain storage temperatures below 45F. A second possible contributory factor was extended storage suggested by evidence of illegal misstatement of use-by dates for both packed product and graded-egg and nest-run sales.  A combination of prolonged storage and thermal abuse will increase the quantum of infection transmitted vertically from the hen to the consumer. A proportion of eggs may have only 102 CFU per egg at the time of lay but proliferating to 108 CFU within ten days under suboptimal conditions of storage.

 

In the case of the Salmonella Braenderup trace-back study, there is some question as to the source of the pathogen among specific cases which were apparently related by whole genome sequence assays performed by the Food and Drug Administration.  Given the initial laboratory findings by the FDA, and a site visit by FDA inspectors, the company concerned elected to withdraw shell eggs from the market, initially dumping 2.4 million eggs each day in landfills. It is understood that more recently eggs are transported to a USDA-FSIS approved and inspected plant for breaking and pasteurization.

 

Costa apparently believes or implies that Salmonella infection originates from rodents and flies.  This is totally incorrect.  In the case of Salmonella Enteritidis, the infection is vertically transmitted from parent stock to commercial progeny.  Admittedly mice are susceptible to SE and the survivors become carriers and can disseminate SE infection among houses on a complex but they are not intrinsically responsible for introduction of infection.  Mice on a farm with flocks shown to be free of SE will not introduce infection and cannot influence the prevalence rate of the pathogen in eggs irrespective of the level of rodent infestation. If the flock is free of infection neither mice nor flies will have any role in dissemination of SE. In the case of the North Carolina complex the FDA has not released any data relating to the prevalence of Salmonella Braenderup in flocks, environmental samples from houses and the packing plant, presence of the pathogen in reproductive tracts of hens of various ages, egg pools or recovery from rodents, flies or manure or from workers on the farm.

 

Since the late 1990’s, breeder flocks at the Great-grandparent, Grandparent and Parent levels have been free of SE infection with primary breeders and multipliers conforming to the statutory  NPIP Salmonella Enteritidis prevention and detection program. Rarely “breaks” occur but these are detected in parent stock by repetitive and routine environmental drag-swab litter assays usually at three-week intervals preventing delivery of infected chicks. At the commercial level, consignments of day-old pullets are assayed by examination of chick-box papers collected at the time of delivery. 

 

There is little known about the epidemiology of Salmonella Braenderup in livestock and poultry.  This pathogen is not generally regarded as associated with eggs and previous limited outbreaks documented in the literature have been attributed to contaminated meat pies and fresh produce.  While investigations are in progress any comments as to the origin of Salmonella Braenderup and possible dissemination among flocks on the implicated complex are speculative.  It is possible that the infection could have been introduced through contaminated animal by-product meal if this ingredient was in fact incorporated into diets fed to the hens or it the pathogen may have been tracked on to the complex through deficiencies in structural or operational biosecurity involving defective decontamination of personnel, vehicles or equipment.

 

Costa is reminded of the ongoing FDA Final Rule on the Prevention of Salmonella and the numerous state EQAP programs and individual company initiatives to prevent and detect SE involving biosecurity, vaccination and monitoring which have proven to be decidedly effective.

 

There have been no documented cases of egg-borne SE attributed to a farm complying with the FDA program or an industry or state EQAP since the 2010 outbreak.

 

Including the implicated company alleged to be responsible for the 2018 Salmonella Braenderup cases and the extensive SE outbreak in 2010 in the same sentence is a disservice to breeders and commercial egg producers.  The limited outbreak of Salmonella Braenderup does not necessarily indicate a “failure of the food safety system”. In contradistinction the diagnoses among consumers serve as a confirmation of the sensitivity of data-based detection systems introduced by the CDC including FoodNet and PulseNet (now using whole genome sequencing). It is an achievement to detect an outbreak of 53 cases in a multi-state population of 100 million at risk over a period of three months.

 

 It is hoped that if Roy Costa is to serve as an expert witness in any action brought by his Client, Marler Clark, that he should at least become familiar with the epidemiology of vertically transmitted Salmonella Group D serotypes and the obvious distinction in transmission and detection of Group B and C Salmonella serotypes.  It would behoove him before submitting to a deposition to be more familiar with aspects of commercial production, industry standards and preventive practices employed. Above all if he is to serve as an expert in relation to a disease outbreak he should refrain from broad generalizations which demonize an industry and generate concern among consumers. The U.S. egg production industry with 315 million hens is responsible for producing a wholesome, nutritious and inexpensive food product.

 

Food Safety News is generally a factual and informational web-site dealing in food-borne infections, the professional specialty of the Marler Clark Law Firm. As a regular subscriber I am disappointed with the Roy Costa contribution but regard the posting as an aberration from informed editing, representing a descent into ill-informed sensationalism.