Category Archives: Some like it hot

Salmonella from frozen dinners!

It’s been a while since I have reviewed the various risks associated with eating, but I came across this Salmonella menace a few weeks ago. The Centers for Disease Control and Prevention published a case study describing a multistate outbreak of Salmonella enterica serotype Chester due to frozen meals. In November the CDC reported that 44 people became ill in 18 states during the late spring of 2010. Molecular analysis of patient isolates indicated sole source contamination and questionnaires completed by the patients suggested that “brand A cheesy chicken and rice frozen meals” were responsible. Of the 43 patients who were followed up, 16 of them required hospitalization however no deaths were reported. On the strength of the epidemiological analysis, the company recalled the product from the shelves and the outbreak strain was identified in 8 unopened containers. Investigation into the source during the manufacturing process did not turn up any production deficiencies or a conclusive common contaminated ingredient supplier.  The best guess was that a single poultry supplier was the source in the outbreak. What made this case novel was that this episode represents the first time that Salmonella enterica serotype Chester had been reported in a widespread foodborne disease outbreak.

Editorial notes by the CDC point out that there is little in the way of negligence in either the supplier or production procedures used to bring this product to market. Simple Google image searching showed that the dinner in the above graphic was the one recalled in this outbreak. The label clearly says “Keep Frozen–Must be cooked thoroughly” and is considered a “not ready to eat” meal, as opposed to the hugely convenient “heat and serve” meal. Organisms such as Salmonella enterica and Shiga toxin-producing Escherichia coli are not effectively killed by incompletely reheating in the microwave, and require actual cooking in order to render them inert. The instruction to “allow dinner to sit in the microwave for 1 minute” is also a critical part of the cooking process, and is frequently ignored by consumers. The CDC notes that this outbreak highlights the need to educate the public on safe food handling procedures, and the need to follow the instructions prior to eating these products. Consumers also, if using a microwave oven to cook these products, need to know the specifications of their appliances and to ensure that their microwave ovens are able to be safely used to cook these.


Fungal pathogens: a new reason to worry

Coccidioides arthrospores

The Centers for Disease Control and Prevention have just published an epidemiological study describing the increasing incidence of coccidioidomycosis (Valley Fever) over a 13 year period in the United States. Most fungal infections of humans are non-contagious, and can be acquired by the accidental inhalation of spores. Infection due to Coccidioides immitis follows this standard route of transmission, and the CDC has charted an almost 10-fold increase in human infections during the period from 1998 to 2011. It is one of the few infections due to a fungal pathogen that is considered a Nationally Notifiable Disease to the CDC.

Coccidioidomycosis in most patients causes mild disease, with self-limiting influenza-like upper respiratory symptoms. Up to 75% of patients do become sick enough to miss work or school, and approximately 40% of diagnosed cases require hospitalization. Most cases resolve well with standard antibiotic therapy directed against fungi, and typically less than 1% of cases result in bloodstream disseminated disease. Disseminated disease is extremely serious, and can have a very poor prognosis. Since the route of infection is via inhalation of spores, coccidioidomycosis is not contagious from person to person; infections occur because of environmental exposure. Universal precautions with patient care are therefore not going to be as serious as for an easily transmissible disease.

Coccidioides immitis is considered an endemic pathogen in the southwest United States, and for cases that occur in Pennsylvania, patients invariably report travel to this region in their recent history. CDC editorial comments suggest that actual rate of infection might be significantly underreported, as many cases might be asymptomatic, and some health jurisdictions do not need to report this disease. The CDC notes that this alert is consequently limited to some extent, due to the problems in consistent reporting across public health districts. Consequently, significant further study is critical to determine how much of the observed increase in Coccidioides infections are artifactual, and to what extent the number of cases are actually increasing. If coccidioidomycosis rates are truly increasing as the epidemiological data suggests, the increase is most likely due to a number of factors: altered rainfall patterns and temperatures in endemic areas might lead to easier dispersal of soil-dwelling spores, as well as increases in the disruption of soil by human activity and construction can also lead to easier spore dispersal. The CDC recommends that better awareness of the risks of coccidioidomycosis in endemic regions on the part of the public and by health-care workers can be important in prompt treatment and management of disease.

Rabbits: perhaps bad after all

DON'T Pat the Bunny!

DON’T Pat the Bunny!

You may recall that there is some controversy as to the extent and nature of the Rabbit Menace. Here is another data point for you to consider, before you head off to PetSmart to get your new companion. Via the journal Global Change Biology, a tale to terrify you.

Many herbivores carry a variety of intestinal helminth parasites, which are acquired during feeding and passed on in the feces. Two soil dwelling helminth parasites of the European rabbit (Oryctolagus cuniculus) have been used to model the interactions between hosts and pathogens in controlled laboratory systems. The nematodes Graphidium strigosum and Trichostrongylus retortaeformis have been extensively studied in the rabbit for decades. Neither nematode typically causes a lethal infection in rabbits, but does lead to weight loss and decrease in fecundity in infected animals. A quick search through Pubmed did not turn up any obvious infections of humans, but presumably the elderly, the very young, and otherwise immunocompromised are at some measure of risk of infection.

CrawlingCelegansThe current study focuses on the ambient temperature, egg hatching rates of the nematode in soil, and survival of the larvae, and came about due to observations of generally increasing air temperature measurements at the study site over a 30 year period. These observations have led the authors to question whether host/parasite dynamics might additionally be affected by environmental conditions. What they found was that T. retortaeformis, but not G. strigosum, showed higher rates of egg hatching and larval survival with increases in temperature. This result contrasted the 30 year period of field studies, which indicated that G. strigosum infection rates increased during the interval of generally increasing ambient temperature trends.

Overall, the study underscores the dynamic nature of the host/parasite interaction, and the potential that shifting environmental conditions enable certain microorganisms to have competitive advantages over others. Although both of these worm pathogens pose no known risk to humans, many other bacterial, fungal, protozoan, and metazoan pathogens of humans may demonstrate similar responses to altered environmental conditions seen, as mean global temperatures continue to increase.

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