SLA Biomedical & Life Sciences Division Blog

Eggs: Safer for You Than You’d Think Given Recent Stories in the News

They’re recalling  up to 500,000,000 eggs?   Isn’t this an indictment of the U.S. egg industry as a whole?

It might be if that were the total production of the US, but it’s not even close. Last year, according to the U.S. Dept. of Agriculture’s National Agriculture Statistical Service,  the 337, 000,000 laying hens living in the US produced 90,400,000,000 eggs (about 269 eggs per layer, by the way). The recalled number of eggs is less than 1% of the national output, and even among those 500,000,000, it is likely that only a tiny percentage are actually infected. Statistically, the odds are about 1 egg out of 20,000 eggs is infected. ( www.eggsafety.org )

I hear that thousands of people have been made ill from these eggs: what are my chances that I will get salmonella from eating eggs?

As a rule, you are right in thinking that it is possible to get salmonella from eating undercooked eggs, and this is unfortunately one of the most common ways to get salmonella. However the odds are vastly on your  side as opposed to being on salmonella’s. In a 2008 paper (Davis et al, cited below) the odds were given as 1 or 2 people out of 100,000 will get salmonella from undercooked eggs.) This seems a tad too rare, so let’s  divide up the estimated 2010 population of the U.S., 308,000,000,  by the FDA’s estimate that there are 142,000 cases  annually of salmonella caused by eating undercooked  eggs.   This gives you a 1 in 2168  chance of getting undercooked-egg-induced salmonella. That’s cases of illness, not fatalities. Out of this small number, your chances of  actually dying admittedly increase if you are elderly, an infant, or immunocompromised, and pasteurized egg products available to foodservice providers are recommended for venues where large numbers of these groups are served. But remember, the odds of becoming ill or dying from salmonella derived from eggs would be  essentially zero if the eggs were cooked thoroughly, by the way.

What causes this contamination?

A strain of bacteria called Salmonella enteritidis.

Where does that bacterium come from?

It can come from soil, water, or feed, but is found today mostly in poultry manure. It appears to have migrated from rats and mice to poultry a few decades ago. Egg producers and government scientists and health officials have since placed a premium on detecting any signs of rodents in egg producing operations, and in eliminating the vermin, but to some extent the bad genie is out of the bottle. Rodent control still limits the chances of new acute outbreaks of subtypes that have yet to infect layers or show up in eggs.

How does the salmonella get into the egg?

Salmonella enteritidis most commonly lives in the reproductive and intestinal tracts of layers . Eggs are made “inside out” in the sense that whatever pathogens live inside the hen can be transmitted to the eggs growing inside her during egg formation and laying.

Are all parts of the egg equally “dangerous.”

As a practical matter, given that eggs come out of the hen from the same place as her manure, the shell is by far, the most likely part to be contaminated, as it traverses this shared route. This is followed at a great statistical distance  by the egg white, which just happens to have naturally produced inhibitors of the further growth of salmonella (Humphrey & Whitehead 1993) and then, accounting for an  even tinier percentage, would be the yolk.

What do egg producers do to make sure the eggs are safe?

First and foremost, eggs and flocks are tested on a regular basis  and layers known to be salmonella carriers are taken out of production, and their eggs stopped from entering the market.  In some cases, the layers will be given antibiotics until the infection clears. (In other cases, the layers will be destroyed outright.) Any eggs from those layers will be discarded, and even when the infection has passed in successfully treated layers,  the eggs will not be put back into the food supply until the eggs themselves have tested free of antibiotics.

The day-to-day processing of eggs also involves a number of important, practical safety steps. All shell  eggs are thoroughly washed to remove fecal traces. New procedures involving ozone (Perry, Rodriguez-Romo & Yousef 2008), and microwaves (Lakins et al 2008) are being developed as boosters in egg contaminant removal.  Eggs are kept constantly chilled, a seemingly simple step that greatly retards the growth of virtually all bacterial pathogens, including salmonella.

The living conditions of the hens are also continuously inspected and cleaned. The chicken feed and water supply are examined. In all cases of conscientious egg production, the goal is to get the fecal matter away  from the birds and the newly laid eggs as often as possible.

I hear that many US Producers do not vaccinate their hens, while this is done routinely in other countries.  What gives?

A New York Times story headlined “U.S. Rejected Hen Vaccine Despite British Success,” and reported by William Neuman on August 25, 2010, called into question the fact that many U.S. egg producers do not vaccinate their hens in the same way that British egg producers did, virtually eliminating egg-associated salmonella cases over there. But a more careful reading of the story also indicated that the FDA had considered it, but decided that the evidence was not so clear cut as to mandate it nationally. (It’s important to note that the Brits still find salmonella within their hen houses and on the grounds of their farms, and even in some chickens and eggs, and about 500 cases of egg-associated salmonella in humans still crop up annually, although that number   represents a dramatic drop off .) The FDA had  already mandated a number of enhanced hygiene practices on July 9, 2010,  for the egg industry before the outbreak, so it is not as if, the agency has been asleep at the switch. The FDA and the industry’s leading trade organization, the United Egg Producers,  have been partners in safety for decades, according to the FDA’s own  pronouncements.  A recent review of Britain’s success (Snow et al. 2010) cited vaccination as one of the likely reasons, but it also cited washing and disinfecting the hen house, providing cleansing pools of disinfectant  and scrub brushes so that workers could  remove poultry manure from their shoes and boots, using a commercial chicken feed supplier as opposed to a home-grown mixture , and the presence of cats and dogs  to keep the rodent population down as other contributors. While it is not clear whether or not the much larger US egg production facilities use cats and dogs to hunt rodents on site, measure like these are already standard here.

US egg-producing facilities are gigantic and involve caged-birds, and operations like this are banned in Europe,  including within the UK. Will freeing the layers free us from salmonella in their eggs?

According to an  August 25, 2010 column by Angela Wu  in Newsweek entitled “Are Free-Range Eggs Safer: Factory farming has its problems, but evidence is unclear about whether local food is better,”  the story is complicated and the evidence contradictory.  The problem is that the FDA has found salmonella outbreaks at the largest factory farms and at some of the smallest free-range operations, as well as in those mid-sized operations in between. Two pieces of evidence will surprise the back-to-nature enthusiasts: In large caged bird operations, by their very design, manure removal is done more often and much more efficiently: the birds don’t get to soil themselves or the eggs to the same degree. Second, free-range, “pastured” poultry actually has a higher rate of parasitic infections,  so one might wish not to trade the devil you know (salmonella) for the devil you don’t.

Should I give up eating eggs until this is all over?

If you did, you would be giving up one of the most economical, nutritious, and still generally very safe sources of protein, vitamins, minerals, and nutraceuticals. Much wiser might be following the recommendations of a paper by Davis et al 2008, in which they compare common means of cooking eggs at home  in terms of their ability to kill off salmonella (which, ironically because they could not find enough naturally infected eggs, with which to conduct this experiment, they had to go out and artificially infect them). They concluded that hard-boiled, soft-boiled, and eggs poached in dimpled pan suspended over the boiling water and/or steam were safest. Over-easy and scrambled eggs were reasonably safe, with longer cooking times adding to the margin of safety. “Dropped poached eggs,” meaning those let freely slip into simmering boiling or near/boiling water were safe but only if they were immersed for at least  5 minutes. Sunny side eggs, were,  alas, the least safe, although increased cooking time (until the yolk is firmly set) and the use of a pan cover or basting of the yolk with hot cooking oil or grease was thought to be helpful to get the top of the yolk to cook through.

Tony Stankus, FSLA [email protected] Life Sciences Librarian, Science Coordinator & Professor

University of Arkansas Libraries MULN 223 E

365 North McIlroy Avenue

Fayetteville, AR 72701-4002

Voice: 479-575-0966

Fax: 479-409-0021

Almonacid, S., R. Simpson, and A. Teixeira. 2007. Heat transfer models for predicting Salmonella enteritidis in shell eggs through supply chain distribution. Journal of Food Science 72 (9): E508-17.

Davis, A. L., P. A. Curtis, D. E. Conner, S. R. McKee, and L. K. Kerth. 2008. Validation of cooking methods using shell eggs inoculated with Salmonella serotypes enteritidis and Heidelberg. Poultry Science 87 (8): 1637-42.

Gurtler, J. B., and D. E. Conner. 2009. Survival and growth of Salmonella enteritidis in liquid egg products varying by temperature, product composition, and carbon dioxide concentration. Foodborne Pathogens and Disease 6 (5): 561-7.

Humphrey, T.J. & A Whitehead. 1993. Egg age and the growth of Salmonella enteritidis. Epidemiology & Infection. 111: 209-291.

Jones, D. R., and M. T. Musgrove. 2007. Pathogen prevalence and microbial levels associated with restricted shell eggs. Journal of Food Protection 70 (9): 2004-7.

Kretzschmar-Mccluskey, V., P. A. Curtis, K. E. Anderson, L. K. Kerth, and W. D. Berry. 2008. Influence of hen age and molting treatments on shell egg exterior, interior, and contents microflora and Salmonella prevalence during a second production cycle. Poultry Science 87 (10): 2146-51.

Lakins, D. G., C. Z. Alvarado, L. D. Thompson, M. T. Brashears, J. C. Brooks, and M. M. Brashears. 2008. Reduction of Salmonella enteritidis in shell eggs using directional microwave technology. Poultry Science 87 (5): 985-91.

Little, C. L., J. R. Rhoades, L. Hucklesby, M. Greenwood, S. Surman-Lee, F. J. Bolton, R. Meldrum, et al. 2008. Survey of Salmonella contamination of raw shell eggs used in food service premises in the United Kingdom, 2005 through 2006. Journal of Food Protection 71 (1): 19-26.

Murchie, L., Xia Bin, R. H. Madden, P. Whyte, and L. Kelly. 2008. Qualitative exposure assessment for Salmonella spp. in shell eggs produced on the island of Ireland. International Journal of Food Microbiology 125 (3): 308-19.

Musgrove, M. T., J. K. Northcutt, D. R. Jones, N. A. Cox, and M. A. Harrison. 2008. Enterobacteriaceae and related organisms isolated from shell eggs collected during commercial processing. Poultry Science 87 (6): 1211-8.

Perry, J. J., L. Rodriguez-Romo, and A. E. Yousef. 2008. Inactivation of Salmonella enterica serovar enteritidis in shell eggs by sequential application of heat and ozone. Letters in Applied Microbiology 46 (6): 620-5.

Roberts-Witteveen, A., B. A. Campbell, T. D. Merritt, P. D. Massey, C. T. Shadbolt, and D. N. Durrheim. 2009. Egg-associated salmonella outbreak in an aged care facility, New South Wales, 2008. Communicable Diseases Intelligence 33 (1): 49-52.

Snow, L.C., R.H. Davies, K.H. Christiansen, J.J. Carrique-Mas, A.J. Cook & S.J. Evans. 2010. Investigation of risk factors for Salmonella on commercial egg-laying farms in Greta Britain, 2004-2005. Veterinary Record 166 (19): 579-586.

Wu, Angela. 2010. Are free-range eggs safer? Newsweek (August 25, 2010). www.newsweek.com/2010/08/25/are-free-range-eggs-safer-.print.html

Octopus Behavior, Intelligence, Learning, Personality, Problem Solving & Consciousness

In a German aquarium this summer, Paul the Octopus, successfully picked the winner of 2010 FIFA World Cup soccer matches being held in South Africa  eight times in a row, including correctly noting an upset win by Serbia over Germany, but then subsequently predicting Germany’s rebound to winning ways until eventually Germany lost to Spain, the ultimate world cup winner, an outcome Paul had also predicted. Click on the following for a picture of Paul and a story entitled “Germany's 'Octopus oracle' keeps perfect record,”  on the official FIFA website.

www.fifa.com/worldcup/news/newsid=1270308/index.html

Paul’s method of prediction was to select a clam from  one of two underwater boxes in one of two adjacent tanks. Each tank was labeled with the national flag of one or the other of opposing soccer teams.  Confounding logic, many German fans felt that the pregame choice by the octopus somehow subsequently caused Germany’s defeat, and monitors of German Internet usage showed heightened activity related to  researching octopus recipes. The Prime Minister of Spain, in response, promised to send his nation’s equivalent of the US Secret Service to guard Paul and keep him from becoming someone’s dinner. The Russians, out of contention for the World Cup early on, demonstrated greater common sense. The state-supported gaming industry offered 100,000 euros for Paul’s services so as to enable them more scientifically to set odds in international sporting contests. The aquarium,  in reaction to all this, announced that Paul would now be going into retirement from sports prognostications, and perhaps would begin a career as a teacher of other young octopuses. This would seem ludicrous, excepting that there have been some papers, in journals as prestigious as Nature,  that indicated that octopuses can learn from one another, just by watching the trial and error procedures of one of their kind (Fiorito & Scotto 1992) .  Could a weekly column in Sports Illustrated or pr pre-game appearances on ESPN be in the works?  Or perhaps has Paul the Octopus all his hands full already.

How Smart Are Octopuses?

There is a general consensus that octopuses are the smartest of invertebrates, and indeed, they may be smarter than many vertebrates. They can negotiate mazes, and retain a memory of successful vs. blocked pathways (Hvorecny et al 2007). The can learn the location of a suitable hideaway in an experimental tank, be  transferred from the tank to another for a week, and then instantly find the hideaway in the original tank when they are returned to it.  Should this hideaway be closed to them, the octopuses  can then be taught a new hideaway’s location, and retain a subsequent memory of it (Boal et al. 2000).

Octopuses have definite favorites in the types of clams or mussels they eat, but it is conditional, with the principal determinant being the degree of difficulty in getting the shell opened or otherwise penetrated (Anderson & Mather 2007).  In a three way choice, the easiest to open bivalves were consistently the most eaten, the next easiest to open were second, and the most difficult to open were last. However, food preferences for these same octopuses flipped when all three bivalves were presented in equal numbers in an already-opened state. One of the more difficult-to-open species became the new favorite. However, when ordinarily easy-to-open clams or mussels are glued and wired shut experimentally, octopuses once again shift their preferences in order to minimize effort. What’s important is that they appear to generalize from initial trials in each round of changed circumstances. When they encounter types that they find that are hard to open in a particular round, they avoid them subsequently during that round, saving their energy by redirecting their foraging to easier types.

To bolster the argument for octopuses making conscious adjustments and generalizing knowledge from specific examples, it was found that octopuses switched strategies for getting at the actual meat in a clam or mussel: sometimes pulling the shell apart, sometimes smashing the shell, sometimes drilling through the shell and at other times chipping away at the shell’s rim. All of these represented shifts in tactics to difficulties encountered.  When one method did not work for a particular species of clam  or mussel, another method might be tried, and once one method proved to be the right tactic for a particular species, that  method of penetration became associated with that species. Indeed, in a final grace note to the argument, octopuses apparently learned to target where to drill their holes so as to get to the most vital internal organs of the clam or mussel most directly, so that their  subsequent injection of poison would cause the shellfish to open up most quickly.

Can Octopuses Use Tools?

One popular video currently making the rounds  on YouTube, entitled “Coconut-Carrying Octopus” www.youtube.com/watch?v=1DoWdHOtlrk and backed by a scientific article in Current Biology  (Finn, Tregenza & Norman 2009) shows that octopuses “claim” coconut shells that have been split apart as part of copra processing and been cast into the sea. They have developed a way of stilt walking across the ocean floor with the shell hanging beneath them, so as to transport the half-shells rather long distances to a preferred site, and then fashioned them into rather safe shelters. 

Some critics have argued that the use of “found objects” like these shells is not the same as fashioning them into tools, but they have yet to explain away the peculiar habit of octopuses for quite literally playing with Lego toys in aquaria (Kuba et al. 2006) . These toys are in no way food-like objects, nor do they represent  prey or serve as practice dummies for hunting. In fact, they resemble nothing in their natural environment, and yet, they become objects of continuing interest in both adult and juvenile octopuses. Octopuses have even  learned on their own, how to unscrew jars and bottles.

“Hand-Eye”  Coordination & Specialization within the Octopus Brain

One of the relatively recent findings in studies of octopus capabilities is the fact that although they do not have specialized tentacles like squid for trapping prey, they do develop special abilities within their otherwise anatomically identical legs or arms, and that this seems to be done in conjunction with having a favored eye they use for specific tasks. In a series of papers (Byrne, Kuba & Meisel 2004, Byrne et al 2006a, 2006b) it was clearly shown that octopuses have a preferred eye that they use more often than its opposite counterpart, and this seems to correlate with tasks routinely assigned to a given arm or set of arms. Anterior arms were used to probe and reach out for novel objects. Octopuses also seemed to favor a particular arm when trying to negotiate a maze. Moreover some octopuses used different legs or arms for sidewise motion, versus back and forwards, despite the fact that it would take little energy to rotate their bodies and choose a different sequence. This all points to an eye-to-brain-to-arm (or leg) circuitry that indicates that the octopus is capable of designating particular parts of their very large brains to serve differentially, specific functions, much as mammals do.

Do Octopuses Have Distinct Personalities Or Temperaments?

There have been many proponents of the theory that individual octopuses do, in fact, have different personalities. The most vocal in support of this notion are the many aquarium personnel who have observed that some octopuses of the same species are aggressive and easy to anger, while others are shy and gentle. Some are quick learners  who love to play while others are  seemingly annoyed by changes in routine and defensive about new objects in their watery domains. Some come out from hiding in their aquarium tanks to look right back at the people who are looking at them. Some get along with other octopuses in large tanks while others view  others of their kind as intruders that have to be put in their place.  Most remarkable are octopuses who habitually break out of their own tanks, traverse the floor to another tank they have been eyeing, enter that tank, and consume all the crabs or clams to be had there, before moving on to another tank or returning to their assigned one.

By far, the most heavily published of experts in areas of octopus intelligence, behavior and temperament is the Canadian researcher Jennifer Mather of the University of Lethbridge, in Alberta,  ironically  a  province that does not even have access to an ocean (She has repeatedly acknowledged the generous access she has been granted over the years to the Seattle Aquarium). This landlocked academic appointment has not stopped her from making the case rather convincingly that individual octopuses develop their personalities or temperaments over time, that genetically related octopuses tend to have similar behavioral traits, and that  at least some  invertebrates, particularly the category of cephalopods (octopuses, squid and cuttlefish) which have very large brains, use them to explore their environments in a conscious manner,   solving  problems, and building  a memory bank of experiences on which they will depend to improve their lives…….and yes, to have a little fun, now and again.

Tony Stankus, FSLA, [email protected] Life Sciences Librarian, Science Coordinator & Professor

University of Arkansas Libraries MULN 223 E

365 North McIlroy Avenue

Fayetteville, AR 72701-4002 USA

Voice: 479-409-0021

Fax: 479-575-4592

 Anderson, Roland C., and Jennifer A. Mather. 2007. The packaging problem: Bivalve prey selection and prey entry techniques of the Octopus enteroctopus dofleini. Journal of Comparative Psychology 121 (3) (08): 300-5.

Boal, Jean Geary, Andrew W. Dunham, Kevin T. Williams, and Roger T. Hanlon. 2000. Experimental evidence for spatial learning in octopuses (Octopus bimaculoides). Journal of Comparative Psychology 114 (3) (09): 246-52.

Byrne, Ruth A., Michael J. Kuba, and Daniela V. Meisel. 2004. Lateralized eye use in Octopus vulgaris shows antisymmetrical distribution. Animal Behaviour 68 (5) (11): 1107-14.

Byrne, Ruth A., Michael J. Kuba, Daniela V. Meisel, Ulrike Griebel, and Jennifer A. Mather. 2006. Does Octopus vulgaris have preferred arms? Journal of Comparative Psychology 120 (3) (08): 198-204.

Byrne, Ruth A., Michael J. Kuba, Daniela V. Meisel, Ulrike Griebel, and Jennifer A. Mather. 2006. Octopus arm choice is strongly influenced by eye use. Behavioural Brain Research 172 (2) (07): 195-201.

Byrne, Ruth A., Michael Kuba, and Ulrike Griebel. 2002. Lateral asymmetry of eye use in Octopus vulgaris. Animal Behaviour 64 (3) (09): 461-8.

Cheng, Mary W., and Roy L. Caldwell. 2000. Sex identification and mating in the blue-ringed octopus, Hapalochlaena lunulata. Animal Behaviour 60 (1) (07): 27-33.

Edelman, David B., Bernard J. Baars, and Anil K. Seth. 2005. Identifying hallmarks of consciousness in non-mammalian species. Consciousness and Cognition: An International Journal 14 (1) (03): 169-87.

Finn, J.K., T.Tregenza & Mark D. Norman. 2009. Defensive tool-use in a coconut-carrying octopus. Current Biology 19 (23): R1069-R1070.

Fiorito, Graziano; and Pietro Scotto. 1992. Observational learning in Octopus vulgaris. Science. Vol. 256(5056), 545-547.

Glanzman, D.L. Octopus conditioning: A multi-armed approach to the LTP- learning question. Current Biology 18 (2): R527-R530.

Gosling, Samuel D., and Oliver P. John. 1999. Personality dimensions in nonhuman animals: A cross-species review. Current Directions in Psychological Science 8 (3) (06): 69-75.

Hochner, Binyamin, Euan R. Brown, Marina Langella, Tal Shomrat, and Graziano Fiorito. 2003. A learning and memory area in the octopus brain manifests a vertebrate- like long-term potentiation. Journal of Neurophysiology 90 (5) (11): 3547-54.

Huffard, Christine L., Roy L. Caldwell, and Farnis Boneka. 2010. Male-male and male-female aggression may influence mating associations in wild octopuses (Abdopus aculeatus). Journal of Comparative Psychology 124 (1) (02): 38-46.

Hvorecny, Lauren M., Jessica L. Grudowski, Carrie J. Blakeslee, Tiffany L. Simmons, Paula R. Roy, Jennifer A. Brooks, Rachel M. Hanner, et al. 2007. Octopuses (Octopus bimaculoides) and cuttlefishes (Sepia pharaonis, S. officinalis) can conditionally discriminate. Animal Cognition 10 (4) (10): 449-59.

Ikeda, Yuzuru. 2009. A perspective on the study of cognition and sociality of cephalopod mollusks, a group of intelligent marine invertebrates. Japanese Psychological Research 51 (3) (09): 146-53.

Kuba, Michael J., Ruth A. Byrne, Daniela V. Meisel, and Jennifer A. Mather. 2006. When do octopuses play? Effects of repeated testing, object type, age, and food deprivation on object play in Octopus vulgaris. Journal of Comparative Psychology 120 (3) (08): 184-90.

Mather, Jennifer A. 2008. Cephalopod consciousness: Behavioural evidence. Consciousness and Cognition: An International Journal 17 (1) (03): 37-48.

Mather, Jennifer . 2006. Behaviour development: A cephalopod perspective. International Journal of Comparative Psychology 19 (1): 98-115.

Mather, Jennifer A., and Roland C. Anderson. 1999. Exploration, play, and habituation in octopuses (Octopus dofleini). Journal of Comparative Psychology 113 (3) (9): 333-8.

Mather, Jennifer A., and Roland C. Anderson. 1993. Personalities of octopuses (Octopus rubescens). Journal of Comparative Psychology 107 (3) (09): 336-40.

Mather, Jennifer A. 2008. To boldly go where no mollusk has gone before: Personality, play, thinking, and consciousness in cephalopods. American Malacological Bulletin 24 (1/2): 51-58.

Meisel, Daniela V., Ruth A. Byrne, Michael Kuba, Jennifer Mather, Werner Ploberger, and Erhard Reschenhofer. 2006. Contrasting activity patterns of two related octopus species, Octopus macropus and Octopus vulgaris. Journal of Comparative Psychology 120 (3) (08): 191-7.

Minakata, H., S. Shigeno, N. Kano, S. Haraguchi, T. Osugi, and K. Tsutsui. 2009. Octopus gonadotrophin-releasing hormone: A multifunctional peptide in the endocrine and nervous systems of the cephalopod. Journal of Neuroendocrinology 21 (4) (04): 322-6.

Shomrat, T. I. Zarrella, G. Fiorito, & B. Hochner. 2008. The octopus vertical lobe modulates short-term learning rate and uses LTP to acquire long-term memory. Current Biology 18 (5): 337-342.

Sinn, David L., Nancy A. Perrin, Jennifer A. Mather, and Roland C. Anderson. 2001. Early temperamental traits in an octopus (Octopus bimaculoides). Journal of Comparative Psychology 115 (4) (12): 351-64.

Wood, James B., and Roland C. Anderson. 2004. Interspecific evaluation of octopus escape behavior. Journal of Applied Animal Welfare Science 7 (2): 95-106.