Archive for August, 2012
Zoos exist to save people money spent travelling to exotic places to see animals in the wild. By bringing a large number of species together in a small space people get a snapshot of the world’s different biomes. Pity the archaeologists of the future digging through the remains of Melbourne, Los Angeles and London, wondering how elephants, tigers and monkeys could have been native to all three cities.
While it’s certainly “nice” to see polar bears in Melbourne, they don’t appreciate the summer heat any more than the gorillas in Toronto enjoy the snow. This mixing and matching produces all sorts of husbandry and dietary problems, which are handled with varying degrees of success. It also creates novel disease issues. This was highlighted recently by the deaths of four polar bears in a German zoo (Greenwood et al 2012). They died of a herpesvirus infection contracted from the zoo’s zebras. The herpesvirus was perfectly well adapted to the zebras and caused them no problems but, when it got into a naïve, non-adapted polar bear, fatal illness was the result.
Herpesviruses seem particularly good at this sort of thing. African elephants carry a herpesvirus that is fatal to Asian elephants. Wildebeest carry a herpesvirus that kills other species of hoofstock. Squirrel monkey herpes kills owl monkeys. A herpesvirus carried by South American conures kills African and Australian parrots. SIV, a relative of HIV (and not a herpesvirus) carried by African monkeys, kills Asian macaques. Normally this would not be a problem as these animals, and their bugs, would not come in contact with each other. However, this mixing of animals from different areas, which gives adapted viruses and bacteria access to non-adapted hosts, is occurring more and more.
Not only is this a problem in zoos but it is happening in the big wide world too. As we clear more and more habitat we come into contact with new species and new disease agents. Feral species, which have made their way into new habitats because of our deliberate or accidental influence, bring their bugs with them too. Species that previously had no connection with each other are suddenly brought into close proximity. Hence, the transmission of Hendra virus from bats to horses, Nipah virus from bats to pigs, toxoplasmosis from feral cats to marsupials and otters, monkeypox from Gambian giant rats and prairie dogs to humans, and chytridiomycosis from African clawed frogs to the amphibians of the world.
At least, when animals are concerned, some of these diseases can be confined to farms or contained by quarantine measures. These are, however, not always as effective as we would like as seen by the introduction of foot and mouth disease to Great Britain, equine influenza to Australia, and psittacine pox to New Zealand. These diseases were eradicated at great expense and effort.
Unfortunately people don’t go through quarantine when they travel, allowing for extremely rapid dissemination of diseases. Just look at how quickly SARS spread from South East Asia in November 2002 to Canada by April 2003. It is estimated that a flu outbreak in the northern hemisphere will reach Australia in four to eight weeks. While we impose travel restrictions on animals to safeguard our pets and agriculture we certainly don’t want to inconvenience ourselves by impeding our own travel, even though the consequences are potentially far more catastrophic. While globalization has facilitated trade, democracy, entertainment, and the dissemination of information, it has also greatly enhanced our ability to spread disease. Unfortunately the science of predicting what the next possible pandemic will be and where it will come from is at a similar stage as the science that predicts earthquakes and volcanic eruptions i.e. we have absolutely no idea. For the moment all we can do is react and hope that will be enough.
And don’t forget to keep washing those hands.
Dr. F. Bunny
Greenwood, A.D., K. Tsangaras, S.Y.W. Ho, C.A. Szentiks, V.M. Nikolin, G. Ma, A. Damiani, M.L. East, A. Lawrenz, H. Hofer, and N. Osterrieder. 2012. A potentially fatal mix of herpes in zoos. Current Biology http://dx.doi.org/10.1016/j.cub.2012.07.035.
Last time I talked about probiotics and their somewhat dubious efficacy claims. Now it’s time to mention prebiotics. For those who were not taking notes or slept through the previous lecture, probiotics supposedly contain “good” bacteria that will help to maintain gut health. Prebiotics, on the other hand, contain no bacteria but various non-digestible carbohydrates, such as lactulose and inulin, that are meant to promote gut health by lowering intestinal pH and selectively stimulating the growth of beneficial bacteria. Many pathogenic bacteria prefer a neutral pH and studies have shown that ingesting lactulose can reduce or eliminate Salmonella from rats and humans (Crittendon 1999). Unfortunately a diet laced with lactulose failed to stop Salmonella shedding in two python species (Holz and Middleton 2005). However, consuming it for six weeks did result in increased faecal bifidobacteria and lactobacilli (“good” bacteria) in humans (Bouhnik et al 2004).
Despite the variable results reported above prebiotics are not necessarily species specific the way probiotics need to be. I suspect the beneficial effects of yoghurt are not because of the bacteria they contain but because they produce an acidic environment more conducive to “good” bacterial growth. The good news is that many of the foods we eat contain prebiotics. High levels can be found in chicory root, dandelion greens, Jerusalem artichokes, garlic, onions and leeks (Moshfegh et al 1999). As usual a balanced and varied diet will provide your body with everything it needs, without resorting to expensive supplements.
Dr. F. Bunny
Bouhnik, Y., A. Attar, F.A. Joly, M. Riottot, F. Dyard, and B. Flourie. 2004. Lactulose ingestion increases faecal bifidobacterial counts: a randomised double-blind study in healthy humans. European Journal of Clinical Nutrition 58: (3) 462-466.
Crittendon, R.G. 1999. Prebiotics. In: Tannock, G.W. (ed.): Probiotics: A Critical Review. Horizon Scientific Press, Wymondham, Norfolk, UK. Pp. 141-156.
Holz, P.H., and D.R. Middleton. 2005. The effect of feeding a prebiotic on Salmonella excretion in carpet pythons, Morelia spilota, and scrub pythons, Morelia amethystina. Journal of Herpetological Medicine and Surgery 15: (1) 4-6.
Moshfegh, A.J., J.E. Friday, J.P. Goldman, and J.K. Chug Ahuja. 1999. Presence of inulin and oligofructose in the diets of Americans. Journal of Nutrition 129: 1407S-1411S.
We share our bodies with 100 trillion bacteria. Not only are these bacteria not harmful to us but they are absolutely essential to our continued health and wellbeing. Our intestines alone contain buckets of these “good” bacteria that help us digest our food, provide additional nutrients and keep out the “bad” bacteria. When things get out of whack because of poor diet, stress, or the improper use of antibiotics the “bad” bacteria gain a foothold and vomiting and diarrhoea result (and possibly wailing and gnashing of teeth). It makes some sense to try and restore the balance by tipping a few zillion “good” bacteria back into the system. This is where probiotics come in, as they are supposed to contain these “good” bacteria. Probiotics have become big business and, as usual where money is involved, the hype outweighs the science.
The theory that “good” bacteria should be used to replace the “bad” bacteria and make us well again is sound. However, this is not what is put into practice. As can be imagined different species have different bacteria in their guts, because they have different diets, consume different food stuffs and, therefore, have different needs. Even within the human species different people have different bacteria as some of us are vegetarian (Prevotella spp. dominate), while others are more carnivorous (Bacteroides spp. dominate) (http://www.nytimes.com/2011/04/21/science/21gut.html?_r=1). Different bugs are needed to deal with these varied diets. What, then, is the logic behind a probiotic such as Protexin Concentrate, which claims to assist digestive function in poultry, pigs, sheep, goats and cattle (http://www.protexin.com/products/protexin-concentrate/13)? Presumably each group of animals contains a whole range of different gut bugs, while this product only contains one specific bacterium: Enterococcus faecium. Human intestines are estimated to contain between 300 and 1000 different bacterial species. Is adding one more bacterium to this broth really going to make a difference?
NutriBAC (http://www.mzrproducts.com/) is a probiotic sold for use in reptiles and amphibians. How one probiotic can satisfy the demands of such a diverse group of animals as frogs, snakes, iguanas and bearded dragons is beyond me. Salmonella is one of the “bad” bacteria reptile keepers worry about. One of the claims made by probiotic manufacturers is that they will stop reptiles shedding Salmonella. A recent study failed to corroborate this assertion (Holz and Middleton 2002).
Probiotics need to be species specific to have any positive effect. One study demonstrated increased resistance to Salmonella colonisation in chickens fed probiotics, but results were better when they were fed actual caecal contents from healthy chickens (Fuller 1999).
Young animals are inoculated with “good” bacteria from their mothers. Orphans that are hand raised may lack these bacteria and often develop diarrhoea. One common method used to counteract this is the shit shake. Faeces are taken from a healthy animal of the same species and mixed in with the animal’s milk. It doesn’t sound particularly attractive but hopefully provides the animal with the bacteria it needs to survive. In fact koalas produce a special type of faeces called pap that is excreted directly from the caecum. Without this pap koala joeys cannot digest the eucalyptus leaves they need to live. Research has shown that koala faeces can be fed if pap is unavailable but the numbers of bacteria are much lower (Osawa et al 1993). These bacteria do not survive freezing, so it must be fed fresh. It seems ludicrous to suggest that a specialised feeder like the koala could benefit from some type of generic probiotic.
Bacteria are like everything else. Once they have settled down and made their home somewhere they are very difficult to shift. Research has shown that the bacteria provided in probiotics do not establish themselves in the intestine but are rapidly washed out (Tannock 1999), necessitating a continual input of bacteria. Very handy for the manufacturers. To have any kind of lasting effect they need to be fed to juvenile animals that haven’t had their guts colonised by bacteria. Or to an adult that has had its bacteria nuked with a big dose of antibiotics. Like me. This was attempted some years ago to cure my intestinal complaint; lots of antibiotics followed by lots of probiotics followed by no improvement whatsoever. N = 1, however.
The other problem with probiotics is that they are not very well regulated. An interesting study published some years ago examined eight veterinary and five human probiotics. Only two of these were accurately labelled. Five of the veterinary products did not specifically list their contents. Most products contained low concentrations of viable organisms (dead bacteria are no good to anyone). Five products did not contain one or more of the stated organisms, and three products contained additional species. Some products contained organisms with no reported probiotic effects; some of which could be pathogens (Weese 2002).
To sum up, there is no doubt that the bacteria in all our guts are vital for our survival. There appears to be some evidence that probiotics can have mild beneficial effects but the important thing is that the bacteria are species specific. So, unless you’re prepared to drink a faecal shake from a healthy friend of yours you are better off saving your money.
Dr. F. Bunny
Fuller, R. 1999. Probiotics for farm animals. In: Tannock, G.W. (ed.). Probiotics: A Critical Review. Horizon Scientific Press, Wymondham, Norfolk, U.K. Pp. 15-22.
Holz, P.H., and D.R. Middleton. 2002. The effect of probiotic feeding on Salmonella excretion in carpet pythons (Morelia spilota). Journal of Herpetological Medicine and Surgery 12: (3) 5-7.
Osawa, R., W. H. Blanshard, and P.G. O’Callaghan. 1993. Microbiological studies of the intestinal microflora of the koala, Phascolarctos cinereus. II. Pap, a special maternal faeces consumed by juvenile koalas. Australian Journal of Zoology 41: (6) 611-620.
Tannock, G.W. 1999. A fresh look at the intestinal microflora. In: Tannock, G.W. (ed.). Probiotics: A Critical Review. Horizon Scientific Press, Wymondham, Norfolk, U.K. Pp. 5-14.
Weese, J.S. 2002. Microbiologic evaluation of commercial probiotics. Journal of the American Veterinary Medical Association 220: (6) 794-797.
What puzzles me is, if there is an after-life and it is as wonderful as all the various religious leaders profess it to be, then why are they all still here? Crazy as they were, at least our friends from Heaven’s Gate and the various other suicide cults put their money where their mouth was. They believed there was something to go to that was better than their current earthly existence, and they acted on that belief. I have to admire the courage of their convictions.
As opposed to all the other living religious leaders, who spend an enormous amount of time asking their followers to martyr themselves, without ever volunteering to do so themselves. If this life is so miserable and transient and the next one is so glorious I would have thought they would be tripping over themselves to get there. More’s the pity that they are not.
And why rail against all the infidels and injustices in this life, when it’s all temporary and an eternity of paradise awaits just around the corner? Surely killing all the unbelievers is counterproductive, because they are receiving a quick trip to their version of paradise, rather than being left to suffer a bit longer on this plane of existence. Except for the murdered atheists, who just stay dead and buried. At least we won’t have to put up with an eternity of preaching, hymns and virgins. Actually I could probably cope with the third one, although I’ve never quite worked out what the virgins get if they martyr themselves.
Dr. F. Bunny