Positive Health Online

Introduction

Biologists are commonly impressed by the health and vigour of wild animals free-ranging in their natural habitat, remarking that they are generally immune to vector-borne disease and show few clinical signs of illness from parasite infections.1 Closer examination reveals that these outwardly healthy animals may not, however, be completely free of pathogens (disease-causing organisms) or signs of previous infections. Quite evidently, though, the presence of a pathogen is not the same as the presence of disease. Indeed, such resilience in the face of a continuous and ubiquitous onslaught could be said to be a sign of extremely good health.

Unfortunately, wild animals successfully keeping disease at bay are feared as ‘carriers’ of disease to more vulnerable domestic stock. Often they are slaughtered to protect our investments. In an attempt to reduce bovine tuberculosis (TB) in confined cattle, the British government intends to cull 20,000 wild badgers in the West of England because some of them ‘carry’ TB (even though research indicates that it is the intensive housing conditions in which cattle are kept that is by far the most significant contributor to their ill health). In mid-Wales earlier this year, 6,000 healthy, free-ranging hill sheep, which had successfully fought off the foot-and-mouth virus, were slaughtered for fear that they might spread the disease to neighbouring farms.

Instead of killing successful healthy animals, should we not be interested to know how they manage to fight off infectious disease without recourse to antibiotics and vaccines? As we in the West struggle to cope with increasing levels of chronic disease, and are threatened with a return to higher levels of infectious disease in the face of drug-resistant pathogens and parasites, we would do well to re-learn from wild animals any health-enhancing natural strategies we have long forgotten.

How Animals Avoid Disease

The answer is not merely that natural selection produces well-tuned immune systems (for it surely does). No, the answer has much to do with the actions animals take to avoid, prevent and treat ill health. Behaviour is, after all, the first line of defence against a health threat, and any action that helps avoid or prevent disease, protects the immune system from unnecessary work.[1]

Fear of the Unfamiliar
Many instinctive fears and dislikes have evolved to protect animals from pathogen hot spots. The natural fear of strangers shown by all wild animals may be based on the experience that strangers bring novel diseases – often followed by death. It was not the superior warfare of the 15th-century Europeans that led to the downfall of the Central and South American Indian civilizations but the novel diseases they brought with them. To the uninitiated, measles is as deadly as biological warfare. Wild chimpanzees show an innate distrust of contact with strangers. Jane Goodall observed a female approach a male of another group and reach out her hand to touch his arm. He immediately moved away, picked some leaves, and wiped where she had touched him.[2,3] Fear of the unfamiliar is helpful for avoiding contact with foreign pathogens.

With today’s increasing amounts of international travel and trade, people, food and produce are spreading novel pathogens far and wide.

The Dangers of Cannibalism
Cannibalism is not as common as it might be (from an evolutionary point of view) considering the obvious nutritional and competitive advantages of eating other members of one’s own species. However research shows that eating one’s own dead is more dangerous than eating the dead of other species. Cannibalism is a severe health risk. Pathogens adjust quickly to the physiological conditions in which they find themselves, and so pathogens incubating in a member of one’s own species will be better adapted and therefore more dangerous to a cannibal than those incubating in a member of another species.[4]

In those few human cultures where cannibalism has been ritually practised, some form of debilitating neurological damage has ensued. Bovine spongiform encephalopath (BSE), or mad cow disease, was caused by feeding not just meat to a vegetarian animal but meat of its own species – ground up bits of cattle brain were hidden in cattle feed. In the wild, cattle avoid eating flesh even when searching for minerals amongst weathered bones, and they never engage in cannibalism.

If the lessons of disease-avoidance demonstrated by animal behaviour had been observed, mad cow disease and its nvCJD (new variant Creutzfeld-Jakob disease) offshoot could have been avoided.

How Animals Prevent Illness

Nutritional Wisdom
Animals also take actions that prevent illness. Their ability to select competently a well-balanced diet for changing individual circumstances, from food that changes in both composition, location and availability, is known as ‘nutritional wisdom’. Quests for specific nutrients lead pregnant rats to increase their intake of calcium-rich foods, sheep to bite the heads off shearwater chicks for the phosphorus they need, tortoises to dig for calcium impacted deep below the desert surface, and moose to wade out into icy water to reach mineral-rich aquatic plants. Just before migration, garden warblers change from eating insects to figs (even though insects are still available). The figs are thought to alter metabolic rate to allow a faster deposition of fat reserves. Before hibernation, golden-mantled ground squirrels change the type of fats they consume. Normally they eat high-energy fats that give off toxins as they are used up, but before hibernation they change to eating lower-energy fats that will not give off toxins during their winter sleep. Scientists do not yet understand how animals manage to achieve such well-balanced diets.[5]

Ingesting Health Bacteria
Animals also actively manage their symbiotic associations with micro-organisms. Not all bacteria are harmful. Some are so important to health that ill health results from not having them. In the mammalian intestine, for example, the bacterium Bifidobacterium not only keeps pathogenic bacteria in order by competitive exclusion (suppressing the growth and division of other bacteria) but also helps prevent colon cancer. Within the first weeks of life, an infant mammal gets its complement of Bifidobacteria from its mother’s milk. Once weaned, young animals continue to obtain boosters of their mothers’ resident microflora from any food she may chew for them. Many youngsters also top up their gut microflora by eating their mothers’ faeces. As soon as young foals are born to feral mares in the New Forest, they start to nibble at the mothers’ dung. This habit gradually subsides after three months.

Up to 90% of the natural diet of wild gorillas consists of the antimicrobial plant Aframomum (a member of the ginger family). What scientists have recently discovered is that this diet cleverly kills pathogenic bacteria such as Shigella and Salmonella while allowing facultative (helpful) bacteria to thrive in the gut. In captivity where gorillas are denied their natural diet, they frequently suffer from serious bacterial gut infections such as shigellosis (which can later lead to arthritis). Keeping animals healthy in captivity clearly requires a better appreciation of how they stay well in the wild.[6]

Self-Medication
Most notable is the constant care and attention that mammals and birds pay to the condition of their skin, fur and feathers – grooming and preening away bacteria, fungi, ectoparasites and dirt. Starlings, sparrows and eagles select aromatic-astringent herbs to line their nests during the breeding season. The volatile oils of the herbs enhance the chicks’ chances against an onslaught of biting insects and skin parasites.[7] During an outbreak of malaria in Calcutta, biologists noticed that house sparrows switched to using quinine-rich leaves of the uncommon Krishnachura tree to line their nests. The sparrows appeared to be medicating against malarial parasites.[8]

There are also many different types of so-called ‘illness-response’ behaviours which animals perform when sick. Rats, for example, eat clay when they feel sick. Clay effectively binds toxins, preventing them from entering the bloodstream. In this way clay eating is a form of self-medication.9 Rats can withstand a potentially lethal dose of Paraquat poisoning if allowed access to clay. Numerous other species of mammals, birds and insects eat clay too, and geophagy (earth eating) is thought to be one of the earliest forms of medicine. This simple, safe form of self-medication can be applied in human medicine when poisoning results from unknown sources.

The mountain gorillas of Mgahinga National Park, Uganda, eat the bark of the Dombeya quinqueseta when suffering from diarrhoea. In the laboratory, this bark inhibits the growth of Salmonella-pathogenic bacteria that commonly cause diarrhoea.6 When suffering the effects of nodule worm infestations (and presumably feeling some gastrointestinal malaise) chimpanzees, bonobos and gorillas seek out rough, hairy leaves, carefully fold them and swallow them whole. Later the leaves are excreted with live, wriggling worms entrapped in the hairy folds. Physical scours (to clean out intestinal worms) are used by other species such as bears, geese, tigers and wolves.10,11 Such a simple, safe approach to de-worming could be useful as all the common human and livestock parasites are currently developing
resistance to chemical anthelmintic drugs.

Conclusion

What is clear is that wild animals pay constant attention to their health. They cannot afford to let their condition decline before taking action. Prevention is, in this context, better than cure. Nature is short on sympathy. Those individuals who have not paid close attention to their health have not survived, and so natural selection has honed ‘health-maintenance strategies’ to a fine art. We have much to remember from observing wild animals in their natural habitat where they demonstrate these skills. Yet most of us remain ignorant of any innate strategies for health we may retain. Medicine is no longer something we do, it is something we buy.

The simple actions we see animals practising (many of them shared by traditional herbalists and naturopaths) are not quaint, old-fashioned superstitions. They are strategies that have stood the test of millennia of natural selection, and as such form the evolutionary genesis of today’s holistic medicine. Perhaps, by trusting our instincts a bit more, we could regain some aspects of wild health.

References

1.    Hart BL. Behavioral Adaptations to Pathogens and Parasites: Five Strategies. Neuroscience and Biobehavioral Reviews. 14: 273-94. 1990.
2.    Goodall J. The Chimpanzees of Gombe: Patterns of Behavior. Belknap Press of Harvard University Press. Cambridge, MA. p545. 1986.
3.    For a general review of how animals avoid disease see: Loehle C. Social Barriers to Pathogen Transmission in Wild Animal Populations. Ecology. 76(2): 326-76. 1995.
4.    Pfennig DW, Ho SG and Hoffman EA. Pathogen Transmission as a Selective Force Against Cannibalism. Animal Behaviour. 55(5): 1255-61. 1998.
5.    Provenza FD. Post-ingestive Feedback as an Elementary Determinant of Food Preference and Intake in Ruminants. Journal of Range Management. 48: 2-17. 1995.
6.    Berry JP. Chemical Ecology of Mountain Gorillas (Gorilla gorilla beringei) with Special Reference to Antimicrobial Constituents in the Diet. PhD
dissertation. Cornell University. Ithaca, NY. 1998.
7.    Gwinner H, Oltrongge M et al. Green Plants in Starling Nests: Effects on Nestlings. Animal Behaviour. 59(2): 301-09. 2000.
8.    Sengupta S and Shrilata. House Sparrow Passer domesticus uses Krishnachura Leaves as an Antidote to Malarial Fever. Emu. 97: 248. 1997.
9.    Takeda N, Hasegawa S et al. Pica in Rats is Analogous to Emesis: An Animal Model in Emesis Research. Pharmacology, Biochemistry and Behavior. 45(4): 817-21. 1993.
10.    Wrangham RW. Leaf Swallowing by Chimpanzees, and its Relation to a Tapeworm Infection. American Journal of Primatology. 37: 297-303. 1995.
11.    Huffman MA and Caton JM. Self-induced Gut Motility and the Control of Parasite Infections in Wild Chimpanzees. International Journal of Primatology. 22(3): 329-46. 2001.