Zoonotic Diseases: An Ecological Overview

Dr. Scott Clifford

Dr. Scott Clifford was born and raised on a large cattle ranching operation in Western Manitoba.

Education includes a B. Sc (Hon) in Zoology from the University of Manitoba in 1987 and D. V. M. from the University of Saskatchewan 1991.

He is also a certified instructor in Holistic Resource Management and in the discipline of Permaculture.

He has worked in a diverse array of veterinary practice worldwide and has owned and operated tow practices of his own.

Dr. Clifford has taught ecosystem health at the University level to senior veterinary students (Western College of Veterinary Medicine 1996).

Dr. Cliffords has worked extensively in wildlife management/medicine internationally (Africa, North and Central America).

For the past decade he has founded several ecologically and biomedically based businesses.

These include:

Natural Landscapes; A company, which utilizes large herding animals for landscape and vegetation modification.

Primal Veterinary Diets; A neutroceutical firm, which produces raw food diets for companion carnivorous animals (dogs, cats, ferrets etc. www.primalvetdiets.com )

Exos Corporation: Multinational firm specializing in design and development of biologically productive and diverse properties using permaculture (permanent agriculture) technologies. This firm is owned out of Central America but consults worldwide).

In partnership with his family he runs a bison and cattle ranching enterprise near Dauphin.

His current research focus is developing biologically based artifacts (biotechnique) as an alternative to current industrial/ non-animate technology.

Zoonotic Disease: An Ecological Overview

All disease is a manifestation of larger epidemiological and thus ecological processes.

To properly understand current "emerging" diseases it behooves the researcher to take a broad look at the information available from the disciplines of paleontology, geology and the numerous sub disciplines of ecology. This provides perhaps a better perspective than does focus on the organismal and individual patient level.

The story of disease generally, is of course very ancient. This particular story begins more than 200 million years ago with what I prefer to call the Pangean Paradox. At this time all land masses on earth where coalesced into one single supercontinent known as Pangea. This was a time of the mammal like reptiles and served as the birthplace for both early mammalian life as well as that of the various dinosaur lines.

Generally speaking the floral and faunal kingdoms at this time were fairly homogenous. Given a single landmass and giant oceanic realm the opportunities for island biogeography and subsequent speciation were limited. It was a time of cycads and redwoods, giant sauropod dinosaurs and "micromammals". The paradox exists because although it was a time of very large individual life forms the overall diversity when compared to today was quite low.

As geologic time passed plate tectonic activity forced Pangea to separate. First into a northern laurasia and southern Gondwanaland. Further separations drove continental plates worldwide and served as the basis of the tremendous burst of speciation and expanding biodiversity that the world currently contains. The opening of numerous ecological niches along with the development of the plant family known as angiosperms has greatly facilitated tremendous speciation following the rules of island biogeography and punctuated quilbruim theory.

So the Stage has Been Set:

We have a very diverse planetary ecological system based upon a long-term evolutionary trend toward relatively isolated populations of flora and fauna.

Something relatively unique occurred 5-8 million years before present with the development of the hominid family line in southern or eastern Africa. Upright walking highly mobile primates began to develop an evolutionary centre ultimately giving rise to several distinct lineages.

The earth has not only seen a diverse array of flora and faunal forms but in fact has given rise to several distinct forms of hominids. These hominid lines began a major expansion out of Africa with the development of the genus homo and after the development of fire utilization and basic tool use.

Indeed up until as recently as 30,000 years ago Homo sapiens shared the planet with the very distinctive Homo sapiens Neanderthals. These two distinct forms may even have had a separate full species designation. The main point here is that human beings are only unique at the behavioural level and through out the use of fire and complex artifacts. Biologically Homo sapiens is simply one mammal among many.

•  Between 100,000 and 12,000 years ago human migrations spread our form of humanity onto every continent except Antarctica. This was associated with a global extinction event that encompassed a majority of mega faunal forms (animals larger than 45kg) and included the Neanderthal lineage of humans. This event seems to have been caused by Homo sapiens through environmental modification of ecologies by fire use. Overhunting of hindgut fermentors (elephant lineages especially) may have also been a significant factor.

•  Between the years 900-1900 colonial Europe began a large-scale expansion. This has become known as ecological imperialism. This expansion was made possible indirectly by the development of sophisticated techniques for biological manipulation. The rise of agriculture and the utilization domesticated animals allowed higher populations and more sophisticated forms of cultural development to occur.

This was followed by the technological revolution of metallurgy and this carried the European culture worldwide.

It is at this time that we begin to have the first readily available documentations of diseases zoonotic and otherwise.

It has been said that at least two-thirds o fall infectious diseases are in fact zoonoses. The true number is probably a lot higher in reality.

The short list of diseases that European culture brought with them to North America is impressive: small pox, chicken pox, plague, malaria, typhoid, cholera, yellow fever, dengue fever, scarlet fever, ameobic dystentery, influenza.

Many of these ills are the result of microbial life (bacterial or viral) cycling between animal hosts and humans in either domestic or wildlife scenarios.

•  Modern human movements (1900-present) subsidized through fossil fuels have effectively closed the seams of Pangea. Today we have large scale mixing of floral and faunal components that have long been separated. This transcontinental movement of humans and ecological elements are recreating a more homogenous ecology worldwide. Humanity through cultural activity is increasingly trying to simplify the world's ecology.

We utilize a relatively small variety of plants and animals in increasingly large biological production units. This fosters a great bioconcentrative effect if a biological production units. This fosters a great bioconcentrative effect if a pathogen can reproduce in a host animal kept in these conditions.

Also, humanities last great expansion into wild, ecologically intact regions allows contact with new undiscovered pathogens. This activity also encourages the novel environments that allow new pathogen strains to develop and/or to be transmitted to humans or to animal life that contacts humans.

It is not by chance that all new emerging diseases seem to be zoonotic. Avian influenza, Nipah virus, West Nile, Ebola, Lyme, AIDs, SARs all have emerged from wildlife hosts in the recent past.

SARs:

Why eating cats is never a good idea!

Probably the result of human consumption of palm civets under relatively unhygienic conditions.

Has probably been accelerated in high-density housing units with domestic cats.

Nipah:

Mix fruit bats, intensive swine production and high density human populations.

West Nile Virus:

Documented entry into North America in 1999.

Possibly via bird importation into the U.S. but maybe by natural bird migration.

Bioconcentration via large wild avian poplulations and spread via large number of mosquito species.

BSE:

Zoonosis by association?

Undoubtly causes disease in bovidae.

Large scale bioconcentration occurred as the result of large scale feeding of rendered ruminant offals back to ruminants.

Tremendous economic and political dislocations based upon media scrutiny and misinformation.

Very low level of risk of human transmission.

Avian Influenza:

Many strains of varying pathogenicity.

Wild birds natural hosts.

Domestic poultry production ideal bioconcentration units.

Great risk if mutation occurs: human-to-human transmission (pandemic possibilities).

Implication of Zoonotic Diseases

Short Term

We will see a lot more of these types of infectious diseases.

Above listed trends combined with global climatic change will make new diseases emerge and old diseases remanifest and expand.

Pandemic possibilities highest with respiratory transmitted forms-influenza esp.

Effect on global human population is probably minimal. Our response times and technical expertise to deal with these outbreaks is getting more and more efficient.

But you never know. Monkey pox virus could mutate (similar to smallpox virus).

Imagine if Aids virus could be transmitted via respiratory route!