Fighting infectious diseases

[Franky]

Good article by DR. MIR M. MANSOOR

The trade in wildlife provides disease transmission mechanisms that not only cause human disease outbreaks but also threaten livestock, international trade, rural livelihoods, native wildlife populations, and the health of ecosystems in general. Outbreaks resulting from wildlife trade are causing economic damage worth billions of dollars globally each year. Rather than attempting to eradicate pathogens or the wild species that may harbor them, a practical approach would include decreasing the contact rate among species, including humans, at the interface created by the wildlife trade.

Threats to global health and risk factors for emerging infectious diseases run the range from climate change to poverty to security issues, but only few are as immediately manageable as the global trade in wildlife. Trade in wildlife provides disease transmission mechanisms at levels that not only cause human disease outbreaks but also threaten livestock, international trade, rural livelihoods, native wildlife populations, and the health of ecosystems.

As such, it is likely that frontline wildlife field functionaries, hunters/poachers, middle marketers or facilitators, and consumers experience some type of contact as each animal is traded. Increase in illegal wildlife trade, coupled with rapid modern transportation increases the movement and potential cross-species transmission of the infectious agents that every animal naturally hosts.
Quantifying the wildlife trade is almost impossible since it ranges in scale from local barter to major international routes, and much is conducted illegally or through informal networks. Some estimates indicate that about 40,000 live primates, 4 million live birds, 640,000 live reptiles, and 350 million live tropical fish are traded globally each year.

Since 1980, more than 35 new infectious diseases have emerged in humans, at the rate of 1 every 8 months. The origin of HIV is likely linked to human consumption of nonhuman primates. In USA, the Ebola hemorrhagic fever outbreaks in humans have been traced to index patient contact with infected great apes that are hunted for food. SARS-associated coronavirus has been associated with the international trade in small carnivores and a study comparing antibody evidence of exposure to this coronavirus demonstrated a dramatic rise from low or zero prevalence of civets at farms to an approximately 80% prevalence in civets tested in markets.
The unintentional movement of infectious agents on account of wildlife trade is not limited to human pathogens but also affects pathogens of domestic animals and native wildlife. Isolation of H5N1 type A influenza virus from 2 mountain hawk eagles illegally imported to Belgium from Thailand; entry of paramyxovirus (highly pathogenic for domestic poultry) into Italy through a shipment of parrots, lovebirds and finches imported from Pakistan for the pet trade; introduction of Monkeypox to a native rodent species and subsequently to humans in the United States by importing wild African rodents from Ghana for the US pet trade; identification of Chytridiomycosis, (a fungal disease) as a major cause of the extinction of 30% of amphibian species worldwide and its spread by the international trade in African clawed frogs � all are suggestive of role played by wildlife trade in spread of emerging infectious diseases in non human species.

Many diseases are transmitted through the same species of parasites carried by imported animals. For example, the commonest parasite i.e. ticks, carry many diseases that threaten livestock and human health, including heartwater disease, Lyme disease, and babesiosis.

The possibility of emerging infectious diseases spreading between persons and animals is rising, fueled by human activities ranging from the handling of wild animal origin products and the trade in exotic animals to the destruction or disturbance of wild habitat. In a list of about 1500 human pathogens, 61% are known to be zoonotic, and multiple host pathogens are twice as likely to be associated with an emerging infectious disease of humans. Seventy seven percent of pathogens found in livestock are shared with other host species.

In addition to the direct health effects of the pathogens on persons and animals, animal-related disease outbreaks have caused hundreds of billions of dollars of economic damage globally, destabilizing trade and producing devastating effects on human livelihoods. The rash of emerging or reemerging livestock disease outbreaks around the world since the mid 1990s, including bovine spongiform encephalopathy, foot-and-mouth disease, avian influenza, swine fever, and other diseases, has cost the world�s economies billions of dollars. In early 2003, the United Nation�s Food and Agriculture Organization reported that more than one third of the global meat trade was embargoed as a result of mad cow disease, avian influenza, and other livestock disease outbreaks. Efforts to control the spread of avian influenza in Asian countries since 2003 have required the culling of 140 million chickens. The projected growth of industrial livestock production in non industrialized countries to meet global protein demand will increase the impact of future disease outbreaks on economic and food supply security. Some of these outbreaks will inevitably be linked to the trade in wildlife.

Now, after recapitulating the whole process involved in spread of emerging infectious diseases from the wild species to other fellow denizens sharing this planet, it seems more practical for managers, marketers, middlemen, biologists, scientists and other sections of the society involved in the process to focus on decreasing contact among species rather than attempting to eradicate pathogens or the wild species that may harbor them. Closing down retail poultry markets in Hong Kong for 1 day per month reduced the rate of H9N2 avian influenza virus in market birds significantly. Focusing efforts at markets, especially in Southeast Asia, to regulate, reduce, or in some cases, eliminate the trade in wildlife could provide a cost-effective approach to decrease the risks for disease for humans, domestic animals, wildlife, and ecosystems.

(Dr. Mir M. Mansoor is Chief Wildlife Biologist J&K State Wildlife Protection Department. He can be mailed at mmmnsur@yahoo.co.in)