Animal Health Matters - Introduction

Introduction:

Healthy Landscapes, Healthy Lives

In 1933, Aldo Leopold stated that the “role of disease in wildlife conservation has probably been radically underestimated.” Today, infectious and noninfectious diseases of humans, domestic animals, and wildlife are finally being recognized as an increasing challenge to efforts aimed at improving the human condition as well as to programs aimed at conservation and sustainable management of natural resources. As human populations and global demand for resources continue to expand, wild landscapes are lost, fragmented and degraded, pushing wildlife into smaller and smaller remnants- mere islands in a sea of humanity. With people spreading into wilderness areas in search of land, food, and other resources, as well as for recreation, the needs of people and the needs of wildlife are increasingly in conflict. Often overlooked, one of the most significant consequences of people and their domestic animals coming into increasingly close contact with wildlife is a significant increase in disease transmission amongst people, livestock, and wildlife.

Foreign Assistance and Unforeseen Impacts on Health

Some well-intentioned development initiatives as well as conservation projects have unwittingly introduced diseases into wildlife populations. Others have been unsuccessful because they failed to take disease factors into consideration. Domestic dogs have spread fatal distemper to lions and other predators in the Serengeti ecosystem, and disease has helped extirpate African wild dogs throughout much of their range. Chickens used to feed eco-tourists may have infected wild parrots with Salmonella, known to cause avian infertility. Ill tourists, project staff, and local people have been incriminated in transmitting fatal respiratory infections, measles, and polio to gorillas and chimpanzees in Africa with devastating consequences.  In fact, examples of the importance of paying attention to wildlife health issues in conservation and development projects abound.

Wildlife Health and Development Efforts: An Ounce of Prevention is Worth a Pound of Cure •  Throughout tropical and sub-tropical South America, peccaries provide a significant source of protein for indigenous hunting communities.  Studies to elucidate population dynamics that could help establish sustainable harvest rates have depended on theoretical assessments of reproductive capacity due to a lack of information on the actual variation in reproductive success.  Infectious diseases can have significant effects on reproductive success; initial studies on one population of peccaries in Bolivia have shown that 25% of the population has been infected with leptospirosis.  This disease is known to cause stillbirths and abortions in other mammal species, including domestic swine. Integrating further health evaluations in other populations could provide data needed for more accurate modeling of reproductive rates and population dynamics. Models lacking this information could inadvertently over-estimate the levels of sustainable harvesting. • The use of ecotourism to support conservation efforts raises concerns about the impact of human proximity on wildlife in some of these projects, but little has been done to quantify the effects.  In a project where tourists were allowed to visit and participate in an endangered macaw breeding and re-stocking program, Salmonella bacteria were found to be infecting the hand-reared, released birds.  This bacterium is known to cause infertility and poor hatching success in other bird species.  Releasing infected birds provides a route of contamination for wild macaw populations.  The source of the Salmonella bacteria was most likely either the domestic poultry brought in to the remote site to feed the tourists and staff, or rodents that infest the lodge facilities.  Without health evaluations, the threat to wild populations would never have been identified and management changes would not have been made to correct the problem. • Chlorinated pesticides (agents such as DDT and its metabolites) are being found in colonies of endangered sea birds, seals, and seal lions in remote protected areas of Argentina and Peru. These chemicals have been shown to affect reproductive success in many species.  Sources of these toxins have not been identified, but agricultural run-off and contamination of fish stocks (and thus the food chain) from areas of agricultural development hundreds of miles away are highly likely.  To date, no studies have been conducted to identify the sources of pesticide contamination, nor have studies been instituted to assess the effects on wildlife populations.  While environmental contaminants have traditionally been thought of as a more urban or “brown” issue, both ocean currents and animal migrations can result in population effects occurring in the most remote protected areas.   • Integrated Conservation and Development Projects, community-based conservation efforts, buffer zone management programs, and other multiple-use strategies are often correlated with the presence of an interface between wild and domestic animals.  Increasingly, disease transmission between these groups of animals has had a negative impact on wildlife (i.e., lions and wild dogs in Tanzania, rinderpest outbreaks in Kenya).  Wildlife is often erroneously implicated as the source of infections in domestic animals. Free-ranging guanaco in Argentina have long been thought to be the source of diseases for domestic sheep, while the only study conducted to date found just the opposite to be true. Typically, wildlife health information is gathered only after major mortality events (an approach providing no baseline for facilitating a complete epidemiological picture). To be successful, proactive health assessments are required to more completely assess and address disease threats to conservation and development projects.  • Land-use choices are often driven by government incentives or subsidies that can favor unsustainable agriculture over more ecologically sound natural resource management schemes, particularly in marginal semi-arid lands.  With better understanding of disease epidemiology and the true costs associated with disease control and environmental degradation, land-use decisions might more often favor a return to natural production systems.  For example, in some parts of southern Africa, foot and mouth disease control programs to support beef production for an export market may not be as profitable or as environmentally sustainable as a return to multi-use natural production systems emphasizing endemic wildlife species.

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