|Sheep Ranching||en español|
Why is sheep ranching a concern?
Sheep are raised for both meat and wool. The number of sheep in the United States peaked at 51 million in 1884. Today, there are approximately 5.5 million sheep in the United States. Sheep account for less than one percent of total U.S. livestock. Texas, California, and Colorado are the top three sheep producing states.
A health and environmental concern about sheep ranching is a practice called sheep dipping. To protect sheep from parasites and insects, sheep are led through a long, narrow, concrete-lined in-ground trench filled with pesticides. Sheep dipping can also take place in a steel transportable dip tank.
Sheep dipping has most commonly used two kinds of chemicals. Organophosphorus compounds used are pesticides that are related to certain chemical warfare agents and are acutely toxic to humans. Synthetic pyrethroids used are also pesticides that are moderately poisonous to humans.
In the Southwest, the Navajo people traditionally raised sheep to provide meat and wool to weave blankets and rugs. Sheep ranching, weaving, and fiber production remain part of the modern Navajo economy.
From the early 1930s to late 1980s, the Navajo Nation and Bureau of Indian Affairs used toxaphene and lindane-based solutions to treat sheep in dip vats. Toxaphene and lindane are organochlorine pesticides and are both listed as "reasonably anticipated to be human carcinogens" in the Fourteenth Report on Carcinogens published by the National Toxicology Program. They are both persistent organic pollutants and endocrine disruptors.
During this time, approximately 250 sheep dip vats were built throughout the Navajo Nation. The pesticide solutions drained into unlined pits or local streams. High concentrations of toxaphene and lindane were suspected of contaminating soil surrounding the sheep dip vats and adjacent water supplies.
Approximately 20,000 gallons of pesticides were used each year until the sheep dipping process ceased in the 1980s. The production and use of toxaphene was banned in 1990.
In 1994, the Navajo Superfund Program and U.S. Environmental Protection Agency began cleaning up 22 sheep dip vats through the Superfund Program. They were successfully cleaned up by late 1995 using bioremediation, or natural processes such as microbes and bacteria.
At least 50 sheep dip vats on Native American lands have been Superfund sites.
Sheep may have diseases that can be passed on to people who handle them. These are called zoonotic diseases. Sheep may have serious diseases such as rabies, anthrax, and brucellosis, which is caused by bacteria. They may have Q fever, an infection that can be passed from sheep through contaminated barnyard dust.
Sheep may also contract ringworm and a skin disease called soremouth, or orf.
Sheep may spread bacteria such as E. coli and salmonella and cryptosporidium, a parasite. Sheep may carry lice and keds, which are wingless flies that as adults look like ticks.
Sheep may contract scrapie, a fatal disease affecting the central nervous system of sheep. It is in a class of diseases called spongiform encephalopathies that may be linked to disease in humans. Scrapie does not appear to be transmissible to humans.
People working with sheep should wear appropriate personal protective equipment such as rubber gloves.
Handling sheep poses safety concerns. Sheep may become agitated if they are separated from their herd, hear loud noises, or see unfamiliar moving objects. Sheep have a narrow field of vision and can become spooked if handlers suddenly appear. Sheep may jump with enough force to break a handler’s leg. Sheep handlers should avoid turning their backs on rams, who may charge or butt humans.
This description is based on the information found in the Web links listed with this topic.
Web Links from MedlinePlus (National Library of Medicine)
Animal Diseases and Your Health
Farm Health and Safety
Animal Handling Safety (California State Compensation Insurance Fund)
Farmworkers, Farm and Ranch Animals. Haz-Map (National Library of Medicine)
Handling Farm Animals Safely (National Ag Safety Database)
Zoonotic Diseases of Sheep and Goats (US Department. of Agriculture)
Last Updated: November 28, 2016