According to the Center for Disease Control (CDC), approximately 75 percent of the newest emerging infectious diseases affecting humans are diseases of animal origin. They also report that approximately 60 percent of all human diseases are zoonotic - meaning they can spread from an animal to a human.
Producers who make their living working closely with animals, are on the front lines to see, identify, and fight these diseases. However, many producers may not know what they are dealing with.
There are numerous zoonotic diseases that can cause mild to severe symptoms and are a definite concern for farmers and ranchers and their families.
"While food borne outbreaks of zoonotic diseases continue to challenge public health authorities, the human cases of some of the more severe diseases - such as anthrax, tularemia, or plague - are extremely rare," said Marty Zaluski, state veterinarian for the Montana Department of Agriculture.
Here is a list of diseases and their human symptoms that affect our area.
Anthrax; There were anthrax cases reported in 2007, and a large outbreak in Gallatin County in 2008. Cattle, sheep and goats are at the highest risk of developing anthrax, but other farm animals as well as wildlife and humans, can contract the disease. Anthrax spores can survive for years in the environment.
"The actual mechanics is not well understood. The classic scenario seems to be a drought or long, dry, hot spell followed by a significant rain. That stirs up the soil and expose the spores and makes them more infective," Zaluski said.
Most animals are infected when they graze on soil contaminated with anthrax. The most common clinical sign in animals is sudden death. Blood may be seen oozing from the mouth, nose and anus of dead animals infected by anthrax.
A vaccine for livestock is available in areas where anthrax is a common livestock disease. Animals suspected of dying from anthrax should be examined by a veterinarian immediately.
Humans can develop anthrax by handling products from infected animals or by breathing in anthrax spores from infected animal products, like wool, for example. People also can become infected by eating undercooked meat from infected animals or by being bitten by an insect carrying the bacteria.
If the anthrax enters a human through the skin via a wound or bite, a small sore will develop and then blister. The blister will enlarge into a black ulcer. Despite their appearance, the blister and ulcer do not hurt. If the anthrax is inhaled, humans will develop cold or flu-like symptoms with a sore throat, fever and muscles aches. Left untreated, it will develop into a cough with chest discomfort and shortness of breath.
Anthrax that is ingested will cause nausea, loss of appetite, bloody diarrhea, fever and bad stomach pains. Most anthrax symptoms in humans will appear within seven days of exposure, although inhalation anthrax can take up to a month and a half to appear.
Fortunately, the risk of becoming infected by anthrax through a natural exposure remains low. Anthrax is not known to spread from one person to another. It is listed by the CDC as a potential bioterrorist weapon and they give it the highest level of priority.
Brucellosis; While brucellosis can affect a wide variety of domestic animals including cattle, pigs, sheep, goats, horses and dogs, Zaluski said in Montana it is most often found in bison and some elk.
According to Zaluski, there are several types of brucellosis. "The ‘abortus' type occurs very infrequently and is typically limited to isolated cases in Texas and where the disease is transmitted from elk to cattle, such as in the Greater Yellowstone area."
Since 2007, Montana has had four livestock herds affected with a total of 18 animals. "Wyoming has had several more. Other reported cases in the U.S. may be Brucella Suis, due to a spill-over from feral swine in the South," he explained.
Humans become infected by coming in contact with animals or animal products that are contaminated with these bacteria. Thanks to a highly successful disease eradication effort in the U.S. Montana has had a total of only 32 human cases since 1960.
One of the most common ways for a human to contract brucellosis is by eating undercooked meats or unpasteurized soft Mexican cheese, said Zaluski.
"The last human case of brucellosis from an animal happened in the 1990s," said Zaluski.
Humans can become infected through skin wounds and penetration. This is of special concern to hunters, producers or veterinarians who may be working around animals with existing skin wounds or using sharp objects. There is also concern that veterinarians can become infected if they accidentally jab themselves while delivering an animal vaccine with the live virus.
"There are a handful of veterinarians in the state that are brucellosis positive but that is due to exposure while working on infected animals," he said.
Currently there is no vaccine for humans, but the disease can be treated through the use of antibiotics. Recovery may take several weeks or even months.
In humans, brucellosis can cause a range of symptoms that are similar to the flu and may include an undulating fever, which is a fever that comes and goes; sweats, especially night sweats; headaches, back and joint pains, and physical weakness. Severe infections of the central nervous systems or lining of the heart may occur.
Cryptosporidium; This parasite causes diarrhea in animals and humans. According to the CDC, it is one of the most common causes of waterborne diseases among humans in the United States. Most animals, both wild and domestic, can be infected with the parasite but symptoms are most commonly observed in calves less than 1 month old. Infected animals shed the organism in their feces, contaminating the environment. The parasite is then ingested by other animals who eat off infected ground or drink contaminated water.
Humans are most often infected when they fail to wash their hands after exposure to animals. A rancher, working with animals, may take a break out in the field to open a can of pop and get a drink. That simple and common action can cause the transmission of the parasite. Transmission can also occur through contact with contaminated recreational water, which often contains the urine and feces of nearby animals.
In humans, symptoms appear two to 10 days after infection and include explosive diarrhea, abdominal cramps and pain, fever, vomiting and weight loss. Some people may experience a recurrence of symptoms after a brief recovery. Symptoms can come and go over short periods of time for up to 30 days. The good news is that most people infected with cryptosporidiosis will recover without treatment.
Escherichia coli (E. Coli); This normal bacteria lives inside the intestinal tracts of people and humans. At the Animal Diagnostic Laboratory there are more than 70,000 different strains of E. Coli collected over the last 50 years. Most strains are harmless but some strains can cause severe problems in humans.
The bacteria is transmitted between farm animals through infected water and food. Often, when the bacteria gets into a water supply on a ranch or farm, it survives in the biofilm, or slime, that forms on the sides and bottom of the water container. Farmers and ranchers can remove this slim with brushes and hot soapy water that has been treated with bleach. Flies and insects can also transmit the disease through a herd by carrying the bacteria with them on their flights and landings. All farm animals, including dogs, can transmit E. Coli to their handlers.
Humans become infected by ingesting contaminated food or water, especially undercooked ground beef and unpasteurized juice and milk. Many cases could be avoided through proper cooking and food handling techniques.
Humans can also become infected after being exposed to the feces of an infected animal. A rancher may get the bacteria on his hand while working with cattle out in the yard. In a surprising find, the CDC notes the bacteria can even be passed to another person through a friendly handshake, such as when a rancher greets a neighbor who drops by for a visit. For that reason, hand washing is vital for all producers working with animals. E. Coli can cause stomach distress and diarrhea.
Giardiasis; According to the CDC, Giardia lamblia, often referred to simply as giardia, is a parasitic disease that infects nearly 2 percent of all adults worldwide. In fact, it is the most common parasitic disease affecting humans. Farmers and ranchers may be interested to know that infection rates go up in the late summer.
Giardia is present in soil, food and water that have been contaminated by infected feces. Humans become infected by ingestion of contaminated food or water. Symptoms include diarrhea, gas, greasy stools that tend to float, stomach cramps, and vomiting. Less common symptoms include itchy skin, hives, and swelling of the eye and joints.
Sometimes the symptoms of giardia resolve and then return again after several days or weeks. Drugs are needed to treat it.
Leptospirosis; This bacterial disease can occur in a large number of animals including cattle, sheep, goats, pigs, horses and dogs. Infected animals may show no signs of illness, although the most common sign in cattle are abortions or weak newborn calves. The bacteria is spread through the urine and can then survive in the water and soil for months.
Like so many zoonotic diseases, humans become infected by coming in contact with infected water, soil, food or other products that have been contaminated with the bacteria. Hand washing is vital. The bacteria can also enter the skin through a cut or scratch.
During times of flooding, the bacteria can enter a ranch's drinking water through seepage, so it is vital that wells be tested.
In humans, the disease begins abruptly with a high fever, headache, chills, muscle aches, vomiting, red eyes, diarrhea, rashes and abdominal pain. Then, if left untreated, it can progress to jaundice, which produces yellow skin and eyes, kidney damage, meningitis, liver failure, respiratory distress and even death. The time between a person's exposure to a contaminated source and becoming sick is two days to four weeks. Treatment is with antibiotics.
Listeriosis; The CDC says that the Listeriosis bacteria lives in decaying vegetation and low lying wet areas. The consumption of spoiled, moldy or improperly stored or silaged feed is often associated with outbreaks in animals. When livestock become infected, they begin to circle, show a lack of coordination and the inability to chew or swallow. Pregnant livestock may abort.
When infected animals are sent to processing facilities, the CDC said the bacteria can live there for years, contaminating other food products both before and after cooking or processing. Once it is brought home through food purchases, listeria not only survives in the refrigerator but can continue to grow. The only way to kill listeria in food is through cooking and proper pasteurization.
In humans, symptoms can include fever, muscle aches, headache, stiff neck, confusion, loss of balance, and convulsions. Pregnant women may experience a mild, flu-like illness followed by fetal loss or meningitis in their newborns.
Q Fever; "We've had some cases of Q Fever in the state from sheep and goats to their owners, in Cascade and Teton counties, said Zaluski.
Q Fever is caused by a bacteria that causes abortions in cattle, sheep and goats. Animals acquire Q Fever through contact with reproductive fluids and milk from infected animals. Humans are very susceptible to the disease and are easily infected, through contact and even inhalation, when they are exposed to birthing fluids and material from infected animals.
CDC said this organism is extremely hardy and resistant to heat, drying, and many common disinfectants. Because of that, the bacteria can survive for long periods of time in barns and corrals.
Symptoms in humans include high fevers, up to 104-105° F; severe headache; chills; sweats; non-productive cough; nausea; vomiting; abdominal pain; diarrhea; chest pain. More severe complications include pneumonia, hepatitis, inflammation of the heart, and central nervous system complications. Pregnant women who are infected may be at risk for pre-term delivery or miscarriage.
Although most persons with acute Q Fever recover, a post-fever fatigue syndrome has been reported to occur in 10 to 25 percent of patients. This fatigue syndrome is characterized by constant or recurring fatigue, night sweats, severe headaches, sensitivity to light, pain in muscles and joints, mood changes, and difficulty sleeping.
Treatment of Q Fever should be started in the first three days of symptoms yet diagnostic tests will frequently appear negative for the first 10 days. For that reason the CDC recommends that treatment should never be delayed pending the receipt of laboratory test results or withheld based on an initial negative laboratory result. Initial treatment of Q Fever should begin based on symptoms and likelihood of exposure. Treatment can then be changed later, when laboratory tests return.
Rabies; "You can't neglect rabies. Every year in Montana we see a number of cases in horses and cattle, and we certainly have our share in skunks and bats," he said.
Every year the CDC reports that an estimated 40,000 people in the U.S. receive the rabies shot series because of exposure to the deadly viral infection. In addition, the U.S. public health cost associated with rabies is more than $300 million a year. Each year around the world, rabies results in approximately one death every 10 minutes, with almost 50 percent of the victims being children under the age of 15.
Domestic animals contract the disease through contact with contaminated animals with 90 percent of that contact occurring with wild animals. Among the worst carriers are skunks, raccoons, foxes, and bats. Domestic animals and even humans can contract the disease through contact with the saliva of infected animals.
One fact missed by many ranchers and farmers is that rabies can survive in the saliva or tissue of a dead animal, especially those recently dead. For that reason, producers should use care when moving an animal's body.
When livestock are infected they can exhibit a change in behavior that is marked by excessive vocalization. They also have difficulty swallowing and drool. They may show signs of paralysis.
Salmonellosis; According to the CDC, other food-borne illness have declined in the last 10 years but not salmonellosis. Though the CDC reports 40,000 cases of salmonellosis in humans every year they estimate the actual number of cases may be as much as 30 or more times higher or more than 1.2 million cases. Approximately 400 people die each year from this zoonotic disease.
All animals, domestic and wild, become infected as a result of ingesting contaminated feed, water or grass. The bacteria can live for months, and even years, in the environment, especially in wet and warm conditions. The bacteria is transmitted to humans through contaminated hands or surfaces coming in contact with food. It can cause diarrhea, fever, and abdominal cramps within 12 to 72 hours after infection. The illness usually lasts four to four to seven days and most persons recover without treatment. However, it may be several months before their bowel habits are entirely normal.
A small number of people will develop pain in their joints, irritation of the eyes, and painful urination, which is called Reiter's syndrome. It can last for months or years, and can lead to chronic arthritis which is difficult to treat.
Tuberculosis; Bovine tuberculosis is caused by a bacteria and is shed in respiratory secretions, feces and milk of infected animals. Cattle are infected by inhaling or ingesting the bacteria and suffer weight loss, weakness, low grade fever and coughing.
Because of an aggressive eradication program that has been underway since 1917, the USDA said that the threat of humans contracting bovine TB from domestic animals is extremely remote. The biggest risk, however, is still from wildlife that carry the bacteria, especially deer, raccoon or foxes. This wildlife is a threat to livestock. Bovine TB shed by infected wildlife can survive on hay and feedstuffs for months, then spread to cattle herds during feeding. Keeping hay and feedstuffs covered and finding ways to discourage wildlife around feeding areas is one way producers can protect their herds.
Vector-borne diseases; These are diseases spread from animals to humans through the bite of an insect, such as a tick, flea or mosquito.
West Nile Virus; Among the vector-borne diseases, Zaluski said that West Nile is always a concern. This disease is transmitted from birds to other humans and other animals through mosquitoes. The CDC reports there have been 1.5 million infections of West Nile virus since 1999.
"While the virus exists in Montana, we've had no reported equine cases. The horses in this state are quite well vaccinated," said Zaluski.
There has been one case of human West Nile virus in Montana this year. Eighty percent of the people infected with West Nile virus will not show any symptoms at all. The remaining 20 percent will develop fever, headache, body aches, nausea, a skin rash, vomiting and swollen lymph glands. One in 150 people will develop neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness and paralysis. These symptoms may last several weeks, and neurological effects may be permanent.
Being outside, means producers are at risk to mosquito bites and should take precautions. While birds die from West Nile virus, the occasional dead bird should not be of concern. However, if producers find an unusual amount of dead birds on their land, they should contact a local veterinarian about the possibility of West Nile virus.
Plague; This is the disease known as the Black Plague and, while it is most often associated with history, Zaluski said there have been several reports of the disease in domestic cats in Montana.
It is spread by fleas, which transmit the disease from infected rodents to humans. Working on a ranch or farm means there are rodents in the area. Producers should take care to keep grain spills cleaned up and properly store feedstuffs. Domestic pets, such as dogs and cats, should wear flea collars to reduce the chance of infected fleas hitching a ride.
If a human is bitten by an infected flea, they will experience fever and painfully swollen lymph nodes. They may also develop round swellings on their skin. The swellings may be mistaken for an allergic reaction or rash. Infected humans will then develop cold-like symptoms and the disease will continue to spread to other humans through coughing, sneezing or direct contact.
Tularemia; This is another disease that is spread through the bite of flies, ticks or fleas. It can also be contracted by touching an infected animal or through inhaling dust particles contaminated with the bacteria. The CDC also lists this disease as a potential bioterrorism threat.
There are four kinds of tularemia. In humans, the advent of tularemia is noted by the swelling of lymph glands in the area of the bite. Lymph glands under the arm, around the groin or in front of the ear can also swell. This can be spread through bites but also through fluids of an infected animal. During butchering or handling of a dead animal, the fluids can enter the human body through the eye, via splattering or by rubbing the eye.
Tick-borne diseases; There are many of these, including Rocky Mountain Spotted Fever, Relapsing Fever, Colorado Tick Fever, and Lyme disease. Most people infected with a tick-borne disease do not remember being bitten. If a tick is spotted on a human, even if it is not attached, it should be captured and stored in the freezer until the incubation period is passed, which is two to 14 days. Most symptoms of tick-borne illnesses include fever, headache, muscle aches, vomiting, dry eyes, neck pain, confusion and dizziness.
Summary; Any producer who suspects one of these diseases on their farm, even in the wildlife, should contact their veterinarian for advice. If a producer suspects they, a family member or an employee has any of these diseases, they should contact their physician immediately.
Luckily, many of the precautions taken to prevent these diseases are the same: Washing hands with soap after handling animals is the most important precaution. Soap should be readily available in the barn and lavatory areas. Antiseptic hand washes and wipes should be carried in all ranch vehicles and machinery cabs.
Also proper cooking and handling of food products is a must, including unpasteurized milk.
"There is a menagerie of potential zoonotic diseases that occur in Montana," said Zaluski. "They are out there and these are just some of the ones we have seen recently. We have been fortunate that most of the diseases have been found in animals, not people."
He would like to emphasize the continual need for a strong working relationship between the public health and animal health authorities and the role that producers can play as front-line observers.