Herd Health: What you should know about salmonellosis, leptospirosis and other herd infections
Thursday, June 10, 2010
A short primer on several diseases that can infect your herd and the people who work with it
by CATE DEWEY and BETH YOUNG
Salmonellosis
Salmonellosis is an infection caused by a group of bacteria called salmonella. There are many different types of salmonella bacteria, but the most common ones found in North America are salmonella typhimurium and salmonella enteriditis.
This family of bacteria can cause disease in humans and many species of animals. The bacteria are shed in the feces of infected people or animals. People are most often infected by salmonella through eating foods, such as meat, fruits or vegetables, which have been contaminated with feces. People can also become infected after handling pets and other animals that are carrying the bacteria.
What happens to pigs? Salmonella are very commonly found in the feces of pigs but, in most cases, infected pigs show no signs of disease. Some infected pigs do become ill and the clinical signs that are seen depend on the type of salmonella causing the infection. Some infected pigs can develop a blood infection, called septicemia. These pigs are depressed, have a high fever, go off-feed and develop a reddish-purple discolouration of the skin. Diarrhea can occur after several days of illness.
Sometimes these pigs die suddenly with no apparent clinical signs. Other pigs develop the intestinal form of salmonellosis. These pigs can have diarrhea, a low-grade fever, are unthrifty and may develop a rectal stricture. Salmonellosis can affect pigs of any age but, typically, weaner and grower pigs are most often affected.
What happens to people? People with salmonellosis have fever, abdominal cramps and diarrhea that can last from four to seven days. Most people recover without treatment, although some people require hospitalization to replace lost fluids or for antibiotic treatment.
The bacteria can sometimes spread from the intestines to the blood stream, causing severe illness that occasionally results in death. The very young, elderly or those with compromised immune systems are most likely to develop the severe form of the disease. Some people who recover from the initial illness can go on to develop a condition called Reiter's Syndrome. This syndrome, which can persist for years, is characterized by joint pain, eye irritation and painful urination, and often results in chronic arthritis.
What can be done to prevent it spreading? The most common way salmonella is spread from pigs to people is through the consumption of improperly cooked pork products or other foods that have been in contact with raw pork or pig feces through improper food handling.
Salmonella contamination of pork can occur at the abattoir and, as a result, abattoirs have many measures in place to help minimize carcass contamination. At the farm level, many suggestions have been made for management changes producers can take to minimize the prevalence of salmonella in pigs, including improved barn hygiene, improved rodent and bird control and feeding mash instead of pelleted feed. However, there is little scientific evidence to show that these steps are actually effective in reducing the prevalence of salmonella on pig farms.
The best way to ensure salmonella is not spread from pigs to people is to handle and cook pork products properly. People working with pigs can avoid becoming infected with salmonella through direct contact with pigs by frequently washing their hands, especially before eating or touching their face.
Leptospirosis
Leptospirosis is a disease caused by a family of spiral-shaped bacteria called leptospires. Most mammals are susceptible to leptospirosis. The bacteria are shed in the urine of infected animals and they can survive for long periods in the environment under warm, moist conditions. If the bacteria enter a pig barn, the disease can spread easily because of the close contact between pigs and the warm, wet conditions found in swine barns.
People and animals can become infected by ingesting (eating) the bacteria. Leptospires also have the ability to penetrate broken skin and the membranes of the eyes, nose and mouth.
What happens to pigs? Many infected pigs show no sign of illness. Often, the only indication that pigs are infected with leptospires occurs when white spots are found on the kidneys at the abattoir. These spots are the result of damage that the bacteria do to the kidneys. Occasionally, infected pigs develop fever, lack of appetite, jaundice or seizures. Infected sows and gilts may show reproductive failure including poor conception rate, abortion, lots of stillbirths, mummies or weakborn piglets. Affected sows may become very thin.
What happens to people? People who come into contact with pig urine and kidneys, such as pig farmers, veterinarians, meat inspectors and abattoir workers, are the ones most likely to be infected with leptospires.
Many infected people do not develop any symptoms. Others develop a mild, flu-like illness that includes headaches, nausea and vomiting, muscle aches and fatigue. In severe cases, the bacteria can cause damage to the brain, liver and kidneys. These people must be hospitalized and the effects of the infection can produce chronic health problems including the need for long-term kidney dialysis. Leptospirosis can also result in death, although this is extremely rare.
What can be done to prevent it? Several steps can be taken to minimize the risk of a pig herd becoming infected, which will reduce the risk of people being exposed to the bacteria. Pigs should not have access to untreated surface water (such as ponds) as the urine of infected wildlife drinking from the pond contaminates the water. A good rodent control program should be in place to reduce the numbers of infected rodents in the barn. Commercial vaccines, often given to sows and gilts, will reduce the prevalence of infection and minimize the shedding of the bacteria by infected animals.
People working around pigs should have easy access to clean, running water, soap and clean towels so they can wash and dry their hands frequently. If a worker is splashed by urine or liquid manure, the skin should be washed, especially if the splashing occurs to the face or to an open wound.
People assisting sows during farrowing should wear protective gloves. People using pressure washers should wear waterproof clothing to prevent becoming soaked with the splash-back of potentially-contaminated water. All cuts and scrapes should be covered and kept dry when working around pigs and any wounds that occur when working in a barn or abattoir should be washed and covered.
Yersiniosis and Campylobacteriosis
Yersiniosis is a disease caused by infection with bacteria of the yersinia family. In North America, most cases of yersiniosis are caused by yersinia enterocolitica. It is related to yersinia pestis, the bacteria that causes the plague. Contaminated pork is the most common source of yersinia infection in people.
Campylobacteriosis is also a bacterial disease, caused by members of the campylobacter family. Campylobacteriosis is most often associated with consuming contaminated poultry meat, but pork can occasionally be a source of infection for people. Both yersiniosis and campylobacteriosis can also be contracted through drinking contaminated water.
What happens to pigs? Pigs are asymptomatic carriers of both yersinia and campylobacter bacteria. In other words, although they may be infected with these bacteria, pigs don't show any signs of illness. Many years ago, it was believed that swine ileitis (porcine proliferative enteropathy) was caused by campylobacter bacteria. It is now known that another bacteria, Lawsonia intracellularis, causes this disease but some people still incorrectly refer to ileitis as "campylobacter."
What happens to people? Both illnesses produce fever, stomach cramps, nausea, vomiting and diarrhea. Both diseases occasionally cause joint pain and arthritis that can persist for months after the initial infection. Some people with yersiniosis develop a skin rash that lasts for about a month.
On rare occasions, people affected by campylobacteriosis develop a condition called Guillain-Barré syndrome. This condition affects the nervous system, resulting in paralysis that requires hospitalization. Many people fully recover from Guillain-Barré syndrome, but months of rehabilitative therapy are needed.
Sometimes, people who cut themselves while handling pigs or pork develop abscesses or blood infections as a result of yersinia infection. These can be severe, requiring antibiotic treatment and hospitalization.
What can be done to prevent them spreading? These bacteria are part of the normal intestinal bacterial population in the intestines of pigs, so it is extremely difficult to eliminate them from pig farms. To avoid becoming infected or infecting others, people working with pigs should always thoroughly wash their hands before eating, touching their face or leaving the barn. Those who get cuts or scrapes while working with pigs or pork should thoroughly wash, dry and cover the wound to reduce the risk of the injury becoming infected with yersinia.
People can become infected with these bacteria if they consume improperly cooked, contaminated pork or other foods that have come in contact with contaminated raw pork. Proper food handling practices will reduce the risk of becoming infected with these bacteria. BP
Beth Young is a swine extension veterinarian at the University of Missouri and Cate Dewey is a professor in the Department of Population Medicine, Ontario Veterinary College, University of Guelph.