Swine dysentery causes important financial losses because of reduced feed efficiency and lower weightgain, costs of medication and additional animal care, and death. Substantial costs may result from loss of sales of breeding stock, or depopulation when necessary. Serpula (Treponema) hyodysenteriae, a spiral bacterium, is the cause of swine dysentery, and seven different types have been recognized worldwide.

The bacteria is spread through faeces of infected animals on the farm. It is extremely cold resistant (it can survive under the temperature which is below 10 ºС): its habitat is lagoons with manure and water, where it lives for approximately two months. But it can stand the temperature +25 ºС for less than a week when it is humid and less than two days when it is dry. It can stand the temperature -70 ºС for the same time.

Pigs of all ages are susceptible to swine dysentery, but the disease is most frequently seen in feeder pigs 8 to 14 weeks old. The incubation period for swine dysentery is highly variable and can range between 10 to 30 days. The acute form of the disease is characterized by severe and often fatal bloody diarrhea.

Introduction and Maintenance of Swine Dysentery on the Farm

An important aspect of the disease is that pigs can continue to transmit swine dysentery even after they recover from diarrhea because they continue to "shed" the S. hyodysenteriae in their feces. These carrier-shedder pigs are the major source of the disease on infected farms, and also transmit it to noninfected farms. Once introduced onto a farm, S. hyodysenteriae quickly becomes established in the swine herd, the environment (especially waste collection systems), and the resident rodent populations.

Shedding of S. hyodysenteriae in the feces of birds, dogs and mice makes these species potential vectors of swine dysentery among herds.

Several factors determine the extent and severity of swine dysentery in a swine herd. These factors are similar for many disease agents affecting swine raised under intensive production practices and broadly include:

1. the dose and virulence of the agent;

2. the degree of stressors imposed on the animals;

3. the level of immunity in the population at risk;

4. and the effectiveness of the control measures used once an outbreak occurs.

The dose of S. hyodysenteriae to which pigs are exposed depends on the degree of environmental

contamination, which in turn is directly related to swine population density, level of hygiene,

segregation of sick and poor-doing animals, and effectiveness of the medication strategy. Very little is known about the relative virulence of individual strains of S. hyodysenteriae. Environmental stressors decrease the resistance of pigs to diseases, causing recurrence of diarrhea in carrier pigs, and poor response to treatment in sick animals.

Clinical Signs

The main symptom of dysentery is diarrhea and the anus area is mudded with faeces .

Affected pigs may be wobbly in the hindquarters and show evidence of abdominal pain, such as

stretching and kicking at the belly. The feces may be red, resembling tomato ketchup, or may have a black, tarry appearance. Death usually results from dehydration caused by severe diarrhea. In herds where the disease has become well-established, the only signs affected pigs may exhibit are lower weight gain and reduced feed efficiency.

1. What are the peculiarities of swine dysentery diagnosis?
2. What diseases is SD confused with most frequently?
3. What factors should be considered when making a decision to control or eradicate the disease?
4.  What is the best way to protect healthy animals and treat sick animals?
5. What are the main rules of effective disinfection?
6.  What are the main rules of eradication?
7.  What are the cases when depopulation is the only decision that can be made?

You can find answers for these and other questions in the full version of the article in the magazine “Profitable Pig Production”, 1 2013.