Swine dysentery is caused by a spirochete called Brachyspira and causes severe inflammation in the large intestine producing bloody and mucous diarrhea.
Alternative names: Brachyspira hyodysenteriae
Swine dysentery is caused by a spirochete called Brachyspira (previously called Serpuline or Treponema hyodysenteriae. This organism causes severe inflammation in the large intestine producing bloody and mucous diarrhea.
The disease is frequent between 12 and 75 kg, but severe cases occur occasionally in sows and their piglets.
B. hyodysenteriae can survive outside the pig up to 112 days, but it dies in 2 days in dry and hot environments. Can be transmitted by birds, flies, fomites and mice.
Dissemination inside the farm is slow. The number of pigs affected increases as the microorganism accumulates in the environment. Recovered pigs rarely suffer from the disease again, however antibodies (IgG and IgA) do not last long. Therefore, the relationship between antibodies level and protection is not good. Some sows might not show any symptom during several months and transmit the disease to their piglets.
The high cost of the disease is associated with mortality (low), morbidity (high), decrease in growth, increase in feed conversion ratio, and the cost of in feed medication.
The incubation period in field cases is normally 7 to 14 days, but it can be up to 60 days. Pigs can initially develop a subclinical carrier state, and afterwards show symptoms if they are under stressing situations or when the diet is changed.
Clinical symptoms in sows are not frequent, unless the disease appears for the first time in the farm.
- May suffer a severe acute dysentery.
- Loose light brown feces with or without blood or mucus.
- Loss of body condition.
- Sows are asymptomatic carriers.
Weaners and growers
First symptoms are:
- Sloppy diarrhea that stains perinneal skin.
- Initially the diarrhea has a light brown color with gel consistency mucus.
- Sunken flanks.
- Partial loss of appetite.
- In some cases sudden death.
As the disease progresses:
- May appear blood in gradually higher amounts which makes feces have a dark and tar like color.
- Pigs rapidly loose appetite and body condition.
- Thin animals with sunken eyes.
Causes / Contributing Factors
- Pigs get infected from the ingestion of contaminated feces.
- The disease is transmitted from carrier pigs (including farrowing sows) who excrete the organism in the feces for a long time.
- It can enter a farm through the introduction of carrier animals.
- Mechanical transmission through infected feces in equipment, feed distribution contaminated trucks, boots and birds.
- May be transmitted through flies, mice, birds and dogs.
- The stress produced when the diet is changed may trigger the disease.
- Bad hygiene and high humidity.
- Crowded conditons.
Based in clinical history, clinical picture, post-mortem examination, laboratory tests on fecal swabs and isolation and identification of B. hyodysenteriae through serological and biochemical tests as well as PCR. In order to identify the spirochete from other spirochetes, the diagnosis tests needed might not always be available due to the fact that they are very specialized.
In the post-mortem examination, lesions are present only in the large intestine.
The disease must be differentiated from colitis caused by other spirochetes, non-specific colitis, porcine proliferative enteritis, proliferative hemorrhagic enteropathy, acute salmonella infections, and important Trichuris infections.
- The following products may be used as treatment: carbadox, ronidazole, dimetridazole, salinomicine, tiamulin, lincomicyn, tylosine, monensine.
- Some B. hyodysenteriae strains have developed resistance to these antibiotics.
- When the first signs of the disease are present, water must be medicated with lincomycin, tiamulin or tylosine during at least 7 days.
- The most affected pigs must be injected with lincomycin, tiamulin or tylosine.
- Medicating the diet only helps preventing the development of clinical disease.
- Hygiene and mice control is of paramount importance to control the transmission, especially when it is planned to eradicate the organism.
- There are two general options to eradicate the disease: depopulate and repopulate with disease free sows, or eradicate the disease without depopulating. Both methods are expensive, and the success percentage is not 100%, mainly with the second option.
- All the replacement animals must originate from a swine dysentery negative farm.