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AHVLA: Swine Dysentery Diagnosed in Bury St Edmunds

13 December 2012


UK - A case of swine dysentery was diagnosed at Bury St Edmunds when a faecal sample was submitted from group of six three-month-old rare breed pigs purchased at six to eight weeks of age for fattening, according to AHVLA's Disease Surveillance Report for September 2012.

Enteric Diseases

Swine dysentery diagnosed in small groups of pigs purchased for fattening

On arrival, one pig was unwell and the whole group subsequently developed diarrhoea, occasionally with blood and wasting. The remaining pigs responded to treatment. The attending vet was provided with advice on swine dysentery control and biosecurity, and informed of the Swine Dysentery Producer Charter. Minimum Inhibitory Concentration testing showed that the Brachyspira hyodysenteriae isolated from the farm was sensitive to tiamulin. Six healthy pigs kept previously on the site were sent to slaughter prior to the weaners arriving and it was suspected that infection arrived with the new group of pigs.

In a similar situation, a group of six Saddleback weaners bought in three weeks earlier developed haemorrhagic diarrhoea, inappetence and poor growth and Brachyspira hyodysenteriae was isolated from a pooled faecal sample submitted to Langford, confirming a diagnosis of swine dysentery. These diagnoses are of concern because swine dysentery is one of the diseases targeted for control by the Pig Health Improvement Project. It is important to raise awareness on small units like this of the potentially serious impact of the disease on commercial units. Information about swine dysentery is available on the BPEX website:

Coccidiosis and salmonellosis causing deaths and diarrhoea in replacement gilts

Concurrent salmonellosis and coccidiosis was diagnosed as the cause of weight loss reported in eight of 33 six-month-old replacement gilts, two of which died in the 24 hours prior to submission of a dead gilt. One thin pig was found dead, the submitted pig was found inappetent, weak and recumbent and died an hour prior to submission. The gilts had arrived on the unit six weeks earlier and were initially housed for four weeks then moved to outdoor training paddocks. This gilt was dehydrated with diarrhoea and severe enteritis (see Figure) due to dual infection with Eimeria coccidial species and Salmonella infection. Histopathology supported these diagnoses and did not reveal evidence of involvement of PCV-2 associated disease. The fact that training paddocks had been used on a continuous basis for at least six years was considered likely to have predisposed to disease by exposing new naïve gilts to a heavy challenge on entry to the paddocks. This clinical scenario has been reported in previous AHVLA submissions of replacement breeding stock. There was also a significant pneumonia associated with Pasteurella multocida infection, this was chronic and the possibility of earlier viral involvement (principally swine influenza) could not be ruled out. To investigate this possibility in new batches of replacement gilts on the unit, submission of nasal swabs for swine influenza virus detection from gilts showing respiratory disease was suggested, sampling early in the course of disease.

Systemic and Miscellaneous Diseases

Porcine circovirus-2 associated respiratory disease in unvaccinated growers

Porcine circovirus-2 associated disease (PCVAD) was implicated in an outbreak of respiratory disease in a herd repopulated eight months previously. Twenty of 250 seven-week-old unvaccinated pigs showed respiratory signs and two died. Examination of two euthanased pigs at Luddington revealed moderate granulomatous bronchointerstitial pneumonia and granulomatous lymphadenitis, immunohistochemistry for PCV-2 confirmed the diagnosis. PCV2 vaccination has been implemented.

PCVAD was also diagnosed by Penrith as the cause of dyspnoea and death of three of a group of nine twomonth- old pigs. A pig was submitted with circular, 3-4 cm diameter areas of raised, dark, encrusted skin over the dorsal body sides and face. The underlying dermis was reddened but not ulcerating. The lungs were markedly oedematous but not consolidated, there was pleural oedema. Histopathology revealed an interstitial pneumonia with lymphoid depletion associated with abundant PCV-2 antigen. The exfoliative dermatitis was considered to be secondary to the PCV-2 induced immunosuppression.

Rapid deaths in pigs due to bracken poisoning

A group of 36 fattening pigs of mixed rare breeds had access to a small hillside carpeted in bracken with minimal access to grass. Supplementary weaner pellets were fed daily. Six pigs died over a period of three weeks; three were found dead and three showed signs of respiratory distress for 24 hours before death. At the time of these deaths almost all the bracken had been grazed from the hillside and bracken roots/rhizomes had been exposed. Both bracken fern and the rhizomes are known to be toxic although pigs are considered to be more resistant than some other species. Postmortem findings at Penrith of lung oedema and pleural effusion were consistent with cardiac failure and histopathological examination revealed a cardiomyopathy similar to that reported in experimental cases of bracken poisoning in pigs. This case was reported as a potential food safety incident and advice was given to protect the food chain, regarding access to bracken and the provision of extra supplementary feed. As a result of this, and subsequent AHVLA diagnoses of bracken poisoning in pigs, an alert was sent out to raise awareness of the risk of bracken toxicity to pigs.

Further Reading

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