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Disinfection Problems Blamed for Salmonella Losses

by 5m Editor
24 March 2009, at 8:57am

UK - The Monthly Surveillance Report from the Veterinary Laboratories Agency (VLA) for January 2009 highlights Salmonella typhimurium U288 causing losses in growing pigs. The cases reported underline the difficulty in disinfecting premises adequately and the involvement of PCV-2 infection in many outbreaks.

Alimentary Tract Diseases

Clostridial enteritis

The carcasses of seven piglets aged between 2-and-3-days were submitted as part of an investigation into increased mortality affecting litters on a unit with 250 breeding sows. Post mortem examination showed the presence of milk clot within the stomach together with liquid yellow blood-stained small intestinal content. One of the piglets showed evidence of subcutaneous haemorrhages and oedema and two of the piglets showed the presence of ruptured livers with free blood within the abdomen. Clostridium perfringens toxin ELISA testing of intestinal content confirmed the presence of alpha and epsilon toxins in one of three samples tested confirming the presence of either type B or type D Clostridium perfringens enterotoxaemia.

A flare-up of scour affecting 25 per cent of neonatal piglets with 10 per cent mortality on a 1500-sow breeder finisher unit, prompted the submission of three live one-day-old piglets to Thirsk for investigation. The farm had recently begun a vaccination policy using a multivalent clostridial vaccine but the vaccine would not have yet had a chance to totally cover the herd. Post-mortem examination revealed yellow bubbly intestinal content along the entire length of the intestines and Clostridium perfringens was cultured from the faeces of each piglet. Alpha toxin was detectable in the small intestinal contents of one piglet confirming the diagnosis of Clostridial enteritis.

Salmonellosis

Bury investigated a case in which forty out of 230 five-week-old pigs were affected with diarrhoea, wasting with 30 deaths. On farm post mortem examination revealed diphtheritic colitis and Salmonella Typhimurium U288 was isolated from two specimens of colon submitted for post-mortem examination. Despite efforts to improve cleaning and disinfection between batches, subsequent weaned pigs suffered a similar problem and pigs submitted for post mortem examination at five to six-weeks-old were in poor body condition with enteric colibacillosis and, in some, salmonellosis. A post cleaning and disinfection visit was made to the unit and high levels of residual salmonella were cultured from swabs of the floor and feeders of cleaned and disinfected flat decks although visually a good standard of cleanliness had been achieved. Advice was given on improving efficacy of disinfection and preventing recontamination of disinfected areas.

Sutton Bonnington also investigated a case involving the same organism. Six, 14-week-old pigs, were submitted for necropsy from a finisher unit. Four of the pigs were from one breeder unit. Animals from this unit had been lethargic, and exhibited lameness, swollen joints and poor weight gain. An animal necropsied on-farm had lesions suggestive of a polyserositis. The other two pigs were from a different breeder unit and were described as 'poor doers'. In all six animals at necropsy, there was a variably severe necrotising and ulcerative colitis often with a diphtheritic membrane. Salmonella Typhimurium phage type U288 was cultured from pooled faecal samples of both groups of pigs. In addition, Brachyspira pilosicoli was cultured from the large intestines but the severity of the colitis was more consistent with salmonellosis. Changes associated with PCV-2 were demonstrated in the two piglets exhibiting wasting indicating the presence of concurrent PMWS.

Swine dysentery

Langford remarked that practitioners were reporting an increase in swine dysentery. They investigated a case with a history of fattening pigs showing wasting and diarrhoea. FAT tests on a faecal sample were positive for Brachyspira. B. hyodysenteriae was isolated using specific culture, confirming the diagnosis of swine dysentery

Respiratory Diseases

Influenza

Rapidly spreading coughing on a large continuous nursery finisher unit with a total of 11,000 pigs began on New Year's Eve and prompted submission of a dead pig to Bury to investigate possible swine influenza. In the rearing shed that was worst affected, approximately 700 of 3,500 pigs were coughing and although most affected pigs appeared bright there were with five deaths in the space of two days. Pigs had been vaccinated for Mycoplasma hyopneumoniae and PCV-2 at weaning. The pig submitted for necropsy had a severe fibrinopurulent tracheitis with a significant bronchopneumonia and unilateral fibrinous pleurisy from which Pasteurella multocida and Streptococcus suis type 2 were isolated. Swine influenza was confirmed by isolation of H1N2 influenza virus and immunohistochemistry. The virus isolated is being compared to the H1N2 virus also isolated in East Anglia from an outbreak of swine influenza on a breeding unit described in November's monthly surveillance report.

PRRSV

Bury diagnosed PRRSV-associated respiratory disease in outdoor weaned pigs. Over a period of six to eight weeks, dyspnoea and coughing were noticed in each batch of weaners from four weeks of age after moving to outdoor nursery finisher sites. In one batch, 25 per cent of pigs became affected with 7 per cent mortality over three weeks. In a batch of 1000 four-week-old pigs, 30 were reported to be affected on arrival. Pigs were outdoors in tents with paddocks with no mixing of sources or ages.

Neurological Diseases

Streptococcal meningitis

Winchester investigated Increasing mortality in 12-week-old pigs that had demonstrated neurological signs. Two pigs submitted for post mortem examination demonstrated meningeal congestion and a fibrino-purulent meningitis. Streptococcus suis Type 2 was isolated from the meninges.

In another case, piglets aged 10 to 14 days that were reportedly 'going off their legs' and showing vague neurological signs were submitted for post mortem examination. There was a suppurative poly-arthritis, with fibrino-purulent deposits over the brain and abdominal viscera. On this occasion Streptococcus suis Type 1 was isolated.

Sutton Bonnington received a twelve-week-old piglet from a small unit that breeds and finishes pigs that had a history of anorexia, walking in circles and eventual recumbency. At necropsy, a heavy infestation of Haematopinus lice was present, along with a polyserositis affecting the right hock, left elbow and peritoneum. Streptococcus suis type II was cultured from the affected joints.

Further Reading

- You can view the full report by clicking here.

Further Reading

- Find out more information on the diseases mentioned in this article by clicking here.

5m Editor