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AHVLA Scanning Surveillance Report - August 2011

by 5m Editor
21 October 2011, at 10:05am

UK - Weight loss and diarrhoea was reported in a group of eleven 12- to 14-week-old pigs in a rare breed herd, which was suggestive of PCV2-associated disease.

Reproductive Diseases

Streptococcal abortions

A problem of two to three late abortions or early farrowings in each farrowing batch of 140 sows over several months on an outdoor unit was investigated by submission of foetuses from one aborted litter. Streptococcus dysgalactiae subspecies equisimilis was isolated from foetal stomach contents of all foetuses in pure growth and no other infectious causes of abortion were identified. The consistent isolation of this streptococcus in pure growth makes it likely that this was significant in this abortion. Further submissions from the herd would establish if this was just a sporadic case.

Alimentary Diseases

PCV2 associated enteric disease

Weight loss and diarrhoea was reported in a group of eleven 12 to14-week-old pigs in a rare breed herd. Intestinal samples were submitted from an on-farm necropsy and histology revealed a marked hyperplastic granulomatous and lymphoplasmacytic enterocolitis strongly suggestive of PCV-2 associated disease which was confirmed by detection of PCV2 by immunohistochemistry. No other enteropathogens were detected. This is a recognized manifestation of PCVAD.

Swine dysentery causing signs in a lactating sow

Swine dysentery was diagnosed on a large breeder-finisher unit where diarrhoea was reported in a lactating sow. Brachyspira hyodysenteriae was isolated confirming the diagnosis.

Late deaths due to porcine intestinal adenomatosis

A fattening herd experienced three deaths in a group of 300 pigs approaching finishing age. A pig, which collapsed while being loaded for slaughter, was submitted for investigation. Necropsy revealed evidence of a severe chronic proliferative and haemorrhagic enteropathy. Organisms resembling Lawsonia intracellularis were seen in stained smears of the ileum. The diagnosis of porcine intestinal adenomatosis was confirmed by histopathology and positive PCR.

Sudden deaths due to E. coli enteritis

Two-week-old piglets were submitted to investigate a few sudden deaths at two to three weeks-old. Post-mortem examination revealed markedly reddened small intestines with red watery mucoid contents. E. coli serotype O149: K91, F4ac (Abbotstown) was isolated in pure, profuse culture from intestinal contents. This E. coli strain is mainly associated with diarrhoea in neonatal and postweaned pigs. The sows were vaccinated against E. coli; ensuring adequate colostrum intake in all piglets to maximise the benefit of sow vaccination and good farrowing house hygiene are important control measures.

Respiratory Diseases

Actinobacillus pleuropneumoniae in finishers

Actinobacillus pleuropneumoniae in finishers Disease due to Actinobacillus pleuropneumoniae was diagnosed as the cause of coughing and mortality in 10 per cent of 1,600 18-week-old pigs from which seven had died on an indoor nursery finisher unit. There were typical circumscribed lesions with consolidation and, on the cut surface, a necrotic appearance and interlobular pulmonary oedema. No evidence of underlying viral infection was detected. On a second unit, sudden deaths were reported in 20-week-old pigs with no prior clinical signs. Post-mortem examinations revealed extensive pneumonia affecting all lung lobes, fibrinous pleurisy and low grade pericarditis, and Actinobacillus pleuropneumoniae and Streptococcus suis serotype 7 were isolated from affected lungs.

Rapidly spreading respiratory disease in swine influenza outbreaks

Swine influenza due to non-pandemic influenza strains was diagnosed on several occasions following detection of virus in nasal swabs tested free under AHVLA’s swine influenza surveillance project. Most outbreaks had typical histories of acute rapidly spreading respiratory disease. One typical example was diagnosed in 26-day-old housed pigs on a nursery finisher unit on which approximately 10 per cent of 600 pigs were showing acute coughing and sneezing; at the time of submission no deaths had occurred.

Another outbreak of swine influenza infection occurred in five-week-old pigs which had been coughing and sneezing with nasal discharges over a two-day period prior to sampling. Approximately 15 per cent of 900 pigs were affected on an outdoor nursery unit; none had died at the time of submission.

In another outbreak, almost all of 20 16-week-old gilts were coughing severely on an outdoor breeding unit and two died. On-farm post mortem examination of one of these revealed a polyserositis, indicating likely secondary bacterial infection and accounting for the mortality.

Likely Glasser’s disease superimposed on active swine influenza infection was the cause of sudden death of 13 six-to-seven-week-old pigs from a group of 1,200, 70 of which appeared dull and lethargic and the rest of which were coughing for several days prior to the deaths. There was a generalised ‘bread and butter’ fibrinous pleurisy and pericarditis, typical of Glasser’s disease due to Haemophilus parasuis. The degree of autolysis and post mortem contamination of the tissues meant that no organisms of clinical significance were isolated; however, swine influenza virus was detected by PCR.

PRRS underlying ongoing respiratory disease problems

PRRSV detected on three units was considered likely to be significant in ongoing disease problems. In the first of these, three live finishing pigs were submitted from a continuous throughput indoor nursery-finisher unit to investigate the cause of chronic cough which had affected the previous two batches. Most pigs were described as affected in the batch and, in the previous batch, 24 of 200 pigs died during rear. Both Pasteurella multocida pneumonia and PRRSV infection were identified, and histopathology supported PRRS as the likely underlying cause of the pneumonias.

In the second unit, samples were submitted from on-farm post mortem examinations to investigate wasting, diarrhoea and respiratory disease in 10-to-14-week-old pigs together with recent information from the abattoir that there were high levels of pleurisy in slaughter pigs. There were multiple mixed findings in which PRRS with Pasteurella multocida were contributing to respiratory disease and both Brachyspira pilosicoli and Lawsonia intracellularis were pathogens associated with the scour problem.

In the third case, two live six-week-old weaners were submitted to investigate post weaning wasting with some respiratory disease, on a 300 sow farrow to finish indoor unit, known to be PRRSV positive. Both pigs were hairy and slightly wasted and had pneumonias and pleurisy from which pure growths of Actinobacillus porcinus were obtained in both pigs. Pooled serum from these pigs, and a serum pool from five pen mates, both tested positive for PRRSv RNA. Histopathology supported an underlying PRRS-induced pneumonia with secondary bacterial infection. Actinobacillus porcinus is not considered a serious pathogen in pigs but may have been an opportunist in immunosuppressed pigs in this case. The parity profile had changed recently, with a higher number of gilts in the herd which may have destabilised herd immunity to PRRS.

Systemic & Miscellaneous Diseases

Klebsiella species septicaemias in preweaned outdoor pigs

Two further diagnoses were made of Klebsiella pneumoniae subspecies pneumoniae septicaemia following two outbreaks reported last month. Again, good condition preweaned pigs three to four weeks old were found dead on outdoor breeding units. Deaths were mainly from gilt litters with just one sow litter reported to be affected. Post mortem findings were suggestive of a septicaemia with fibrin stranding in the peritoneal cavities and, in one pig, petechiation over the cortex of both kidneys and the organism was isolated in pure growth from multiple sites. No PRRSv involvement was detected. An investigation is in progress into factors which may be involved in these cases.

Musculoskeletal

Likely hemlock toxicity causing congenital limb defects in piglets

A gilt from a smallholding farrowed 13 piglets, six of which had multiple severe congenital limb contracture/arthrogryposis and were euthanased. The seven others were less severely affected. This gilt was kept in an uncultivated field during pregnancy. A field walk confirmed the presence of hemlock (Conium maculatum). This grows in damp places and open woodlands throughout Britain. The stems are smooth with characteristic purple- red blotches and the fleshy white tap root resembles a parsnip. As far as we are aware the last recorded case of hemlock poisoning in pigs occurred in the Langford area over 25 years ago (Barlow, 2006, Pig Journal, volume 57, 254-258). The control of hemlock is by cutting or digging up and disposing of the plants safely; alternatively a glyphosate herbicide can be used.

Further Reading

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

5m Editor