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VLA: Three Different Viruses Found in Flu Outbreaks

by 5m Editor
15 January 2010, at 9:02am

UK - Three outbreaks of swine influenza (caused by 'human' H1N1, 'avian' H1N1 and H1N2 viruses) are reported in the VLA Monthly Scanning Surveillance Report for November.

Alimentary Tract Diseases

Swine dysentery

Low level scour which, at its worst, only affected three pigs in a pen of 50 indoor finishing pigs was investigated by Bury. A 15-week-old pig that had received in-feed lincomycin on the day of submission and the previous week was euthanased for necropsy. The pig had khaki-coloured diarrhoea with no blood or mucus present and in the spiral colon there were multiple 1 to 2 mm diameter mucosal ulcers overlain with yellow diphtheresis. Spirochaetes were present on histological examination of the colon and Brachyspira hyodysenteriae was detected by PCR, confirming a diagnosis of swine dysentery. This finisher site was supplied by a breeding unit repopulated four years ago and this is the first evidence of swine dysentery. The source of infection is not yet known and further investigation is planned.

Salmonellosis

Salmonellosis due to Salmonella Typhimurium phage type U288 was identified by Bury as the cause of scour and deaths in eight-week-old pigs in flat decks where approximately 10 per cent were affected and eight had died out of the batch of 240 pigs. The unit involved has had ongoing salmonella problems over the past few years and advisory visits have been made to the unit. Both pigs submitted had evidence of enterocolitis, which was necrotic in one pig.

Respiratory Diseases

Swine influenza

Three outbreaks of swine influenza were diagnosed by Bury involving three different influenza strains. Although outbreaks of influenza can occur throughout the year, they usually peak in the colder months and outbreaks of swine influenza at this time of year in 2008 were seen.

An outbreak of human pandemic H1N1 2009 influenza infection was diagnosed. Affected breeding sows and gilts showed loss of appetite and lethargy of one to four days duration, with very few exhibiting respiratory signs. All pigs recovered fully other than one sow that was sacrificed for diagnostic purposes. In-feed antibiotic treatment was given.

An outbreak of swine influenza due to strain H1N2 was diagnosed in October as the cause of a marked increase in coughing in all age groups over a week on an indoor breeder-finisher unit, where signs were most prominent in pigs up to 30kg. Morbidity was high and mortality low, reaching one to two per cent in younger pigs.

Avian-like H1N1 influenza virus was diagnosed as the cause of lethargy and coughing in 75 per cent of 2,000 pigs on an indoor nursery-finisher unit supplied by two sources. Disease occurred in nine-week-old pigs and began in one shed and spread to the second. Histopathology revealed a bronchiolitis in the three submitted pigs, strongly suggestive of swine influenza infection which was confirmed by isolation of the virus. No involvement of PRRSV was identified.

Metastrongylus

Winchester necropsied a weaner gilt that had been purchased approximately three weeks previously. It was in a group showing noticeable variation in size with coughing and diarrhoea. Post-mortem revealed patchy, firm, long-standing consolidation and collapse affecting approximately 40 per cent of the total lung area. Histologically, the lesions noted in the lung were considered to be consistent with a heavy nematode burden and the presence of embryonated eggs was suggestive of infection with Metastrongylus sp.

Other diseases

Erysipelas

Several pigs were presented to a practitioner with signs of cyanosis, respiratory distress and a history of erysipelas. Post mortem examination carried out on the farm revealed endocarditis, and a sample of the bacterial growth from the heart valve was forwarded to VLA Thirsk for identification. Erysipelothrix rhusiopathiae was cultured from the heart valve confirming endocarditis caused by erysipelas.

Neurological Diseases

Streptococcus suis

Streptococcus suis type 14 infection was implicated in disease affecting approximately 21 pigs from which seven died in a group of 1,400 six-week-old housed weaners on an indoor nursery-finisher unit. The problem began two days after arrival at four weeks old with paddling, recumbency, sudden death and lameness. Clinical signs responded well to penicillin treatment. One dead pig submitted to Bury was septicaemic and had a polyarthritis from which Streptococcus suis type 14 was isolated in pure and profuse growth. PRRSV was not identified by PCR and no swine influenza virus was isolated.

Three piglets were submitted to Thirsk from a nursery unit where seven-week-old pigs were affected with signs of meningitis, joint-ill and respiratory illness. At the time of the submission approximately 128 from 1,200 had been affected with eight deaths. The post mortem investigation revealed fibrinopurulent material in joints, fibrin overlying the meninges and pulmonary consolidation. Streptococcus suis type 14 was isolated from joint swabs, pericardium, lung and brain. Lung and trachea submitted for influenza virus isolation revealed Avian-like H1 influenza, similar to A/sw/Eng/195852/92 (this is not the human pandemic H1N1v09 strain). The results confirmed Streptococcus suis joint-ill, meningitis and septicaemia. The isolated flu virus is typical of a number of isolates that are detected on a seasonal basis and that are endemic in the UK pig herd. It is likely that the flu virus triggered the Streptococcus suis septicaemia and contributed to the severity of the clinical signs.

Further Reading

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