Alimentary tract diseases

Rotaviral enteritis

Thirsk necropsied three 1-day-old pigs which had a history of severe diarrhoea. Post mortem examination revealed generalised reddening of the small intestine and pasty yellow faeces. Rotavirus was detected in two of the three pigs and histopathology confirmed mild villus atrophy and reactive crypt hyperplasia in these two pigs , suggestive of viral enteritis.

Bury also identified rotavirus as the cause of diarrhoea in seven of 32 three to seven-day-old piglets on a large indoor breeding unit. Rotavirus was detected by PAGE in faeces from two typically affected piglets with yellow pasty to fluid faeces.

Salmonellosis

Thirsk isolated Salmonella Typhimurium var Copenhagen phage type 120 from four-week-old piglets that showed acute post weaning fading and scouring. Histological examination revealed moderate severely, subacute ulcerative and necrotising colitis.

Bury isolated Salmonella Typhimurium phage type 193, a PT often associated with the monophasic S. Typhimurium variants, from a group of seven-monthold gilts on an outdoor unit. The gilts had presented with profuse khaki green diarrhoea and slight malaise. The unit was newly established on ground on which pigs had not previously been kept and it is possible that infection entered with new stock. Clinical disease has resolved.

Swine dysentery

Shrewsbury diagnosed swine dysentery as the cause of extensive wasting and diarrhoea in growing pigs. The farm system was reported to be extensive with piglets and sows having the run of the farm, including access to outdoor paddocks. No routine vaccinations were carried out and there had been no recent introductions to the herd in the past 12 months. Post-mortem examination revealed colitis and Brachyspira hyodysenteriae was isolated, consistent with a diagnosis of swine dysentery.

Respiratory Diseases

Swine Influenza

Thirsk diagnosed swine influenza as the cause of abortion in sows and pneumonia in 13 wk growing pigs on a farrow-to-finish unit. The diagnosis was confirmed by immunohistochemistry on lung tissue following the identification of Influenza A RNA by PCR in pooled respiratory tissues taken at necropsy.

Bury also diagnosed the disease as the cause of coughing in 90 per cent of nine-week- old pigs on an outdoor nursery unit with <1 per cent mortality. Swine influenza virus was detected by PCR in nasal swabs collected from acutely affected pigs. Neither case was associated with pandemic H1N1 2009.

In another case the condition was suspected but not confirmed as the cause of widespread coughing in 70 per cent of 800 seven-week-old pigs on an indoor nursery finisher from which four had died. Pigs had arrived coughing at four-weeks old from the breeding unit. Limited diagnostic material was received.

Neurological Diseases

Congenital tremor

Thirsk diagnosed congenital tremor type A2 as the cause of ataxia, tremor and a very unsteady gait affecting piglets from two sows in a small herd of Berkshire pigs. The two affected second parity sows had been on another farm for service and had only recently returned. Gross post mortem findings were unremarkable in the affected piglets but histopathology, including a luxol fast blue preparation, revealed deficiency in stainable myelin in the spinal cord of the affected piglet, confirming a diagnosis of congenital tremor A2 which is thought to be associated with in utero infection with an as yet unidentified virus. Mixing with pigs on the other farm may have been the source of infection. Type A1 tremor associated with classical swine fever was ruled out on clinical and histopathological grounds.

Streptococcal meningitis

Three sudden deaths and two pigs with nervous signs in a group of 50 growing pigs on an outdoor organic finishing unit, were investigated by Bury. Three dead pigs were necropsied revealing necrotic enterocolitis caused by Salmonella Typhimurium phage type U288 in one pig and pneumonia and polyarthritis caused by Pasteurella multocida and Streptococcus suis type 7 in thesecond. The third pig had gross lesions consistent with septicaemia/meningitis; Streptococcus suis type 2 was isolated from the meninges confirming streptococcal meningitis. The mixed findings were suggestive of underlying viral disease; however, testing provided no evidence of involvement of PCV-2 associated disease, PRRS or swine influenza.

Further Reading

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