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Mulberry Heart, Flu Caused Mortalities in Weaners

16 August 2012, at 8:02am

UK - The AHVLA Surveillance Monthly Report for May 2012 records cases of unusual vomiting, salmonellosis and mulberry heart disease have been reported in piglets across the UK.

Alimentary Disease

Unusual vomiting in gilt litters with rotaviral enteritis

An interesting case of rotaviral enteritis was diagnosed by Thirsk in preweaned pigs. The farmer reported vomiting as the first clinical sign followed within six to twelve hours by diarrhoea. The problem was mainly seen in gilt litters and mortality in the farrowing house had crept up from approximately 7% to 11%. Due to the unusual and predominant sign of vomiting, a farm visit was undertaken and samples collected and tested for transmissible gastroenteritis and porcine epidemic diarrhoea (TGE and PED); neither were detected. However rotavirus was detected in multiple samples. The husbandry was of a very high standard, and improving on the hygiene measures was considered to be difficult. It was suggested that gilts should be mixed with younger smaller sows prior to farrowing to try and stimulate immunity to be transferred to piglets in colostrum.

Salmonellosis following treatment for respiratory disease

An outbreak of salmonellosis was diagnosed in seven-week-old pigs following treatment for respiratory disease seen as coughing on entry to the unit. A week afterwards the pigs began to scour and lose weight and Salmonella Typhimurium phage type U288 was isolated by direct culture from submitted faeces. The salmonella isolated was resistant to the antimicrobial used to treat the respiratory disease and this is likely to have contributed to the development of the salmonellosis. Advice was given to reduce the risk of zoonotic infection with salmonella.

E.coli scour in neonatal pigs

The carcases of four neonatal piglets were submitted to Winchester as part of an investigation into diarrhoea and mortality in outdoor bred piglets. There was evidence of recent feeding with milk clot present within the stomach. Small intestinal content in all examined pigs was liquid and pale yellow with purple congestion of the serosa of the large intestine and blood-stained content. Heavy pure growths of K88 antigen-positive haemolytic E.coli were obtained on intestinal culture. This isolate was serotyped as E.coli 0141:K85ac, K88ac. No other enteropathogens were detected. The farm had previously practised E.coli vaccination but had ceased vaccinating recently.

Respiratory Disease

Mulberry heart disease with swine influenza

Swine influenza involving strain H1N2 virus was detected in five-week-old pigs dying due to likely Mulberry heart disease. The pigs were kept in tents of 100 outdoors and in the two days prior to submission seven of 1,500 pigs in good body condition had died suddenly. Straw-coloured clear fluid was present in excess in the pleural and peritoneal cavities with fibrin stranding, hearts showed dark red discolouration and histopathology was consistent with Mulberry heart disease. It is recognised that infections such as swine influenza in young pigs, increase the demand for free radicals and predispose affected pigs to Mulberry heart disease. However, whilst bacterial and other viral infections are commonly found concurrent with swine influenza virus infection, Mulberry heart disease together with swine influenza is a less common combination of diagnoses made by AHVLA.

Multiple infections involved in respiratory disease in growers

Swine influenza (strain H1N2), PRRS virus and Streptococcus suis type 14 were all detected in plucks submitted to Thirsk to investigate clinical respiratory disease affecting 10% of grower pigs on a 400-sow farrow to finish unit. Post-mortem examination revealed multifocal grey and purple consolidation with some wedge shaped purple areas in caudodorsal lung regions. This case illustrates how important it is to undertake full diagnostic investigation of respiratory disease cases to provide information to assist control.

Systemic and Miscellaneous Diseases

Disease tentatively attributed to in utero Mycoplasma suis infection in neonatal pigs:

Mycoplasma suis was detected in blood from neonatal pigs by microscopy and DGGE/PCR, and was confirmed by sequencing of the PCR product during an investigation into stillbirths and recumbent piglets on an indoor weaner-producer unit. Approximately 12% of litters from any parity of sow were affected each week and a concurrent increase in diarrhoea in two to three-day-old pigs was reported. There had been periodic surges of this presentation on the unit and the incidence had increased in the two weeks prior to submission. No other significant health problems were reported on the unit and no increase in sow mortality. Once pigs reached around two weeks old, they grew well and wean at a good weight. No diagnosis was established for weakness in live piglets and stillbirths submitted, nor for the diarrhoea in two older pigs from the unit which had moderate to good colostral antibody. The two live weak piglets and one of the diarrhoeic piglets had a regenerative anaemia and M. suis was detected by PCR. Histopathology on bone marrow suggested an erythroid regenerative response which supported the anaemia being due to M. suis and did not suggest bone marrow suppression or iron deficiency anaemia. However, interpreting histopathological findings in neonatal bone marrow is problematic without bone marrow from age-matched haematologically normal piglets. Clinical disease due to M. suis reportedly is often associated with outbreaks of other infectious diseases in the herd. There was no evidence that PRRS was underlying disease but active swine influenza infection is known to be present on the unit and vaccination is being considered. Given the findings, improvements were made in hygiene; in particular, more frequent changes of needles during sow vaccinations. Clinical disease subsided; however, further investigation is planned if there is an upsurge of similar disease on this unit, to include blood sampling sows of affected and unaffected litters and, if possible, examination of age-matched healthy nonanaemic pigs. In utero transmission of M. suis is reported in the literature (Henderson et al, 1997, Veterinary Record 140:6 144-146) and tetracycline treatment can be used for treatment but does not eliminate the organism.

Further Reading

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