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AHVLA Surveillance Report - July 2012

24 September 2012, at 10:14am

UK - The AHVLA surveillance report for July 2012 highlights illthrift tentatively attributed to mould and/or mycotoxins in feed and straw, Klebsiella species septicaemia outbreaks have re-emerge in East Anglia and outbreaks of acute polyarthritis are due to Streptococcus suis types 1 and 14.

Alimentary Disease

Food refusal causing illthrift tentatively attributed to mould and/or mycotoxins in feed and straw

Ten to 15% of 1100 weaners began to show illthrift and failure to establish normal feeding from a week postweaning on an indoor rearing unit. Two euthanased pigs were submitted to Starcross and salmonellosis was diagnosed with typical colitis lesions in both pigs. Pigs ate better when the feed was changed and the enteric disease was considered likely to be a sequel to the earlier poor food intake. Investigations into the possible reasons for feed refusal were initiated by the attending pig practitioner who reported that trichothecene (T-2) was the only mycotoxin detected in both the feed and visibly mouldy straw. In the absence of an alternative explanation, the food refusal was tentatively attributed to the presence of T-2. Different food and bedding was provided to the next batch of pigs which performed much better, allaying initial concerns that this might be a case of periweaning failure to thrive syndrome. As there can be unequal distribution and ‘hot-spots’ of mycotoxin in feed and bedding, evaluating the significance of concentrations of mycotoxin detected in a single farmer-selected sample can be problematic. There are maximum guidance concentrations for animal feed available for T-2 mycotoxin. These guidance values were not exceeded.

Neonatal diarrhoea due to rotavirus

Rotaviral enteritis was diagnosed as the cause of diarrhoea in piglets two to four-days-old on a large indoor grower-producer farrowing weekly. Litters from all sow parities were reported to be affected with 15 of each weekly batch of 60 litters showing clinical signs with a poor response to antimicrobial treatment. Three live piglets were submitted with distension of the small intestine with yellow clear fluid and liquid creamy large intestinal contents and diarrhoea. Rotavirus was the only enteropathogen detected in all three pigs and histopathology revealed villus atrophy and crypt hyperplasia which, in the absence of significant bacterial protozoal involvement, was consistent with rotaviral enteritis. Serum zinc sulphate turbidity (ZST) concentrations were indicative of adequate colostral intake making attention to farrowing house hygiene an important area to target.

Severe salmonellosis causes vomiting diarrhoea and mortality

Twenty five percent of 550 pigs died over a period of a week with vomiting and diarrhoea due to salmonellosis from Salmonella Typhimurium PT U288 infection. Disease began three weeks after pigs entered a finishing unit at 13 weeks old. A second smaller earlier batch of pigs had shown similar signs also three weeks after entry. In view of the severity of disease and the presence of a dairy herd in close proximity to the pig unit, an advisory visit was undertaken. Environmental contamination with the salmonella involved was found with dust from the pig unit culturing positive for salmonella while that in the parlour did not. Rat droppings found outside the parlour were negative but rat and bird droppings outside the pig unit were positive for salmonella. Advice was given to reduce the risk of zoonotic infection and to address the disease in pigs and salmonella infection on the farm.

Respiratory Disease

Swine influenza diagnosed by submission of nasal swabs from weaners

Swine influenza was diagnosed in four and a half week old weaned pigs which arrived at the rearing site already coughing; 10% of 1,100 pigs were affected with three deaths. A non-pandemic swine influenza strain was detected by PCR in nasal swabs collected from acutely affected pigs. The strain was not identified as no virus was isolated, this can occur as PCR is more sensitive than virus isolation. Testing for swine influenza is performed free of charge as part of the national swine influenza surveillance programme funded by Defra; for further information, see http://vla.defra.gov.uk/science/sci_si.htm

Porcine circovirus-2 associated disease causing respiratory signs

Twenty pigs showed respiratory signs in a group of 250 and two died. The small herd of about 800 pigs was repopulated in November 2011 and serology revealed antibodies to Mycoplasma hyopneumonia, which was surprising as the pig source was supposedly free from the organism; it later emerged that the pigs had been vaccinated at the farm of origin. Two affected live pigs were submitted to Luddington to investigate further. The pigs had a grey-pink lobar pneumonia and enlarged lymph nodes. Lesions due to porcine circovirus-2 associated disease (PCVAD) were detected by histopathology in the viscera and lymph nodes. PCVAD was confirmed by immunohistochemistry and, following diagnosis, a PVC2 vaccination program was implemented.

Heavy lungworm burden in outdoor finisher

An 8-month-old finisher outdoor pig was found febrile, trembling and coughing and died within 48 hours in spite of antimicrobial treatment. Postmortem examination at the Royal Veterinary College/AHVLA surveillance centre revealed an acute haemorrhagic pneumonia suspected to have been a sequel to a heavy lungworm (Metastrongylus species) burden. There was also a chronic pericarditis that had resulted in fibrous adhesion of the entire pericardium to the epicardium. This was a longstanding lesion with the causative pathogen probably having been and gone. However, it may have contributed to the observed illthrift in the pig. Advice was given regarding anthelmintic treatment of the remaining herd.

Systemic and Miscellaneous Disease

Klebsiella species septicaemia outbreaks re-emerge in East Anglia

Three dead three-week-old pigs were submitted from an outdoor weaner-producer to investigate sudden deaths of good condition pigs between two and three weeks old occurring over the previous four batches in this three-weekly batch-farrowing herd. The numbers of pigs dying suddenly per batch were relatively low (estimated total of three to 20 pigs from up to 15 litters in each batch of about 100 litters), however, the deaths were unexpected and mostly of good pigs, meriting further investigation. Findings in two pigs submitted to Bury St Edmunds in good body condition were suggestive of a septicaemia with fibrin in the abdominal cavities and haemorrhages in the subcutis and kidneys and Klebsiella pneumoniae ssp pneumoniae was isolated. This organism was associated with six outbreaks of septicaemia in preweaned pigs on outdoor units in 2011 and this is the first outbreak diagnosed by AHVLA in 2012. Further information on the disease and investigations are available at: http://vla.defra.gov.uk/science/docs/sci_klebsiella.pdf
http://vla.defra.gov.uk/reports/docs/rep_survrep_qtlyp0112.pdf

Streptococcal disease due to the less common Streptococcus suis type 7

Two 18-week-old finisher pigs died in 24 hours from the same shed but not the same pen from 750 finishers. One pig was seen malaised and died soon after, the pig submitted to Bury St Edmunds was found dead. An on-farm post-mortem examination found haemorrhages in the heart, stomach serosa, subcutaneous fat and mesentery with other organs and organ systems unremarkable and viscera were submitted. Streptococcus suis type 7 was isolated from lung and meninges. There was no disease evident in the rest of the pigs and disease remained limited.

Streptococcus suis serotype 7 was also isolated from the pericardium of a seven-week old pig found dead and submitted to Langford. This organism is a recognised cause of septicaemia in pigs, although more common in younger pigs. Streptococcus suis type 7 is predominant in Europe and is sporadically seen causing primary disease in submissions such as these to AHVLA.

Active PRRSv infection and bacterial meningitis in flat-deck pigs found dead

Bacterial meningitis and concurrent active PRRS virus infection was identified in a pig which died at eightweeks-old, one of two found dead in flat decks on an indoor breeder finisher unit. Gross findings pointed to a bacterial septicaemia/meningitis with the meninges appearing cloudy with prominent blood vessels. No significant bacteria were isolated, however, histopathology confirmed a severe acute purulent meningitis consistent with a bacterial meningitis and PRRS virus was detected by PCR in the spleen. No further deaths were reported.

PRRS underlying illthrift and fading of weaners

Three live pigs were submitted to investigate ill thrift and fading after weaning on a farrow to rearing unit. Glässer’s disease had been suspected in the past and the herd was vaccinated against PCV-2 and enzootic pneumonia. Post-mortem examination revealed polyserositis in all three pigs from which E. coli 0115 was isolated. Three of the four pigs submitted were positive on PCR to PRRS virus, and this was considered the likely inciting cause for the bacterial problem.

Tumours resembling tuberculous lesions in an adult sow

Fixed tissue was submitted to Winchester from an adult British White sow which was found dead. The liver was reported to have been covered in caseous nodules with thickened edges to the liver lobes. Fibrinous fluid was present throughout the thoracic cavity with the lung tissue containing similar nodules. Histopathological examination identified the presence of a malignant neoplasia although it was not possible to ascribe a cell type to the neoplastic changes present. Histopathological examination also identified a fibrino-suppurative pleuritis which may have been a reflection of the neoplastic involvement in the lung or due to a secondary bacterial infection but is likely to have played a significant part in the animal’s death. Examination of these lesions was particularly worthwhile to rule out the possibility of the lesions being due to tuberculosis.

Skin Disease

Mange in rare-breed and commercial pigs

Sarcoptic mange was confirmed by detection of mites in a skin scraping from five to six month old pigs of various rare breeds (including British Lop and Saddleback). 20 to 30 of 115 pigs were reported to be affected. Skin lesions were described affecting the legs of weaners and growers.

Ill-thrift and death in pre-weaning and weaned piglets was investigated by post mortem examination at Langford. The underlying problem was identified as chronic mange with a secondary staphylococcal dermatitis. The staphylococcus isolated from the skin was Staphylococcus equorum which was considered likely to be an opportunist. It has been recorded as causing dermatitis in horses.

Musculoskeletal Disease

Outbreaks of acute polyarthritis due to Streptococcus suis types 1 and 14

One live 17-day-old sucking pig was submitted to investigate nervous signs of shaking, ataxia and recumbency in pigs aged 17 to 40 days on an indoor batch-farrowing grower producer. 20 to 30 pigs from a batch of 800 were affected with around 15 dying in each batch. A fibrinous polyarthritis was found from 4 which Streptococcus suis type 1 was isolated.

Fibrinopurulent polyarthritis due to streptococcal disease associated with Streptococcus suis type 1 infection was diagnosed in two 26-day-old pigs submitted from an outdoor unit on which young piglets were showing signs of malaise, some lameness and respiratory signs. No underlying viral disease was detected in the submitted pigs.

Pigs were submitted from a large outdoor grower producer to investigate lameness in approximately 20% of 1,500 six week old pigs from which 20 had died. All of the six and nine week old pigs submitted, and a four week old pre-weaned pig submitted had very consistent findings of a fibrinous polyarthritis suggestive of a bacterial disease; Streptococcus suis type 14 was isolated from the pre-weaned pig but not from any of the older pigs, some of which had been recently treated, others not so recently. In addition, swine influenza (non-pandemic strain) was detected in one of the six week old pigs. Interestingly, streptococcal disease has been detected concurrent with swine influenza on several occasions in AHVLA submissions.

Histopathology confirmed a suppurative arthritis and synovitis in the older pigs consistent with a bacterial cause. Examination of a further batch of older pigs was recommended to confirm whether the Streptococcus suis type 14 isolated from the younger pig accounts for the polyarthritis in the older pigs in which lesions were very similar and likely to be the same cause.