AHVLA: Bone Disease Causes Recumbency in Pigs

by 5m Editor
27 April 2012, at 8:14am

UK - Respiratory disease prominent with an upsurge of PRRS in East Anglia, streptococcal disease, which is still a common diagnosis in post-weaned pigs and another case of bone disease causing recumbency in pigs on an inadequate diet have been observed in the latest AHVLA Scanning Surveillance Report.

Reproductive Disease

Fungal infection as part of a larger problem of reproductive failure

Fungal abortion was diagnosed by Bury St Edmunds in one litter from a closed indoor breeder-finisher unit on which more widespread abortion was suspected as sows were coming into milk approximately three weeks early as if due to farrow but piglets were never found. A high regular and irregular return rate was also occurring. Sows were vaccinated for erysipelas and PRRSV, parvovirus vaccination was also undertaken but only in gilts. One aborted piglet was submitted together with five mummified piglets from a different full-term litter. Aspergillus species was isolated from foetal stomach contents of the aborted piglet in pure growth, no other causes of abortion were detected, in particular no parvovirus antibody or virus was detected. Fungal abortion can occasionally occur in pigs, usually related to mouldy feed or bedding. It can cause sequential foetal death as seen in some litters on this farm, however it is unlikely (unless mycotoxins are involved) to cause infertility and a second submission of aborted and mummified piglets was submitted to investigate further. Porcine parvovirus PCR and other tests on these piglets did not yield any infectious causes of abortion and no fungal growth was obtained. Histopathology on the hearts did not reveal myocarditis making PCV2 associated foetopathy and EMCV unlikely. Investigations continue on this unit.

PRRS outbreak causing abortions, stillbirths, weak piglets and deaths of farrowing sows

severe PRRSV outbreak was diagnosed on an indoor weaner-producer unit. Disease began a month prior to submission as respiratory disease manifesting as coughing, inappetence and malaise mainly in the gilt yard which then spread to sows. In the week prior to submission six sows died just after farrowing after showing respiratory disease. Abortions also increased in the month prior to submission and, of 14 sows to farrow at the weekend prior to submission, 50 per cent of piglets had died either as stillbirths or having been born weak. Fifteen dead piglets from three litters were submitted which were stillborn or weak at birth. Given the prominence of the respiratory disease on the unit and the relationship of respiratory disease to sow deaths and stillborn/weak piglets, the likely diagnoses were considered to be PRRS and/or swine influenza, rather than notifiable disease. The unit was urged to submit a dead sow to investigate further and the following day, a sow dying after farrowing was submitted. This sow had severe well-established fibrinous pleuropneumonia with most of the lung consolidated and from which Pasteurella multocida was isolated. PRRSV was detected in the sow by PCR and also in two of the piglets tested and in the serum of another affected sow, consistent with a diagnosis of PRRS. The unit was vaccinating for PRRS with no obvious problems with vaccine storage or administration to account for the apparent vaccine failure and a report was made to VMD. No swine influenza virus was detected. Since the diagnosis was made, morbidity and mortality have reduced and the clinical situation is improving. Vaccination has been intensified on the unit.

Alimentary Diseases

Coccidiosis causing widespread diarrhoea from a week of age

Three live 10-day-old piglets were submitted to Shrewsbury to investigate the cause of diarrhoea affecting up to 70 per cent of piglets from 7-10 days of age with 45 piglets dying in the previous batch of 200 piglets. Sows were vaccinated for E. coli and clostridial disease. Gross findings were similar in all three pigs, with the entire length of the intestines dilated with watery to creamy, yellow-green, somewhat smelly contents. Histopathology revealed marked villus stunting and blunting with variable numbers of developing intraepithelial Isospora within the more distal aspects of the villi and in all three piglets there was a fibrinopurulent and necrotising enteritis associated with isosporosis. Live typically affected piglets are ideal for diagnosis of coccidiosis in preweaned pigs as significant disease may be present without detectable oocyst excretion.

Further outdoor units affected with intestinal torsion in replacement gilts

Four of 25 190-day-old replacement gilts were showing lethargy, reduced appetite, dyspnoea and coughing and two died. The problem began six days prior to submission approximately one week after the gilts arrived on the outdoor breeding unit. One dead gilt was submitted to Bury St Edmunds in good body condition. The gilt was dehydrated and post mortem examination revealed a clear significant intestinal torsion with no evidence of respiratory disease. There was a significant proportion of sandy material in the large intestine. It was recommended that any further gilts dying be submitted to determine whether this was a one-off or part of a group problem. We have seen several ‘outbreaks’ of intestinal torsion in replacement gilts after their arrival from indoor units onto outdoor breeding units. Excessive ingestion of sandy soil and stones is likely to be playing a part and amongst the measures which might be taken to reduce the risk of torsion are provision of plentiful straw to distract the gilts in the paddocks and feeding more regularly.

Respiratory Diseases

Active PCV2 associated disease with swine influenza causing respiratory disease

Live six-week-old pigs were submitted to Thirsk for post mortem examination to investigate wasting evident from two to three weeks post weaning on a 350 sow weekly farrowing farrow to finish indoor unit. Pigs were vaccinated at eight weeks old for PCV-2 and Mycoplasma hyopneumoniae. The pigs were wasted and hairy and had variable cranioventral purple lung consolidation with some significant interlobular oedema. In one pig there was excess fibrinous pleural fluid and early visceral pleurisy. Swine influenza was detected by PCR and a variety of bacterial causes of pneumonia were isolated, including Haemophilus parasuis, Pasteurella multocida and S. suis. Histopathology confirmed severe lymphadenopathy with lymphoid depletion and some intracytoplasmic inclusion bodies typical of PCV-2 associated disease. A diagnosis was made of swine influenza superimposed on a background of active PCVAD, with secondary bacterial pneumonia. It was recommended that the PCV-2 vaccination protocol should be reviewed.

An upsurge of PRRS outbreaks was diagnosed in the Bury St Edmunds region. Several typical cases are described below. Whether this upsurge relates to the spread of a particular strain, different strains or to disease manifesting on units where it had previously been controlled is, at this stage, unclear and is being investigated.

Widespread respiratory disease due to PRRS with pasteurellosis after entry to finishing unit

Approximately 50 per cent of 1,300 indoor 14-week-old finishers were reported to be showing respiratory signs with 14 deaths over a two week period. One fresh pluck was submitted showing consolidation of the ventral parts of both middle lung lobes. Pasteurella multocida and PRRS virus were detected. Immunohistochemistry confirmed PRRSV involvement in the pneumonia. The pigs had been vaccinated for PRRSV on arrival nine days prior to submission but were already coughing and it was suspected that the pigs had been challenged prior to arrival.

Mixed bacterial infection with PRRS in wasting growers

Wasting and respiratory disease were reported in approximately 10 per cent of growers in each batch of 300 in straw yards on an indoor breeder finisher unit. Pigs were vaccinated for Mycoplasma hyopneumoniae and PCV2, PRRS vaccine had also recently been initiated although the submitted pigs were not vaccinated. Mortality was approximately 2 per cent. Three pigs in poor body condition were submitted, two had chronic extensive pneumonia while two had significant diarrhoea without specific mucosal lesions. Both Haemophilus parasuis and Pasteurella multocida were isolated from the pneumonic lung and PRRSV was detected in the pigs by PCR. Immunohistochemistry confirmed involvement of the PRRS virus in the pneumonia. Brachyspira pilosicoli was isolated from one of the pigs with diarrhoea supporting a diagnosis of concurrent Brachyspira pilosicoli colitis. The unit has initiated PRRS vaccination of rearing pigs.

Poor response to antimicrobial treatment in coughing finishers with PRRS challenge

Clotted blood samples were submitted from a group of 2,000 16-week-old housed finishers in which approximately 10 per cent were affected by coughing, wasting, reddened ears and approximately 20 deaths with a poor response to antimicrobial treatment. PRRS was suspected to be underlying the problem and this was confirmed by detection of PRRS virus in two pools of five sera by PCR and seropositivity in unvaccinated finisher pigs.

PRRSv detected in coughing unwell gilts on outdoor unit

Mixed tissues including a pluck were submitted from a 26-week-old gilt on an outdoor unit. The gilt was one of a group of 30 all of which were coughing, lethargic and inappetent over a three day period prior to submission. The rest of the group improved following antimicrobial treatment. This one gilt died. There was a severe fibrinous pericarditis and endocarditis affecting the left atrioventricular valve and a nontypable Streptococcus suis was isolated from the heart valve. More significantly, with respect to the clinical disease in the rest of the group, PRRS virus was detected by PCR and was considered to be the most likely cause of the group problem.

Mixed viral infection with Glasser’s disease causing rapid wasting and coughing

Concurrent swine influenza, PRRSV and Glasser’s disease was diagnosed as the cause of rapid wasting with coughing in 15 of 340 13-week-old pigs, six other pigs had died over the previous week. One dead pig in poor body condition was submitted which was quite pale with watery blood due to a deep gastric ulcer affecting the entire pars oesophagea. There was a fibrinous polyserositis and a generalised lymphadenopathy. Haemophilus parasuis was isolated confirming Glasser’s disease and both swine influenza (not pandemic H1N1 2009) and PRRSV were detected by PCR. Dual infection with both swine influenza and PRRS was likely to be a significant factor precipitating Glasser’s disease.

Glasser’s disease diagnosed with underlying swine influenza in weaners

Increased mortality in seven-week-old weaners with nervous signs, swollen joints and low grade cough was found to be due to combined Glasser’s disease and swine influenza. The pigs had shown a poor response to antimicrobial treatment. Three dead pigs were submitted which had fibrinous polyserositis typical of Glasser’s disease which was confirmed by isolation of Haemophilus parasuis and swine influenza (pandemic H1N1 2009 strain) was detected by PCR.

Swine influenza with mixed bacterial infections

Four six-week-old weaners were submitted to Thirsk to investigate increased respiratory disease and wasting on an indoor 600-sow farrow to finish unit. There was also an increase in abattoir pleurisy lung scores. In summary, porcine respiratory disease complex was diagnosed due to Streptococcus suis and Haemophilus parasuis infections with underlying influenza and salmonellosis. It is likely that the incursion of influenza allowed other pathogens to manifest. It is not uncommon for pigs in which influenza is diagnosed to have been submitted as a result of the secondary infections rather than the influenza itself.

Concurrent swine influenza and PRRS associated with salmonellosis post-weaning

Multifactorial disease with both swine influenza and PRRS infections was diagnosed as the cause of a very poor performance in pigs post weaning on a 300 sow indoor farrow to finish unit. Pigs were reported to scour, become dyspnoeic and approximately 10 per cent then lose condition and die within the first ten days post weaning. Lung lesions were significant with multifocal haemorrhages, wedge-shaped purple/black areas of discolouration, some grey consolidation of cranioventral lobes and some areas of firm beige rubbery lung. Both PRRS and pandemic H1N1 2009 influenza were detected by PCR and Salmonella Typhimurium Copenhagen was isolated from lung. Dual infection with PRRS and influenza was likely to have compromised the pigs and led to salmonellosis. Vaccination of the sow herd for PRRSv is being considered (the herd was not previously vaccinated) as well as diligent attention to hygiene and acidification of water in order to mitigate the effects of the salmonellosis.

Urinary Diseases

Kidney infection causes sow deaths on outdoor unit

Chronic pyelonephritis was diagnosed as the cause of illness and death of a sow on an outdoor unit on which there had been two previous unexplained sudden deaths in sows in the previous week. The sow had been treated with antibiotics and the causative organism was not isolated. The sow was estimated to be five weeks pregnant, interestingly sows are considered to be more susceptible to pyelonephritis in the three weeks post-mating when their urine is more alkaline and supports the growth of organisms causing pyelonephritis better.

Nervous Diseases

Streptococcus suis type 7 was isolated from a swab taken from the meninges of a ten-week old grower to investigate the cause of sudden death. Ten pigs had been affected out of a group of 400, eight of which had died. S. suis 7 is an uncommon cause of primary disease in UK pigs but is prominent in some European countries.

Streptococcus suis type 2 continues to cause mortality in pigs of a range of ages and several examples are described below.

The carcase of a three-month-old gilt was submitted to Winchester with a history of fitting prior to death. The liver was markedly congested with fibrin strands present on the surface. The meninges were congested and haemorrhagic in appearance and S. suis type 2 was isolated confirming streptococcal meningitis.

Four dead six-week-old pigs were submitted to investigate the cause of lameness and nervous signs, manifesting as recumbency with tremors, in 45 of 1,200 pigs with 21 deaths over a two week period. There was a fibrinous meningitis and polyarthritis in two of the three pigs, S. suis type 2 was isolated from meninges, joints and liver confirming a diagnosis of S. suis type 2 disease. No involvement of swine influenza or PRRSV was detected.

Systemic and Miscellaneous Disease

Neonatal mortality due to lack of milk

A single whole litter of neonatal piglets were found dead one morning, resulting in the submission of two carcases to Preston. There was no indication that the piglets had sucked (no milk found in the alimentary tracts) and, as no other diagnosis was established, it was concluded that the likely cause of death was starvation complicated by a liver rupture and haemorrhage in one piglet. The farmer was advised to check the milk supply of sows if further cases occurred.

Musculoskeletal Disease

Streptococcus suis type 14 polyarthritis

Streptococcus suis type 14 was isolated from joints of a 2-week-old piglet submitted to Leahurst with polyarthritis, peritonitis and pericarditis. Fourteen of 35 piglets were affected by sudden recumbency over the period of a week. In the previous batch of litters, 3 of 35 had died and several recovered following antibimicrobial treatment. S. suis type 14 is as recognised cause of such outbreaks.

Poor bone mineralisation causing recumbency suspected to be due to an inadequate diet

Eight of a batch of 71 four month old pigs fed confectionery and custard waste with sow nuts were affected with hind limb weakness leading to reluctance to stand and recumbency. Post mortem examination at Shrewsbury revealed synovial changes involving the stifles and hip joints but no significant bacteria were isolated. There was also no evidence of neurological disease on neuropathological examination. Bone analysis revealed a significantly low bone ash content with normal calcium and phosphorus content. The poor bone mineralisation was suspected to be due to dietary deficiency. Review and improvement of the mineral content of the diet was prompted by these findings.

Further Reading

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