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PRRS Breakdown Diagnosed in Breeding Unit

by 5m Editor
5 April 2012, at 8:09am

UK - In the latest AHVLA Scanning Surveillance Report, a PRRS breakdown was observed on an unvaccinated indoor breeding unit.

Reproductive Disease

PRRS breakdown in a naïve breeding herd

A PRRS breakdown was diagnosed on an unvaccinated indoor breeding unit by PCR testing of stillborn and low-viability neonatal piglets submitted to Bury St Edmunds. Most piglets in 25% of litters were affected in the first farrowing batch to be affected with a marked reduction in the numbers of piglets weaned. Gross findings in the submitted piglets were non-specific but included subtle petechiation of the kidneys, a non-specific lesion but seen before in PRRS outbreaks. PRRS virus was detected by PCR in pooled sera from the low-viability piglets and in the spleens of stillborn piglets. As PRRS was strongly suspected from the outset, all sows were vaccinated rapidly and to date, although the subsequent farrowing batch was affected, the severity of disease was reduced.

Reproductive losses due to leptospirosis associated with rodents

Leptospirosis was confirmed as the cause of reproductive losses in a 200-sow, recently repopulated herd consisting mainly of gilts. Abortion was occurring at different stages of pregnancy and late returns to service were also increased. The problem was mainly seen in the gilts but some second parity sows were also affected. There was a history of a rodent problem which an outside pest control company was called in to manage. Rodents are recognized reservoirs of several Leptospira serovars. Examination of foetal tissues revealed a mottled reticular pattern on the liver of one foetus with occasional pinpoint white spots present on the surface. Leptospires were detected in foetal kidney by PCR and also by histopathology in both foetal liver and kidney. Serology on bloods from affected sows revealed antibodies to both Leptospira Bratislava and Icterohaemorrhagiae. Antimicrobial treatment was instigated and the farm is being monitored by the attending private veterinary surgeon. Advice was given on the potential for zoonotic infection. Rodent control is now progressing well and advice was given to promptly and safely collect and dispose of rodent carcases.

Alimentary Disease

Wasting in finishers due to Brachyspira pilosicoli colitis

Brachyspira pilosicoli colitis was diagnosed as the cause of wasting and diarrhoea with some lethargy in 30 of 300 12-week-old housed finishers. The problem had been on-going for eight days in the batch and the previous batch had also been affected. Mortality was low and principally through culling but a significant growth check occurred. Two euthanased pigs were submitted in quite poor body condition with a marked grey diarrhoea. Large intestinal lesions were mild and Brachyspira pilosicoli was identified by both PCR and culture. There was no evidence of salmonella infection, swine dysentery or PCV2 associated disease.

Rotaviral enteritis in neonatal pigs

Rotavirus was detected in faeces from a two-day-old piglet with yellow scour by Starcross. Rotaviral enteritis typically causes scour from one-day-old and older with high morbidity and low mortality unless complicated by dehydration or other infections. Optimising gilt acclimatisation, ensuring adequate colostral intake, strict cleaning and disinfection and good hygiene are all important in control. There is no vaccine available at present.

Salmonellosis diagnoses continue in growing pigs

Multiple diagnoses of salmonellosis were made in growing pigs, and two typical examples are described below:

Approximately 25 of 150 eight-week-old pigs on a nursery-finisher unit of 1,200 pigs were affected with loss of condition, diarrhoea and eight deaths. A portion of fresh small intestine was submitted which was dilated with foul-smelling brown fluid and fibrin floccules with areas of the mucosa showing diphtheresis. Salmonella Typhimurium phage type U288 was isolated, consistent with salmonellosis in the group.

An increase in diarrhoea and mortality (up to 3.5 per cent) in 11-week-old pigs which had been ongoing for approximately a month stimulated the submission of three dead pigs. All three had necrotic typhlocolitis and Salmonella Typhimurium Copenhagen phage type 193 was isolated confirming the suspected salmonellosis; no involvement of Brachyspira infection was detected.

Respiratory Disease

High morbidity coughing in weaners in a herd due to swine influenza

Swine influenza was diagnosed as the cause of coughing in five-week-old housed weaners in which signs spread over four days to affect 80 per cent of 1,100 pigs. The diagnosis was achieved by submission of nasal swabs from acutely affected pigs to Bury St Edmunds for testing free of charge under the Defra-funded Swine Influenza Surveillance Project.

Swine influenza underlying post-weaning diarrhoea and weight loss

Three live 27-day-old weaners were submitted to Thirsk five days after weaning to investigate a severe productive cough and some diarrhoea on a 1,300 pig nursery straw yard unit. Pigs were housed in groups of 220 and were sourced from two breeding units. Pigs were reported to look unwell, stop eating and lose condition. Swine influenza virus was detected in all three pigs and was considered to be the major contributor to the clinical signs observed, with pigs then being affected by a variety of enteric infections. Investigations into the cause of diarrhoea detected rotavirus in one pig, a significant Isospora suis oocyst count in another and marked to moderate villus atrophy in the small intestines suggesting an earlier enteric insult. Large numbers of cryptosporidia were present in the colon of two pigs examined which is an unusual finding in pigs.

Swine influenza virus was successfully isolated from two submissions from late 2011 in which swine influenza was diagnosed by detection of PCR in nasal swabs. In both cases, the virus isolated was H1N2 strain. The swine influenza strains detected in England in recent months are pandemic H1N1 2009 and H1N2.

Systemic & Miscellaneous Diseases

PRRS underlying deaths due to Streptococcus suis disease

One dead six-week-old pig was submitted to investigate malaise and mortality in pigs aged six to twelve weeks in flat-deck and grower accommodation on an indoor breeder finisher unit. Six deaths were reported from 550 six-week-old pigs following short term illness with blue discolouration of the ears and poor response to antimicrobial treatment. The ears of the submitted pig were both affected with necrosis of the distal pinnae and there was blotchy red discolouration of the ventral skin, arthritis and non-specific lesions including fibrin stranding and excess food in body cavities suggestive of possible septicaemia. Streptococcus suis 2 FAT on the meninges was positive, although the organism was not isolated, possibly due to antimicrobial treatment. Histopathology was consistent with a septicaemia which was also the likely cause of the ear tip necrosis due to thrombosed blood vessels. PRRS virus was detected by PCR and was considered to be the likely primary agent of disease, predisposing to concurrent infections such as Streptococcus suis 2.

Neonatal deaths suspected to be due to poor milk supply in gilts

Eight of a litter of 10 piglets were found dead at five-days-old on an outdoor gilt breeding unit. In the batch of 60 litters, ten were similarly affected. Post-mortem examination was fairly unremarkable in the piglets which were in quite poor body condition. None had milk in the stomachs and the intestines were quite empty; in addition, the bacterial flora of the intestines appeared abnormal. The findings were not suggestive of an infectious cause of death and no pathogens were detected suggesting a managemental problem was involved. This was supported out by the attending veterinary surgeon’s opinion that gilts were not coming in to milk properly, with a problem in gilts’ lactation diet quality being addressed. The fact that gilts arrived on the unit one week prior to farrowing into shared farrowing paddocks was also suspected to be part of the problem.

Nervous disease

Meningitis due to Streptococcus suis type 2 on several units

Streptococcus suis type 2 meningitis and septicaemia was diagnosed as the cause of fitting in a euthanased two-month-old piglet submitted to Carmarthen. A litter mate died after showing similar clinical signs within the previous few days. The meninges were congested and purulent material has accumulated between the cerebrum and cerebellum. S. suis type 2 was isolated from spleen, liver, lung and brain.

S. suis 2 infection was diagnosed at Bury St Edmunds as the cause of streptococcal meningitis and septicaemia in six-week-old pigs. The farm had reported a problem over a period of two weeks of pigs becoming recumbent with tremors and dying with no response to chlortetracycline treatment in water. Four dead pigs were submitted with fibrinous meningitis and arthritis from which S. suis type 2 was isolated. No viral involvement was identified, however, the S. suis type 2 showed in vitro resistance to tetracycline, explaining the poor response to antimicrobial treatment; the isolate remained susceptible to penicillin and trimethoprim/sulphamethoxazole.

Sutton Bonington isolated S. suis type 2 from brain and liver of a nine-week-old pig which died following a short period of malaise on a single source 1600 pig nursery-finisher unit. Five other pigs aged 4-10 weeks had died recently, some as sudden deaths and others with signs of meningitis. Trimediazine medicated feed had been fed on arrival and antimicrobial sensitivity testing revealed in vitro resistance of the S. suis isolate to trimediazine.

Urinary disease

Fatal kidney infection in Middle White sow

Acute pyelonephritis was diagnosed by Luddington following post mortem examination of a three-year-old heavily pregnant Middle White sow, part of an indoor herd, following short-term malaise and a vulval discharge. No bacteria were isolated but the sow had been treated several times. No health problems were reported in the remainder of the herd.

Neoplasia in a pig suspected to have cystitis

A 19-week-old Gloucester old Spot male pig was treated by its owner for suspected cystitis but failed to respond to treatment and was euthanased. On-farm post mortem examination revealed an enlarged liver and spleen and almost white kidneys with ecchymotic subcapsular haemorrhages. Histopathological examination revealed the lesions to be those of multicentric lymphoma in liver, kidney and bladder tissue, a sporadic neoplasia occurring in individual pigs.

Further Reading

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