VLA: Streptococcus Suis 2, 14 Cause Disease in Pigs

UK - According to Defra's VLA Monthly Scanning Surveillance Report for February 2010, septic arthritis and sudden death were presenting signs in pigs, as well as the more familiar nervous presentation.

7 April 2010

5 minute read

Europe

Reproductive diseases

Influenza

Sudden onset pyrexia, agalactia, inappetence, lethargy and abortion in sows and an increase in neonatal piglet mortality prompted the submission of samples to Thirsk. Examination and testing on the aborted piglets and placentas identified no gross abnormalities or infectious agent. The neonatal piglets had empty stomachs and starvation due to maternal agalactia was considered the likely cause of death. There was evidence of seroconversion to swine influenza in the sows with titres of up to 1/80 detected to H1N2 and 195852 strains suggesting that swine influenza may have played a role in this abortion storm. PRRS virus was also detected in 5 out of 7 blood samples tested by PCR despite a comprehensive vaccination policy on the unit, and further characterization of the PRRS virus is in progress using molecular methods.

Alimentary tract diseases

Porcine Circovirus associated disease and Brachyspira pilosicoli

Rapid wasting was described in pigs between 10 and 16-weeks-old affecting a few of each batch of 50 pigs weaned at seven-weeks-old on an organic unit. Some loose faeces and a few PDNS cases were seen and there was poor response to treatment. No vaccination was used in rearing pigs. One typically affected pig was euthanased and submitted to Bury for necropsy. The pig was hairy, dehydrated, in poor body condition, had caecum and colon walls that were thickened with a roughened mucosa and had liquid green scour without ulceration and necrosis. Brachyspira pilosicoli was detected by PCR on large intestinal contents and histopathology revealed a granulomatous lymphadenopathy with macrophage inclusions typical of porcine circovirus. This confirmed porcine circovirus associated disease (PMWS) in addition to porcine colonic spirochaetosis due to B.pilosicoli.

Respiratory Diseases

H1N1 Swine Influenza

Outbreaks of swine influenza continued due to endemic strains. Avian-like H1N1 (similar to A/swEng/195852/92) virus was confirmed by Bury as the cause of widespread coughing in 10-week-old pigs on a nursery finisher site where 300 of 1000 pigs were affected with minimal mortality. A single dead pig was submitted in which there was extensive purple swollen cranioventral consolidation (EP equivalent score 41), polyarthritis and vegetative endocarditis. Streptococcus suis type 14 was isolated from the heart valve and joint and avian like H1 influenza virus was isolated from respiratory tissues. The influenza virus was considered to be of significance with respect to the widespread coughing described in the group of pigs and may well have predisposed to the streptococcal infection in the dead pig. Interestingly, in several recent swine influenza outbreaks, there has been concurrent streptococcal disease which has caused higher mortality than would probably have occurred in uncomplicated swine influenza virus infection.

Avian-like H1N1 influenza virus was also implicated as the cause of low level coughing with dyspnoea in a few pigs on a 425 pig indoor nursery unit on which approximately 10 six-week-old pigs were affected and one had died. Some meningitis and lameness had been seen on the unit. A fresh pluck was submitted showing cranioventral and patchy caudal consolidation affecting approximately 80 per cent of the lung mass. Swine influenza virus was detected by PCR and isolated from respiratory tissues confirming active infection with this endemic strain.

Other diseases

Streptococcus suis

Bury identified Strep. suis as a cause of both sudden death and lameness. In one case, the sudden death of four-week-old pigs from a group of 180 on a restocked breeder-finisher unit were investigated by submission of two dead pigs for necropsy. The affected pigs were the first batch of weaners through the system since depopulation. Gross lesions were consistent with septicaemia and Streptococcus suis type 2 was isolated from the meninges and liver and meningeal smears tested positive for Streptococcus suis 2 by FAT. There was no evidence of swine influenza or PRRSV virus involvement. In another case Streptococcus suis type 2 septicaemia was diagnosed as the cause of repeated spells of meningitis, lameness and mortality in 11-week-old pigs in which a total of 90 had died over an eight week period since arrival on an indoor nursery finisher unit of 1500 pigs. The organism was isolated from meninges, lungs and liver but no swine influenza virus or PRRSV were detected by PCR in the submitted pigs.

Strep. suis type 14 was also associated with lameness and neurological signs in five-week-old pigs in flat decks on an indoor breeder finisher unit. All had varying degrees of suppurative polyarthritis from which Streptococcus suis type 14 was isolated. The same organism was confirmed as the cause of polyarthritis causing lameness in 40 of 3000 five to six-week-old pigs responding well to antimicrobial treatment. Excess cloudy cream-like or yellow watery synovial fluid was present in joints.