Streptococcus & Enterococcus Infections - Pigs

Also Known As: Bacterial Endocarditis –- Bacterial Pericarditis – Ear/Skin/Teat Necrosis – Streptococcal Pustules – Enterococcal Diarrhoea – Joint Ill – Jowl Abscess – Streptococcal Meningitis – Streptococcal Lymphadenitis – Streptococcosis – Streptococcal Otitis

Caused By: Streptococcus suis – S. bovis – S. dysgalactiae – S. hyointestinalis – S. intestinalis - S. porcinus - Enterococcus faecalis – E. durans

Introduction

Streptoccocal and Enterococcal infections are common in pigs as the organisms are commensal in their gastrointestinal and reproductive tracts and environments. A multitude of diseases affecting many systems can be the result of infection with these organisms.

Most streptococcus species are opportunistic and the main precursor to S. suis infection in pigs is Porcine Reproductive and Respiratory Syndrome.

S. suis is also a zoonosis of significance which can cause severe disease in humans.

Distribution

These organisms are present worldwide due to their commensal nature.

S. suis capsular type 2 is prevalent in almost all countries and is the organism of most importance from this group of pathogens.

Streptococcus suis Infection

Signalment and Distribution

The main host of S. suis is the domestic pig but cattle, sheep, goats, horses, dogs, cats and people can acquire the infection with varying clinical presentations.

It is a natural inhabitant of the respiratory, reproductive and gastrointestinal tracts'. Disease usually occurs following movement of pigs between herds and is transmitted via the respiratory route, during suckling and also vertically from infected sows to piglets.

Clinical Signs

Disease is often multisystemic and may involve the respiratory, neurological, cardiovascular, gastrointestinal systems and skin. The first sign is usually pyrexia. Peracute cases will be found dead with no premonitory signs.

Pneumonia is a common presentation of infected pigs usually featuring coughing, sneezing, nasal discharge, epistaxis, tachypnoea, dyspnoea and a change in voice.

Pigs with streptococcal pericarditis or endocarditis are tachycardic, have muffled heart sounds and murmurs, are often ascitic and may exhibit jugular distension. Pulses may be weak, mucous membranes pale and an ECG often lacks P-waves and shows dysrhythmmias.

Meningitis is common and severe and may cause or be a consequence of otitis media. Ear infections may present as an aural discharge, deafness or scratching of the ears. The neurological disease features seizures, torticollis, head tilt, muscle spasms, paddling, tremors, paresis which many involve all four limbs, ataxia, hypermetria, irritability, depression, circling, head pressing and abnormal proprioception. Cranial nerve deficits may be seen and opthalmological signs may result. Pigs are often found dead and mortality may be significant.

If the organism enters the joints by direct or haematogenous routes, arthritis develops and leads to lameness, weakness and joint swelling, which may rupture and expose the purulent exudate. This is also a common consequence of navel infection in newborn pigs.

Enteritis is also commonly caused by S. suis and presents as anorexia, diarrhoea and dehydration.

The skin may be a route of entry for the pathogens or a later sign of systemic disease. Subcutaneous masses, abscesses and nodules may form and erythema, ulcers and sloughing can occur. The coat is often rough and “staring”.

Reproductive disease can also result, causing agalactia, abortion and mastitis.

Diagnosis

Diagnosis is often presumptive bases upon epidemiology, clinical signs and lesions seen at necropsy.

It can be confirmed by isolation from tissues, joint fluid and cerebrospinal fluid, by PCR and serologically by ELISA.

On post-mortem, suppurative bronchopneumonia, neutrophilic meningitis/encephalitis and epicarditis are seen. Microscopic lesions are seen in the lung, brain, heart and joints.

Treatment

Most S. suis isolates are susceptible to ampicillin and amoxicillin. Penicillin can also be used but resistance is slightly more common. Culture and sensitivity is recommended as a high degree of resistance to many antibiotics occurs. Anti-inflammatory therapy is also useful and advised.

S. suis in humans

Human cases of S. suis are infrequent but severe. Meningitis is the most common manifestation followed by septicaemia and endocarditis. The disease is often mistaken for other pathogens due to laboratories being unaware of its existence. In most cases. S. suis capsular type 2 is responsible and disease is acquired through close contact with pigs or contaminated pork products, which enters through skin abrasions or cuts..

Other Species and Diseases

Enteritis

Diarrhoea is the primary sign associated with Enterococcus spp. infections, usually in neonatal pigs 2 -14 days old and commonly associated with E. durans. Mortality is usually low, in contrast with other neonatal enteritis pathogens. The condition can also affect calves and puppies.

Lymphadenitis

Streptococcal lymphadenitis is usually the result of infection with S. porcinus in growing pigs. Abscess formation is also a common feature of infection, forming on the jowl or in the cervical region. This is the result of dissemination of infection from its initial location in the pharynx and tonsils. Infection can be transmitted via ingestion of abscess exudates/contents or infected faeces, by direct contact or via drinking water. This disease is of particular economic importance in the USA. It can be diagnosed by isolation from tonsils, pharynx, nasal cavity and vagina/prepuce. S. porcinus is often isolated from pneumonia, enteritis and arthritis cases also, but is thought to be secondary in these situations. This disease is not zoonotic.

Control

Minimising stock density, keeping stress minimal and environmental conditions consistent can help to reduce the prevalence and transmission of infection. Pigs with an age difference of more than two weeks should not be mixed. All-in/all-out systems are ideal.

Most disinfectants are active against S. suis, but organic matter can reduce their efficacy so units should be pre-cleaned.

Antibiotics can also be used prophylactically but the implications should always be considered.

Vaccines are available but results are inconsistent.

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References

This article was originally sourced from The Animal Health & Production Compendium (AHPC) published online by CABI during the OVAL Project. The datasheet was accessed on 4 July 2011.

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