Background and history

Meningitis denotes inflammation of the meninges which are the membranes covering the brain. In the sucking piglet it is usually caused by Streptococcus suis, Haemophilus parasuis or sometimes bacteria such as E. coli and other streptococci.

Streptococci are common organisms in all animals including people. They are broadly but not entirely species specific. The main species is Streptococcus suis which occurs wherever pig farming is carried out. It is associated with a variety of conditions including meningitis, septicaemia (infection of the blood), polyserisitis (inflammation of the lining of the abdominal and chest cavities), arthritis, endocarditis (infection of the heart) and pneumonia. It has also been isolated from cases of rhinitis and abortion.

S. suis is carried for long periods in the tonsils and may be transmitted to the sucking piglet from the sow or from other piglets. The sow also provides a variable level of immunity in the colostrum. Streptococcal meningitis in sucking piglets is sporadic occurring occasionally in individual piglets.

Meningitis is uncommon in the sow but it is sometimes secondary to middle ear infection. If an infectious disease enters a herd for the first time sporadic cases in sows may be seen. Meningitis is seen in the sucking pigs and weaners associated with streptococcal infections.

Clinically healthy pigs can carry the organism in their tonsils for many months. Once a serotype has entered a herd no techniques are yet available to remove it and it becomes established in the tonsil as part of the normal flora.

Outside the pig, in very cold and freezing conditions S. suis may survive for 15 weeks or more but at normal room temperatures it dies within one to two weeks. It survives long periods in rotting carcasses. It is much more common in the immediate post-weaning period often starting 2 to 3 weeks after weaning and continuing through to approximately 16 weeks of age. In flat decks or nurseries almost 100 percent of pigs become carriers within three weeks.

Sereotypes

S. suis is sub-divided into at least 34 serotypes. They vary in their pathogenicity and the diseases they cause, both between and within types. Some types appear to be non-pathogenic and have been isolated mainly from healthy pigs, some are mainly associated with lung lesions, and some have been isolated from other animal species as well as pigs.

The pattern and relative importance of the different syndromes vary in different countries. In most S. suis type 1 is the main one in sucking piglets. In Denmark it is type 7. In the UK type 2 is the main cause of serious acute meningitis, along with polyserisitis and arthritis in weaned and growing pigs, and it is rarely associated with pneumonia.

S. suis also causes joint problems, particularly types 1 and 14. S. suis type 1 occasionally cause meningitis but more commonly joint infections. Meningitis in piglets is more commonly caused by Haemophilus parasuis or glässers disease.

The syndrome that is important and worrying to the pig farmer is persistent endemic meningitis caused by type 2.

Type 2 occasionally causes septicaemia and meningitis in people, mainly in people handling pigs or pig meat products. Fortunately human cases are rare in the West but a little more common in parts of South East Asia. There is at least one report of an isolation of type 14 from a human brain.

Similar diseases include:

• Acute kidney infection
• Aujeszky's disease (AD) (PR).
• Brain abscess.
• Haemophilus parasuis infection.
• Heat stroke.
• Listeriosis.
• Middle ear infection.
• Poisons.
• Water deprivation (salt poisoning)
• Joint infections
• Glässers disease
• Generalised septicaemia
• Hypoglycaemia

Clinical signs

Piglets, weaners and growers

• Shivering.
• Pigs show pain/discomfort.
• Pigs found lying on their belly.
• Hair raised.
• Grinding teeth
• Lateral movement of eyes (nystagmus).
• Fits and convulsions.
• On side paddling.
• Frothing at the mouth.
• In acute cases the piglet may just be found dead.

The organism invades the blood stream and is carried around the body where it may cause arthritis and pneumonia.

Sows (unusual)

• The sow is off feed.
• Trembling with an unsteady gate.
• The temperature is elevated, often as high as 42°C (108°F).
• The eye moves sideways.
• Fits occur and the sow cannot stand.
• The head may be on one side.

Diagnosis

This is based upon the signs in an individual pig, or if there are a number of cases, a specific infectious disease.

A history of the presence of recurring meningitis in weaned pigs is highly suggestive and is confirmed by the isolation of the organism from the brain and its specific identification, which not all diagnostic laboratories are capable of.

Because of the existence of strains that are non-pathogenic or only mildly pathogenic the isolation of S. suis type 2 from the tonsils of a pig is difficult to interpret. Isolation from the brain of a pig showing signs of meningitis is more conclusive.

Meningitis must be differentiated from the similar diseases listed above.

Causes

Meningitis often comes secondary to another condition, such as middle ear infection.

S. suis type 2 is spread from one pig to another by direct nose to nose contact. It can also spread within a herd by indirect contact and in confined space by aerosol infection. The most likely source of entry into the farm is the purchase of carrier boars or gilts.

There are also strains of low pathogenicity which may be activated by porcine reproductive and respiratory syndrome (PRRS) virus infection. PRRS may also raise the incidence of meningitis caused by pathogenic strains when it first enters a herd. Although PRRS alone does not affect the brain, it has been shown experimentally that many more pigs are affected with meningitis when they are infected with both S. suis type 2 and PRRS viruses than when they are infected with S. suis alone.

If you have the disease endemic in your herd the incidence increases with:

• High stocking density in flat decks.
• Continuous production systems which perpetuate infection.
• PRRS infections may activate S. suis already in the herd.
• Mixing of pigs post-weaning.
• A small cubic capacity air space per pig. Provide at least 0.8 m³ per pig at weaning.
• Poor ventilation and high humidity.
• High dust levels.
• Stress.
• Damp pens.
• High slurry levels under perforated metal floors and the damaging effects of gases to the respiratory system.
• Weighing pigs.
• Tattooing, ear notching and extra stress at weaning.
• Changes in nutritional status at critical times.
• Low vitamin E in the diet. Assess the response to adding 50–100iu/kg.

Prevention

Strategic medication

This is a method to adopt on farms where disease levels remain high. The following options are available:

• Identify the onset of disease and apply strategic medication 2 to 3 days before that time.
• Strategic medication can be applied in the drinking water using phenoxymethyl penicillin, tetracyclines, synthetic penicillin particularly amoxycillin, or trimethoprim/sulpha.
• In-feed medicate continuously from day of weaning through to six weeks post-weaning. Phenoxymethyl penicillin at a level of 300g/tonne is the medicine of choice. TMS could also be used.
• Inject all pigs with long-acting penicillin at weaning time.
• It is possible to vaccinate the sow using an autogenous vaccine to improve the colostral immunity.
• The sow can be injected with long-acting penicillin just before farrowing.

Environmental prevention

• S. suis is quickly killed by disinfectants in common use on farms, including phenolic disinfectants and chlorine and iodine based ones, detergents will also kill the organism in thirty minutes. "Savlon" is particularly effective.
• If your herd is free from this disease, try to keep it free.
• Check out your sources of replacement stock before purchase.
• Do not purchase pigs from herds with clinical cases of meningitis.
• Consider the causes of the spread of streptococci work to reduce.

Treatment

• This depends upon the cause. Always consider the common ones first which include middle ear infection, brain abscess, water deprivation and in some countries aujeszky's disease. Refer to the treatment for these specific diseases.
• For bacterial infections use penicillin, penicillin/streptomycin, synthetic penicillins, sulphonamides or amoxycillin. Inject twice daily.
• Use a quick acting penicillin for the first 24 hours followed by long-acting penicillin. Time is of the essence with this disease. Trimethoprim/sulpha would be an alternative medicine to use.
• Corticosteroids may also be required. Seek veterinarian advice.
• If your herd has a problem always examine the at risk pigs twice daily to identify and treat affected pigs early.
• Meningitis is extremely painful and the recovery rate is increased substantially through good nursing.
• Remove the piglet during the first 3 to 6 hours from the litter to a warm hospital pen and carefully supplement it with milk via a stomach tube.
• Provide warmth and bedding and trickle water into the pigs mouth from a hosepipe every 4 to 6 hours. Alternatively, water can be given by inserting a narrow hosepipe gently into the pigs rectum or using a flutter valve.