What is Parasitic Meningitis?

Meningitis Now, a UK meningitis charity, found that there are approximately 8,000 cases of meningitis in the UK every year. There are many different forms of the disease, and some are more harmful than others. However, almost all types of meningitis can be fatal to children. Since the 1990s, the number of deaths relating to meningitis has been steadily declining, but it still appears to be a troublesome disease.

According to the United Nations’ levels and trends in child mortality report (2017), meningitis is the second biggest infectious killer of infants and children under five in the entire world. The disease can be particularly difficult to beat due to the different types and causes of meningitis. This creates challenges in diagnosis and treatment by causing delays.

What is parasitic meningitis?

Parasitic meningitis is a rare form of the meningitis disease. Meningitis causes inflammation around the brain and spinal cord. It is the membranes that surround the brain and spinal cord that become inflamed. The membranes are called meninges; which is where the disease gets its name.

A parasite is an organism that lives in or on something else. This thing acts as its host, and the parasite feeds off its host to survive. Parasites are extremely small organisms that are invisible to the naked human eye and can grow into long worms as they get stronger from feeding off their host and from multiplying. The parasite itself is not a disease, but it can cause and spread diseases such as meningitis.

There are three different types of parasites that can affect humans, which are:

• Protozoa: Protozoa are single-celled organisms that can multiply in humans. These parasites can spread through contaminated food and water, person-to-person contact, and insect bites.
• Helminths: Helminths are parasitic worms that often take root in a person’s digestive tract. These parasites cannot multiply or divide within a human body and eventually pass through a person’s stool.
• Ectoparasites: Ectoparasites are small organisms that live on the outside of the body. These include ticks, fleas and lice. These types of parasites are not included in the parasites which cause parasitic meningitis. They cause diseases such as Lyme disease.

Parasitic meningitis cannot be transmitted from person to person, so it is not classed as contagious. It can only be caught by ingesting a parasite as parasites cause parasitic meningitis. If the parasite is infectious or carries eggs that are infected, then you are likely to become infected with parasitic meningitis. You catch parasitic meningitis if you ingest a parasite that causes the disease in your body.

These parasites can be found in the following places:

• Dirt.
• Contaminated food such as snails, raw fish, poultry or produce.
• Animals.
• Faeces.

What causes parasitic meningitis?

The most common cause of parasitic meningitis is a parasite called an amoeba (also known as Naegleria fowleri). This is an organism that can cause Primary Amoebic Meningoencephalitis (PAM) which can be fatal in nearly all cases.

This type of parasite is found in fresh warm water, such as lakes, rivers, ponds, and poorly maintained pools with low or no levels of chlorine. However, a distinguishing factor about this type of meningitis is that it can only be caught by entering the body through the nose (not the mouth).

The parasite goes up the nose where it then enters the brain and targets the brain tissue, causing PAM. Amoebic meningitis is unlikely to be caught in the UK due to the climate. The UK does not have fresh warm water most of the time due to our cold climate.

The second type of parasitic meningitis is eosinophilic meningitis. Eosinophilic meningitis is defined by the presence of at least 10% eosinophils (which are a type of disease-fighting white blood cell) in the blood and cerebrospinal fluid count. When a high count of these is found in the blood, it is a sign that parasitic meningitis may be present. Science Direct report that although there are several possible causes of high numbers of eosinophils in the body, parasitic infection is the main cause.

There are three types of parasites that can cause parasitic meningitis, which although more commonly found in tropical climates, are now spreading globally due to increased travelling.

These parasites are:

Angiostrongylus cantonensis

Angiostrongylus cantonensis is a parasite that can cause severe damage and disease to the central nervous system. The parasite is found in rodents such as rats and is commonly referred to as rat lungworm. If a rodent is infected and carrying the parasite, it can pass the eggs of the parasite in its faeces. It is the rats and rodents that carry the adult parasite worms.

This form of parasite can spread through rodent faeces. Infected rats excrete the parasite in their faeces which can then go on to infect snails and slugs. The snails and slugs then come into contact with the contaminated faeces and catch the larval worms. People then become infected when they eat raw snails that contain these worms or eat something that has been contaminated by the slugs or snails. This can be through fruit and vegetables such as lettuce.

Baylisascaris procyonis

Baylisascaris procyonis is a type of parasite found in racoons. It is more commonly called racoon roundworm. It is a very serious and rare form of parasitic meningitis. Similar to the above, the parasite is passed in racoon faeces where it is found in the faeces as a worm.

This can then be passed on by a number of different animals that may become contaminated by the faeces. It is the other animals that then go on to become the new accidental hosts of Baylisascaris procyonis. It is more likely for us to catch parasitic meningitis from an accidental animal host.

Gnathostoma spinigerum

Gnathostoma spinigerum is not commonly found in the UK. It is found in climates such as Asia, South and Central America, and Africa. It is the name for several types of parasitic worms that are found in fresh water, raw fish, reptiles and birds. Gnathostoma spinigerum reproduces on animals and is passed on through faeces. The larvae in the faeces are often eaten by water fleas which are eaten by other animals, causing them to be accidental hosts.

We can catch this parasite by eating undercooked meat from a contaminated animal. However, the parasite cannot reproduce in the human body but instead creates a disease that often targets the blood, creating swelling under the skin. It is the least common form of parasite to cause parasitic meningitis as it rarely targets the brain and spinal cord, but it is possible.

Signs and symptoms of parasitic meningitis

The early signs and symptoms of meningitis can mimic symptoms of the flu. However, if symptoms develop further, or are prolonged, it can be a sign of meningitis.

The most common signs and symptoms of parasitic meningitis include:

• A sudden intense headache.
• Stiff neck or inability to move your neck forwards.
• Nausea.
• Vomiting.
• Light sensitivity.
• Confusion.
• Painful sensation to touch on the skin.
• Weak muscles.
• Fever.
• Permanent disability.
• Coma.
• Itchy rash.
• A pins and needles sensation.

As mentioned in the introduction, it is infants and children who are most susceptible and most at risk from meningitis.

Due to this, we have listed the most concerning symptoms that relate specifically to infants and children below:

• High fever.
• Constant crying.
• Irritable.
• Sleeping problems.
• Difficulty waking from sleep.
• Being sluggish.
• Poor feeding.
• Vomiting.
• Stiffness in the neck and body.
• A bulge in the soft spot on top of a baby’s head.
• Skin rashes.
• Seizures.
• Difficulty concentrating.
• No appetite or thirst.

If treatment is not sought after quickly enough, it can result in severe complications that can turn into life-long issues.

The longer a person is suffering from parasitic meningitis without treatment, the greater the risk of permanent neurological damage, such as:

• Hearing loss.
• Memory problems.
• Learning disabilities.
• Brain damage.
• Trouble walking.
• Seizures.
• Kidney failure.
• Death.

The risk factors of parasitic meningitis

There are some factors that can create a higher risk of parasitic meningitis developing.

These include:

• Skipping vaccinations. Risk rises for anyone who hasn’t completed the recommended childhood or adult vaccination schedule.
• Age. Most cases of meningitis occur in children younger than age five years.
• Pregnancy. Pregnancy increases the risk of an infection caused by listeria bacteria, which also may cause meningitis. The infection increases the risk of miscarriage, stillbirth and premature delivery.
• Weakened immune system. AIDS, alcohol use disorder, diabetes, use of immunosuppression drugs and other factors that affect your immune system increase the risk of meningitis. Having a spleen removed also increases risk. People without a spleen should get vaccinated to lower the risk.

How is parasitic meningitis diagnosed?

The diagnosis of parasitic meningitis is based on the signs and symptoms presented. Depending on how a person presents at a medical centre, a health professional will conduct a questionnaire, physical examination, and laboratory tests.

It is important to tell a health professional if you have done any of the following in the lead-up to your signs and symptoms as this can help with diagnosis:

• Recent travel.
• Exposure to warm fresh water.
• If you have eaten any raw meat or fish.

During a physical examination a medical professional will examine:

• Your temperature.
• Skin issues such as any rashes or changes.
• Increased heart rate.
• Neck or muscle stiffness.
• Consciousness, concentration and awareness.

Following this, laboratory tests will be conducted in various forms where your medical professional will collect samples of blood and fluid. Tests may also be completed such as MRI or CT scans. These will scan your brain creating images for the medical professional to review to help determine swelling and inflammation around the brain.

How is parasitic meningitis treated?

There is not one specific treatment for parasitic meningitis. Rather, medication is prescribed for reducing symptoms or for preventing meningitis from developing when it is suspected. Preventive treatment with a prescription medication (called albendazole) may be considered in cases where there are suggestions that a parasite has been ingested through contaminated food or water, or from contact with a contaminated animal.

Parasitic meningitis is a rare form of meningitis, and a variety of medicines can be used to treat and relieve the pressure around the brain and kill the parasites in the body. Steroid medication can be commonly prescribed as an anti-parasitic drug as its function is as an anti-inflammatory.

If somebody with cancer contracts meningitis, a specific type of therapy is required to ensure that the parasites do not fuel or interfere with the cancer or treatment being undertaken.

How is parasitic meningitis prevented?

Some common prevention measures can be followed to reduce the risk of developing parasitic meningitis:

• Don’t eat raw snails or slugs. If eating snails, ensure they are thoroughly cooked first.
• Supervise infants and young children in environments where they may find snails, slugs or stray animals.
• Wash fresh vegetables and lettuce well before eating in case they have snails or slugs (or their slime) on them.
• Wash your hands well after gardening or touching animals.
• Consider controlling snails and slugs around vegetable patches and gardens and control vermin around the home. If snail pellets or rodent baits are used it is very important that precautions are taken to ensure young children don’t accidentally eat them.
• Do not swim in unchlorinated water.
• Ensure unused water systems are cleaned and treated prior to using them again.

Meningitis is identified as a preventable disease, which means that it can be stopped with the correct health, hygiene and lifestyle factors. Currently, it has one of the highest fatality rates and, in some countries, has the potential to cause devastating epidemics. There have been advances in vaccines for meningitis in many countries that aim to prevent or reduce the severity of the disease.

Despite this, recent estimates have identified that the global burden of meningitis in all age groups remains high in contemporary society; considering how technically and medicinally advanced the world has become.

Progress lags substantially behind that of other vaccine preventable diseases. The World Health Organization has developed a strategy that aims to defeat meningitis by 2030. This will improve awareness, diagnosis and surveillance of the disease, as more data will support investigation into treatment.