When Nature Disrupts the Brain: Lyme Disease, Parasites, and How Your Genes Play a Role

Most of us don’t expect a walk in the woods, a mosquito bite, or a plate of undercooked meat to affect our nervous system. Yet, a surprising number of infections and parasites from the natural world can invade or impact the human brain and nerves—sometimes subtly, sometimes dramatically.

And here’s the twist: your genes may determine how badly you’re affected—or if you even notice at all.

Let’s explore the most fascinating examples where microbes and parasites collide with the nervous system, and how your genetic blueprint can influence the outcome.

🦠 Lyme Disease and Neuroborreliosis: When a Tick Changes Your Brain

What is Lyme Disease?

Lyme disease is an infection caused by the bacterium Borrelia burgdorferi (or Borrelia afzelii/garinii in Europe). It spreads through the bite of infected Ixodes ticks (deer ticks).

What is Neuroborreliosis?

When Lyme bacteria spread to the nervous system, it's called neuroborreliosis. This can happen weeks to months after infection.

Neurological Symptoms:

• Facial paralysis (often called Bell’s palsy)
  
• Burning or shooting pain in the limbs (peripheral neuropathy)
  
• Stiff neck and headaches (signs of meningitis)
  
• Trouble with memory, concentration, mood (so-called Lyme brain)
  
  

How Genes Play a Role:

• HLA genes influence how well your immune system “sees” and fights the bacteria. Certain types may allow Borrelia to hide more easily.
  
  
• MTHFR, GST, and SOD2 genes help detoxify inflammation-related chemicals. If they’re slow or inefficient, symptoms may be worse or last longer.
  
  
• People with slow COMT activity may also have stronger responses to inflammation and pain.
  
  

🧠 Toxoplasma gondii: The Parasite That Can Change Behavior

What is it?

Toxoplasma gondii is a single-celled parasite found in raw or undercooked meat and in cat feces. Up to one-third of the world’s population carries it, often without symptoms.

What it does to the brain:

In most healthy people, it forms cysts in muscle and brain tissue and stays dormant. But in some, it can subtly alter behavior or cause serious illness.

In the brain, it may cause:

• Delayed reaction times
  
• Increased risk-taking behavior
  
• Mood disorders
  
• Seizures or encephalitis (brain inflammation) in the immunocompromised
  
  

Gene Interactions:

• Variants in MAOA and COMT (enzymes that regulate mood chemicals) may increase sensitivity to the parasite’s brain effects.
  
  
• Poor-functioning immune genes (like IFN-γ or TLRs) can make it harder to keep the parasite under control.
  
  

💀 Rabies Virus: A Viral Sprint to the Brain

What is rabies?

Rabies is a deadly virus spread through the saliva of infected animals, especially dogs and bats. Once symptoms appear, it’s nearly always fatal.

What happens in the brain?

Rabies travels along peripheral nerves into the brain, causing acute viral encephalitis.

Symptoms:

• Agitation, confusion, hallucinations
  
• Hydrophobia (fear of water)
  
• Seizures and coma
  
• Paralysis and death
  
  

Genetic Defense:

• People with strong interferon response genes (e.g., IFNAR) may mount a better early defense.
  
• Some rare neuronal repair genes may influence disease progression.
  
  

🧬 Taenia solium and Neurocysticercosis: Worms in the Brain

 

What is Taenia solium?

It’s a pork tapeworm. While eating undercooked pork can give you an intestinal infection, eating the tapeworm’s eggs (through contaminated water or food) leads to something far more dangerous: neurocysticercosis.

 

What is Neurocysticercosis?

It’s a disease where tapeworm larvae form cysts in the brain or spinal cord. It’s the most common parasitic brain infection worldwide and a leading cause of adult-onset epilepsy in developing countries.

Symptoms depend on cyst location:

• Seizures
  
• Headaches
  
• Balance or vision issues
  
• Brain swelling and hydrocephalus (fluid buildup)
  
  

Genetic Risk Factors:

• Certain HLA types may trigger a stronger inflammatory response when cysts die, worsening symptoms.
  
• Genes like APOE (involved in brain protection and repair) may affect how damaging the cysts are.
  
  

🌊 Naegleria fowleri: The Brain-Eating Amoeba

 

What is it?

A rare but deadly amoeba found in warm freshwater (lakes, hot springs). It infects people through the nose during water activities.

 

What it causes:

Primary Amebic Meningoencephalitis (PAM) – a rapidly progressing brain infection that’s almost always fatal.

 

Symptoms:

• Headache, fever, stiff neck
  
• Confusion, hallucinations
  
• Seizures, coma
  
• Death within days
  
  

Genetic factors:

• Strong innate immune genes (like NLRP3 and TLR4) may provide slightly better resistance.
  
• Delays in immune recognition can allow rapid amoeba growth.
  
  

🦟 West Nile Virus: A Mosquito-Borne Brain Threat

 

What is it?

A virus spread by mosquito bites. In most people, it's mild or symptom-free—but in some, it leads to neuroinvasive disease.

 

Brain symptoms:

• Encephalitis (brain swelling)
  
• Meningitis (inflammation of brain lining)
  
• Muscle weakness or tremors
  
• Memory problems or paralysis
  
  

Genes and immunity:

• CCR5 gene mutations may increase susceptibility.
  
• Low-function glutathione genes (e.g., GSTM1, GSS) may lead to greater oxidative damage in the brain.
  
  

🧠 The Gut-Brain Axis and Parasites

Not all infections go straight to your brain. Some change your gut microbiome, which in turn influences the brain. This is called the gut-brain axis.

 

How it works:

• Microbes and parasites can produce or block neurotransmitters like serotonin, dopamine, and GABA.
  
• They can alter immune signals that travel to the brain.
  
• They may increase gut permeability ("leaky gut"), allowing inflammatory molecules into the bloodstream.
  
  

Genetic sensitivities:

• TPH2, MAOA, and VDR genes affect neurotransmitter production and sensitivity.
  
• Mutations in MTHFR, QDPR, and BHMT may limit your ability to process nutrients needed for brain chemicals.
  
  

🛡️ How to Stay Safe