Summary: Parkinson’s disease affects more than 10 million people worldwide and is second only to dementia among major neurodegenerative disorders. Pathologically, it is defined by progressive loss of dopamine-producing neurons, which leads to tremor, impaired movement, stiffness, balance problems and cognitive decline. Until now, most animal models have relied on genetic manipulation or injections of potent neurotoxins to reproduce Parkinsonian symptoms, approaches that do not fully reflect the natural, gradual ways the disease can arise in people.
A new study from researchers at Texas A&M University describes the first non-toxic animal model of Parkinson’s disease using a naturally occurring mouse virus, Theiler’s murine encephalomyelitis virus (TMEV). This viral model reproduces long-term dopaminergic neuron loss, sustained motor impairment and progressive gait abnormalities seen in human Parkinson’s, supporting the hypothesis that common viral infections can act as environmental triggers for late-life neurodegeneration.
Key Findings
- A non-toxic, viral model: Unlike chemical or genetic models, the TMEV-based approach uses a natural mouse pathogen to initiate disease-like neuroinflammation and neuronal degeneration without exposing animals to artificial toxins.
- Rapid infection, lasting neuron loss: Researchers detected TMEV in dopamine-producing neurons within seven days of exposure. By one month post-infection the affected dopaminergic cells at the infection site were lost, confirmed by behavioral responses to dopamine-mimicking drugs.
- Persistent motor deficits: Infected animals performed significantly worse on standardized motor tests such as the pole test; these deficits persisted through week 20, the end of the study observation period.
- Progressive gait and balance decline: A high-resolution treadmill analysis assessing more than 100 gait parameters identified systemic weakness and progressive walking impairments mirroring clinical features of Parkinson’s disease.
- Support for the “hit-and-run” theory: The results reinforce the concept that a transient viral infection can trigger chronic, low-grade neuroinflammation that over time destroys vulnerable neuronal networks, producing late-onset neurodegeneration.
- Translational next steps: With this validated baseline, the team plans larger comparisons between the TMEV model and traditional chemical models, searches for early blood biomarkers, and mapping of immune signaling pathways that convert a common infection into progressive brain disease.
Source: Texas A&M University
Animal models are indispensable for studying Parkinson’s disease, but conventional approaches—gene edits or toxin injections—have limitations because they force symptoms to appear quickly and unnaturally. The TMEV model offers an alternative that mimics a more realistic, infection-driven route to dopaminergic neurodegeneration.
The pilot study demonstrates that a single, transient viral infection can trigger the same types of brain damage and functional impairments that characterize Parkinson’s in humans. This model therefore provides a tool to study how common infections might set in motion long-term neurodegenerative processes.
“Toxic-exposure models are useful, but not everyone exposed to chemicals develops Parkinson’s, so those models cannot capture all the pathways by which the disease begins and evolves in people,” said Candice Brinkmeyer-Langford, a neurodegenerative disease expert at the Texas A&M School of Public Health. The viral model permits observation of disease progression from an initial, natural infectious event through chronic neuroinflammatory processes and eventual neuronal loss.
Parkinson’s disease destroys dopaminergic neurons that regulate movement and balance, resulting in tremor, rigidity and impaired gait, along with psychological and cognitive symptoms. Although its exact causes are unknown, a combination of genetic susceptibility and environmental triggers—potentially including viral infections—has long been suspected. Similar viral links have been proposed for other neurodegenerative disorders such as ALS.
The study evaluated three core outcomes to validate the TMEV model:
- Brain cell infection and loss: One week after infection, TMEV was present in dopamine-producing neurons. By one month, those neurons were destroyed in the infected area. Behavioral testing after administration of a dopamine-mimicking drug produced movement patterns consistent with dopaminergic cell loss, confirming progressive neuronal damage.
- Motor speed and coordination: Using the pole test, researchers compared 13 infected animals with 14 controls. Infected animals showed slower completion times and impaired coordination that persisted through week 20, indicating chronic motor deficits analogous to human Parkinson’s symptoms.
- Detailed gait analysis: A specialized treadmill examined more than 100 gait parameters to measure walking, balance and motor function. The results revealed systemic weakness and progressive gait deterioration following dopaminergic neuron loss caused by TMEV infection.
With this model established, the team intends to directly compare TMEV-driven pathology against standard toxin-based models, search for early biomarkers in blood, and investigate the immune-cell signaling mechanisms that convert an ordinary viral exposure into a long-term degenerative process.
“The global population is aging rapidly, and the number of people with Parkinson’s is projected to rise substantially,” Brinkmeyer-Langford said. Developing models that reflect realistic disease origins is therefore critical to identifying preventive strategies and effective therapies.
Other contributors to the study from Texas A&M include graduate student Tae Wook Kang (College of Veterinary Medicine and Biomedical Sciences), Rahul Srinivasan (Naresh K. Vashisht College of Medicine), and C. Jane Welsh (VMBS and Department of Neuroscience and Experimental Therapeutics). The work was supported by the National Institute for Neurological Disorders and Stroke and a Texas A&M College of Veterinary Medicine and Biomedical Sciences Graduate Trainee Grant.
Key Questions Answered
Q: Why is moving from toxin-based models to a viral infection model important for Parkinson’s research?
A: Toxin-based models force rapid onset of symptoms and skip the slow, multistage processes that likely occur in people. A natural viral model like TMEV lets researchers observe how a common infection can initiate chronic neuroinflammation and progressive neuronal loss over time, revealing realistic causal pathways and potential early intervention points.
Q: How can a virus that infects someone years earlier cause neurodegeneration later?
A: The “hit-and-run” theory proposes that a transient infection can trigger a persistent, low-grade inflammatory state in brain immune cells. This chronic inflammation gradually damages vulnerable neurons—especially dopaminergic cells—over years or decades until clinical symptoms emerge.
Q: Does a common viral infection mean a person will develop Parkinson’s or ALS?
A: No. Viral infections interact with an individual’s genetic makeup and other environmental factors. Only in certain genetic contexts might a routine infection contribute to later neurodegenerative disease. This model will help identify which genetic and immunological profiles increase long-term risk.
Editorial Notes
- Article edited by a Neuroscience News editor.
- Journal paper reviewed in full and contextualized by staff.
About this neurology and Parkinson’s disease research news
Author: Ann Kellett
Source: Texas A&M University
Contact: Ann Kellett – Texas A&M
Image: Image credited to Neuroscience News
Original Research: Open access. “Theiler’s murine encephalomyelitis virus as the infectious agent for a virally induced mouse model of Parkinson’s disease” by Tae Wook Kang, Rahul Srinivasan, Candice Brinkmeyer-Langford, C. Jane Welsh. Brain, Behavior & Immunity – Health. DOI: 10.1016/j.bbih.2026.101230
Abstract
Theiler’s murine encephalomyelitis virus as the infectious agent for a virally induced mouse model of Parkinson’s disease
Parkinson’s disease (PD) is the second most common neurodegenerative disorder with a prevalence exceeding ten million patients worldwide. The etiology of PD remains unclear, but virus-associated neuroinflammation has emerged as a possible contributor. Conventional animal models reproduce some PD pathophysiology, such as degeneration of dopaminergic neurons in the substantia nigra pars compacta, but typically rely on harmful neurotoxins to induce symptoms. We present a virally induced neuroinflammatory model of PD in C57BL/6J mice using the naturally occurring pathogen Theiler’s murine encephalomyelitis virus (TMEV). This model provides a non-toxic tool to advance understanding of PD pathogenesis and to evaluate potential therapeutic and diagnostic approaches.