Public Health · Polk County · Rat Lungworm
Rat Lungworm in Florida —
What Lakeland & Polk County Residents Need to Know
Angiostrongylus cantonensis is documented in Florida’s roof rat population. The first locally acquired human cases were confirmed in Florida children in 2021–2022. This is not a theoretical risk.
What Is Rat Lungworm and Why Is It a Growing Risk in Lakeland and Polk County?
Angiostrongylus cantonensis is a parasitic nematode that causes eosinophilic meningitis in humans. Adult worms live in the pulmonary arteries of rats — hence “rat lungworm.” The parasite’s lifecycle requires two hosts: rats are the definitive (final) host where adult worms develop, and snails and slugs are intermediate hosts where larvae develop to the infective stage.
Humans become infected by accidentally ingesting infected snails, slugs, or snail/slug slime — through contaminated garden produce, unwashed vegetables, or contact with snail trails in high-risk environments. Once inside a human host, the larvae migrate to the brain. Human beings are dead-end hosts; the parasite cannot complete its lifecycle in humans and eventually dies — but not before causing significant inflammation in the brain tissue (eosinophilic meningitis).
UF IFAS research confirmed A. cantonensis is present throughout Florida’s roof rat population and in multiple snail species found in Polk County. A 2020 PLOS Neglected Tropical Diseases paper confirmed the parasite in Florida from the panhandle to Miami. The CDC confirmed the first locally acquired Florida cases in three children in 2021–2022, occurring in the Orlando metro area — within 50 miles of Lakeland.
What Are the Symptoms of Rat Lungworm Infection — and How Is It Diagnosed?
Rat lungworm infection presents as eosinophilic meningitis — inflammation of the brain’s lining caused by the parasite’s migration and death in neural tissue. Symptoms typically appear 1–3 weeks after ingestion of an infected snail or slug.
Symptoms in Adults
- Severe, persistent headache (often described as the worst headache of their life)
- Neck stiffness — may be severe enough to prevent chin-to-chest movement
- Nausea and vomiting
- Tingling or abnormal sensations in arms and legs (paresthesia)
- Low-grade fever
- Visual disturbances or eye pain in some cases
- Partial facial paralysis (rare)
Symptoms in Children
- Nausea and vomiting (more prominent than in adults)
- Fever
- Lethargy and refusal to walk (as in the CDC 2021 case — 19-month-old child)
- Neck stiffness
- Less prominent neurological symptoms than adults
- Positive Kernig sign (inability to extend knee when hip is flexed)
Diagnosis: Rat lungworm is diagnosed through cerebrospinal fluid (CSF) analysis showing eosinophilic pleocytosis (high eosinophil count), plus PCR testing or next-generation sequencing. It mimics bacterial meningitis on initial presentation — the key distinguishing finding is eosinophils in CSF rather than the polymorphonuclear cells seen in bacterial meningitis. The incubation period of 1–3 weeks means the connection to snail ingestion is often not immediately apparent to treating physicians.
⚠ Medical Attention: If you or a family member develops severe headache, neck stiffness, and nausea — particularly after spending time in a garden environment or in proximity to snails/slugs — seek emergency medical care immediately and tell the treating physician about potential snail exposure. Mention rat lungworm specifically; it is underdiagnosed in Florida.
Why Are Lakeland and Winter Haven Particularly High-Risk Areas for Rat Lungworm in Florida?
Three factors combine to make the Lakeland-Winter Haven corridor one of the higher rat lungworm risk environments in Florida:
Dense Snail Habitat
The 23 named Lakeland lakes and Winter Haven’s 50+ Chain of Lakes create year-round snail and slug habitat at densities found nowhere else in central Florida. Shoreline gardens, irrigated landscaping, and lakefront mulch beds sustain high snail populations through all 12 months.
High Roof Rat Density
Polk County’s combination of subtropical climate, legacy citrus, and pre-1990 housing stock produces some of the highest residential roof rat densities in Florida. More rats in the environment means more infected snails in lakeside gardens.
Garden Culture
Lakeland’s subtropical climate supports year-round outdoor gardening. Residents who grow vegetables, herbs, and citrus in lakeside gardens have direct, repeated exposure to the snail populations that are most likely to carry A. cantonensis.
How Does Removing Roof Rats From Your Lakeland Home Reduce Rat Lungworm Risk?
Rat lungworm requires an active rat population to maintain its transmission cycle. Rats defecate larvae into the environment; snails and slugs ingest the larvae and become infective; humans accidentally ingest infected snails. Remove the rats from the transmission cycle and the local snail population gradually clears of infective larvae — though this is not immediate (existing infected snails remain infective).
The practical value of permanent roof rat removal for lakeside Lakeland and Winter Haven properties extends beyond structural protection. Eliminating the rat population that maintains the parasite’s transmission cycle in your immediate environment meaningfully reduces your household’s exposure risk over time. This is the primary reason we include attic decontamination as a recommended follow-up for any infestation in close proximity to Polk County lakes.
How Can Lakeland Residents Reduce Personal Rat Lungworm Exposure While an Infestation Is Being Addressed?
Wash All Garden Produce Thoroughly
Scrub all produce grown in lakeside or high-snail-activity areas under running water. Cook root vegetables and leafy greens that contact the soil. Don’t eat raw garden snails under any circumstances.
Supervise Children in Lakeside Gardens
The CDC’s 2021–2022 Florida cases were all children under 5. Geophagia (eating soil) and hand-to-mouth contact in snail-active garden areas are the most likely transmission routes for young children. Supervise and prevent soil ingestion in high-risk outdoor areas.
Inspect Pets’ Food and Water Bowls
Snails and slugs can enter outdoor pet food and water bowls at night, leaving larvae behind even after they’ve moved on. Use covered water bowls or bring them inside overnight if your property has active snail populations.
Frequently Asked Questions — Rat Lungworm Florida
Has anyone in Lakeland specifically been diagnosed with rat lungworm?
No documented Lakeland cases are publicly reported as of our knowledge cutoff. The CDC-confirmed 2021–2022 Florida cases occurred in the Orlando area. However, the parasite is confirmed present in Florida’s roof rat population and snail species throughout the state. Polk County’s combination of high rat density and extensive lake snail habitat represents a real ongoing exposure risk, even without a recorded local case.
Can I get rat lungworm from a rat bite or contact with rat droppings?
No — transmission requires ingesting infected snails or slugs (or snail/slug slime on contaminated produce). Contact with rats, rat droppings, or rat urine does not transmit rat lungworm. However, rat droppings carry other pathogens (Leptospira, Salmonella, Hantavirus precursors) that require separate HEPA cleanup protocols.
Is rat lungworm treatable?
Most infections resolve spontaneously as the parasite cannot complete its lifecycle in humans and eventually dies. Supportive care (pain management, steroids to reduce inflammation) is the primary treatment. Severe infections require hospitalization. There is no specific anti-parasitic drug proven effective for A. cantonensis infection. The CDC and WHO recommend against anthelmintic drugs for this infection, as dying parasites may cause additional inflammatory response.
Should I see a doctor if I suspect rat lungworm infection?
Yes — immediately if you develop the hallmark symptom cluster (severe headache + neck stiffness + nausea) after any potential snail exposure. Tell your doctor specifically about rat lungworm and provide your exposure history. Early corticosteroid treatment can reduce the severity of inflammation. Don’t wait to see if symptoms resolve.
LCWM-Certified Roof Rat Removal — Same or Next Day
No poison · Permanent exclusion · 90-day return protection · Polk County
Rodent Shield Lakeland
3616 Harden Blvd, Lakeland FL 33803 · (863) 238-8082
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