ConditionLungs & breathing
Tropical Pulmonary Eosinophilia
Tropical pulmonary eosinophilia (TPE) is an allergic-type lung condition caused by the body's immune reaction to filarial worms, mainly Wuchereria bancrofti and Brugia malayi, which are spread by mosquitoes. It mostly affects people who live in or have spent months in South and Southeast Asia, parts of Africa and other tropical regions. It causes a cough and wheeze that are worse at night, mimicking asthma, along with very high eosinophil counts in the blood. It responds well to the antiparasitic drug diethylcarbamazine (DEC).
Also called: TPE, tropical eosinophilia, Weingarten syndrome, filarial pulmonary eosinophilia
At a glance
- What it is
- A hypersensitivity lung reaction to filarial parasites.
- Where
- India, Sri Lanka, Southeast Asia, parts of Africa, South America and Pacific islands.
- Who
- Mostly young adult men; also long-stay travelers and migrants.
- Symptoms
- Night-time cough, wheeze, breathlessness, low fever, tiredness, weight loss.
- Diagnosis
- Eosinophils usually over 3,000 per microliter, very high IgE, high antifilarial antibodies, and response to DEC.
- Treatment
- Diethylcarbamazine (DEC) for about 2 to 3 weeks; steroids sometimes added.
When to get help
Call 911 or go to the ER
- Severe breathlessness, blue lips or inability to speak in full sentences
See a doctor within a day or two
- Worsening breathlessness or coughing blood
- Fever, cough and wheeze that are getting worse despite asthma inhalers
Book a routine appointment
- A cough or wheeze, worse at night, that started after living in or traveling to a tropical region
- "Asthma" that does not respond well to usual treatment, especially with a very high eosinophil count on a blood test
- Unexplained weight loss and tiredness with cough after time in the tropics
What causes it
Lymphatic filariasis is a parasitic infection spread by mosquito bites. In most infected people, the larvae mature into adult worms in the lymphatic system, which can later cause lymphedema ("elephantiasis"). In TPE, the immune system reacts very strongly to the microfilariae (the larval stage). The microfilariae are trapped and destroyed in the lungs, triggering intense inflammation with large numbers of eosinophils, a type of white blood cell involved in allergy and parasite defense. As a result, microfilariae are usually not found in the blood.
TPE accounts for only a small fraction of filarial infections.
Symptoms
- a dry, hacking cough, worse at night
- wheezing and chest tightness
- shortness of breath
- low-grade fever
- tiredness, loss of appetite and weight loss
- sometimes swollen lymph nodes or an enlarged liver and spleen
Because these symptoms resemble asthma, TPE is often misdiagnosed, particularly in non-endemic countries.
Diagnosis
| Test | Typical finding in TPE |
|---|---|
| Blood eosinophil count | Very high, usually over 3,000 cells per microliter |
| Total IgE | Markedly raised, often over 1,000 IU/mL |
| Antifilarial antibodies (IgG, IgE) | High |
| Blood smear for microfilariae | Usually negative |
| Chest X-ray | Diffuse small nodules or streaky shadows; can be normal |
| CT chest | Small nodules, airway thickening |
| Lung function tests | Mixed obstructive and restrictive pattern, reduced gas transfer |
| Bronchoalveolar lavage | Very high eosinophils |
| Response to DEC | Rapid clinical and laboratory improvement supports the diagnosis |
Stool tests and other investigations rule out other causes of eosinophilia, such as strongyloides, other worms, drug reactions, allergic bronchopulmonary aspergillosis, eosinophilic pneumonia, eosinophilic granulomatosis with polyangiitis and hypereosinophilic syndrome. Testing for strongyloides is important before any steroid treatment, because steroids can trigger a severe strongyloides infection.
Treatment
- diethylcarbamazine (DEC): the treatment of choice, usually for 14 to 21 days. Most patients improve within a week or two. In the US, DEC is available through the CDC
- corticosteroids: sometimes added for severe symptoms or persistent inflammation
- repeat courses for relapses, which occur in a minority of patients
- ivermectin and other antifilarial drugs are used in some settings, sometimes in combination; specialist advice is recommended
Complications
If untreated, TPE can progress to chronic lung damage with interstitial fibrosis (scarring), permanently reducing lung function and causing persistent breathlessness. Early diagnosis and treatment prevent this.
Prevention
- avoid mosquito bites: insect repellent, long sleeves and trousers, bed nets, screened accommodation
- community mass drug administration programs, coordinated by the WHO, aim to eliminate lymphatic filariasis
Frequently asked questions
What is tropical pulmonary eosinophilia?
It is a lung condition caused by an intense immune reaction to filarial worms spread by mosquitoes in tropical regions. It causes night-time cough, wheezing and very high eosinophil counts in the blood.
How is tropical pulmonary eosinophilia different from asthma?
Both cause cough and wheeze, but TPE occurs after living in or visiting filariasis-endemic areas, is associated with very high eosinophils and IgE, high antifilarial antibodies, and responds to the antiparasitic drug DEC rather than only to asthma inhalers.
How is tropical pulmonary eosinophilia treated?
The main treatment is diethylcarbamazine (DEC), usually taken for 2 to 3 weeks. Steroids may be added for severe inflammation. Most patients improve quickly, though some need repeat courses.
Can tropical pulmonary eosinophilia cause permanent lung damage?
Yes, if it goes untreated for a long time, it can cause lung scarring (fibrosis) and permanent breathing problems. Prompt diagnosis and treatment with DEC usually prevents lasting damage.
Sources
This guide was written from current patient and clinical guidance, including:
- CDC: Lymphatic filariasis: clinical overview
- World Health Organization: Lymphatic filariasis fact sheet
- Merck Manual Professional Version: Tropical pulmonary eosinophilia
- European Respiratory Journal: Tropical pulmonary eosinophilia review
- MedlinePlus: Eosinophil count