FILARIA INFECTION : COULD IT BE A CAUSE OF CHRONIC DRY COUGH ?

Background: Management of chronic dry cough is a challenging problem for physicians. A significant proportion of patients remain undiagnosed and not cured for a long period. So this study was undertaken to identify etiology of chronic dry cough. Methods: A prospective study was done in a private center, Dhaka during the period of April 2007-February, 2008 among 80 patients who were suffering from chronic dry cough for more than three months. Results: 80 patients of chronic dry cough were prospectively studied on the basis of history, clinical examination and investigation reports. Among them, (41, 51.25%) were diagnosed as having usual causes of dry cough like cough variant asthma (21, 26.25%), heart Failure (10, 12.5%), sinusitis/post nasal drip (4.5%), gastro esophageal reflux disease (2, 2.5%) and drugACE inhibitor (4,5%). This group of patients improved after treatment of their primary cause except 6 (7.5%), who showed no improvement. These patients and the rest 39 (48.75%) patients did not have any discernible cause of chronic cough. They were evaluated by CFT for filaria. Among them, 20 cases (25%) showed moderate to strongly positive result. This CFT filaria positive group was treated with a combination of ivermectin and albendazole. Patients were followed up for up to four months. Result showed cough was totally absent in 80% treated patients with the rest 20% showing significant improvement. Conclusion: This study advocates that, significant proportion of chronic dry cough patients were actually suffering from occult filaria and they responded well to treatment with drugsivermectin and albendazole combination. 1. Associate Professor, Department of Cardiology, National Institute of Cardiovascular Diseases and Hospital, Dhaka. 2. Honorary Medical officer, National Institute of Chest Diseases and Hospital, Dhaka. 3. Medical Officer, Department of Hepatology, Bangabandhu Sheikh Mujib Medical University, Dhaka. 4. Medical Officer, Department of Medicine, Bangabandhu Sheikh Mujib Medical University, Dhaka. Correspondence: Dr. Abdul Wadud Chowdhury, Associate Professor, Department of Cardiology, National Institute of Cardiovascular Diseases and Hospital, Dhaka. E-mail: drwadud@hotmail.com annually.2 The prevalence of chronic cough is not yet known in our country though chronic cough is commonly encountered by our physicians.3 A significant proportion of these patients remain undiagnosed and not cured for a long period. Management of this group of patients is a challenging issue. This study was done to identity the etiology of chronic dry cough, which persists more than three months of duration. Material and methods: It was a prospective observational study conducted in a private center in Dhaka during the period of April 2007February 2008. A total of 80 adult patients fulfilling the inclusion and exclusion criteria were ORIGINAL ARTICLES J MEDICINE 2009; 10 : 3-6

annually. 2 The prevalence of chronic cough is not yet known in our country though chronic cough is commonly encountered by our physicians. 3A significant proportion of these patients remain undiagnosed and not cured for a long period.Management of this group of patients is a challenging issue.This study was done to identity the etiology of chronic dry cough, which persists more than three months of duration.

Material and methods:
It was a prospective observational study conducted in a private center in Dhaka during the period of April 2007-February 2008.A total of 80 adult patients fulfilling the inclusion and exclusion criteria were enrolled in the study.Inclusion criteria were dry cough lasting 3 months or more without any significant history of occupational exposure to organic/inorganic dust, fever, haemoptysis.Exclusion criteria were patients of pulmonary TB, bronchial carcinoma and interstitial lung disease.The patients were examined thoroughly.Then following routine laboratory investigations were donetotal and differential count of WBC, Hb%, ESR, total circulating eosinophil count, sputum for eosinophil count, CXR P/A view, ECG, RBS, serum creatinine.Selective investigations like X-ray PNS OM view, upper GI endoscopy, echocardiogram-(2D/Colour Doppler), lung function test, methacholine challenge test and CFT for filaria were also done as needed.
Thus after primary evaluation, 41 patients were diagnosed as having usual causes of dry cough like cough variant asthma 21(26.25%),heart failure 10(12.5%),sinusitis/post nasal drip 4(5%), gastroesophageal reflux disease-GERD 2(2.5%) and drug-ACE inhibitor 4(5%).The rest 39(48.75%)patients remain undiagnosed.The diagnosed group improved after treatment of their primary cause except 6(7.5%) patients.These 6 and the rest 39 patients did not have any discernible cause of persistent cough.They were then evaluated by CFT for Filaria.Among them 20 cases (6 old + 14 new) showed moderate to strongly positive result for CFT Filaria.
This CFT filaria positive group was treated with a combination of ivermectin and albendazole.Ivermectin 400ug/kg -single dose in empty stomach half an hour before meal & albendazole 400mg,twice daily for 5 days after meal.Patients were followed up for up to four months (mean 3.2 months).

Discussion:
In Bangladesh, prevalence of chronic cough is not known, though it is a commonly encountered complaint.A systematic diagnostic approach based on history, clinical examination and a number of investigations reveal the cause in most cases. 4The commonest causes are PNDS (post nasal drip syndrome), asthma, GERD, chronic bronchitis and ACE inhibitor induced cough. 5These conditions often coexist and may simultaneously contribute to cough.A combination of treatments are necessary for managing these cough. 6Patients with chronic cough present more of a diagnostic challenge, specially those individual with a normal examination, chest X-ray and lung function studies.The main objective of this study was to identify the etiologies of chronic dry cough.
The study showed that clearly identifiable causes of chronic dry cough were present in about half of the patients (51.25%).Among the rest, 25% more were identified as cases of occult filaria infection.This finding is important because this group of patients did not show the classical features of tropical pulmonary eosinophilia.
In this study, our close observation showed that occult filaria infected persons complained of chronic dry cough in the absence of other significant symptoms.They, therefore, remained undiagnosed for a long period.This identified occult filaria group was treated with a combination of ivermectin and albendazole.In comparative study of ivermectin and DEC -the two drugs were found to be equally efficacious in reducing microfilaria burden. 8Combination of ivermectin & albendazole is under evaluation as an alternative of DEC. 9 Ivermectin kills the parasite by interfering with nervous system and muscle function, in particular by enhancing inhibitory neurotransmission.The drug binds and activates glutamate-gated chloride channels (GluCls) present in neurons and myocytes -resulting in neuro-muscular paralysis and death of parasite. 10ide effects are nausea, vomiting, decreased appetite, diarrhoea or constipation, muscle or joint pain, swelling of lymph node, fever, tiredness, dizziness, itching.On the other hand albendazole is slow macrofilaracidal and microfilaracidal.Dose for microfilaria is 400mg-single dose and for macrofilaria 400mg-twice daily for 3 weeks.A comparative study using a single dose of albendazole 600 mg alone or in combination with ivermectin 400 micrograms/kg or DEC 6 mg/kg was compared with a single dose of the combination DEC and ivermectin has established the tolerability, safety and efficacy against bancroftian filariasis. 11Side effects of DEC are more common & relatively serious-fever, headache, myalgia, dizziness, allergic reaction, anorexia, vomiting, urticaria, asthmatic attack, cough, chest pain etc. Close observation showed the combination of ivermectin and albendazole is cheap and less toxic.We found the same in our study.The side effects were much lower probably due to less disease burden.The dosage we have used -ivermectin 400 µg/kgsingle dose & albendazole 400-twice daily for 5 days is an empirical one.But the results showed that it was very effective & well tolerated.Follow up showed this combination is effective too.However one significant finding is that at least one-third patients (31.25%) still remain undiagnosed.

Conclusion:
In this study, we have identified that occult filarial infection is the cause of chronic dry cough in a significant number (25%) of patients.We also showed that a combination of ivermectin & albendazole is an effective, cheap & very well tolerated regime for this group of patients.However, with all these efforts onethird patients of chronic dry cough still remain undiagnosed.Further study is therefore needed to elucidate other yet unidentified factors responsible for chronic cough.

Table - I
The presenting symptoms of study population (n=80)