Identifying Active Paragonimiasis in Rural Nagaland in Northeastern India- a Community-Based Cross-Sectional Study

Background

Paragonimiasis is a neglected tropical disease (NTD) and of significant public health concern in northeastern India where it is frequently misdiagnosed as pulmonary tuberculosis. Transmission occurs through consumption of raw or undercooked freshwater crustaceans, a widespread dietary practice in this region. Accurate diagnosis will ensure cheap, effective treatment with praziquantel and avoid unnecessary prolonged tuberculosis therapy. This study determines the prevalence, specific risk factors for infection, and showcases a clinical scoring model to screen for active paragonimiasis in endemic areas.

Methodology/Principal Findings

A community-based cross-sectional survey was conducted in Medziphema block, Nagaland, in northeastern India screening 2,942 residents aged over 10 years. Participants reporting chronic cough (≥2 weeks) provided sputum and serum samples (93,3.16%). Sputum examination was screened for Paragonimus ova and acid-fast bacilli, and serum samples were tested for IgG antibodies against Paragonimus heterotremus using anti-Extra Secretory antigen by ELISA (positive case defined as titre ≥0.5 IU). IgG-confirmed paragonimiasis was detected in 30 individuals, yielding a population prevalence of 1.02% (30/2942) and 32.3% (30/93) amongst symptomatic participants. Sputum microscopy demonstrated limited sensitivity (3.3%), detecting cysts in only one confirmed case. Tuberculosis co-infection was documented in 6.7% of sero-positive cases. Multivariable regression identified significant associations with increasing age (adjusted (aOR) 1.04) previous tuberculosis history (aOR 4.62), monthly snail consumption frequency (aOR 1.05), ever smoking (aOR 3.51), and education beyond middle school (aOR 2.93). Haemoptysis (aOR 9.86) was the strongest symptomatic predictor. Clinical scoring models were developed, with haemoptysis consistently emerging as the most robust predictor across all models.

Conclusions/Significance

Pulmonary paragonimiasis constitutes a prevalent yet under-recognised condition in several southeast-Asian communities, necessitating systematic screening as a differential diagnosis for pulmonary tuberculosis. The clinical scoring model facilitates early case identification in resource-constrained settings. Public health interventions must address dietary practices, particularly consumption of raw or undercooked freshwater crustaceans, to interrupt transmission.

AUTHOR SUMMARY

“Paragonimiasis is a lung infection acquired by eating raw or undercooked crabs, prawns, or snails, a dietary practice in parts of Northeast India. Because its symptoms closely resemble pulmonary tuberculosis, many patients are misdiagnosed and receive prolonged TB treatment instead of a short course of praziquantel. We assessed how common active paragonimiasis is in rural Nagaland and identified factors linked to infection.

We surveyed 2,942 people in Medziphema Block and tested those with cough lasting at least 2 weeks. Active paragonimiasis was confirmed in 30 participants, giving a community prevalence of 1.02%, and in 32.3% of those with persistent cough. The disease was strongly linked to eating snails frequently, previous tuberculosis diagnosis (likely misdiagnosis), smoking, and older age. The standard sputum tests detected the infection in only 3% of cases.

A simple scoring system developed with just four questions, that health workers in remote clinics can use to identify people who need further testing.

These findings show that paragonimiasis is an important but overlooked cause of chronic cough in Nagaland. Simple clinical screening tools may help identify patients who need confirmatory testing. Public health efforts should promote safer preparation of freshwater crustaceans while respecting these deeply rooted cultural food traditions.”