Dr Mrinalini Das, epidemiologist and operational researcher, Doctors Without Borders/ Médecins Sans Frontières (MSF), takes a closer look at TB mimicking paragonimiasis, its symptoms, diagnosis and treatment.
You led a research titled, “Paragonimiasis in tuberculosis patients in Nagaland, India”. What is paragonimiasis? How does it mimic TB?
Paragonimiasis (PRG) is a food-borne parasitic disease caused by lung flukes of the genus Paragonimus. Paragonimus infection is caused after consumption of raw or insufficiently cooked freshwater crustaceans (crabs and crayfish) containing encysted metacercariae of the parasite. Tuberculosis and paragonimiasis diseases are similar in clinical presentation including chronic cough, dyspnoea, haemoptysis and chest pain; thus paragonimiasis mimics TB.
How is paragonimiasis treated?
The current recommended regimen for treatment of paragonimiasis is a three-day short course with praziquantel. Mass triclabendazole administration may be preferred in communities where cases of PRG are significantly clustered.
How can medical practitioners effectively differentiate between TB and paragonimiasis? Could you please list the three biggest challenges you faced while the study was undertaken?
Though the clinical presentation of TB and PRG are similar, residence in PRG-endemic area and history of consumption of infected crustaceans (crabs and crayfish) will call for laboratory and clinical investigations for TB and PRG. Further, when patients already on TB medications fail to show clinical improvement, it may hint towards PRG infection.
There were few challenges during the study. First, it took a lot of effort and time to understand the food culture and consumption pattern of the patients, to elicit history of undercooked crab consumption. Second, patients were already enrolled for TB treatment and showed non-improvement under TB treatment, and thus required further diagnosis for PRG. Third, due to difficult terrain and remote setting, additional efforts were required for follow-up of these patients during the treatment.
What did you do to mitigate these challenges?
Local counsellors and nurses were trained for the study to assist in providing appropriate information about PRG and TB disease/treatment to the patients and collect required information for the study. For early and accurate diagnosis, a diagnostic and treatment algorithm was introduced for all presumptive TB patients; and clinical/laboratory evaluations for PRG and TB were simultaneously carried out for these patients with history of consumption of crustaceans. In addition to adherence counselling to patients, counselling and treatment information was provided to their family members during the treatment duration.
What were the biggest lessons learnt from the study?
The TB clinical algorithms are being revised in most affected countries to reflect new tools allowing an accurate diagnosis, new drugs and treatment regimens. However, accurate diagnosis continues to be challenging as TB is a multi-systemic disease with myriad manifestations; it may masquerade as many other diseases or conditions and thus differential diagnosis based on the local epidemiology is essential. In TB-PRG dual burden areas, PRG may be integrated into the TB diagnostic algorithms as misdiagnosis of PRG may not only delay the initiation of appropriate treatment but also pose an unnecessary burden of long and toxic TB treatment on the patient.
What are the findings of the study?
In the MSF-supported TB programme in Mon district (2012-2013), 96 patients who had given consent were screened, of whom three (3%) had pulmonary PRG, including one with HIV co-infection. Of the three PRG patients, two had smear-positive TB with no improvement in clinical condition with TB treatment; however, the third was diagnosed as smear-negative TB. Subsequent treatment with praziquantel led to substantial improvement of symptoms and eventually to cure among all three patients.
A simple TB-PRG diagnostic and treatment algorithm using a limited number of diagnostic tests (sputum smear, stool examination for children<15 years and ELISA) and medicines was prepared. This was being used for all presumptive TB patients, with history of crustacean (crabs & crayfish) consumption in PRG-endemic areas.