Infections that mimic TB

HEALTH

TUBERCULOSIS is a potentially serious infectious disease that mainly affects the lungs. Mycobacterium tuberculosis, the bacteria that causes the disease is spread from person to person through tiny droplets released into the air via coughs and sneezes. As an ancient disease, it was present in Egypt from as early as 3700 BC. And even to date, it is a major global public health concern, with more than 2 billion people infected worldwide. About a third of world’s population is affected by tuberculosis.
When it affects the lungs, signs and symptoms of active tuberculosis include, coughing, coughing up blood or mucus, chest pain, or pain with breathing or coughing, weight loss, fatigue, fever, night sweats, chills, and loss of appetite.
Tuberculosis can also affect other parts of your body, including the kidneys, spinal cord or brain. When tuberculosis occurs outside the lungs, signs and symptoms vary according to the organs involved. For example, tuberculosis of the spine might cause back pain, whilst tuberculosis affecting kidneys might cause presence of blood in urine.
One other medical condition that produces very similar signs and symptoms to that of tuberculosis is paragonimiasis. It is a food-borne parasitic infection caused by a family of lung flukes called Paragonimus. It is particularly common in East Asia, Africa, and South America and infects an estimated 22 million people worldwide every year. The first reported case of paragonimiasis or human lung fluke was in 1879 in Taiwan, which was attributed to the findings of adult worms in the lungs of a dead Taiwanese.
There are more than 30 known species of Paragonimus, and of which, eight have been reported to cause infections in humans. They are widely distributed in Asia, Africa, and North and South America, with Paragonimus westermani found in southeast Asia and Japan, Paragonimus kellicotti being endemic to North America, Paragonimus africanus found in Africa, whilst Paragonimus mexicanus endemic in Central and South America.
Just as the species names imply, paragonimiasis is endemic in Asian, African, and Hispanic communities because of their cultural practices and habits.
Fresh water crabs, crayfish, as well as snails act as first and second intermediate hosts, respectively. Humans acquire infection mostly by consuming uncooked or undercooked crabs and crayfish containing mature eggs of the parasite.
The parasites primarily infect the lung, but infection of other organs may also be encountered. Like tuberculosis, paragonimiasis can also involve other systems such as the brain and spinal cord, the stomach and intestines, the muscles and bones, and the skin.
In most of the endemic areas of paragonimiasis, the majority of the infections involve the lungs. Pulmonary paragonimiasis is usually characterised by persistent cough, bloody sputum, and nodular ring shadows in the lung by chest X-ray.
However, other additional features such as massive pleural effusion (fluid around lungs) without pulmonary infiltration have been described. This may indicate early stage of the parasitic infection. The laboratory diagnosis of Paragonimiasis is by microscopic demonstration of Paragonimus egg in the sputum and other specimens, such as, stool, and from fluid taken from around the lungs.
Generally speaking, a high level of suspicion is necessary to diagnose paragonimiasis. Suggestive diagnostic features are the, person’s residence in a known endemic area, the long period of chronic cough, the relative well-being of patient, and habit of eating raw, undercooked, or uncooked crabs or crayfish, and most probably, tuberculosis negative test or treatment failure.
Diagnosis of paragonimiasis is confirmed when eggs of the causative parasite are detected in the sputum, stool, bronchoscopic washing, biopsy specimen, or pleural effusion. However, diagnosis is generally delayed due to lack of suspicion and presentation of signs and symptoms being very similar to tuberculosis, which is endemic in many populations globally. Thus, exclusion of tuberculosis is of equal importance in suspected paragonimiasis cases.
It is not an understatement that paragonimiasis and tuberculosis are overlapping public health issues in many countries in the world. Tuberculosis is a dramatic recurring public health problem due to its long association with poverty, acquired immune deficiency syndrome, and multiple drug resistance. In contrast, paragonimiasis is generally accorded little significance on the global health agenda although about 22 million people are estimated to be infected.
These are both pulmonary diseases with similar clinical manifestations, especially, hemoptysis. Increased reporting of this disease in Europe and the Americas has been attributed to changes in migration patterns, refugee movement, and tourism.
Pulmonary tuberculosis and paragonimiasis remain as health problems in certain areas of the world. Both share similar clinical manifestations, which include chronic productive cough, hemoptysis, dyspnea, fever, weight loss, and night sweats.
The diagnosis of pulmonary paragonimiasis should be considered in patients from endemic regions presenting with symptoms and radiological features which may mimic pulmonary tuberculosis. The presence of a positive dietary history, negative tuberculosis laboratory tests, and lack of response to anti-tuberculosis therapy should prompt a revision of diagnosis. Given its similarities in clinical presentation, paragonimiasis should be considered as a high possibility in such clinical cases.
Source of information
Toscano, C, et. al. 1994, Paragonimiasis and tuberculosis – Diagnostic confusion: A review of literature, World Health Organization, viewed 02 March 2022, https://www.apps.who.int
Paragonimiasis, Wikipedia, viewed 08 May 2022, https://www.en.m.wikipedia.org

• Gelinde Narekine is a technical officer with the Discipline of Medical Laboratory Science, Division of Health Sciences, School of Medicine and Health Sciences, University of Papua New Guinea.