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This study investigates if worm infection or deworming has any relevance to leprosy clinical care. The research group aims to detect risks and associations between helminth indicators, leprosy indicators and clinical outcomes including leprosy reaction development, severity and duration.
Helminth Influences in Leprosy: Indicators, Treatment, Reactions and Clinical Outcome
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Project summary
More than 94% of global new leprosy cases are living in areas endemic for soil-transmitted helminths (STH, intestinal worms). Recent evidence indicates that intestinal worms depress immunity in general, suppressing host capacity to evict or manage other co-infection(s). For instance, current studies now indicate that allergies are more common in developed nations than nations with high rates of intestinal worms [1]. Basically, the worms long-term suppress the inflammatory responses evidenced in allergies.
In Brazilian leprosy patients, intestinal worm infections were more common in those with higher leprosy bacterial loads. Essentially, the worms suppressed the patient’s normal immune defences, likely allowing M. leprae to grow to higher numbers and thereby placing patients at higher risk for complications.
Growing evidence from other diseases such as HIV, tuberculosis and malaria indicate that deworming patients can benefit immune health and restore normal immune responses, although recovery times seem to vary on malnutrition, the specific worm(s), duration and degree of infection and if the patient has any other health conditions. Deworming seems of obvious benefit; however, there is a risk that restored immunity may suddenly overreact with strong inflammation towards co-infections that developed during the time of worm-induced immune suppression [2].
Roughly 30-50% of leprosy patients develop immune complications called leprosy reactions, which often involve inflammation of the skin and nerve. Because the nerves can be permanently damaged, reactions are the major factor for disability development in leprosy. Reactions typically are sudden shifts in the immune response, unpredictable and often requiring months to years of immunosuppressive medications before they resolve.
It is unknown what triggers leprosy reactions. Surprisingly, though, in recent years it was discovered that some arthritis treatments that suppressed immunity long term and then were halted could unmask previously subclinical leprosy by manifesting intense inflammation against leprosy bacteria once immunity was restored. In some African HIV patients, normal immunity had been decimated by the HIV virus over a long period. After receiving immune boosting medications, some unexpectedly manifested a leprosy reaction, intense inflammation by a restored immune system attacking leprosy bacteria that had sought to thrive while HIV kept defences low. Combining these patterns with what is being learned about worm co-infections, the research group proposes that worms and deworming may also be related to signs of leprosy and leprosy reaction development.
Worm co-infection may also be blocking leprosy blood test signals. In Bangladesh, malnourished children with confirmed tuberculosis and worm co-infection more often received unreadable blood test results. This was because their worm infection had suppressed the signals the test was designed to evaluate. Some developing leprosy diagnostics are targeting similar signals. Therefore, the research group also proposes that worm co-infection in leprosy may be silencing or diminishing immune responses that could be detectable by blood test. Deworming suspect leprosy cases before these blood tests and then allowing for immune recovery may allow better readout with improved sensitivity and accuracy.
The main research question is: Are common worm co-infections and deworming relevant to leprosy indicators, clinical care and outcomes?
References:
1. Smits, H.H., et al., Chronic helminth infections protect against allergic diseases by active regulatory processes. Curr Allergy Asthma Rep, 2010. 10(1): p. 3-12.
2. Jackson, J.A., et al., Review series on helminths, immune modulation and the hygiene hypothesis: immunity against helminths and immunological phenomena in modern human populations: coevolutionary legacies? Immunology, 2009. 126(1): p. 18-27.