A recent study assessed whether tungiasis, an inflammatory skin disease caused by sand fleas, can be detected using high-resolution infrared thermography.
Tungiasis, a parasitic skin disease caused by the penetration of female sand fleas, is endemic in many tropical countries across Central and South America, the Caribbean and Sub-Saharan Africa. As this skin disease is highly prevalent in low and middle-income countries, it can quite often be underdiagnosed and untreated. Therefore, there is a need for an easy method to help detect, diagnose, and treat patients.
One suggested technique is high-resolution infrared thermography or thermal imagery which is able to provide a real-time map of skin temperatures. Infrared thermography has been used for various medical purposes in recent times, including the detection of breast cancer or rheumatic diseases, which are characterized by inflammation that affects joints and muscles.
The sand flea burrows into the skin, with 99% of lesions occurring on the feet. Once burrowed under the skin, the fleas cause a build-up of pressure in the surrounding area as they fully develop and increase their body volume by a factor of 2000 within two weeks. This creates redness, swelling, pain, and itchiness which subsequently trigger an acute inflammatory response. Skin temperature rises when inflammation occurs, meaning use of high-resolution infrared thermography can enable instant assessment of inflamed skin.
Typically, many people try to remove the burrowed fleas with needles or pins, which often leads to bacterial superinfections of the lesion. The result is infected skin, or cellulitis, characterized by inflammation, redness, and the formation of pus. These infections can cause severe side effects such as mobility restrictions and tetanus.
In a recent study by Schuster and colleagues published in Tropical Medicine and Health, researchers from Germany, Belgium, Sweden, and Madagascar investigated whether high-resolution infrared thermography could be used to detect and quantify the tungiasis-associated inflammation. They also assessed how quickly inflammation caused by the parasite regressed once the parasite was removed.
Thirty-six tungiasis patients from two rural communities located in Madagascar were included in the study. At the time of the study, the prevalence of tungiasis in the general population of this region was approximately 73%. Clinical examination and infrared thermography or thermal imaging of only the patient’s feet were carried out. Patients had the sand fleas surgically removed by an experienced health professional after a baseline examination was carried out and inflammation regression was assessed 4 days after extraction had occurred.
Results showed that the average temperature surrounding a lesion was 29.5 °C, which was substantially higher compared to the average temperature of 27.1 °C. A positive correlation between the average temperature detected by infrared thermography and the degree of acute and chronic inflammation, including the degree of pain was observed. However, the stage of lesion did not correlate with the temperature of the lesion. Inflammation and temperature surrounding the lesion decreased significantly four days after the sand fleas were surgically removed, with the average temperature of the affected area dropping to 20.9 °C.
Furthermore, early-stage lesions, which previously were hard to detect due to limited signs of inflammation, were able to easily be identified using high-resolution infrared thermography. However, it was noted by the researchers, limitations of this study included interpretation of images produced using infrared thermography is subjective and interpretation is also difficult in patients with extended and multiple lesions. Also, the study was conducted in rural communities in Madagascar which were resource-poor, meaning thermal measurements were not standardized like they would have been in an industrialized hospital setting, resulting in difficulties quantitatively comparing tungiasis-associated inflammation between patients before and after treatment.
Overall, this study provided significant evidence that high-resolution infrared thermography is an effective tool for not only detecting tungiasis-associated inflammation of the skin and the regression of the inflammation after treatment but also help diagnose hidden or early stages of the disease. Researchers used hand-held infrared thermography cameras, which follows the World Health Organisation recommendations to develop innovative methodologies to manage neglected tropical diseases such as tungiasis. Finally, this study suggests that infrared thermography could also be used as a diagnostic tool for potentially detecting and assisting treatment for various other infectious skin diseases prevalent in tropical regions.
Written by Lacey Hizartzidis, PhD
Schuster A, Thielecke M, Raharimanga V, et al. High-resolution infrared thermography: a new tool to assess tungiasis-associated inflammation of the skin. Tropical Medicine and Health. 2017;45:23. doi:10.1186/s41182-017-0062-9.
Tungiasis, Lymphatic Filariasis. World Health Organisation website http://www.who.int/lymphatic_filariasis/epidemiology/tungiasis/en/. Accessed September 25th, 2017.