Simple Summary Currently, the Eurasian red squirrel ( Sciurus vulgaris ) is the only known wild rodent detected with Mycobacterium leprae and M. lepromatosis infection and serves as a potential maintenance host for these mycobacteria. Studies have detected leprosy bacilli in red squirrels from around the British Isles. However, red squirrels on the European mainland have not been shown to be infected with leprosy bacillus. To gain further insight into presence of leprosy bacilli in red squirrels in the northern UK, this study utilized samples from opportunistically collected red squirrel carcasses found since 2004. To specifically detect the presence of M. leprae and M. lepromatosis DNA, squirrel pinna was assayed by real-time PCR (qPCR). Additionally, we investigated whether specific antibodies directed against leprosy bacilli were present in blood/body cavity fluid from these and other animals. The rate of detection of either of these bacilli in the sampled red squirrels was 22.6%, indicating that leprosy bacilli remain present in the northern UK red squirrel population. Therefore, continuous monitoring for the presence of leprosy bacilli in red squirrels, using macroscopic examination alongside both molecular and serological assays, as well as further research to elucidate the ecology of the disease, is recommended. Abstract Leprosy is a poverty-associated infectious disease in humans caused by Mycobacterium leprae or M. lepromatosis , often resulting in skin and peripheral nerve damage, which remains a significant public health concern in isolated areas of low- and middle-income countries. Previous studies reported leprosy in red squirrels in the British Isles, despite the fact that autochthonous human cases have been absent for centuries in this region. To investigate the extent of M. leprae and M. lepromatosis presence in wild red squirrels in the northern UK, we analyzed 220 blood/body cavity fluid samples from opportunistically sampled red squirrels (2004–2023) for specific antibodies against phenolic glycolipid-I, a cell wall component specific for these leprosy bacilli. Additionally, we assessed bacillus-derived DNA by real-time PCR (qPCR) in 250 pinnae from the same cohort. M. lepromatosis and M. leprae DNA were detected by qPCR in 20.4% and 0.8% of the squirrels, respectively. No cases of co-detection were observed. Detectable levels of anti-PGL-I antibodies by UCP-LFA were observed in 52.9% of animals with the presence of M. lepromatosis determined by qPCR, and overall in 15.5% of all animals. In total, 22.6% ( n = 296) of this UK cohort had at least some exposure to leprosy bacilli. Our study shows that leprosy bacilli persist in red squirrels in the northern UK, emphasizing the necessity for ongoing molecular and serological monitoring to study leprosy ecology in red squirrels, gain insight into potential zoonotic transmission, and to determine whether the disease has a conservation impact on this endangered species.
【저자키워드】 DNA, Real-time PCR, Mycobacterium leprae, leprosy, Mycobacterium lepromatosis, red squirrel, UCP-LFA, anti-PGL-I antibody,