02902nas a2200241   4500000000100000008004100001260004600042653002300088653003100111653002100142100001600163700001600179700001200195700001200207700001200219700001700231700001600248700001600264245012200280490000700402520223700409022001402646       2021                            d  bAmerican Association of Zoo Veterinarians10aGeneral Veterinary10aAnimal Science and Zoology10aGeneral Medicine1 aSchilling A1 avan Hooij A1 aLurz PW1 aShaw DJ1 aGeluk A1 aCorstjens PL1 aStevenson K1 aMeredith AL00aClinical progression of leprosy in Eurasian red squirrels (Sciurus vulgaris) in a naturally infected wild populations0 v523 a<p>Leprosy has been described in Eurasian red squirrel (<em>Sciurus vulgaris</em>; ERS) carcasses since 2014. Studies of ERS carcasses have not provided information about incubation or disease progression in this host but have provided important insights into pathogen presence and distribution throughout the United Kingdom. Here we present field study data on 31 live ERS from an island population naturally infected with&nbsp;<em>Mycobacterium leprae</em>&nbsp;that were assessed longitudinally over a 2-yr time period. Clinical assessment, serologic (anti-phenolic glycolipid-I antibody [αPGL-I] detection) and molecular methods (polymerase chain reaction) were used to diagnose and categorize ERS at each assessment as a leprosy case, a leprosy suspect, colonized by&nbsp;<em>M. leprae</em>, or a contact ERS. Eight ERS (25.8%) were identified as leprosy cases: four at initial assessment, two at 6 mon and two at 24 mon after initial assessment. One ERS was categorized a leprosy suspect when it developed typical lesions 12 mon after initial assessment, despite negative serologic and molecular test results at this time, though&nbsp;<em>M. leprae</em>&nbsp;DNA had been isolated during the initial assessment. Seven ERS (22.6%) were categorized as colonized and of these, six were reassessed but did not develop clinical signs of leprosy within 6 (<em>n</em>&nbsp;= 2), 12 (<em>n</em>&nbsp;= 3), and 18 (<em>n</em>&nbsp;= 1) mon. Most (48.4%,&nbsp;<em>n</em>&nbsp;= 15) were categorized as contact ERS. Progression of leprosy lesions varied between ERS, but always increased in severity over time and was paralleled with increased antibody response. Based on our dataset, we propose the hypotheses: 1) leprosy in ERS is a chronic, slowly progressing disease in this species, similar to that described for other hosts; 2) lesions can undergo repeated ulceration-healing cycles; and 3) in some instances&nbsp;<em>M. leprae</em>&nbsp;DNA and αPGL-I antibodies are detectable before the onset of clinical signs of disease. Future studies addressing the progression of leprosy in ERS should follow affected animals over a longer time period and include tissue samples to pair molecular diagnostics with serologic results.</p>
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