Flach Edmund J, Dodhia Hasita S, Guthrie Amanda, Blake Damer P
Wildlife Health Services, Zoological Society of London, Regents Park, London NW1 4RY, United Kingdom,
Wildlife Health Services, Zoological Society of London, Regents Park, London NW1 4RY, United Kingdom.
J Zoo Wildl Med. 2022 Mar;53(1):70-82. doi: 10.1638/2021-0087.
Infection with systemic species (systemic isosporiasis [SI]) is common in passerine birds and may cause substantial mortality in zoological collections. Ten years of postmortem records of 26 species of captive, nonnative passerine birds maintained at the Zoological Society of London, London Zoo, plus seven free-ranging species found dead within the zoo, were reviewed to assess cause of death and occurrence of SI (presence of merozoites in tissue impression smears and/or polymerase chain reaction [PCR] testing for DNA). The records of 287 juveniles and adults were reviewed, of which 161 had SI test results. The most common cause of death was physical (trauma, predation, drowning, and hypothermia), diagnosed in 39.0% of cases. Virulent SI was considered the cause of death in only nine individuals from five species (3.1% of all cases, 5.6% of tested birds). However, merozoites were recorded in 36.0% of the 150 individuals examined cytologically (representing 18 of the 33 species), while 45.3% of 53 spleen samples (14 species) were positive for DNA. Test agreement for the 42 birds tested by both methods was 69.0%. Assuming that the PCR result was correct in these, 37.9% of the 161 birds (21 species) were positive for SI at the time of death. These figures might underestimate prevalence because of poor DNA preservation and low numbers of individuals of some species tested. Eight new 28S rDNA sequences and 12 new internal transcriber spacer 1/2 sequences were amplified. Sequences from individuals of the same host species clustered together, suggesting a single species, and there was no evidence of overlap among hosts. These results confirm that systemic infection with species in zoo passerines is generally of low pathogenicity and most likely coevolved with their hosts. Severe disease may occur, however, with overwhelming exposure, secondary to immunosuppression, or following coinfection with another pathogen.
全身性等孢球虫物种感染（全身性等孢球虫病[SI]）在雀形目鸟类中很常见，可能会在动物园的圈养种群中导致大量死亡。回顾了伦敦动物学会伦敦动物园饲养的26种圈养外来雀形目鸟类以及在动物园内发现死亡的7种自由放养鸟类的十年尸检记录，以评估死亡原因和SI的发生情况（组织印片涂片中有裂殖子和/或进行DNA的聚合酶链反应[PCR]检测）。审查了287只幼鸟和成年鸟的记录，其中161只进行了SI检测。最常见的死亡原因是身体因素（外伤、捕食、溺水和体温过低），在39.0%的病例中被诊断出。仅在来自五个物种的九只个体中，强毒SI被认为是死亡原因（占所有病例的3.1%，检测鸟类的5.6%）。然而，在150只接受细胞学检查的个体中，36.0%记录到了裂殖子（代表33个物种中的18个），而53个脾脏样本（14个物种）中有45.3%的DNA呈阳性。通过两种方法检测的42只鸟类的检测一致性为69.0%。假设这些鸟类中PCR结果正确，那么161只鸟类（21个物种）中有37.9%在死亡时SI呈阳性。由于DNA保存不佳以及某些物种检测个体数量较少，这些数字可能低估了患病率。扩增了8个新的28S rDNA序列和12个新的内部转录间隔区1/2序列。来自同一宿主物种个体的序列聚集在一起，表明是单一物种，且没有宿主间重叠的证据。这些结果证实，动物园雀形目鸟类中全身性等孢球虫物种感染通常致病性较低，很可能与其宿主共同进化。然而，在接触过多、继发于免疫抑制或与另一种病原体合并感染后，可能会发生严重疾病。
