Poulle Marie-Lazarine, Le Corre Matthieu, Bastien Matthieu, Gedda Elsa, Feare Chris, Jaeger Audrey, Larose Christine, Shah Nirmal, Voogt Nina, Göpper Byron, Lagadec Erwan, Rocamora Gérard, Geers Régine, Aubert Dominique, Villena Isabelle, Lebarbenchon Camille
Epidémio-Surveillance et Circulation des Parasites dans les Environnements (ESCAPE), EA 7510, CAP SANTE, Université de Reims Champagne Ardenne, Reims, France.
CERFE, Université de Reims Champagne-Ardenne, Boult-aux-Bois, France.
PLoS One. 2021 Aug 18;16(8):e0255664. doi: 10.1371/journal.pone.0255664. eCollection 2021.
Toxoplasma gondii is a protozoan parasite that uses felids as definitive hosts and warm-blooded animals as intermediate hosts. While the dispersal of T. gondii infectious oocysts from land to coastal waters has been well documented, transmission routes to pelagic species remain puzzling. We used the modified agglutination test (MAT titre ≥ 10) to detect antibodies against T. gondii in sera collected from 1014 pelagic seabirds belonging to 10 species. Sampling was carried out on eight islands of the Western Indian Ocean: Reunion and Juan de Nova (colonized by cats), Cousin, Cousine, Aride, Bird, Europa and Tromelin islands (cat-free). Antibodies against T. gondii were found in all islands and all species but the great frigatebird. The overall seroprevalence was 16.8% [95% CI: 14.5%-19.1%] but significantly varied according to species, islands and age-classes. The low antibody levels (MAT titres = 10 or 25) detected in one shearwater and three red-footed booby chicks most likely resulted from maternal antibody transfer. In adults, exposure to soils contaminated by locally deposited oocysts may explain the detection of antibodies in both wedge-tailed shearwaters on Reunion Island and sooty terns on Juan de Nova. However, 144 adults breeding on cat-free islands also tested positive. In the Seychelles, there was a significant decrease in T. gondii prevalence associated with greater distances to cat populations for species that sometimes rest on the shore, i.e. terns and noddies. This suggests that oocysts carried by marine currents could be deposited on shore tens of kilometres from their initial deposition point and that the number of deposited oocysts decreases with distance from the nearest cat population. The consumption of fishes from the families Mullidae, Carangidae, Clupeidae and Engraulidae, previously described as T. gondii oocyst-carriers (i.e. paratenic hosts), could also explain the exposure of terns, noddies, boobies and tropicbirds to T. gondii. Our detection of antibodies against T. gondii in seabirds that fish in the high sea, have no contact with locally contaminated soils but frequent the shores and/or consume paratenic hosts supports the hypothesis of an open-sea dispersal of T. gondii oocysts by oceanic currents and/or fish.
刚地弓形虫是一种原生动物寄生虫，它以猫科动物作为终末宿主，以温血动物作为中间宿主。虽然刚地弓形虫感染性卵囊从陆地扩散到沿海水域已有充分记录，但向远洋物种的传播途径仍令人费解。我们使用改良凝集试验（MAT滴度≥10）检测了从属于10个物种的1014只远洋海鸟采集的血清中针对刚地弓形虫的抗体。采样在西印度洋的八个岛屿上进行：留尼汪岛和新胡安岛（有猫栖息）、库辛岛、库辛内岛、阿里德岛、伯德岛、欧罗巴岛和特罗梅林岛（无猫）。除了大军舰鸟外，在所有岛屿和所有物种中都发现了针对刚地弓形虫的抗体。总体血清阳性率为16.8%[95%置信区间：14.5%-19.1%]，但根据物种、岛屿和年龄组有显著差异。在一只剪水鹱和三只红脚鲣鸟雏鸟中检测到的低抗体水平（MAT滴度=10或25）很可能是由于母源抗体转移。在成年鸟中，接触当地沉积卵囊污染的土壤可能解释了在留尼汪岛的楔尾剪水鹱和新胡安岛的黑燕鸥中检测到抗体的原因。然而，在无猫岛屿上繁殖的144只成年鸟检测结果也呈阳性。在塞舌尔，对于有时在岸边休息的物种，即燕鸥和黑燕鸥，刚地弓形虫的流行率与离猫种群的距离增加有显著下降。这表明洋流携带的卵囊可能在离其初始沉积点数十公里的海岸沉积，并且沉积的卵囊数量随着离最近猫种群的距离增加而减少。食用先前被描述为刚地弓形虫卵囊携带者（即转续宿主）的鲱科、鲹科、鲱形目和鳀科鱼类，也可以解释燕鸥、黑燕鸥、鲣鸟和热带鸟接触刚地弓形虫的原因。我们在公海捕鱼、不接触当地污染土壤但经常在岸边活动和/或食用转续宿主的海鸟中检测到针对刚地弓形虫的抗体，这支持了刚地弓形虫卵囊通过洋流和/或鱼类在公海扩散的假说。
