Ruiz A, Frenkel J K
Am J Trop Med Hyg. 1980 Nov;29(6):1161-6. doi: 10.4269/ajtmh.1980.29.1161.
Toxoplasma gondii was isolated from 3.5% of 202 Mus musculus, 12.5% of 120 Rattus norvegicus, 16% of 106 sparrows (Zonotrichia capensis), and from 54% of 50 chickens from Costa Rica. The infection rate in chickens increased from 23% in those weighing less than 500 g, to 73% in those between 500 and 1,000 g, indicating a rapid rate of acquiring infectin, probably from the soil in which they constantly search for food. No isolates were made from Musca domestica, or from four genera of roaches caught in the wild. However, Toxoplasma was isolated from four of 16 lots of earthworms. Most strains of Toxoplasma isolated from Costa Rican cats produced chronic latent infections in mice. However, even when infected with virulent strains, mice died at a time when numerous bradyzoites had been formed. Also, the availability of bradyzoites in chickens 8-10 days after ingestion of oocysts was comparable to that in mice. Therefore, several infected prey species are available as intermediate hosts to cats, providing the bradyzoites essential for the shedding of large numbers of oocysts. The isolation of Toxoplasma from earthworms or the soil associated with them illustrates their possible role as transport hosts to infect chickens and other birds feeding on them. The possible role of other transport hosts could not be confirmed.
从哥斯达黎加的202只小家鼠中分离出弓形虫的比例为3.5%，从120只褐家鼠中分离出的比例为12.5%，从106只麻雀（海角带鹀）中分离出的比例为16%，从50只鸡中分离出的比例为54%。体重小于500克的鸡的感染率为23%，体重在500至1000克之间的鸡的感染率为73%，这表明鸡感染的速度很快，可能是因为它们不断在土里觅食。未从家蝇或野外捕获的四个蟑螂属中分离出弓形虫。然而，从16批蚯蚓中有4批分离出了弓形虫。从哥斯达黎加猫身上分离出的大多数弓形虫菌株在小鼠体内产生慢性潜伏感染。然而，即使感染了强毒株，小鼠在形成大量缓殖子的时候死亡。此外，鸡在摄入卵囊后8至10天体内缓殖子的情况与小鼠相当。因此，有几种受感染的猎物物种可作为猫的中间宿主，为排出大量卵囊提供必需的缓殖子。从蚯蚓或与其相关的土壤中分离出弓形虫，说明它们可能作为传播宿主感染以它们为食的鸡和其他鸟类。其他传播宿主的可能作用无法得到证实。
