Graczyk T K, Cranfield M R, Fayer R, Trout J, Goodale H J
Department of Molecular Microbiology and Immunology, Johns Hopkins University, Baltimore, MD, USA.
Trop Med Int Health. 1997 Apr;2(4):341-7. doi: 10.1111/j.1365-3156.1997.tb00149.x.
Five Cryptosporidium-free Canada geese (Branta canadensis) were individually orally dosed with 3.5 x 10(6) Cryptosporidium parvum oocysts infectious to neonatal BALB/c mice. After intestinal passage, inoculum-derived oocysts extracted from goose faeces established severe infection in 14 neonatal BALB/c mice (inoculum dose 2.5 x 10(5)/mouse). The inoculum-derived oocysts were detected in goose faeces up to 9 days post-inoculation (PI); the number of intact oocysts and oocyst shells shed during the first 3 days PI was significantly higher than for the remaining 6 days PI (P < 0.01). Based on acid-fast stained air-dried direct wet smears, 62% of the oocysts in goose faeces were intact (oocyst shells) constituted 38%) and conformed to morphological features of viable and infectious inoculum oocysts. The fluorescence scores of the inoculated oocysts, obtained by use of the MERIFLUOR test, were identical to those obtained for the faeces-recovered oocysts (majority 3+ to 4+). The dynamics of oocyst shedding showed that overall, the birds released a significantly higher number of intact oocysts than oocyst (P < 0.01). Retention of the viability and infectivity of C. parvum oocysts following intestinal passage through a migratory water-fowl species has serious epidemiological implications. Water-fowl can serve as mechanical vectors for the water-borne oocysts and can contaminate surface waters with C. parvum. As the concentration of Cryptosporidium oocysts in source waters is attributable to water-shed management practices, water-shed protection programme officials should consider water-fowl as a potential factor enhancing contamination of the source water with Cryptosporidium.
五只无隐孢子虫的加拿大鹅(Branta canadensis)分别经口接种3.5×10⁶对新生BALB/c小鼠具有感染性的微小隐孢子虫卵囊。经肠道排出后,从鹅粪便中提取的接种源卵囊在14只新生BALB/c小鼠中引发了严重感染(接种剂量为2.5×10⁵个/小鼠)。在接种后长达9天的时间里,在鹅粪便中都能检测到接种源卵囊;接种后第1至3天排出的完整卵囊和卵囊壳数量显著高于接种后其余6天(P<0.01)。基于抗酸染色的风干直接湿涂片,鹅粪便中62%的卵囊是完整的(卵囊壳占38%),符合有活力且具感染性的接种源卵囊的形态特征。通过MERIFLUOR检测获得的接种卵囊的荧光评分与从粪便中回收的卵囊的荧光评分相同(大多数为3+至4+)。卵囊排出动态表明,总体而言,鹅排出的完整卵囊数量显著高于卵囊壳数量(P<0.01)。微小隐孢子虫卵囊经迁徙水禽肠道排出后仍保持活力和感染性,这具有严重的流行病学意义。水禽可作为水源性卵囊的机械传播媒介,并可将微小隐孢子虫污染地表水。由于水源水中隐孢子虫卵囊的浓度归因于流域管理措施,流域保护计划官员应将水禽视为增加水源水被隐孢子虫污染的潜在因素。