title: Development of free-living stages of Strongyloides ratti under different temperature conditions.
abstract: It is well known that the Strongyloides species have two different developmental courses-direct and indirect development-and selection of these courses is affected by various environmental factors. This study examined the effect of temperature on the development of first-stage larvae (L1s) of Strongyloides ratti, to clarify how larvae adapt and survive at unsuitable temperatures. It was revealed that L1s cultured at 4 or 10 °C for 120 h could not develop because of growth arrest or delay. However, L1s could develop after transfer to culture at 25 °C for 48 h. Although larvae cultured at 25 °C take indirect development, larvae subjected to low-temperature stimulation (at 4 or 10 °C) take direct development into infective third-stage larvae (L3s), and only 1 min of low-temperature stimulation was sufficient to induce direct development. Morphological study of low-temperature-stimulated L3s revealed that those stimulated at 4 °C (L3-4) showed less development, but those stimulated at 10 °C (L3-10) developed as well as the control (no low-temperature stimulation). Furthermore, we revealed that L3-10 showed similar infectivity to the control when they were injected subcutaneously into rats as the final host, which indicated that L3-10 grew normally. We conclude that S. ratti has a survival strategy of growth arrest or delay if excreted in cold conditions. Moreover, even if they start development after transfer to suitable conditions, they memorize low-temperature stimulation, which leads them to direct development thereafter so that they can immediately infect the final host.
authors.affiliation: Department of Parasitology, Faculty of Health Sciences, Kobe University Graduate School of Health Sciences, 7-10-2, Tomogaoka, Suma-ku, Kobe, 654-0142, Japan.
authors.forename: Maki
authors.initials: M
authors.lastname: Sakamoto
authors.forename: Shoji
authors.initials: S
authors.lastname: Uga
mesh_terms: D000818:Animals; D003080:Cold Temperature; D005243:Feces / Q000382:microbiology; D005260:Female; D007814:Larva / Q000254:growth & development; D008297:Male; D010270:Parasite Egg Count; D051381:Rats; D017208:Rats, Wistar; D017170:Strongyloides ratti / Q000254:growth & development*; D013696:Temperature
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