Van Wyk J A, Gerber H M, Van Aardt W P
Onderstepoort J Vet Res. 1977 Sep;44(3):173-94.
Exsheathed infective larvae (L 3) of 19 species of nematodes were tested for infectivity in either sheep or cattle after they had been frozen in 0,9% NaCl solution, stored for a relatively short time in the gas phase of liquid nitrogen and subsequently thawed. In addition, 13 of these species were tested after similar storage for up to 18 months. In sheep, Haemonchus contortus, Ostertagia circumcincta, Trichostrongylus axei, Trichostrongylus colubriformis, Nematodirus spathiger and Oesophagostomum columbianum were viable after 2 years of cryopreservation, a mean of greater than 90% of the L 3 being alive when thawed after this period. Similar results were obtained with Chabertia ovina L 3 after 18 months and with Marshallagia marshalli, Trichostrongylus falculatus and Dictyocaulus filaria, after a short period of freezing. On the other hand, Gaigeria pachyscelis and Strongyloides papillosus survived freezing for up to 7 months but neither was viable at the end of this period, nor was exsheathed G. pachyscelis viable without freezing. Most of these infestations were established by inoculating the infective larvae into the abomasum and/or duodenum. M. marshalli, T. falculatus and C. ovina also proved infective after oral dosing. D. filaria, the only other species tested by this route, was not infective when dosed per os after thawing. The infective larvae of the bovine nematodes, Haemonchus placei, Ostertagia ostertagi, Nematodirus helvetianus, Oesophagostomum radiatum, Cooperia pectinata and Cooperia punctata survived freezing for a mean of 26 months, greater than 90% being alive on thawing, but infectivity was generally lower than with the same genera in sheep. Even when not frozen, exsheathed Bunostomum phlebotomum was non-infective. When Cooperia spp. after thawing were tested for infectivity by the oral route, more worms developed in one calf infested orally than in another infested by inoculation into the duodenum. Ova of H. contortus, M. marshalli, O. circumcincta, T. colubriformis, T. falculatus, N. spathiger, C. ovina, H. placei, O. ostertagi, Cooperia spp. and N. helvetianus were recovered from the faeces of animals infested with cryopreserved L 3. No ova of O. columbianum or O. radiatum were recovered from faeces, because differential larval counts were performed before they were patent. Nevertheless, gravid females were obtained post-mortem. Frozen L 3 of N. helvetianus were used to re-establish a pure strain in calves, 2,3 million ova being recovered from infestations with 10 670 L 3 frozen for 26 months. The infectivity of the progeny of frozen L 3 was tested with M. marshalli and C. ovina. In both instances infectivity was high and the worms which developed also produced ova, thus completing the cycle. This appears to be the first report of infective larvae of parasitic nematodes retaining their infectivity after being frozen in liquid nitrogen (gas phase) for longer than 2 years. This is also apparently the first time that M. marshalli T. colubriformis, T. falculatus, T. axei, N. spathiger, C...
19种线虫的脱鞘感染性幼虫（L3）在0.9%氯化钠溶液中冷冻、在液氮气相中储存较短时间并随后解冻后，对绵羊或牛进行感染性测试。此外，其中13种线虫在类似储存长达18个月后进行了测试。在绵羊中，捻转血矛线虫、环形奥斯特线虫、斧形毛圆线虫、蛇形毛圆线虫、粗纹食道口线虫和哥伦比亚食道口线虫在冷冻保存2年后仍具有活力，在此期间解冻后，平均超过90%的L3存活。短时间冷冻后，18个月的绵羊夏伯特线虫L3以及马氏马歇尔线虫、镰状毛圆线虫和丝状网尾线虫也获得了类似结果。另一方面，厚尾盖吉线虫和乳头类圆线虫在冷冻长达7个月后存活，但在此期间结束时均无活力，未冷冻的脱鞘厚尾盖吉线虫也无活力。这些感染大多通过将感染性幼虫接种到皱胃和/或十二指肠来建立。马氏马歇尔线虫、镰状毛圆线虫和夏伯特线虫经口服给药后也被证明具有感染性。丝状网尾线虫是通过该途径测试的唯一其他物种，解冻后经口给药时不具有感染性。牛线虫的感染性幼虫，如牛血矛线虫、奥氏奥斯特线虫、瑞士细颈线虫、辐射食道口线虫、栉状古柏线虫和点状古柏线虫在冷冻后平均存活26个月，解冻时超过90%存活，但感染性通常低于绵羊中同一属的线虫。即使未冷冻，脱鞘的牛钩口线虫也无感染性。解冻后的古柏属线虫经口服途径测试感染性时，一头经口感染的小牛体内发育的蠕虫比另一头经十二指肠接种感染的小牛体内发育的蠕虫更多。从感染冷冻保存的L3的动物粪便中回收了捻转血矛线虫、马氏马歇尔线虫、环形奥斯特线虫、蛇形毛圆线虫、镰状毛圆线虫、粗纹食道口线虫、夏伯特线虫、牛血矛线虫奥氏奥斯特线虫、古柏属线虫和瑞士细颈线虫的虫卵。未从粪便中回收哥伦比亚食道口线虫或辐射食道口线虫的虫卵，因为在它们产卵前进行了幼虫鉴别计数。然而，死后获得了妊娠雌虫。瑞士细颈线虫的冷冻L3用于在小牛中重新建立一个纯系，从用10670条冷冻26个月的L3感染的动物中回收了230万个虫卵。用马氏马歇尔线虫和夏伯特线虫测试了冷冻L3后代的感染性。在这两种情况下，感染性都很高，发育的蠕虫也产生了虫卵，从而完成了循环。这似乎是关于寄生线虫的感染性幼虫在液氮（气相）中冷冻超过2年后仍保持其感染性的首次报告。这显然也是首次对马氏马歇尔线虫、蛇形毛圆线虫、镰状毛圆线虫、斧形毛圆线虫、粗纹食道口线虫、哥伦比亚食道口线虫、辐射食道口线虫、栉状古柏线虫、点状古柏线虫、牛血矛线虫、奥氏奥斯特线虫、瑞士细颈线虫、牛钩口线虫、夏伯特线虫、厚尾盖吉线虫、乳头类圆线虫、丝状网尾线虫和捻转血矛线虫进行这样的研究。
