UNESP - Universidade Estadual Paulista, Departamento de Parasitologia, Instituto de Biociências, Caixa Postal 510, CEP: 18618-000 Botucatu, SP, Brazil.
UNESP - Universidade Estadual Paulista, Departamento de Parasitologia, Instituto de Biociências, Caixa Postal 510, CEP: 18618-000 Botucatu, SP, Brazil.
Vet Parasitol. 2014 Jun 16;203(1-2):127-38. doi: 10.1016/j.vetpar.2014.02.048. Epub 2014 Mar 2.
Two trials were conducted to determine the prepatent and the patent period of Haemonchus contortus and Haemonchus placei in Santa Ines crossbred sheep and to determine whether serial infections with both species confer protection against homologous or heterologous challenge. To evaluate the prepatent and patent periods of infection, five lambs received a single infection with 4000 H. contortus-infective larvae (L3), and another five received a single infection with 4000 H. placei L3. H. contortus presented patency earlier than H. placei. Animals infected with both species shed a large number of eggs in the faeces for several months with the highest counts, with means higher than 3000 eggs per gram of faeces (EPG) between 24 and 106 days and between 38 and 73 days post infection with H. contortus and H. placei, respectively. H. contortus eggs were detected in the faeces for a minimum of 302 days and a maximum of 538 days post infection, while the H. placei patent period lasted from 288 to 364 days. In the second trial, one group of lambs (n=12) was serially infected 12 times (three times per week for four weeks) with 500 L3 of H. placei and then challenged with either H. placei (n=6) or with H. contortus (n=6). The lambs in the second group (n=12) were serially infected 12 times with 500 L3 of H. contortus and then challenged with H. contortus (n=6) or with H. placei (n=6), and a third group of lambs was single challenged with H. placei (n=6), H. contortus (n=6), or remained uninfected throughout the trial period (control group, n=6). Animals serially infected with H. placei and then challenged with the same species presented the most intense immune response with the highest levels of anti-parasitic immunoglobulin and number of inflammatory cells in the abomasal mucosa. As a result, this group had the lowest rate of parasite establishment (2.68% of the 4000 L3 given), but this phenomenon did not occur in animals single challenged with H. placei, in which the rate of establishment was relatively high (25.3%), confirming that the protective immune response to H. placei develops only when animals are repeatedly infected with this species. However, when the animals were previously serially infected with H. placei and then challenged with H. contortus, no evidence of significant protection was observed (establishment of 19.18%). The results of the trials showed an important role played by the immune response on parasite-host specificity.
两项试验旨在确定 Santa Ines 杂交羊感染捻转血矛线虫和奥斯特线虫的潜伏期和专利期，并确定两种物种的连续感染是否对同源或异源挑战提供保护。为了评估感染的潜伏期和专利期，五头羔羊接受了 4000 条捻转血矛线虫感染性幼虫（L3）的单次感染，另有五头羔羊接受了 4000 条奥斯特线虫 L3 的单次感染。捻转血矛线虫的出现早于奥斯特线虫。两种物种感染的动物在粪便中排泄大量虫卵，数月内最高计数超过 3000 个虫卵/克粪便（EPG），分别在感染捻转血矛线虫和奥斯特线虫后 24 至 106 天和 38 至 73 天之间。捻转血矛线虫卵在粪便中至少检测到 302 天，最长检测到 538 天，而奥斯特线虫专利期持续 288 至 364 天。在第二次试验中，一组羔羊（n=12）被连续感染 12 次（每周三次，持续四周），每次感染 500 条奥斯特线虫 L3，然后分别用奥斯特线虫（n=6）或捻转血矛线虫（n=6）进行攻虫。第二组（n=12）羔羊被连续感染 12 次，每次感染 500 条捻转血矛线虫 L3，然后用捻转血矛线虫（n=6）或奥斯特线虫（n=6）进行攻虫，第三组羔羊用奥斯特线虫（n=6）、捻转血矛线虫（n=6）或整个试验期间保持未感染（对照组，n=6）进行单次攻虫。连续感染奥斯特线虫然后用同种线虫攻虫的动物表现出最强的免疫反应，具有最高水平的抗寄生虫免疫球蛋白和胃黏膜中的炎症细胞数量。因此，该组寄生虫定植率最低（给予的 4000 条 L3 的 2.68%），但这种现象在仅用奥斯特线虫攻虫的动物中并未发生，其定植率相对较高（25.3%），证实只有当动物反复感染该物种时，才能对奥斯特线虫产生保护性免疫反应。然而，当动物先前连续感染奥斯特线虫，然后用捻转血矛线虫攻虫时，未观察到显著的保护作用（建立率为 19.18%）。试验结果表明，免疫反应在寄生虫-宿主特异性中发挥了重要作用。
