Suarez V H, Busetii M R, Miranda A O, Prévot F, Jacquiet P
INTA, Estación Experimental Agropecuaria Anguil, CC 11, 6326 Anguil, La Pampa, Argentina.
Parasite. 2004 Dec;11(4):405-10. doi: 10.1051/parasite/2004114405.
Seasonal population trends and effects of Oestrus ovis in naturally infected sheep were studied over 13 months, in the Western of the Pampeana region. At weaning, 140 growing lambs were randomly allocated to two groups: UG, untreated group and TG treated every 4 weeks with closantel (10 mg/kg). Successive Oestrus free tracer lambs (TL) by previous treatment (n = 65) were slaughtered after 20-30 exposition days for larval counts. Likewise, other group PL of 117 permanent untreated lambs was slaughtered from four to 17 months of age. Weighing and assessment of health signs of UG and TG and blood samples were monthly carried out. The prevalence of infection in permanent group varied from 33% to 100%. Mean number of larvae in PL was 6.1 with 3 L1, 1.4 L2 and 1.6 L3 during spring-summer and 17.9 with 16.9 L1, 0.5 L2 and 0.4 L3 during autumn-winter months. In PL the proportions of larvae in each of the different larval stages was similar during spring and summer, but a significant (P < 0.01) increase of L1 was detected during autumn and winter. The prevalence in tracer lambs was 100% during summer time and larvae were absent from 25-May to 25-October. Mean larval burdens of positive TL varied from 6.4 to one Oestrus and a significant peak (P < 0.05) of larvae was seen from December to March. Since March to November only L1 was recovered from TL. TG group showed a reduction in nasal discharge and in antibody ELISA levels, but no difference was observed in live weight gain between TG and UG. These results show a high prevalence during summer and that the perpetuation of Oestrus is ensured by an autumn period of arrested development and the over wintering larvae in the sheep heads.
在潘佩阿纳地区西部，对自然感染绵羊的季节性种群趋势以及羊狂蝇（Oestrus ovis）的影响进行了为期13个月的研究。断奶时，140只生长中的羔羊被随机分为两组：UG组，即未处理组；TG组，每4周用氯氰碘柳胺（10毫克/千克）处理一次。先前经过处理的连续无发情期的示踪羔羊（TL，n = 65）在暴露20 - 30天后屠宰，用于幼虫计数。同样，117只永久未处理羔羊组成的PL组在4至17月龄时屠宰。每月对UG组和TG组进行称重、健康体征评估并采集血样。永久组的感染率在33%至100%之间变化。PL组幼虫的平均数量在春夏季节为6.1只，其中L1期3只（译者注：此处原文可能有误，L1期3只加上L2期1.4只加上L3期1.6只不等于6.1只，可能是表述问题，但按原文翻译），L2期1.4只，L3期1.6只；在秋冬季节为17.9只，其中L1期16.9只，L2期0.5只，L3期0.4只。在PL组中，每个不同幼虫阶段的幼虫比例在春夏季节相似，但在秋冬季节检测到L1期幼虫显著增加（P < 0.01）。示踪羔羊在夏季的感染率为100%，在5月25日至10月25日期间没有幼虫。阳性TL的平均幼虫负荷从6.4只到1只羊狂蝇不等，在12月至3月期间观察到幼虫数量有显著峰值（P < 0.05）。从3月到11月，从TL中仅回收L1期幼虫。TG组的鼻分泌物和抗体ELISA水平有所降低，但TG组和UG组在体重增加方面没有差异。这些结果表明夏季感染率很高，并且羊狂蝇通过秋季发育停滞期和在羊头部越冬的幼虫得以持续存在。
