Rhabditis spp., in the Espírito Santo, State of Brazil and evaluation of biological control

Abstract The objectives of this study were to describe occurrences of Rhabditis spp. causing parasitic otitis in dairy cattle of Gir breed in the state of Espírito Santo, southeastern Brazil, and to evaluate the biological control of this nematode using the nematophagous fungi Duddingtonia flagrans (AC001) and Monacrosporium thaumasium (NF34). After nematode detection and collection, three groups were formed: two groups that were treated, respectively, with the fungal isolates; and a control group, without fungus. The treatments were as follows: (a) Petri dishes containing the culture medium 2% water agar (WA) + 250 nematodes + AC001; (b) Petri dishes containing 2% WA + 250 nematodes + NF34; and (c) Petri dishes containing only 2% WA + 250 nematodes. After seven days at 27 °C the treatments with fungi were able to capture and destroy the nematodes, with percentages of 82.0% (AC001) and 39.0% (NF34) in relation to the control group. The results demonstrate the occurrence of Rhabditis spp. after animals physical examination and that there was efficacy of the in vitro predatory activity of both fungal isolates. Thus, these results are important because they can assist in future in vivo control of this nematode in cattle.

摘要 本研究旨在描述巴西东南部圣埃斯皮里图州吉尔奶牛群体中杆线虫属（Rhabditis spp.）引发寄生虫性中耳炎的发生情况，并评估食线虫真菌杜丁顿霉（Duddingtonia flagrans，AC001）与单顶孢霉（Monacrosporium thaumasium，NF34）对该线虫的生物防治效果。完成线虫的检测与采集后，实验分为三组：两组分别使用上述真菌菌株进行处理，另一组为不添加真菌的空白对照组。具体处理方案如下：(a) 培养皿中添加2%水琼脂（WA）培养基+250条线虫+AC001菌株；(b) 培养皿中添加2%水琼脂（WA）培养基+250条线虫+NF34菌株；(c) 培养皿中仅添加2%水琼脂（WA）培养基+250条线虫。在27℃条件下培养7天后，施加真菌处理的两组均成功捕获并灭杀线虫，相较于空白对照组，AC001菌株的线虫灭杀率达82.0%，NF34菌株达39.0%。研究结果证实，通过对受试奶牛进行体格检查可检出杆线虫属感染，且两种真菌菌株均展现出优异的体外捕食灭杀线虫活性。本研究结果具有重要应用价值，可为后续开展奶牛体内该线虫的生物防治工作提供参考依据。