Kinetics of capture and infection of infective larvae of trichostrongylides and free-living nematodes Panagrellus sp. by Duddingtonia flagrans.

Duddingtonia flagrans, a nematode-trapping fungus, has been investigated as an agent for biological control against infective larvae of gastrointestinal nematode parasites of production animals. The initial process of nematode-trapping fungi infection is based on an interaction between the trap structure of the fungus and the surface of the nematode cuticle. This report investigates by light and scanning electron microscopy the kinetics of capture and infection during the interaction of D. flagrans with the infective larvae (L(3)) of trichostrongylides and the free-living nematode Panagrellus sp. D. flagrans was cultivated for 7 days in a Petri dish containing agar-water. L(3) and Panagrellus sp. were inoculated in the Petri dishes and the samples consisting of agar-L(3)-fungi and agar-Panagrellus sp.-fungi were collected after 10, 20, 30, 40, 50, 60, and 70 min and 3, 4, 5, 10, 15, 20, and 25 h of interaction. All samples were observed by light microscopy. The samples with 1, 5, 15, and 25 h of interaction were also analyzed by scanning electron microscopy. The interaction was monitored up to 25 h. An initial differentiation of predation structures was observed after 30 min of interaction. The presence of traps and of captured L(3) or Panagrellus sp. occurred after 70 min. The live captured nematodes were observed up to 3 h of interaction. However, after 4 h, all Panagrellus sp. were dead. It took 15 h of interaction for the fungus to invade the L(3), and the presence of hyphae inside the nematode near the region of penetration was evident. At this time, the hyphae had filled the whole body of Panagrellus sp. The complete occupation of the body of L(3) occurred at 20 h of interaction and with 25 h the nematode was completely damaged except for the cuticle. Although the double cuticle of L(3) slows the penetration of D. flagrans, it was possible to verify that the process of trap formation and capture occurs quickly when both nematodes were tested, suggesting that the organisms would eventually be killed once in contact with the fungi encouraging the use of the fungus as a biological control agent.

Anthelmintic efficacy and management practices in sheep farms from the state of Rio de Janeiro, Brazil.

Anthelmintic resistance in parasites maybe a consequence of over-exposing populations of parasites to drugs or from the commerce/transit of animals harboring resistant parasites. Knowledge of the sensitivity of nematodes to anthelmintics is essential to establish an efficient integrated program of parasite control. In Brazil, producers rely on technology transfer from field professionals and non-technical labor for new management strategies of parasite control. The aim of this work was to determine the practices farmers used for anthelmintic management and to monitor drug efficacy on sheep farms from northern and northwestern regions of the state of Rio de Janeiro, Brazil. A questionnaire was sent to 34 farms, and anthelmintics were tested on ten of these farms. Sheep (n=10/group) were weighed and treated with albendazole, closantel, doramectin, fenbendazole, ivermectin, levamisole, moxidectin, or nitroxynil with their recommended doses. Faeces were collected on the day of treatment and after 7-10 days. The faecal egg count reduction test was evaluated based on RESO 2.0. Among the farmers interviewed, 97% applied commercial anthelmintics to control parasites, 77% rotated anthelmintics annually, 72% used ivermectin as the principal anthelmintic, and 38% applied anthelmintics with a frequency of 30-60 days. On two farms, none of the anthelmintics was efficacious. Levamisole had the best overall efficacy (70%). Albendazole, ivermectin, and fenbendazole were efficacious (above 95%) on only two farms. The present work illustrates the alarming lack of efficacy of drugs even in an area new to sheep farming. It is important to establish alternative strategies of management in a broad program of parasite control for reducing the selection pressure on parasites by the commercially available anthelmintics.