Association between Duddingtonia flagrans, dimethylsulfoxide and ivermectin for the control of Rhabditis spp. in cattle.

Cattle parasitic otitis caused by the nematode Rhabditis spp. is a serious health problem in Brazil, a situation which is confounded by lack of effective control measures. In vitro studies associating biological and chemical control as an alternative method showed promising results. The objective was to evaluate the combined use of Duddingtonia flagrans (AC001), 10% dimethylsulfoxide (DMSO), and 1.9% ivermectin for the in vivo control of Rhabditis spp., in naturally infected Gyr cattle. For this purpose, 48 animals, whose infection in both ears was diagnosed, were randomly assigned to 6 groups: group 1 (ivermectin 1.9%); group 2 (10% DMSO); group 3 (AC001); group 4 (ivermectin 1.9% + 10% DMSO w/v); group 5 (1.9% ivermectin + AC001 w/v); group 6 (10% DMSO + AC001 v/v). The treatments were performed in a single dose, in the right ears, with the left ears remaining untreated, as a control group. There was a significant reduction (p < 0.01) in the number of nematodes in the treated groups in relation to the control, with the following best efficacies: groups 1 and 2, 47% and 52.9%, respectively, 7 days after treatment; groups 3, 4, and 5, 47.8%, 48.6% and 36.7%, respectively, 14 days post-treatment; group 6, 38.4%, 21 days post-treatment. It was concluded that the combination of chemical compounds and D. flagrans in a single application was effective for the in vivo control of Rhabditis spp. in naturally infected cattle.

Colonization and destruction of ants of the genus Camponotus sp. (Hymenoptera: Formicidae) in vitro by the fungus Pochonia chlamydosporia in the southeast region of Brazil.

The objective of this study was to evaluate, in vitro, the colonization and destruction of ants of the genus Camponotus sp. by the ovicidal fungus Pochonia chlamydosporia (VC4 isolate), in the southeast region of Brazil. The insects used in the experiment were worker ants of the genus Camponotus sp., collected periodically in the environment and immediately transported to the laboratory in test tubes. Then, VC4 growth was promoted in 2% chitin agar medium (2% WQ) to obtain a fungal solution containing conidia and/or chlamydospores. Two experimental groups were formed. Treated group consisted of Petri dishes containing 2% agar-water culture medium (2% WA) with nine live insects and 20 µL of fungal solution at the concentration of 15,000 conidia/chlamydospores. Control group consisted of Petri dishes containing 2% WA culture medium and nine live insects. The dishes in the treated and control groups were incubated in BOD at 25 ± 1 °C and 80 ± 10% relative humidity for 4 days. After 4 days, it was observed that the VC4 had grown, colonized, and caused the destruction of the ants. The fungus P. chlamydosporia was efficient at colonizing and destroying the urban ants collected on an experimental basis. Thus, it could open up new ways to reduce the use of chemical compounds in the future, decreasing health and environmental problems.

Nematocidal activity of extracellular enzymes produced by the nematophagous fungus Duddingtonia flagrans on cyathostomin infective larvae.

Duddingtonia flagrans produces chitinases, however, optimization of the production of these enzymes still needs to be explored, and its nematocidal activity should still be the subject of studies. The objective of the present study was to optimize chitinase production, and evaluate the nematocidal activity of extracellular enzymes produced by the nematophagous fungus D. flagrans on cyathostomin infective larvae. An isolate from D. flagrans (AC001) was used in this study. For the production of enzymes (protease and chitinase), two different culture media were inoculated with AC001 conidia. Both enzymes were purified. The statistical Plackett-Burman factorial design was used to investigate some variables and their effect on the production of chitinases by D. flagrans. After that, the design central composite (CCD) was used in order to determine the optimum levels and investigate the interactions of these variables previously observed. Only two variables (moisture and incubation time), in the evaluated levels, had a significant effect (p<0.05) on chitinase production. The conditions of maximum chitinase activity were calculated, with the following values: incubation time 2 days, and moisture 511%. The protease and chitinase derived from D. flagrans, individually or together (after 24h), led to a significant reduction (p<0.01) in the number of intact cyathostomin L3, when compared to the control, with following reduction percentage values: 19.4% (protease), 15.5% (chitinase), and 20.5% (protease+chitinase). Significant differences were observed (p<0.05) between the group treated with proteases in relation to the group treated with proteases+chitinases. In this study, the assay with the cyathostomins showed that chitinase had a nematocidal effect, suggesting that this enzyme acts on the "fungus versus nematodes" infection process. It is known that nematode eggs are rich in chitin, and in this case, we could think of a greater employability for this chitinase.