The predatory capability of three nematophagous fungi in the control of Haemonchus contortus infective larvae in ovine faeces.

The effect of oral administration of three different nematode-trapping fungi, in aqueous suspension containing either Dactylaria sp. or Arthrobotrys oligospora conidia or Duddingtonia flagrans chlamydospores, on the number of Haemonchus contortus infective larvae in sheep faeces, was evaluated. The three selected species of fungi produce three-dimensional adhesive nets in the presence of nematodes. Sixteen Creole sheep were divided into four groups of four animals each. Groups 1 and 2 were orally drenched with a suspension containing 2x10(7) conidia of either A. oligospora or Dactylaria sp. Group 3, received a similar treatment, with D. flagrans chlamydospores, instead of conidia, being administered, at the same dose. Group 4 acted as control, without any fungi. Faecal samples were collected directly from the rectum of each sheep and faecal cultures were prepared and incubated at 15 and 21 days. Larvae were recovered from faecal cultures and counted. The highest reduction of the nematode population occurred in the D. flagrans group, reaching reductions of 96.3% and 91.4% in individual samplings in plates incubated for 15 and 21 days, respectively. Arthrobotrys oligospora showed moderate reductions in the faecal larval population, ranging between 25-64% at 15 days incubation. In general, Dactylaria sp., was less efficient in its trapping ability. Despite the inconsistent results with Dactylaria sp., reduction percentages of 73.4% and 80.7% were recorded in individual samplings during the first and second days, in plates incubated for 15 days. Duddingtonia flagrans, was shown to be a potential biological control agent of H. contortus infective larvae.

[In vitro predatory activity of 8 fungal isolates against the nematode Panagrellus redivivus]. / Acción depredadora in vitro de ocho aislados de hongos contra el nematodo Panagrellus redivivus.

The aim of this study was to evaluate the predacious capacity in vitro of eight isolates of nematophagous fungi: four of Arthrobotrys sp., one of Arthrobotrys oligospora, one of Duddingtonia flagrans, one of Dactylaria sp. and one Monacrosporium eudermatum. Nine groups of Petri dishes with 13 repetitions each were set up. The fungi were seeded in fluor-corn-agar media, following this each Petri dish was added with 150 larvae of the free living nematode Panagrellus redivivus. Five days after larval addition these were collected by Baermannization and were quantified. A significant difference (p < 0.05) between all treated group was observed respect with the control. Isolates FTHO-8 D. flagrans, R6 M. eudermatum, DAC Dactylaria sp. as well as FTHO-4 and FTHO-6 Arthrobotrys sp., showed an excellent predatory activity (> 90%) and they could be considered as potential bio-control agents in future field trials.

[In vitro nematophagous capacity of Duddingtonia flagrans maintained under 2 conditions of preservation]. / Capacidad nematófaga in vitro de Duddingtonia flagrans Mantenido en dos Condiciones de Preservación.

One trial was carried out to evaluate the nematophagous capacity of two Duddingtonia flagrans cultures, one maintained during one year at laboratory temperature and the other one was a recent culture, twelve Petri dishes with flour-corn-agar media were seeded with the 1YC another 12 Petri dishes were inoculated with the RC. Both were added with 150 larvae/dish of the free living nematode Panagrellus redivivus and 12 fluor-corn-agar dishes only with the free living nematode were used as a control. The results showed that the nematophagous capacity of both cultures were similar but it was statistically different (p < 0.05) with respect to the control group. It was concluded that the nematophagous capacity of D. flagrans was not affected in spite of being kept one year at laboratory temperature.

Biological control of Haemonchus contortus infective larvae in ovine faeces by administering an oral suspension of Duddingtonia flagrans chlamydospores to sheep.

A single oral dose of an aqueous suspension containing 11,350,000 chlamydospores of a Mexican isolate of Duddingtonia flagrans (FTHO-8) given to sheep, resulted in a maximum reduction of 88% (range 86.7-90.4%) of the population of Haemonchus contortus infective larvae in the faeces. The effect of this treatment continued for 4-5 days after administration of the suspension. The possible use of this treatment as a method of control of ovine haemonchosis is discussed.

Cryopreservation of infective larvae of Haemonchus contortus.

Three freeze protectants were evaluated to preserve H. contortus infective larvae. Freezing solutions used: A) saline solution phosphate buffer pH 7.2 (PBS); B) 10% DMSO (dimethyl sulphoxide); C) 10% glycerol. Fifty thousand infective larvae were put into each of 10 vials per freeze protectant and then stored into liquid nitrogen. Results were based on the motility of the larvae under a light microscope at 30, 90, 180, and 360 days of freezing. Ten vials of each freeze protectant were removed from the liquid nitrogen at these times and immediately were put on water at 37 C during a minute. Motility percentages obtained were as follows: PBS: 36%, 20%, 7% and 39%; DMSO,: 87%, 69%, 46% and 85%; glycerol: 67%, 62%, 29% and 55%; at 30, 90, 180 and 360 days respectively. Inoculation of infectiva larvae from DMSO and glycerol to calves was successful after 28 days. DMSO was a better freeze preserver for H. contortus.

Reduction of Haemonchus contortus infective larvae by three nematophagous fungi in sheep faecal cultures.

The reduction of Haemonchus contortus (L3) infective larvae in sheep faecal cultures caused by the action of three nematophagous fungi conidia was evaluated in vitro. Addition of 20,000 conidia of Monacrosporium eudermatum, Arthrobotrys oligospora and Arthrobotrys robusta per gram of faeces caused a reduction of 95.7%, 98.3% and 10.1%, respectively, compared with the control group. A 97.4% reduction was observed when combined conidia of the three fungi were used. Total reduction of the larval population was observed by addition of the three fungi at 100,000 conidia per gram of faeces.

Development and recovery of Haemonchus contortus first larval stages on experimental plots in Mexico.

The objective of this study was to determine the influence of relative humidity, environmental temperature and precipitation on the development of Haemonchus contortus from egg to infective larvae on experimental plots in a subtropical subhumid climate of Mexico. The study was of 1 year duration, with the highest rates of recovery of first-stage (L1) and second-stage larvae (L2) obtained at the end of the rainy season, and of third-stage larvae (L3) in the post-rainy season during the autumn. The lowest rate of recovery of L1 was in winter, whereas that of L2 and L3 mainly occurred in the dry season. The shortest development period for L1 was 12 h, for L2 18 h, and for L3 36 h. The longest development period for L1 was 66 h, for L2 156 h and L3 216 h. Statistical analysis of the data obtained showed significant differences in the time of development from eggs to infective larvae with respect to the season of the year.