Ovicidal potential of Pochonia chlamydosporia isolate Pc-10 (Ascomycota: Sordariomycetes) on egg masses of the snail Pseudosuccinea columella (Mollusca: Gastropoda).

Snails of the species Pseudosuccinea columella are considered intermediate hosts of Fasciola hepatica, a digenetic trematode that infects bile ducts of ruminants and humans, causing economic damage and serious problems for public health. These gastropods inhabit ponds, have high reproductive capacity, and lay their egg masses in submerged substrates on pond edges where they are exposed to desiccation and microbes, including fungi, that may exert pathogenic effects on the snail and its embryos. This information is relevant for control of the intermediate host and therefore of fasciolosis. With the objective of evaluating ovicidal potential of Pochonia chlamydosporia (Pc-10 isolate), a nematophagous fungus used as antagonistic agent for a wide variety of helminths of medical and veterinary importance, on egg masses of P. columella, we compared a treated group, where the egg masses were exposed to Pc-10 for a period of 25 days, and a control group, in which there was no exposure to the fungus. The results indicated that the embryogenesis process was significantly inhibited (93.15%) by Pc-10, suggesting its applicability in biological control programs of lymnaeid snails. In addition, ultrastructure showed the occurrence of different types of interactions between the egg masses with the mycelia of Pc-10: type 1, biochemical effects by the adherence of hyphae; type 2, morphological alterations, but without hyphal penetration; and type 3, lytic effect, morphological damage caused by penetration of hyphae by the fungus, resulting in some important structural modifications, thus compromising the viability of the eggs. The results demonstrate the susceptibility of P. columella egg masses to an isolate of P. chlamydosporia under laboratory conditions, providing valuable information for the biological control of this intermediate host.

[The relationship between larvae recovered of pasture and counting eggs per grams of feces (epg) of the gastrointestinal nematodes of cattle in the Microrregion of Viçosa, State of Minas Gerais]. / Relação entre larvas recuperadas da pastagem e contagem de ovos por gramas de fezes (opg) de nematóides gastrintestinais de bovinos na Microrregião de Viçosa, Minas Gerais.

Eight calves with one year old approximately, Holstein-zebu cross-breeding, were stocked in paddock to analysis the relation between the eggs per grams of feces (EPG) and larvae number recovered of pastures, from February to September 2005, at municipality of Viçosa, Zona da Mata region, State of Minas Gerais, Brazil. During this time, feces and pastures were collected for examination of EPG and larvae recovered from pastures, respectively. The genera Cooperia, Haemonchus and Oesophagostomum larvae were harvested in paddock until 20 centimeters and between 20 and 40 cm far distance of fecal cake. The genus Cooperia (60.97%) was the most prevalent in the pastures. In coprocultures, Haemonchus (42.65%) was the most prevalent genus of nematode. The coefficient of correlation of the larvae recovered of pasture and the EPG was not significant (P < 0.05). It can indicate that this relation can be influenced possibly by several factors related on the nematodes, the host and the climate conditions.

[Evaluation of nematode predacious fungus Duddingtonia flagrans on infective Haemonchus contortus and Strongyloides papillosus larvae of goats]. / Avaliação do fungo predador de nematóides Duddingtonia flagrans sobre larvas infectantes de Haemonchus contortus e Strongyloides papillosus de caprinos.

One brazilian isolate of nematode-trapping fungus Duddingtonia flagrans AC 001 was evaluated regarding the capacity of supporting passage through the gastrointestinal tract of goats without losing the ability to entrap infective Haemonchus contortus and Strongyloides papillosus larvae (L3). Ten saneen goats of eight months old, males and infected naturally were divided in two groups of five animals. In the group 1, the animals received orally 20 g of pellets of the D. flagrans. In the group 2 (control), the animals received orally 20 g of pellets without fungi. Fecal Samples were collected at 14, 20, 24, 36 and 46 hours after the treatments and were allocated in fecal cultures at 25 degrees C during fifteen days. There was significant reduction (p<0.05) of the average number of S. papillosus larvae recovered of the fecal cultures in the animals treated with fungus when compared with the control animals at 14 and 46 hours, in the end of the experiment, this difference was 82.3%. There was significant reduction (p<0.05) of the average number of H. contortus larvae recovered of the fecal cultures in the animals treated with fungus when compared with the control animals at 14, 20 and 46 hours, in the end of the experiment, this difference was 59.3%. Such evidences confirm the transit of these fungi pellets by the digestive tract of the goats without loss of the predatory viability on L3 of H. contortus and S. papillosus.

[In vitro predatory activity of fungi Arthrobotrys robusta, Duddingtonia flagrans and Monacrosporium thaumasium on infective larvae of Ancylostoma spp. of dogs]. / Atividade predatória in vitro dos fungos Arthrobotrys robusta, Duddingtonia flagrans e Monacrosporium thaumasium sobre larvas infectantes de Ancylostoma spp. de cães.

The predatory capacity of isolates of nematode-trapping fungus Arthrobotrys robust (I31), Duddingtonia flagrans (CG768) and Monacrosporium thaumasium (NF34A) on infective larvae of Ancylostoma spp. was evaluated in laboratorial conditions in experimental assay in medium water-agar 2% (WA 2%). There was significant reduction (p <0.05) of 89.89%, 97.75% and 88.76% in the average of infective larvae of Ancylostoma spp. recovered of medium WA 2% from the treatments with isolated CG768, I31 and NF34A, respectively. The isolated I31 was the most effective in the capture of the infective larvae. The results show that these fungi can be used in the environmental control of the free-living stages of Ancylostoma spp. of dogs.

[Viability of nematophagous fungi Arthrobotrys robusta, Duddingtonia flagrans and Monacrosporium thaumasium after sporulation in different culture media]. / Viabilidade sobre larvas infectantes de Ancylostoma spp. dos fungos nematófagos Arthrobotrys robusta, Duddingtonia flagrans E Monacrosporium thaumasium após esporulação em diferentes meios de cultura.

Due to the shortage of studies that indicate the culture mediums that optimize the sporulation of namatophagous fungi for use in researche, the sporulation of the fungal isolates A. robusta (I31), D. flagrans (CG768) and M. thaumasium (NF34A) was evaluated in laboratorial conditions for 10 days in the means water-agar 2% (WA 2%), potato-dextrose-agar 2% (PDA 2%), corn-meal-agar 2% (CMA 2%) and yeast-phosphate-sulphate-sucrose-agar (YPSSA). The largest conidia production (P < 0.05) for the isolate CG768 happened in BDA 2% while in the isolates I31 and NF34A produced larger conidia number in YPSSA (P < 0.05). The viability of the conidia to prey infective Ancylostoma spp. larvae did not lose its effectiveness (P < 0.05) independent of the culture medium. The middle of culture did not influence in the viability of the conidia (P > 0.05).