In vitro stress selection of nematophagous fungi for biocontrol of parasitic nematodes in ruminants

Abstract

Laboratory experiments were designed to select nematophagous fungi that were able to survive in vitro conditions simulating passage through the gastro-intestinal tract of cattle. All of the tests were conducted at 39°C. In a primary stress selection step in diluted rumen fluid, 21 isolates were obtained. Each of the primary stress selected isolates was tested in synthetic saliva, rumen fluid simulating the activity in the rumen, rumen fluid followed by pepsin-hydrochloric acid treatment simulating the additional effect of ruminal and abomasal activity, pepsin-hydrochloric acid solution simulating conditions in the abomasum and finally in a trypsin solution as an example of enzyme activity in the gut. The effect of the rumen fluid alone, or rumen fluid followed by pepsin-hydrochloric acid treatment, were responsible for the reduction in surviving fungal isolates. Only six of thirteen isolates belonging to the genus Arthrobolrys survived while seven of eight isolates of the genus Duddingtonia survived. Fourteen isolates were tested for their predatory capacity in a dung pat bioassay. Fungi of the genera Arthrobotrys and Duddingtonia reduced the development of Ostertagia ostertagi third stage larvae by approximately 75% and 96% respectively compared to the number of larvae that developed from fungus-free control pats.

Survey of nematophagous fungi in South Africa : research communication

“…The modified sprinkling technique of Larsen, Wolstrup, Henriksen, Dackman, Grønvold & Nansen (1991) was used for the isolation of nematophagous fungi. Soil, faeces, leaf litter and compost samples collected from five provinces in South Africa (Gauteng, Mpumalanga, North West, Limpopo and Free State) were sprinkled in a cross configuration on individual plates of 2 % water agar containing 0.02 % tetracycline hydrochloride to suppress bacterial growth.…”

Occurrence, morphological characteristics and ribotyping of New Zealand isolates ofDuddingtonia flagrans,a candidate for biocontrol of animal parasitic nematodes

“…We have used Duddingtonia to maintain continuity with the biological control literature. Detection of D. flagrans in New Zealand, following its isolation and characterisation in Australia (Larsen et al 1994), continental Europe (Virat 1977;Larsen et al 1991), North America (Mahoney & Strongman 1994), Central America (Mendoza de Gives et al 1998), and Asia (Chandrawathani et al 1999;Sanyal 2000) provides further support for the view that this fungus is distributed worldwide.…”

“…In five, 0.5 g substrate was applied to the plate using the "soil sprinkling method" (Duddington 1955). The remaining five plates received a substrate suspension (Larsen et al 1991), prepared by macerating 10 g substrate in 15 ml sterile water in a small chamber homogeniser (350 ml; Atomix) at high speed for 1 min. After settling for 5 min, 0.5 ml aliquots of the supernatant were pipetted in a star pattern on each plate and allowed to dry.…”

“…The fungus shows particular promise for the biological control of livestock parasites because of its ability to produce large numbers of thick-walled, resilient chlamydospores. These survive unfavourable environments such as those in the animal gut (Larsen et al 1991). This property allows chlamydospores to be administered orally and results in their deposition in dung simultaneously with eggs of internal parasites.…”

Produção e composição do leite de vacas submetidas à dieta contendo diferentes níveis de caroço de algodão

“…Impulsionados pelos danos causados pelos nematóides e pela baixa eficiência dos métodos de controle da verminose existente naquela época, alguns pesquisadores iniciaram estudos objetivando o controle biológico das formas de vida livre dos nematóides com o uso de fungos nematófagos. Têm sido realizados vários estudos, in vitro, sobre a patogenicidade de fungos nematófagos sobre helmintos de animais domésticos (NANSEN et al, 1988;LARSEN et al, 1991;ARAÚJO et al, 1992;ARAÚJO et al, 1993;WALLER e FAEDO,1993;ARAÚJO et al, 1994;WALLER et al, 1994;GRONVOLD et al, 1995;VIEIRA-BRESSAN et al, 1995;ARAÚJO, 1996;PADILHA e GIVES, 1996;CASTRO et al, 1999;MOTA et al, 1999;NEVES et al, 1999;RODRIGUES et al, 1999;GRAMINHA, 2000;GRAMINHA et al, 2000a;GRAMINHA et al, 2000b).…”