Pathogenicity and thermotolerance of entomopathogenic fungi for the control of the scab mite, Psoroptes ovis

Abstract

Psoroptes ovis is responsible for a highly contagious skin condition, both in sheep and cattle. This parasite has a marked economical impact in the sheep and cattle industry. Biological control is considered as a realistic alternative to chemotherapeutic control. Laboratory experiments were carried out to evaluate the pathogenicity and the thermotolerance of twelve isolates of entomopathogenic fungi from four genera (Beauveria Vuillemin, Metarhizium Sorokin, Paecilomyces Bainier and Verticillium Nees). The pathogenicity was evaluated by the survival of P. ovis females after exposure to 10(6) to 10(8) conidia ml(-1) in humidity chambers. Results revealed intra- and interspecies differences. All isolates with the exception of B. bassiana IHEM3558 and V. lecanii MUCL8672 induced 50% mortality within 2 days at the highest concentration. At this concentration the entire mite population became infected with all isolates but B. bassiana IHEM3558; however, only four isolates gave rise to 100% infected cadavers at the lowest concentration. The thermotolerance of each isolate was evaluated by measuring its growth on an artificial medium kept between 25 and 37.5 degrees C. All isolates were able to grow up to 30 degrees C but only two, M. anisopliae IHEM18027 and Paecilomyces farinosus MUCL18885, tolerated temperatures up to 35 degrees C. These two isolates could be considered as good candidates for further use as biopesticide taking into account their virulence and thermotolerance. Other critical factors linked with the implementation of this type of biocontrol in P. ovis infected animals are discussed.

First report of the infection of insecticide-resistant malaria vector mosquitoes with an entomopathogenic fungus under field conditions

“…Supporting evidence for this comes from results that indicate that 33°C is too hot for the sporulation, growth and viability of B. bassiana [31]. Further evidence can be found in a series of laboratory studies that reported relatively rapid losses in fungal viability after exposure to heat and humidity [11,22,32,33] and from B. bassiana gene-knockout studies that linked thermotolerance to viability [34,35]. In concurrence with these findings, Scholte et al [18] found that the viability of M. anisopliae- treated cotton sheets decreased from 96% in suspension to 63% three weeks after application in Tanzania, whereas the viability of the conidia remaining in suspension did not change [18], as was found in the present study.…”

“…When oil-formulated fungal conidia were applied to polyester netting and kept at 27°C, the viabilities of M. anisopliae and B. bassiana were significantly reduced both one day and again one week after application, although this may also have been due to the polyester netting substrate [11]. Lekimme et al [22] inoculated temperate and tropical strains of B. bassiana and M. anisopliae onto agar plates and held them at a range of temperatures to investigate thermotolerance. They found that at 35°C only one M. anisopliae strain and none of their B. bassiana strains grew [22].…”

“…Lekimme et al [22] inoculated temperate and tropical strains of B. bassiana and M. anisopliae onto agar plates and held them at a range of temperatures to investigate thermotolerance. They found that at 35°C only one M. anisopliae strain and none of their B. bassiana strains grew [22]. Whilst field work has shown that entomopathogenic fungi can infect and kill malaria vectors [18,19], and reduce blood feeding behaviour in Culex mosquitoes [20], Scholte et al [18] found that fungal viability reduced from 96% to 63% after three weeks exposure to Tanzanian field conditions.…”

Entomopathogenic Fungi and Bacteria in a Veterinary Perspective

“…The rate of parasite killing and thermotolerance are of capital importance to allow the molds to carry out their entomopathogenic activity. These features depend on the selected fungal isolate [274]; B. bassiana was reported to show the optimal growth temperature between 25 • C and 28 • C [275], even if some isolates can grow at about 30 • C, with highly reduced activity and may not survive at 34 • C [276].…”

Psoroptes sp. Infestation in Sulawesi Bear Cuscus (Ailurops ursinus) in Indonesia

“…Report cases of disease caused Psoroptes sp. the possum has not been published, one of a kind Psoroptes is Psoroptes cuniculi generally attacks on domesticated livestock such as rabbits (Acar et al, 2007;Kyung-Yeon & Oh-Deog, 2010), Psoroptes is the causative agent of dermatitis in cattle, sheep, goats, rabbits and turkey (Kurtdede et al, 2007;Lekimme et al, 2008). Type P. cuniculi attack on wildlife group Artiodactyls reported by Pederson et al (2007), whereas the incidence of deer in the United States reported by Schmith et al (1982).…”