Ticks are parasites of serious concern for humans, domesticated animals and wild animals. Despite scientific advances, in South America the principal control method for ticks is the use of chemical acaricides. Indiscriminate use of these products causes environmental pollution, food contamination and development of tick resistance to acaricides. In vitro studies and field trials have demonstrated that pathogenic fungal isolates not only cause mortality of many tick species, but also reduce subsequent generations due to effects on their reproductive efficacy. Accordingly, this review presents results of several studies which were conducted in South America. Furthermore, it outlines current information on fungal pathogens of ticks and discusses the need to develop and implement effective strategies for use of entomopathogenic fungi to control ticks in the near future.

Entomopathogenic fungi against South American tick species

Laboratory and field evaluation of Metarhizium anisopliae (Deuteromycotina: Hyphomycetes) for the control of Rhipicephalus microplus (Acari: Ixodidae) in the Mexican tropics.

Updating the application of Metarhizium anisopliae to control cattle tick Rhipicephalus microplus (Acari: Ixodidae).

This work aimed to assess the effect of the fungus Metarhizium anisopliae on off-host Rhipicephalus (Boophilus) microplus from tick-infested Brachiaria decumbens pasture undergoing cattle grazing. For this purpose a naturally tick-infested Brachiaria decumbens pasture of 60 m × 100 m with twelve grazing Holstein Friesian–Nelore (Bos indicus) cross breed bovines was sprayed 12 times, 21 days apart with an aqueous conidial suspension of the E9 isolate of M. anisopliae fungus. Control pasture was treated with conidial suspension vehicle only. Efficacy of treatment was evaluated by tick larvae counts on the pasture and that of engorged female ticks on grazing cattle. Fungus persistence on grass stems as well as soil pasture was assessed after each spray. Efficacy of fungus against ticks was also measured by an in vitro immersion test. Whereas in vitro test showed a clear pathogenic effect of the fungus on ticks, no pathogenic effect over R. (B.) microplus ticks was detected in the field trial by spraying pasture with fungal suspension. Fungus from the suspension could be recovered from both the grass stem as well as the soil of sprayed pasture, even though the numbers obtained varied distinctly and could only be recovered shortly after spray. Pasture environments with exposure to sun and rain, seem to be very detrimental to the fungus, thus suspensions which provide fungus with protection or more resistant isolates to these should be looked for. In order to achieve high fungal efficacy against tick under field conditions, accurate laboratory assays, optimization of application strategy and knowledge of interactions between fungal strains and environmental factors are warranted.

Effect of Metarhizium anisopliae fungus on off-host Rhipicephalus (Boophilus) microplus from tick-infested pasture under cattle grazing in Brazil

Nomuraea rileyi, a fungus pathogenic to insects, has been widely used for biological control of agricultural pests in Brazil. This study investigates the effects of N. rileyi, isolates Nr 138, Nr 151, and Nr 177, to eggs, larvae, and engorged females of Rhipicephalus microplus tick. Specimens were immersed in 1 ml of conidial suspension for 3 min, whereas the control group was immersed in 0.01 % Tween 80 water solution. The isolate Nr 138 controlled 67.37 % of ticks when the highest conidial concentration was used, 108 conidia ml−1. The isolate Nr 177 significantly reduced the percentage of hatch of larvae from eggs treated with 108 conidia ml−1. Conversely, the isolate Nr 151 was not virulent to eggs, larvae, or adults. Variability in virulence was observed among the N. rileyi isolates investigated in the current study—Nr 138 was more virulent to engorged females, while Nr 177 was more virulent to unfed larvae. Although N. rileyi proved to be virulent to several stages of R. microplus, the results obtained in this study indicate that N. rileyi does not appear to be a remarkable biological control agent for R. microplus.

Nomuraea rileyi as biological control agents of Rhipicephalus microplus tick

MELO, D.R. DE; REIS, R.C.S. ; BITTENCOURT, V.R.E.P. [In vitro patogenicity of the fungi Metarhiziumanisopliae (Metschnikoff, 1879) Sorokin, 1883, on the tick...

PATOGENICIDADE IN VITRO DO FUNGO Metarhizium anisopliae (METSCHNIKOFF, 1879) SOROKIN, 1883, SOBRE O CARRAPATO Boophilus microplus (CANESTRINI,1887)

The flea Ctenocephalides felis felis is a parasite that causes allergic dermatitis and also may transmit etiologic agents to domestic animals and humans. This study investigated by scanning electron microscopy the development of entomopathogenic fungi on flea cuticle. Fleas were exposed to conidia (10(8) ml(-1)) of Metarhizium anisopliae (isolate 959) or Beauveria bassiana (isolate 986). Following standard protocols for electron microscopy, the specimens were prepared 2, 15, 26 and 96 h after infection. The micrography revealed that 2 h after fungus exposure, conidia attachments encompassed the entire flea cuticle, especially on abdominal intersegmental membranes. The emergence of germ tubes and appressoria formation occurred at 15 h, thickening and branching of hyphae on the flea cuticle was noted at 26 h. Therefore, both of these fungal isolates were able to develop on cuticular surfaces of C. f. felis.

http://www.scielo.br/pdf/rbpv/v16n3/a11v16n3.pdf

[Development of the fungi Metarhizium anisopliae (Metschnikoff, 1879) Sorokin, 1883 and Beauveria bassiana (Balsamo) Vuillemin, 1912 on the Ctenophephalides felis felis (Bouché, 1835)].

Denise R. De Melo

Papers

PATOGENICIDADE IN VITRO DO FUNGO Metarhizium anisopliae (METSCHNIKOFF, 1879) SOROKIN, 1883, SOBRE O CARRAPATO Boophilus microplus (CANESTRINI,1887)

[Development of the fungi Metarhizium anisopliae (Metschnikoff, 1879) Sorokin, 1883 and Beauveria bassiana (Balsamo) Vuillemin, 1912 on the Ctenophephalides felis felis (Bouché, 1835)].

Characteristics and 1-year survival of incident patients on chronic peritoneal dialysis compared with hemodialysis:a large 11-year cohort study