Fungal fauna ofIxodes scapularissay andRhipicephalus Sanguineus(Latreille) (Acari: Ixodida) with special reference to species-associated internal mycoflora

Abstract

Body contents of the black-legged tick, Ixodes scapularis, and brown dog (or kennel) tick, Rhipicephalus sanguineus, were screened by fungal culturing for more virulent strains to use in biological control and to investigate the propensity of ticks as endosymbiotic hosts. A low incidence of internal fungi was observed in both ticks, averaging < 20% recovery. Noteworthy in R. sanguineus was identification of Scopulariopsis carbonaria Morton and Smith (previously unknown within ticks) among the few internal isolates as well as the common internal associate S. brevicaulis (Sacc.) Bainier. Ixodes scaputaris ticks were similarly devoid of fungi except for recovery ofMetarhizium anisopliae (Metsch.) that is likely present as a parasite. Compositions of external mycoflora were alike (13 Deuteromycetes and three Zygomycetes) and reflect fungi prevalent in soil, leaf litter and organic debris. Despite this rich external mycoflora, internal fungi appear to be restricted to Scopulariopsis spp. and harboring this fungus is linked to the large wax glands ('sagittiform sensilla') that are characteristic of metastriate, but not prostriate (Ixodes), ticks. However, low levels of fungi within R. sanguineus indicate that the prevalence of tick-borne fungi is not as widespread as previously thought. The fact that not all classified entomopathogenic fungi recovered from tick surfaces were found inside the tick suggests that successful parasitism may be limited to a few select fungi (e.g., Metarhizium spp.) in nature, thus affecting potential biological control applications.

Isolation of Entomopathogenic Fungi From Soils andIxodes scapularis(Acari: Ixodidae) Ticks: Prevalence and Methods

“…Five known entomopathogens were identified from these specimens, and Samšiňáková et al (1974) concluded that the presence of entomopathogenic species on the cuticle of ticks may be sufficient to influence tick population dynamics. The results from this study, combined with those reported by Benoit et al (2005), Yoder et al (2003), and Samšiňáková et al (1974), show that directly plating ticks is an effective method for finding entomopathogenic fungi on tick surfaces.…”

“…The methods used in this study enabled identification of four taxa known to be entomopathogenic in addition to five unidentified species that were suspected entomopathogens from a total of 64 nymphs plated. Similarly, a survey of the external mycoflora of nonfed female I. scapularis resulted in the isolation of one entomopathogenic fungus, but 14 additional fungi were isolated from the 25 ticks plated (Benoit et al 2005). Likewise, Yoder et al (2003) used methods similar to those in this study, plating whole female American dog ticks ( Dermacentor variabilis ), and isolated three genera from the external surfaces of only 12 ticks.…”

“…These internal infection rates are relatively low compared with those reported in previous studies. For example, 6 of 25 (24%) surface-sterilized, nonfed female I. scapularis were found to harbor the entomopathogenic fungus, Metarhizium anisopliae , and 25% of nonfed female Rhicephalus sanguineus contained fungus (Benoit et al 2005). In addition, Yoder et al (2003) surface-sterilized, dissected, and plated female D. variabilis to observe internal fungal growth and found that one fungal species, identified as Scopulariopsis brevicaulis , was present in 100% of their 25 specimens.…”

“…However, there is little information relating the frequency and distribution of fungal species present in blacklegged tick habitat to the virulence of those fungi being developed as biocontrol agents. To our knowledge, only two surveys have attempted to identify fungi associated with field-collected I. scapularis (Zhioua et al 1999, Benoit et al 2005), and only a few have looked at fungi associated with other ticks (Kalsbeek et al 1995, Yoder et al 2003). To help clarify the role that these fungi may have in the life cycle of I. scapularis , optimization of methods to survey and isolate fungi occurring in situ is needed.…”

Evidence for Personal Protective Measures to Reduce Human Contact With Blacklegged Ticks and for Environmentally Based Control Methods to Suppress Host-Seeking Blacklegged Ticks and Reduce Infection with Lyme Disease Spirochetes in Tick Vectors and Rodent Reservoirs

“…Numerous species of entomopathogenic fungi have been isolated from soils and I. scapularis in the Northeast (Ginsberg and LeBrun 1996, Zhioua et al 1999b, Benoit et al 2005, Tuininga et al 2009, Greengarten et al 2011). Several species of fungi—including Beauveria bassiana (Balsamo-Crivelli) Vuillemin, Hypocrea lixii Patouillard, Metarhizium brunneum (Petch) (including some varieties previously assigned to Metarhizium anisopliae (Metschnikoff) Sorokin), and Penicillium soppii Zalessky—were shown to cause mortality in both fed and unfed I. scapularis in laboratory trials (Zhioua et al 1997; Benjamin et al 2002; Kirkland et al 2004; Hornbostel et al 2004, 2005a; Greengarten et al 2011).…”