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United States Department of Agriculture

Agricultural Research Service


Location: Emerging Pests and Pathogens Research

Title: Occurrence of pathogenic fungi to Amblyomma cajennense in a rural area of central Brazil and their activities against vectors of Rocky Mountain spotted fever

item D'alessandro,, Wb
item Humber, Richard
item Luz,, C.

Submitted to: Veterinary Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/23/2012
Publication Date: 3/1/2012
Citation: D'Alessandro,, W., Humber, R.A., Luz,, C. 2012. Occurrence of pathogenic fungi to Amblyomma cajennense in a rural area of central Brazil and their activities against vectors of Rocky Mountain spotted fever. Veterinary Parasitology. 188:156-159. DOI: 10.1016/j.vetpar.2012.02.016.

Interpretive Summary: This study presents the results of field studies to monitor the populations of an important tick vector of Rocky Mountain spotted fever and the incidence of fungal pathogens affecting these ticks in a set of pasture habitats in central Brazil. This type of information has not been gathered previously from the star tick (which completes only a single generation per year); these ticks are particularly significant pests of livestock and, in this part of Brazil, are also borne in high numbers throughout the year by the resident populations of capybaras (the world’s largest rodent species). The fungi obtained from the field-collected ticks have also been known from ticks in other parts of the world but these cultures are important because they have been shown in laboratory conditions to cause significant mortality to all life stages of these ticks including their eggs, a stage that is usually thought to resist fungal infections. These studies present initial results that are to be extended in laboratory and further field studies to find better, more environmentally benign means of controlling tick populations and their transmission of diseases other than the continued dependence on chemical pesticides.

Technical Abstract: Two isolates of Beauveria bassiana and one of Purpureocillium lilacinum (=Paecilomyces lilacinus) were found affecting A. cajennense engorged females collected on horses (0.15 percent infection rate from a total of 1982 specimens) and another two isolates of P. lilacinum and one M. anisopliae detected in soils (2.1 percent from 144 samples) collected in typical pasture habitats of this tick in Central Brazil from October 2009 to March 2011. Fungi were isolated from soils with Rhipicephalus sanguineus as surrogate baits. No fungi were found in ticks or soils during the driest months (May to August). While testing pathogenicity of fungi, all R. sanguineus females were killed regardless of the isolate and A. cajennense was less susceptible to infection with P. lilacinum within 20 days and fungi sporulated abundantly on the cadavers. All three fungal species probably act as natural antagonists of A. cajennense particularly in the rainy season and have interest for integrate control of vectors of Rocky Mountain spotted fever.

Last Modified: 10/16/2017
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