Brucella melitensis and B. abortus in eggs, larvae and engorged females of Dermacentor marginatus.

Brucellosis is a relatively common zoonosis, particularly in the developing countries. Our aim was to cultivate the Brucella wild-type strain from eggs of Dermacentor marginatus, and to molecularly investigate the presence of Brucella DNA in different developmental stages. A total of 350 engorged adult female ticks were collected from sheep and cattle, and individually placed into a single clean breathable tube suitable for laying eggs and for the development of larvae. Detection of Brucella DNA was attempted in engorged female ticks and their offsprings based on the Brucella outer membrane protein gene 22 (omp22) and IS711 gene. Additionally, bacterial isolation in the culture medium of Brucella was performed. The eggs from the Brucella DNA-positive engorged female ticks were positive for Brucella omp22 (4.6%, 16/350). The prevalence was 40.9% (90/220) in larvae, which developed from the Brucella DNA-positive egg batch. Based on BLASTn analysis of IS711 gene, ten (4.1%, 10/242) PCR products were identified as Brucella melitensis in D. marginatus from sheep, while six (5.6%, 6/108) were identified as B. abortus in D. marginatus infesting cattle. B. melitensis biotype 3 was isolated from eggs of D. marginatus. This is the first study which demonstrates the transovarial transmission of Brucella in the D. marginatus. Furthermore, Brucella may be partially transmitted from D. marginatus eggs to larvae (40.9%) in D. marginatus. These findings extend our knowledge on the transmission of Brucella in D. marginatus offsprings.

Ovicidal Efficacy of Metarhizium anisopliae (Hypocreales: Clavicipitaceae) towards Rhipicephalus sanguineus (Acari: Ixodidae) Eggs

@#Rhipicephalus sanguineus, commonly known as brown dog tick is a widespread species with considerable public health and economic importance. Tremendous efforts were performed to control the tick populations with the concern of resistance build-up and environmental issues. Alternative towards microbial control thus emerged as one option to reduce tick populations. In this study, the ovicidal efficacy of a native isolate entomopathogenic hyphomycetes fungi, Metarhizium anisopliae strain HSAH5 was evaluated against eggs of R. sanguineus. Spray applications with three different conidial concentrations of 105, 106 and 107 conidia mL-1; 40 ppm of Flumethrin and a negative control. The M. anisopliae strain was found highly virulent to R. sanguineus eggs by reducing the hatching percentages to ≈30% compared with 8.9% in Flumethrin eggs. The result showed a significantly higher mortality in M. anisopliae group than those of the control groups (F = 42.08, df = 32, P < 0.001) at 30 days post-infection. However, there are no significant differences within the M. anisopliae group, in which the mortality between different conidial concentrations is almost the same. The estimated LC50 of M. anisopliae against eggs of R. sanguineus is 1.36 × 103 conidia ml-1. Thus, these results suggest M. anisopliae strain HSAH5 could be a potential biocontrol agent of R. sanguineus in the integrated approach to managing ticks in the residential landscape by targeting on the eggs.