ABSTRACT
Adulticidal and oviposition- and hatching-altering activities of essential oil extracted from Mexican oregano leaves (Lippia graveolens H.B.K.) (OEO) were evaluated on engorged adult female Rhipicephalus microplus ticks using the adult immersion test bioassay. Twofold dilutions of OEO were tested from a starting dilution of 10% down to 1.25%. Results showed 100% adulticidal activity at 10% OEO concentration and oviposition inhibition of 65.8% and 40.9% at 5.0% and 2.5% OEO concentration, respectively. Egg hatching inhibition was achieved by 26.0% and 11.5% at 5.0% and 2.5% OEO concentration, respectively. These effects could be attributed to OEO major components: thymol, carvacrol and p-cymene, which together account for more than 60.0% of the OEO chemical composition. Mexican oregano could represent a potential source for development of alternative tick control agents.
ABSTRACT
Adulticidal and oviposition- and hatching-altering activities of essential oil extracted from Mexican oregano leaves (Lippia graveolens H.B.K.) (OEO) were evaluated on engorged adult female Rhipicephalus microplus ticks using the adult immersion test bioassay. Twofold dilutions of OEO were tested from a starting dilution of 10% down to 1.25%. Results showed 100% adulticidal activity at 10% OEO concentration and oviposition inhibition of 65.8% and 40.9% at 5.0% and 2.5% OEO concentration, respectively. Egg hatching inhibition was achieved by 26.0% and 11.5% at 5.0% and 2.5% OEO concentration, respectively. These effects could be attributed to OEO major components: thymol, carvacrol and p-cymene, which together account for more than 60.0% of the OEO chemical composition. Mexican oregano could represent a potential source for development of alternative tick control agents.
ABSTRACT
Upon oxygen shift-down, Mycobacterium tuberculosis complex bacteria can induce a genetic program characterized by halted duplication, which is called Non-replicating persistence (NRP). During this phase, at least 48 genes, collectively named Dormancy survival regulator (DosR) regulon, are important for the long-term survival of bacilli under a non-respiring state, a condition that bacilli encounter inside granulomatous lesions. It remains unclear whether expression of NRP genes occurs within the tissue of Mycobacterium bovis naturally infected cattle. In order to start dissecting this question, total RNA from bovine lymph node tissues of sacrificed tuberculin reacting animals was isolated and transcription of genes required for in vivo duplication (esxB and fbpB) and in vitro NRP (hspX, pfkB, and mb2660c) were analyzed by RT-PCR approaches. Detection of transcripts was positive in bovine tissue samples for genes hspX, pfkB, and mb2660c in 84, 32, and 21%, respectively. NRP genes were upregulated even in animals with a negative IFN-γ in vitro test, and the expression of NRP genes occurred more often than expression of the esxB gene.
Subject(s)
Bacterial Proteins/metabolism , Gene Expression Regulation, Bacterial , Lymph Nodes/microbiology , Mycobacterium bovis/growth & development , Up-Regulation , Animals , Bacterial Proteins/genetics , Cattle , Interferon-gamma/biosynthesis , Interferon-gamma Release Tests , Mycobacterium bovis/genetics , Mycobacterium bovis/metabolism , Mycobacterium bovis/pathogenicity , Regulon , Skin Tests , Tuberculin Test , Tuberculosis, Bovine/microbiologyABSTRACT
Acaricidal effects of three essential oils extracted from Mexican oregano leaves (Lippia graveolens Kunth), rosemary leaves (Rosmarinus officinalis L.), and garlic bulbs (Allium sativum L.) on 10-d-old Rhipicephalus (Boophilus) microplus (Canestrini) tick larvae were evaluated by using the larval packet test bioassay. Serial dilutions of the three essential oils were tested from a starting concentration of 20 to 1.25%. Results showed that both Mexican oregano and garlic essential oils had very similar activity, producing high mortality (90-100%) in all tested concentrations on 10-d-old R. microplus tick larvae. Rosemary essential oil produced >85% larval mortality at the higher concentrations (10 and 20%), but the effect decreased noticeably to 40% at an oil concentration of 5%, and mortality was absent at 2.5 and 1.25% of the essential oil concentration. Chemical composition of the essential oils was elucidated by gas chromatography-mass spectrometry analyses. Mexican oregano essential oil included thymol (24.59%), carvacrol (24.54%), p-cymene (13.6%), and y-terpinene (7.43%) as its main compounds, whereas rosemary essential oil was rich in a-pinene (31.07%), verbenone (15.26%), and 1,8-cineol (14.2%), and garlic essential oil was rich in diallyl trisulfide (33.57%), diallyl disulfide (30.93%), and methyl allyl trisulfide (11.28%). These results suggest that Mexican oregano and garlic essential oils merit further investigation as components of alternative approaches for R. microplus tick control.
