Evaluation of vaccine candidates purified from the adult ticks of Ornithodoros savignyi (Acari: Argasidae) and Hyalomma dromedarii (Acari: Ixodidae) against tick infestations.

Ticks cause anemia, toxicosis, growth delay, and transmit infectious diseases in animals and humans. The current study aimed to evaluate the immunoprophylactic properties of two vaccine candidates to develop vaccine against tick infestations. These two vaccine candidates were specific fraction from the adults of the soft tick Ornithodoros savignyi and cross-reactive fraction from the adults of the hard tick Hyalomma dromedarii. Both specific and cross-reactive fractions were isolated by Cyanogen Bromide-activated Sepharose-4B affinity column chromatography. Both candidates proved their cross-reactivity by enzyme linked immunosorbent assay and Western blot. Characterization of the two vaccines by SDS-PAGE showed that the O. savignyi specific fraction consists of four bands; 97, 85, 66 and 11.5 kDa compared with nine bands associated with its crude antigen (196-11.5 kDa). The H. dromedarii cross-reactive vaccine candidate consists of three bands; 97, 66 and 45 kDa compared to eight bands of its crude antigen (196-21 kDa). Two common bands of 97 and 66 kDa between two candidates showed immunogenic cross-reactivity with the developed antisera of both infestations by Western blot. Immunization of rabbits intramuscularly with two doses of the fractions separately (40 µg/kg) led to immunological and parasitological changes. Immunologically; the level of immunoglobulins in vaccinated rabbits increased significantly compared with control infested non-vaccinated rabbits. These immunoglobulins are probably responsible for the protective effect of both candidates. Parasitologically, immunized rabbits showed protection against infestation by adult ticks as proved by significant feeding rejection percentage and significant reduction in egg and engorgement weights of H. dromedarii. While insignificant protection was observed against O. savignyi ticks infestation in feeding rejection and reduction in engorgement weight. In conclusion, this study suggests promising immunoprophylactic potentials of the purified fractions against tick infestations in rabbits through induction of IgG responses. The protective effect of both vaccine candidates deserves further evaluation in other hosts and against other tick infestations.

Efficacy and safety of ethanolic Curcuma longa extract as a treatment for sand tampan ticks in a rabbit model.

BACKGROUND AND AIM: The soft tick Ornithodoros savignyi is distributed throughout Africa, including Egypt. It primarily attacks camels, cattle, donkeys, and cows; and rarely affects humans. This study evaluated the acaricidal efficacy of ethanolic Curcuma longa extract (Turmeric) on the second nymphs of O. savignyi and then investigated the safety of this herb in rabbits. MATERIALS AND METHODS: The nymphs were immersed in 10, 5, 2.5, 1.25, and 0.625 mg/ml ethanolic C. longa extract. An additional group was immersed in ethanol as a control. On the 1st, 7th, and 15th-day post-treatment, the mortality percentages, LC50, and LC95 were calculated. The ticks exposed to 10mg/ml ethanol C. longa extract were investigated by scanning electron microscopy (SEM). Three male New Zealand White rabbits were orally administered 2ml (two doses) of 10mg/ml ethanolic C. longa extract, and another three rabbits were orally given two doses of 2ml of absolute ethanol as a negative control. Histopathological examination of the kidney and liver hematology and the kidney and liver function was performed. Chemical analysis of the extract was determined by gas chromatography-mass spectrometry (GC-MS). RESULTS: The LC50 and LC95 were 1.31 and 15.07, 1.07 and 8.56, and 0.81 and 6.97mg/ml on the 1st, 7th, and 15thday, respectively. SEM revealed that mamillae and spots on the surfaces of the treated ticks were not discriminating except for some clefts on the surfaces. The histological examination, blood profile, and biochemical analyses revealed no significant differences between the treated and untreated rabbits (p>0.05). GC/MS analysis revealed 50 compounds, and curcumene and tumerone were found to be the major constituents of this ethanolic extract. CONCLUSION: The ethanolic C. longa extract produced a strong acaricidal effect on the second nymph of O. savignyi, and it was safe to use in rabbits.

Morphological and molecular description of immature stages of Ornithodoros savignyi (Acari: Argasidae).

This study was designed to provide more details about larva, first nymph, and second nymph of Ornithodoros savignyi using a combination of light microscopy (LM), scanning electron microscopy (SEM), and partial sequence of mitochondrial 16S ribosomal ribonucleic acid (rRNA). The main characteristics of larva are wrinkled integument with many grooves, gnathosoma without camerostome cheeks, hypostome with a pair of large teeth apically, and tarsus without humps. The comparisons between the first and the second nymphs are different shape and distribution of dorsal grooves; a few spots without mammilla on the dorsal surface of the second nymph; 27 and 63-65 pairs of setae on the dorsal surface of the first and second nymphs, respectively; small holes on mammillae that are more dense in the second nymph; basis capitulum with two pairs of small setae in the second nymph; and one pair of sate in the first nymph, hypostome with dental formula 2/2 in the first nymph, and 3/3 in the second nymph. The partial 16S rRNA sequence of the second nymph that was determined as O. savignyi (450 bp) was deposited in GenBank under the accession number KU163242.