Henipaviruses at the Interface Between Bats, Livestock and Human Population in Africa

Nipah virus (NiV) and Hendra virus (HeV) are closely related members within the genus Henipavirus, family Paramyxoviridae, for which fruit bats serve as the reservoir. The initial emergence of NiV infections in pigs and humans in Malaysia, and HeV infections in horses and humans in Australia, posed severe impacts on human and animal health, and continues threatening lives of humans and livestock within Southeast Asia and Australia. Recently, henipavirus-specific antibodies have also been detected in fruit bats in a number of sub-Saharan African countries and in Brazil, thereby considerably increasing the known geographic distribution of henipaviruses. Africa is progressively being recognized as a new high prevalence zone for henipaviruses, as deduced from serological and molecular evidence of past infections in Madagascar, Ghana, Republic of Congo, Gulf of Guinea, Zambia, Tanzania, Cameroon, and Nigeria lately. Serological data suggest henipavirus spillover from bats to livestock and human populations in Africa without reported clinical disease in any of these species. All virus isolation attempts have been abortive, highlighting the need for further investigations. The genome of the Ghanaian bat henipavirus designated Ghana virus (GhV), which was detected in a pteropid Eidolon helvum bat, is the only African henipavirus that has been completely sequenced limiting our current knowledge on the genetic diversity and pathogenesis of African henipaviruses. In this review, we summarize the available data on the circulation of henipaviruses in Africa, discuss potential sources for virus spillover, and highlight existing research gaps.

Mangifera indica Bark Essential Oil: Chemical Composition and Biological Activities in Comparison with Aqueous and Ethanol Extracts

Ethnobotanic surveys have revealed the use of Mangifera indica L. (Anacardiaceae) bark for the treatment of infectious diarrhea. The essential oil of M. indica bark is described for the first time for its chemical composition, radical scavenging activity (DPPH method) and antimicrobial properties. The total phenols content of its water and ethanol bark extracts as well as their radical scavenging and antimicrobial properties were also evaluated. Four commercial plant extracts were also studied for a comparison purpose. The antimicrobial activities were measured for all samples against three Gram (-): Escherichia coli, Salmonella enteritidis, Shigella and two Gram (+): Staphylococcus aureus and Bacillus cereus bacteria. The M. indica bark essential oil was characterized by the association of two major sesquiterpenes: ( E)-β-caryophyllene (60.3%) and α-humulene (36.7%). It presented the lowest ratio of concentration to inhibition zone diameter on all the strains. The aqueous and ethanol extracts of M. indica bark were characterized by high contents of total phenols compounds and high radical scavenging activity compared to the essential oil. Finally, the interesting combination of the antibacterial and antiradical activities of the aqueous M. indica bark extract justifies the traditional use of this plant part in decoction form for the treatment of diarrheal infections.

Antimicrobial structure activity relationship of five anthraquinones of emodine type isolated from Vismia laurentii

BACKGROUND

Antimicrobial activity of anthraquinone compounds of emodine type has been reported by many authors. These compounds are found in Vismia laurentii (Clusiaceae), a plant used in traditional pharmacopoeia for treatment of microbial infections among others affections. The continuous identification of new compounds has raised the problem of the relation between the structure and antimicrobial properties.

RESULTS

The yeast growth kinetics parameters were not influenced by the pH variation as it was the case for the other tested bacteria. Fungicidal activities were noted for all molecules while only few of them had bactericidal activities, mostly on Gram positive bacteria. Mathematical model establishing a quantitative relationship between physicochemical properties of molecules and their fungicidal activities were obtained for Candida albicans and showed that physicochemical properties impacting on antifungal activity were polarizability, partition coefficient, molecular weight and hydrogen bond acceptor.

CONCLUSIONS

This work demonstrated that the presence of a long aliphatic chain methoxy group substituted in position two of the emodine structure increased the antibacterial properties of the studied compounds. Moreover this antimicrobial property depends on the pH of the environment, and specifically on the polarizability and number of hydrogen bond acceptors of the compound.