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The plague agent Yersinia pestis persists for years in the soil. Two millennia after swiping over Europe and North Africa, plague established permanent foci in North Africa but not in neighboring Europe. Mapping human plague foci reported in North Africa for 70 years indicated a significant location at <3 kilometers from the Mediterranean seashore or the edge of salted lakes named chotts. In Algeria, culturing 352 environmental specimens naturally containing 0.5 to 70 g/L NaCl yielded one Y. pestis Orientalis biotype isolate in a 40 g/L NaCl chott soil specimen. Core genome SNP analysis placed this isolate within the Y. pestis branch 1, Orientalis biovar. Culturing Y. pestis in broth steadily enriched in NaCl indicated survival up to 150 g/L NaCl as L-form variants exhibiting a distinctive matrix assisted laser desorption-ionization time-of-flight mass spectrometry peptide profile. Further transcriptomic analyses found the upregulation of several outer-membrane proteins including TolC efflux pump and OmpF porin implied in osmotic pressure regulation. Salt tolerance of Y. pestis L-form may play a role in the maintenance of natural plague foci in North Africa and beyond, as these geographical correlations could be extended to 31 plague foci in the northern hemisphere (from 15°N to 50°N).

This study aimed to compare the epidemiology of Rickettsia felis infection and malaria in France, North Africa, and sub-Saharan Africa and to identify a common vector. Blood specimens from 3,122 febrile patients and from 500 nonfebrile persons were analyzed for R. felis and Plasmodium spp. We observed a significant linear trend (p<0.0001) of increasing risk for R. felis infection. The risks were lowest in France, Tunisia, and Algeria (1%), and highest in rural Senegal (15%). Co-infections with R. felis and Plasmodium spp. and occurrences of R. felis relapses or reinfections were identified. This study demonstrates a correlation between malaria and R. felis infection regarding geographic distribution, seasonality, asymptomatic infections, and a potential vector. R. felis infection should be suspected in these geographical areas where malaria is endemic. Doxycycline chemoprophylaxis against malaria in travelers to sub-Saharan Africa also protects against rickettsioses; thus, empirical treatment strategies for febrile illness for travelers and residents in sub-Saharan Africa may require reevaluation.

The purpose of this article is to overview vector-borne rickettsioses in North Africa, focusing on epidemiologic aspects, clinical features, diagnosis procedures, and treatment. The protective measures, the exposure to risk, and the dynamics of endemic emerging and re-emerging diseases in the region are detailed to minimize the risk when traveling in this area. In addition, the article describes the scientific contribution on the rickettsial field of North-African researchers from the beginning of the 20th century until today., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Mediterranean spotted fever is the most important tick-borne disease occurring in Southern Europe and North Africa. The first case of this life-threatening zoonosis was reported in 1910. In the 1930s, the role of the brown dog tick, Rhipicephalus sanguineus, and the causative agent, Rickettsia conorii were described. However, basic questions regarding the relationships between the rickettsia and its tick vector are still unresolved, and the life cycle of R. conorii is incompletely known. There is a lack of knowledge associated with the role of Rh. sanguineus in the maintenance and transmission of R. conorii. The infectious rate of Rh. sanguineus ticks with R. conorii has been found low every time it has been tested; usually lower that 1%. The deleterious impact of R. conorii on ticks has been suggested in experimental models as a potential reason to explain a low prevalence in nature. The long-recognized phenomenon known as reactivation has been suggested as a cause of negative effects--that is, the change in temperature and physiology of the tick host induces the agent to emerge from dormancy and attain infectivity with bad effects on ticks. However, naturally infected colonies of ticks have been maintained in laboratory conditions over several generations. We discuss here several aspects that have been recently studied to better understand Rh. sanguineus-R. conorii relationships, including comparison between the fitness of infected and non-infected ticks in laboratory conditions and the role of external factors such as temperature and starvation.