Mini reviewVectors of rickettsiae in Africa
Introduction
Members of the genus Rickettsia are divided into 2 main groups: the spotted fever group (SFG) and the typhus group (TG). SFG rickettsiae are mainly associated with ticks, but also with fleas (Rickettsia felis) and mites (Ri. akari). Within ticks, transmission can be transovarial and transstadial. SFG rickettsiae have an optimal growth temperature of 32 °C and a G/C content between 32 and 33%. They can polymerize actin and thus can move into the nuclei of host cells (Heinzen et al., 1993, Teysseire et al., 1992, Teysseire et al., 1995). SFG rickettsiae can cause spotted fevers in humans. In contrast, TG rickettsiae are associated with human body lice (Ri. prowazekii) or fleas (Ri. typhi). TG rickettsiae have an optimal growth temperature of 35 °C and a G/C content of 29%. They cannot polymerize actin and thus cannot enter the nuclei of host cells and are thereby only found in the cytoplasms of host cells (Heinzen et al., 1993, Teysseire et al., 1995). TG rickettsiae cause epidemic (Ri. prowazekii) and murine (Ri. typhi) typhus in humans.
The distribution of vector-borne rickettsioses is summarized in Table 1. In this review, we have analyzed 15 species of the Rickettsia genus that have been detected or isolated in arthropods in Africa.
Section snippets
Flea-borne rickettsioses
Siphonaptera (fleas) is a highly specialized holometabolous insect order, currently comprising 246 genera and approximately 2575 described taxa (including subspecies – modified from Lewis, 1999). Fleas are laterally compressed, wingless insects that range from 1 to 10 mm in length. Their head is usually small and shield-shaped (Dunnet and Mardon, 1999). Fleas are obligate endo- or ectoparasites of birds and mammals. Fleas occurring on birds are only represented by 5 families: Ceratophyllidae (68
Murine typhus and Rickettsia typhi
Murine typhus is a worldwide zoonosis and is also known as flea-borne, rat, urban and endemic typhus. The etiological agent, Ri. typhi, is transferred from a rodent reservoir by an arthropod (often X. cheopis) to humans (Houhamdi and Raoult, 2007). Many recent reports state that this is a re-emerging disease that spreads via travelers returning from endemic regions.
Occasionally, other flea species or arthropod vectors have been reported to transmit Ri. typhi including the cat flea C. felis, the
Tick-borne rickettsioses
Ticks are currently considered to be second only to mosquitoes as vectors of human infectious diseases worldwide. All of the nearly 900 known species of ticks require blood for their development and reproduction, and they parasitize animals in almost every region of the world. Two families of ticks are of medical significance: Ixodidae (hard ticks) and Argasidae (soft ticks). To date, most ticks infected with SFG rickettsiae belong to the Ixodidae family. Ixodid ticks feed once within each
Mite-borne rickettsioses
Mites are one of the most common groups of animals, with 45,000 recognized species. The house mouse mite (Liponyssoides sanguineus) is the vector for rickettsialpox due to infection with Ri. akari. The relatively mild disease, characterized by fever and exanthema, was first described in the neighborhood of Kew Garden in the Bronx, New York, during the 1940s (Huebner et al., 1946). This disease has been reported from the Republic of Central Africa (Le Gac and Giroud, 1951). Although this
Louse-borne diseases
The body louse, Pediculus humanus corporis, is a strictly hematophagous ectoparasite that lives in clothing throughout its life cycle. It is specific for human beings in natural conditions. Body lice are distributed in worldwide (Bechah et al., 2008).
The role of the body louse P. humanus corporis in the transmission of epidemic typhus was demonstrated by Charles Nicolle in 1909 (Gross, 1996). Nicolle observed that patients with epidemic typhus were no longer contagious after being admitted to
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Molecular detection of tick-borne pathogens in Rhipicephalus sanguineus sensu stricto collected from dogs in the steppe and high plateau regions of Algeria
2022, Acta TropicaCitation Excerpt :sanguineus s.l. infesting dogs and other domestic or wild animals such as cats, cattle, small ruminants, hedgehogs (Atelerix algirus), boars (Sus scrofa algira), mongooses (Echinomon herpestis), and jackals (Canis aureus) (Bitam et al., 2006; Socolovschi et al., 2009; Khaldi et al., 2012; Bessas et al., 2016; Leulmi et al., 2016; Sadeddine et al., 2020). Rickettsia conorii conorii is the causative agent of Mediterranean spotted fever (human boutonneuse fever), which is endemic in Mediterranean regions, including North Africa (Bitam, 2012; Kernif et al., 2012). Rhipicephalus sanguineus s.l. is considered the principal vector and an important reservoir of R. conorii in both dogs and humans.
Prevalence of Rickettsia africae in tick vectors collected from mammalian hosts in sub-Saharan Africa: A systematic review and meta-analysis
2022, Ticks and Tick-borne DiseasesBacterial arthropod-borne diseases in West Africa
2017, Acta TropicaCitation Excerpt :Recently, R. aeschlimannii has been reported, especially in other Hyalomma ticks, including H. dromedarii ticks, H. m. rufipes and H. impeltatum in North Africa (Demoncheaux et al., 2012; Djerbouh et al., 2012). These findings indicate that the genus Hyalomma may be considered as a main vector of the bacterium (Bitam, 2012). In West Africa, R. aeschlimannii has been associated with six species of ticks.
Rickettsial Infections
2016, Tropical Dermatology: Second EditionFirst detection of Hyalomma rufipes in Germany
2016, Ticks and Tick-borne DiseasesCitation Excerpt :Currently, the former H. marginatum rufipes is considered a species called H. rufipes (Apanaskevich and Horak, 2008), and we follow this view, but future studies with additional lines of evidence could be helpful to validate or reject the current status of these taxa. Ticks belonging to the H. marginatum complex including H. rufipes are known to transmit viral and bacterial agents with the potential to cause diseases with variable severity in humans, among them CCHF virus, R. conorii and R. aeschlimannii (Bitam, 2012; Parola et al., 2013). R. aeschlimannii was detected in ticks collected from birds in Pakendorf and Zerbst, Saxony-Anhalt, Germany, in May 2007.