First molecular detection of Rickettsia africae in a tropical bont tick, Amblyomma variegatum, collected in Corsica, France.

Cicculli V, et al. Exp Appl Acarol. 2019.


Here we report the first detection of Amblyomma variegatum, a tick species of medical and veterinary importance, and the first molecular evidence of a pathogen, Rickettsia africae, both new to Corsica (France). In August 2018, an ixodid tick with an unusual morphology was removed from the ventral part of a cow’s whole skin in a slaughterhouse located in the village of Ponte-Leccia (Haute-Corse). The tick was morphologically identified as an adult male of A. variegatum. This result was confirmed by 16S rDNA sequence analysis with a close relative being a sequence from Senegal showing 99% nucleotide identity. We tested the tick for Ehrlichia and Rickettsia. The tick was positive to Rickettsia and the corresponding sequence matched with R. africae. There is little or no risk of the introduction and establishment of a viable population of A. variegatum in Corsica by migrating birds. However, if it did, it could produce major economic losses for livestock production. Further studies and sustained surveillance are indicated, not only focusing on this species of tick and this rickettsia, but also on other microorganisms of veterinary and medical importance that might be transmitted in Corsica and other Mediterranean islands.


**Comment**  The tropical bont tick is considered one of the most detrimental of the tick species present in Africa and now the Caribbean (CaribVet 2011b, Stachurksi and Lancelot 2006).

Now it’s been found in France.

Of human health concern, it is implicated as a potential vector for Crimean-Congo hemorrhagic fever virus (CCHF)Yellow Fever virus (CDC 2001, Merck 2011), & African Tick Bite Fever (Rickettsia africae),which results in fevers, headaches and swollen lymph nodes (Parola et al. 1999).

It has had a huge effect on the livestock industry, primarily through its transmission of heartwater disease, Ehrlichia ruminantium (formerly Cowdria ruminantium) (Allan et al. 1998, CaribVet 2011b, OIE 2009, Parola et al. 1999) and their association with dermatophilosis, Dermatophilus congolensis (Allan et al. 1998, Barré and Garris 1990, CaribVet 2011b, Merck 2011).

It’s also been implicated as a vector or potential vector for several diseases to include Dugbe virus, and Jos virus (Merck 2011). In the Caribbean, only heartwater disease and dermatophilosis have been detected in the hosts and have demonstrated clinical symptoms.

The dispersal of tropical bont tick is associated with the migration patterns of the cattle egret, Bubulcus ibis (OIE 2009, Barré et al. 1995, Pegram and Eddy 2002). The birds transport the larvae and the nymphs of the tick (Deem 1998). Because the non-feeding stages of the life cycle occur within the environment and not on the host, the transport of infested vegetation and litter is a potential source for dispersion as well (Alderink and McCauley 1988, Barré et al. 1995).

The adult ticks are found on various domesticated species such as camels, cattle, goats, sheep and even dogs (Deem 1998, Merck 2011). The ticks also are found on various species of wildlife throughout the distribution range, but the adults are generally found on the larger mammals (Barré et al.1995, Yonow 1995).

Biological controls (birds, parasitic wasps, nematodes, bacteria, and fungi) have not been very successful in eradicating the tick.

tropical_bont_tick02Adult male tropical bont tick, Amblyomma variegatum Fabricius. Photograph by Alan Walker, University of Edinburgh.

tropical_bont_tick03Adult female tropical bont tick, Amblyomma variegatum Fabricius. Photograph by Richard Matthews and Alan Walker, University of Edinburgh.

Other ticks in other places have been found to carry CCHF (it can also be spread human to human):