Abstract
BackgroundThe presence in Morocco of Argasid ticks of the Ornithodoros erraticus complex, the vector of tick-borne relapsing fever (TBRF) in North Africa, has been known since 1919, but the disease is rarely diagnosed and few epidemiological data are available.Methodology/Principal FindingsBetween 2006 and 2011, we investigated the presence of Ornithodoros ticks in rodent burrows in 34 sites distributed across Morocco. We also collected small mammals in 10 sites and we investigated TBRF in febrile patients in Kenitra district. The prevalence of Borrelia infections was assessed by nested PCR amplification in ticks and the brain tissue of small mammals, and by evaluation of thick blood films in patients. A high proportion of burrows were infested with ticks of the O. erraticus complex in all regions of Morocco, with a mean of 39.5% for the whole country. Borrelia infections were found in 39/382 (10.2%) of the ticks and 12/140 (8.6%) of the rodents and insectivores studied by PCR amplification, and 102 patients tested positive by thick blood film. Five small mammalian species were found infected: Dipodillus campestris, Meriones shawi, Gerbillus hoogstrali, Gerbillus occiduus and Atelerix algirus. Three Borrelia species were identified in ticks and/or rodents: B. hispanica, B. crocidurae and B. merionesi.Conclusions/SignificanceTick populations belonging to O. erraticus complex are widely distributed in Morocco and a high proportion of ticks and small mammals are infected by Borrelia species. Although rarely diagnosed, TBRF may be a common cause of morbidity in all regions of Morocco.
Highlights
Tick-borne relapsing fever (TBRF) due to Borrelia infections transmitted by Argasid ticks of the genus Ornithodoros is a major cause of disease in several regions of Africa
In Eastern and Southern Africa, tick-borne relapsing fever (TBRF) is due to B. duttoni with O. moubata and O. porcinus as vectors; in West Africa and the most arid parts of North Africa, TBRF is due to B. crocidurae with O. sonrai as the vector; whereas in coastal areas of North Africa, TBRF is due to B. hispanica with O. erraticus as the vector [3,4,5,6,7]
Our aim was to systematically investigate the distribution of O. erraticus s.l. in most regions of Morocco, to measure the proportion of infected ticks, to identify small mammalian species that act as potential reservoir, and to analyze data on TBRF patients fortuitously collected during a malaria eradication program
Summary
Tick-borne relapsing fever (TBRF) due to Borrelia infections transmitted by Argasid ticks of the genus Ornithodoros is a major cause of disease in several regions of Africa. In Eastern and Southern Africa, TBRF is due to B. duttoni with O. moubata and O. porcinus as vectors; in West Africa and the most arid parts of North Africa, TBRF is due to B. crocidurae with O. sonrai as the vector; whereas in coastal areas of North Africa, TBRF is due to B. hispanica with O. erraticus as the vector [3,4,5,6,7]. Both in West and North Africa, small mammals act as reservoirs of Borrelia infections [3,5]. The presence in Morocco of Argasid ticks of the Ornithodoros erraticus complex, the vector of tick-borne relapsing fever (TBRF) in North Africa, has been known since 1919, but the disease is rarely diagnosed and few epidemiological data are available
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