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    Evolution of malaria and Rickettsia felis infection morbidity in Dielmo and Ndiop villages, Senegal, in 2013–2016. This figure appears in color at www.ajtmh.org.

  • 1.

    Angelakis E, Mediannikov O, Parola P, Raoult D, 2016. Rickettsia felis: the complex journey of an emergent human pathogen. Trends Parasitol 32: 554564.

    • Search Google Scholar
    • Export Citation
  • 2.

    Raoult D, La Scola B, Enea M, Fournier PE, Roux V, Fenollar F, Galvao MA, de Lamballerie X, 2001. A flea-associated Rickettsia pathogenic for humans. Emerg Infect Dis 7: 7381.

    • Search Google Scholar
    • Export Citation
  • 3.

    Brown LD, Macaluso KR, 2016. Rickettsia felis, an emerging flea-borne rickettsiosis. Curr Trop Med Rep 3: 2739.

  • 4.

    Richards AL, Jiang J, Omulo S, Dare R, Abdirahman K, Ali A, Sharif SK, Feikin DR, Breiman RF, Njenga MK, 2010. Human infection with Rickettsia felis, Kenya. Emerg Infect Dis 16: 10811086.

    • Search Google Scholar
    • Export Citation
  • 5.

    Mediannikov O 2013. Common epidemiology of Rickettsia felis infection and malaria, Africa. Emerg Infect Dis 19: 17751783.

  • 6.

    Roucher C, Mediannikov O, Diatta G, Trape JF, Raoult D, 2012. A new Rickettsia species found in fleas collected from human dwellings and from domestic cats and dogs in Senegal. Vector Borne Zoonotic Dis 12: 360365.

    • Search Google Scholar
    • Export Citation
  • 7.

    Parola P, Mediannikov O, Dieme C, Raoult D, 2015. Reply to Slesak et al.: so much about Rickettsia felis infection to be discovered. Proc Natl Acad Sci USA 112: E6595E6596.

    • Search Google Scholar
    • Export Citation
  • 8.

    Socolovschi C, Pages F, Ndiath MO, Ratmanov P, Raoult D, 2012. Rickettsia species in African Anopheles mosquitoes. PLoS One 7: e48254.

  • 9.

    Dieme C, Bechah Y, Socolovschi C, Audoly G, Berenger JM, Faye O, Raoult D, Parola P, 2015. Transmission potential of Rickettsia felis infection by Anopheles gambiae mosquitoes. Proc Natl Acad Sci USA 112: 80888093.

    • Search Google Scholar
    • Export Citation
  • 10.

    Sokhna C, Mediannikov O, Fenollar F, Bassene H, Diatta G, Tall A, Trape JF, Drancourt M, Raoult D, 2013. Point-of-care laboratory of pathogen diagnosis in rural Senegal. PLoS Negl Trop Dis 7: e1999.

    • Search Google Scholar
    • Export Citation
  • 11.

    Wotodjo AN 2015. The implication of long-lasting insecticide-treated net use in the resurgence of malaria morbidity in a Senegal malaria endemic village in 2010–2011. Parasit Vectors 8: 267.

    • Search Google Scholar
    • Export Citation

 

 

 

 

 

Parallel Decline of Malaria and Rickettsia felis Infections in Senegal

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  • 1 Aix-Marseille Univ, IRD, APHM, MEPHI, IHU-Méditerranée Infection, Marseille, France;
  • 2 Aix-Marseille Univ, IRD, APHM, VITROME, IHU-Méditerranée Infection, Marseille, France;
  • 3 Campus International IRD-UCAD Hann Maristes, Dakar, Senegal

Rickettsia felis is a common emerging pathogen in sub-Saharan Africa. Comparing dynamics of morbidities due to malaria and R. felis infections in two Senegalese villages, we found a strong and significant correlation between them. Malaria morbidity is strongly decreasing because of the implementation of long-lasting insecticidal nets, so we hypothesize that the same measure may decrease the R. felis infections.

Ricketsia felis is a worldwide emerging arthropod-borne pathogen. It was described as a human pathogen in 1991.1 Then, the detection of R. felis in laboratory-reared colonies of cat fleas, Ctenocephalides felis, drove scientists to the conclusion that this bacterium is hosted and transmitted by fleas.1 Numerous detections of R. felis in fleas collected from wild and domestic animals all around the world confirmed this hypothesis. The disease associated with R. felis has been named as “flea-borne spotted fever.”2 Multiple laboratory experiments confirmed that R. felis may be transmitted by cat fleas.3 However, until 2010, R. felis cases were very rarely reported. The disease has become increasingly more recognized in the tropical countries of Africa4 and Asia1 after simultaneous reports of high prevalence of R. felis infection in Kenya4 and in Senegal5 had been published. It was reported that fleas collected in an R. felis–endemic region in Senegal did not contain this bacterium6; this may suggest that another transmission mechanism exists. Moreover, it appears that the epidemiologies of malaria and R. felis infection in Senegal are very similar.5

These observations led us to the hypothesis that R. felis may be transmitted by mosquitoes in tropical countries.79 We have reported the correlation between mosquito-transmitted malaria and R. felis infection regarding geographic distribution, seasonality, asymptomatic infections, and a potential vector.5 Ricketsia felis has been also detected in wild Anopheles and in Aedes.8 Later, the ability of Anopheles mosquitoes to acquire and transmit R. felis to susceptible hosts was proven in an experimental model.79 Here, we report additional evidence of the connecting epidemiologies of both diseases. Dielmo and Ndiop are two villages in the Sine-Saloum region of Senegal situated 5 km from each other, with a total population about 800 persons and where the point-of-care laboratory was installed in 201110 to perform rapid detection of both pathogens. This laboratory serves two village dispensaries where all cases of acute febrile diseases are reported. The diagnosis is performed by using quantitative polymerase chain reaction and rapid diagnostic immunochromatographic tests. We analyzed the total monthly number of cases of malaria and R. felis infection in both villages for the period from August 2013 to October 2016, including the episode of malaria rebound in 2013.11 Over the study period, 236 and 28 human cases of malaria and R. felis, respectively, were identified. Figure 1 illustrates the dynamics of monthly number of cases of these infections. Both curves show the same peaks and declines. Using the R software (R Project, Auckland, New Zealand), we performed a Pearson correlation test to determine if there was a correlation between the cases of malaria and that of R. felis throughout the study period. Intriguingly, we identified a strong and significant correlation between the appearance and disappearance of the two diseases (correlation coefficient equal to 0.6, P value < 10−3).

Figure 1.
Figure 1.

Evolution of malaria and Rickettsia felis infection morbidity in Dielmo and Ndiop villages, Senegal, in 2013–2016. This figure appears in color at www.ajtmh.org.

Citation: The American Journal of Tropical Medicine and Hygiene 99, 2; 10.4269/ajtmh.17-0194

Long-lasting insecticide-treated nets (LLIN) marked a real breakthrough in malaria prevention, resulting in a significant decline in morbidity and mortality. It seems that the renewal of LLIN in 2013 helped to stop malaria10 and R. felis infection rebound in Dielmo. As the growing number of cases of R. felis infection dropped to zero at the same time, it seems that this effective tool to reduce malaria burden may also decrease the number of acute R. felis infection cases. The strong significant correlation between the number of cases of R. felis infection and that of malaria further reinforces the hypothesis that most cases of R. felis infection in tropical areas may be transmitted by mosquitoes, in particular Anopheles spp.

REFERENCES

  • 1.

    Angelakis E, Mediannikov O, Parola P, Raoult D, 2016. Rickettsia felis: the complex journey of an emergent human pathogen. Trends Parasitol 32: 554564.

    • Search Google Scholar
    • Export Citation
  • 2.

    Raoult D, La Scola B, Enea M, Fournier PE, Roux V, Fenollar F, Galvao MA, de Lamballerie X, 2001. A flea-associated Rickettsia pathogenic for humans. Emerg Infect Dis 7: 7381.

    • Search Google Scholar
    • Export Citation
  • 3.

    Brown LD, Macaluso KR, 2016. Rickettsia felis, an emerging flea-borne rickettsiosis. Curr Trop Med Rep 3: 2739.

  • 4.

    Richards AL, Jiang J, Omulo S, Dare R, Abdirahman K, Ali A, Sharif SK, Feikin DR, Breiman RF, Njenga MK, 2010. Human infection with Rickettsia felis, Kenya. Emerg Infect Dis 16: 10811086.

    • Search Google Scholar
    • Export Citation
  • 5.

    Mediannikov O 2013. Common epidemiology of Rickettsia felis infection and malaria, Africa. Emerg Infect Dis 19: 17751783.

  • 6.

    Roucher C, Mediannikov O, Diatta G, Trape JF, Raoult D, 2012. A new Rickettsia species found in fleas collected from human dwellings and from domestic cats and dogs in Senegal. Vector Borne Zoonotic Dis 12: 360365.

    • Search Google Scholar
    • Export Citation
  • 7.

    Parola P, Mediannikov O, Dieme C, Raoult D, 2015. Reply to Slesak et al.: so much about Rickettsia felis infection to be discovered. Proc Natl Acad Sci USA 112: E6595E6596.

    • Search Google Scholar
    • Export Citation
  • 8.

    Socolovschi C, Pages F, Ndiath MO, Ratmanov P, Raoult D, 2012. Rickettsia species in African Anopheles mosquitoes. PLoS One 7: e48254.

  • 9.

    Dieme C, Bechah Y, Socolovschi C, Audoly G, Berenger JM, Faye O, Raoult D, Parola P, 2015. Transmission potential of Rickettsia felis infection by Anopheles gambiae mosquitoes. Proc Natl Acad Sci USA 112: 80888093.

    • Search Google Scholar
    • Export Citation
  • 10.

    Sokhna C, Mediannikov O, Fenollar F, Bassene H, Diatta G, Tall A, Trape JF, Drancourt M, Raoult D, 2013. Point-of-care laboratory of pathogen diagnosis in rural Senegal. PLoS Negl Trop Dis 7: e1999.

    • Search Google Scholar
    • Export Citation
  • 11.

    Wotodjo AN 2015. The implication of long-lasting insecticide-treated net use in the resurgence of malaria morbidity in a Senegal malaria endemic village in 2010–2011. Parasit Vectors 8: 267.

    • Search Google Scholar
    • Export Citation

Author Notes

Address correspondence to Didier Raoult, URMITE, Aix Marseille University, UM63, CNRS 7278, IRD 198, INSERM 1095, Institut Hospitalo-Universitaire (IHU) Méditerranée Infection, 19-21 Boulevard Jean Moulin, Marseille 13385, France. E-mail: didier.raoult@gmail.com

Authors’ addresses: Oleg Mediannikov, URMITE, Aix Marseille University, UM63, CNRS 7278, IRD 198, INSERM 1095, Institut Hospitalo-Universitaire (IHU) Méditerranée Infection, Marseille, France, and IRD, URMITE UMR198, Campus Communs IRD/UCAD Hann Maristes, Dakar, Senegal, E-mail: olegusss1@gmail.com. Cédric Abat and Didier Raoult, URMITE, Aix Marseille University, UM63, CNRS 7278, IRD 198, INSERM 1095, Institut Hospitalo-Universitaire (IHU) Méditerranée Infection, Marseille, France, E-mails: cedric.abat@gmail.com and didier.raoult@gmail.com. Cheikh Sokhna, URMITE, Campus IRD d’ Hann Maristes, Dakar, Senegal, E-mail: cheikh.sokhna@ird.fr.

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