Zoonotic cutaneous leishmaniasis in central Tunisia

Spatio-temporal dynamics

Afif Ben Salah, Yiannis Kamarianakis, Sadok Chlif, Nissaf Ben Alaya, Poulicos Prastacos

Research output: Contribution to journalArticle

57 Citations (Scopus)

Abstract

Background: Zoonotic cutaneous leishmaniasis (ZCL) is endemic in many rural areas of the Southern and Eastern Mediterranean region where different transmission patterns of the disease have been described. This study was carried out in a region located in Central Tunisia and aimed to investigate the spatio-temporal dynamics of the disease from 1999 to 2004. Methods: Incident ZCL cases were defined by clinical diagnosis, confirmed by a positive skin test and/or parasitological examination. Annual ZCL rates were calculated for 94 regional sectors that comprise the study region of Sidi-Bouzid. Spatial and temporal homogeneity were initially investigated by chi-squared tests. Next, spatial scan statistics were used to identify spatial, temporal and spatio-temporal clusters that display abnormally high incidence rates. A hierarchical Bayesian Poisson regression model with spatial effects was fitted to signify explanatory socio-geographic factors related to spatial rate variability. Temporal ZCL dynamics for the 94 sectors were described via a linear mixed model. Results: A total of 15 897 ZCL cases were reported in the 6-year study period, with an annual incidence rate of 669.7/100 000. An outbreak of the disease was detected in 2004 (1114/100 000). Spatial clustering is evident for the whole time period. The most likely cluster according to the spatial scan statistic, contains seven sectors with abnormally high incidence rates and ∼5% of the total population. ZCL rates per sector are mostly related to the urban/rural index; sectoral population density and the number of inhabitants per household do not appear to contribute much to the explanation of rate variability. The dynamics of the disease within the study period are satisfactorily described by quadratic curves that differ for urban and rural areas. Conclusions: ZCL rates vary across space and time; rural/urban areas and environmental factors may explain part of this variation. In the study region, the Sidi Saâd dam - constructed in the early eighties and identified by previous studies as a major reason for the first outbreak of the disease - seems to be still related to increased ZCL rates. The most likely spatial cluster of high incidence rates contains regions located close to the dam. Our findings of increased incidences in urban areas support the hypothesis of increased incidences in peri-urban environments due to changes in sandfly/rodent living habits over recent years.

Original languageEnglish (US)
Pages (from-to)991-1000
Number of pages10
JournalInternational Journal of Epidemiology
Volume36
Issue number5
DOIs
StatePublished - Oct 2007
Externally publishedYes

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Tunisia
Cutaneous Leishmaniasis
Zoonoses
Incidence
Disease Outbreaks
Mediterranean Region
Psychodidae
Geography
Population Density
Skin Tests
Habits
Cluster Analysis
Rodentia
Linear Models

Keywords

  • Spatial clustering
  • Spatio-temporal dynamics
  • Zoonotic cutaneous leishmaniasis

ASJC Scopus subject areas

  • Epidemiology

Cite this

Salah, A. B., Kamarianakis, Y., Chlif, S., Alaya, N. B., & Prastacos, P. (2007). Zoonotic cutaneous leishmaniasis in central Tunisia: Spatio-temporal dynamics. International Journal of Epidemiology, 36(5), 991-1000. https://doi.org/10.1093/ije/dym125

Zoonotic cutaneous leishmaniasis in central Tunisia : Spatio-temporal dynamics. / Salah, Afif Ben; Kamarianakis, Yiannis; Chlif, Sadok; Alaya, Nissaf Ben; Prastacos, Poulicos.

In: International Journal of Epidemiology, Vol. 36, No. 5, 10.2007, p. 991-1000.

Research output: Contribution to journalArticle

Salah, AB, Kamarianakis, Y, Chlif, S, Alaya, NB & Prastacos, P 2007, 'Zoonotic cutaneous leishmaniasis in central Tunisia: Spatio-temporal dynamics', International Journal of Epidemiology, vol. 36, no. 5, pp. 991-1000. https://doi.org/10.1093/ije/dym125
Salah, Afif Ben ; Kamarianakis, Yiannis ; Chlif, Sadok ; Alaya, Nissaf Ben ; Prastacos, Poulicos. / Zoonotic cutaneous leishmaniasis in central Tunisia : Spatio-temporal dynamics. In: International Journal of Epidemiology. 2007 ; Vol. 36, No. 5. pp. 991-1000.
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abstract = "Background: Zoonotic cutaneous leishmaniasis (ZCL) is endemic in many rural areas of the Southern and Eastern Mediterranean region where different transmission patterns of the disease have been described. This study was carried out in a region located in Central Tunisia and aimed to investigate the spatio-temporal dynamics of the disease from 1999 to 2004. Methods: Incident ZCL cases were defined by clinical diagnosis, confirmed by a positive skin test and/or parasitological examination. Annual ZCL rates were calculated for 94 regional sectors that comprise the study region of Sidi-Bouzid. Spatial and temporal homogeneity were initially investigated by chi-squared tests. Next, spatial scan statistics were used to identify spatial, temporal and spatio-temporal clusters that display abnormally high incidence rates. A hierarchical Bayesian Poisson regression model with spatial effects was fitted to signify explanatory socio-geographic factors related to spatial rate variability. Temporal ZCL dynamics for the 94 sectors were described via a linear mixed model. Results: A total of 15 897 ZCL cases were reported in the 6-year study period, with an annual incidence rate of 669.7/100 000. An outbreak of the disease was detected in 2004 (1114/100 000). Spatial clustering is evident for the whole time period. The most likely cluster according to the spatial scan statistic, contains seven sectors with abnormally high incidence rates and ∼5{\%} of the total population. ZCL rates per sector are mostly related to the urban/rural index; sectoral population density and the number of inhabitants per household do not appear to contribute much to the explanation of rate variability. The dynamics of the disease within the study period are satisfactorily described by quadratic curves that differ for urban and rural areas. Conclusions: ZCL rates vary across space and time; rural/urban areas and environmental factors may explain part of this variation. In the study region, the Sidi Sa{\^a}d dam - constructed in the early eighties and identified by previous studies as a major reason for the first outbreak of the disease - seems to be still related to increased ZCL rates. The most likely spatial cluster of high incidence rates contains regions located close to the dam. Our findings of increased incidences in urban areas support the hypothesis of increased incidences in peri-urban environments due to changes in sandfly/rodent living habits over recent years.",
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N2 - Background: Zoonotic cutaneous leishmaniasis (ZCL) is endemic in many rural areas of the Southern and Eastern Mediterranean region where different transmission patterns of the disease have been described. This study was carried out in a region located in Central Tunisia and aimed to investigate the spatio-temporal dynamics of the disease from 1999 to 2004. Methods: Incident ZCL cases were defined by clinical diagnosis, confirmed by a positive skin test and/or parasitological examination. Annual ZCL rates were calculated for 94 regional sectors that comprise the study region of Sidi-Bouzid. Spatial and temporal homogeneity were initially investigated by chi-squared tests. Next, spatial scan statistics were used to identify spatial, temporal and spatio-temporal clusters that display abnormally high incidence rates. A hierarchical Bayesian Poisson regression model with spatial effects was fitted to signify explanatory socio-geographic factors related to spatial rate variability. Temporal ZCL dynamics for the 94 sectors were described via a linear mixed model. Results: A total of 15 897 ZCL cases were reported in the 6-year study period, with an annual incidence rate of 669.7/100 000. An outbreak of the disease was detected in 2004 (1114/100 000). Spatial clustering is evident for the whole time period. The most likely cluster according to the spatial scan statistic, contains seven sectors with abnormally high incidence rates and ∼5% of the total population. ZCL rates per sector are mostly related to the urban/rural index; sectoral population density and the number of inhabitants per household do not appear to contribute much to the explanation of rate variability. The dynamics of the disease within the study period are satisfactorily described by quadratic curves that differ for urban and rural areas. Conclusions: ZCL rates vary across space and time; rural/urban areas and environmental factors may explain part of this variation. In the study region, the Sidi Saâd dam - constructed in the early eighties and identified by previous studies as a major reason for the first outbreak of the disease - seems to be still related to increased ZCL rates. The most likely spatial cluster of high incidence rates contains regions located close to the dam. Our findings of increased incidences in urban areas support the hypothesis of increased incidences in peri-urban environments due to changes in sandfly/rodent living habits over recent years.

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