Modeling and comparative study of the spread of zoonotic visceral leishmaniasis from Northern to Central Tunisia.

During the last twenty years, zoonotic visceral leishmaniasis (ZVL) spread from the north characterized by humid, sub-humid, and semi-arid bio-climates to the arid areas located in Central Tunisia. In order to understand the eco-epidemiological factors involved in the distribution of ZVL, both a sero-epidemiological and an entomological investigation were performed in two governorates situated in two different bio-geographical areas: Bizerte in the north and Kairouan in the center. A mathematical model for transmission of ZVL was built, describing the disease dynamic in these areas. Among 108 sera collected from clinically healthy owned dogs used for guarding houses in the governorate of Bizerte and tested for anti-L. infantum antibodies by indirect immune-fluorescence antibody test (IFAT), 8.3% were positive. From a total of 191 serum samples collected from clinically healthy owned dogs used for guarding houses in the governorate of Kairouan and tested for anti-L. infantum antibodies by IFAT, 26.7% were sero-positive. The cumulative incidences of ZVL in humans in the governorates of Bizerte and Kairouan were 39.17/100,000 and 0.2/100,000 inhabitants, respectively. The infection rates of sand flies with Leishmania DNA in the governorate of Bizerte and Kairouan were 3.8% and 9.4%, respectively. It is important to point out that ZVL epidemic in humans is preceded or concomitant to a high prevalence of Leishmania infantum in dogs and in sand flies. The model showed also a non-linear relationship between dog infection and ZVL in humans. These results suggest an important force of infection (R0) in emerging foci such as the governorate of Kairouan leading to an increased incidence of ZCL in humans. A high prevalence of L. infantum in dogs will result in high prevalence in the vector and obviously high probability to infect human; that it is a key factor for triggering transmission to humans, and subsequently it is an important parameter in the control of ZVL transmission.

Kaabi B ，Zhioua E 《-》

Co-circulation of Toscana virus and Leishmania infantum in a focus of zoonotic visceral leishmaniasis from Central Tunisia.

In the Mediterranean basin, sand flies are vectors of Leishmania parasites and phleboviruses affecting humans and animals. In this study, we aimed to investigate phlebovirus and Leishmania parasites circulating in a focus of zoonotic visceral leishmaniasis (ZVL) located in a highly irrigated area within the arid Central Tunisia, known mainly to be endemic for zoonotic cutaenous leishmaniasis (ZCL) caused Leishmania major and transmitted by Phlebotomus papatasi. Sand flies were collected using CDC light traps in the village of Saddaguia, an emergent focus of ZVL located in Central Tunisia during September-October 2014, 2015, and 2016. Pools of live female sand flies were screened for phleboviruses and Leishmania by nested PCR in the polymerase gene and kinetoplast minicircle DNA, respectively. Dead sand flies were identified morphologically to species level. Sand flies of the subgenus Larroussius mainly Phlebotomus perfiliewi, Phlebotomus perniciosus, and Phlebotomus longicuspis were predominant in this ZVL focus compared to P. papatasi. A total of 1932, 1740, and 444 sand flies were tested in 2014, 2015 and 2016, respectively. Pathogen screening performed on 4116 sand flies distributed in 148 pools revealed the presence of Leishmania infantum and Toscana virus. The minimum infection rates of sand flies with TOSV in 2014, 2015, and 2016 were 0.05%, 011%, and 0.22%, respectively. The minimum infection rates of sand flies with L. infantum in 2014, 2015, and 2016 were 0.25%, 012%, and 0.79%, respectively. No L. major was detected during the 3-years investigation in this ZVL focus. Our results showed clearly the endemic co-circulation of TOSV and L. infantum in this emergent ZVL focus. However, no co-infection of TOSV and L. infantum was detected in any of the sand fly pools investigated during the three years period. TOSV was isolated from positive pools in 2015. Phylogenetic analysis showed that the Tunisian strains of TOSV belonged to the sublineage A. Based on the present findings, our results provided strong evidence that TOSV and L. infantum are transmitted by the same predominant sand fly species of the subgenus Larroussius, and subsequently, humans and dogs could be co-infected through co-infected or successive infected bites. Our results showed clearly that the development of irrigation in arid areas contributed significantly to the establishment of stable transmission cycles of L. infantum and TOSV and subsequently to the emergence of a ZVL focus within this arid bio-geographical area characterized by the presence of multiple foci of ZCL located outside the study site. Thus, more studies are needed to better understand the impact of RNA viruses shared by vectors and reservoir hosts of L. infantum on the development of zoonotic visceral leishmaniasis.

Fares W ，Dachraoui K ，Barhoumi W ，Cherni S ，Chelbi I ，Zhioua E ... -  《-》

Changes of Sand Fly Populations and Leishmania infantum Infection Rates in an Irrigated Village Located in Arid Central Tunisia.

Barhoumi W ，Fares W ，Cherni S ，Derbali M ，Dachraoui K ，Chelbi I ，Ramalho-Ortigao M ，Beier JC ，Zhioua E ... -  《-》

Interaction between canine and human visceral leishmaniases in a holoendemic focus of Central Tunisia.

Canine visceral leishmaniasis (CVL) is endemic in the Mediterranean basin. In Tunisia, CVL is spatially associated with human visceral leishmaniasis (HVL) affecting mostly children younger than 5 years old. In this study, seroprevalence of Leishmania infantum infection in dogs was assessed in highly endemic districts of the governorate of Kairouan where more than 50% of HVL cases in Tunisia were reported. An entomological investigation was also carried out in two endemic districts (Bouhajla and Haffouz) to assess sand fly fauna and infection status of sand flies with Leishmania. A total of 191 serum samples were collected from healthy dogs and tested for anti-L. infantum antibodies by indirect immunofluorescence antibody test (IFAT). Overall seroprevalence for L. infantum was 26.7% being highest among dogs in the district of Bouhajla (52.7%) and the lowest in the district of Chbika (5.2%). In dogs, seroprevalence did not differ significantly based on gender or age, with dogs younger than 1 year showing a higher seroprevalence compared to older dogs. These findings suggest strong force of infection in naïve animals in holoendemic regions leading to emerging high incidence of HVL. Concomitant to the high CVL prevalence observed in the Bouhajla district, a significantly high cumulative HVL incidence also was observed in this district. Phlebotomus perniciosus and Phlebotomus longicuspis were the most abundant sand fly species in Bouhajla and Haffouz districts. The rate of Leishmania-DNA infection in sand flies was 9.4%. This finding points to spatial correlation between the occurrence of disease in humans, a high rate of infection in dogs and a high abundance of P. pernicious and P. longicuspis. Thus, CVL is the main risk factor for transmission to humans and subsequently, it is an important parameter for controlling transmission to humans.

Zoghlami Z ，Chouihi E ，Barhoumi W ，Dachraoui K ，Massoudi N ，Helel KB ，Habboul Z ，Hadhri MH ，Limam S ，Mhadhbi M ，Gharbi M ，Zhioua E ... -  《-》

[Epidemiology of Leishmania (L.) infantum, L. major and L. killicki in Tunisia: results and analysis of the identification of 226 human and canine isolates].

Aoun K ，Amri F ，Chouihi E ，Haouas N ，Bedoui K ，Benikhlef R ，Ghrab J ，Babba H ，Chahed MK ，Harrat Z ，Bouratbine A ... -  《-》