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SHORT RESEARCH COMMUNICATION
Year : 2022 | Volume
: 59
| Issue : 2 | Page : 186-189
Seroprevalence study of Toscana virus in Yafran area, Libya
Walid K Saadawi1, Faraj Dhu Abozaid1, Muteia Almukhtar1, Badereddin B Annajar2, Taher Shaibi3
1 National Centre for Disease Control, Ministry of Health, Tripoli, Libya
2 National Centre for Disease Control, Ministry of Health, Tripoli; Public Health Department, Faculty of Medical Technology, University of Tripoli, Tripoli, Libya
3 National Centre for Disease Control, Ministry of Health, Tripoli; Zoology Department, Faculty of Science, University of Tripoli, Libya
Correspondence Address:
Walid K Saadawi
National Centre for Disease Control, Ministry of Health, Tripoli
Libya
Source of Support: None, Conflict of Interest: None
CheckDOI: 10.4103/0972-9062.335728
Background & objectives: In Mediterranean countries, infection of Toscana virus is a public health problem during the summer season, related to sandflies activity; it may cause aseptic meningitis and mild meningoencephalitis. We investigated the presence of antibodies (IgG) against the Toscana virus in the sera of individuals living in the area of Yafran, Libya.
Methods: During the period from December 2013 to February 2014, a total of 232 sera samples were collected from Yefran hospital. Demographic information of participants collected in a questionnaire; samples were analyzed by the serological method of enzyme-linked immunoassays specific for Toscana IgG antibodies.
Results: Seroprevalence of IgG antibodies among samples was 25% (n = 232). Seroprevalence varied among genders, age groups. The differences were not statically significant.
Interpretation & conclusion: Our findings indicate and confirm local circulation of the Toscana virus. It also indicates that TOSV infection is neglected, and needs to be considered as one of the causes of meningitis or meningoencephalitis.
Keywords: TOSV; Seroprevalence; Yefran; Libya
Toscana virus (TOSV), an arbovirus belonging to the genus Phlebovirus family Bunyaviridae, is transmitted to humans through Phlebotomine sandflies bites, which is also the vector for leishmaniasis[1]. TOSV is an enveloped virus with three segments of single-stranded, negative-sense RNA[2],[3], first isolated in Tuscany, central Italy from the sandfly Phlebotomus perniciosus in 1971[4]. TOSV is recurrent during the summer season, with a peak in August, due to the fact that the summer season is the activity period of the species of the genus Phlebotomus[5]. The most common presentation is an acute febrile illness or meningitis, and more rarely a meningoencephalitis causing central nervous system infection[6]. The clinical finding is very hard in non-endemic areas and may be mistaken as other diseases such as influenza; in addition, serological diagnosis may be negative during the early stages[4],[7]. Earlier, the infection of TOSV has been reported in the northern shores countries around the Mediterranean Sea (Italy, Croatia, France, Greece, Portugal and Spain), as well as in the east (Cyprus and Turkey) and recently, from neighboring countries of Libya (Tunisia, Egypt, Algeria) as well as Morocco[8]. There is a scarcity in studies regarding the occurrence of three-day fever in Libya. Antibodies for two types of Sand Fly Viruses (SFV) were detected in the serological survey conducted in 2008, indicating past exposure[9]. This study aimed to investigate the presence of antibodies (IgG) for the Toscana virus in the serum of individuals living in the area of Yafran.
Material & MethodsStudy area
The study was conducted in Yafran Area. Yafran is a town located in southwest of Tripoli in Jabal Nafusah (Nafusah Mountain or Western Mountain) 12° 55› E, 32° 08› N, 691 meters above the sea level[10]. It is a semi-arid area; the annual rainfall average is about 90 mm, in January the temperature average about 6°C and increases to 42°C in July. Olive trees, fig trees, and wild aromatic herbs grow in this area. Jabal Nafusah is considered an endemic area of leishmaniasis[11].
Specimen collection
A total of 232 blood samples were collected from patients who attended Yefran hospital for laboratory investigations; between December 2013 and February 2014, regardless of their health situation and whether they had sandfly fever symptoms or not. Blood samples were taken by venipuncture; sera were separated by centrifugation and stored at -20°C until tested. Each participant filled out a questionnaire in which the following variables were registered; age, gender, occupation, area of residence, blood transfusion, the history of contact with domestic animals, and traveling history. No data regarding race were obtained.
Serological technique
Sera were sent to the Parasitology and Vector-Borne Disease Research Laboratory at the National Centre for Disease Control (NCDC), Tripoli, Libya; where they were tested by the serological method of enzyme-linked immunoassays (ELISA) to detect the presence of Toscana IgG antibodies using a commercial enzyme immunoassay kit, (AXIOM Diagnostic, Worms, Germany), according to the manufacturer’s instructions.
Statistical analysis
Seroprevalence of antibodies to TOSV was calculated as the ratio between positive sera and all tested sera. Chi square test to evaluate if the prevalence by demographic data was statistically significant (p ≤ 0.05). All collected data were analyzed statistically using statistical package for the social sciences program (SPSS) version 20.0 software[12].
Ethical statement
All the participants in this study signed an informed consents form, and the Libyan National Committee of Biosecurity and Bioethics approved the study (Reference 52-13).
ResultsA total of 232 sera samples collected, among them 106 (45.7%) male and 136 (54.3%) female, sex ratio was 0.84. The median age was 32.0 years (range: 1–88). [Table 1] shows the demographic characteristics of sample collected (n = 232). 25.0% (n=58) were positive for TOSV IgG antibody.
Seroprevalence varied between male (20.8%) and female (28.6%), the difference was not significant (χ2 = 1.876, df= 1, p = 0.171). All groups of age showed positive result with different rate, the highest positivity rate was 43.8% among age group 61–75 years, while the lowest was 20.6% in age group 16–30; statistically, no significant difference was seen between age groups (χ2 = 5.534, df = 5, p = 0.354). Out of 58 seropositive participants 36 (62%) had no history of travel outside Libya, 56 (96.6%) has no history of blood transfusion and 35 (60.3%) don’t use insecticides inside their homes. Diabetic participants showed higher seroprevalence (30.8%) than non-diabetic (23.3%); this difference was not significant (χ2 = 1.190, df = 1, p = 0.275).
DiscussionTOSV is an emerging virus in the Mediterranean basin and recognized as one of the most common causes of meningitis[3], and meningoencephalitis during the summer the time of sand fly activity[8]. Infection of TOSV in Mediterranean countries has been demonstrated to be endemic in several studies[13]. In this study, we investigate the past exposure of TOSV in Libya by detection of IgG antibodies among collected serum samples from Yafran area, and we reported seroprevalence rate for antibodies to TOSV in 25% (58/232).
Previous studies have shown seroprevalence rates between 23% and 30% in Italy[14],[15], 21.4% in southeastern France[16], 24.9% in Spain[17], 37.5% in Croatia[18]. Moreover, studies in Tunisia, the neighboring North African country, have demonstrated lower seroprevalence (9.5%)[13], and (12.16%)[19], this difference between seroprevalence rates may be due to the different climate of Yafran, which may be responsible for abounding of sandflies.
In Libya, studies about the presence or circulation of TOSV nor other sandflies-borne viruses are very scant. However, serological surveys to define viral and bacterial etiologies causing acute febrile illness, confirmed the presence of antibodies in humans against arbovirus including; Sandfly Naples and Sandfly Sicilian with very low prevalence rates (0.5%), and (0.7%) respectively[9]. The lack of case reports of hospitals may be due to weak knowledge of the actual virus epidemiology in the country and shortage of laboratory diagnosis facilities. Moreover, patients with TOSV infections are asymptomatic or paucisymptomatic; and they are not usually hospitalized, this can explain seroprevalence and the number of severe cases reported in the literature[20].
In epidemiological study, ELISA technique is recommended[13], therefore, our serological tests were performed by ELISA with recombinant nucleoprotein, and its sensitivity was 95% and specificity was 96.5%; cross-reactivity between TOSV and other serotypes of genus Phlebovirus cannot be excluded[20],[21]. TOSV is transmitted by phlebotomine sandflies (Phlebotomus spp. of the subgenus Laroussius)[2],[22], precisely P. perniciosus and P. perfiliewi[23], interestingly; the presence of those two species was not completely confirmed or approved especially in the northwestern region of Libya. In general, species of subgenus Laroussius are very difficult to be morphologically distinguished[24]; our result indicates that TOSV vector exists in Yafran area, therefore intensive entomological study should be conducted. IgG seroprevalence in this study confirms past exposure of the virus, particularly that a major part of participants (62%) have no history of travel outside the country, therefore we recommend that physicians to do not exclude possible TOSV infection in meningitis or meningoencephalitis cases.
Conflict of interest: None
AcknowledgementsThe authors thank management and laboratory team members in Yafran hospital for the help during sample collection. We also thank Parasitology and Vector-Borne Disease Research Laboratory team at NCDC-Libya for providing diagnostic kits and facilities.
References
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