Serological evidence of Francisella tularensis in febrile patients seeking treatment at remote hospitals, northeastern Kenya, 2014–2015

Abstract

Tularaemia is a highly contagious infectious zoonosis caused by the bacterial agent Francisella tularensis. The aim of this study was to investigate the presence of antibodies to F. tularensis in febrile patients in northeastern Kenya. During 2014–2015, 730 patients were screened for anti-F. tularensis antibodies using a combination of ELISA and Western blot. Twenty-seven (3.7%) individuals were positive for F. tularensis. Tularaemia was not suspected by the treating clinicians in any of them. Our results suggest that tularaemia may be present in Kenya but remain unreported, and emphasizes the need for local clinicians to broaden their diagnostic repertoire when evaluating patients with undifferentiated febrile illness.

Francisella tularensis, Tularemia and Serological Diagnosis

“…As indicated before, the risk of false-positive results due to antigenic cross-reactions increases when considering low antibody titers (Syrjälä et al, 1986). In some studies, authors confirmed positive serological tests using Western blot to reduce false-positive results caused by antigenic cross-reactions (Jenzora et al, 2008;Splettstoesser et al, 2009;Zaḱutnáet al, 2015;Njeru et al, 2017). Besides, in many instances, the Western blot did not confirm positive ELISA tests, especially when ELISA titers were just above the cutoffs (Schmitt et al, 2005;Rossow et al, 2015).…”

“…The immunoblotting technique has been proposed as a confirmatory test in patients with positive MAT, IFA, or ELISA tests. The ladder-like band pattern obtained with F. tularensis LPS is considered as typical for this species (Porsch-Ozcürümez et al, 2004;Schmitt et al, 2005;Jenzora et al, 2008;Chaignat et al, 2014;Rossow et al, 2015;Zaḱutnáet al, 2015;Njeru et al, 2017). However, in many studies, western blot could not confirm a large number of positive tests obtained with other methods (Porsch-Ozcürümez et al, 2004;Schmitt et al, 2005;Rossow et al, 2015;Zaḱutnáet al, 2015;Njeru et al, 2017).…”

“…Recently, Njeru et al (2017) evaluated the tularemia seroprevalence in 730 febrile patients (335 men and 395 women, 652 adults and 78 children) hospitalized in Garissa and Wajir hospitals (northeastern Kenya) in 2014-2015. The Serazym ® ELISA tests detected 71 (9.7%) positive samples, of which only 27 (3.7%) were confirmed by Western blot.…”

“…These studies have evaluated the tularemia seroprevalence in specific areas, either in the general population or in specific groups of individuals. ELISA tests were performed in most recent studies because they allow easy testing of a large number of serum samples (Jenzora et al, 2008;Splettstoesser et al, 2009;Zaḱutnáet al, 2015;Büyük et al, 2016;Njeru et al, 2017;Esmaeili et al, 2019). Overall, most studies have reported low seroprevalences (0.19 to 4%) in the general populations studied (Koskela and Herva, 1982b;Gutieŕrez et al, 2003;Porsch-Ozcürümez et al, 2004;Schmitt et al, 2005;Jenzora et al, 2008;Splettstoesser et al, 2009;Tobudic et al, 2014;Rossow et al, 2015;Zaḱutnáet al, 2015;De Keukeleire et al, 2017;Njeru et al, 2017;Akhvlediani et al, 2018).…”

“…ELISA tests were performed in most recent studies because they allow easy testing of a large number of serum samples (Jenzora et al, 2008;Splettstoesser et al, 2009;Zaḱutnáet al, 2015;Büyük et al, 2016;Njeru et al, 2017;Esmaeili et al, 2019). Overall, most studies have reported low seroprevalences (0.19 to 4%) in the general populations studied (Koskela and Herva, 1982b;Gutieŕrez et al, 2003;Porsch-Ozcürümez et al, 2004;Schmitt et al, 2005;Jenzora et al, 2008;Splettstoesser et al, 2009;Tobudic et al, 2014;Rossow et al, 2015;Zaḱutnáet al, 2015;De Keukeleire et al, 2017;Njeru et al, 2017;Akhvlediani et al, 2018). Higher seroprevalences (5.02 to 18%) have been reported in tularemia highly endemic areas, in rural populations, in hunters, and in specific occupational groups (including farmers, butchers, slaughterhouse workers, ranchers, and park workers) (Feldman, 2003;Splettstoesser et al, 2009;Clark et al, 2012;Esmaeili et al, 2014a;Esmaeili et al, 2014b;Büyük et al, 2016;Gazi et al, 2016;Akhvlediani et al, 2018;Esmaeili et al, 2019;Harrist et al, 2019).…”