Moshe Ephros

Cat scratch disease (CSD), caused by Bartonella henselae, usually presents as regional lymphadenopathy/lymphadenitis, known as typical CSD or as atypical CSD, which includes, among others, neurological manifestations. Serology for anti-B. henselae IgG antibodies is the most commonly used diagnostic tests for CSD. Intravenous immunoglobulin (IVIG) is given for an increasing number of medical conditions and may cause interference with serological testing. We report six patients with neurological manifestations and two patients with Kawasaki disease mimicking typical CSD, mistakenly diagnosed as CSD due to false-positive serology following IVIG therapy. Bartonella IgG serology was positive one to six days after IVIG administration and reverted to negative in seven of eight patients or significantly decreased (1 patient) ≤30 days later. In patients with CSD, IgG titers remained essentially unchanged 15–78 days after the positive serum sample. An additional eight patients treated with IVIG for various conditions were evaluated prospectively. All were seronegative one day pre-IVIG infusion, five patients demonstrated an increase in the IgG titers one to three days after IVIG administration, one interpreted as positive and four as intermediate, whereas three patients remained seronegative, suggesting that false seropositivity after IVIG therapy may not occur in all patients. Treatment with IVIG can result in false-positive serology for B. henselae. Increased awareness to the misleading impact of IVIG is warranted to avoid misinterpretation. Repeat testing can distinguish between true and false serology. Preserving serum samples prior to IVIG administration is suggested.

Leishmania spp. are medically important unicellular parasites transmitted by phlebotomine sand flies. The World Health Organization recently highlighted the importance of reliable diagnostic tools for leishmaniasis. Our study of human infection was conducted in two endemic foci of Leishmania tropica in the Galilee region, northern Israel. Elevated anti-Leishmania antibodies were present in the majority (78.6%) of L. tropica-PCR positive individuals. Moreover, the enzyme-linked immunosorbent assay showed high sensitivity, specificity, and negative and positive predictive values (ranging between 73% and 79%), thus fulfilling the basic requirement for future development of a serodiagnostic and screening tool. The anti-sand fly saliva antibodies used as biomarkers of exposure reflected the composition of the local sand fly fauna as well as the abundance of individual species. High levels of antibodies against vector salivary proteins may further indicate frequent exposure to sand flies and consequently a higher probability of Leishmania transmission.