Serodiagnosis of visceral leishmaniasis in an endemic area of the Sudan

Abstract

The value of serology in the diagnosis of visceral leishmaniasis in the endemic area of central Sudan was assessed by comparing the reactions of sera from patients and apparently normal people by the immunofluorescence (IF), immunodiffusion (ID) and counter-immunoelectro-phoresis (CIE) tests. The sera came from 50 parasitologically-positive cases of visceral leishmaniasis, from 150 apparently normal individuals in a known focus of the disease and 300 blood donors from the general population of the area. In the IF test serial doubling dilutions of sera were tested by the indirect antibody technique against promastigote slide antigen. In the ID and CIE tests undiluted sera were used against concentrated soluble leishmanial antigen. All 50 sera from the patients were positive in the IF test, 34% at 1: 200 dilution and 66% at 1: 400 to 1: 6400 dilutions. Positive results were obtained in some of the normal sera: 3·3% of the 300 blood donors’ sera, at dilution 1: 100, and 25 (16·6%) of the 150 sera from the disease focus, 24 at 1: 100 and one at 1: 200.

It was concluded that an IF titre of at least 1: 400 would be diagnostic of visceral leishmaniasis. In the ID and CIE tests 72% of the sera from the patients gave positive results. Some of the normal sera (9·3% of the 150 and 1·3% of the 300 sera) were also positive by the ID and/or CIE, so that it was also concluded that ID positives and CIE positives, as with an IF titre of 1: 200, would only be suggestive of the presence of clinical infection.