Visceral leishmaniasis in Somalia. Significance of IgG subclasses and of IgE response.

We have determined the levels of IgG subclasses and IgE as well as specific antibodies of these isotypes in sera from 22 patients with clinical visceral leishmaniasis (VL) from Somalia. The results are compared with those obtained from 30 Somali and 23 Swedish controls. We found markedly increased concentrations of IgG1 in the VL sera, indicating that the pronounced increase in IgG in VL which is generally considered to be due to polyclonal B-cell activation is mainly restricted to this subclass. The IgG2 concentrations were significantly decreased. The IgG3 and IgG4 concentrations, on the other hand, did not differ between the two groups of Somali sera. The Somali control sera contained higher concentrations of IgG1 and IgG3, but significantly lower concentrations of IgG2 as compared to Swedish controls. The IgG4 values, on the other hand, were not different between the two groups of control sera. Anti-leishmania antibodies belonging to all IgG subclasses, were found in the patients' sera. There was no significant difference in total IgE between sera from VL patients and controls and specific IgE antibodies were only detected in a few patients. The Western blot assay (WB), revealed the presence of two bands corresponding to 74 kDa and 88 kDa in all patients' sera, indicating a possible diagnostic role for WB in this particular population.

Visceral leishmaniasis in Somalia: prevalence of markers of infection and disease manifestations in a village in an endemic area.

Prevalence and disease manifestations of visceral leishmaniasis (VL) were studied in a Somali village in an area which has long been known to be endemic for VL. Demographic data were collected from 102 households, comprising 438 inhabitants. Clinical examination was performed of 306 individuals, 72% of the 426 eligible persons. Of these, 276 (90%) agreed to give blood and 246 (80%) to be skin tested with leishmanin. Leishmanin reactions were positive; in 26% anti-Leishmania antibodies were detected in 11%, and splenomegaly was recorded in 14% (23% of those who were seropositive). Malaria was hypoendemic and therefore unlikely to be responsible for more than 10% of the cases with splenomegaly. Three of the seropositive villagers with splenomegaly complained of feeling ill. The remaining 91 sero- and/or leishmanin-positive individuals had no complaint regarding their health and had not experienced any long period of illness. There was a slight over-representation of males in the group of sero- and/or leishmanin-positive villagers, possibly due to a gender-associated difference in exposure to the parasite. Among the patients with clinical VL treated at Mogadishu hospitals during 1989 and 1990, the male/female ratio was 3.3:1, which may indicate a selection of male patients for hospital care. Most patients were < or = 15 years old, suggesting that the highest risk of becoming clinically ill was among children.

Visceral leishmaniasis in Somalia: prevalence of leishmanin-positive and seropositive inhabitants in an endemic area.

In an endemic area of Somalia both humoral and cell mediated immunity against Leishmania donovani was demonstrated in 246 inhabitants. In a study of 14 patients with active visceral leishmaniasis, we found that antibodies appear early in infection and that they are then demonstrable for a limited period only. Leishmanin positivity develops later and persists longer, but does not seem to be lifelong. The majority of the immunoreactive individuals were either sero- or leishmanin positive. This finding is in accord with the result obtained in recent experimental studies indicating a regulatory effect exerted on humoral and cell mediated immunity by different T lymphocyte subsets.

Visceral leishmaniasis in Somalia. Circulating antibodies as measured by DAT, immunofluorescence and ELISA.

Sera from patients with visceral leishmaniasis (VL) (n = 26), healthy residents of Mogadishu (n = 157), inhabitants of a village in an endemic area (n = 276) and healthy Swedes (n = 60) were examined using the direct agglutination test (DAT), immunofluorescence (IF) and ELISA for antibodies against Leishmania donovani. The study was carried out in order to provide baseline data for antibody responses in visceral leishmaniasis as existing in Somalia and to explore which one of these methods would be most suitable for diagnosis of clinical cases as well as for epidemiological population studies in Somalia. All patients had high levels of circulating antibodies, however, lower values were recorded in the early stages of the disease. High reactivity in ELISA was seen first after one year. All three tests distinguished well between sera from VL patients and healthy controls. Approximately 10% of the sera from villagers were reactive above the cut-off levels in the three tests. DAT is the simplest to perform and does not require much equipment. ELISA can be made simple and economic if performed in one serum dilution and read visually. IF requires more expensive and specialized equipment and is not suitable for large scale examination of sera. A complete evaluation of the three tests should also include the analysis of sera from various stages and manifestations of the disease.

Reference ranges for IgG, IgM and IgA in the serum of urban and rural Somalis.

In order to provide baseline data for an immuno-parasitological laboratory in Somalia, serum concentrations of IgG, IgM and IgA were determined in some key populations: healthy residents of Mogadishu (n = 157), inhabitants of the village of Daimo Samo (n = 276) and patients with malaria (n = 39) and visceral leishmaniasis (n = 26), both protozoan infections accompanied by hypergammaglobulinaemia and causing severe health problems in Somalia. Since the serum immunoglobulin concentrations in the Somali populations studied were not normally distributed, they were evaluated using medians and percentiles. Significantly higher values of IgG, IgM and IgA were demonstrated in healthy Mogadishu residents as compared to healthy Swedes. Daimo Samo villagers had significantly higher IgG and IgM values than healthy Mogadishu residents. Very high concentrations of IgG and IgM were demonstrated in sera from patients with visceral leishmaniasis. Somali patients with malaria also had marked hypergammaglobulinaemia, however, only in the IgG class. The high levels of IgG, IgM and IgA demonstrated in sera from Somalis, indicate the need for establishing local reference values and should be considered when introducing serological tests in tropical countries. Such methods are usually adopted to conditions in industrialized countries, where immunoglobulin contents of sera are lower.