G. Gachihi

Visceral leishmaniasis unresponsive to antimonial drugs II. Response to high dosage sodium stibogluconate or prolonged treatment with pentamidine

Ten Kenyan patients with visceral leishmaniasis unresponsive to sodium stibogluconate, at a dose of 16 to 20 mg Sb/kg body-weight/day given for 30 to 98 days, were treated with 20 mg Sb/kg bw given every eight hours. This regimen was modified or abandoned in six patients because of suspected toxicity, although toxicity was difficult to assess because of intercurrent illness. Toxic effects included lethargy, anorexia, vomiting, electrocardiographic changes, fall in haemoglobin and rise in liver enzymes. One patient died, probably from a cardiac arrhythmia. Two patients were cured, four responded partially and four showed no response. Pentamidine, at a dose of 4 mg/kg body-weight given one to 3 times per week for 5 to 39 weeks, was given as initial treatment in one patient and after failure of sodium stibogluconate in seven. Toxic effects included nephritis, hepatitis, transient diabetes and subcutaneous abscesses. Two patients were cured, two responded partially, three showed no response and one, after apparent cure, relapsed and was unresponsive to additional pentamidine treatment. Low-frequency, long-duration pentamidine was often useful in maintaining any improvement made during treatment with the less well tolerated high-dose, high frequency sodium stibogluconate. We observed the step-wise development of resistance to both sodium stibogluconate and pentamidine. The problems of managing patients with visceral leishmaniasis which is unresponsive to conventional doses of pentavalent antimonials are discussed and some tentative suggestions put forward.

Visceral leishmaniasis unresponsive to antimonial drugs I. Clinical and immunological studies

Ten Kenyan patients with visceral leishmaniasis, unresponsive to sodium stibogluconate at a dose of 16 to 20 mg Sb/kg/day given for 30 to 98 days, have been studied clinically and immunologically and compared with 57 antimony-responsive patients. Pulmonary tuberculosis and previous treatment with antimonial drugs were the only factors which were more common in unresponsive patients. The degree of immunosuppression and rate of recovery of immunoreactivity did not differ between antimony-responsive and -unresponsive patients. Only one patient had never been treated before (primary unresponsiveness). In the other nine patients secondary unresponsiveness occurred after one or more treatment courses, suggesting that the parasite developed resistance to antimony. Antimony-unresponsiveness in visceral leishmaniasis is a serious problem numerically, clinically and economically. A plea is made that the initial treatment of visceral leishmaniasis should be adequate in dose and duration.

A prospective sero-epidemiological study of visceral leishmaniasis in Baringo district, Rift Valley Province, Kenya

The incidence of visceral leishmaniasis (VL) was studied in 30 clusters with an average of 98 individuals in each cluster in a defined, endemic rural area of Baringo District, Kenya. The clusters were centred around recent cases of VL. Anti-leishmanial antibodies were measured by the direct agglutination test (DAT) and a clinical examination was performed on 2 occasions between April 1991 and May 1993. Of 2934 individuals tested by the DAT during the first visit, 78 (2.7%) were seropositive, 54 with and 24 without a history of VL. The seroconversion rate was 9/1000 person-years of observation (95% confidence interval 5.1-12.92) among 2332 seronegative individuals retested the following year. During the entire study period, VL was diagnosed in 10 patients, with an incidence rate of 2.2/1000 person-years of observation (95% confidence interval 0.8-3.6). Household contacts of individuals with previously confirmed VL had a higher frequency of DAT positivity than the rest of the population. This difference was significant for both sexes. These results suggest transmission in and around houses.

Visceral leishmaniasis: use of the polymerase chain reaction in an epidemiological study in Baringo District, Kenya

The polymerase chain reaction was applied to capillary blood spots dried on filter paper from 20 parasitologically proved cases of visceral leishmaniasis (VL), 21 subclinical cases, and 11 healthy controls in a longitudinal study of anthroponotic VL in Baringo District, Kenya. Leishmania deoxyribonucleic acid (DNA) was detected 10.5 months before diagnosis and up to 3 years after diagnosis and apparently successful treatment. Subclinical cases can have detectable circulating parasite DNA in their blood. These findings may indicate that subclinical cases can be a reservoir and formerly treated VL patients can remain a reservoir for a long time. Xenodiagnosis should be performed on subclinical cases and former VL patients to establish their role in transmission of VL in Kenya.

Cutaneous leishmaniasis caused by Leishmania major in Baringo District, Kenya

Leishmania major was isolated from lesions of a patient suffering from cutaneous leishmaniasis in Baringo District of Kenya. Isoenzyme mobilities of this strain were compared with those of L. major, L. donovani, L. aethiopica and L. tropica reference strains and also L. major from a sand fly, Phlebotomus duboscqi, and a rodent, Arvicanthis niloticus, trapped in the same region. The patients isolate had similar banding patterns to the L. major reference strain and also the rodent and the sand fly strains with the 9 enzymes examined. This is the first report in Kenya of an indigenous case with naturally acquired zoonotic cutaneous leishmaniasis.

Acute phase protein concentrations predict parasite clearance rate during therapy for visceral leishmaniasis

Visceral leishmaniasis (VL) remains a major health problem in Kenya and other parts of Africa, Central America and Asia. Currently, splenic aspirate smear and culture are the standard methods of monitoring therapy and relapse. Acute phase reactant markers, C-reactive protein (CRP), serum amyloid A protein (SAA) and alpha 1-acid glycoprotein (AGP) were evaluated as less invasive techniques for monitoring therapy in 59 patients with VL before, during and after therapy. CRP, SAA and AGP were elevated in VL patients at admission and the concentrations decreased with effective therapy to reach normal levels by the end of therapy (SAA and AGP) or by 3 months follow-up (CRP). Two groups of patients were selected on the basis of rate of parasite clearance. The acute phase protein concentrations were significantly raised in those slower to clear parasites. Analysis of sensitivity and specificity of acute phase proteins as predictors of parasite clearance suggested that they might represent useful non-invasive markers for monitoring disease activity, response to therapy and relapse in VL.

Eosinophilia and eosinophil helminthotoxicity in patients treated for Schistosoma mansoni infections

The changes in eosinophil levels and in eosinophil-mediated antibody-dependent schistosomular cytotoxicity, following treatment for Schistosoma mansoni infections, have been investigated in 2 similar groups of patients aged 15-50 years. Patients in group 1 were treated with either hycanthone or oxamniquine, and those in group 2 with hycanthone or praziquantel. Eosinophil levels were significantly increased in both groups. In group 1 peripheral blood eosinophil counts rose from a mean of 175/microliters before treatment to 745/microliters 3 weeks after treatment, and in group 2 from 181/microliters to 1066/microliters. The increase in eosinophil levels was positively correlated with a rise in circulating anti-adult worm antibodies (r = -0.587, P less than 0.05), whereas a negative correlation was recorded with anti-egg antibodies (r = -0.727). Despite some enhanced eosinophil helminthotoxicity following treatment in some of the individuals in group 1 (7/15), the change overall was not significant. In group 2, in which a different standard anti-schistosomular antibody was used, the eosinophil killing capacity recorded at 3 weeks was lower than that before commencement of treatment (t = 2.89, P less than 0.01). The eosinophil stimulating activity, detected in cultured mononuclear cell supernatants (MCS) from individual patients, correlated with eosinophil levels (r = 0.582, P less than 0.02) but there was no association with eosinophil killing. MCS activity did not appear to be boosted by treatment. These studies showed that peripheral blood eosinophil counts were increased following treatment, but their ability to kill schistosome larvae is variable and may depend on the immune serum used as the source of anti-schistosomular antibody.

Safety and immunogenicity of a Plasmodium falciparum sporozoite vaccine: boosting of antibody response in a population with prior natural exposure to malaria

Recombinant sporozoite vaccine or placebo were administered once to 25 volunteers from an area endemic for malaria. Antibody to R32tet32 rose in 9 of 15 receiving vaccine and remained elevated in 6 for 6 months. Mean absorbance increase was 0.43 +/- 0.40 with vaccine, 0.01 +/- 0.23 with placebo, and 0.72 +/- 0.19 in responders. Six non-responders had significantly lower pre-immunization levels (0.07 +/- 0.05) than responders (0.39 +/- 0.25). There was an association between an increase in immunofluorescence (n = 4) and an increase in absorbance (n = 9) among vaccine recipients (n = 15). Vaccine-induced increase in antibody to natural circumsporozoite antigen was indicated by increases in immunofluorescence and by increases in circumsporozoite precipitation score in 2 of the 5 responders with highest antibody increase measured by enzyme-linked immunosorbent assay. Response to subunit sporozoite vaccine paralleled response to prior natural sporozoite exposure and was significant and prolonged in a population with prior natural exposure to malaria.

Interferon-γ and interleukin-4 production by human T cells recognizing Leishmania donovani antigens separated by SDS-PAGE

Crude preparations of Leishmania donovani proteins were separated by preparative SDS‐polyacryl‐amide gel electrophoresis. Fractions of separated proteins were recovered by electroelution directly from the gel into separate chambers. The isolated protein fractions were tested for induction of proliferation and interferon‐γ (IFN‐γ) production in cultures of peripheral blood mononuclear cells (PBMC) from individuals who had recovered from visceral leishmaniasis caused by L. donovani. The release of interleukin‐4 (IL‐4) by PBMC stimulated with the isolated L. donovani antigen fractions was measured after treatment with phorbol‐myristate‐acetate and ionomycin. The cells proliferated in response to all protein fractions with molecular weights in the range <12 kDa to 85 kDa. In general, IFN‐γ was secreted in response to stimulation with all the protein fractions, whereas IL‐4 production was infrequently observed. The results show that T cells from individuals who have been cured of visceral leishmaniasis recognize and respond to a wide range of leishmanial antigens. There was no evidence of particular fractions constantly giving either IFN‐γ‐ or IL‐4‐producing responses.

A new focus of kala-azar due to Leishmania donovani sensu lato in Kenya

Three Masai children from Kekonyokie South Location, Kajiado District were diagnosed with visceral leishmaniasis (kala-azar). Leishmanial isolates from the patients were characterized as Leishmania donovani sensu lato, by cellulose acetate electrophoresis. Case histories indicated that the disease was acquired locally. A survey of 409 children at 7 local primary schools and one nursery school revealed no additional case. Sandfly surveys using light traps and sticky paper traps recovered 10 species of sandfly, including 2 Phlebotomus species. P. martini was prevalent throughout the area. P. orientalis was only rarely encountered, but it was the first collection record of this species in the southern portion of the Rift Valley in Kenya. Although no Leishmania-infected sandfly was found, P. martini is probably the vector of kala-azar in the location, as it is elsewhere in Kenya.