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The DOT-STRIP-ELISA was evaluated in the laboratory as a serodiagnostic tool for Schistosoma haematobium infection in order to assess the potential of introducing the technique under field conditions in the developing world. Out of 100 individuals with parasitologically confirmed Schistosoma haematobium, 87 reacted positively (sensitivity 87%), whereas 45 out of 50 sera from individuals from a non-endemic area reacted negatively (specificity 90%). Results were reproducible. Cross-reactions were observed with sera from individuals infected with Schistosoma mansoni, Echinococcus, Leishmania and Wuchereria. The DOT-STRIP-ELISA offers more advantages with regard to practicability and test-time when compared with the DOT-DISC-ELISA and DOT-MILLIPORE-ELISA.

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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.

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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.

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The relationship between splenomegaly and visceral leishmaniasis (VL) was investigated during a cross-sectional study in 2,941 individuals in Baringo District, Kenya, where both malaria and VL are endemic. Spleen size was correlated with presence of malaria parasites in thick blood films and with evidence of present or past Leishmania donovani infection as determined by serology and history. Marked splenomegaly (Hackett grade 3 or greater) significantly correlated with present or previous leishmanial infection (chi 2 = 53.5; p < 0.001) whereas moderate splenomegaly (Hackett grade 1 or 2) significantly correlated with malaria parasitaemia (chi 2 = 73.03; p < 0.001). The presence of antimalarial antibodies did not contribute to the differentiation of the cause of splenomegaly. The diagnostic significance of splenomegaly in this population is discussed.

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A 12-month field study on sandflies was conducted from April 1992 to March 1993 at three locations in Baringo District, Rift Valley Province, Kenya. Study sites were selected based on their close proximity to the households of three patients who had had parasitologically confirmed visceral leishmaniasis in 1988, 1990 or 1991. Sandfly populations were highest during the two rainy seasons, April-June and November-December. A significant association was detected between the monthly abundance of sandflies and rainfall in the previous month. A significantly higher proportion of females than males was collected in light traps than on sticky paper traps set in termite mounds or animal burrows: approximately twice as many males as females were collected from the sticky paper traps whereas twice as many females as males were collected in light traps. Over 10% of the female sandflies collected from animal burrows and termite mounds were gravid, indicating that these flies were seeking oviposition sites at these locations. A total of 2231 sandflies was collected and five females were found to have flagellates in their midguts. The flagellates cultured from four Sergentomyia spp. were tentatively identified as Crithidia sp. by cellulose acetate electrophoresis (CAE). The promastigotes from the one Phlebotomus martini female found with an infected midgut were identified as Leishmania donovani by CAE.(ABSTRACT TRUNCATED AT 250 WORDS)

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The T cell response to different Leishmania donovani antigens was investigated using peripheral blood mononuclear cells (PBMC) from Kenyans cured of visceral leishmaniasis and non-exposed Danes. Crude promastigote and amastigote antigens both induced proliferation and interferon-gamma (IFN-gamma) production in PBMC from cured patients, while cells from non-exposed donors gave weak responses. A similar pattern was induced by lipophosphoglycan-associated protein (LPGAP). By contrast, the major surface protease of Leishmania, gp63, induced only a weak proliferative response without IFN-gamma production in five of 17 samples from cured patients. Four of the five responding cultures produced IL-4, i.e. the response to this antigen was of the Th2 type. Furthermore, sera from acutely ill visceral leishmaniasis patients contained high levels of IgG antibodies to gp63. The Th2-like response to gp63 in patients cured of visceral leishmaniasis differs from the Th1-like response to the same antigen observed in patients cured of cutaneous leishmaniasis.

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The leishmanin skin test (LST) was applied in 26 clusters of an average of 97 individuals in Baringo District, Kenya. These clusters were centered around recent cases of visceral leishmaniasis (VL). Of 2,411 individuals tested, 254 (10.5%, 155 males and 99 females) had a positive reaction. Among cured VL patients, the frequency was approximately 30% and no sex difference was observed. In the population as a whole, LST positivity increased with age to a stable level from approximately 15 years of age, reflecting an endemic situation. The level of LST positivity was 25-30% and 10-15% in males and females, respectively. Uninfected household contacts of VL cases had a higher frequency of LST reactivity than the rest of the population. This relationship was significant only in females and children, the prevalence ratio being 2.3 (95% confidence interval 1.3-4.1), 1.9 (1.1-3.5), and 1.4 (0.8-2.5) for females, children, and males, respectively. The frequency of LST positivity was higher individuals living in wood houses than in individuals living in house with mud or stone walls. Again, this difference was significant only in females and children (P = 0.02 and P = 0.04), but not in males (P = 0.7). The results suggest that children and women are exposed to the parasite in or around their houses, whereas adult males are, in addition, exposed elsewhere.

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Visceral leishmaniasis (VL), caused by Leishmania donovani, is endemic in Baringo District, Kenya. The disease has a focal distribution in the dry, hot areas below 1500 metres. Infections may be characterized as follows: 1) asymptomatic, 2) subclinical and self-limiting (not medically identifiable), and 3) clinically manifest disease (that is medically identifiable). Half of the reported VL patients are between 5 and 14 years of age and 66% of them are males. The reasons for the focal distribution and for the age and sex preference are discussed. Phlebotomus martini is the vector of the parasite, and man is the only known reservoir. Cutaneous leishmaniasis (CL), due to Leishmania major, is rare in humans, but underreporting is likely. The vector, Phlebotomus duboscqui, is mainly found in animal burrows where it feeds on rodents which are frequently infected. A human case of a mixed L. donovani and L. major infected. A human case of a mixed L. donovani and L. major infection has been reported in this dual focus of VL and CL.

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A Schistosoma haematobium adult worm cDNA library was screened with sera from demonstrably immune baboons (mean worm reduction 94%) vaccinated with highly-irradiated cercariae (VBabS) and also with sera from adult S. haematobium-infected humans (HIS Sh). As species-specificity is a characteristic feature of the immunity induced by irradiated cercariae, S. haematobium species-specific clones were identified by rescreening positives with sera from S. mansoni-vaccinated animals or infected humans. Six species-specific clones, 3 initially detected with vaccinated baboon sera (D11, D14 and D26) and 3 with human infection sera (E1, E2 and E16) were further characterized by Western blotting. The three HIS-selected clones did not react significantly with VBabS or acutely-infected baboon sera (ABabS) while D11, D14 and D26 showed increasing reactivity with successive vaccinations. In addition D11 and D14 but not D26 responded to ABabS. When tested against HIS Sh from 24 patients of varying ages, D11 and D26 reacted most frequently with sera from individuals in the older age groups (> 17 yrs). A species cross reactive clone, D12, which was used as a positive control throughout, was found to react with all schistosome specific sera tested.

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In a cross-sectional house-to-house study in a leishmaniasis-endemic area in Kenya, the cellular and humoral immune response to Leishmania lipophosphoglycan (LPG) was determined. Clinical data, peripheral blood mononuclear cells, and plasma were obtained from 50 individuals over the age of eight years. Lymphoproliferation and interferon-gamma (IFN-gamma) production by these cells were examined. It was shown that cells from all six individuals in the population with a history of kala-azar responded to LPG in the lymphocyte proliferation assay, and four of these six responded in the IFN-gamma assay. In contrast, cells from 12 of 44 individuals from the study area with no history of kala-azar and none of the five Danish control samples responded to LPG. Antibodies against LPG were detected by enzyme-linked immunosorbent assay in 45 of 50 plasma samples. Our findings clearly show that mononuclear cells from kala-azar patients cured of infection were able to respond to the LPG preparation. The finding of a specific cellular immune response to LPG in 12 of 44 individuals with no history of kala-azar is consistent with previous epidemiologic studies, in which it has been shown that a proportion of L. donovani infections run a subclinical course. The high frequency of individuals with antibodies against LPG might indicate that a majority of the population had been exposed to the parasite.(ABSTRACT TRUNCATED AT 250 WORDS)

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