Mapping the potential distribution of Phlebotomus martini and P. orientalis (Diptera: Psychodidae), vectors of kala-azar in East Africa by use of geographic information systems.

The distribution of two principal vectors of kala-azar in East Africa, Phlebotomus martini and Phlebotomus orientalis were analysed using geographic information system (GIS) based on (1) earth observing satellite sensor data: Normalized Difference Vegetation Index (NDVI) and midday Land Surface Temperature (LST) derived from advanced very high resolution radiometer (AVHRR) of the global land 1km project of United States Geological Survey (USGS), (2) agroclimatic data from the FAO Crop Production System Zone (CPSZ) of the Intergovernmental Authority on Development (IGAD) sub-region, and (3) the FAO 1998 soils digital map for the IGAD sub-region. The aim was to produce a predictive risk model for the two vectors. Data used for the analysis were based on presence and absence of the two species from previous survey collections in the region (mainly Ethiopia, Kenya and Somalia). Annual, wet season and dry season models were constructed. Although all models resulted in more than 85% positive predictive values for both species, the best fit for the distribution of P. martini was the dry season composite (NDVI 0.07-0.38 and LST 22-33 degrees C) with a predictive value of 93.8%, and the best fit for P. orientalis was the wet season composite (NDVI -0.01 to 0.34 and LST 23-34 degrees C) with a predictive value of 96.3%. The two seasonal composites models derived from satellite data were largely similar with best fit models developed based on the CPSZ climate data: average altitude (12-1900m), average annual mean temperature (15-30 degrees C), annual rainfall (274-1212mm), average annual potential evapotranspiration (1264-1938mm) and readily available soil moisture (62-113mm) for P. martini; and average altitude (200-2200m), annual rainfall (180-1050mm), annual mean temperature (16-36 degrees C) and readily available soil moisture (67-108mm) for P. orientalis. Logistic regression analysis indicated LST dry season composite of the satellite data, average altitude, mean annual temperature and readily available soil moisture of the CPSZ data as the best ecological determinants for P. martini while LST annual composite was the only important ecological determinant for P. orientalis. Spearman's rank correlation revealed several factors to be important determinants for the distribution of the two vectors. None of the soil types analysed appeared to be important determinant for the two species in East Africa, unlike in Sudan where P. orientalis is mainly associated with eutric vertisol (black cotton clay soil).

Alteration of Fas and Fas ligand expression during human visceral leishmaniasis.

Several studies in murine systems have suggested a role of apoptosis in the pathogenesis of leishmaniasis. However, the role of apoptosis in visceral leishmaniasis in man has not been explored. In this study, we show that patients with visceral leishmaniasis demonstrate significant dysregulation of Fas and Fas ligand. Levels of soluble Fas (sFas) and soluble Fas ligand (sFasL) were elevated in plasma of patients with active visceral leishmaniasis (VL) and individuals co-infected with VL-HIV-1 compared to healthy controls. The levels of sFas and sFasL were normalized 6 months after successful treatment. In VL patients, the expression of membrane bound Fas, and to a lower extent FasL, were up-regulated on Leishmania donovani-infected spleen cells, the site of parasite multiplication. Expression of Fas and FasL on peripheral blood mononuclear cells was within normal range, probably reflecting that the blood is not a normal site of L. donovani infection. Furthermore, this is suggested by the finding that in vitro infection of macrophages with L. donovani up-regulated Fas expression on the surface of infected cells and enhanced the levels of sFasL in supernatants from infected cultures. How this dysregulation may affect the pathogenesis of human visceral leishmaniasis is discussed.

Sero-epidemiological assessment and diagnosis of visceral leishmaniasis in an endemic locality using Fast Agglutination Screening Test (FAST).

The Fast Agglutination Screening Test (FAST) was employed on sera obtained from an endemic area of visceral leishmaniasis in southwestern Ethiopia, in February 2000. The study involved (i) active case detection among 1575 residents of two villages; and (ii) passive case detection in an outpatient clinic. Sera of 1587 individuals, including 143 sera of previously treated VL patients, were tested. Based on the size of agglutination mat, the FAST results were read qualitatively as non-reactive (-), weakly reactive (1+), moderately reactive (2+) and highly reactive (3+). All FAST reactive sera were re-tested with the Direct Agglutination Test (DAT). After clinical screening of 1625 individuals, 61 individuals with signs and symptoms of early or late VL were found; 26 sera were FAST positive. Twenty-two of these suspected VL cases were subjected to parasitological examination using lymph node aspirates. Eighteen (81.8%) were confirmed either by demonstration of amastigotes in smears or promastigotes in NNN cultures. FAST reactive anti-leishmanial antibodies were detected in 4.5% of untreated and 70.6% of previously treated patients. Forty-five sera of 1390 previously untreated asymptomatic individuals (3.2%) were found to be FAST positive. This report demonstrates that FAST is a rapid and cost-effective screening test for the diagnosis and sero-epidemiological surveillance of visceral leishmaniasis.

The performance of direct agglutination tests (DAT) in the diagnosis of visceral leishmaniasis among Ethiopian patients with HIV co-infection.

The incidence of visceral leishmaniasis (VL) in Ethiopia has dramatically increased over the last 10 years, coinciding with the advent of the HIV epidemic. HIV co-infection in VL patients results in atypical, clinical and serological presentations, and may hamper serological diagnosis of VL. The performance of direct agglutination tests (DAT) in the diagnosis of VL in 103 Ethiopian patients with or without HIV infection was therefore investigated. The DAT results indicated that 96 of the patients had leishmanial infections, although amastigotes were only detected in samples from 91. Data on HIV status showed that 50.7% of all patients but 56.0% of the parasitologically confirmed cases of VL patients were HIV-positive. Based on the 95 patients who were each examined both by DAT and parasitological methods, the overall sensitivity of the DAT was 97.7%. Among the parasitologically confirmed cases of VL, a false-negative DAT result was obtained for two (3.9%) of the 51 cases who had HIV co-infection and for none of the 40 HIV-negative cases. In contrast to the observations made in Europe, DAT in Ethiopia therefore remain reasonably sensitive in the diagnosis of VL during HIV co-infection. The results are discussed in view of the possibility of distinctive antibody responses induced by Leishmania donovani donovani and L. d. infantum in HIV-infected patients.

Control of Schistosoma mansoni by the soapberry Endod (Phytolacca dodecandra) in Wollo, northeastern Ethiopia: post-intervention prevalence.

OBJECTIVES: To record the effect of Endod soap and spraying of soaked Endod suspension on the prevalence of human schistosomiasis. DESIGN: A cross-sectional epidemiological study in which pre- and post-intervention parasitological results were compared. SETTING: Kemise, Bati and Harbu towns in northeastern Ethiopia. SUBJECTS: The study subjects included all members of the five per cent households systematically selected from the three towns. RESULTS: In Kemise town, where suspension of ground Endod was sprayed on the stream containing infected snails, the prevalence of the disease was reduced from 59% to 53% and the mean intensity of infection was reduced from 239 eggs per gram (EPG) of faeces to 99 EPG (p < 0.05). In Bati town where Endod soap approach was used, the respective reduction in the prevalence and intensity of infection was from 51% to 43% and from 195 EPG to 162 EPG (p < 0.05). There was also a significant reduction of the disease in the control town probably due to the effects of praziquantel treatment and other factors. CONCLUSION: The reduction achieved in the prevalence and intensity of schistosomiasis after an intervention period of four years was limited. This observation corroborates the fact that molluscicides must always be considered as supplementary to chemotherapy in the control of schistosomiasis. Although both approaches can be used, the spraying approach appears to be simpler and more feasible because two or three times yearly application of Endod suspension would suppress snail population and reduce transmission. Nevertheless, the choice as to what approach to use must be made on the basis of community preference, and for some soap-effect of Endod would be attractive

Inter-current and nosocomial infections among visceral leishmaniasis patients in Ethiopia: an observational study.

From July 1989 up to September 1997, a total of 247 non-HIV associated visceral leishmaniasis (VL) patients were treated on outpatient basis in rural clinics (195 patients) and hospitalised in the Northern-Omo Regional Hospital (18 patients) and in Addis Ababa referral hospitals (34 patients). Patients treated in the rural clinics and in the Regional hospital originated from the same endemic area and had comparable baseline characteristics. Overall rates of complications (inter-current/concurrent infectious or non-infectious diseases or deaths) in the three categories were 10.7, 38.9 and 61.6%, while case fatality rates were 2.5, 5.6 and 11.7%, respectively. Nosocomial bacterial infections occurred in 16.6% of patients treated in the Regional hospital and 32.3% of patients treated in Addis Ababa referral hospitals, and these infections accounted for 42.8 and 52.4% of the complications seen in the respective categories. Among VL patients originating from the same endemic place and with comparable baseline clinical data, patients treated hospitalised had significantly higher rates of complications than patients treated on outpatient basis (P<0.001). Patients who had complications during the course of VL therapy had significantly lower pre-treatment haemoglobin levels. Considering the extra cost of hospitalisation and risk of nosocomial infections and petavalent antimonial therapy being fairly safe, we recommend that VL patients, unless with serious complications, should preferably be treated on ambulatory basis with follow-up to monitor response and inter-current infections if any.

Distinct immunity in patients with visceral leishmaniasis from that in subclinically infected and drug-cured people: implications for the mechanism underlying drug cure.

Significant levels of IgG3 and IgG4 and high levels of IgG1 leishmania-specific antibody differentiated the immune states in 10 patients with visceral leishmaniasis from those of virtually all 20 drug-cured and 18 subclinically infected subjects, whereas the level of IgG2 antibody was nondiscriminating. The most extreme "subclinically infected" outlier subsequently developed disease. Overall, the immune states in subclinically infected and drug-cured persons were mutually indistinguishable but were readily distinguished from those of patients. These findings may have implications for the immunologic mechanism underlying drug cure in visceral leishmaniasis.

Emerging Leishmania/HIV co-infection in Africa.

The HIV/AIDS pandemic is spreading at an alarmingly high rate in Africa. Leishmaniasis is also highly prevalent in the continent. Despite the emergence of Leishmania/HIV co-infection in Africa, the numbers reported are disproportionately low. Moreover, the number of cases of co-infection is expected to rise in Africa owing to the simultaneous spread of the two infectious diseases and their increasingly overlapping geographical distribution.

Electrocardiographic findings in Ethiopians on pentavalent antimony therapy for visceral leishmaniasis.

BACKGROUND: The old short course regimens of pentavalent antimonial (sb(v)) therapy of visceral leishmaniasis (VL) have largely been abandoned worldwide as they are associated with increasing problems of relapse and unresponsiveness. In Ethiopia, some hospitals still use the old interrupted and short course regimen partly because of fear of drug toxicity. OBJECTIVE: To evaluate the safety of the WHO recommended uninterrupted therapy at a dose of 20 mg sb(v)/kg for up to thirty days. DESIGN: A prospective study. SETTING: Patients were recruited from Addis Ababa hospitals and from Konso VL endemic area in southern Ethiopia. SUBJECTS: Forty nine patients who included, ten HIV-positive and 39 HIV-negative, were enrolled for the study. RESULTS: Twenty three HIV-negative patients got treatment for 20 days and the rest, 16 HIV-negative and 10 HIV-positive, were treated for 28 to 30 days. Among HIV-seronegatives, the mean QT interval corrected for heart rate (QTc) at the end of therapy in patients treated for 20 days and 28-30 days was comparable (0.419 +/- 0.031 seconds versus 0.424 +/- 0.027 seconds, respectively). Among patients treated for 28-30 days, the mean QTc in HIV co-infected patients was comparable to that of HIV-negatives (0.416 +/- 0.018 seconds versus 0.424 +/- 0.027). Comparable rates of new ECG changes involving the T waves were observed in two HIV-positive (20%) and two HIV-negative (12.5%) patients treated for 28-30 days, and in seven (30.4%) HIV-negative patients treated for 20 days. Overall, only two (4.1%) patients (all HIV-negative males) had QTc interval > or = 0.50 seconds at the end of therapy. In one patient, the prolonged QTc was noted on the twentieth day with bradycardia of 44/minute. CONCLUSIONS: In Ethiopian VL patients with normal renal function, sb(v) therapy at a daily dose of 20 mg/kg for up to 30 days is safe and only rarely associated with clinically significant bradycardia which resolves after temporary cessation of therapy. Furthermore, in areas with limited facilities, monitoring the pulse rate during antimonial therapy may help detect impending cardiotoxicity.

HIV-1 alters T helper cytokines, interleukin-12 and interleukin-18 responses to the protozoan parasite Leishmania donovani.

OBJECTIVE: To investigate the in vitro and in vivo effect of HIV-1 on lymphoproliferative and T helper (Th) cytokine responses in leishmaniasis. METHODS: Th1 [interleukin (IL)-2 and interferon (IFN)-gamma] and Th2 (IL-4 and IL-10) as well as IFN-gamma-inducing cytokines (IL-12 and IL-18) were measured in antigen and mitogen-stimulated culture supernatants of peripheral blood mononuclear cells (PBMC) of healthy donors, HIV-infected and visceral leishmaniasis (VL) patients with or without HIV co-infection. RESULTS: Proliferative responses to phytohaemagglutinin (PHA) were significantly lower in PBMC from VL and asymptomatic HIV-infected persons compared with responses in healthy individuals. VL-HIV co-infected patients showed the lowest responses. Although there was no significant difference in the Leishmania-induced proliferative responses among the healthy group and those infected with HIV only, VL patients (with or without HIV) exhibited very low proliferation. When cultured with PHA or Leishmania, PBMC from healthy donors produced high levels of a Th1 cytokine (IFN-gamma) and low levels of Th2 cytokines (IL-4 and IL-10). In addition, co-culturing PBMC from healthy donors with a killed HIV preparation abrogated the production of IFN-gamma induced by Leishmania and augmented IL-4 and IL-10 production. Cells from HIV-infected patients produced low levels of IFN-gamma, but high levels of IL-10. The addition of anti-IL-10 did not increase Leishmania-induced proliferative responses or IFN-gamma production. Both IL-12 and/or IL-18 responses were lower in VL patients, HIV-infected, or VL-HIV co-infected patients as compared with those of healthy donors. CONCLUSION: The data suggest that the inhibitory effect of HIV and VL on proliferation and IFN-gamma production is not due to IL-10 alone, but that the defect induced by HIV and VL probably operates at the level of regulation of IFN-gamma-inducing factors, such as IL-12 and IL-18.

HIV viral load and response to antileishmanial chemotherapy in co-infected patients.

OBJECTIVE: To investigate whether clearance of Leishmania parasites from tissue aspirate smears in patients with HIV and visceral leishmaniasis (VL) co-infection treated with pentavalent antimonials is influenced by initial HIV viral load and to assess the effect of active VL on HIV viral load and replication in vivo. METHODS: Leishmania parasites were identified in Giemsa-stained smears prepared from tissue aspirates. Parasite index was determined by quantifying Leishmania donovani bodies in smears. HIV-1 RNA was quantitated by using the nucleic acid sequence-based amplification technique with a limit of detection of 500 copies/ml. All patients were treated with pentavalent antimonials at 20 mg pentavalent antimony (Sb(V))/kg daily for a total of 28 days. None of the patients received specific anti-retroviral therapy. RESULTS: Seventeen patients (73.9%) showed good initial response to anti-leishmanial treatment and the remaining six (26.1%) had very poor response. Among the good responders, 11 (64.7%) had no demonstrable Leishmania donovani bodies in post-therapy tissue aspirate smear preparations, and in the remaining six (35.3%) their parasite loads were reduced to very low levels. Patients with poor response had persistently high parasite index despite completion of anti-leishmanial chemotherapy. Poor responders had pre-treatment median HIV viral load that was >160-fold higher than responders to anti-leishmanial chemotherapy; [410000 copies/ml (quartile range, 33000-530000) and 2500 copies/ml (quartile range 500-297500), respectively]. Furthermore, compared with pre-treatment viral concentrations, patients with good response showed marked reduction in post-treatment viral load. In contrast, post-treatment HIV viral concentrations were markedly increased among patients with poor response to anti-leishmanial therapy. CONCLUSIONS: The results suggest that pre-treatment HIV viral load influences response to anti-leishmanial chemotherapy and active VL is associated with increased viral replication in vivo, supporting the notion that dual infection plays an important role in the pathogenesis and disease progression of either infection.

Leishmania-HIV interaction: immunopathogenic mechanisms.

Both Leishmania and the human immunodeficiency virus (HIV) can infect and multiply in macrophages, and both can dysregulate the immune system. Recent studies indicate that Leishmania can induce the activation of HIV in latently infected monocytic and T cells. Moreover, HIV can enhance intracellular growth of Leishmania in macrophages. Here, Dawit Wolday and colleagues examine the mechanisms that might be involved in the immunopathogenesis of Leishmania- HIV co-infection.

Praziquantel side effects and efficacy related to Schistosoma mansoni egg loads and morbidity in primary school children in north-east Ethiopia.

A total of 611 Schistosoma mansoni infected primary school children from three schools in north-east Ethiopia were treated with praziquantel at 40 mg/kg body weight in a single dose. Pre-treatment, 40.4% had no presenting symptoms and 30-40% had nausea, abdominal cramps and/or bloody-mucoid diarrhoea. None of the pre-treatment symptoms was related to nutritional status, intensity of S. mansoni egg excretion, or to the presence of other concomitant intestinal parasitic infections. During the first 4-6 h post-treatment observation period, 90 (14.7%) children self-presented with severe gastro-intestinal symptoms. Children who self-presented with severe symptoms had a higher mean age and mean S. mansoni egg excretion compared with children who did not self-present. The following day a total of 529 (86.6%) children, including all who self-presented during the first 4-6 h post-treatment, reported for clinical check-up and were subjected to a structured questionnaire interview on symptoms they had experienced over the time lapse following treatment. Among these, 91.5% reported one or more treatment related symptoms which were at times severe. Abdominal cramps (86.9%), diarrhoea with blood and/or mucus (49.5%), dizziness (31.2%) and vomiting (24.9%) were the most common treatment related symptoms. Skin rash with oedema were observed in four cases. Among treatment related symptoms, the combination of abdominal cramps with vomiting, bloody diarrhoea, vomiting alone and general weakness were significantly higher among the malnourished. A proportion of these symptoms increased with increasing categories of S. mansoni egg excretion before and after adjusting for nutritional status and concurrent intestinal parasitic infections. Overall, the cure rate of praziquantel, among 541 children who had stool examination 5 weeks after treatment was 83.2% and this rate decreased with increasing pre-treatment egg counts. In conclusion, most of the treatment related symptoms were mild. However, some of the objective symptoms were at times severe and may reduce drug compliance in primary health care based population chemotherapy.

Epidemiology of schistosomiasis mansoni in three endemic communities in north-east Ethiopia: baseline characteristics before endod based intervention.

As part of a pre-intervention baseline data collection the epidemiological characteristics of schistosomiasis mansoni were studied in 3 endemic communities (Kemise, Harbu and Bati towns) in northeast Ethiopia in April and May 1994. The objective was to generate data based on which post-intervention differences (in changes), if any, in transmission level could partly be explained for the 3 towns. After calculating the sample size required for each town 132, 75, 158 households were selected by systematic random sampling from Kemise, Harbu and Bati, respectively and all members of the selected households stool was examined by the Kato's thick smear method. Eighty eight and 85% of the houses harboured one or more cases of Schistosoma mansoni in Kemise and in Bati, respectively, all members of the households being positive in 27% in Kemise and in 28% in Bati. The overall prevalences were 59%, 33% and 51% in Kemise, Harbu and Bati, respectively, with the corresponding geometric mean egg counts (epg) of 240, 123 and 195 for positives and 26.5 and 15 for the whole populations. All ages combined, there were no significant differences due to sex both in prevalence and intensity of infection. By age, children in the 10-14 years age group were most affected (p = 0.007), their prevalences reaching 86%, 52% and 66% in Kemise, Harbu and Bati, respectively and their corresponding geometric mean epg being 377, 157 and 401, respectively. Heavy infection (> 100 epg) reached 42%, 32% and 16% in Kemise, Bati and Harbu, respectively, reaching an average of 55% among the 10-14 years of age. The implications of the epidemiological findings and the possible use of the household approach for rapid assessment of schistosomiasis magnitude in an area are discussed.

Leishmaniasis in the middle course of the Ethiopian Rift Valley: I. Clinical and leishmanin skin test surveys.

A clinico-epidemiological study of cutaneous leishmaniasis (CL) and visceral leishmaniasis (VL) was undertaken involving 1,809 residents of ten representative villages from Zeway-Langano, Wajifo-Mirab-Abaya and Blate-Dimtu areas in the middle course of the Ethiopian Rift Valley from November 1994 to June 1996. Community prevalence of positive leishmanin skin test (LST) was very low ranging from 5% in Olge village to 0% in Kello-Langano area. Sera collected from 57 clinical VL suspects originating from the different villages tested negative for anti-leishmanial antibodies. The rate of splenomegaly ranged from 5% in Kello-Langano area to as high as 80% in Korga village. Furthermore, the frequency and size of splenomegaly was related to the reported past and recent history of attack(s) of malaria. The low community prevalence of LST suggests minimal transmission of leishmania infections in spite of the knowledge of the presence of the sandfly vectors of CL and VL in the area. However, with increasing villagization and agricultural development activities, the potential risk for the establishment of VL and/or CL as endemic diseases can not be excluded.

Use of Leishmania major derived leishmanin for skin test surveys of visceral leishmaniasis in Ethiopia.

The potential use of Leishmania major derived leishmanin in surveys of visceral leishmaniasis (VL) was examined. The study was conducted in Konso sub-district, southwest Ethiopia involving 51 VL patients, 18 VL contacts, four localised cutaneous leishmaniasis (LCL) cases and 15 healthy controls. Sixty three percent of treated VL patients, 44.4% of VL contacts, all of LCL cases and none of untreated VL patients were positive to the test. Leishmanin skin test (LST) induration sizes of 41 treated VL patients were in the ranges of 0 to 10 mm, with a mean of 4.9 mm. The mean induration size and the positive LST rates in female patients were found to be significantly lower than in males. The major drawback of the antigen in the survey was the relatively smaller and flatter indurations. The relationship of LST to gender and leishmanial disease variant is discussed.

Seroepidemiological and leishmanin skin test surveys of visceral leishmaniasis in south and southwest Ethiopia.

Sero-epidemiological and leishmanin skin test surveys of visceral leishmaniasis were carried out in eight localities of South and Southwest Ethiopia between the July 1989 and June 1992. A total number of 4870 subjects comprising semi-pastoral nomads, peasants and farm labourers were included in the study. Areas of high and low leishmanin skin test positivity were identified, with rates varying from 1.0-80.5%. An enzyme-linked immunosorbent assay was used to determine prevalence of antileishmanial antibodies. The rates varied from 1.8% to 27.8%. Age and sex related serological and leishmanin skin test profiles are described. Correlation analysis of serological and leishmanin skin test was made for data in each locality. The relationships between seroprevalence, leishmanin skin test rates and prevalence of active visceral leishmaniasis and the implications on degrees of endemicity and patterns of transmission are discussed.

Visceral leishmaniasis in Gambela, western Ethiopia.

Active case finding, leishmanin skin test and serological surveys of visceral leishmaniasis were carried in selected localities in Gambela, Western Ethiopia, through the years 1989-1993. Active case detection surveys were made among 1456 Sudanese refugees, 646 Ethiopian Nuers and Anuaks, 651 resettlers at Baro-Abol and 165 patients from health centres in Itang. Fugnido and Kermi and Gambela hospital. Leishmanin skin test and sero-epidemiological studies were also conducted. A total of seven cases of visceral leishmaniasis were detected among refugees and none among resettlers, natives or 156 patients attending health centres and a hospital in Gambela. Positive leishmanin rates varied from 34.4% among refugees to 7.6% and 1.7% among Ethiopian Nuers and Anuaks and resettlers, respectively. Seroprevalence rates were also determined to be 18.1%, 7.3% and 8.1% respectively for the above order of study populations. Results are discussed in view of the currently ongoing leishmaniasis epidemic in the Upper Nile Province of the Sudan. The study emphasizes on the potential risk of imported visceral leishmaniasis being established in Western Ethiopia, where the disease is not known to be endemic until now.