SEARCH

SEARCH BY CITATION

Keywords:

  • Sudan;
  • leishmaniasis;
  • kala-azar;
  • PKDL;
  • clinical features;
  • diagnosis;
  • treatment;
  • entomology

Summary

  1. Top of page
  2. Summary
  3. Introduction
  4. Clinical features of VL
  5. Clinical symptoms of PKDL
  6. Clinical presentation of CL
  7. Clinical symptoms of SML
  8. Diagnosis
  9. Treatment
  10. Strain identification
  11. Entomology
  12. Reservoir studies
  13. References

The literature on the leishmaniases in the Sudan is reviewed with an emphasis on clinical aspects and on literature related to the recent outbreaks in the south and east of the country. The numbers of cases of subclinical infection and post-kala azar dermal leishmaniasis in the recent outbreaks are remarkable. New diagnostic techniques have been introduced and evaluated, notably the direct agglutination test and polymerase chain reaction technology. The latter gives very promising results and further research into application of the technique is warranted. Treatment with pentavalent antimony is still satisfactory. The reservoir host has not been identified definitely.


Introduction

  1. Top of page
  2. Summary
  3. Introduction
  4. Clinical features of VL
  5. Clinical symptoms of PKDL
  6. Clinical presentation of CL
  7. Clinical symptoms of SML
  8. Diagnosis
  9. Treatment
  10. Strain identification
  11. Entomology
  12. Reservoir studies
  13. References

The leishmaniases are a group of diseases with a broad range of clinical manifestations caused by several species of parasites belonging to the genus Leishmania (Family: Trypanosomatidae). The Leishmania parasite, a haemo-flagellate protozoan organism, is exclusively transmitted by the bite of a female sandfly of the genus Phlebotomus or Lutzomyia. There are three clinical forms of leishmaniasis: visceral leishmaniasis (VL) including post-kala azar dermal leishmaniasis (PKDL), cutaneous leishmaniasis (CL) and cutaneous leishmaniasis with involvement of the mucous membranes, also called mucocutaneous leishmaniasis (MCL).

In Sudan, VL and CL are endemic in several areas ( Figure 1). PKDL, a complication of VL of unknown cause, now occurs in up to 50% of cases ( Zijlstra et al. 1995 ), much more frequently than in the past ( Kirk & Sati 1940b). A particular form of ‘mucosal leishmaniasis’, different from MCL – which is found in Central and Latin America – occurs in Sudan. It is called Sudanese mucosal leishmaniasis (SML).

image

Figure 1. Endemic and epidemic areas of visceral and cutaneous leishmaniasis in the Sudan (adapted from Osman 1998 ).

Download figure to PowerPoint

VL is one of the most important endemic diseases in the country and Sudan is considered to be one of the main foci of VL in the world. Occasionally, severe epidemics have claimed the lives of thousands of people. In recent years the disease has spread outside established endemic areas, and a resurgence of cases has become apparent in regions with a previously low incidence ( Siddig et al. 1990 ). VL spreads over a wide belt from the Atbara river in the north-east along the Sudanese–Ethiopian border to south of the Sobat river and Nassir and Malakal and extending west across the White Nile. Other foci are the Kapoeta area, the Nuba Mountains and scattered areas in the Darfur region.

Epidemiology in historical perspective

Neave was the first to describe VL in Sudan in 1904 ( El-Hassan et al. 1995a ), although the disease was already known there in the 19th century ( Henderson 1937). At the turn of the 20th century, VL was recognized as a serious health problem in the Sudan. This realization led to the establishment of the Sudan Kala Azar Commission, which operated from 1909 to 1913 ( Zeese & Frank 1987). In the 3rd and 4th Wellcome Research Laboratory Reports published in 1908 and 1911, respectively, chapters are devoted to kala azar with notes on epidemiology, clinical and diagnostic aspects, trials at treatment, case descriptions and post mortem reports ( Balfour 1908, 1911). Archibald and Mansour (1937) identified the main endemic area as the Kassala and Fung districts bordering the Abyssinian frontier and the Kapoeta district in the south. Sporadic cases were found in the Nuba Mountains and in the western district of Darfur. At that time no epidemics had been described.

The first epidemic was reported in the Upper Nile Province in 1936–38: at least 300 cases occurred with a recorded death rate of 80% ( Stephenson 1940). The second epidemic in the southern Fung area of Blue Nile Province in 1956–60 killed thousands of people ( Sati 1958) and led to the establishment of a research team that between 1960 and 1964 provided clear data on medical and zoological aspects of the vector and reservoir hosts ( Hoogstraal & Heyneman 1969). In 1979–81 there was an increased number of cases in Melut ( Zeese & Frank 1987), an area described as a new focus in 1962 by Van Peenen & Reid. Around 1985 the average number of patients requiring treatment was 1300 per year, 75% of whom were treated in Gedaref and Hawata ( Zeese & Frank 1987).

In the last decade, several new outbreaks of VL occurred: a major epidemic in the south of the country ( Perea et al. 1991 ; Ashford et al. 1992 ; El-Hassan et al. 1993b ; Seaman et al. 1993 ) came to light only after VL had been found in the Khartoum area in 1988 among displaced people from Western Upper Nile Province who had fled the civil war in the south ( De Beer et al. 1991 ). Subsequent studies confirmed this ( Zijlstra et al. 1991b ; El-Hassan et al. 1993b ), and it became clear that a devastating outbreak had been going on in southern Sudan since 1984 ( Perea et al. 1991 ), which affected all age groups and by the end of 1988 had already killed 20–30 000 people ( Seaman et al. 1992 ). During the period 1986–95 an estimated 100 000 from a population of about 280 000 people died of the disease in Western Upper Nile Province. Population movement, civil war and poor nutritional status may have contributed to this high death rate ( Seaman et al. 1996 ).

The Masariya, a nomadic tribe from southern Kordofan in western Sudan, traditionally move their cattle to the northern part of the epidemic area in Western Upper Nile Province in search of pasture. During this trek they became infected and thus brought VL to their home area ( Hashim et al. 1994 ). In 1994 another outbreak was reported in Nasir District of Eastern Upper Nile Province which was probably related to people travelling to a food distribution centre located in the southern part of the VL-endemic zone in eastern Sudan ( Mercer et al. 1995 ). Until recently, at least 1000 cases of VL occurred each year in Gedaref State, eastern Sudan ( Zeese & Frank 1987; El-Hassan et al. 1995b ; Osman et al. 1998b ); the incidence of the disease was estimated to be stable at 4% ( Zijlstra et al. 1994 ). However, by the end of 1997, a sharp increase in the number of VL cases was reported from this area and also from Eritrea and the north-west Ethiopian focus ( McGregor 1998). This has continued through 1998 and 1999 (unpublished data).

The first case of possible PKDL was described by Christopherson (1921). The first definite cases were reported by Kirk and Drew (1938). The number of cases might have been much greater than supposed until recently, or may have increased over time ( Zijlstra et al. 1995 ). PKDL patients may serve as a reservoir for transmission of the parasite ( El-Hassan et al. 1992 ).

The first cases of CL in Sudan described at the beginning of the 20th century had contracted the disease in Egypt ( Kirk and Drew 1938). The first reported autochthonous CL case was from the Nuba mountains ( Archibald 1911). CL patients mainly come from Darfur and the central belt of Sudan ( Abdalla et al. 1973 ; Abdalla & Sherif 1978). So far, three outbreaks of CL have been reported: the first started in 1976–77 in the region of Shendi-Atbara north of Khartoum, the second in 1985 in and around El-Gerrsa in the White Nile area, and the last major epidemic took place in Khartoum Province with about 10 000 recorded cases in 1985–87. Heavy rainfall after several years of drought, the discontinuation of insecticide spraying for malaria control and rodent outbreaks have all been implicated as factors in the outbreaks ( El-Safi & Peters 1991).

SML is uncommon: only 78 cases have been reported since the disease was first described by Christopherson in 1914 ( El-Hassan et al. 1995a ). SML is seen in adult males in VL-endemic areas: eastern Sudan, Darfur and Kordofan. Cases are sporadic and isolated: SML has never occurred in epidemic form.

Clinical features of VL

  1. Top of page
  2. Summary
  3. Introduction
  4. Clinical features of VL
  5. Clinical symptoms of PKDL
  6. Clinical presentation of CL
  7. Clinical symptoms of SML
  8. Diagnosis
  9. Treatment
  10. Strain identification
  11. Entomology
  12. Reservoir studies
  13. References

Skin manifestations

After the infectious bite of the sandfly a ‘leishmanioma’ may appear. We do not know how often this happens as it is infrequently reported and generally seems to go unnoticed. A leishmanioma is a nonitching papule that may ulcerate and then resemble CL ( Kirk 1938), but in general it evolves gradually into a tuberculoid lesion ( Manson-Bahr 1959). Histologically it consists of lymphocytes, macrophages and plasma cells ( El Hassan & Modabber 1999). The leishmanioma may precede VL or be present when VL becomes manifest. Two of four leishmanioma patients studied in Upper Nile Province developed VL ( Adler et al. 1966 ). In another study, one of five leishmanioma cases not treated and followed up 6 months later developed VL, another developed PKDL without apparent VL and the remaining three were without symptoms ( Zijlstra et al. 1994 ). Skin pigmentation did not change ( Siddig et al. 1990 ), in contrast to the situation in India, where the dark skin associated with VL gave the disease its Hindi name kala azar (‘black sickness’).

Other clinical manifestations

The clinical features of Sudanese VL have been described by a number of authors ( Henderson 1937; Van Peenen & Reid 1962; Ahmed et al. 1988 ; El-Hassan et al. 1990a ; Siddig et al. 1990 ; El-Safi et al. 1991b ; Zijlstra et al. 1991a b; Hashim & El-Hassan 1994; Hashim et al. 1994 , 1995). The disease is characterized by the development of fever, splenomegaly, varying degrees of hepatomegaly, weight loss in combination with a healthy appetite, and pancytopenia. Splenomegaly may be absent: in 4% of cases Zijlstra et al. (1991b) did not observe an enlarged spleen. The number of patients with lymphadenopathy ranges from 36% ( Hashim et al. 1994 ) to more than 80% ( Zijlstra et al. 1991a ).

Complications

Complications such as epistaxis ( El-Hassan et al. 1990a ; Siddig et al. 1990 ), severe tinea versicolor due to depressed cell-mediated immunity ( Hashim & El-Hassan 1994) and neurological changes such as deafness, foot drop and a sensation of burning feet ( Hashim et al. 1995 ) have been reported.

Congenital and placental leishmaniasis

A case of congenital leishmaniasis was reported, together with a patient who a few days after the start of treatment of VL aborted a 5-month-old foetus. The placenta contained many parasites, the foetus did not ( Eltoum et al. 1992 ).

Subclinical infection

In Sudan subclinical infection was defined as serological conversion and/or conversion in the leishmanin skin test (LST) in the absence of clinical symptoms. Using this definition, the ratio of clinical to subclinical cases was 1.6:1 and 2.4:1 in two successive years in a longitudinal study in eastern Sudan ( Zijlstra et al. 1994 ). This ratio is higher than those in Italy (1:4), Kenya (1:5) ( Ho et al. 1982 ) and Brazil (1:18.5 for ‘a study area at large’ and 1:6.5 for the ‘area with the highest prevalence of disease’) ( Badaro et al. 1986a ). The Italian and Kenyan studies were cross-sectional and used a combination of serology (ELISA) and skin test and no clinical symptoms to define subclinical infection. The Sudanese and Brazilian studies were prospective. As mentioned, the Sudanese study defined subclinical infection as conversion in direct agglutination test (DAT) and/or LST without development of clinical symptoms, while in Brazil subclinical infection was defined as having a positive serological test for leishmaniasis (ELISA) and symptoms of long duration with low-grade fever, malaise, poor weight gain, cough, diarrhoea, hepatomegaly and sometimes splenomegaly. Some of these children developed full-blown VL within 5 months (they would not be called subclinical infection in Sudan), the others had protracted disease (mean 35 months), but recovered ( Badaro et al. 1986b ). Differences in definition, epidemiology and tools thus explain the discrepancies in the reported figures.

Clinical symptoms of PKDL

  1. Top of page
  2. Summary
  3. Introduction
  4. Clinical features of VL
  5. Clinical symptoms of PKDL
  6. Clinical presentation of CL
  7. Clinical symptoms of SML
  8. Diagnosis
  9. Treatment
  10. Strain identification
  11. Entomology
  12. Reservoir studies
  13. References

PKDL is a recognized complication of VL of unknown cause. A rash with tiny papules on the face resembling measles and papular lesions on a background of depigmented macules are the most common clinical presentations in eastern Sudan ( Zijlstra et al. 1995 ). Rarely, eye lesions associated with past or concomitant PKDL occur ( El-Hassan et al. 1998 ). In a population-based study 56% of VL patients developed PKDL after treatment ( Zijlstra et al. 1995 ). This figure is higher than the other reported frequencies of 20% ( Kirk & Sati 1940b; Zijlstra et al. 1993 ) and 29% ( Osman et al. 1998b ). PKDL occasionally occurs in the absence of a history of clinically manifest VL ( El-Hassan et al. 1990b ) or during treatment of VL, but it generally appears directly or up to 6 months post-treatment ( Zijlstra et al. 1995 ). This is faster than Indian PKDL which typically shows up 1–5 years after cure. The nodular and hypopigmented macular forms of PKDL, especially in the absence of a history of VL, may be confused with lepromatous leprosy, as may the pathology ( El-Hassan et al. 1993a ). Unlike leprosy patients, PKDL patients have no sensory loss or motor power deficit. Finding the parasites in smears by microscopy or polymerase chain reaction (PCR) and a positive DAT may also assist in distinguishing PKDL from leprosy ( El-Hassan et al. 1992 ; Harith et al. 1996 ; Osman et al. 1998a ).

Clinical presentation of CL

  1. Top of page
  2. Summary
  3. Introduction
  4. Clinical features of VL
  5. Clinical symptoms of PKDL
  6. Clinical presentation of CL
  7. Clinical symptoms of SML
  8. Diagnosis
  9. Treatment
  10. Strain identification
  11. Entomology
  12. Reservoir studies
  13. References

CL in Sudan is similar to the disease in other endemic areas. There are 3 types: nodular or nodular-ulcerative, ulcerative and diffuse infiltrative ( Abdalla et al. 1973 ). Most patients have multiple lesions of the nodular or ulcerative type ( El-Safi et al. 1991a ). Typically, lesions start to heal spontaneously after approximately three months ( Abdalla & Sherif 1978).

Clinical symptoms of SML

  1. Top of page
  2. Summary
  3. Introduction
  4. Clinical features of VL
  5. Clinical symptoms of PKDL
  6. Clinical presentation of CL
  7. Clinical symptoms of SML
  8. Diagnosis
  9. Treatment
  10. Strain identification
  11. Entomology
  12. Reservoir studies
  13. References

Unlike American mucocutaneous leishmaniasis, Sudanese mucosal leishmaniasis is not preceded or accompanied by cutaneous lesions. Three clinical presentations of SML have been reported: nasal, which is characterized by nasal obstruction, mucoid discharge and slight bleeding; oral, where the patient complains of a sensation of fullness of the mouth, spontaneous loss of teeth and bleeding from the gum; and oro-nasal, where the hard palate may perforate ( El-Hassan et al. 1995a ). The disease is almost exclusively found in adult males (20–70 years) ( Abdalla et al. 1975 ; El-Hassan et al. 1995a ) and characterized by long duration if not treated ( Abdalla et al. 1975 ).

Diagnosis

  1. Top of page
  2. Summary
  3. Introduction
  4. Clinical features of VL
  5. Clinical symptoms of PKDL
  6. Clinical presentation of CL
  7. Clinical symptoms of SML
  8. Diagnosis
  9. Treatment
  10. Strain identification
  11. Entomology
  12. Reservoir studies
  13. References

Parasitological diagnosis

In the first described VL case in Sudan, the parasite was detected in the spleen, and by the early years of the 20th century, VL was frequently diagnosed by demonstrating parasites in splenic aspirates, a technique described by Bousfield (1911–12 ) and used by many workers both in the field and in the clinic. Three studies showed sensitivities of at least 92% ( Van Peenen & Reid 1962; Siddig et al. 1988 ; Zijlstra et al. 1992 ).

Lymph node aspiration was introduced by Kirk & Sati (1940a). At present, microscopy on lymph node aspirates is the most commonly used procedure to confirm a diagnosis of VL. The method is safe ( Siddig et al. 1988 ) but varies in sensitivity from 58.3% ( Zijlstra et al. 1992 ), 78% ( Siddig et al. 1988 ) and 81.6% ( Osman et al. 1997b ) to 100% ( Kirk & Sati 1940a). Microscopy of bone marrow aspirates (70.2%) was less sensitive than microscopy of splenic aspirates (96.4%), but more sensitive than microscopic examination of lymph node aspirates (58%) ( Zijlstra et al. 1992 ).

Many authors mention that it is extremely difficult to find parasites in peripheral blood ( Archibald & Mansour 1937; Henderson 1937; Kirk & Sati 1940a; Stephenson 1940; Van Peenen & Reid 1962). In contrast to some contemporaries ( Balfour 1908), Marshall (1911) found parasites in 13 of 15 (86%) blood samples. Rohrs (1964) detected parasites in the venous blood of 4 of 20 confirmed VL patients. Archibald & Mansour (1937) claimed that even though no parasites could be found in blood films from the Fung district, all blood films of VL patients from the Kapoeta district were positive. Using peripheral blood spots on filter paper from confirmed VL patients, Osman detected Leishmania DNA in 70% of the samples by PCR ( Osman et al. 1997b ).

Parasites have been found in skin biopsies ( Kirk & Sati 1940a; Gumaa et al. 1988 ) and nasal smears of VL patients ( Archibald & Mansour 1937; Henderson 1937; Rohrs 1964). The parasite load in skin samples from PKDL patients is lower than from CL patients ( El-Hassan et al. 1992 ). Examination of paraffin-embedded skin biopsies from PKDL patients revealed Leishmania parasites in all 14 samples tested ( El-Hassan et al. 1992 ). In contrast, a sensitivity of only 20% was reported by Ismail et al. (1997) . Using an immunoperoxidase technique and anti-L. donovani monoclonal antibody, they achieved high sensitivity with microscopy. Using slit skin smears of PKDL patients, Leishmania DNA was detected in 19 of 23 samples by PCR, whereas with microscopy parasites were only found in seven ( Osman et al. 1998a ). In CL patients, microscopy on slit skin smears is often positive with sensitivity ranging from 54.5% to 100% ( Abdalla & Sherif 1978; El-Safi et al. 1991a ; Andresen et al. 1996 ). In SML patients the sensitivity of microscopy on smear samples was 85.7% ( Abdalla et al. 1975 ) and 100% ( El-Hassan et al. 1995a ).

Serological diagnosis

Serological diagnosis, mainly the direct agglutination test (DAT), has been compared with parasitological methods. In several studies the DAT was highly sensitive (94–100%) and specific (74–100%) ( Abdel-Hameed et al. 1989 ; El-Safi & Evans 1989; Zijlstra et al. 1991b ). 331 of 654 displaced persons from southern Sudan who were clinically suspect of VL but without parasites in the bone marrow tested postive with the DAT ( De Beer et al. 1991 ) and responded to specific therapy. In war-torn southern Sudan, struck by an extensive outbreak, high titres in the DAT together with suggestive clinical symptoms were considered sufficient evidence of VL to start treatment ( Seaman et al. 1993 ). The performance of the DAT using both aqueous and freeze-dried antigen under field conditions has been evaluated in separate studies in southern and eastern Sudan. Both antigens performed equally well ( Meredith et al. 1995 ; Zijlstra et al. 1997 ), giving identical titres or a difference of only ± 1 dilution in 92–98% of the samples tested in two successive surveys ( Zijlstra et al. 1997 ). Boelaert (1999) reports a series of evaluations of the utility of DAT in Sudan and elsewhere.

The immunofluorescent antibody test (IFAT) and ELISA have also been used in Sudan, but only in a few research studies. Abdalla (1980) found all 50 sera from confirmed VL patients positive in the IFAT at a dilution of 1:200; 33 sera (66%) were positive at a dilution of 1:400, but 16% of 150 controls from the endemic area tested positive at the same dilution and 3.3% of nonendemic controls were positive at a dilution of 1:100. El Amin et al. (1985) found all 25 VL patients’ sera positive in an ELISA. Using another ELISA, El-Safi & Evans (1989) found all 25 confirmed VL patients and 10 of 14 VL suspects positive.

El Amin et al. (1986 ) compared ELISA, IFAT and indirect haemagglutination (IHA) in 24 sera from confirmed VL patients: all sera tested positive in the three tests, with the ELISA giving higher titres. All three tests gave cross-reactions with sera from patients with African trypanosomiasis which disappeared at higher dilutions in ELISA. In another comparative study, all 25 sera from confirmed VL cases were positive in both ELISA and DAT. The two tests did not differ significantly in VL suspects: 9 of 14 were positive in DAT and 10 were positive in ELISA ( El-Safi & Evans 1989).

Leishmanin skin test

There are only few reports on the use of the leishmanin skin test (LST) in Sudan. The LST is characteristically negative during active VL and became positive in 81% of cured cases within 6 months ( Zijlstra & El-Hassan 1993). Only 59% of PKDL patients tested positive ( Zijlstra & El-Hassan 1993). The LST is a useful tool for epidemiological investigations and surveys and can be used to quantify transmission of leishmaniasis. A team working on the epidemiology of VL in southern Sudan found 59% of the individuals tested were LST-positive, compared to 10% in an area where the disease was unknown ( Hoogstraal & Heyneman 1969). During the VL epidemic in southern Sudan, 43% of survivors in two villages were LST-positive ( Seaman et al. 1992 ). In a longitudinal study in eastern Sudan, most people had a positive LST, possibly due to previous exposure to L. major in their homeland in western Sudan from where they had migrated in the 1980s. L. major causes CL and a positive LST. As VL was observed to occur only in previously LST-negative individuals, previous CL might protect against subsequent VL, a possibility that warrants further research ( Zijlstra et al. 1994 ). As in CL, the LST is almost always positive in SML ( Abdalla et al. 1975 ; El-Safi et al. 1991b ; El-Hassan et al. 1995a ).

Molecular diagnosis

Recently, the value of PCR for the diagnosis of leishmaniasis has been examined. The technique was tested with VL samples of different clinical materials (peripheral blood, aspirates from lymph nodes and bone marrow); with samples taken at different stages of the disease from the endemic area in eastern Sudan ( Osman et al. 1997a b, 1998b) and in a hospital-based study ( Andresen et al. 1997 ). In parasitologically confirmed patients PCR was as sensitive as microscopy. In clinically suspect individuals (clinical features of VL, positive serological test and response to treatment but with negative microscopy), PCR was positive in about 50% of cases ( Osman et al. 1997b ). PCR was positive in 70% of confirmed cases on peripheral blood and in 17% of suspected cases ( Osman et al. 1997b ). Thus PCR is likely to be of value in the diagnosis of VL and further studies are warranted. Where the ‘gold standard’ of the diagnosis of VL, i.e. demonstration of parasites, is difficult or impossible, clinicians have to make decisions based on the best evidence available. PCR can be helpful here with proper interpretation in the full context. PCR was also used to diagnose PKDL ( Osman et al. 1998a ) and CL ( Andresen et al. 1996 ) and proved more sensitive than routine microscopy in all cases.

Treatment

  1. Top of page
  2. Summary
  3. Introduction
  4. Clinical features of VL
  5. Clinical symptoms of PKDL
  6. Clinical presentation of CL
  7. Clinical symptoms of SML
  8. Diagnosis
  9. Treatment
  10. Strain identification
  11. Entomology
  12. Reservoir studies
  13. References

Since its introduction in Sudan, sodium stibogluconate continues to be the drug of choice, although treatment is expensive at US$ 60–200 per course ( Desjeux 1992; Veeken et al. 2000 ). Pentamidine has been used in the past ( Kirk 1947) and more recently 49 patients were treated with different schedules of liposomal amphotericin B with high cure rates of 88% to 94% in higher-dosed regimens ( Seaman et al. 1995 ). The cost of this treatment precludes use at any scale. Antimony is the drug in general use and is discussed here. In the 1960s, Van Peenen & Reid (1962) used a total dose of 600 mg/kg spread over 14 days or more and achieved an initial cure rate of 65%; 20% died. Fearing toxicity of sodium stibogluconate, many physicians used 10 mg/kg/day for 15 days ( Zijlstra et al. 1993 ) instead of the WHO-recommended dose of 20 mg/kg/day for 30 days ( World Health Organization 1990).

In a comparative trial in southern Sudan, 134 patients were randomized to treatment with sodium stibogluconate at 20 mg/kg/day for 30 days or the same drug at a dose of 20 mg/kg/day plus aminosidine at 15 mg/kg/day for 17 days. Five patients (7%) in group I and three patients (4%) in group II died. All patients who completed treatment were clinically cured. At days 15–17, the parasite clearance rate was 95% in group II and 81% in group I. At the end of treatment, 93.4% of splenic aspirates in group I were negative, comparable to group II ( Seaman et al. 1993 ). Follow-up was not possible in this trial.

In another comparative randomized trial in Khartoum, Zijlstra et al. (1993) compared a regimen of stibogluconate at 10 mg/kg/day for 30 days with 20 mg/kg/day for 15 and for 30 days. They found no significant difference between the three regimens, but the groups were small (29, 37 and 38 patients). Khalil et al. (1998) reported that in the period 1989–95, 98% of 1593 VL patients responded well to treatment with Pentostam using the three treatment regimens described above. However, this was a retrospective, descriptive study, not comparative, not randomized. It included patients from different endemic areas, treated at different hospitals in Khartoum and follow-up data were often not available.

In contrast, 23 of 49 (47%) patients in eastern Sudan were not cured after well-supervised treatment with daily stibogluconate at a dose of 20 mg/kg/day for 4 weeks: 14 (28.5%) developed PKDL and nine (18%) had recurrent VL with reappearance of parasites in aspirates. Four of these patients died ( Osman et al. 1998b ).

PKDL often clears by itself ( Zijlstra et al. 1995 ), but once systemic antimony treatment is deemed necessary, a dose of stibogluconate 20 mg/kg/day for at least 30 days seems advisable ( El-Hassan et al. 1992 ). Indications for treatment, the optimum dose and duration have yet to be determined. Ketoconazole at 10 mg/kg/day for 4 weeks was ineffective ( El-Hassan et al. 1992 ), as was a combination of two antifungal drugs, terbinafine and itraconazole ( Khalil et al. 1996 ).

If it is not extensive, CL may clear by itself and does not necessarily require treatment. In extensive and disfiguring disease or when multiple lesions are present, treatment with antimony 600 mg/day for 3–4 weeks was successful ( El-Safi et al. 1991a ). The response of SML patients to pentavalent antimony (ten patients, one death, seven cures, one lost and one relapse/cure after ketoconazole) or ketoconazole (four patients, three cured) was good ( El-Hassan et al. 1995a ).

Treatment of VL with pentavalent antimony resulted in death rates of 4.8% to 20% ( Van Peenen & Reid 1962; El-Hassan et al. 1990a ; De Beer et al. 1991 ; Zijlstra et al. 1991a ; Seaman et al. 1993 , 1997). Relapse rates of VL after sodium stibogluconate therapy varied between 1 and 2% ( Sati 1958), 6% ( Siddig et al. 1989 ), 3% ( Zijlstra et al. 1993 ) and 18% ( Osman et al. 1998b ). In lymph node aspirates obtained from Sudanese VL patients immediately after treatment, Leishmania DNA was detected by PCR in 82% of the samples ( Osman et al. 1998b ). Incomplete treatment and suboptimal dosing have both been implicated in the occurrence of complications after treatment ( Zijlstra et al. 1995 ; Khalil et al. 1998 ), although in the small study of Osman et al. (1998b) treatment was well supervised.

Strain identification

  1. Top of page
  2. Summary
  3. Introduction
  4. Clinical features of VL
  5. Clinical symptoms of PKDL
  6. Clinical presentation of CL
  7. Clinical symptoms of SML
  8. Diagnosis
  9. Treatment
  10. Strain identification
  11. Entomology
  12. Reservoir studies
  13. References

Most epidemiological evidence suggests that VL in Sudan is a zoonosis caused by L. donovani sensu lato ( Kirk 1956; Hoogstraal & Heyneman 1969; Elnaiem et al. 1997 ; Oskam et al. 1998 ). Isoenzyme analysis showed that isolates from Sudanese VL patients were all L. donovani s.l. with zymodemes belonging to an ancient ancestral cluster ( Ashford et al. 1992 ; Oskam et al. 1998 ). Restriction fragment length polymorphism (RFLP) analysis showed that in eastern Sudan the causative agent of VL and PKDL was L. donovani s.l. ( El-Hassan et al. 1993c ; Meredith et al. 1993 ). Using different molecular biological techniques, isolates from this area were identified as L. donovani s.s. ( Oskam et al. 1998 ).

CL is caused by L. major ( Abdalla et al. 1973 ; El-Safi et al. 1991a ; Ibrahim et al. 1995 ; Andresen et al. 1996 ) and L. tropica ( Abdalla & Sherif 1978). L. donovani and L. major seem to be the causative agents for SML ( Ghalib et al. 1992 ; El-Hassan et al. 1995a ).

Entomology

  1. Top of page
  2. Summary
  3. Introduction
  4. Clinical features of VL
  5. Clinical symptoms of PKDL
  6. Clinical presentation of CL
  7. Clinical symptoms of SML
  8. Diagnosis
  9. Treatment
  10. Strain identification
  11. Entomology
  12. Reservoir studies
  13. References

Nine Phlebotomus and 29 Sergentomyia species have so far been found in Sudan ( Elnaiem et al. 1997 ). The only proven vector of VL in Sudan is P. orientalis, which abounds in woodlands dominated by Acacia seyal and Balanites aegyptiaca trees ( Quate 1964; Adler et al. 1966 ; Hoogstraal & Heyneman 1969; Ashford & Thomson 1991; Elnaiem et al. 1997 , 1998a; b). P. orientalis had an exceptionally high infection rate (10%) in southern Sudan ( Schorscher & Goris 1992). In the Kapoeta area in south Sudan, where P. orientalis is not known to be present, P. martini may, as in Kenya, be the main vector of VL ( Minter et al. 1962 ). Elnaiem & Osman (1998) confirmed intravillage transmission by PCR of sandfly material.

P. papatasi was incriminated as a vector for CL during the epidemics in central and northern Sudan (where P. orientalis is absent) in 1976–78 ( Abdalla & Sherif 1978). Earlier studies had indicated that P. papatasi is not a suitable vector for L. donovani ( Hoogstraal & Heyneman 1969).

Reservoir studies

  1. Top of page
  2. Summary
  3. Introduction
  4. Clinical features of VL
  5. Clinical symptoms of PKDL
  6. Clinical presentation of CL
  7. Clinical symptoms of SML
  8. Diagnosis
  9. Treatment
  10. Strain identification
  11. Entomology
  12. Reservoir studies
  13. References

Outbreaks of leishmaniasis in troops in uninhabited areas ( Kirk 1956) and infected P. orientalis (3.5–7.1%) in the uninhabited Dinder National Park ( Elnaiem et al. 1998a ) strongly suggest a reservoir host other than man in Sudan. Man-to-man transmission via sandflies is also likely, especially during epidemics.

A number of studies have been devoted to the identification of the reservoir host of Leishmania in Sudan. Archibald & Mansour (1937) did not find the parasite in dogs, cats, fowl, rats, mice, sheep, goats, squirrels, bats, lizards and geckos. In later reports the parasite was isolated from Cercopithecus aethiops and Vulpus pallida ( Kirk 1956), Rattus rattus, Acomys albigena, Arvicanthis niloticus, Genetta senegalensis and Felis serval ( Adler et al. 1966 ; Hoogstraal & Heyneman 1969). El-Hassan et al. (1993c) detected Leishmania DNA in Arvicanthis niloticus, the incriminated reservoir of L. donovani in eastern Sudan. Despite repeated investigations and trials of experimental infection, no infected dogs, the main reservoir host in the Mediterranean area, were found ( Archibald & Mansour 1937; Hoogstraal & Heyneman 1969). Thus the dog is unlikely to be a vertebrate reservoir host in Sudan. Both Kirk (1956) and El-Hassan et al. (1992) suggest that PKDL patients may serve as a reservoir for the parasite.

References

  1. Top of page
  2. Summary
  3. Introduction
  4. Clinical features of VL
  5. Clinical symptoms of PKDL
  6. Clinical presentation of CL
  7. Clinical symptoms of SML
  8. Diagnosis
  9. Treatment
  10. Strain identification
  11. Entomology
  12. Reservoir studies
  13. References
  • Abdalla RE (1980) Serodiagnosis of visceral leishmaniasis in an endemic area of the Sudan. Annals of Tropical Medicine and Parasitology 74, 415 419.
  • Abdalla RE, Ali M, Wasfi AI, El Hassan AM (1973) Cutaneous leishmaniasis in the Sudan. Transactions of the Royal Society of Tropical Medicine and Hygiene 67, 549 559.
  • Abdalla RE, El Hadi A, Ahmed MA, El Hassan AM (1975) Sudan mucosal leishmaniasis. Transactions of the Royal Society of Tropical Medicine and Hygiene 69, 443 449.
  • Abdalla RE & Sherif H (1978) Epidemic of cutaneous leishmaniasis in northern Sudan. Annals of Tropical Medicine and Parasitology 72, 349 352.
  • Abdel-Hameed AA, Harith AE, Abdel-Rahim IM (1989) Potential of a direct agglutination test (DAT) for detection of visceral leishmaniasis in a known endemic area in Sudan. Tropical Medicine and Parasitology 40, 470 471.
  • Adler S, Foner A, Montiglio B (1966) The relationship between human and animal strains of Leishmania from the Sudan. Transactions of the Royal Society of Tropical Medicine and Hygiene 60, 380 386.
  • Ahmed MAM, Suleman SM, Kordofani AAY, Mustafa MD (1988) Outbreak of visceral leishmaniasis on the western bank of the White Nile-Sudan, report and clinical study. East African Medical Journal 65, 824 828.
  • Andresen K, Gaafar A, El-Hassan AM et al. (1996) Evaluation of the polymerase chain reaction in the diagnosis of cutaneous leishmaniasis due to Leishmania major: a comparison with direct microscopy of smears and sections from lesions. Transactions of the Royal Society of Tropical Medicine and Hygiene 90, 133 135.
  • Andresen K, Gasim S, Elhassan AM et al. (1997) Diagnosis of visceral leishmaniasis by the polymerase chain reaction using blood, bone marrow and lymph node samples from patients from the Sudan. Tropical Medicine and International Health 2, 440 444.
    Direct Link:
  • Archibald RG (1911) A case of parasitic granuloma in which development forms of Leishmania tropica were present. Fourth Report of the Wellcome Tropical Research Laboratory A, 207 211.
  • Archibald RG & Mansour H (1937) Some observations on the epidemiology of kala-azar in the Sudan. Transactions of the Royal Society of Tropical Medicine and Hygiene 30, 395 406.
  • Ashford RW, Seaman J, Schorscher J, Pratlong F (1992) Epidemic visceral leishmaniasis in southern Sudan: identity and systematic position of the parasites from patients and vectors. Transactions of the Royal Society of Tropical Medicine and Hygiene 86, 379 380.
  • Ashford RW & Thomson MC (1991) Visceral leishmaniasis in Sudan. A delayed development disaster? Annals of Tropical Medicine and Parasitology 85, 571 572.
  • Badaro R, Jones TC, Carvalho EM et al. (1986b) New perspectives on a subclinical form of visceral leishmaniasis. Journal of Infectious Diseases 154, 1003 1011.
  • Badaro R, Jones TC, Lorenco R et al. (1986a) A prospective study of visceral leishmaniasis in an endemic area of Brazil. Journal of Infectious Diseases 154, 639 649.
  • Balfour A(ed.) (1908) Third Report of the Wellcome Research Laboratories at the Gordon Memorial College, Khartoum. Baillière, Tindall & Cox, London.
  • Balfour A(ed.) (1911) Fourth Report of the Wellcome Research Laboratories at the Gordon Memorial College, Khartoum. Baillière, Tindall & Cox, London.
  • Boelaert M (1999) The value of serodiagnosis for visceral leishmaniasis, a validation approach through latent class analysis. PhD thesis , University of Gent, Gent.
  • Bousfield L (191112) Some remarks on kala-azar in the Sudan. Transactions of the Society of Tropical Medicine and Hygiene 5, 234 239.
  • Christopherson JB (1921) Intravenous injection of antimony tartrate. Lancet i, 522 525.
  • De Beer P, El Harith A, Deng LL, Semiao-Santos SJ, Chantal B, Van Grootheest M (1991) A killing disease epidemic among displaced Sudanese population identified as visceral leishmaniasis. American Journal of Tropical Medicine and Hygiene 44, 283 289.
  • Desjeux P (1992) Human leishmaniases: epidemiology and public health aspects. World Health Statistics Quarterly 45, 267 275.
  • El Amin ERM, Wright EP, Abdel Rahman AM, Kolk A, Laarman JJ, Pondman KW (1986) Serodiagnosis of Sudanese visceral and mucosal leishmaniasis: comparison of ELISA-immunofluorescence and indirect haemagglutination. Transactions of the Royal Society of Tropical Medicine and Hygiene 80, 271 274.
  • El Amin ERM, Wright EP, Kager PA, Laarman JJ, Pondman KW (1985) ELISA using intact promastigotes for immunodiagnosis of kala-azar. Transactions of the Royal Society of Tropical Medicine and Hygiene 79, 344 350.
  • El-Hassan AM & Modabber F (1999) Visceral leishmaniasis: pathology and pathogenesis. In: Protozoal Diseases(ed. MGilles) Arnold, London, pp. 440 446.
  • El-Hassan AM, Ahmed MAM, Abdul Rahim AG et al. (1990a) Visceral leishmaniasis in the Sudan: clinical and haematological features. Annals of Saudi Medicine 10, 51 56.
  • El-Hassan AM, Ghalib HW, Zijlstra EE et al. (1992) Post kala-azar dermal leishmaniasis in the Sudan: clinical features, pathology and treatment. Transactions of the Royal Society of Tropical Medicine and Hygiene 86, 245 248.
  • El-Hassan AM, Ghalib HW, Zijlstra E, Eltoum IA, Ali MS, Ahmed HMA (1990b) Post-kala-azar dermal leishmaniasis in the absence of active visceral leishmaniasis. Lancet 336, 750.
  • El-Hassan AM, Hashim FA, Abdullah M, Zijlstra EE, Ghalib HW (1993a) Distinguishing post-kala-azar dermal leishmaniasis from leprosy: experience in the Sudan. Leprosy Review 64, 53 59.
  • El-Hassan AM, Hashim FA, Siddig Ali M, Ghalib HW, Zijlstra EE (1993b) Kala-azar in western Upper Nile province in the southern Sudan and its spread to a nomadic tribe from the north. Transactions of the Royal Society of Tropical Medicine and Hygiene 87, 395 398.
  • El-Hassan AM, Khalil EAG, El Sheikh EA, Zijlstra EE, Osman A, Ibrahim ME (1998) Post kala-azar ocular leishmaniasis. Transactions of the Royal Society of Tropical Medicine and Hygiene 92, 177 179.
  • El-Hassan AM, Meredith SEO, Yagi HI et al. (1995a) Sudanese mucosal leishmaniasis: epidemiology, clinical features, diagnosis, immune responses and treatment. Transactions of the Royal Society of Tropical Medicine and Hygiene 89, 647 652.
  • El-Hassan AM, Zijlstra EE, Ismael A, Ghalib HW (1995b) Recent observations on the epidemiology of kala-azar in the Eastern and Central States of the Sudan. Tropical and Geographical Medicine 47, 151 156.
  • El-Hassan AM, Zijlstra EE, Meredith SEO, Ghalib HW, Ismail A (1993c) Identification of Leishmania donovani using a polymerase chain reaction in patient and animal material obtained from an area of endemic kala-azar in the Sudan. Acta Tropica 55, 87 90.
  • Elnaiem DA, Ward RD, Hassan HK, Miles MA, Frame IA (1998a) Infection rates of Leishmania donovani in Phlebotomus orientalis from a focus of visceral leishmaniasis in eastern Sudan. Annals of Tropical Medicine and Parasitology 92, 229 232.
  • Elnaiem DA, Connor SJ, Thomson MC et al. (1998b) Environmental determinants of the distribution of Phlebotomus orientalis in Sudan. Annals of Tropical Medicine and Parasitology 92, 877 887.
  • Elnaiem DA, Hassan HK, Ward RD (1997) Phlebotomine sandflies in a focus of visceral leishmaniasis in a border area of eastern Sudan. Annals of Tropical Medicine and Parasitology 91, 307 318.
  • Elnaiem DA & Osman OF (1998) Evidence for active transmission of visceral leishmaniasis within a village in eastern Sudan. Acta Tropica 71, 305 309.
  • El-Safi SH & Evans DA (1989) A comparison of the direct agglutination test and enzyme-linked immunosorbent assay in the serodiagnosis of leishmaniasis in the Sudan. Transactions of the Royal Society of Tropical Medicine and Hygiene 83, 334 337.
  • El-Safi SH & Peters W (1991) Studies on the leishmaniases in the Sudan. 1. Epidemic of cutaneous leishmaniasis in Khartoum. Transactions of the Royal Society of Tropical Medicine and Hygiene 85, 44 47.
  • El-Safi SH, Peters W, El-Toam B, El-Kadarow A, Evans DA (1991a) Studies on the leishmaniases in the Sudan. 2. Clinical and parasitological studies on cutaneous leishmaniasis. Transactions of the Royal Society of Tropical Medicine and Hygiene 85, 457 464.
  • El-Safi SH, Peters W, Evans DA (1991b) Studies on the leishmaniases in the Sudan. 3. Clinical and parasitological studies on visceral and mucosal leishmaniasis. Transactions of the Royal Society of Tropical Medicine and Hygiene 85, 465 470.
  • Eltoum IA, Zijlstra EE, Ali MS et al. (1992) Congenital kala-azar and leishmaniasis in the placenta. American Journal of Tropical Medicine and Hygiene 46, 57 62.
  • Ghalib HW, Eltoum IA, Kroon CCM, El Hassan AM (1992) Identification of Leishmania from mucosal leishmaniasis by recombinant DNA. Transactions of the Royal Society of Tropical Medicine and Hygiene 86, 158 160.
  • Gumaa SA, Ahmed MA, Hassan ME, Hassan AM (1988) A case of African histoplasmosis from Sudan. Transactions of the Royal Society of Tropical Medicine and Hygiene 82, 503 505.
  • Harith AE, Chowdury S, Al-Masum A et al. (1996) Reactivity of various leishmanial antigens in a direct agglutination test and their value in differentiating post-kala azar dermal leishmaniasis from leprosy and other skin conditions. Journal of Medical Microbiology 44, 141 146.
  • Hashim FA, Ahmed AE, El-Hassan AM et al. (1995) Neurologic changes in visceral leishmaniasis. American Journal of Tropical Medicine and Hygiene 52, 149 154.
  • Hashim FA, Ali MS, Satti M et al. (1994) An outbreak of acute kala-azar in a nomadic tribe in western Sudan: features of the disease in a previously non-immune population. Transactions of the Royal Society of Tropical Medicine & Hygiene 88, 431 432.
  • Hashim FA & El-Hassan AM (1994) Tinea versicolor and visceral leishmaniasis. International Journal of Dermatology 33, 258 259.
  • Henderson LH (1937) Clinical observations on kala-azar in the Fung province of the Anglo-Egyptian Sudan. Transactions of the Royal Society of Tropical Medicine and Hygiene 31, 179 190.
  • Ho M, Siongkok TK, Lyerly WH, Smith DH (1982) Prevalence and disease spectrum in a new focus of visceral leishmaniasis in Kenya. Transactions of the Royal Society of Tropical Medicine and Hygiene 76, 741 746.
  • Hoogstraal J & Heyneman D (1969) Leishmaniasis in the Sudan Republic. 30. Final epidemiologic report. American Journal of Tropical Medicine and Hygiene 18, 1091 1210.
  • Ibrahim ME, Evans DA, Theander TG, El-Hassan AM, Kharazmi A (1995) Diversity among Leishmania isolates from the Sudan: isoenzyme homogeneity of L.donovani versus heterogeneity of L. major. Transactions of the Royal Society of Tropical Medicine and Hygiene 89, 366 369.
  • Ismail A, Kharazmi A, Permin H, El Hassan AM (1997) Detection and characterisation of Leishmania in tissues of patients with post kala-azar dermal leishmaniasis using a specific monoclonal antibody. Transactions of the Royal Society of Tropical Medicine and Hygiene 91, 283 285.
  • Khalil EAG, El-Hassan AM, Zijlstra EE et al. (1998) Treatment of visceral leishmaniasis with sodium stibogluconate in Sudan: management of those who did not respond. Annals of Tropical Medicine and Parasitology 92, 151 158.
  • Khalil EAG, Nur NM, Zijlstra EE, El-Hassan AM, Davidson RN (1996) Failure of a combination of two antifungal drugs, terbinafine plus itraconazole, in Sudanese post kala-azar dermal leishmaniasis. Transactions of the Royal Society of Tropical Medicine and Hygiene 90, 187 188.
  • Kirk R (1938) Primary cutaneous sore in a case of kala-azar. Transactions of the Royal Society of Tropical Medicine and Hygiene 32, 271 272.
  • Kirk R (1947) Studies in leishmaniasis in the Anglo-Egyptian Sudan. VIII. Some observations on the chemotherapy of kala-azar. Transactions of the Royal Society of Tropical Medicine and Hygiene 40, 459 478.
  • Kirk R (1956) Studies in leishmaniasis in the Anglo-Egyptian Sudan. XII. Attempts to find a reservoir host. Transactions of the Royal Society of Tropical Medicine and Hygiene 50, 169 177.
  • Kirk R & Drew CB (1938) Preliminary notes on dermal leishmaniasis in the Anglo-Egyptian Sudan. Transactions of the Royal Society of Tropical Medicine and Hygiene 32, 265 270.
  • Kirk R & Sati MH (1940a) Studies in leishmaniasis in the Anglo-Egyptian Sudan. II. The skin and lymph gland in kala-azar. Transactions of the Royal Society of Tropical Medicine and Hygiene 33, 501 506.
  • Kirk R & Sati MH (1940b) Studies in leishmaniasis in the Anglo-Egyptian Sudan. IV. Punctate rash in treated cases. Transactions of the Royal Society of Tropical Medicine and Hygiene 34, 213 216.
  • Manson-Bahr PEC (1959) East African kala-azar with special reference to the pathology, prophylaxis and treatment. Transactions of the Royal Society of Tropical Medicine and Hygiene 53, 123 137.
  • Marshall WE (1911) Kala-azar commission to investigate the prevalence and cause of the disease in the Eastern Sudan (2) Pathological report. Fourth Report of the Wellcome Tropical Research Laboratory A,157 172.
  • McGregor A (1998) WHO warns of epidemic leishmaniasis. Lancet 351, 575.
  • Mercer A, Seaman J, Sondorp E (1995) Kala azar in eastern Upper Nile Province, southern Sudan. Lancet 345, 187 188.
  • Meredith SEO, Kroon NCM, Sondorp E et al. (1995) Leish-KIT, a stable direct agglutination test based on freeze-dried antigen for serodiagnosis of visceral leishmaniasis. Journal of Clinical Microbiology 33, 1742 1745.
  • Meredith SEO, Zijlstra EE, Schoone GJ et al. (1993) Development and application of the polymerase chain reaction for the detection and identification of Leishmania parasites in clinical material. Archives de l’Institut Pasteur de Tunis 70, 419 431.
  • Minter DM, Wijers DJB, Heisch RB, Manson-Bahr PEC (1962) Phlebotomus martini, a probable vector of kala-azar in Kenya. British Medical Journal ii, 835.
  • Oskam L, Pratlong F, Zijlstra EE et al. (1998) Biochemical and molecular characterization of Leishmania parasites isolated from an endemic focus in eastern Sudan. Transactions of the Royal Society of Tropical Medicine and Hygiene 92, 120 122.
  • Osman OF, Kager PA, Zijlstra EE, El-Hassan AM, Oskam L (1997a) Use of PCR on lymph-node samples as test of cure of visceral leishmaniasis treatment. Annals of Tropical Medicine and Parasitology 91, 845 850.
  • Osman OF, Oskam L, Zijlstra EE et al. (1997b) Evaluation of PCR for diagnosis of visceral leishmaniasis. Journal of Clinical Microbiology 35, 2454 2457.
  • Osman OF, Oskam L, Kroon NCM et al. (1998a) Use of PCR for diagnosis of post-kala-azar dermal leishmaniasis. Journal of Clinical Microbiology 36, 1621 1624.
  • Osman OF, Oskam L, Zijlstra EE, El-Hassan AM, El-Naiem DA, Kager PA (1998b) Use of the polymerase chain reaction to assess the success of visceral leishmaniasis treatment. Transactions of the Royal Society of Tropical Medicine and Hygiene 92, 397 400.
  • Osman OF (1998) Visceral leishmaniasis: the PCR and direct agglutination test for diagnosis and management. PhD Thesis, University of Amsterdam, Amsterdam, The Netherlands.
  • Perea WA, Ancelle T, Moren A, Nagelkerke M, Sondorp E (1991) Visceral leishmaniasis in southern Sudan. Transactions of the Royal Society of Tropical Medicine and Hygiene 85, 48 53.
  • Quate LW (1964) Phlebotomus sandflies of the Paloich Area in the Sudan (Diptera, Psychodidae). Journal of Medical Entomology 1, 213 268.
  • Rohrs LC (1964) Leishmaniasis in the Sudan Republic. XVIII. Parasitemia in kala-azar. American Journal of Tropical Medicine and Hygiene 13, 265 271.
  • Sati MH (1958) Early phases of an outbreak of kala-azar in the Southern Fung. Sudan Medical Journal 1, 98 111.
  • Schorscher JA & Goris M (1992) Incrimination of Phlebotomus (Laroussius) orientalis as a vector of visceral leishmaniasis in western Upper Nile Province, southern Sudan. Transactions of the Royal Society of Tropical Medicine and Hygiene 86, 622 623.
  • Seaman J, Ashford RW, Schorscher J, Dereure J (1992) Visceral leishmaniasis in southern Sudan: status of healthy villagers in epidemic conditions. Annals of Tropical Medicine and Parasitology 86, 481 486.
  • Seaman J, Boer C, Wilkinson R et al. (1995) Liposomal amphotericin B (Ambisome) in the treatment of complicated kala-azar under field conditions. Clinical Infectious Diseases 21, 188 193.
  • Seaman J, Mercer AJ, Sondorp E (1996) The epidemic of visceral leishmaniasis in Western Upper Nile, southern Sudan: course and impact from 1984 to 1994. International Journal of Epidemiology 25, 862 871.
  • Seaman J, Mercer AJ, Sondorp HE, Herwaldt BL (1997) Epidemic visceral leishmaniasis in southern Sudan: treatment of severely debilitated patients under wartime conditions and with limited resources. Annals of Internal Medicine 124, 664 672.
  • Seaman J, Pryce D, Sondorp HE, Moody A, Bryceson AD, Davidson RN (1993) Epidemic visceral leishmaniasis in Sudan: a randomized trial of aminosidine plus sodium stibogluconate versus sodium stibogluconate alone. Journal of Infectious Diseases 168, 715 720.
  • Siddig AM, Gaafar A, Ghalib HW, Grayson J, Petersen E, Khidir S (1989) Kala-azar in the Sudan: clinical and immunological manifestations. Sudan Medical Journal 27, 26 36.
  • Siddig M, Ghalib HW, Shillington DC, Petersen EA (1988) Visceral leishmaniasis in the Sudan: comparative parasitological methods of diagnosis. Transactions of the Royal Society of Tropical Medicine and Hygiene 82, 66 68.
  • Siddig M, Ghalib HW, Shillington DC, Petersen EA, Khidir S (1990) Visceral leishmaniasis in Sudan. Clinical features. Tropical and Geographical Medicine 42, 107 112.
  • Stephenson RW (1940) An epidemic of kala-azar in the Upper Nile province of the Anglo-Egyptian Sudan. Annals of Tropical Medicine and Parasitology 34, 175 179.
  • Van Peenen PFD & Reid TP (1962) Leishmaniasis in the Sudan republic. VI. Clinical and laboratory aspects of kala-azar in hospitalized patients from Upper Nile province. American Journal of Tropical Medicine and Hygiene 11, 723 730.
  • Veeken H et al. (2000) A randomised comparison of branded and generic sodium stibogluconate for the treatment of visceral leishmaniasis under field conditions in Sudan. Tropical Medicine and International Health 5, 312 317.
  • World Health Organization (1990) Control of leishmaniasis. Report of a WHO expert committee. WHO Technical Report Series 793. WHO, Geneva.
  • Zeese W & Frank W (1987) Present epidemiological situation of kala-azar in the Republic of Sudan. Zentralblatt für Bakteriologie, Mikrobiologie und Hygiene – Series A, Medical Microbiology, Infectious Diseases, Virology, Parasitology 264, 414 421.
  • Zijlstra EE, Ali MS, El-Hassan AM et al. (1991a) Kala-azar in displaced people from southern Sudan: epidemiological, clinical and therapeutic findings. Transactions of the Royal Society of Tropical Medicine and Hygiene 85, 365 369.
  • Zijlstra EE & El-Hassan AM (1993) Leishmanin and tuberculin sensitivity in leishmaniasis in the Sudan, with special reference to kala-azar. Transactions of the Royal Society of Tropical Medicine and Hygiene 87, 425 427.
  • Zijlstra EE, El-Hassan AM, Ismael A (1995) Endemic kala-azar in eastern Sudan: post-kala-azar dermal leishmaniasis. American Journal of Tropical Medicine and Hygiene 52, 299 305.
  • Zijlstra EE, El-Hassan AM, Ismael A, Ghalib HW (1994) Endemic kala-azar in eastern Sudan: a longitudinal study on the incidence of clinical and subclinical infection and post-kala-azar dermal leishmaniasis. American Journal of Tropical Medicine and Hygiene 51, 826 836.
  • Zijlstra EE, Osman OF, Hofland HWC et al. (1997) The direct agglutination test for diagnosis of visceral leishmaniasis under field conditions in Sudan: comparison of aqueous and freeze-dried antigens. Transactions of the Royal Society of Tropical Medicine and Hygiene 91, 671 673.
  • Zijlstra EE, Siddig Ali M, El-Hassan AM et al. (1991b) Direct agglutination test for diagnosis and sero-epidemiological survey of kala-azar in the Sudan. Transactions of the Royal Society of Tropical Medicine and Hygiene 85, 474 476.
  • Zijlstra EE, Siddig Ali M, El-Hassan AM et al. (1992) Kala-azar: a comparative study of parasitological methods and the direct agglutination test in diagnosis. Transactions of the Royal Society of Tropical Medicine and Hygiene 86, 505 507.
  • Zijlstra EE, Siddig Ali M, El-Hassan AM et al. (1993) The treatment of kala-azar in the Sudan with sodium stibogluconate: a randomized trial of three dosage regimens. Transactions of the Royal Society of Tropical Medicine and Hygiene 87, 307 309.