Exome Sequencing Identifies Two Variants of the Alkylglycerol Monooxygenase Gene as a Cause of Relapses in Visceral Leishmaniasis in Children, in Sudan.

Background: Visceral leishmaniasis (kala-azar, KA) is the most severe form of leishmaniasis, characterized by fever, weight loss, hepatosplenomegaly, and lymphadenopathy. During an outbreak of KA in Babar El Fugara (Sudan), 5.7% of cured patients displayed relapses, with familial clustering in half the cases. Methods: We performed whole-exome sequencing on 10 relapsing individuals and 11 controls from 5 nuclear families. Results: Rare homozygous and compound-heterozygous nonsense (c.1213C > T, rs139309795, p.Arg405*) and missense (c.701A > G, rs143439626, p.Lys234Arg) mutations of the alkylglycerol monooxygenase (AGMO) gene were associated with KA relapse in 3 families. Sequencing in additional family members confirmed the segregation of these mutations with relapse and revealed an autosomal dominant mode of transmission. These mutations were detected heterozygous in 2 subjects among 100 unrelated individuals with KA who never relapsed after cure, suggesting incomplete penetrance of AGMO deficiency. AGMO is expressed in hematopoietic cells, and is strongly expressed in the liver. AGMO modulates PAF production by mouse macrophages, suggesting that it may act through the PAF/PAF receptor pathway previously shown to have anti-Leishmania activity. Conclusions: This is the first demonstration that relapses after a first episode of KA are due to differences in human genetic susceptibility and not to modifications of parasite pathogenicity.

Epidemiology of visceral leishmaniasis in Atbara River area, eastern Sudan: the outbreak of Barbar El Fugara village (1996-1997).

An outbreak of visceral leishmaniasis (VL) started in 1995 in the Atbara River area in eastern Sudan. This article reports on this outbreak and on the clinical and immunological studies that were carried out in a village, with the highest incidence of VL cases, from 1996 to 1997. A significant increase in VL incidence was recorded in a dozen villages in this area; one village, Barbar El Fugara accounted for half of the total number of cases recorded at the regional hospital. A total of 152 VL and 61 post kala-azar dermal lesion (PKDL) cases were diagnosed and treated in Barbar. Household (n = 671) and school (n = 276) surveys were performed using the leishmanin skin test (LST) and the direct agglutination test (DAT). LST positivity was 23.1 and 15.7%, whereas DAT positivity was 8.9 and 26.4% in both surveys, respectively. No gender differences were observed in either test. Unlike DAT, LST positivity was predominant in the higher age groups that also exhibited lower prevalence of VL. Few individuals were positive by both tests (1.3%, 5.2%) while the majority (68.8%, 64.8%) had no evidence of acquired immune response, suggesting either a role of innate immunity in preventing parasite establishment or, unexpectedly, lack of exposure to Leishmania. Subclinical parasitism was also demonstrated, as evidence of both acquired humoral and cellular immune responses was observed in individuals with no past history of the disease. The wide spectrum of L. donovani/human interactions may be explained by differential exposure to environmental risk factors, parasite strain polymorphisms or host genetic makeup.

The interplay between environmental and host factors during an outbreak of visceral leishmaniasis in eastern Sudan.

Parasitic diseases, including human visceral leishmaniasis, are multifactorial. Factors that are expected to play an important role in the parasite-human interaction are exposure, parasite "virulence" and host resistance factors. In populations exposed to Leishmania donovani most subjects do not allow the parasites to establish themselves or remain asymptomatic. Some individuals, however, fail to control parasite expansion and dissemination and develop a visceral disease. We report here the results of a longitudinal survey whose aims were to identify risk factors underlying visceral leishmaniasis (VL) susceptibility during an outbreak that occurred in a Sudanese village between 1995 and 1999. Most of the 660 subjects (90%) living in the central district were exposed to Leishmania and 20.9% (n = 138), mostly teenagers, developed VL. VL cases increased markedly in adults late in the outbreak, suggesting some changes in adult resistance status or in Leishmania "virulence" during the epidemic. Age and ethnic origin of the patients were the most important critical risk factors to account for the distribution of the VL cases that were recorded during the whole epidemic. This and the high frequency of VL in certain families suggest that host genetic factors played an important role in shaping the outbreak in this village. However, environmental factors (the presence of cows and neems in the households) that increase/decrease exposure to the parasite had significant effects on the distribution of VL cases in the village in the first phase of the outbreak.

Visceral leishmaniasis in eastern Sudan: parasite identification in humans and dogs; host-parasite relationships.

In 1996, an epidemic outbreak of visceral leishmaniasis (VL) started in Barbar el Fugara, a village in Gedarif State (eastern Sudan). From 1997 to 2000, regular epidemiological studies were carried out in the human population, as well as in mammals and sand flies. In symptomatic patients, 46/69 lymph node, 6/20 post kala-azar dermal leishmaniasis (PKDL) and 1/4 cutaneous cultures in NNN medium were positive. In 69 dogs, 23/79 lymph node cultures were positive. In other mammals (47 rodents, five donkeys, one mongoose and one monkey) spleen and/or blood cultures were negative. Characterization of isolated strains (by starch gel electrophoresis and isoelectrofocusing) identified three zymodemes of Leishmania donovani, two of L. infantum and two of L. archibaldi complexes from patient samples and three zymodemes of L. donovani, three of L. infantum and two of L. archibaldi complexes from dog samples. Five of them were present in both man and dog. For the first time, a strain from a PKDL case was identified as L. infantum, and a child had the same L. infantum zymodeme in VL and in subsequent PKDL. Blood samples from dogs were studied by immunofluorescent antibody test (IFAT). The seroprevalence in dogs was 72.5%, 74.3% and 42.9% in 1998, 1999 and 2000, respectively. By using CDC miniature light traps 12 745 sand flies were collected and then identified. Phlebotomus papatasi (7%) and P. orientalis (5%) were sympatric, mainly inside homes (85% and 75%, respectively). These results, the relative stability of seroprevalence in dogs and the intradomiciliar presence of P. orientalis, known as a vector of VL in Sudan, suggest several hypotheses: (i) man is responsible for the disease in dogs, (ii) the dog is the reservoir of VL, (iii) the dog is an intermediate host between a possible sylvatic cycle and the anthroponotic cycle. More extensive studies are needed to assess the transmission cycle of VL in this area of Sudan.