Post-kala-azar dermal leishmaniasis (PKDL) occurs after kala-azar treatment and acts as a durable infection reservoir. On the basis of active case finding among 22,699 respondents, 813 (3.6%) had had kala-azar since 2002, of whom 79 (9.7%) developed PKDL. Eight additional patients with PKDL had no history of kala-azar. Annual kala-azar incidence peaked at 85 cases per 10,000 person-years in 2004 and fell to 46 cases per 10,000 person-years in 2007, but PKDL incidence rose from 1 case per 10,000 person-years in 2002-2004 to 21 cases per 10,000 person-years in 2007. The rising PKDL incidence threatens the regional visceral leishmaniasis elimination initiative and underscores the urgent need for more effective PKDL diagnosis and treatment.

Abstract. We conducted active surveillance for kala-azar and post-kala-azar dermal leishmaniasis (PKDL) in a population of 24,814 individuals. Between 2002 and 2010, 1,002 kala-azar and 185 PKDL cases occurred. Median PKDL patient age was 12 years; 9% had no antecedent kala-azar. Cases per 10,000 person-years peaked at 90 for kala-azar (2005) and 28 for PKDL (2007). Cumulative PKDL incidence among kala-azar patients was 17% by 5 years. Kala-azar patients younger than 15 years were more likely than older patients to develop PKDL; no other risk factors were identified. The most common lesions were hypopigmented macules. Of 98 untreated PKDL patients, 48 (49%) patients had resolution, with median time of 19 months. Kala-azar patients showed elevated interferon-γ (IFNγ), tumor necrosis factor-α (TNFα), and interleukin 10 (IL-10). Matrix metalloproteinase 9 (MMP9) and MMP9/tissue inhibitor of matrix metalloproteinase-1 (TIMP1) ratio were significantly higher in PKDL patients than in other groups. PKDL is frequent in Bangladesh and poses a challenge to the current visceral leishmaniasis elimination initiative in the Indian subcontinent.

The El Tor biotype of Vibrio cholerae O1, causing the current seventh pandemic of cholera, has replaced the classical biotype, which caused the sixth pandemic. The CTX prophages encoding cholera toxin in the two biotypes have distinct repressor (rstR) genes. Recently, new variants of El Tor strains that carry the classical type (CTX class ) prophage have emerged. These ''hybrid'' strains apparently originate through lateral gene transfer and recombination events. To explore possible donors of the CTX class prophage and its mode of transfer, we tested environmental V. cholerae isolates for the presence of CTX class prophage and mobility of the phage genome. Of the 272 environmental V. cholerae isolates tested, 6 were found to carry the CTX class prophage; all of these belonged to the O141 serogroup. These O141 strains were unable to produce infectious CTX class phage or to transmit the prophage to recipient strains in the mouse model of infection; however, the CTX class prophage was acquired by El Tor strains when cultured with the O141 strains in microcosms composed of filtered environmental water, a chitin substrate, and a V. cholerae O141-specific bacteriophage. The CTX class prophage either coexisted with or replaced the resident CTX ET prophage, resulting in El Tor strains with CTX genotypes similar to those of the naturally occurring hybrid strains. Our results support a model involving phages and natural chitin substrate in the emergence of new variants of pathogenic V. cholerae. Furthermore, the O141 strains apparently represent an alternative reservoir of the CTX class phage genome, because the classical V. cholerae O1 strains are possibly extinct.hybrid Vibrio cholerae strain ͉ toxigenic Vibrio cholerae C holera caused by toxigenic Vibrio cholerae is a major public health problem confronting many developing countries, in which outbreaks occur frequently and are closely associated with poverty and poor sanitation (1, 2). Seven distinct pandemics of cholera have been recorded since the first pandemic in 1817. The current seventh pandemic, which originated in Indonesia in 1961, is the most extensive in terms of geographic spread and duration. The causative agent is V. cholerae O1 of the El Tor biotype. The sixth pandemic and presumably the earlier pandemics were caused by V. cholerae O1 of the classical biotype (2).Classification into biotypes is based on a set of phenotypic traits that include susceptibility to polymixin B, hemagglutination of chicken erythrocytes, hemolysis of sheep erythrocytes, the Voges-Proskauer test (which measures the production of acetylmethylcarbinol), and susceptibility to phages (1, 2). In toxigenic V. cholerae, the genes encoding cholera toxin (ctxAB) are located in the CTX prophage (3). Although most other parts of the CTX phage genomes are similar in the two biotypes of V. cholerae O1, the repressor genes (rstR genes) carried by CTX phages differ in CTX ET and CTX class (4,5). Two other varieties of the rstR gene carried by CTX Calc and CTX env also have been reported (6, 7...

Seasonal epidemics of cholera in Bangladesh are self-limited in nature, presumably due to phage predation of the causative Vibrio cholerae during the late stage of an epidemic, when cholera patients excrete large quantities of phage in their stools. To further understand the mechanisms involved, we studied the effect of phage on the infectivity and survival of V. cholerae shed in stools. The 50% infectious dose of stool vibrios in infant mice was ϳ10-fold higher when the stools contained a phage (1.8 ؋ 10 3 to 5.7 ؋ 10 6 PFU/ml) than when stools did not contain a detectable phage. In competition assays in mice using a reference strain and phage-negative cholera stools, the infectivity of biofilm-like clumped cells was 3.9-to 115.9-fold higher than that of the corresponding planktonic cells. However, the difference in infectivity of these two cell populations in phage-positive stools was significantly less than that in phage-negative stools (P ‫؍‬ 0.0006). Coculture of a phage and V. cholerae or dilutions of phage-positive cholera stools in nutrient medium, but not in environmental water, caused rapid emergence of phage-resistant derivatives of the bacteria, and these derivatives lost their O1 antigen. In cholera stools and in intestinal contents of mice prechallenged with a mixture of V. cholerae and phage, the bacteria remained completely phage susceptible, suggesting that the intestinal environment did not favor the emergence of phage-resistant derivatives that lost the O1 antigen. Our results indicate that phages lead to the collapse of epidemics by modulating the required infectious dose of the bacteria. Furthermore, the dominance of phage-resistant variants due to the bactericidal selective mechanism occurs rarely in natural settings, and the emerging variants are thus unable to sustain the ongoing epidemic.

We assessed the relationship between chronic arsenic exposure through drinking water with respiratory complications and humoral immune response by measuring serum immunoglobulin profiles in the affected subjects (arsenicosis patients) living in the arsenic endemic rural villages of Bangladesh. The duration of exposure was determined through detailed history of the patients (n=125) and the levels of arsenic in the drinking water and urine samples were determined. The mean duration of exposure in the patients was 7.4+/-5.3 y, and the levels of arsenic in the drinking water and urine samples were 216+/-211 and 223+/-302 micro g/L, respectively, compared to 11+/-20 and 29+/-19 microg/L, respectively, in the unexposed subjects. There was high prevalence of respiratory complications like breathing problems including chest sound, asthma, bronchitis and cough associated with drinking water arsenic toxicity. Arsenicosis patients had significantly elevated levels of IgG (P<0.001) and IgE (P<0.001) while the levels of IgA were also significantly higher (P<0.005) but IgM were similar to that of the control subjects. Analysis of the clinical symptoms based on skin manifestations showed the levels of both IgG and IgE were significantly elevated during the initial stages while IgE were further elevated with the duration of arsenic exposure. Arsenicosis patients with respiratory complications had mean serum IgE levels of 706+/-211 IU/mL compared to 542+/-241 IU/mL in patients without apparent involvement with the respiratory system (P<0.01). The eosinophil counts in the patients did not differ significantly from the unexposed subjects indicating that elevated levels of serum IgE might not be due to allergic diseases, rather it could be due to direct effects of arsenic. We found significant linear relationships between the levels of serum IgE and inorganic phosphorus (P<0.05), and serum IgA levels with urinary excretion of arsenic (P<0.001). These observations suggested that arsenic toxicity caused respiratory complications, induced changes in the humoral as well as mucosal immune responses.