[ effect of age group under 15 years on cholera morbidity during the past 10 years in Iran [1996-2005]]

The study of the effect of age, especially children under 15 years, on cholera morbidity during a period often years [1996-2005] was carried out in Iran. There are no other studies on this topic in Iran and other countries. In this cross sectional study, we used cholera surveillance data collected in Center for Disease Control. All cholera cases were divided into two groups: under 15 years and above 15 years. Incidence rate of cholera per 100000 was calculated in total population and the two mentioned groups during 10 years. The relative risk of less than 15 year-olds group to above 15 year-olds was calculated with95% CI for 10 years by EPI6 and SPSS software. The trend of cholera incidence during the past 10 years shows two epidemic peaks in 1998 and 2005 by the rate of 15.7 and 1.63 per 100000, respectively. During the year with no epidemic and the years between two peaks, the age group under 15 year-olds was more affected with significant relative risk. For example, in 2001 this rate was 4.53. So, we can consider this age group as a risk factor to cholera morbidity. The age group of above 15 year-olds was more affected to cholera during epidemic years [1998, 2005] and relative risk was less than one. So, the age was protective on cholera morbidity for children in these years. One of the most important causes of periodic cholera epidemics every 5-6 years is changing of herd immunity. During the years between two epidemics adults have sufficient immunity and children are more affected because of first exposure and less immunity. With reduced herd immunity epidemics occur. We recommend continuing and strengthening of cholera surveillance system for detection of epidemics and treatment of highly sensitive age groups

Enfermedades emergentes y reemergentes: un reto de nunca acabar: segunda parte / Emergent and re-emergent diseases: a never-ending challenge

El presente artículo muestra cómo la humanidad se enfrenta a nuevos agentes patógenos (emergentes) y a otros, ya conocidos, pero que en los últimos años han aumentado su mortalidad (reemergentes). Hasta dónde la “mano del hombre” es responsable de éste fenómeno?La segunda parte pretende analizar los diferentes factores, sociales, políticos, morales y económicos, que incidieron para que el S.I.D.A apareciera, no como epidemia, sino como pandemia y cómo los intereses económicos primaron sobre las políticas de salud, al precio de millones de vidas.

Comparative stuy for LPS Extraction of NAG vibrio cholerae by EDTA, heating method and hot phenol method

Vibrio cholerae [NAG] was isolated from patients with diarrhea, identification by microbiological, biochemical and serological techniques, then Lip polysaccharide was extract from Vibrio cholerae [NAG][31G, 11G, 24G, 13G] by phenol and EDTA-heating method for comparison, The extracts were purified by Sepharose-4B gel. The results showed that EDTA-heating method was efficient and less expensive of time and material.

Detection of faecal leucocytes & erythrocytes from stools of cholera patients suggesting an evidence of an inflammatory response in cholera.

BACKGROUND & OBJECTIVES: Detection of faecal leucocytes and RBCs in stool samples of cholera patients has been reported in a small number of studies. This study extends these observations by examining stool samples of cholera patients in Calcutta. METHODS: Out of 1562 diarrhoeal stool samples, Vibrio cholerae was isolated in 266 cases. Stool samples obtained were examined microscopically within two hours of collection. RBCs and faecal leucocytes were examined by normal saline and methylene blue stain. Stool culture was performed using selective and differential media for isolation of V. cholerae. RESULTS: Among 266 cholera patients, RBCs was detected in 58 per cent and faecal leucocytes in 88 per cent respectively. The extent of the changes correlated with clinical severity. INTERPRETATION & CONCLUSION: This study showed the presence of RBCs and faecal leucocytes in stools of patients of cholera caused by V. cholerae 01 and 0139 which indicates some inflammatory changes in the gut mucosa. Further study is required to elucidate the inflammatory mechanism involved in the underlying process(es).

El cólera, una enfermedad impredecible / Cholera, an unpredictable disease

Aun cuando la mortalidad por cólera ha declinado debido a un tratamiento apropiado, el desplazamiento de esa enfermedad es ahora más intenso que lo que fue a principios del siglo. La esperanza la protección por medio de una vacuna se han visto afectadas por la habilidad del cólera para cambiar su epidemiología. Los programas para el control de afecciones diarreicas han de continuar estimulando la prevención de esas enfermedades por medio de la educación de la comunidad e intervenciones en el campo de la higiene, ya que no hay solución "mágica" inminente o en perspectiva. Estudios de la epidemiología y del comportamiento se requieren aún para entender mejor aquellos factores que puedan continuar iniciando cambios impredecibles en el curso de esta enfermedad y en su distribución epidémica.

Vacunas contra el cólera / Vaccines against cholera

El cólera es una enfermedad aguda e infecciosa que fue descrita antes de la época de Hipócrates en el siglo V AC. Se describieron varias epidemias de esta enfermedad en Asia entre los siglos XV y XVIII. A mediados del siglo XIX John Snow en Inglaterra fue el primero en describir las medidas de prevención de la enfermedad a raíz de una epidemia ocurrida en Londres. En 1883, Robert Koch realizó el descubrimiento del agente causal, Vibrio cholerae, un bacilo curvo de gran movilidad. Durante los siglos XIX y XX han ocurrido siete pandemias de cólera; en la actualidad ocurre la transmisión de la séptima. El cólera es una de las causas más importantes de morbilidad y mortalidad de algunos países de Asia y Africa y desde 1991 también en Latinoamérica. Desde principios del siglo se ha empleado una vacuna parenteral elaborada con una cepa de V. cholerae 01, inactivada con calor, la cual únicamente induce 50 por ciento de protección en jóvenes y adultos, durante un período de aproximadamente 6 meses. El empleo de adyuvantes no ha tenido influencia en su eficiencia, sino por el contrario incrementa las reacciones colaterales. Las perspectivas para el desarrollo de una vacuna eficaz contra el cólera se basan en el hecho de que más del 90 por ciento de los sujetos infectados en forma natural quedan protegidos para una segunda reinfección. El avance del desarrollo de las vacunas del cólera se ha podido efectuar gracias a un mejor conocimiento de los mecanismos de patogenicidad y antigenicidad del agente etiológico, aunque persisten incógnitas importantes. La vacuna ideal contra el cólera debería ser tan eficaz como la infección natural, sin riesgo de causar enfermedad infecciosa, de fácil administración, de bajo costo, de una sola dosis, inocua, que proteja contra la infección y obviamente contra la enfermedad grave, con protección de larga duración y probablemente de administración oral

A toxoid prepared from cholera toxin by iodination

A cholera toxoid was prepared by iodinating purified cholera toxin having an activity of 25 Limit of blueing (Lb) doses/l ug with 0.8 umol of iodine monochloride per mg toxin, and the residual lesion capacity was tested in mice. The Blueing Dose (BD) test was strongly positive for the native toxin, and co0mpletely abolished in the iodinated toxoid when tested at up to 25 times one Lb dose. The dermal microscopic lesions with intradermal doses of 1 ug virulent toxin presented intense leucocyte infiltration, proteinaceous edema and active hypertemia, whereas none of these effects was observed with the same amount of toxoid. To determine antigenicity, two groups of micereceived toxin or toxoid, 8.5 ug adsorbed to aluminum hydroxide, followed by a booster of 17 ug in saline 21 days later. Measurement of antibodies by ELISA at day 28 indicated that the toxoid was 2.5 times more antigenic than the toxin. These data show iodination converts cholera toxin to an effective toxoid

Immunogenicity of liposome-associated oral cholera vaccine prepared from combined Vibrio cholerae antigens.

Liposomes were prepared from bovine brain sphingomyelin and cholesterol. They were reinforced by incorporation of osmium tetroxide to prevent their immediate degradation inside the host. Combined Vibrio cholerae antigens (lipopolysaccharide, crude cell-bound hemagglutinin and procholeragenoid) were orally administered to experimental rats either as free or liposome-associated. A total of 70 experimental rats was utilized in experiments comparing the immune responses of rats to liposome-associated vaccine, free vaccine, liposomes, or placebo, and to vaccines where the lipid or antigen levels were reduced. Immediately after feeding with sodium bicarbonate to lower the gastric acidity, they were fed either cholera vaccines or placebo. Results from serum ELISA revealed that the liposomes localized the immune response to the intestinal mucosa. They displayed an adjuvant property in terms of evoking a higher immune response to V. cholerae antigens, as measured by the appearance of specific antibody-producing cells in the intestinal mucosa, than when the antigens were fed alone. The adjuvanticity was found to be lipid dose dependent. Liposomes prepared with high lipid content enhanced immunogenicity of the admixture antigens to a greater degree.

Oral vaccine against cholera prepared from Vibrio cholerae antigen(s).

Albino rats aged 7-8 weeks old purchased from the National Laboratory Animal Centre, Salaya, Nakhon Pathom, were found to be a good animal model for the study on immunogenicity of V. cholerae antigens. Seventy-two rats were fasted for 15 hours before feeding each one with 1 ml of 5% NaHCO3 to reduce gastric acidity prior to immunization. They were divided into 9 groups of 8 rats and immunized orally with 2 ml, each, of the V. cholerae antigens dissolved or suspended in Cassamino acid as follows: group 1 (control): Cassamino acid (Ca) alone; group 2 (control): 2.5% formalinized sheep red blood cells (F-SRBC); group 3: 1,000 micrograms of lipopolysaccharide (LPS); group 4: 100 micrograms of procholeragenoid (P); group 5: 80 haemagglutinating units of cell-bound haemagglutinin (CHA) adsorbed onto the surface of F-SRBC (CH-SRBC); group 6: 500 micrograms of LPS + 50 micrograms of P; group 7: CH-SRBC + 50 micrograms of P; group 8: combined vaccine formula 1 consisted of 500 micrograms of LPS, CH-SRBC and 50 micrograms of P and group 9: combined vaccine formula 2 consisted of 1,000 micrograms of LPS, CH-SRBC and 100 micrograms of P. The immunization was repeated once more 14 days later. Five days, thereafter, the rats were killed and their jejuni were removed for cryostat sectioning. Antibody producing cells against LPS (anti-LPS cells), P (anti-CT cells) and CHA (anti-CHA cells) in the intestinal lamina propria were enumerated by double antibody sandwich method of immunofluorescence using pure LPS, cholera toxin (CT) and pure CHA as the antigens in the assay, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibodies against Vibrio cholerae lipopolysaccharide, cell-bound haemagglutinin and toxin in the intestinal fluid during convalescence.

Specific antibodies to V. cholerae lipopolysaccharide (LPS), cell-bound haemagglutinin (CHA) and toxin (CT) in the intestinal lavages of healthy Thais and Thai cholera patients during the convalescence period were determined by enzyme-linked immunosorbent assay. Only IgM and IgA specific antibodies were detectable in the specimens. All of the persons who were just recovered from cholera had IgA anti-CT and IgA anti-LPS and 82.4% had IgA anti-CHA. The IgA anti-CT, anti-LPS and anti-CHA were detected also in the gut fluids of 70.6%, 94.1% and 88.2%, respectively, of the healthy controls. The mean levels of the IgA antibodies of all specificities between the two groups of individuals were not different. However, the IgM anti-CT and IgM anti-LPS of the cholera patients increased during the convalescence period. The levels, therefore, were significantly higher than those of the controls. The ratios of IgA anti-CT: IgM anti-CT and IgA anti-LPS: IgM anti-LPS among the patients were 2.93:1 and 2.02:1, respectively while those of the controls were 10:1 and 34:1, respectively. IgA antibodies predominated in the lavages of both groups of the individuals.

Cell-bound haemagglutinin (CHA) of V. cholerae 01 as protective antigen.

The study of immunogenicity of cell-bound haemagglutinin (CHA) of Vibrio cholerae E1 Tor in mice revealed that the CHA was a good antigen when it was adsorbed onto the surface of sheep red blood cells and given orally to mice. The antigen not only induced high levels of various class antibodies which sustained in the intestinal tracts for a long period of time (longer than 6 months) but also the antibodies were protective against homologous cholera challenge. The degree of protection seems to correlate with the level of IgA in the intestinal washing. The protective ability was conferred mainly by anti-CHA.

Protection against Vibrio cholerae infection afforded by fragments of anti-haemagglutinin.

The finding that Fab fragments of the anti-E1 Tor haemagglutinin were able to afford protection in vivo (low but significant), as well as a significant reduction in Vibrio cholerae adherence to isolated intestinal epithelial cells in-vitro, implicate that masking of these cell-bound haemagglutinin sites per se, would be sufficient to confer protection in E1 Tor cholera infection. Subsequently, the related working hypothesis that the E1 Tor cell-bound haemagglutinin is playing an adhesive role is validated. In natural immunity, it could be envisaged that antiserum to this cell-bound haemagglutinin of V. cholerae E1 Tor would be highly protective due to the synergistic effects of the dual protective mechanisms in operation at the intestinal sites viz. a masking and agglutinating phenomenon.

Antibody responses in cholera patients.

Haemagglutinating, vibriocidal and mouse protective antibody responses in cholera patients were found to be maximum on the 7th day of admission. The mouse protective antibody on the first day at the hospital was lower than those of human volunteers. The circulating antibodies in the patients declined to normal levels or lower than normal before 3 months after the acute onset.

Protection afforded by anti-hemolysin against V. cholerae El Tor infection in experimental cholera.

Specific antisera to V. cholerae El Tor hemolysin were prepared. The sera exhibited the following characteristics: formed a single precipitin band in immunoelectrophoresis against the crude preparation of hemolysin, had no passive hemagglutinating antibodies against V. cholerae LPS sensitized cells, possessed neutralizing property to the homologous hemolysin, and afforded some small degree of protection to oral challenge of V. cholerae El Tor in experimental animals.