An immunoglobulin G enzyme-linked immunosorbent assay (IgG-ELISA) for the detection of dengue antibodies is described and compared to the haemagglutination inhibition test (HI). The sensitivity, specificity and agreement rate between the 2 techniques were good. The coefficients of correlation between IgG-ELISA and HI results, using dengue 1-4 antigens, were highly significant (P less than 0.001 for either antigen). IgG-ELISA was rapid, and easy to perform and suitable for large-scale studies. Between April and June 1987, a baseline serosurvey of the prevalence of dengue antibodies in age-stratified samples of children was carried out in Tahiti using IgG-ELISA. 327 children were tested against each dengue serotype. There was no significant difference between sex. Overall rates ranged from 7.4% in children under 5 years to 83.1% in those aged 15-19 years. Dengue 4 being the only serotype involved since 1979, specific responses to dengue 4 were found in higher proportion among children under 8 years old, while the IgG-ELISA responses were more widely reactive among children aged above 8 years (P less than 0.001). The acquisition rate of dengue 4 antibodies was 2.95% on average per year in children under 8 years of age.

Age Factors↗

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Finger-prick blood collection and computer-assisted enzyme-linked immunosorbent assay for large-scale serological studies on leprosy.

An immunoglobulin M anti-phenolic glycolipid 1 assay was standardized and optimized using specimens of dried blood collected on commercial precut filter paper discs, followed by a computer-assisted enzyme-linked immunosorbent assay (ELISA). The correlation between venepuncture and finger-prick methods, the calibration of the quantity of absorbed blood, and the reproducibility of the ELISA test were excellent. A slight decline of activity was observed when the samples were stored for 3 months at +4 degrees C. Skimmed milk can be used as diluent instead of bovine serum albumin, contributing to lessening the cost of the test. Using the method described, as many as 300 samples can be collected in the field and 480 ELISAs per day can be run in the central laboratory by one trained person.

Antigens, Bacterial↗

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Prevalence of hepatitis B virus infection in the Austral archipelago, French Polynesia: identification of transmission patterns for the formulation of immunization strategies.

A sero-epidemiological survey of hepatitis B virus (HBV) infection in a randomly selected sample of 957 persons from the population of the Austral Island group in French Polynesia was conducted as a first step before developing an immunization programme strategy. Prevalence rates of HBsAg ranged from 3.09% to 27% in the different islands of the group with a weighted mean of 10.48%, while the prevalence rate for at least one marker ranged from 46.91% to 81.03% with a weighted mean of 64.12%. In the 0-11 months and 1-4 years age groups, 2.08% and 10.57%, respectively, of the children were HBsAg carriers. These findings, when compared to the mean population carrier rate of 10.48%, suggest that HBV transmission occurred mostly after the first year of life. The highest prevalence rate for HBeAg positivity was in the 5-19 years age group (more than 40% of the HBsAg carriers were HBeAg positive), suggesting that contagiousness was greatest in childhood and adolescence. HBsAg was found in 11.45% of women of child-bearing age and HBeAg in 19.09% of women positive for HBsAg. It is concluded that immunization of newborns and infants, using vaccine alone, should be the most effective strategy for reducing HBV infection in the Austral Islands archipelago.

Age Factors↗

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Duration of immunoglobulin M antibodies against Rift Valley fever virus in cattle after natural infection.

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Animals↗

PubMedDate not supplied

First fatal human case of Rift Valley fever in Madagascar.

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Adult↗

PubMedDate not supplied

Dengue 1 epidemic in French Polynesia, 1988-1989: surveillance and clinical, epidemiological, virological and serological findings in 1752 documented clinical cases.

An epidemic of dengue 1 occurred in French Polynesia in December 1988 and June 1989. This paper records (i) the trend of the outbreak and its surveillance and (ii) the clinical, epidemiological and virological data obtained from 1752 documented cases. The epidemic reached its peak in February in Tahiti Island, 7 weeks after its recognition. Among 6034 suspect cases reported by sentinel physicians, 60.3% were < 20 years old. The illness was classical dengue. No fatality or case of dengue haemorrhagic fever/dengue with shock syndrome was reported. Of 4792 patients subjected to laboratory testing, 41% were confirmed as positive. The serological attack rate was c. 40%. The estimated number of dengue infections in the Windward Islands was about 20,000. Transmission was associated with Aedes aegypti. Study of documented cases showed a higher confirmation rate in both the civilian population < 15 years old (46.5%) and the susceptible French military population (47.6%) than in older civilians (31.1%, P < 0.05). Furthermore, primary dengue infections were predominant in both of the first 2 groups. The diagnosis was mostly confirmed (i) by virus isolation on day < 5 of illness and (ii) by detection of immunoglobulin (Ig) M on day > or = 5 of illness. The study showed that adequate surveillance of an epidemic requires both clinically and laboratory-based systems.

Dengue↗

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Ultrasonographical assessment of morbidity in schistosomiasis mansoni in Madagascar: a community-based study in a rural population.

Between June and November 1993, a parasitological, clinical and ultrasonographical survey was carried out in the mid west of Madagascar, among the whole population of a village where Schistosoma mansoni was endemic. S. mansoni eggs were found in the stools of 61.8% of the 544 individuals examined; the highest prevalence of infection (85.7%) was observed in the 15-19 years old age group. The most intense infections were recorded in the 10-14 years age group, in which the geometric mean egg count was 265 eggs/g of faeces and 34.3% of the individuals excreted more than 400 eggs/g. The egg count decreased steadily from the age of 15 years. Ultrasonographical examination was performed in 482 inhabitants older than 2 years: 29% of them presented definite schistosome associated liver alterations according to the proposals for staging S. mansoni infection made by the World Health Organization Cairo working group. Stage 3 was never observed in subjects under 30 years old. This is consistent with the need for a long-standing infection before serious lesions occur. A significant relationship between egg count and degree of liver alterations was found only in the 20-29 years age group.

Adolescent↗

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[Determination of biovars of Brucella melitensis by manometric character: epidemiological value and relation to serovars].

As Brucella melitensis is the most frequently encountered Brucella species in human medicine, and as its subdivision into three serovars is insufficient for epidemiological studies, we sought to define a new scheme for biotyping of this species. For this purpose, we studied 94 strains for their oxidative metabolic rates on 32 substrates and their susceptibility to ten antibiotics, and 132 strains for their activities with three enzymes. A taxonomic study on the basis of the 32 oxidative metabolic rates led to the distinction of five biovars which could then be defined by means of the five most discriminating substrates. Among the ten antibiotics tested, only three showed varying patterns of susceptibility. Oxidative metabolic rates were not correlated with these patterns of susceptibility nor with the enzymatic activities. However, a relationship was found between biovar and serovar, especially with regard to the following substrates: meso-erythritol, deoxythymidine, D-galactose and DL-phenylalanine. As shown by correspondence analysis, the repartition of biovars significantly differed among French administrative regions.

Anti-Bacterial Agents↗

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Schistosoma haematobium infection in western Madagascar: morbidity determined by ultrasonography.

To assess the morbidity related to Schistosoma haematobium infection in western Madagascar, an ultrasonographic examination was performed of 574 inhabitants > 5 years old in a village in an old-established endemic area where no prior systematic antischistosomal treatment had been given. The overall prevalence of infection was 75.9% and the geometric mean egg count of positive individuals was 36 eggs/10 mL of urine. Recent haematuria had been experienced by 31.8% of individuals. Echographic abnormalities of the urinary tract were present in 50.5% of individuals: they were more frequent in males. Bladder wall lesions were observed in 93.1% of individuals with ultrasonographic changes, irregularities of the inner surface being the most common finding. Congestive changes were noted in 8.4% of kidneys, but we observed only 4 severe congestions. Bladder lesions and congestive changes in kidneys predominated in youth; their presence and severity were significantly correlated with egg excretion. In 12 inhabitants, grade 1 periportal fibrosis was observed, but no significant association was found with S. haematobium infection. In a control village, where the prevalence of S. haematobium infection was 7%, moderate congestion of kidneys was observed in 2% of examined inhabitants, and bladder changes in 6%, with a significant relationship with S. haematobium infection.

Adolescent↗

PubMedDate not supplied

Reversibility of Schistosoma mansoni-associated morbidity after yearly mass praziquantel therapy: ultrasonographic assessment.

A parasitological, clinical and ultrasonographic longitudinal study was undertaken in 1993 in a focus hyperendemic for Schistosoma mansoni infection in the central highlands of Madagascar. All the inhabitants were systematically treated with praziquantel. A complete examination and treatment were repeated each year. Among the 289 villagers who underwent the complete 3 years' follow up, 65.9% excreted eggs at the initial survey and the mean egg count of infected individuals was 202 eggs/g. In 1996, the prevalence of infection was 19.3% with a mean egg count of 27 eggs/g and, among inhabitants aged > 44 years, only one was found to be infected. The proportion of individuals complaining of bloody stool decreased from 24.9% in 1993 to 8.4% in 1996. Compared to the initial clinical examination, the age-adjusted prevalence of splenomegaly was significantly lower in 1996, but remained high: 62% in the 10-14 years age group and 59% in individuals aged > 24 years. Ultrasonographic examination after 3 years of praziquantel therapy showed a marked decrease of the overall prevalence of schistosomal hepatic fibrosis, from 28% in 1993 to 10.3% in 1996. This improvement had already been achieved during the second year of follow-up for most subjects. Usually, the reversal of morbidity affected individuals classified as stage 1 at the beginning of the study. Stage 3 was not observed in the last 2 surveys. One patient's ascites disappeared during the follow-up, associated with a significant reversal of periportal fibrosis. Our results indicate that repeated praziquantel therapy can lead to improvement of liver morbidity and the prevention of the development of schistosomal hepatic fibrosis, even in an old-established hyperendemic focus.

Adolescent↗

PubMedDate not supplied

Rift Valley fever epizootic in the central highlands of Madagascar.

Between February and April 1991, unusual numbers of bovine abortion around Antananarivo (central highlands, Madagascar) were reported by official veterinary services. Rift Valley fever (RVF) virus isolations were made from sixteen aborted foetuses and one dead calf in different foci. Using monoclonal antibodies, the isolated viruses were found to be different from the 1979 RVF strains isolated in Madagascar from mosquitoes and human laboratory infection, and closer to African RVF strains. In a bovine population--previously characterized by a negative or very low RVF antibody prevalence--a high prevalence of IgM antibodies (264/994: 26.5% positive) was revealed; the IgM prevalence in recently aborting females varied from 40 to 91%. Among 994 human sera tested by IgG-IFA (immunofluorescent antibody assay) and IgM ELISA, 8.2% and 4.5%, respectively, proved positive. A total of 11,371 mosquitoes (61% Culex antennatus) were collected in the epizootic areas and tested without any virus isolation. Extensive studies were conducted to determine the geographical extension and the impact of this epidemic on the highly susceptible livestock and human populations.

Abortion, Veterinary↗

PubMedDate not supplied

[Significance of IgM titration by an immunoenzyme technic for the serodiagnosis and epidemiological surveillance of dengue in French Polynesia].

The usefulness of IgM antibody capture enzyme-linked immunosorbent assay (ELISA-IgM) for the diagnosis of dengue was studied using several groups of sera. An attempt was made to detect IgM against each dengue serotype. Of 76 paired sera from patients with dengue type 4 infection, the diagnosis was confirmed by ELISA-IgM in 74: in 47 out of 49 primary dengue infections and in all 27 secondary dengue infections. It was possible to detect IgM in 15 of the acute sera of primary infections and in 16 of the acute sera of secondary infections. In 20 patients from whom only single serum with high haemagglutination-inhibition titre (greater than or equal to 640) was available, 18 were found positive for dengue IgM. Dengue infection was also confirmed in 10 patients with dengue type 1 and in 10 patients with dengue type 2. IgM was detected in 1 of the acute sera of patients with either dengue type 1 or dengue type 2 infection. In all cases in which IgM was detected, a positive response was obtained for the homologous antigen. ELISA-IgM on sequential serum samples from 7 proven cases of dengue type 4 revealed that antibody titres greater than or equal to 400 are reached early in the second week of the illness and persist for 60 days or more at a low level (titre less than 400). An attempt was made to obtain a type-specific presumptive diagnosis by analysing the relative titre against each of the 4 antigens. It was possible to make a diagnosis of dengue type 4 in 85% and 52% of IgM-positive responses in primary and secondary infections (p less than 0.01), respectively, using paired sera from patients with known dengue type 4 infection. ELISA-IgM was shown to be of interest in the diagnosis and surveillance of dengue in French Polynesia where dengue viruses are, presently, the only known flavivirus.

Antibodies, Viral↗

PubMedDate not supplied

Plague, a reemerging disease in Madagascar.

Human cases of plague, which had virtually disappeared in Madagascar after the 1930s, reappeared in 1990 with more than 200 confirmed or presumptive cases reported each year since. In the port of Mahajanga, plague has been reintroduced, and epidemics occur every year. In Antananarivo, the capital, the number of new cases has increased, and many rodents are infected with Yersinia pestis. Despite surveillance for the sensitivity of Y. pestis and fleas to drugs and insecticides and control measures to prevent the spread of sporadic cases, the elimination of plague has been difficult because the host and reservoir of the bacillus, Rattus rattus, is both a domestic and a sylvatic rat.

Animals↗

PubMedDate not supplied

[Duration of action of the pyrimethamine-sulfametopyrazine combination in a Plasmodium falciparum endemic zone].

The duration of action of the drug Antemal, a combination of Pyrimethamine and Sulfametopyrazine, was eveluated in Bobo-Dioulasso, Upper Volta, West Africa, and endemic zone for Plasmodium falciparum malaria. The study was held during the season of maximum malaria transmission. 79 persons presenting with an acute attack of malaria were studied; 37 persons received a single dose of chloroquine sulfate (Nivaquine), at a dose of 15 mg./kg.; 42 persons received a single dose of Antemal at a dose of one tablet (75 mg. of Pyrimethamine and 25 mg. of Sulfametopyrazine) per 10 kg. Clinical and parasitological studies of all subjects occurred on days one, two, three, 10, 17, 24 and 31. Only one of 37 (2.7%) subjects on Antemal had a reappearance of trophozoites, occurring on day 17. Eight of 42 (19.0%) patients taking nivaquine had reappearance of trophozoites, observed between day 23 and 31. Gametocytes were observed in eight of 37 (21.6 %) persons on Antemal and in only one of 42 (2.3 %) persons on Nivaquine. These observations suggest an extended duration of protection from Antemal in semi-immune individuals. Nivaquine appeared as a potent inhibitor of gametocytogenesis.

Administration, Oral↗