Seroepidemiology of malaria in Karnataka State: longitudinal study of a population from an area with high incidence at Kolar, South India

Serologic methods have considerable value in epidemiologic surveillance of malaria. Antigens prepared from P falciparum cultured in vitro have been found to be sensitive and to a certain extent specific in the IFA test to detect malarial antibodies in the sera from a population continuously exposed to P falciparum and Plasmodium vivax infections [1]. However, it is necessary to assess the serologic data against the results of conventional examination of peripheral blood smears in monitoring the effect of antimalaria measures on malaria transmission. With this objective, we studied a randomly selected population from GPHU, which is located in an area in the Kolar District of the state of Karnataka where malaria is known to be endemic. During the transmission period of 1980 (from July to November), the annual parasitic incidence was 202 per 1,000, with 78% due to P vivax and 22% to P falciparum. The antimalaria measures were subsequently intensified by the GPHU staff, which lead to a decrease in the incidence of malaria in 1981 (60 per 1,000, with 91% due to P vivax and 9% to P falciparum; data obtained from GPHU records). Serum samples were collected after each transmission period and tested by IFA using a local isolate of P falciparum as antigen. There was a marked decrease in the number of seropositive samples in the second batch among children less than 10 years of age and a threefold decrease in malarial antibody titers up to the age of 15 years.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of a crude soluble antigen from in-vitro culture of Plasmodium falciparum for ELISA

The present study was to evaluate the soluble antigen prepared from the in-vitro cultured P. falciparum (FCR3) as an alternative source of antigen to those obtained from in-vivo models for enzyme linked immunosorbent assay (ELISA) in serology of malaria. Results obtained on known positive and negative reference sera revealed good correlation between the ELISA and the indirect fluorescent antibody (IFA) technique (rs = 0.797; p less than 0.001). However such close correlation was not observed on six local sera from patients whose peripheral blood smear showed ring stage of P. falciparum (rs = 0.43; p greater than 0.05), though all the six sera were positive by the IFA and ELISA tests. Test was repeated to establish its reproducibility. The results indicate that antigen prepared from in vitro culture and stored in liquid nitrogen was found sensitive in ELISA for serology of malaria.

Evaluation of in-vitro-cultured Plasmodium falciparum as antigen for malaria serology

A handicap in developing seroepidemiology for malaria in India is the lack of homologous antigens. Aotus monkeys, in which human plasmodia can be propagated, are not easily available in India. Other alternatives include the use of infected human blood or the in-vitro culture of Plasmodium falciparum, using the candle-jar technique of Trager & Jensen (1976). With certain modifications, the in-vitro culture technique has been established at the St John's Medical College (SJMC) to obtain a regular and high yield of P. falciparum to use as a source of antigen in serological tests. Antigens prepared from in-vitro-cultivated P. falciparum have been tested against positive and negative reference sera by the indirect haemagglutination (IHA) and immunofluorescent antibody (IFA) tests. These reference sera were also tested with the IHA test by using P. falciparum-sensitized human "O' erythrocytes received from the Center for Disease Control (CDC), Atlanta. IHA test results with both types of antigens were comparable (Spearman rank correlation coefficient, rS=0.8440, P less than 0.01). The antigen from in-vitro culture was also found suitable for use in the IFA test. The IFA titres obtained were comparable to those found at the CDC (Spearman rank correlation coefficient, rS=0.7940, P less than 0.01). These results indicate that P. falciparum parasites prepared from in-vitro continuous culture can be used as a source of antigen for use in the IHA and IFA tests for malaria.

Bacterial flora of the jejunum: a comparison of luminal aspirate and mucosal biopsy

The aerobic and anaerobic bacterial flora grown from 40 human jejunal aspirates were compared with the flora grown from an intestinal mucosal biopsy obtained simultaneously from the same level. In four paired samples the flora was identical; in nine the flora differed by only one organism. In six pairs the flora differed by two organisms, and in 11 pairs by three or more organisms. In nine pairs the jejunal aspirate grew only one organism or was sterile, but the biopsy showed considerable numbers of organisms. In one pair the jejunal aspirate grew organisms, but there was no growth from the biopsy. It is apparent that for adequate bacteriological study of the intestine, the flora at both sites should be investigated.

Jejunal microbial flora of southern indian infants in health and with acute gastroenteritis

The microbial flora of the jejunal lumen of 28 infants with acute gastroenteritis was compared with that of a group of 10 normal infants. The jejunum of control subjects harboured an "oral" type of flora and in a few instances enterobacteria in small numbers. The concentrations of all but one of the groups of organism were higher in the patients than in controls, and the differences were of statistical significance for enterobacteria and lactobacilli. In eight subjects, the same pathogen was identified in the jejunum and the stool. In six subjects with rotavirus infection, there were almost no Gram-negative aerobic rods in the jejunum. The possible role of other Gram-negative aerobic rods in producing gastroenteritis is discussed. It is suggested that studies of jejunal flora are of considerable importance in assigning an aetiological role to bacteria in the causation of acute gastroenteritis.

Faecal flora of South Indian infants and young children in health and with acute gastroenteritis

The faecal flora of 29 healthy infants and young children was compared with that of 49 children of similar age and socio-ecomonic status with acute gastroenteritis. In the healthy children the most common organisms in the faeces were bifidobacteria, veillonellae, enterobacteria and enterodocci with anaerobes outnumbering aerobes. Most members of the noraml faecal flora were present in the diarrhoeal stools, but anaerobes were signigicantly reduced in number and enterobacteria were significantly increased, thereby altering the ratio of anaerobes to aerobes. The alterations in the flora were not related to the nature of the aetiological agent or to the severity of the diarrhoea. The changes appeared to be a direct result of the altered colonic environment produced by the diarrhoeal state. In 13 of the 28 patients from whom bacterial pathogens were isolated, the pathogens were the predominant faecal organsims.

Intestinal perfusion studies in tropical sprue. 2. Movement of water and electrolytes

Jejunal absorption of sodium and water has been investigated in 10 normal Indians and 11 patients with chronic tropical sprue. Normal saline and solutions containing amino acids and dipeptides were studied. In both groups little absorption of sodium and water from normal saline was seen. Mean water and sodium absorption from the free amino acid or dipeptide solutions showed no significant difference between the groups and was similar to absorption from normal saline. These results differ from data obtained in normal English subjects where at these concentrations significant stimulation of sodium and water absorption was seen. In a proportion of subjects in both groups net secretion was observed. However, no correlation was seen between mucosal histology or luminal bacteriology and sodium or water movement. These findings in patients with chronic tropical sprue are similar to findings in normal Indians and suggest that jejunal handling of sodium and water is abnormal when compared with normal English subjects, but that the mucosa is not in a secretory phase as seen in certain other diarrhoeal states or in the acute early phase of sprue.

Aetiology of acute gastroenteritis in infancy and early childhood in southern India

The aetiology of acute gastroenteritis was studied in 50 infants and young children. Bacterial pathogens were isolated in 33, enteropathogenic E. coli (EPEC), Salmonella, and Shigella being the commonest isolates. Rotaviruses were detected in the stools of 13 of the cases. All children with gastroenteritis in whom rotavirus was detected were seen during the months July to December. In 30 children who served as controls, EPEC were isolated in 6, but rotavirus was detected in none. It is concluded that infection with rotaviruses is a significant cause of morbidity in children with gastroenteritis in southern India.

Vitamin B12 absorption--a study of intraluminal events in control subjects and patients with tropical sprue

The intraluminal fate of orally administered radioactive vitamin B12 has been studied in control subjects with normal vitamin B12 absorption and those with vitamin B12 malabsorption due to tropical sprue. In control subjects 1 to 21% of the dose was bound to sedimentable material and 37 to 75% was bound to immunoreactive intrinsic factor. In subjects with vitamin B12 malabsorption due to tropical sprue, the results were identical with the control subjects. Bacteriological studies showed a statistically significant correlation between both the number of flora in the jejunum and the number of bacteroides in both the jejunum and ileum and vitamin B12 malabsorption. In patients with tropical sprue who have normal intrinsic factor secretion, the vitamin B12 absorptive defect is not due to binding of the vitamin to bacteria or to alteration to the intrinsic factor vitamin B12 complex in the intestinal lumen. The lesion appears to be one of the mucosal cell receptors or of the cells themselves, possibly caused by bacterial toxins.

Comparative evaluation of desoxycholate citrate medium and xylose lysine desoxycholate medium in the isolation of shigellae

Studies of the relative efficacies of different modes of transport of fecal specimens intended for culture for the isolation of Shigellae have been carried out. When the delay between collection and culture was long, transportation in liquid nitrogen was slightly but not significantly better than transportation on ice. When the delay was short (10 hours or less) transportation at ambient temperature was as satisfactory as that on ice. A comparative study of the efficacies of three media for the isolation of Shigellae was also carried out. A total of 75 stool specimens containing Shigellae was studied. Isolation rates were highest with xylose lysine desoxycholate medium (XLD) and desoxycholate citrate medium (DCA). XLD was superior to DCA in that the Shigella colonies were clearly visible after overnight incubation, whereas use of DCA necessitated 48 hours of incubation. Also, colonial morphology on XLD was more specific. It is recommended that both XLD and DCA be employed, but if only one medium is to be used, XLD is the medium of choice.