Anti-Salmonella activity of metabolites from African soldier termites, Macrotermes bellicosus

Background: The global emergence and rapid dissemination of multidrug resistant Salmonella strains necessitate research to find new antimicrobials that will effectively be used against these pathogens. In the present study, anti-Salmonella activity of metabolites from African Soldier Termites, Macrotermes bellicosus was demonstrated and subsequently compared with a potent antibiotic, ciprofloxacin. Materials and Methods: N-hexane, ethylacetate, methanol and aqueous extracts of metabolites from the M. bellicosus were assayed for anti-Salmonella activity using the agar dilution method in the determination of the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). The inhibitory activities of the extracts were compared to ciprofloxacin (256µg/ml). Also, the bioactive components of the extracts were determined using standard techniques. Results: At 4000 µg/ml, N-hexane extract inhibited the growth of Salmonella Typhi, S. Paratyphi A, B and C while ethylacetate extract was able to inhibit S. Paratyphi A and C. Methanolic and aqueous extracts at the same concentration were unable to inhibit these strains of Salmonella. Furthermore, our findings revealed that the MIC of ethylacetate extract was 2000µg/ml for S. Paratyphi A and B, 250µg/ml for S. Typhi, and 125µg/ml for S. Paratyphi C. Also, the MIC of hexane extract was 4000µg/ml for S. Paratyphi B, 2000 µg/ml for S. Paratyphi C, 500µg/ml for S. Typhi and 250µg/ml for S. Paratyphi A respectively. The screening of bioactive components revealed the presence of cardiac glycosides and alkaloids. Conclusion: Our results provide evidence of anti-Salmonella action of metabolites from African Soldier Termites, M. bellicosus. N-hexane and ethylacetate extracts of M. bellicosus may be explored as novel antimicrobials for the treatment of typhoid and paratyphoid fevers thereby reducing the pressure exerted on available antibiotics

The role of urea in the oviposition behaviour of japanese encephalitis vectors in rice fields of South India

The effect of urea on the oviposition behaviour of culicine vectors of Japanese encephalitis was studied in rice fields. Gravid females had a strong preference for oviposition in urea treated areas in rice fields, while no such preference was exhibited in untreated areas. The egg laying declined in the area where urea treated water surface had a mechanical barrier, which allowed volatile fractions to escape, but prevented contact with the water. Urea was shown to act as an oviposition attractant/stimulant for Culex tritaeniorhynchus, but its role was not clear for Cx. vishnui, as the number of egg rafts obtained for the latter species was low

Japanese encephalitis in India.

Japanese encephalitis (JE), caused by a mosquito-borne virus was first recognised in India in 1955 and since then many major out-breaks from different parts of the country have been reported, predominantly in rural areas. Children are mainly affected, with morbidity rate estimated at 0.30 to 1.5 per 100,000 population. Case fatality rate has ranged from 10% to 60%, and up to 50% of those who recover may be left with neurological deficits. Reported incidence has generally been higher in males than in females, but subclinical infections have occurred equally in both sexes. A large number of subclinical infections occur each year during the transmission season. Diagnosis at the primary health centre (PHC) level is based on clinical symptoms only. Therefore, there is a need to develop simple tests for use at the peripheral level both for diagnosis and for epidemiological surveys. JE is a vaccine preventable disease, but there are many logistic problems for effective implementation of vaccination.

Comparative evaluation of bioassay and ELISA for detection of Japanese encephalitis virus in field collected mosquitos.

Comparative evaluation of enzyme-linked immunosorbent assay (ELISA) and bioassay (virus isolation in Toxorhynchites splendens larvae and identification by immunofluorescence test using virus specific monoclonal antibody) was carried out in order to define a suitable strategy for monitoring Japanese encephalitis virus infection in field mosquitos. A total of 8,850 adult female mosquitos in 177 pools (Culex tritaeniorhynchus 91, Cx. vishnui 59 and Cx. fuscocephala 27) collected from an endemic area of Tamil Nadu were examined by both the techniques. In ELISA, 9 pools which had optical densities (OD) equal to the mean of normal infected pools plus > or = 4 standard deviations (SD) mean considered positive and all of them were virus positive by the bioassay also. Sixty-five pools had OD = Mean + 2-3 SD and 103 pools had OD = Mean + < 2 SD of normal pools. From these groups, 12 (18.5%) and 8 (7.8%) pools respectively were found to be virus positive by the bioassay. In total 29 (16%) pools were positive by the bioassay as against 9 (5%) by ELISA. This study demonstrated that the bioassay is sensitive for estimation of true positives and ELISA is a rapid screening system. A protocol has now been developed for surveillance in which field pools are first screened by ELISA and only those with OD = Mean + > or 2 SD are assayed in Toxorhynchites. By excluding a large majority of pools with low OD (Mean + < 2 SD), which are likely to yield to only a small percentage of true positives, the cost, time and labor involved are greatly reduced.(ABSTRACT TRUNCATED AT 250 WORDS)

Composite fish culture for mosquito control in rice fields in southern India.

Composite culture of edible fishes (common carp, Cryprinus carpio; silver carp, Hypopthalmithys molitrix, grass carp, Ctenopharyngodon idella; catla, Catla catla; rohu, Labeo rohita; and mrigal, Cirrhinus mrigala) in rice fields in the Cauvery delta of Tamil Nadu, southern India, resulted in 81.0% reduction in the immature mosquito population of anophelines and 83.5% of culicines. Analysis of fish feces for mosquito larval head capsules showed that common carp and silver carp are effective larvivores. The selective feeding of common carp on culicines and silver carp on anophelines is correlated to their trophic niches. Net profit in the fish-cum-rice fields was 2.5 times greater than fields in which rice alone was cultured. Hence, rice-cum-fish culture can be recommended to the farming community in this area.

Space-spraying with malathion as a supplementary measure for operational malaria control.

Entomological studies showed that due to outdoor resting by the vector Anopheles culicifacies as well as poor spray coverage, indoor residual spraying with malathion was ineffective in malarious villages of the Thenpennai riverine tract in Tamil Nadu. Over a 4 yr period during which residual spraying was supplemented with ground applications of malathion space spraying, the slide positivity among patients with fever fell from 21.04 to 1.1 per cent. In mass blood surveys 0.7 per cent persons surveyed at the beginning of the study were positive for the malarial parasite, but no positives were detected in the last survey, in 1984. There was a rising trend in malaria incidence in riverine villages outside the programme.