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Biomedical subjects

V Dhanda

Publications and source records attributed to V Dhanda.

At least 19 recordsLinked to original sources
PubMed1997

Virus isolation from wild-caught mosquitoes during a Japanese encephalitis outbreak in Kerala in 1996.

Out of 5357 wild-caught mosquitoes in 163 pools tested for virus using antigen capture ELISA and an insect-bioassay (inoculation into Toxorhynchites splendens larvae and identification by IFA using JE virus-specific monoclonal antibody), 16 flavivirus isolations were made of which 12 (75%) were identified as JE virus. Of the 12 JE virus isolations, 7 were from Culex tritaeniorhynchus, 3 from Mansonia uniformis and 1 each from Ma. indiana and Anopheles subpictus. Four isolations from Mansonia species for the first time reported here are noteworthy.

Animals↗
PubMed1996

A novel 70-kDa Triton X-114-soluble antigen of Plasmodium falciparum that contains interspecies-conserved epitopes.

In order to identify novel conserved integral membrane and other membrane-associated proteins of Plasmodium falciparum, lambda gt11-P. falciparum DNA library phages were immunoscreened with convalescent-phase mouse sera and rabbit antiserum against Triton X-114-soluble proteins of P. falciparum. One recombinant phage clone, L857, reacted with both of the antibody probes. Insert DNA (857 bp long) in L857 was 69% dA+dT rich and hybridized to a fragment of 1800 bp from mung bean nuclease-digested P. falciparum genomic DNA. The cloned parasite DNA did not show notable sequence homology with any known protein gene. The L857-encoded polypeptide, p34 (M(r) 34 kDa) was expressed in bacteria, fused to glutathione S-transferase (GST). The fusion peptide, GST-p34 (M(r) 62 kDa), was recognized by immune serum against Triton X-114-soluble antigens of P. falciparum and was reactive with anti-P. falciparum, anti-Plasmodium yoelii, and anti-GST sera. Rabbit antiserum raised against the fusion peptide recognized a 70-kDa protein from lysates of P. falciparum cells and a putative homologous 100-kDa protein from lysates of P. yoelii. The rabbit serum anti-fusion peptide antibodies bound to acetone-fixed P. falciparum-infected erythrocytes and, in immunofluorescent antibody tests, produced a punctate pattern of fluorescence suggesting that the 70-kDa native protein is associated with an apical organelle of the parasite.

Amino Acid Sequence↗
PubMed1996

Spread of lymphatic filariasis, re-emergence of leishmaniasis & threat of babesiosis in India.

The impact of unabated population growth and consequent ecological changes is felt in the spread of vector-borne diseases also. Filariasis, once considered to be more associated with urban areas and urbanization, is rapidly emerging as a major problem in rural areas. The need to delimit the endemic areas through a new rapid assessment procedure and the possible control methods of rural filariasis are discussed. Leishmaniasis has re-emerged with a vengeance in some parts of the country and the reasons for this are analyzed. Babesiosis, though zoonotic, has the potential to invade the domain of man in India.

Animals↗
PubMed1995

A report on the demonstration of microfilariae of Brugia malayi in the brain of an experimental animal host, Mastomys natalensis.

The brain tissues of microfilaraemic animals, Mastomys natalensis, which were earlier inoculated (s.c.) with Brugia malayi infective larvae (100 each) were examined for the occurrence of Mf. This was done by staining squash preparations of the brain tissues which were cleared off from the vascular piamater. Animals with blood Mf count of 50 >/per 20 cu. mm were found to harbour Mf in the brain tissues. The Mf count in the brain varied from 5-86/81 cu. mm (sum of Mf detected in 3 tissue pieces, each of 27 cu. mm collected from 3 parts of the brain, viz., the cerebral hemispheres, cerebellum and medulla oblongata). Teh presence of Mf in the brain was confirmed by its detection in 20-micrometers-thick cryosections of the tissue. Also, fine needle aspirates of cerebral hemispheres of an animal showed live Mf.

Animals↗
PubMed1995

Response of gravid Phlebotmus papatasi females to an oviposition attractant/stimulant associated with conspecific eggs.

Oviposition response of gravid P. papatasi females to conspecific eggs was studied in laboratory colonized sandflies. It was observed that significantly higher number of eggs were laid in the vicinity of conspecific eggs. However, a certain minimum number of eggs were required to be placed on the substratum to influence the rate of oviposition. The fecundity of females (mean = 56.5 +/- 4.9 eggs) exposed to conspecific eggs was significantly higher (P < 0.05) than that of blank control group. Perhaps, the chemical substances/pheromone of egg origin stimulated the oviposition rate. In an attempt to isolate the active ingredient, solvent washing of the conspecific eggs were tested. No increase in the rate of oviposition was noticed when the test site was treated with distilled water extract, whereas, significantly larger number of eggs were laid at the site treated with di-ethyl ether extract. This indicated that the oviposition attractant associated with the eggs dissolved in the organic solvent, but not in water. The possible application of this attractant for wild sandflies in nature and for regulating the site of oviposition on the substratum in the laboratory colonized sandflies needs to be explored.

Animals↗
PubMed1994

Estimation of permissible levels of transmission of bancroftian filariasis based on some entomological and parasitological results of a 5-year vector control programme.

The impact of a 5-year vector control programme on transmission of bancroftian filariasis and microfilaraemia levels in the human population was examined in Pondicherry, South India. The programme reduced and maintained the transmission of Wuchereria bancrofti at appreciably low levels in many localities of Pondicherry town, but its impact on overall microfilaraemia prevalence was only limited. However, prevalence of infection was reduced drastically in children born after establishment of the programme and only 18% of the number expected without vector control were found infected. No new infections were found in localities with less transmission intensity. It is proposed that a Transmission Intensity Index of 0.50 and Annual Transmission Potential of less than the 96-105 range are permissible levels of transmission, and below these levels no new infections may occur. The required duration of vector control to eliminate Culex-borne filariasis foci is estimated to be 11-12 years, slightly longer than that required to eradicate anopheline-borne filariasis.

Animals↗
PubMed1994

Phlebotomine sandflies (Diptera: Psychodidae) of Tamil Nadu and Pondicherry, southern India, in relation to visceral leishmaniasis.

The Phlebotomine sandfly fauna of Tamil Nadu and Pondicherry in South India is described. Two morphologically different forms of Phlebotomus argentipes, the vector of Indian visceral leishmaniasis, are reported from Madras, a known focus of visceral leishmaniasis. A new species, Sergentomyia shettyi sp. nov., is described and Sergentomyia babu and Sergentomyia insularis stat. nov. are considered distinct species on the basis of their parapatric distribution. Phlebotomus papatasi and P. argentipes were the most abundant species around houses (37% and 29% of the catch, respectively), based on 1 year's sampling in villages near Pondicherry. The incidence of visceral leishmaniasis in Tamil Nadu since 1903 is summarized.

Animals↗
PubMed1994

Morphological and chromosomal descriptions of new species in the Anopheles subpictus complex.

Anopheles subpictus Grassi is shown to comprise four reproductively distinct species, designated A, B, C and D, occurring sympatrically in villages of Pondicherry, southeast India. Adult females were reared individually from wild larvae and examined for their morphological and chromosomal characters. Paracentric fixed inversions on the X-chromosome serve to distinguish the species cytogenetically, with no inversion heterozygotes (i.e. no interspecific hybrids) among totals of 717 species A (X+a, +b), 1863 species B (Xa, b), 869 species C (Xa, +b) and 1365 species D (X+a, b) identified. Morphologically, diagnostic characters for each of the four species are seen in the egg float ridge number, larval mesothoracic seta 4, pupal seta 7-I and the palpi of female adults. Species A, C and D immatures inhabit freshwater, whereas the malaria vector species B breeds in saltwater and was found only in coastal villages.

Animals↗
PubMed1994

Micro-spatial variation in filarial disease and risk of developing disease associated with microfilaremia in urban situation.

Clinical and parasitological surveys were carried out concurrently during 1986 in Pondicherry. The analyses showed that there was no significant micro-spatial variation in prevalence of total diseases (acute and chronic) and the manifestations such as hydrocele and lymphedema in the different zones and stations of Pondicherry urban area, a stable endemic area. Analyses on different filariometric indices in different stations showed a significant correlation between disease and mf prevalence (r = 0.4106; p = 0.037). The prevalence of disease and hydrocele in microfilaremic individuals (9.4% and 20.0% respectively) was higher compared to that observed in amicrofilaremic persons (6.4% and 11.2% respectively). The relative risk (RR) of parasite carriers developing disease (any manifestations) was marginally higher compared to amicrofilaremic persons (1.18). However, the RR of developing hydrocele manifestation due to microfilaremia was much greater (1.5) compared to amicrofilaremic persons. The attributable risk (AR) due to microfilaremia for developing hydrocele was 0.05. This suggests that although the risk is high in mf carriers, there might be alternate ways of developing disease without the infected person becoming microfilaremic. The limitations of point prevalence data on understanding complex dynamics of infection and disease are discussed.

Animals↗
PubMed1994

Cumulative exposure and its relationship with chronic filarial disease in bancroftian filariasis.

Several hypotheses have been put forth about the factors influencing the dynamics of infection and disease in lymphatic filariasis. However, appropriate validation of these hypotheses by real situation analyses of epidemiological data is lacking. The present analyses examine the relationship between cumulative exposure to infection and prevalence of disease by utilizing the existing entomological and clinical data collected between 1981 and 1986 in Pondicherry, South India, endemic for bancroftian filariasis. While there was a significant negative association when the cumulative exposure was correlated with total prevalence of disease (r = 0.70, p = 0.024) as well as hydrocele alone (r = 0.74, p = 0.014), a significant positive association was found with prevalence of lymphedema (r = 0.72, p = 0.018). These results suggest that hydrocele development follows early after exposure, but prolonged exposure could result either in development of lymphedema or immune tolerance resulting in microfilaremia. These could also suggest that the pathomechanisms in development of hydrocele and lymphedema could follow different pathways. Implications of the present findings are discussed in light of the various hypotheses put forward by earlier studies.

Age Factors↗
PubMed1993

Population dynamics of Phlebotomus papatasi (Diptera:Phlebotomidae) in Pondicherry, India.

Investigations on the population dynamics of Phlebotomus papatasi were carried out. The average indoor resting density fluctuated between 16.70 and 2.25/man-hour in different seasons with a maximum density during monsoon season. There was a significant positive correlation between density and rainfall. Probability of daily survival of adult population was high in monsoon and low in summer. Both relative humidity and temperature influenced the survival. The finite rate of natural increase of the field population was maximum in October and minimum in April. The monsoon season, with moderate temperature and relative humidity was found to be favourable for the growth of P. papatasi population.

Animals↗
PubMed1993

Dengue in Gujarat state, India during 1988 & 1989.

Following the reports of epidemics of febrile illness from several rural and urban areas of Gujarat state (India) in 1988, epidemiological investigations were carried out and dengue (DEN) virus activity was demonstrated in large cities such as Surat and Rajkot as well as several villages in Sabarkantha district. Two strains of dengue type-2 each were isolated from human sera from Surat city and a village in Sabarkantha district. Six strains of dengue virus were isolated from Aedes aegypti mosquitoes collected at Chotasan village, two of which were confirmed as DEN type-2. Of the 560 patients' sera tested from different areas (including villages and townships), 122 showed evidence of dengue infection and another 236 showed a broader reaction with flaviviruses. Entomological investigations showed a widespread distribution of Ae. aegypti both in urban and rural areas. In the household conditions this mosquito was found to breed predominantly in containers with non-potable water. Amongst these, cement containers manufactured in towns and distributed to the villages seem to play an important role in the spread of this species. In non-residential areas prolific breeding of Ae. aegypti was observed in automobile tyre dumps, and varied types of scrap, in towns and villages. Distribution and relative prevalence of the species were studied in 46 towns and villages, covering the spectrum of rural-urban-continuum. These studies provide an indication regarding the mechanism of the spread of DEN virus through peoples' movement, transport, the process of urbanisation etc.

Aedes↗
PubMed1992

Occurrence of entomophilic nematode infestation among phlebotomid sandfly, Phlebotomus papatasi--a preliminary report.

Infestation of a nematode parasite was observed in the natural population of Phlebotomus papatasi in Pondicherry, India. Of the 877 males and 959 females sandflies examined for the natural infection, 11 females were found infested with nematodes (0.59%). The number of juveniles and/or eggs of nematodes per infected fly ranged from 1 to 192 (mean 51.36 +/- S.D 55.95). The presence of a stylet at the opening of the dorsal oesophageal duct suggests that the parasite belongs to the super family Tylenchoidea.

Animals↗
PubMed1992

Experimental studies on the susceptibility of Aedes vittatus to dengue viruses.

Ae. vittatus mosquitoes were infected by oral route and by intrathoracic inoculation with dengue (DEN) viruses and tested for the presence of dengue virus antigen in their head squashes and salivary glands by indirect immunofluorescence. The results indicate that this species was susceptible to all four types of DEN viruses and supported the growth of DEN-2 virus.

Aedes↗
PubMed1992

Community participation in the control of filariasis.

A programme was launched in 1986 for the control of brugian filariasis in an area of high endemicity in southern India. Sustained community involvement was achieved by integrating economic measures to improve the lot of the people with the creation of widespread awareness about the cause of the disease and about the possibilities of combating it.

Animals↗
PubMed1991

Susceptibility of four species of mosquitoes to Chandipura virus and its detection by immunofluorescence.

Susceptibility of Culex tritaeniorhynchus, Cx. Bitaeniorhynchus, Cx. quinquefasciatus, and Aedes aegypti to Chandipura (CHP) virus was compared after parental inoculation of the mosquitoes. Virus detection was done by indirect immunofluorescence (IF). CHP antigen in head squashes of all the four species was seen at 24 hr post infection (p.i.). The mosquitoes supported the virus growth and transmission by bite to 2 days old suckling Swiss albino mice. Ae. aegypti which was found the most susceptible mosquito species for CHP virus can be used as a substitute for laboratory mice.

Aedes↗
PubMed1991

Entomological investigations during outbreaks of dengue fever in certain villages in Maharashtra state.

Outbreaks of dengue (DEN) fever are reported from 22 villages in five districts in the state of Maharashtra. DEN viral antigen was detected by indirect immunofluorescence test in 34 of 375 female Aedes aegypti mosquitoes collected from 8 villages. DEN types 2 and 3 were identified among the 16 strains that were isolated. None of the 64 male mosquitoes showed the presence of viral antigen; 281 males and 323 females reared from field collected larvae were also found negative. Indoor spraying of DDT in the affected villages produced a drastic reduction in Ae. aegypti catches. No viral antigen was detected in mosquitoes caught subsequent to the spray. With the introduction of water supply through taps, which is often inadequate, people are compelled to store water for domestic purposes, which favours an increase in Ae. aegypti breeding. In view of changing rural ecology associated with the development process, continued surveillance of the spread of Ae. aegypti as well as the diseases borne by this vector are recommended.

Aedes↗