Cytogenetic observations on an extensive material of the Anopheles culicifacies complex from the Thenpennai river area, Tamil Nadu, South India show that the populations are made up of four cytologically distinct species. Three of these, labeled A, B and C have already been described. A fourth one, monomorphic for the inversion arrangement +a +b in the X chromosome and il + hl in the second chromosome, is designated as D, another morphologically indistinguishable sibling species. Each sibling species is characterized by a species-specific type of Y-chromosome. Both of these criteria, inversions and Y-chromosomes can be used to distinguish these important malaria vectors.

Animals↗

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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.

Adolescent↗

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Evaluation of malaria clinics in Thailand.

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Ambulatory Care Facilities↗

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Surveillance for Japanese encephalitis in villages near Madurai, Tamil Nadu, India.

A simple dusk index was developed to monitor the density of recognized vectors of Japanese encephalitis virus (JEV) based on hand catches around cattlesheds at dusk and parous rates. When used routinely in combination with sentinel animal studies for surveillance in villages with a high prevalence (46.2%) of neutralizing antibodies against JEV in children under 16 years, there was a peak in vector density and virus activity during the north-east monsoon period, October-December. The reasons for an unusual outbreak of cases of encephalitis during the summer months of 1984 are discussed.

Animals↗

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Epidemiology of subperiodic Wuchereria bancrofti infection in the Nicobar Islands, India.

Diurnally subperiodic filariasis due to Wuchereria bancrofti has been reported from tribal populations in the Nancowry group of islands in the Andaman and Nicobar Islands, India. This was confirmed in a survey carried out during the monsoon season in 1993. Microfilariae were detected in the peripheral blood throughout a 24 h period with a peak at 18:00. The microfilaria (mf) rate ranged from 1.2% to 18.7%, with a low disease rate (mean = 1.9%). Incidence of mf was low in children less than 10 years old (3.5%), but increased with increasing age. Culex (Culex) quinquefasciatus was present at a very low density. Aedes (Finlaya) niveus and Aedes (Stegomyia) malayensis were the only species commonly biting man. The former was incriminated as a vector, and found naturally infected with W. bancrofti (infection and infectivity rates 1.1% and 0.9% respectively). After experimental feeding on donors, W. bancrofti developed to L3 stage larvae in A. niveus but failed to develop in A. malayensis and A. aegypti.

Adolescent↗

PubMedDate not supplied

Erythroid differentiation and the cell cycle: some implications from murine foetal and erythroleukemic cells.

On the basis of observations with (1) erythropoietin induced erythroid differentiation of foetal mouse liver proerythroblasts and (2) chemically induced expression of the erythroid program in MELC, it appears that DNA replication plays a critical role in the transition to haemoglobin formation. Erythropoietin acts selectively on proerythroblasts to stimulate first housekeeping RNA species (rRNA, tRNA), then cell proliferation and differentiation. In erythro-leukemia cells expression of the erythroid program is induced by a variety of polar compounds. DNA synthesis appears requisite to this transition to haemoglobin formation, The molecular site of action of inducing compounds is not established but it is suggested that one critical effect is on the structure of chromatin which occurs during DNA replication and results in the transcription of the erythropoietic gene program.

Animals↗

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Population dynamics of mosquito immatures and the succession in abundance of aquatic insects in rice fields in Madurai, South India.

Studies on the breeding pattern of mosquito immatures and the successional changes in the abundance of aquatic insects were conducted in rice fields near Madurai, south India. The population of late (III/IV) larval instars of culicines peaked on Day 28 and pupae (Culex tritaeniorhynchus, Cx. pseudovishnui and Cx. vishnui) peaked on Day 9 after transplantation, whereas the population of late (III/IV) larval instars of anophelines peaked on Day 19 and pupae of Anopheles subpictus and An. vagus on Days 7 and 9 respectively, after transplantation of paddy. A total of 14 families (consisting of 17 subfamilies) of aquatic insects belonging to six different orders, Coleoptera, Diptera, Ephemeroptera, Hemiptera, Anisoptera and Zygoptera were collected during the study period and the abundance of each group of insects is discussed in detail. The Shannon-Weaver Diversity Index, applied to study the diversity of different groups of aquatic insects, showed a clear pattern in diversity of surface predators, bottom predators and non-predators of mosquito immatures. The multiple linear regression model reveals that notonectid adults, coenagrionids, libellulids and veliids act as important predators of mosquito immatures in rice fields.

Animals↗

PubMedDate not supplied

Effect of plant spacing on the population of mosquito immatures in rice fields in Madurai, south India.

A study was conducted during 'Kuruvai' crop season from December 1992 to January 1993 in the rice fields of the Agricultural College and Research Institute, Madurai, Tamil Nadu to determine the influence of plant spacing and plant canopy on the populations of mosquito immatures. Three paddy varieties (ADT36, IR50 and IR20) were selected with two types of plant spacing, one with normal spacing (15 x 10 cm) and another wider (20 x 15 cm) than the normal spacing. Results showed that the field planted with normal spacing of paddy had significantly higher populations of culicine and anopheline immatures than the fields planted with wider spacing of paddy. The paddy varieties did not have any significant effect on the population of mosquito immatures. Light intensity, measured at the water surface using an illuminometer, was inversely related to the development of plant canopy and the results suggested that plant canopy does not inhibit oviposition by mosquitoes in the early stages of paddy growth, but it was responsible for the decline in the populations in the later stages of paddy growth. The plant spacing had a significant effect on the populations of chironomids and libellulids and other insects were not affected significantly.

Agriculture↗