Medium-term outcome of total hip replacement for dysplastic hips in Singapore.

PURPOSE: To review medium-term outcomes of 46 patients who underwent total hip replacement (THR) for osteoarthritis secondary to dysplastic hips. METHODS: Records of 58 hips in 6 men and 40 women aged 32 to 76 (mean, 62) years who underwent THR for osteoarthritis secondary to dysplastic hips and had been followed up for a mean of 4 (range, 2-8) years were retrospectively reviewed. The hips were classified according to the Crowe's grading, Sharp's acetabular angle, and centre-edge angle. The radiological uncoverage of acetabular cup (RUAC) index was calculated. The outcomes of THR were evaluated in terms of cup inclination, RUAC index, cup migration, lysis or loosening (radiolucency), heterotopic ossification, component incorporation and positioning, thigh pain, and subsidence. RESULTS: 51 of the hips were Crowe's type I, 6 were type II, and one was type IV. The mean acetabular angle was 46.3 degrees and the mean centre-edge angle was 15.4 degrees. The mean cup, head, and stem sizes were 50.4 mm, 28.7 mm, and 10.9 mm, respectively. The mean RUAC index was 16.9% and the mean cup inclination was 40.7 degrees. Radiolucency of 1 mm in the acetabular zone I was observed in 16 cases, but only one failed. For cemented and uncemented stems, the most common positioning was neutral and valgus, respectively. Five patients had complications of greater trochanter fracture, aseptic loosening, split calcar, stem loosening, and/or heterotopic ossification. CONCLUSION: Conventional THR can achieve good medium-term results in low-grade dysplastic hips.

Effects of organic and inorganic fertilisers on mosquito populations in rice fields of southern India.

The effects of nitrogenous (inorganic) fertilisers, organic manures and blue-green algae (BGA) biofertiliser on mosquito populations (Diptera: Culicidae) were studied in rice fields of Madurai, Tamil Nadu, south India, with particular attention to Culex vishnui Theobald, Cx. pseudovishnui Colless and Cx. tritaeniorhynchus Giles, the vectors of Japanese encephalitis (JE). The application of urea, a nitrogenous fertiliser, in rice fields significantly increased the grain yield and the population densities of mosquito larvae and pupae (anophelines as well as culicines) in a dose-related manner. Fields treated with inorganic fertilisers (N, P, K) had significantly higher population densities of mosquito immatures than fields treated with organic manures (farmyard manure and green manure). Without nitrogenous fertiliser, BGA increased paddy yield without enhancing mosquito production. Therefore, the use of BGA with less nitrogenous fertiliser is recommended, which is beneficial economically and agronomically to the farming community and also significantly reduces mosquito production in rice fields. Increased use of nitrogenous fertiliser over the past two decades may have contributed to the increased severity of Japanese encephalitis epidemics, vectors of which breed in rice fields.

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.

First outbreak of Japanese encephalitis in two villages of Dharmapuri district in Tamil Nadu.

BACKGROUND & OBJECTIVES: Three cases of Japanese encephalitis (JE) were reported for the first time from two villages in Krishnagiri Health Unit district of Tamil Nadu during November 1999. Two children died and one developed neurological sequelae. A serological survey was conducted in these villages to find out the prevalence of JE antibodies among children below 15 yr of age in addition to the epidemiological investigations. METHODS: The prevalence of haemagglutination inhibiting (HI) antibodies to JE virus (JEV), West Nile virus (WNV) and dengue-2 virus (DEN-2) was detected by HI test and IgM antibody capture ELISA (MAC ELISA) was performed to determine recent infections with JE virus. Adult mosquitoes were collected in the study villages and females of Culex pseudovishnui, C. tritaeniorhynchus and C. vishnui were tested for the presence of JE viral antigen by ELISA. RESULTS: Out of 146 sera samples from children below 15 yr, the prevalence of HI antibodies to JEV, WNV and DEN-2 virus was found to be 8.9, 3.4 and 6.85 per cent respectively and three children had IgM antibodies to JEV. Of the 13 species of mosquitoes identified, C. tritaeniorhynchus (30.8%) was the most abundant species in the study villages. Two pools of female C. tritaeniorhynchus were found to be positive for JEV antigen. Fogging with 2 per cent pyrethrum and residual spray with 10 per cent cyfluthrin were effective in reducing vector density. INTERPRETATION & CONCLUSIONS: Serological investigations revealed that the JE virus was predominant in the study villages. In addition, DEN-2 and WN viruses were also prevalent. Detection of JE virus specific IgM antibodies in three specimens and the presence of JE viral antigen in 2 pools of C. tritaeniorhynchus emphasized the need for constant surveillance and monitoring so as to prevent future large outbreaks.

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.

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.

Aquatic macrophytes and the associated mosquitoes in and around Madurai City (Tamil Nadu).

A survey of mosquitoes was carried out in 7 weeded astatic ponds in and around Madurai from October 1990 to January 1991 to qualitatively determine the macrophyte-mosquito larvae association. Members of Culex vishnui subgroup were associated with most of the macrophytes. Eichhornia crassipes, Marsilea quadrifolia and Spirodella polyrhiza showed a high potential for mosquito breeding and Azolla sp., a very low potential for both anophelines and culicines.