Some aspects of changing behaviour of malaria vectors in tribal areas of India.

The field entomological studies and surveys carried out in 72 tribal districts out of 100 in seven penninsular States namely, Andhra Pradesh, Bihar, Gujarat, Madhya Pradesh, Maharashtra, Orissa and Rajasthan indicated that in most of the areas the vector mosquitoes encountered during the present study were almost the same as recorded by the earlier workers except that Anopheles fluviatilis James, 1902 was recorded in the areas of district Raipur, Durg, Bilaspur, Raigarh, Shahdol, Rajnandgaon, Barwani and Janjgir of Madhya Pradesh, and Sundergarh of Orissa during the present survey. This vector was not recorded in earlier studies by other workers. An. culicifacies Giles, 1901 was not found in present survey in East Godavari and Vishakhapatnam of Andhra Pradesh and Ganjam and Koraput of Orissa where this mosquito was found in collections earlier. Similarly, An. fluviatilis was not encountered during the present field study in Bhilwara of Rajasthan, Phulbani and Kalahandi of Orissa, Thane, Nanded and Nasik of Maharashtra and Bharuch of Gujarat state. During this study An. fluviatilis was noted to be mostly endophilic whereas earlier workers noted this mosquito to be exophilic in a large number of districts. The majority of the tribal districts seem to be under the influence of two malaria vectors, An. culicifacies and An. fluviatilis and these tribal districts are maintaining a high malaria endemicity with predominance of Plasmodium falciparum infection. In the present study, the transmission seasons were noted to be longer than recorded earlier in the districts of Andhra Pradesh, Gujarat, Rajasthan and Orissa. In the remaining states it is almost similar as recorded earlier.

Field trial of cyfluthrin as an effective and safe insecticide for control of malaria vectors in triple insecticide resistant areas.

Cyfluthrin (Solfac**) 10 wp, a synthetic pyrethroid was evaluated for its efficacy in malaria control through primary health centre approach, and for its acceptance by the community and effect on human health, and non target organisms, in predominantly tribal areas of Maharashtra and Gujarat from 1988 to 1990. Two dosage schedules; 2 rounds of indoor residual sparying a year, at 25 mg/sq. m2 in Maharashtra, and 3 rounds a year at 15 mg/sq. m2, in Gujarat were followed. There was significant reduction in per man hour densities of An. culicifacies the principal malaria vector, and collaterally of C. quinquefasciatus also. Significant reductions in slide positivity rates and slide falciparum rates were observed in both the areas as compared to the controls. The community acceptance of Cyfluthrin in terms of room coverage was 96% in Gujarat, and 89% in Maharashtra, as against average 68.5% and 55% in case of DDT and Malathion respectively. There were no reported ill-effects on humans or non-target organisms.

A community-based study on the effect of hexachlorocyclo-hexane (HCH) exposure in spraymen and general population.

The study was carried out in Allahabad district, (Uttar Pradesh) with 260 spraymen as test subjects and 50 persons as controls from a sprayed and unsprayed village respectively. Majority of the spraymen (44%) had worked for 3-4 years (seasons) and 31% had worked in the programme for 5-10 years. The spraymen were relatively healthy with no complaints in 77% whereas the figures were 76% for the Community living in the sprayed village, and 50% for the Community in the unsprayed village. A comparison of the biochemical parameters revealed lowered Cholesterol more than 150 mg % in 38% of the spraymen and 58% had altered A:G ratio. Other biochemical estimations were not significantly different from the control population. The mean residue of Alpha, Beta and Gamma Isomers and the total Alpha, Beta and Gamma isomers were 0.0317, 0.2254, 0.0288 and 0.2859 mg/1 respectively; the corresponding mean values in the control population were 0.0211, 0.1112, 0.0197 and 0.1520 mg/1 respectively. The values in spraymen were twice those of the general population. A significant association (p < .05) was observed between their length of exposure and the levels of Cholesterol and HCH isomers in blood of spraymen. No significant morbidity was evident in spraymen due to HCH exposure.

Impact of deltamethrin spraying on malaria transmission in Rameshwaram Island, Tamil Nadu State - India.

The impact of spraying Deltamethrin 2.5% w.d.p. @ 20 mg/m2 and its comparison with Malathion 25% w.d.p. @ 2 gr./m2 was assessed in Rameshwaram Island, Tamil Nadu. Monitoring of entomological and parasitological indices revealed that due to deltamethrin spray malaria transmission could be effectively interrupted and a significant reduction in malaria cases was achieved. P. falciparum cases also showed a significant reduction whereas in the comparison malathion areas reduction in malaria cases or in pf cases was not recorded.

Malaria problem and its control in north eastern states of India.

There has been a substantial increase in the overall malaria incidence and incidence of Plasmodium falciparum in the north-eastern region of India. The main contributory factors for this are: (i) difficult terrain, (ii) 'Jhum' cultivation, (iii) presence of optimum climatic conditions for prolonged transmission, (iv) presence of highly efficient malaria vectors, (v) developmental projects attracting aggregation of labour, (vi) influx of population along the international borders and (vii) chloroquine resistant P. falciparum strains. To combat this situation new approaches like providing 100 per cent Central assistance, intensifying training of personnel and DDT spray, opening Drug Distribution Centres and Fever Treatment Depots and making drugs available in the villages have been put into action. In this communication the overall malaria situation in the north-east India is discussed.

Malaria transmission during post-spray period of pirimiphos-methyl in Arunachal Pradesh.

Observations made for a period of four years from 1985 to 1988 on post-spray impact of pirimiphos-methyl (25 per cent Wp) on malaria vectors in Tirap district of Arunachal Pradesh showed that a low density (0.0 to 0.02 PMH) of Anopheles dirus was maintained in the areas sprayed with the insecticide at the dosages of 1 and 2 g/m2 from 1981 to 1984. The post-spray data (1985 to 1988) showed a reduction of 62.5 to 62.8 per cent in SPR, 55.6 to 64.7 per cent in SRF and 72.3 to 75.5 per cent decline in API as compared to baseline data of 1980 in areas sprayed with pirimiphos methyl.

Residues of DDT and its metabolite in blood of exposed factory workers and their correlation with ill health symptoms.

The residue levels of DDE, op1--DDT and pp1--DDT of the factory workers exposed to DDT formulations having temporary clinical symptoms and of those without any such symptoms did not show any significant difference in their values suggestive of no direct correlation between insecticide residues and ill health symptoms. The average residue values of DDT (mg/litre) and its metabolite DDE (mg/litre) in exposed workers were 0.8634 +/- 0.1529 and 0.2106 +/- 0.0458 respectively while in unexposed control subjects 0.0826 +/- 0.0238 and 0.0278 +/- 0.0040. Total DDT residue in blood in exposed workers is more than 10 times higher than the same in unexposed control.

Filaria situation in the Union Territory of Dadra & Nagar Haveli.

A resurvey conducted 8 years later in the Union Territory of Dadra & Nagar Haveli revealed the persistence of filariasis amongst its residents. Though no control measures have been in operation since the detection of filariasis in Dadra and Nagar Haveli in 1982, the parasitological indices, microfilaria (mf) and disease rates as well as mf count have remained static. The entomological studies revealed five times increase in density of Culex quinquefasciatus both in Silvassa and Naroli towns.

Deterioration of DDT 50 per cent water dispersible powder packed in hessian bags during storage.

One hundred seventeen samples of DDT 50% WP received from field where supplies were effected, were tested during 1988-89 for suspensibility without accelerated storage treatment (ATS) as per ISI specifications and compared with their suspensibilities after ATS obtained during the initial testing to know the stability status of the insecticide during transit and tropical storage in the field when packed in hessian bags. Out of 117 samples tested 95 (81.2 per cent) failed and only 22 (18.8 per cent) passed the test for suspensibility indicating deterioration of the formulation in the field.

Vector control through environmental management with special reference to India--approach prospectives.

The introduction of different types of pollutants like those from industrial effluence, bye-products from petro-chemical industries, pesticidal application, wastages of nuclear power industries, etc. is viewed seriously by the society. For the control of vectors of disease the adoption of environmental management is, therefore, imperative. The physical methods like drainage of excess and waste water, making water unsuitable for vector breeding by adopting various indigenous methods in vogue, the intra and inter-sectrol coordination and community based activities are identified as the basic approaches for achieving this goal. Minimising the potentiality of vector breeding through source reduction and water management is thought to be the simplest, cheapest and most permanent method. For the society having varying types of habitation and varying degree of habitational facilities like planned housing, water supply and disposal, sanitation and organized anti-vector measures, the adoption of environmental management to exercise check over vector population is a promising proposition. The suitability of such an approach has already been demonstrated by MRC, (ICMR), Delhi and V.C.R.C., Pondicherry. The implementation of these methods is to be initiated right from Primary Health Centre and district level onwards and community is to be motivated to the extent that the various methods of environmental management for vector control are adopted in the routine way of life. In the present article these ideas have been touched upon and various methods of environmental management described in brief. In addition what other Governmental agencies are required to do in order to effectively implement environmental management methods are briefly enlisted.

Blood Cholinesterase monitoring in spraymen involved in malathion spraying--a health protection measure.

The blood Cholinesterase (ChE) level of malathion in spraymen is continuously monitored through a "built-in warning system" existing under NMEP since the introduction of malathion spraying. The data available from the States of Maharashtra, Punjab and Gujarat revealed that, in spraymen of Punjab, the ChE level in 1988 and 1989 remained normal in about 99.8 per cent spray personnel, and in 1 out of 381 workers, the ChE level fell to 62.5 per cent during 1989. In Gujarat and Maharashtra, the normal level of ChE was maintained in nearly 88 and 98.4 per cent of spray personnel respectively during the spraying period. The ChE level fell to 62.5 per cent in 11.9 per cent of spray staff in Gujarat during 1987 and in 1.5 and 1.6 per cent persons during 1988 and 1989 respectively in Maharashtra. Only in three cases (0.07 per cent) out of 4,100 in Maharashtra showed depression in ChE to 50 per cent in 1988. In none of the above mentioned cases, there was any parasympathetic overstimulation or uneasiness, etc, even then they were withdrawn from spray and were given rest and where needed medical care.

Success of integrated methods of control of mosquitoes in India--a review.

The integrated methodology for the control of vectors of diseases as well as mosquitoes has become an accepted concept amongst the public health experts. The feasibility of adopting this approach in different situations for mosquito control as per field trials by various institutions has been reviewed in this article. This concept, to some extent, has been in vogue under National Malaria Eradication Programme since long in a practicable way. Satisfactory results have been obtained wherever this approach has been applied carefully. The applicability of the integrated control methodology is not difficult provided various methods to be integrated are chosen and utilized in a rational way. Thorough health education is a prerequisite to awaken the community to accept the methods as part and parcel of routine life.

Filariasis control in rural areas through detection and treatment with diethylcarbamazine.

A pilot study for control of bancroftian filariasis through detection and treatment of microfilaria (mf) carriers and filaria disease cases with Diethylcarbamazine (DEC) undertaken in the rural areas of Srikakulam and Vizianagaram of Andhra Pradesh showed that this chemotherapeutic method of control of filaria in rural areas is feasible and acceptable to society. During first round of detection and treatment 20,300 mf carriers (90.6 per cent of detected) and 6,588 disease persons (86 per cent of detected) in Srikakulam and 7,097 mf carriers (94.8 per cent of detected) and 1,436 disease persons (93.4 per cent of detected) in Vizianagaram were treated with DEC tablets. These areas were again surveyed after five years and detected cases were treated with DEC with coverage of treatment ranging from 82.3 per cent to 95 per cent for both mf & disease cases and decline in mf and disease rate was noted to be 52.4 per cent and 50.9 per cent respectively in Srikakulam and 42.2 per cent for mf rate in Vizianagaram. The mf reduction was appreciably high (50 per cent or more) in 11 PHCs of Srikakulam and 4 PHCs of Vizianagaram. The mf rate reduction was the highest in the age group of 1 to 4 year indicating that the transmission has been cut down significantly. The vector infection rate showed reduction by 50 per cent during second round of detection and treatment as compared to first round, indicating significant reduction in transmission potential.