Optimization of Intervention Strategies

Programmes for the control of vector borne diseases need to be evaluated for their effectiveness and improvement. Cost minimization with the same level of effectiveness and improved effectiveness with the same level of inputs are the two methods to achieve the desired level of impact.


Transmission of filariasis can be interrupted by controlling

  • vector

  • protecting individuals

  • or controlling the parasite (chemotherapy) in the human host.

Selective Chemotherapy:

  • A single 12-day course of DEC (6mg/kg body wt/day)could clear parasitaemia in 62% of Wuchereria bancrofti mf carriers. The remaining required a maximum of 4 such courses for complete clearance of mf. The clearance was dependent on initial mf density, but independent of age and gender. In the case of brugian filariasis, the total clearance with single course of DEC was observed in 88% of the cases, indicating that the a better response to DEC than Wuchereria bancrofti The compliance of treatment was 73.9% of in the case of patients with Brugia malayi whereas it was lower (61.6%) in Wuchereria bancrofti. Side reaction was the limiting factor for the compliance. At community level the selective therapy followed by screening of about 80% of the population could result in about 50% reduction in mf prevalence after one month of intervention.

  • Followup of mf carriers of Brugia malayi after treatment with three different daily regimens of DEC indicated that 6mg daily dose for 12 days was ideal in terms of compliance, clearance and recurrence of mf.

Mass chemotherapy:

  • Four rounds of mass semi-annual single dose DEC against bancroftian filariasis with a coverage ranging from 82-92% showed a reduction of about 62% in mf prevalence and 74% in mf intensity. There was 50% reduction in vector infectivity at the end of fourth round of treatment.

  • Relatively a higher reduction in mf prevalence (60%) was recorded with four rounds of mass single dose ivermectin when compared to that of DEC (49%). The reduction in mf intensity was 95% for the former and 70% for the latter. The impact of two rounds of combination of DEC and ivermectin is comparable to that of four rounds of either of the drugs alone. Vector infectivity rate was reduced by 65% and 70% in ivermectin and DEC groups of villages respectively after four rounds, while it was 70% after two rounds of combination treatment.

  • Two rounds of mass annual single dose with DEC in controlling brugian filariasis showed that with a coverage of 59 and 62%, the mf prevalence was brought down from 4.9 to 1.2% (75% reduction). mf intensity was reduced by 81%. The infectivity potential of human population declined from 2.1 to 0.5 (89% reduction). Four rounds of semi-annual single dose showed significantly a higher reduction in mf prevalence (90%) and mf intensity (98%) compared to mass annual single dose DEC.

Mass medicated Salt

  • Monthly follow-up of a cohort of mf carriers of W. bancrofti following DEC medicated salt (0.2% w/w) showed that continuous intake of DEC salt for a minimum period of 180 days is necessary for complete clearance of mf. The cost of salt with DEC powder and fortification was calculated to be Rs. 5.59 per Kg. Daily per capita consumption of salt was estimated to be 13 gms.

  • Medicated salt distribution through public distribution system could reach only 35% of the 17 lakh population covered under the mass programme in Kanyakumari district. Low dosage of DEC medicated salt for period of 44 months and two rounds of mass annual single dose DEC resulted in about 83% reduction in mf prevalence

  • A study in B. malayi endemic area (population 27000) in Kerala showed that use of DEC medicated salt for a period of one year (coverage=74.5%) could reduce the mf prevalence from 1.4 to 0.1%. Vector infection was brought down to zero six months after the introduction of this intervention from the pre control level of 2.96% and maintained thereafter.

 

Morbidity mamagement:

  • In a placebo controlled clinical field based trial, the efficacy of foot care, DEC, oral penicillin and combination of both drugs was evaluated for prevention of ADL in lympho-edema pa-tients. Foot care alone is adequate for manage-ment at community level. Therefore foot care can form an im-portant component of morbidity management strategy.

  • DEC and supporting therapy (anti-inflammatory, antibi-otic, diuretic, crepe bandage) resulted in reduction of oe-dema (35%) in bancroftian filariasis. In the case of bru-gian filariasis, the response to therapy was relatively higher (36-70%) in terms of reduction of oedema.
     

  • Surgical procedures namely, lymphonodovenous shunt (LNVS) and omento plasty (OPL) were evaluated for their effectiveness in the management of bancroftian filarial lymphoedema. Majority of cases (64%) responded in terms of reduction in oedema assessed on 7th post-opera-tive day. This reduction was sustained only in 25% of the cases by the end of one year. Patients recording initial oe-dema volume of 2 litres or more best suited for LNVS. Post-operative ADL attacks resulted in failure of the shunt. OPL was attempted in cases, which failed to re-spond to LNVS. Although oedema reduction was above 25% in most cases, this was not suitable as is post-surgical incisional hernia was common. LNVS is recommended.


Implementation of strategy:

  • Under the mass annual single dose DEC programme, drug delivery has been the major issue to be resolved to achieve the desired level of control. Different drug delivery approaches have been developed. Researcher designed drug delivery strategy was implemented through trained community volunteers and primary health care system. Coverage and compliance was relatively higher under community approach. Centralized drug distribution through anganwadi centres and schools achieved maximum coverage.

  • When the entire responsibility of planning and implementation of mass single dose DEC distribution was given to the drug distributors, primary health care system showed to be better in terms of coverage, compliance and community perception. The per capita cost of the programme was Rs. 1.35 for the primary health care approach while it was Rs. 2.23 for community approach under which training cost constituted about 48% of the total cost.

  • Drug delivery through workers of Integrated Child Development Scheme in Pondicherry could achieve 86% of coverage with supervised administration of about 10% of the eligible population. Side reactions were minimal (0.74%). Vector infection was brought down from 3.3% to 2.6% following three rounds of treatment.

Cost analysis of control strategies:

  • Economic analysis of mass annual single dose DEC to control lymphatic filariasis through the primary health care system showed that the per capita cost additional to the existing health care system was Rs. 0.97 per round. Drug was the major cost component and drug distribution was the expensive activity under the programme. The annual requirement of resources to protect the population under risk in India is estimated to be Rs. 487.9 million.

Malaria control in a tribal area through strengthening the Traditional Health Care Personnel

  • A drug delivery system has been developed for malaria control by involving the traditional health healers (Disaris) in treating fever cases with chloroquine and referring the severe/complicated cases to PHCs. This has been demonstrated in one PHC area inhabited by 'Koya' tribals and is being extended to other tribal areas in Orissa.


    • Since majority of disaris have no formal education, they were trained to provide treatment with the help of a pictorial guide and pre-packed tablets. Disaris could follow the recording system and in a period of 9 months (Apr - Dec, 1999), they treated 27021 cases of all age groups. Most of them administered correct dosage and reporting of cases was regular. A total of 29 severe/complicated cases were referred to the PHC. The number of fever days (number of days, a person suffering from malaria fever without treatment) has been reduced from 5-15 days to 2-3 days.

Last Updated on : 07/04/2014