Leprosy is not yet eradicated because
Ans is 'a' i.e. No effective vaccine Both "No Effective Vaccine" and "Long incubation period" are the reason behind not being able to fully control Leprosy. But when it comes to eradication, "No Effective Vaccine" is correct answer because only disease eradicated (small pox) was because of effective vaccine.About leprosy Park writes- "Although significant progress has been made in controlling the disease and reducing the disease burden, much remains to be done in order to sustain the gains and further reduce the impact of the disease...One of the long-term needs is to develop reliable diagnostic tests for early diagnosis and an effective vaccine for the prevention of leprosy."The only disease which has been eradicated till now is smallpox. There were many advantageous features of the disease coupled with a highly effective, heat stable vaccine which led to its eradication.The other disease which is a very potential candidate for eradication is Polio. It does not have advantageous features like those possessed by Small pox, still it has a very effective vaccine.Small pox was eradicated and Polio is likely to be eradicated because of the massive global immunization programs launched by WHO.This suggests that most probable reason for non-eradication of leprosy could be absence of an effective vaccine. Other reasons which are also culprits are - long incubation period, highly infectious, large number of infective subclinical cases, difficult to diagnose and animal reservoir.Various definitions:Control:The reduction of disease incidence, prevalence, morbidity or mortality to a locally acceptable level as a result of deliberate efforts; continued intervention measures are required to maintain the reduction.Example: diarrhoeal diseases.Elimination:Reduction to zero of the incidence of a specified disease in a defined geographical area as a result of deliberate efforts; continued intervention measures are required.Example: neonatal tetanus, measles, poliomyelitis.Eradication:Permanent reduction to zero of the worldwide incidence of infection caused by a specific agent as a result of deliberate efforts; intervention measures are no longer needed.Example: smallpox.Extinction:The specific infectious agent no longer exists in nature or in the laboratory.Example: none. Factors associated with potential for eradication of a communicable disease:There are many factors but the three factors considered to be of primary importance are:An effective intervention is available to interrupt transmission of the agent;Practical diagnostic tools with sufficient sensitivity and specificity are available to detect levels of infection that can lead to transmission; andHumans are essential for the life-cycle of the agent, which has no other vertebrate reservoir and does not amplify in the environment.Factors Associated with Potential for Eradication of a Communicable Disease Factors Associated with the DiseaseEase of diagnosis and treatment Low prevalence of subclinical disease High disease burden and economic impact Immunity is long term or lifelong Disease cannot be reactivated Disease has predictable seasonalityFactors Associated with the Etiologic AgentLack of an animal reservoir or vectorOnly one causative agent or serotypeShort incubation periodFactors Associated with the Host or Target PopulationCorrelates or protection can be demonstratedHost cannot be reinfected with the agentHost cannot shed the organism once infection is resolvedPublic acceptance of the vaccine and other control measures is highFactors Associated with the VaccineCan confer long-lasting protection in a few injectionsMinimal handling and storage requirements (e.g., cold chain)Simple administrationCan be administered simultaneously with other vaccines or adapted to schedules and timing of the national childhood immunization programsFew short- or long-term adverse effectsLow cost to produce and purchase vaccine Epidemiological factors which led to the eradication of smallpox are:No known animal reservoir.No long-term carrier of the virus.Life-long immunity, after recovery from the disease.The detection of the cases was relatively simple as the rashes were characteristic.Persons with subclinical infection did not transmit the diseaseHighly effective, heat stable vaccine, easily administrable and provides long term protection.International cooperation
No effective vaccine
Highly Infectious but low pathogenicity
Only humans are reservoir
Long incubation period
Communicable Diseases