Epidemiological Definitions

These definitions and indices are important in epidemiological surveillance and in planning the control strategy for malaria.

Endemic Malaria: Constant incidence over a period of many successive years in an area.

Epidemic Malaria: Periodic or occasional sharp increase of malaria in a given indigenous community.

Stable Malaria: Amount of transmission is high without any marked fluctuation over years though seasonal fluctuations occur.

Unstable Malaria: Amount of transmission changes from year to year.

Vulnerability: Either proximity to malarious areas or liability to frequent influx of infected people or anophelines.

Receptivity: Habitual presence of vector anophelines or existence of ecological factors.

Clinical Cure: Relief of symptoms without complete elimination of parasites.

Radical Cure: Elimination of parasites actually responsible for attack of malaria.

Recrudescence: Renewed clinical activity seen during the first 8-10 weeks after primary attack (short term relapse).

Recurrence: Renewed clinical activity seen around 30th – 40th week following primary attack (long term relapse)

Clinically Latent: Symptom less phase between primary attack and relapse with splenomegaly, no parasite seen in peripheral smear.

Insecticidal Resistance: Development of resistance i.e. ability in strains of insects to tolerate doses of toxicants which would prove lethal to the majority of the insect population of the same species.

Epidemiological Indices:

Annual Blood Examination Rate (A.B.B.R.) = Smears examined in a year X 100 / Total population.

Annual Parasitic Incidence (A.P.I.) = Total no. of positive slides for parasite in a year x 1000 / Total population.

Annual Falciparum Incidence = Total positive PF in a year x 1000 / Total population.

Slide Positivity Rate (S.P.R.) = Total positive x 100 / Total slides examined.

Slide Falciparum Rate (S.F.R.) = Total positive PF x 100 / Slides examined.

P. falciparum Percentage (PF %) = Total positive for P. falciparum x 100 / Total positive for MP

Entomological parameters:

Adult vector density – Man hour hand captures (per man hour density) = No. of mosquitoes collected/ No. of man hours spent in search

Sporozoite Rate (%) for each species = (No. of positive for sporozoites/ No. dissected) x 100

(I sincerely thank Dr. P.P. Venugopalan, Former Medical Superintendent, Attavar Hospital and Professor and Head of Community Medicine, Kasturba Medical College, Mangalore for his contribution)

©malariasite.com ©BS Kakkilaya | Last Updated: June 7, 2016