Basic reproduction number (R0), an epidemiological tool for prioritizing livestock diseases' An example of Karnataka

Abstract

Livestock diseases become burden to the dairy farmers and state animal husbandry departments, and causes huge economic loss. Basic reproduction number [R0], indicates the number of secondary cases in susceptible population from one diseased animal. In the present study, R0 was calculated by using 5 statistical methods for 13 livestock diseases, which was used to prioritize livestock diseases and calculated herd immunity threshold, vaccination coverage required. Time series data on livestock disease outbreaks, month, year, clinically diagnosed cases, death cases were collected from Department of Animal Husbandary and Veterinary Services. Govt. of Karnataka during the period 2000–18. The mean R0 values were >1 for bacterial (4), viral (5) and parasitic (4) diseases. The livestock diseases were prioritized for high transmission potential as haemorrhagic septicaemia [HS] (2.51) followed by Peste des petits ruminants [PPR] (2.22), black quarter [BQ] (1.89), foot-and-mouth disease [FMD] (1.71), theileriosis [TE] (1.70), enterotoxaemia [ET] (1.54), anthrax [AX] (1.48), sheep and goat pox [SGP] (1.44), rabies [RA] (1.39), babesiosis [BA] (1.38), bluetongue [BT] (1.31) and fasciolosis [FA] (1.27) based on mean R0 values for Karnataka. The herd immunity threshold was high for HS [60.2%] followed by PPR [55.0%], BQ [47.1%], FMD [41.5%] and other diseases. The vaccination coverage required showed highest levels for HS, followed by PPR, BQ, FMD, TE, ET, etc. Thus, R₀ values may be used for prioritizing livestock diseases by policy makers and for planning the necessary preventive measures. The herd immunity threshold and vaccination coverage obtained for livestock diseases will help in allocating the scarce resources for vaccination effectively and to prevent livestock diseases outbreaks in Karnataka.