Epidemiology, risk factor and R0 investigation of an outbreak of lumpy skin disease in cattle in Punjab, India

Abstract

Lumpy skin disease (LSD) is an emerging disease in India, causing substantial economic losses to the livestock industry. This study aimed to estimate epidemiologic parameters, including R₀, and risk factors associated with an LSD outbreak in cattle (November 2021—August 2022) in Punjab, India. Animals were unvaccinated, and the village’s animals were isolated due to district animal movement restrictions. Univariable regression analyses investigated the association of farm and animal level explanatory variables with disease outcome. The exponential growth (EG) method using the gamma-distributed serial intervals between cases was used to estimate the basic reproduction number (R₀). Buffalo (N = 603) in the village were not affected. The attack rate in cattle was 5.3 % (95 % CI 3.8–7.5), mortality rate 1.1 % (95 % CI 0.5–2.3), and case fatality rate 20 % (95 % CI 9.5–37.3). The odds of indigenous cattle being a case was higher than crossbred cattle (OR 3.9, 95 % CI 1.1–12.5, P = 0.01). Estimated animal-level R₀ was 1.82 (range 0.55–3.57; 95 % CI 0.01–7.83). Univariable logistic regression analysis identified significant risk factors at the farm-level including the number of cattle (OR 1.19, 95 % CI 1.03–1.43, P = 0.01), presence of blood sucking flies (OR 8.21, 95 % CI 2.11–31.92, P < 0.01) and ticks (OR 3.12, 95 % CI 1.03–9.52, P = 0.038). Therefore, prioritizing vaccination to cattle over buffalo during limited vaccination supplies and control measures for both direct and indirect transmission must be adopted in dairy farms, and monitoring R₀ could be used to determine the effectiveness of control measures either in the field or in LSD simulation models.