Risk factors, logistic model, and vulnerability mapping of lumpy skin disease in livestock at the farm level in Indragiri Hulu District, Riau Province, Indonesia, in 2022

Clinical and molecular description of natural infections with an Asian strain of lumpy skin disease virus in Bos indicus

Knowledge of the dynamic of clinical infections with Asian strains of LSD virus (LSDV) in Bos indicus is scarce. This study reports on the clinical, serological and molecular features of natural infections with LSDV in B. indicus during the first outbreak in Yogyakarta, Indonesia, 2023. Eleven Peranakan ongole (PO) breed cattle with multiple skin lumps were included in the study. Data was collected on lump progression, rectal temperature, anorexia, lameness and oedema, along with serum samples, on five sampling points at four days intervals. Seroconversion was detected using an ELISA, viral DNA in sera was detected using PCR and a phylogenetic tree of the viral DNA sequences was constructed. A Kendall's tau-b bivariate correlation was conducted to test correlations between variables observed. Results showed that, after lumps, lameness was the most frequently observed clinical feature (9/11), followed by oedema, anorexia (both 6/11) and fever (5/11). Lump presence was strongly correlated with lameness and moderately correlated viral DNA load in sera (r = 0.61, P < 0.01, and r = 0.51, P < 0.01), anorexia was moderately correlated with the course of oedema (r = 0.45, P < 0.01). Younger animals were ill for longer than older individuals. Antibody levels increased on Day eight but declined rapidly yet, remained above the threshold, on day 16. The detection of viral DNA in sera was of short duration and intermittent in a few animals; the virus was closely related to Clade 2 of LSDV. This study provides preliminary knowledge of features of LSDV infection in Indonesia for further studies on vaccination, clinical treatment and prognosis of the disease.

Prevalence of lumpy skin disease and associated risk factors in beef cattle in Rembang Regency, Central Java, Indonesia

Background and Aim

Lumpy skin disease (LSD) is an economically devastating infectious disease in cattle. Rembang Regency, located in Central Java, Indonesia, has suffered over 3800 cases of LSD and 75 deaths since early 2023. This region holds the 4th number of most populous beef cattle producers in Central Java. However, until now, there have been no reports on the prevalence and risk factors related to LSD in beef cattle in Rembang Regency, Central Java, Indonesia. Therefore, this study aimed to estimate the prevalence of LSD and identify associated risk factors in Rembang Regency, Central Java, Indonesia.

Materials and Methods

The sample size was 458 cattle, which were determined using the formula (n = 4PQ/L2) and two-stage random sampling technique, were examined physically through LSD typical clinical signs, namely distinguishing firm, circumscribed, few (mild forms) to multiple (severe forms) skin nodules. Structured questionnaires and interviews with farm owners were used to identify risk factors. The data related to the LSD were analyzed using descriptive statistics, bivariate analysis with Chi-square and odd ratios, and multivariate logistic regression to retrieve the logit model. All data were compiled in Microsoft® Excel, while analyses were performed using SPSS version 26.0.

Results

The prevalence of LSD in Rembang Regency was 28.2%. There were 11 significant risk factors associated with LSD. The multivariate analysis indicated that risk factors significantly contributing to LSD were knowledge of LSD transmission (p = 0.035, Odds ratios [OR] = 2.933), waste management (p = 0.014, OR = 4.015), rainy season (p = 0.019, OR = 2.944), and proximity between farms (p = 0.003, OR = 4.506). The logistic regression model analysis was as follows: LSD (Y) = -6.719 + 1.041 (knowledge of LSD transmission) + 1.390 (waste management) + 1.080 (rainy season) + 1.505 (proximity between farms).

Conclusio

n: This study revealed a significant prevalence of LSD in Rembang Regency, Central Java, Indonesia, with 28.2% of cattle affected. Key risk factors contributing to LSD outbreaks were insufficient knowledge of transmission, inadequate waste management, seasonal rainfall, and close proximity between farms. These findings emphasize the need for targeted interventions, including educational programs for farm owners, improved waste management practices, and strategies to mitigate seasonal and spatial risks to control LSD in the region effectively.

A systematic review of epidemiological modelling in response to lumpy skin disease outbreaks

Lumpy skin disease (LSD) is an infectious disease currently spreading worldwide and poses a serious global threat. However, there is limited evidence and understanding to support the use of models to inform decision-making in LSD outbreak responses. This review aimed to identify modelling approaches that can be used before and during an outbreak of LSD, examining their characteristics and priorities, and proposing a structured workflow. We conducted a systematic review and identified 60 relevant publications on LSD outbreak modelling. The review identified six categories of question to be addressed following outbreak detection (origin, entry pathway, outbreak severity, risk factors, spread, and effectiveness of control measures), and five analytical techniques used to address them (descriptive epidemiology, risk factor analysis, spatiotemporal analysis, dynamic transmission modelling, and simulation modelling). We evaluated the questions each analytical technique can address, along with their data requirements and limitations, and accordingly assigned priorities to the modelling. Based on this, we propose a structured workflow for modelling during an LSD outbreak. Additionally, we emphasise the importance of pre-outbreak preparation and continuous updating of modelling post-outbreak for effective decision-making. This study also discusses the inherent limitations and uncertainties in the identified modelling approaches. To support this workflow, high-quality data must be collected in standardised formats, and efforts should be made to reduce inherent uncertainties of the models. The suggested modelling workflow can be used as a process to support rapid response for countries facing their first LSD occurrence and can be adapted to other transboundary diseases.

The first outbreak of Lumpy Skin Disease in Indonesia

This study describes the first outbreak of Lumpy Skin Disease (LSD) in cattle in the Bengkalis region, Indonesia, and vaccination to control the epidemic. Data on the outbreak and vaccination was obtained from the local veterinary authority of the Bengkalis region, Indonesia. Climatological data was provided by the Meteorological, Climatological, and Geophysical Agency of Riau Province. Over the 5.5 months, the outbreak caused 10.4% (94/906) morbidity and 0.6% (6/906) mortality of cattle on infected farms. Temporally, three epidemic waves occurred during the outbreak period. Villages with cattle populations of > 150 animals (n = 36) were 5.3 times more likely to be infected with LSD compared to villages with smaller cattle populations (n = 107) (CI: 2.56-10.90, P < 0.01). The vaccination campaign covered 43.8% of cattle in villages within a 10 km radius of the cases. However, vaccination in villages with larger cattle populations (n = 29) was 0.63 less likely to cover 50% of the cattle populations compared to villages with smaller cattle populations (n = 41) (CI: 0.39-1.02, P = 0.05). By the time the first two and the major waves ceased, vaccination had covered only 0.0% (n = 6036), 27.8% (n = 6,036) and 9.7% (n = 5,697) of the cattle in the 10 km radius of the respective spatial clusters. The outbreak was statistically associated with rainfall and its interaction with temperature (F(2, 13) = 5.822, R2 = 0.47, P = 0.016). This study indicates that the LSD outbreak had low morbidity and mortality. Despite the low vaccination rate, the outbreak ceased, possibly due to plummeting of the abundance of insect vectors.

Analysis of factors associated with the first lumpy skin disease outbreaks in naïve cattle herds in different regions of Thailand

Introduction

Thailand experienced a nationwide outbreak of lumpy skin disease (LSD) in 2021, highlighting the need for effective prevention and control strategies. This study aimed to identify herd-level risk factors associated with LSD outbreaks in beef cattle herds across different regions of Thailand.

Methods

A case-control study was conducted in upper northeastern, northeastern, and central regions, where face-to-face interviews were conducted with farmers using a semi-structured questionnaire. Univariable and multivariable mixed effect logistic regression analyses were employed to determine the factors associated with LSD outbreaks. A total of 489 beef herds, including 161 LSD outbreak herds and 328 non-LSD herds, were investigated.

Results and discussion

Results showed that 66% of farmers have operated beef herds for more than five years. There were very few animal movements during the outbreak period. None of the cattle had been vaccinated with LSD vaccines. Insects that have the potential to act as vectors for LSD were observed in all herds. Thirty-four percent of farmers have implemented insect control measures. The final mixed effect logistic regression model identified herds operating for more than five years (odds ratio [OR]: 1.62, 95% confidence interval [CI]: 1.04-2.53) and the absence of insect control management on the herd (OR: 2.05, 95% CI: 1.29-3.25) to be associated with LSD outbreaks. The implementation of insect-vector control measures in areas at risk of LSD, especially for herds without vaccination against the disease, should be emphasized. This study provides the first report on risk factors for LSD outbreaks in naïve cattle herds in Thailand and offers useful information for the development of LSD prevention and control programs within the country's context.