Drivers for the Reporting of Highly Fatal Animal Disease Reporting: A Modelling Study Based on Global Outbreak Data on African Swine Fever and Highly Pathogenic Avian Influenza

Abstract

Background & Aims of Study

The early detection and reporting of pathogen introduction into livestock populations are key elements for successful animal and zoonotic disease surveillance and control. Here, we investigated the factors influencing the time between pathogen introduction and reporting for two highly fatal animal diseases: African swine fever (ASF) and highly pathogenic avian influenza (HPAI).

 

Methods & Results

We constructed a comprehensive set of mathematical models assuming different relationships between the number of dead animals at reporting (i.e. when an outbreak was first reported) and herd size, taking into account herd types, seasons, and geography. These models were fitted to ASF and HPAI outbreak data reported to the World Organisation for Animal Health (WOAH) by WOAH members and non-members. All models assumed that the likelihood of observing the number of dead animals at reporting followed a negative binomial distribution.

For both ASF and HPAI, the best-fitting model indicated that the number of dead animals at reporting increased proportionally to herd size (i.e., reporting slope). However, above a certain herd size, it reached a plateau (i.e., reporting threshold). These dynamics, particularly the reporting threshold, varied significantly between herd types and, within the same herd types, countries, including those on the same continents. While the number of dead animals at reporting significantly varied by season for HPAI, it was not the case for ASF. Finally, the number of dead animals at reporting showed high overdispersion, suggesting large variations in the time between pathogen introduction and reporting among herds in the same strata.

 

Implications

Our modelling approach, combined with global notification data, highlights the complex dynamics of ASF and HPAI detection and reporting. It suggests that beyond a certain herd size, the number of dead animals at reporting remains stable despite an increase in the number of susceptible animals. However, the high levels of variation in the reporting threshold emphasise the necessity of joint efforts to minimise the global spread of these fatal diseases. Finally, our modelling approach could be adopted for other notifiable animal diseases (e.g. using the number of cases at reporting for non-fatal diseases) at the global and national levels.

Note: This conference abstract was presented at the 9th International Conference on Infectious Disease Dynamics organized by the journal Epidemics. This abstract has not been screened by SSRN for potential for public harm and should not be used to inform any clinical decision making. No competing interests or funding statements have been declared.