Transboundary Livestock Network in Africa: How Circulate Pathogens and Where to Act to Prevent the Epizootics Spread?

Abstract

Objectives: Transboundary animal diseases (TADs) of domestic ruminants are closely linked to livestock movements, consequently,
understanding these latter provides information on the pathogen's dissemination pathways. This descriptive study, using
the mapping and network analysis (NA) method, aims to characterize the cross-border mobility network of domestic ruminants
on the African continent, to understand how it works, to identify the main countries controlling livestock mobility, to deduct their
relationships with other countries, and finally, to highlight the articulation points of the network at which actions should be taken
to stop the epizootics spread.
Methodology: This is a synthetic, descriptive study, whose results make it possible to place it within the framework of epidemiological
surveillance with a continental scope, aiming to guide the efforts of the concerned authorities. Based on deep documentary
research, a total of 483 transhumant and commercial cross-border movements were identified. These movements were mapped
by the geographic information system (GIS) to reconstruct the network of international movements between countries. The most
regular movements, numbering 190 and constituting a more stable exchange network over time, were subjected to processing by
the NA method, to highlight different indicators that permit the characterization of the network. The results obtained were then
compared with health data on the distribution of the five main notifiable animal diseases circulating in the African continent in
addition to rinderpest. All analyses were conducted using “R” software.
Results: The centrality indicators enabled the identification of the main central countries, including the most active and unavoidable
ones that contribute to diseases spread in Africa. They also made it possible to quantify their importance in the influence of
movement, while the global measurements and network cohesion parameters showed that the latter is vulnerable to the spread of
epizootics. This study revealed a strong livestock exchange relationship between 25 African countries, extending from nations on
the Atlantic Ocean coasts to those of the Indian Ocean ones, which were found to be the most vulnerable to the establishment
of contagious diseases. Different communities of countries whose livestock movements appear to be very cohesive and which
presage significant mutual contamination have been highlighted. Certain African countries have proven to be key points in the articulation
of flows between different countries and different regions and contribute significantly to the dissemination of diseases
between the different regions of the continent. Accordingly, key countries where actions should be taken to stop the epizootics
spread were identified.
Conclusion: The results allowed a better understanding of diseases diffusion pathways through livestock movements across Africa
and highlighted the main movement focal points which represent a high-risk of diseases spread, as well as the capacity to influence
their diffusion through the control of the animal’s movement or the deployment of prophylactic actions at their level.