Ovine Network in Morocco: Epizootics Spread Prevention and Identification of the At-Risk Areas for “Peste des Petits Ruminants” and “Foot and Mouth Disease”

Abstract

Objectives: Because contagious diseases spread among domestic ruminants are closely linked to livestock movements, the present
study aims to analyze the sheep movements network in Morocco during its two periods of regular movements and more intense
movements in the festive period, to map it and identify central points and movement structures that influence its functioning, but
also to highlight the articulation points at which actions should be taken to prevent or control the epizootics spread. The aim of this
study is also to produce risk maps for introduction and exposure to Peste des Petits Ruminants (PPR) and Foot-and-Mouth Disease
(FMD), to guide the epidemiological surveillance efforts.
Methodology: This is a descriptive study, and which results placed it within the framework of epidemiological surveillance on a national
scale. A two-stage random sampling was carried out in 52 provinces belonging to regions with very high sheep populations and
whose municipalities have been subject to previous outbreaks of diseases, notably PPR and FMD. A sampling proportion of 25%
of municipalities was adopted for each province. Within each commune, sheep farms and markets, if existed, were drawn randomly.
In the absence of a breeder database, the sample relating to farms was carried out by representativeness of the sheep population for
each municipality. The sample relating to markets was carried out as representative of the trading volume of the markets. An “Origindestination”
survey concerning the origin and destination of sheep routes made by breeders or traders was deployed in the field. The
results of this survey were entered into a database and then mapped by the Geographic Information System (GIS) to distinguish
regular movements from periodic ones. After data reorganization into two movement periods, the database was processed by the
network analysis method to highlight the main central points and the main structures that condition the movement. All these analyses
were conducted using the “R” software. The risk analysis of introduction and exposure to PPR and FMD was also carried out. The
results obtained were compared with the epidemiological data of these diseases.
Results: The sheep movement network in Morocco is much more sensitive to the epizootics spread during intense movement periods
corresponding to preparation for the festivities, namely Aid al Adha than during regular periods. The centrality of certain municipalities
exposes them to the risk of diseases during periods of intense movement, while others appear exposed during both periods. This
study has traced back the different regions by cohesive structures of movement which condition the circulation of disease pathogens
across the country and which strongly contribute to their diffusion across regions which are sometimes very distant geographically.
However, the movement articulation municipalities “cutpoints”, that allow to neutralize flows between these structures have been
identified. The introduction and exposure risk analysis provided satisfactory results for the PPR and FMD about their validation by
health epidemiological data related to outbreaks. Thus, 82.88% and 67.39% of outbreaks were included in the high to very high risk
strata respectively for PPR and FMD.
Conclusion: This study’s results allowed a better understanding of sheep movements extent and articulation at the national level during
periods of regular movements and periods of more intense movements and consequently a better knowledge of the pathogen's
dissemination paths. Highlighting “cutpoint” municipalities in addition to the at-risk municipalities for introduction and exposure to
diseases represents valuable guidance for targeted actions that would contribute to remobilizing and optimizing available surveillance
resources more efficiently.