Ecological Modeling of the Spatial Distribution of Wild Waterbirds to Identify the Main Areas Where Avian Influenza Viruses are Circulating in the Inner Niger Delta, Mali

Abstract

Predicting areas of disease emergence when no epidemiological data is available is essential for the implementation of efficient surveillance programs. The Inner Niger Delta (IND) in Mali is a major African wetland where >1 million Palearctic and African waterbirds congregate. Waterbirds are the main reservoir of Avian Influenza Viruses (AIV). Our objective was to model their spatial distribution in order to predict where these viruses would be more likely to circulate. We developed a generalized linear model (GLM) and a boosted regression trees (BRT) model based on total aerial bird counts taken in winter over 6 years. We used remotely sensed environmental variables with a high temporal resolution (10 days) to predict the spatial distribution of four waterbird groups. The predicted waterbird abundances were weighted with an epidemiological indicator based on the prevalence of low pathogenic AIV reported in the literature. The BRT model had the best predictive power and allowed prediction of the high variability of waterbird distribution. Years with low flood levels showed areas with a higher risk of circulation and had better spatial distribution predictions. Each year, the model identified a few areas with a higher risk of AIV circulation. This model can be applied every 10 days to evaluate the risk of AIV emergence in wild waterbirds. By taking into account the IND's ecological variability, it allows better targeting of areas considered for surveillance. This could enhance the control of emerging diseases at a local and regional scale, especially when resources available for surveillance programs are scarce.

Characterizing the interface between wild ducks and poultry to evaluate the potential of transmission of avian pathogens

“…One would expect birds from different family groups to congregate on this pond with other groups. Furthermore, the behaviour of the tagged comb ducks was in compliance with what is known about their ecology and what local hunters reported during our field work: they congregated on the remnant water bodies during the dry season and performed a regional movement to reach different breeding grounds during the rainy season [20,28]. That is why we believe these results can be extrapolated to other wild ducks in the study area.…”

Circulation of avian influenza viruses in wild birds in Inner Niger Delta, Mali

“…This massive arrival of Eurasian migrants is followed during the second half of their wintering period by the concentration of waterbirds on remnant water bodies because of decreasing water levels and the reduction in the surface of wetland habitat (Figure 1B,E). These factors increase the bird density and as a consequence the potential AIV transmission through a higher contact rate between wild birds 10 . Conversely, most Afro‐tropical waterbirds disperse after the onset of the rainy season (in July) to breed outside of the IND, leading to a decrease in the local host density.…”

Risk factor modelling of the spatio-temporal patterns of highly pathogenic avian influenza (HPAIV) H5N1: A review

“…Data on their distribution in space and time are hence difficult to obtain at high resolution. Furthermore, although some sites are known to harbour large wintering populations, the precise locations where birds will actually stay may vary from year to year, depending on the specifics of the water level and food availability (33). One can then only predict areas where the birds are likely to be, rather than where they actually are (33).…”