Unexpected Rift Valley Fever Outbreak, Northern Mauritania

During September–October 2010, an unprecedented outbreak of Rift Valley fever was reported in the northern Sahelian region of Mauritania after exceptionally heavy rainfall. Camels probably played a central role in the local amplification of the virus. We describe the main clinical signs (hemorrhagic fever, icterus, and nervous symptoms) observed during the outbreak

Investigating avian influenza infection hotspots in old-world shorebirds

Heterogeneity in the transmission rates of pathogens across hosts or environments may produce disease hotspots, which are defined as specific sites, times or species associations in which the infection rate is consistently elevated. Hotspots for avian influenza virus (AIV) in wild birds are largely unstudied and poorly understood. A striking feature is the existence of a unique but consistent AIV hotspot in shorebirds (Charadriiformes) associated with a single species at a specific location and time (ruddy turnstone Arenaria interpres at Delaware Bay, USA, in May). This unique case, though a valuable reference, limits our capacity to explore and understand the general properties of AIV hotspots in shorebirds. Unfortunately, relatively few shorebirds have been sampled outside Delaware Bay and they belong to only a few shorebird families; there also has been a lack of consistent oropharyngeal sampling as a complement to cloacal sampling. In this study we looked for AIV hotspots associated with other shorebird species and/or with some of the larger congregation sites of shorebirds in the old world. We assembled and analysed a regionally extensive dataset of AIV prevalence from 69 shorebird species sampled in 25 countries across Africa and Western Eurasia. Despite this diverse and extensive coverage we did not detect any new shorebird AIV hotspots. Neither large shorebird congregation sites nor the ruddy turnstone were consistently associated with AIV hotspots. We did, however, find a low but widespread circulation of AIV in shorebirds that contrast with the absence of AIV previously reported in shorebirds in Europe. A very high AIV antibody prevalence coupled to a low infection rate was found in both first-year and adult birds of two migratory sandpiper species, suggesting the potential existence of an AIV hotspot along their migratory flyway that is yet to be discovered

Comprehensive Phylogenetic Reconstructions of Rift Valley Fever Virus: The 2010 Northern Mauritania Outbreak in the Camelus dromedarius Species

International audienceRift valley fever (RVF) is a mosquito-borne disease of domestic and wild ruminants caused by RVF virus (RVFV), a phlebovirus (Bunyaviridae). RVF is widespread in Sub-Saharan Africa. In September of 2010, an RVF outbreak occurred in northern Mauritania involving mass abortions in small ruminants and camels (Camelus dromedarius) and at least 63 human clinical cases, including 13 deaths. In camels, serological prevalence was 27.5-38.5% (95% confidence interval, n=279). For the first time, clinical signs other than abortions were reported in this species, including hemorrhagic septicemia and severe respiratory distress in animals. We assessed the presence of RVFV in camel sera sampled during this outbreak and generated whole-genome sequences of RVFV to determine the possible origin of this RVFV strain. Phylogenetic analyses suggested a shared ancestor between the Mauritania 2010 strain and strains from Zimbabwe (2269, 763, and 2373), Kenya (155_57 and 56IB8), South Africa (Kakamas, SA75 and SA51VanWyck), Uganda (Entebbe), and other strains linked to the 1987 outbreak of RVF in Mauritania (OS1, OS3, OS8, and OS9)

Investigating Avian Influenza Infection Hotspots in Old-World Shorebirds

Heterogeneity in the transmission rates of pathogens across hosts or environments may produce disease hotspots, which are defined as specific sites, times or species associations in which the infection rate is consistently elevated. Hotspots for avian influenza virus (AIV) in wild birds are largely unstudied and poorly understood. A striking feature is the existence of a unique but consistent AIV hotspot in shorebirds (Charadriiformes) associated with a single species at a specific location and time (ruddy turnstone Arenaria interpres at Delaware Bay, USA, in May). This unique case, though a valuable reference, limits our capacity to explore and understand the general properties of AIV hotspots in shorebirds. Unfortunately, relatively few shorebirds have been sampled outside Delaware Bay and they belong to only a few shorebird families; there also has been a lack of consistent oropharyngeal sampling as a complement to cloacal sampling. In this study we looked for AIV hotspots associated with other shorebird species and/or with some of the larger congregation sites of shorebirds in the old world. We assembled and analysed a regionally extensive dataset of AIV prevalence from 69 shorebird species sampled in 25 countries across Africa and Western Eurasia. Despite this diverse and extensive coverage we did not detect any new shorebird AIV hotspots. Neither large shorebird congregation sites nor the ruddy turnstone were consistently associated with AIV hotspots. We did, however, find a low but widespread circulation of AIV in shorebirds that contrast with the absence of AIV previously reported in shorebirds in Europe. A very high AIV antibody prevalence coupled to a low infection rate was found in both first-year and adult birds of two migratory sandpiper species, suggesting the potential existence of an AIV hotspot along their migratory flyway that is yet to be discovered

List of potential hotspots of AIV infection detected in our study.

<p>These sites correspond to sampling occasions (top) at which the number of AIV-positive birds was above the threshold number of birds for which the hypothesis that prevalence is lower than 10% could not be rejected (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0046049#pone-0046049-g002" target="_blank">Figure 2</a>). Sampling conducted in different years at the same sites during the same months and on the same species (below) detected a low number of AIV-positive birds.</p>a<p>. African jacana <i>Actophilornis africana</i>, Kittlitz's plover <i>Charadrius pecuarius</i>, Little stint <i>Calidris minuta</i>, Blacksmith lapwing <i>Vanellus armatus</i>, Slender-billed gull <i>Chroicocephalus genei</i>, Curlew sandpiper Calidris ferruginea, Wood sandpiper <i>Tringa glareola</i>.</p

Detection of potential hotspots of AIV infection in shorebirds sampled at various sites across Eurasian and Afro-tropical regions (<b>Figure 1</b>-B; and supporting information Table S2).

<p>The number of AIV-positive birds detected in relation to the number of birds sampled per sampling occasion is here compared to the threshold number of positive birds (solid line) below which the prevalence is unlikely (probability <0.05) to be greater than 10% for a sample of the same size. Points on or above the line represent potential AIV hotspots, i.e. sampling occasions (n = 5) for which the number of positive birds was too large for rejecting the hypothesis that prevalence could be >10% (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0046049#pone-0046049-t003" target="_blank">Table 3</a>). Only sampling occasions (n = 47) that had at least 28 birds sampled were considered in this analysis.</p

Mean seroprevalence of AIV antibodies among closely related shorebird species in relation to the mean latitude of their breeding range.

<p>Seroprevalence were measured in West Africa (the Banc d'Arguin, Mauritania and the Inner Niger Delta, Mali) and the Delaware Bay, USA (from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0046049#pone.0046049-Stallknecht1" target="_blank">[8]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0046049#pone.0046049-Brown2" target="_blank">[31]</a>) using the same commercial bELISA kit (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0046049#s2" target="_blank">Methods</a>). The mean species breeding latitude was computed from the northern and southern limits of the breeding distribution of the populations present at each site using distribution maps from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0046049#pone.0046049-Jourdain1" target="_blank">[22]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0046049#pone.0046049-Poole1" target="_blank">[32]</a>. Species include ruddy turnstone (Δ), red knot (□), dunlin (o), sanderling (◊), short-billed dowitcher (×), ruff and wood sandpiper (−). Error bars represent the binomial exact 95% confidence interval.</p