The Spatial Organization of Species

<div><p>Letters represent different PID species. Numbered rectangles represent different countries or areas.</p> <p>(A) Nested organization of species. Applying Diamond's theory, we here distinguish (1) “high-S” species, like species E, which are exclusively confined to the most species-rich communities; and (2) “tramps,” like species A, which occur mostly in richer communities but also in species-poor communities (e.g., measles, which is found in virtually every country). Thus, this nested pattern implies that some pathogens are restricted to the tropics, while others, more ubiquitous species, are widely and regularly distributed all over the world.</p> <p>(B) Random distribution of species, where no spatial organization occurs (see also <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.0020141#s4" target="_blank">Materials and Methods</a>).</p></div

The Latitudinal Gradients of PID Species

<div><p>(A) Relationship between PID species richness and latitude across the two hemispheres. Linear relationships between PID species richness and latitude (dotted lines) are highly significant (<i>F</i> = 12.29, <i>df</i> = 29, <i>p</i> = 0.0015 and <i>F</i> = 18.01, <i>df</i> = 130, <i>p <</i> 0.0001 for Southern and Northern hemispheres, respectively). No difference in disease species richness with latitude across the two hemispheres was observed (interaction: <i>F</i> = 2.68, <i>df = 159</i>, <i>p</i> = 0.1036). Residuals of PID species richness on the <i>y</i> axis were extracted from minimal models controlling for the effects of confounding factors on PID species diversity estimates (see <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.0020141#s4" target="_blank">Materials and Methods</a>). Locally weighted regression (tension 0.5) did not change the general linear shape. Latitude is expressed in minute degrees.</p> <p>(B) Presence/absence matrix for the 229 distinct PID species across the hemispheres. The figure was generated by the Nestedness Temperature Calculator (see <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.0020141#pbio-0020141-Atmar1" target="_blank">Atmar and Patterson 1995</a>). The distribution is nonsymetrical because of the 224 studied countries, 172 countries are found in the Northern hemisphere versus only 52 in the Southern one. (B) indicates that PID species diversity decreases as one moves northwards or southwards from the equator. The black exponential curves are the occurrence boundary lines (see <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.0020141#s4" target="_blank">Materials and Methods</a>). The color scale indicates the nonuniform probability of state occupancy among all of the cells of the matrix, i.e., the probability of encountering a species as function of its position in the matrix. Black cells are highly predictable presences, whereas red cells are unexpected presences.</p> <p>(C) Monte Carlo–derived histogram after 1,000 permutations. The histogram represents the 1,000 values obtained after Monte Carlo permutations. The average theoretical value under the null hypothesis is compared to our real value, to assess the likelihood that the parent matrix was nonrandomly generated. The probability is highly significant (<i>p</i> < 0.0001), confirming that the spatial organization of PID species richness on the largest scale matches the nested species subset hierarchy illustrated in <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.0020141#pbio-0020141-g001" target="_blank">Figure 1</a>A. The symmetrical Gaussian distribution indicates that 1,000 permutations are enough to obtain reliable variance estimates for probability calculations.</p></div

The “Meningitis Belt” in West Africa

<p>Modified from the WHO [<a href="http://www.plosmedicine.org/article/info:doi/10.1371/journal.pmed.0020006#pmed-0020006-b09" target="_blank">9</a>].</p

The Seasonal Periodicity of Meningitis Cases

<p>Mean seasonal pattern of the number of cases of MCM over the 1994–2002 period in standardized anomalies (bars). The red curve represents the same evolution, but in composite mean, using the week of epidemic onset as the reference date, <i>W</i>_o, each year. Time series in red is shown from “<i>W</i>_o − 3 wk” to “<i>W</i>_o + 30 wk.”</p

The Onset of Epidemics and the Winter Maximum

<p>Scatter plot of the week of epidemic onset and the week of winter maximum over the 1994–2002 period.</p

Kaplan-Meier survival curves for <i>Abramis brama</i>, <i>Rutilus rutilus</i> and <i>Cyprinus carpio</i> following infection with <i>Sphaerothecum destruens</i>.

<p>Cumulative proportion of (A) Bream <i>Abramis brama</i>, (B) Roach <i>Rutilus rutilus</i> and (C) Carp <i>Cyprinus carpio</i> surviving following exposure to <i>S. destruens</i>. Treatment fish (solid line) were exposed to an average concentration of 8.6×10⁴<i>S. destruens</i> spores ml⁻¹ whilst control fish (dotted line) were sham exposed. Time: days post exposure.</p

GenBank sequences <i>Sphaerothecum destruens</i> prevalence values used in genetic and susceptibility distances.

<p>Mean prevalence was calculated and used where multiple prevalence values were available for a species. The infection method used is also provided.</p><p>(*) Current study.</p

Host phylogeny and susceptibility to <i>Sphaerothecum destruens</i>.

<p>Genetic distance between all known susceptible species to <i>S. destruens</i> was plotted against the susceptibility distance to <i>Sphaerothecum destruens</i> for all the species combinations. The two families, <i>Cyprinidae</i> (□) and <i>Salmonidae</i> (♦) show different relationship patterns between genetic and susceptibility distances. Genetic distances were based in the pairwise analysis of ten Cytochrome b sequences. Analyses were conducted using the Tajima-Nei <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0036998#pone.0036998-Tajima1" target="_blank">[30]</a> method in MEGA4 <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0036998#pone.0036998-Tamura1" target="_blank">[31]</a>. All positions containing gaps and missing data were eliminated from the dataset. There were a total of 249 positions in the final dataset.</p

Mortality pattern in <i>Abramis brama</i> as a result of infection with <i>Sphaerothecum destruens</i>.

<p>The cumulative percentage mortality in the treatment groups (n = 60 individuals in total) and daily mortalities are presented for 26 days post exposure with <i>S. destruens</i>.</p

Sampling strategy for the treatment groups <i>Abramis brama</i>, <i>Cyprinus carpio</i> and <i>Rutilus rutilus</i>.

<p>List of organs and organ numbers which have been tested for the presence of <i>Sphaerothecum destruens</i> DNA. Organs tested included the kidney (K), liver (L), intestine (I), gill (Gi) and gonad (Go). n: number of fish sampled.</p>*<p>: at 28 d.p.e. the liver, kidney and intestine of 10 <i>C. carpio</i> were tested for <i>S. destruens</i>.</p>**<p>: gill and gonad tissues were analyzed in only 13 of the 22 <i>R. rutilus</i> mortalities.</p