Peste des petits ruminants Virus Transmission Scaling and Husbandry Practices That Contribute to Increased Transmission Risk: An Investigation among Sheep, Goats, and Cattle in Northern Tanzania

Peste des petits ruminants virus (PPRV) causes an infectious disease of high morbidity and mortality among sheep and goats which impacts millions of livestock keepers globally. PPRV transmission risk varies by production system, but a deeper understanding of how transmission scales in these systems and which husbandry practices impact risk is needed. To investigate transmission scaling and husbandry practice-associated risk, this study combined 395 household questionnaires with over 7115 cross-sectional serosurvey samples collected in Tanzania among agropastoral and pastoral households managing sheep, goats, or cattle (most managed all three, n = 284, 71.9%). Although self-reported compound-level herd size was significantly larger in pastoral than agropastoral households, the data show no evidence that household herd force of infection (FOI, per capita infection rate of susceptible hosts) increased with herd size. Seroprevalence and FOI patterns observed at the sub-village level showed significant spatial variation in FOI. Univariate analyses showed that household herd FOI was significantly higher when households reported seasonal grazing camp attendance, cattle or goat introduction to the compound, death, sale, or giving away of animals in the past 12 months, when cattle were grazed separately from sheep and goats, and when the household also managed dogs or donkeys. Multivariable analyses revealed that species, production system type, and goat or sheep introduction or seasonal grazing camp attendance, cattle or goat death or sales, or goats given away in the past 12 months significantly increased odds of seroconversion, whereas managing pigs or cattle attending seasonal grazing camps had significantly lower odds of seroconversion. Further research should investigate specific husbandry practices across production systems in other countries and in systems that include additional atypical host species to broaden understanding of PPRV transmission.

Improvement and Application of Key Pasture Theory for the Evaluation of Forage–Livestock Balance in the Seasonal Grazing Regions of China’s Alpine Desert Grasslands

The calculation of theoretical carrying capacity (TCC) is one of the most fundamental tasks for the evaluation of the forage–livestock balance on grassland pastures. At present, the main methods for calculating TCC are the traditional theory (TT) and key pasture theory (KPT), but they both have obvious limitations in practical applications for the seasonal grazing regions in the alpine desert grasslands of China. In this study, the pastures in Wulan County (PWC) were selected as the research area. The unique features of the research area as well as the faulty applications of TT and KPT were fully analyzed, and then a new method named dynamic key pasture theory (DKPT) was established for calculating TCC by improving KPT with the introduction of the two dynamic factors of the livestock slaughter rate (α) and coefficient of grassland productivity (β). TT, KPT and DKPT were respectively used to calculate the TCC of the PWC under different precipitation scenarios. The forage–livestock balance in the PWC determined using DKPT was assessed by the forage–livestock balance index (FLBI). The results showed that the natural processes of grassland supply and livestock demand were significantly imbalanced in time and space and formed a dynamic cycle with four subprocesses, which was the supporting basis of DKPT; DKPT effectively improved the rationality of TCC and offered greater guidance for the evaluation of the forage–livestock balance in the seasonal grazing regions of China’s alpine desert grasslands. In the PWC, the TCCs of different pastures calculated by DKPT were clearly different from those calculated by TT and KPT; the areas of the pastures divided were extremely imbalanced, with a huge surplus of more than 50% in cool-season pastures; in the representative year of 2016, the pastures in the Xisai Basin were underloaded (FLBI = −35.19%) on the whole, while the pastures in the Chaka Basin were overloaded (FLBI = 24.34%).

Spatiotemporal influence of permafrost thaw on anthrax diffusion

<p>The recent 2016 outbreak of anthrax disease affecting reindeer herds in Siberia has been associated to the presence of old infected carcasses released from thawing permafrost, underlying the emerging character of such disease in the Arctic region due to climate change. Anthrax occurs in nature as a global zoonotic and epizootic disease caused by the spore-forming bacterium <em>Bacillus anthracis</em>. It principally affects herbivores and causes high animal mortality. Transmission occurs mainly via environmental contamination through spores which can remain viable in permafrost for many decades.</p><p>We propose and analyze a novel epidemiological model for anthrax transmission specifically tailored for the Arctic region. It conceptualizes the transmission of disease between susceptible and infected animals in the presence of environmental contamination, considering also herding practices (e.g. seasonal grazing) and the seasonal environmental forcing caused by thawing permafrost. We performed stability analyses and implemented Floquet theory for periodically forced systems, and therefore applied our model to the 17-year-long records of permafrost thawing depth available at the Lena River Delta (northern Siberia). Accordingly, in order to spatialize potential anthrax incidence and consequently the possible hazardous areas in the Arctic, we used the Maximum Entropy (Maxent) approach considering environmental variables and, in particular, accounting for current and expected permafrost thawing rates.</p><p>Results show how temporal variability of grazing and thawing may influence and favor sustained anthrax transmission.  Also, particularly warm years are associated to increased risk of anthrax incidence. Accordingly, we show that such risk could be mitigated with specific precautions involving herding practices, for example by anticipating or postponing seasonal grazing. Finally, a spatial map of the potential Arctic areas at risk is presented, providing a tool for local authorities in view of eventual targeted prevention measures.</p>

Response of soil respiration and soil microbial biomass carbon and nitrogen to grazing management in the Loess Plateau, China

Grassland covers more than a third of the earth's terrestrial surface. Grazing management can affect grassland carbon dynamics and soil microbial biomass, yet limited information is available on the effects of grassland management on carbon dioxide efflux and soil microbial biomass carbon (SMBC) and nitrogen (SMBN). During 2010 and 2011, soil respiration (Rs), SMBC, and SMBN, as well as different abiotic and biotic factors were measured after long term rotational grazing (nine years) on the grasslands of the semi-arid Loess Plateau, China. Grazing management included different grazing intensities and seasonal grazing patterns (in summer or winter). Stocking rates of 0, 2.7, 5.6, and 8.7 sheep ha−1 were used as grazing intensities, and warm-season grazing and cold-season grazing by sheep during summer and winter from 2010 to 2011 were used as grazing patterns. We hypothesized that the different seasonal grazing patterns and grazing intensities would affect Rs in a semi-arid grassland ecosystem. Our results indicated that grazing management significantly affected the rate of Rs, which supports our hypothesis. Grazing intensities tended to increase SMBC, but had no effect on SMBN. We also found that SMBC in cold season grazing plots was higher than that in the warm season grazing plots. However, variation in grazing patterns had little effect on SMBN. Furthermore, a structural equation model indicated that the aboveground biomass and soil microbial biomass were two important biotic factors that controlled Rs. Soil temperature (ST) and soil moisture (SM), which were affected by grazing intensity and patterns, were significant abiotic factors affecting Rs and soil microbial biomass. Our observations suggest that grazing management may change soil carbon sequestration rates in grassland ecosystems, because of changes in the aboveground plant and soil microbial biomass.