Maintenance of brucellosis in Yellowstone bison: linking seasonal food resources, host-pathogen interaction, and life-history trade-offs

Effects of Pregnancy Prevention on Brucella abortus Shedding in American bison (Bison bison)

Products of parturition are the predominant source of Brucella abortus for transmission in bison (Bison bison). Our objective was to assess whether preventing pregnancy in Brucella-seropositive bison reduced B. abortus shedding. Brucella-seropositive and -seronegative bison from Yellowstone National Park, Wyoming, USA were used in a replicated experiment. Each of two replicates (rep1, rep2) included a group of seropositive females treated with a single dose of gonadotropin-releasing hormone-based immunocontraceptive (Treatment rep1, n=15; Treatment rep2, n=20) and an untreated group (Control rep1, n=14; Control rep2, n=16) housed separately. Seronegative sentinel females were placed in each group to monitor horizontal transmission. Seronegative males were co-mingled for breeding each year. Pregnant females were removed from treatment groups in the first year, but not thereafter. Each January-June we monitored for B. abortus shedding events-any parturition associated with culture-positive fluids or tissues. We analyzed probability of shedding events using a negative binomial generalized linear mixed model fit by maximum likelihood using Laplace approximation. Over 5 yr, we observed zero shedding events in Treatment rep1 vs. 12 in Control rep1. All five Control rep1 sentinels but zero (0/5) Treatment rep1 sentinels seroconverted. In the second replicate, Treatment rep2 had two shedding events over 3 yr and Control rep2 had five events over 2 yr. Sentinels in both Control rep2 (3/6) and Treatment rep2 (5/6) seroconverted by trial endpoint. Treatment rep1 showed a reduced shedding probability relative to Control rep1, Treatment rep2, and Control rep2 (log odds value -25.36 vs. -1.71, -1.39, and -0.23, respectively). Fixed effect predictor covariates, year and age, had no explanatory value. These data suggest that successful contraception of brucellosis-seropositive female bison prevents shedding of B. abortus by individual animals. However, contraceptive treatment may or may not sufficiently reduce disease transmission to reduce brucellosis prevalence in an affected herd.

Seasonal diet composition of Himalayan goral (Naemorhedus goral) in Kajinag National Park, Jammu and Kashmir, India

In temperate environments, forage availability and quality are known to influence life history traits of wild ungulates. However, variations in foraging strategies of these mountain dwellers with changing plant availability have received little attention. The seasonal vegetation availability in temperate climatic conditions of Kajinag National Park (KNP) was assessed by plot method at different altitudes (1900–3600 m a.s.l.) from 2018 to 2020 on seasonal basis. The objective of this study was to determine the impact of availability of vegetation on seasonal diet composition of Himalayan goral (Naemorhedus goral) inhabiting the National Park. We recorded 61 plant species whose availability differed significantly across seasons (F 3,240 = 20.14, p < 0.05). We found seasonal variation in the diet composition of Himalayan goral depicting a strong relationship between plant consumption and dynamic availability in the study area. Himalayan goral consumed herbs in spring (dominated by Dioscorea deltoidea relative importance value (RIV) = 27.20, Poa pratensis RIV = 14.99 and Themeda spp. RIV = 12.87), grasses in summer (dominated by Themeda spp. RIV = 34.12, P. pratensis RIV = 30.14, Bothriochloa ischaemum RIV = 22.72) and autumn (dominated by Themeda spp. RIV = 34.64, P. pratensis RIV = 30.14, Stipa spp. RIV = 29.73) and shrubs in winter (dominated by Indigofera heterantha RIV = 47.05, Prunus tomentosa RIV = 17.51 and Lonicera spp. RIV = 16.98). The annual diet of Himalayan goral was dominated by graze species (72.66%). The proportion of graze items in the diet showed a sharp decline from spring (90.67%) to winter (19.23%) whereas that of browse showed a huge increment from spring (4.67%) to winter (74.43%). This shift shows a survival or foraging strategy of a temperate ungulate in harsh winters with limited forage availability.

Production of embryos and a live offspring using post mortem reproductive material from bison (Bison bison bison) originating in Yellowstone National Park, USA

Bison from Yellowstone National Park (YNP) have an important genetic history. As one of the few wild herds of bison with no evidence of cattle DNA introgression and a large enough population to maintain genetic diversity, they are considered a conservation priority for the species. Unfortunately, there is a high prevalence of the zoonotic disease brucellosis in the herd. Part of the management strategy for controlling the disease and herd size in YNP is to remove bison from the population during the winter migration out of the park. This interagency management cull provides an opportunity to collect a large number of oocytes from a wild bison population for genetic banking and research purposes. During the winters of 2014-2018, which is the nonbreeding season for bison, oocytes were collected post mortem and used to determine the effects of donor reproductive maturity and pregnancy status on oocyte quality and in vitro fertilization (IVF) outcomes, and to demonstrate the feasibility of producing healthy offspring. Cumulus oocyte complexes (COCs) were placed into an in vitro embryo production (IVP) system, and on days 7, 7.5, and 8 of in vitro culture (Day 0 = day of in vitro fertilization) embryos were assessed for developmental stage and quality prior to vitrification. Embryos were then stored in liquid nitrogen until the breeding season when a subset were warmed, cultured for 6 h, evaluated for survival, and transferred to healthy bison recipients. There were no significant differences in the ability of recovered COCs to support blastocyst development based on female reproductive maturity or pregnancy status (juvenile 79/959 (8.2%) vs sexually mature 547/6544 (8.4%); non-pregnant 188/2302 (8.2%) vs pregnant 556/6122 (9.1%)). Following the transfer of 15 embryos to 10 recipients, one healthy female calf was born. This work demonstrates that live offspring can be generated from COCs collected from YNP bison post mortem in the non-breeding season, and that gamete recovery can be a valuable tool for conservation of valuable genetics for this species while mitigating diseases like brucellosis.

Seasonal diet composition of Pyrenean chamois is mainly shaped by primary production waves

In alpine habitats, the seasonally marked climatic conditions generate seasonal and spatial differences in forage availability for herbivores. Vegetation availability and quality during the growing season are known to drive life history traits of mountain ungulates. However, little effort has been made to understand the association between plant phenology and changes in the foraging strategies of these mountain dwellers. Furthermore, this link can be affected by the seasonal presence of livestock in the same meadows. The objective of this work was to study the seasonal changes in diet composition of Pyrenean chamois (Rupicapra p. pyrenaica) and its relationship to primary production trends in a Mediterranean alpine environment. Moreover, diet composition in two populations with contrasting livestock pressure was compared in order to study the effect of sheep flocks on the feeding behaviour of chamois. From 2009 to 2012, monthly diet composition was estimated by cuticle microhistological analysis of chamois faeces collected in the eastern Pyrenees. The primary production cycle was assessed by remote sensing, using the Normalized Difference Vegetation Index. Additionally, the diet of sheep sharing seasonally the subalpine and alpine meadows with chamois was analysed. Diet selection of chamois and sheep and their overlap was also assessed. Our results show an intra-annual variation in the diet composition of Pyrenean chamois and demonstrate a strong relationship between plant consumption dynamics and phenology in alpine areas. In addition, Calluna vulgaris, Cytisus spp. and Festuca spp., as well as forbs in the summer, are found to be key forage species for Pyrenean chamois. Furthermore, this study couldn’t detect differences between both chamois populations despite the presence of sheep flocks in only one area. However, the detection of a shift in the diet of chamois in both areas after the arrival of high densities of multi-specific livestock suggest a general livestock effect. In conclusion, Pyrenean chamois are well adapted to the variations in the seasonal availability of plants in alpine habitats but could be disturbed by the seasonal presence of livestock. Due to the key plants in their diet, we suggest that population management programmes should focus on the preservation of mixed grasslands composed of patches of shrubs and herbs. The effects of climate change and shrub expansion should be studied as they may potentially affect chamois population dynamics through changes in habitat composition and temporal shifts in forage availability.

Seroprevalence and risk factors associated with Brucella seropositivity in dairy and mixed cattle herds from Ecuador

An extensive cross-sectional study to determine the seroprevalence of and associated risk factors for Brucella infection was performed in dairy and mixed (dairy-beef) cattle herds in Ecuador. A total of 2666 serum samples from 386 farms were analyzed using Rose Bengal test and a blocking ELISA test. In addition, a questionnaire with 57 variables related to management, feeding, facilities, biosecurity, and animal health was filled in every cattle farm. A Generalized Estimating Equations model was used to determine the factors associated with Brucella seropositivity. The true prevalence of Brucella seropositivity in dairy and mixed cattle from Ecuador reached 17.0% (CI95% 15.6-18.4%). The herd prevalence was 45.1% (174/386) (CI95% 40.1-50.1%), and the within-herd prevalence ranged from 10 to 100% (mean 38.9%; Q1 14.3%, Q2 26.8%, Q3 52.5%). Seven factors were included in the GEE model for Brucella seropositivity: the nominal variables sex (OR 2.03; CI95% 1.32-3.13), herd type (dairy) (OR 1.79; CI95% 1.11-2.87), closed facilities in the farm (OR 1.80; CI95% 1.19-2.74), and ad libitum feeding (OR: 0.32; CI95%: 0.19-0.54), and the quantitative variables age (OR 1.005; CI95% 1.001-1.009), average slope in the farm (%) (OR 1.013; CI95% 1.002-1.024), and annual abortion rate (OR 1.016; CI95% 1.002-1.031). This study remarks the high spread of Brucella infection in cattle farms from Ecuador. In addition, it reports the risk factors associated to this infection in the predominant extensive system existent in this country.

How counterfactuals of Red-Queen theory shed light on science and its historiography

A historical episode of evolutionary theory, which has lead to the Red Queen theory of the evolutionary maintenance of sex, includes two striking contingencies. These are used to explore alternative what-if scenarios, in order to test some common opinions about such counterfactuals. This sheds new light on the nature of science and its historiography. One counterfactual leads to an unexpected convergence of its result to that of the actual science but, nevertheless, differs in its causal structure. The other diverges towards an incompatible alternative, but this requires further contingent choices that also diverge from actual science. The convergence in the first counterfactual is due to a horizontal transfer of knowledge. Similar transfers of knowledge are typical for innovations of actual science. This suggests that contingent choices can merge as well as fork research traditions both in actual research and counterfactual history. Neither the paths of the actual history of science nor those of its counterfactual alternatives will form a tree of exclusively diverging bifurcations, but a network instead. Convergencies in counterfactuals may, therefore, be due to the web-structure of science as much as to the aims of the historians in question. Furthermore, the difference in causal structure between the actual science and its convergent counterfactual might become diagnostic for external factors rather than internal aims forcing a historian towards convergence.