Scale-free dynamics of COVID-19 in a Brazilian city.

A common basis to address the dynamics of directly transmitted infectious diseases, such as COVID-19, are compartmental (or SIR) models. SIR models typically assume homogenous population mixing, a simplification that is convenient but unrealistic. Here we validate an existing model of a scale-free fractal infection process using high-resolution data on COVID-19 spread in São Caetano, Brazil. We find that transmission can be described by a network in which each infectious individual has a small number of susceptible contacts, of the order of 2-5. This model parameter correlated tightly with physical distancing measured by mobile phone data, such that in periods of greater distancing the model recovered a lower average number of contacts, and vice versa. We show that the SIR model is a special case of our scale-free fractal process model in which the parameter that reflects population structure is set at unity, indicating homogeneous mixing. Our more general framework better explained the dynamics of COVID-19 in São Caetano, used fewer parameters than a standard SIR model and accounted for geographically localized clusters of disease. Our model requires further validation in other locations and with other directly transmitted infectious agents.

Performance and visceral tissue growth and development of Holstein calves fed differing milk replacer allowances and starch concentrations in pelleted starter.

The objectives of this study were to investigate how milk replacer (MR) allowance and differing concentrations of starch and neutral detergent fiber in starter alters visceral tissue and overall growth of the calf. Calves were randomly assigned to 1 of 4 dietary treatments (n = 12 per treatment) arranged in a 2 × 2 factorial based on daily MR allowance (MRA) and amount of starch in pelleted starter (SPS) as follows: 0.691 kg of MR/d [dry matter (DM) basis] with starter containing low or high starch (12.0% and 35.6% starch, respectively) and 1.382 kg of MR/day (DM) with starter containing low or high starch. All calves were housed in individual pens with straw bedding until wk 5 when bedding was covered to minimize intake. Calves were fed MR twice daily (0700 and 1700 h) containing 24.5% crude protein (DM) and 19.8% fat (DM), and had access to pelleted starter (increased by 50 g/d if there were no refusals before weaning, and then 200 g/d during and after weaning) and water starting on d 1. Calves arrived between 1 and 3 d of age and were enrolled into an 8-wk study, with calves undergoing step-down weaning during wk 7. Intakes were measured daily, and body weight (BW) and blood samples were recorded and collected weekly. Calves were dissected in wk 8 for visceral tissue measurements. Overall, there was increased MR DM intake for the high- (0.90 ± 0.01 kg/d; ± SE) compared with the low-MRA (0.54 ± 0.01 kg/d) calves, whereas starter DM intake increased in low- (0.47 ± 0.05 kg/d) compared with high-MRA (0.20 ± 0.05 kg/d) calves, which was driven by increases in wk 6, 7, and 8. High-MRA calves had increased BW during wk 2, 3, 4, 5, 6, and 7. The difference in BW disappeared by wk 8, with overall average daily gain having a tendency to be increased in high (0.57 ± 0.04 kg/d) compared with low-MRA (0.50 ± 0.04 kg/d) calves, whereas average daily gain was increased in high-MRA calves during wk 2 and 3 and increased in low-MRA calves during wk 7 and 8. There were several differences throughout visceral tissue measurements, but most notably, an increase in rumen mass (i.e., full, empty, and digesta weights) in low- compared with high-MRA calves, as well as in low- compared with high-SPS calves was observed. The length, width, and 2-dimensional area of rumen papillae were also increased in low- (area: 0.88 ± 0.03 mm2) compared with high-MRA (0.46 ± 0.03 mm2) calves. The majority of differences were attributed to increased MR allowance, which contributed to reduced pelleted starter intake by more than 50% and reduced rumen development, whereas differences in starch intake from the completely pelleted starter had minimal effects on overall growth and tissue measurements.

The effect of neomycin inclusion in milk replacer on the health, growth, and performance of male Holstein calves during preweaning.

The prophylactic use of oral antimicrobials, such as neomycin, in milk replacer (MR) or whole milk is a common practice in calf-rearing that is thought to aid in preventing disease. Heavy reliance on antimicrobials is of concern not only because of the development of antimicrobial resistance, but also because of the potentially negative effects on health. The objective of this study was to investigate the effects of neomycin on calf health and growth performance. One hundred and sixty calves (approximately 3-10 d of age), distributed across 2 experimental periods, were stratified by body weight (BW) and serum total protein, and assigned to 1 of 3 treatments: control (CON; nonmedicated MR, n = 60), short-term antibiotic (ST; neomycin mixed in MR from d 1-14, n = 50), or long-term antibiotic (LT; neomycin in ​MR from d 1-28, n = 50). Arrival BW (47.69 ± 0.87 kg) and serum total protein (5.67 ± 0.09 g/dL) were not different between treatment groups. Neomycin in ST and LT was dosed in MR at a rate of 20 mg/kg of BW and was adjusted weekly according to BW. Calf BW was measured weekly for 49 d, and health indicators (fecal score, attitude score, respiratory score, and rectal temperature), MR intake, starter intake, and the use of additional electrolytes and antimicrobials were recorded daily. Calves in the CON group experienced a higher proportion of days with diarrhea (20.32 ± 0.02%) compared with ST (14.70 ± 0.02%) or LT (13.80 ± 0.02%) calves, as well as longer bouts of diarrhea (7.45 ± 0.38 d, 5.69 ± 0.46 d, and 5.62 ± 0.45 d for CON, ST, and LT calves, respectively). Calves in the CON group also experienced higher fecal scores (score of 0.64 ± 0.04) than ST (score of 0.53 ± 0.04) or LT (score of 0.49 ± 0.04) calves, especially at d 7. However, no differences were observed in other health-related measures. The time to reach first diarrhea and first respiratory illness was not different between treatments, nor was the time to recover from respiratory illness. The time to intervention with additional electrolytes or antimicrobials was not different between treatment groups. Furthermore, growth performance, feed intake, and feed conversion ratio were not different. No differences were found when comparing ST and LT, except in the defined daily dose of total antimicrobials received. Calves in the LT group received a higher overall dose than ST calves, and both ST and LT calves received a higher dose than CON calves, which received no prophylactic antimicrobials. Given that there were no differences in performance variables and no additional health benefits aside from reduced fecal scores in calves fed neomycin, current practices involving the use of antimicrobials on dairy and veal operations need to be considered more prudently.

Technical note: Is fecal consistency scoring an accurate measure of fecal dry matter in dairy calves?

The objective of this cross-sectional study was to evaluate the accuracy of fecal consistency scoring as a measure of fecal dry matter (DM) in dairy calves. This study was conducted at a commercial grain-fed veal facility in southwestern Ontario. A total of 160 calves arrived at the facility in 2 groups of 80 calves each. Calves were fed milk replacer twice daily at 0700 and 1700 h and had ad libitum access from arrival onward to water through nipple drinkers and starter through a shared trough. Fecal consistency scores were evaluated once daily in the first 28 d after arrival before milk feeding. The fecal consistency scoring was conducted using a 4-level scoring scale: 0 = normal (firm but not hard); 1 = soft (does not hold form, piles but spreads slightly); 2 = runny (spreads readily); and 3 = watery (liquid consistency, splatters). Fecal samples were collected from all calves via rectal palpation on d 1, 7, 14, and 21 at 0900 h for determination of fecal DM. Mixed repeated measures linear regression models were built to assess the accuracy of fecal consistency scoring in predicting fecal DM. Over 4 selected time points (d 1, 7, 14, and 21) the 160 calves were observed, 382 (61.6%) had a fecal consistency score of 0, 121 (19.5%) had a score of 1, 85 (13.7%) had a score of 2, and 32 (5.2%) had a score of 3. A fecal score of 0 had a fecal DM of 25.1 ± 8.4%, whereas a fecal score of 1 had a DM of 21.8 ± 8.2%. With respect to calves that had a fecal score of 2 or 3, their fecal DM was 16.0 ± 11.1% and 10.7 ± 6.9%, respectively. In evaluating the pairwise comparisons generated in the repeated measures model that controlled for day of sampling, a fecal score of 0 had a 3.2%, 8.1%, and 12.0% higher fecal DM, respectively, when compared with those that had a fecal score of 1, 2, and 3. In addition, calves with a fecal score of 1 had a 5.0% and 8.8% higher fecal DM than calves with a fecal score of 2 and 3, respectively. Finally, calves with a fecal score of 2 had a 3.8% higher fecal DM than those with a fecal score of 3. This study confirms that using observational fecal consistency scoring can accurately predict diarrhea or a decline in fecal DM.

Group living, competition, and the evolution of cooperation in a sessile invertebrate.

Competition and cooperation are thought to represent the opposite extremes of organism interactions. I here show that the formation of aggregations in a sessile organism requires cooperation between individuals and that the gregarious pattern of habitat selection generating these aggregations is a response to a density dependence in the outcome of interference competition.

Transmission genetics of allorecognition in Hydractinia symbiolongicarpus (Cnidaria:Hydrozoa).

Allorecognition is ubiquitous, or nearly so, amongst colonial invertebrates. Despite the prominent role that such phenomena have played both in evolutionary theory and in on the origin of the vertebrate immune system, unambiguous data on the transmission genetics of fusibility (i.e., the ability of two individuals to fuse upon tissue contact) is lacking for any metazoan outside of the phylum Chordata. We have developed lines of the hydroid Hydractinia symbiolongicarpus (Phylum Cnidaria) inbred for fusibility and here report results of breeding experiments establishing that fusibility segregates as expected for a single locus with codominantly expressed alleles, with one shared allele producing a fusible phenotype. Surveys of fusibility in field populations and additional breeding experiments indicate the presence of an extensive allele series.

Viruses and exacerbations of chronic obstructive pulmonary disease: unmet clinical need.

Chronic obstructive pulmonary disease (COPD) is a non-communicable long-term condition characterised by accelerated lung-function decline and intermittent episodes of respiratory illness called exacerbations. We discuss the current understanding of the role of viruses in these elements of COPD. The burden of acute viral illness in COPD is great and largely unrecognised. Because naturally occurring exacerbations are inherently difficult to study, only recently have we understood underlying pathophysiological mechanisms and the true prevalence of viral exacerbations. Data are also emerging to support a potential role for chronic viral infection in the progression of stable COPD. As knowledge in these two areas develops, it is clear that the role of viruses in COPD represents a significant unmet clinical need.

Dynamics of Gastrovascular Circulation in the Hydrozoan Podocoryne carnea: the One-Polyp Case.

Time-lapse video microscopy and image analysis algorithms were used to generate high-resolution time series of the length and volume of a single hydrozoan polyp before and after feeding. A polyp of Podocoryne carnea prior to feeding is effectively static in length and volume. At 20{deg}C, feeding elicits 8-millihertz (mHz) oscillations in polyp length and volume. A polyp connected to a colony by a single stolon displayed an abrupt transition from low-amplitude, 8-mHz oscillations to large-amplitude, 6-mHz oscillations at 1.5-2 h after feeding. The transition was preceded by a substantial decrease in polyp volume and increase in length which coincided with the export of food items from the digestive cavity of the polyp into the colonial gastrovascular system. In contrast, 8-mHz oscillations of a polyp isolated from a colony continued for 12.7 h after feeding, at which time particulates from the digestive cavity were exported into the hydrorhiza and a 4-mHz subharmonic became briefly dominant. Regular oscillatory behavior was terminated by regurgitation at comparable intervals post-feeding in coupled and isolated polyps. These observations are compatible with the hypothesis that the presence of nutrients in the digestive cavity induces polyp oscillations and that release of nutrients into the gastrovascular system similarly induces unfed polyps to oscillate, thereby distributing the contents of the fed polyp throughout the colony.

Spontaneous abortion: a prospective cohort study of younger women from the general population in Denmark. Validation, occurrence and risk determinants.

OBJECTIVE: To assess the occurrence of spontaneous abortion, comparing two different data sources. To estimate the rate of spontaneous abortion over a 2-year period, and examine potential predictors of the risk for incident spontaneous abortion. METHODS: We used interview data from a population-based prospective cohort study comprising 11,088 women and data from a linkage of the cohort with the Hospital Discharge Register to compare spontaneous abortions as reported in the interview with those identified in the register. Based on interview data, we estimated the rate of spontaneous abortion during the two-year follow-up. Finally, risk determinants for incident spontaneous abortion were analyzed by means of logistic regression. RESULTS: A total of 654 spontaneous abortions before enrolment in the study were reported by the women compared to 531 abortions found in the register. More than 80% of the spontaneous abortions identified from both sources were recorded in the same year. During follow-up a total of 20.9% of pregnancies intended to be carried to term ended as a spontaneous abortion. In the risk factor analysis, we found that previous spontaneous abortion, being single, never having used oral contraceptives, and use of intrauterine device were associated with increased risk of subsequent spontaneous abortion. In addition, it was indicated that a short interpregnancy interval following a spontaneous abortion may confer an increased risk of abortion in the subsequent pregnancy. CONCLUSION: We found a high rate of spontaneous abortion in the present study and an acceptable agreement between information obtained by interview and register information. More than 25% of the spontaneous abortions were only reported by the women, and this could not be explained by erroneously reported induced abortions, and may be early, nonhospitalized abortions. We confirm that number of previous spontaneous abortions is a strong determinant, and our data may also indicate a role of previous contraceptive habits. A role of the length of interpregnancy interval in the risk of spontaneous abortion cannot be ruled out.

Competitive intransitivity and size-frequency distributions of interacting populations.

The competitive ranking of three marine sessile organisms was determined from overgrowth observations and found to be intrasitive. Overgrowth results were dependent upon relative vertical relief which, in turn, was related to colony area. Discriminant function analysis demonstrates that competitive rankings can be largely predicted on the basis of knowledge of the size-frequency distribution of interacting populations. Because size increases with age for these species, size-dependent competition implies age-dependent competition. The role of age structure in determining the results of inter-specific interactions has been curiously neglected, particularly as it relates to competitive ability, yet the age dependence of competitive ability suggests (i) the occurrence of intransitivity in purely exploitative systems, (ii) a mechanism for frequency-dependent behavior, (iii) the production of limit cycles, and (iv) the possibility of size refugia.

Competition within and between encrusting clonal invertebrates.

Colonies of encrusting marine invertebrates are tractable models for the study of competition, because of the relative ease with which observations can be made on the frequency and outcome of overgrowth interactions. Studies of intraspecific competition have found that competition is predicated upon a genetically controlled recognition event, which results in either fusion or rejection. Data are rapidly accumulating in two model systems showing that fusion is associated with somatic cell parasitism and that rejection is associated with overgrowth. Thus, encounters between conspecifics define a choice: to compete at the level of the cell lineage or to compete at the level of the colony. Fusion-rejection genes act to control the units (or targets) of selection.

Somatic cell parasitism and the evolution of somatic tissue compatibility.

Selection pressures proposed to account for the convergent evolution of self/not-self recognition systems in lower organisms include defense against microbial parasites and somatic cell variants. Direct support for the existence of somatic cell parasites in natural populations has been lacking. I here report the occurrence of a somatic cell parasite in the cellular slime mold Dictyostelium mucoroides and discuss the implications of this phenomenon to the evolution of mechanisms of somatic tissue compatibility.

Evolution, development, and the units of selection.

The "Modern Synthesis" forms the foundation of current evolutionary theory. It is based on variation among individuals within populations. Variations within individuals are believed to hold no phylogenetic significance because such variation cannot be transmitted to the germ line (i.e., Weismann's doctrine). Weismann's doctrine, however, does not apply to protists, fungi, or plants and is an entirely unsupported assumption for 19 phyla of animals. This fact requires that the Modern Synthesis be reexamined and modified.

Treatment with 2,4-dinitrophenol mimics ontogenetic and phylogenetic changes in a hydractiniid hydroid.

Clonal plants, fungi, and invertebrate animals often display both intra- and interspecific heterochronic variation in the relative proportions of ramets (e.g., polyps, plantlets) and stolons (or rhizomes, hyphae). Treatment of developing colonies of Podocoryne carnea, a hydractiniid hydroid, with dilute solutions of 2,4-dinitrophenol (DNP), an uncoupler of oxidative phosphorylation, accelerates the usual ontogenetic trajectory of polyp and stolon production. This morphological heterochrony can be related to the hydrodynamic behavior of the gastrovascular system under the conditions of "loose-coupling" of oxidative phosphorylation produced by DNP. In its normal ontogeny, Hydractinia symbiolongicarpus, a closely related hydractiniid hydroid, not only shows morphological heterochrony similar to that induced in P. carnea by DNP, but also shows a pattern of gastrovascular flow similar to that observed in P. carnea under treatment with DNP. These results support hypotheses linking metabolic activity to heterochronic variation and provide a potentially widely applicable experimental basis for the study of such variation.

Alleopathy and spatial competition among coral reef invertebrates.

Species of ectoprocts and solitary encrusting animals were subjected in aquaria to homogenates of 11 sympatric species of sponges and colonial ascidians. Five of the nine sponge species and one of the two ascidian species exhibited species-specific allelochemical effects. Evidence suggests that alleochemical provide a wide-spread, specific, and complex mechanism for interference competition for space among natural populations of coral reef organisms. The existence of such species-specific mechanisms may provide a basis for maintenance of diversity in space-limited systems in the absence of high levels of predation and physical disturbance.