Reproduction Number Research Articles

Global stability and modeling with a non-singular kernel for fractional order heroin epidemic model: Insights from different population studies

There has been a worldwide epidemic of heroin that has affected people, families, societies, and cultures across the world. Now, the heroin epidemic has transitioned from heroin abuse to the overuse of synthetic narcotics, which are widely accessible and inexpensively produced. In this work, a novel mathematical approach is applied to investigate the dynamics of the heroin epidemic model and its harmful effect on society with different population data. A heroin model has been constructed with the importance of a non-singular kernel in the sense of a generalized Mittag-Leffler kernel. The well-possedness of the proposed model is proven via fixed-point theory. To examine the heroin model, two equilibrium states have been determined. These equilibrium states are proven to be locally and globally asymptotically stable. To analyze the behavior of heroin, a basic reproduction number and sensitivity analysis are used to determine the impact of different parameters mathematically as well as through simulations. To find the approximate solution, we implement the Toufik-Atangana numerical method at different fractional order values. The sensitivity of the heroin model is carried out, and 3-D graphs show the significance of the parameter involved in the model. Finally, the numerical outcomes are presented with different values of fractional parameters.

Dynamics and backward bifurcations of SEI tuberculosis models in homogeneous and heterogeneous populations

The main difference between tuberculosis (TB) and other infectious diseases is that the transmission of the bacterium should be considered not only as the development of a primary infection, but also as exogenous reinfection or endogenous reactivation. Moreover, individuals in the population may have heterogeneous contact rates, which can be described by complex networks. To this end, we present two differential equation-based TB models in homogeneous and heterogeneous populations. The first model assumes that the number of contacts per unit time is constant for the whole population, whereas the second model considers the heterogeneous number of contacts per unit time for each individual. We derive the basic reproduction number of each model using the next-generation matrix method, and analyze the dynamical properties of each model in detail. We find that the two models undergo backward bifurcations and have the same threshold condition for backward bifurcation. From this threshold condition, we see that the reduced rate of exogenous reinfection of individuals plays an important role in causing the backward bifurcation. Interestingly, the second model allows the threshold condition for backward bifurcation to be independent of network parameters. Thus, unlike other infectious disease models on complex networks, in controlling the spread of tuberculosis among populations with different numbers of contacts, we only need to focus on disease parameters during treatment. Finally, numerical simulations more intuitively demonstrate the impact of parameter changes on the prevalence of tuberculosis and reveal the model's richer and more interesting dynamical properties, such as bistability. Sensitivity analysis indicates that the basic reproduction number is highly correlated with both the relapse rate of latent individuals progressing to active infection and the probability of healthy individuals becoming infected after contact with the pathogen. Therefore, enhancing the detection and treatment of latent cases and reducing contact between infected and uninfected individuals are the most crucial public health interventions.

An immuno-epidemiological model with non-exponentially distributed disease stage on complex networks

Most of epidemic models assume that duration of the disease phase is distributed exponentially for the simplification of model formulation and analysis. Actually, the exponentially distributed assumption on the description of disease stages is hard to accurately approximate the interplay of drug concentration and viral load within host. In this article, we formulate an immuno-epidemiological epidemic model on complex networks, which is composed of ordinary differential equations and integral equations. The linkage of within- and between-host is connected by setting that the death caused by the disease is an increasing function in viral load within host. Mathematical analysis of the model includes the existence of the solution to the epidemiological model on complex networks, the existence and stability of equilibrium, which are completely determined by the basic reproduction number of the between-host system. Numerical analysis are shown that the non-exponentially distributions and the topology of networks have significant roles in the prediction of epidemic patterns.

A clustered-LPSEIRS malware propagation model in complex networks

In this paper, we present a new malware propagation model that integrates epidemic spread, clustering, and link prediction techniques, tailored for complex network networks. Our model is based on the clustered-link prediction-susceptible-exposed-infected-recovered (clustered-LPSEIRS) epidemic model, which simulates malware dissemination within the network. Our findings reveal a significant decrease in the rate of malware spread compared to the traditional SEIR model, with this enhancement in containment attributed to the integration of clustering and link prediction methods. We also compute the basic reproduction ratio (R0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$R_{0}$$\\end{document}) for our model, providing insights into the potential ramifications of malware within the network. By examining parameter variations, we enhance our understanding of the model's behavior under diverse scenarios. Additionally, we assess the influence of clustering and link prediction on mitigating malware spread, emphasizing its effectiveness in diminishing the overall impact.

A two-strain COVID-19 co-infection model with strain 1 vaccination

COVID-19 has caused substantial morbidity and mortality worldwide. Previous models of strain 1 vaccination with re-infection when vaccinated, as well as infection with strain 2 did not consider co-infected classes. To fill this gap, a two co-circulating COVID-19 strains model with strain 1 vaccination, and co-infected is formulated and theoretically analyzed. Sufficient conditions for the stability of the disease-free equilibrium and single-strain 1 and -strain 2 endemic equilibria are obtained. Results show as expected that (1) co-infected classes play a role in the transmission dynamics of the disease (2) a high efficacy vaccine could effectively help mitigate the spread of co-infection with both strain 1 and 2 compared to the low-efficacy vaccine. Sensitivity analysis reveals that the main drivers of the effective reproduction number Re are primarily the effective contact rate for strain 2 (β2), the strain 2 recovery rate (τ2), and the vaccine efficacy or infection reduction due to the vaccine (η). Thus, implementing intervention measures to mitigate the spread of COVID-19 should not ignore the co-infected individuals who can potentially spread both strains of the disease.

Decoding the origins, spread, and global risks of mcr-9 gene

The global spread of the plasmid-mediated mcr (mobilized colistin resistance) gene family presents a significant threat to the efficacy of colistin, a last-line defense against numerous Gram-negative pathogens. The mcr-9 is the second most prevalent variant after mcr-1. A dataset of 698 mcr-9-positive isolates from 44 countries is compiled. The historical trajectory of the mcr-9 gene is reconstructed using Bayesian analysis. The effective reproduction number is used innovatively to study the transmission dynamics of this mobile-drug-resistant gene. Our investigation traces the origins of mcr-9 back to the 1960s, revealing a subsequent expansion from Western Europe to the America and East Asia in the late 20th century. Currently, its transmissibility remains high in Western Europe. Intriguingly, mcr-9 likely emerged from human-associated Salmonella and exhibits a unique propensity for transmission within the Enterobacter. Our research provides a new perspective that this host preference may be driven by codon usage biases in plasmids. Specifically, mcr-9-carrying plasmids prefer the nucleotide C over T compared to mcr-1-carrying plasmids among synonymous codons. The same bias is seen in Enterobacter compared to Escherichia (respectively as their most dominant genus). Furthermore, we uncovered fascinating patterns of coexistence between different mcr-9 subtypes and other resistance genes. Characterized by its low colistin resistance, mcr-9 has used this seemingly benign feature to silently circumnavigate the globe, evading conventional detection methods. However, colistin-resistant Enterobacter strains with high mcr-9 expression have emerged clinically, implying a strong risk of mcr-9 evolving into a global "true-resistance-gene". This study explores the mcr-9 gene, emphasizing its origin, adaptability, and dissemination potential. Given the high mcr-9 expression colistin-resistant strains was observed in clinically the prevalence of mcr-9 poses a significant challenge to drug resistance prevention and control within the One Health framework. This work was partially supported by the National Natural Science Foundation of China (Grant No. 32141001 and 81991533).

Serologic Evidence for Early SARS-CoV-2 Circulation in Lima, Peru, 2020.

During early 2021, Peru had the highest COVID-19-associated per-capita mortality rate. Socioeconomic inequality, insufficiently prepared healthcare, and surveillance systems are factors explaining the mortality rate, which can be severely worsened by early undetected SARS-CoV-2 circulation. We tested 1,441 individuals with fever sampled during August 2019-May 2021, several months before the first SARS-CoV-2 seroprevalence study available so far in Lima, Peru, for SARS-CoV-2-specific antibodies. The testing algorithm included a chemiluminescence immunoassay and surrogate virus neutralization test. Early positive samples (N = 24) from January-March 2020 were further tested using a plaque-reduction neutralization test (PRNT) and avidity test against the SARS-CoV-2 spike and nucleoprotein. None of the early samples were PRNT-confirmed, in contrast to 81.8% (18/22) of a subsample from April 2020 onward (Fisher exact test; P <0.0001). Therefore, we excluded non-PRNT-confirmed samples from subsequent analyses. The SARS-CoV-2 antibody detection rate was 0.9% in mid-April 2020 (1/104; 95% CI: 0.1-5.8%), suggesting viral circulation in early-middle March 2020, consistent with the first molecular detection of SARS-CoV-2 in Peru on March 2020. Mean avidity increase of 62-77% to 81-94% from all PRNT-confirmed SARS-CoV-2-positive samples during early 2020 were consistent with onset of SARS-CoV-2 circulation during late February/March 2020. Early circulation was also confirmed in a susceptible, exposed, infected, and recovered mathematical model that calculated an effective reproduction number >1 during February-March 2020. Early introduction of SARS-CoV-2 thus contributed to the high COVID-19 mortality rate in Peru. Emphasizing the role of diagnostic confirmation in understanding the pandemic's trajectory, this study highlights the importance of early detection and accurate testing in managing infectious disease outbreaks.

ECOTOXICITY OF ALKALINE RESIDUE FROM THE PULP AND PAPER INDUSTRY TO SOIL FAUNAL ORGANISMS

The increased production and expanding demand for cellulosic products have required companies to provide solutions for the proper disposal of generated residues without compromising soil quality. In this context, the current research aimed at evaluating the ecotoxicological impacts of dregs application in subtropical soils. The experiments were carried out with the earthworm Eisenia andrei, the springtail Folsomia candida, and the potworm Enchytraeus crypticus in two subtropical soils (Neosol and Cambisol) collected in the southern region of Brazil. The considerable differences in texture and organic matter content motivated the choosing of these soils. The reproductive rate of all organisms was influenced, with varying EC50 values depending on the soil type. However, more pronounced effects were observed for Neosol. The springtail F. candida proved to be the most sensitive to contamination (EC50 = 5.8 g kg-1 for Neosol and 48.5 g kg-1 for Cambisol), followed by the earthworm E. andrei (EC50 = 62.4 g kg-1 for Neosol and 129.5 g kg-1 for Cambisol) and the potworm E. crypticus (EC50 = 67.2 g kg-1 for Neosol and 230.4 g kg-1 for Cambisol). As a result, while dregs can be used to correct soil acidity, they have been shown to have negative effects on important organisms responsible for functions critical to maintaining ecosystem quality.

The antidepressant, sertraline, impacts growth and reproduction in the benthic deposit feeder, Tubifex tubifex

Among emerging contaminants, pharmaceuticals are considered one of the most pertinent substances that may threaten aquatic ecosystems. Pharmaceuticals are designed to be directed at specific metabolic- and molecular pathways. Thus, they are assumed to be still biologically active when entering the ecosystem and may result in unpremeditated impacts on non-target organisms. One of the most widely used selective serotonin reuptake inhibitors, sertraline (an antidepressant), is regularly found in aquatic environments. However, knowledge about the effects, and in particular, of sediment-associated sertraline in benthic invertebrates is limited. We examined the impacts of chronic exposure (28 d) to sediment-associated sertraline (3.3, 33, 330 μg/g dw sed.) on survival, growth and reproduction in the deposit-feeding oligochaete, Tubifex tubifex. Sertraline significantly decreased T. tubifex survival and growth. Worms exposed to high sertraline concentrations (330 μg/g) had a lower growth rate and reproduction, as indicated by a significantly lower number of cumulated cocoons. Worms exposed to an environmentally relevant concentration (3.3 μg/g) decreased growth but maintained a reproduction rate similar to that of the control. The implications are that adult worms exposed to high sertraline concentrations presumably required more energy for maintenance and detoxification, thereby reducing available energy for reproduction and growth. This represents a trade-off between survival, reproduction and growth. In contrast, T. tubifex exposed to environmentally relevant concentrations allocated more energy to reproduction by slightly increasing the number of cocoons produced and reducing growth. However, the quantity and quality of offspring may be impacted as we observed fewer juveniles in the environmentally relevant treatment than in the control. Overall, the results indicate that sediment-associated sertraline is bioavailable and negatively impacts T. tubifex survival, growth, and reproduction even at environmentally relevant concentrations.

The impact of lethal and sub-lethal exposure of emamectin benzoate on population of Spodoptera litura (Lepidoptera: Noctuidae) under laboratory conditions

Emamectin benzoate is an avermectin bio-insecticide commonly used for managing several insect pests including Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae), a major polyphagous pest of many cultivated crops. The current study was conducted to evaluate the effects of emamectin benzoate on the fitness of S. litura populations exhibiting differential susceptibility to insecticide. The selection process and all the bioassays were carried out using 6-day-old 2nd instar larvae of S. litura. A field-collected population of S. litura was divided into two groups: one selected with emamectin benzoate for eight generations (EB-Sel) and the other kept unexposed (Unsel-Lab) to insecticide in the laboratory. An increase in resistance ratio from 1.71-fold in the F1 generation to 22.54-fold in the F8 generation of the EB-Sel population was observed compared to the Unsel-Lab (F8) population. The EB-Sel and Unsel-Lab populations were treated with their respective lethal and sub-lethal concentrations which resulted in an extended development period, decreased larval survival, and adult emergence along with increased morphological abnormalities in adults. Significant reductions were observed in both male and female longevity, fecundity, egg hatching, net reproductive rate (R0), intrinsic rate of increase (rm), and finite rate of increase (λ) in EB-Sel and Unsel-Lab populations. Higher concentrations of the insecticide also reduced the relative fitness (Rf) of S. litura larvae, with maximum effect at LC50 of the EB-Sel population where the Rf value was 0.32 compared to the Unsel-Lab population. Both populations have been affected by emamectin benzoate exposure, however, the impact was more pronounced in the EB-Sel population indicating fitness costs. Our results suggested the fitness cost linked to emamectin benzoate resistance in S. litura which might favor managing insecticide resistance by reducing the frequency of resistant alleles by removing selection pressure. Consequently, our research provides significant insights to devise better pest management strategies for S. litura.

Spotlight hunting of invasive deer (Axis axis) selects for individuals with greater reproductive value in a protected area of north-eastern Argentina

Spotlight hunting of invasive deer (Axis axis) selects for individuals with greater reproductive value in a protected area of north-eastern Argentina

Mathematical analysis of Ebola considering transmission at treatment centres and survivor relapse using fractal-fractional Caputo derivatives in Uganda

In this article, we seek to formulate a robust mathematical model to study the Ebola disease through fractal-fractional operators. The study thus incorporates the transmission rate in the treatment centers and the relapse rate, since the Ebola virus persists or mostly hides in the immunologically protected sites of survivors. The Ebola virus disease (EVD) is one of the infectious diseases that has recorded a high death rate in countries where it is endemic, and Uganda is not an exception. The world at large has suffered from this deadly disease since 1976 when it was declared epidemic by the World Health Organization. The study employed fractal-fractional operators to identify the epidemiological patterns of EVD, especially in treatment centers and relapse. Memory loss and relapse are mostly observed in EVD survivors and this justifies the use of fractional operators to capture the true dynamics of the disease. Through dynamical analysis, the model is proven to be positive and bounded in the region. The model is further explicitly shown to have a solution that is unique and stable. The reproduction number was duly computed by using the next-generation matrix approach. By taking EVD epidemic cases in Uganda, the study fitted all parameters to real data. It has been shown through sensitivity index analysis that the transmission rate outside treatment centers and relapse have a significant effect on the endemic state of the disease, as they lead to an increase in the basic reproduction ratio.

On a Symmetry-Based Structural Deterministic Fractal Fractional Order Mathematical Model to Investigate Conjunctivitis Adenovirus Disease

In the last few years, the conjunctivitis adenovirus disease has been investigated by using the concept of mathematical models. Hence, researchers have presented some mathematical models of the mentioned disease by using classical and fractional order derivatives. A complementary method involves analyzing the system of fractal fractional order equations by considering the set of symmetries of its solutions. By characterizing structures that relate to the fundamental dynamics of biological systems, symmetries offer a potent notion for the creation of mechanistic models. This study investigates a novel mathematical model for conjunctivitis adenovirus disease. Conjunctivitis is an infection in the eye that is caused by adenovirus, also known as pink eye disease. Adenovirus is a common virus that affects the eye’s mucosa. Infectious conjunctivitis is most common eye disease on the planet, impacting individuals across all age groups and demographics. We have formulated a model to investigate the transmission of the aforesaid disease and the impact of vaccination on its dynamics. Also, using mathematical analysis, the percentage of a population which needs vaccination to prevent the spreading of the mentioned disease can be investigated. Fractal fractional derivatives have been widely used in the last few years to study different infectious disease models. Hence, being inspired by the importance of fractal fractional theory to investigate the mentioned human eye-related disease, we derived some adequate results for the above model, including equilibrium points, reproductive number, and sensitivity analysis. Furthermore, by utilizing fixed point theory and numerical techniques, adequate requirements were established for the existence theory, Ulam–Hyers stability, and approximate solutions. We used nonlinear functional analysis and fixed point theory for the qualitative theory. We have graphically simulated the outcomes for several fractal fractional order levels using the numerical method.

Bursaphelenchus xylophilus Venom Allergen-Like Protein BxVAP1, Triggering Plant Defense-Related Programmed Cell Death, Plays an Important Role in Regulating Pinus massoniana Terpene Defense Responses.

Bursaphelenchus xylophilus (pine wood nematode, PWN), a migratory plant-parasitic nematode, acts as an etiological agent, inflicting considerable damage to pine forests worldwide. Plant immunity constitutes a crucial factor in resisting various pathogenic invasions. The primary defensive responses of host pines against PWN infection encompass terpene accumulation, defense response-related gene expression, and programmed cell death. Venom allergen-like proteins (VAPs), as potential effectors, are instrumental in facilitating the successful colonization of PWNs. In this study, we investigated the inhibition of B. xylophilus VAP (BxVAP1) expression by RNA interference in vitro. Following BxVAP1 silencing, the reproduction rate and migration rate of the PWN population in Pinus massoniana decreased, the expression of the α-pinene synthase gene was induced, other terpene synthase and pathogenesis-related genes were inhibited and delayed, the peak times and levels of terpene-related substances were changed, and the degree of cavitation in P. massoniana was diminished. Transient expression of BxVAP1 in Nicotiana benthamiana revealed that BxVAP1 was expressed in both the cell membrane and nucleus, inducing programmed cell death and the expression of pathogen-associated molecular pattern-triggered immunity marker genes (NbAcre31 and NbPTI5). This study is the first to demonstrate that silencing the BxVAP1 gene affects host defense responses, including terpenoid metabolism in P. massoniana, and that BxVAP1 can be recognized by N. benthamiana as an effector to trigger its innate immunity, expanding our understanding of the parasitic mechanism of B. xylophilus.

Impact of heat stress on female reproduction in farm animals: challenges and possible remedies

Global warming poses significant challenges to agriculture, particularly within the livestock industry. Heat stress in animals refers to the physiological and metabolic distress experienced when environmental heat causes an animal’s body temperature to exceed its thermoneutral zone. Heat stress has a significant detrimental impact on reproductive outcomes, posing a direct threat to the profitability of livestock operations. Heat stress disrupts the normal hormonal balance essential for reproduction in female livestock, adversely affecting events of folliculogenesis and embryogenesis. As a result, the developmental competence of oocytes is compromised, which is crucial for successful fertilization and reproduction. Consequently, heat stress can lead to issues such as immature oocytes, atypical or sluggish embryonic development, silent estrus, and increased pregnancy loss causing a decline in reproductive rates and livestock owners face substantial financial losses. Despite using various cooling strategies, such as water sprinkler systems, cooling shades, and cooling devices, these measures are often insufficient to restore normal reproductive rates. Therefore, it is crucial to implement and explore novel strategies to enhance reproductive efficiency during periods of heat stress. Potential mitigation techniques include estrus synchronization, artificial insemination, hormonal alterations, embryo transfer, genetic engineering, sophisticated breeding strategies, the use of nutraceuticals, and changes in management practices. This review aims to consolidate recent findings on the adverse effects of heat stress on female reproduction, especially in tropical environments, and to evaluate potential strategies for improving summer fertility of livestock. Bangladesh Journal of Animal Science 53(3): 77-100, 2024

Optimizing tuberculosis control: a comprehensive simulation of integrated interventions using a mathematical model

Tuberculosis (TB) remains a formidable global health challenge, demanding effective control strategies to alleviate its burden. In this study, we introduce a comprehensive mathematical model to unravel the intricate dynamics of TB transmission and assess the efficacy and cost-effectiveness of diverse intervention strategies. Our model meticulously categorizes the total population into seven distinct compartments, encompassing susceptibility, vaccination, diagnosed infectious, undiagnosed infectious, hospitalized, and recovered individuals. Factors such as susceptible individual recruitment, the impact of vaccination, immunity loss, and the nuanced dynamics of transmission between compartments are considered. Notably, we compute the basic reproduction number, providing a quantitative measure of TB transmission potential. Through this comprehensive model, our study aims to offer valuable insights into optimal control measures for TB prevention and control, contributing to the ongoing global efforts to combat this pressing health challenge.

Modeling of Malware Propagation Under the Clustering Approach in Scale‐Free Networks

ABSTRACTIn this paper, we present an innovative malware propagation model that combines epidemic spread and clustering techniques, specifically designed for scale‐free networks. The proposed model builds upon the susceptible–exposed–infected–recovered (SEIR) framework, effectively simulating the dissemination of malware across the network. Our research demonstrates a notable reduction in the rate of malware transmission compared to the traditional SEIR model, with this improvement in containment being attributed to the incorporation of clustering methodologies. We also calculate the basic reproduction ratio (R0) for the proposed model, which offers valuable insights into the potential consequences of malware outbreaks within the network. By exploring variations in key parameters, we deepen our understanding of the model's behavior under different conditions. Furthermore, we evaluate the role of clustering in mitigating malware spread, highlighting its significant effectiveness in reducing the overall impact of infections.

Fitness and Survival of the Fall Armyworm, Spodoptera Frugiperda (Lepidoptera: Noctuidae) on Maize in West Java, Indonesia

An important pest of maize is a new invasive species called Spodoptera frugiperda, also known as the fall armyworm (FAW), causing a considerable economic impact in Indonesia since 2019. This insect has a large host range, a quick generation time at the right temperature, a high rate of reproduction, and a high dispersal capacity. In population ecology and pest management, fitness and survival are crucial. This research was aimed to determine some biological aspects and demographic statistics of three FAW populations (lowland, midland, and highland) in a laboratory setting with 25 ± 2 °C, 75 ± 5% relative humidity, and a 12:12 (L:D) hour photoperiod. Findings indicated no variation in the length of the FAW life stage or its reproductive capacity. Nonetheless, notable variations were noted in the average fecundity of females, with FAW of the highland population laying the most eggs (1242.1 eggs). FAW had the shortest mean generation time (T), the highest intrinsic rate of increase (rm), the finite rate of increase (λ), and the highest net reproductive rate (R0) of the highland population. Overall FAW collected from highland, midland, and lowland can adapt well when brought to a laboratory with a constant temperature at 25 ± 2 °C without detriment to the parameters of the life table. The knowledge gained from this study is crucial for managing FAW because it improves comprehension of its life cycle and adaptability to various altitudes, enabling us to take appropriate action to stop its spread.

Modeling the Transmission Dynamics of the Ebola Virus: Effects of Quarantine and Vaccination

Quarantine and vaccination of individuals suspected of exposure to infectious agents are fundamental public health strategies that have historically been employed to mitigate the transmission of contagious diseases within human populations. This study introduced a modified SEIVQRD deterministic model to evaluate the population-level effects of quarantine and vaccination on individuals potentially exposed to the Ebola virus. The study showed that the Model exhibits backward bifurcation when . This implies that even when the reproductive number An unstable endemic and a stable disease-free equilibrium can coexist in less than one. This phenomenon arises from imperfect quarantine and indicates that while is necessary for adequate infection control; it is no longer sufficient and creates additional challenges for effectively controlling Ebola. Furthermore, the sensitivity analysis revealed that the quarantine effectiveness parameter and the parameter related to the isolation of vulnerable individuals had less influence on the incidence of new Ebola cases. However, vaccinating non-quarantined susceptible individuals significantly affects the infection burden and can lower the reproductive value to less than one. Overall, the Model emphasizes the critical role of vaccination in reducing Ebola virus transmission. Although quarantine measures alone may not be sufficient, their combination with vaccination can significantly reduce infection rates.

Merinos in Poland – an analysis of breeding condition, selected performance traits and perspectives for the protection of genetic resources in relation to the country’s total sheep population

The purpose of the study was to analyse the breeding condition and performance traits of merino sheep belonging to three breeds in 2008-2022. The experimental material consisted of data derived from annual reports published by the Polish Sheep Breeding Association on breeding of three merino breeds: Polish Merino, Coloured Merino, old-type Polish Merino and data on the number and distribution of flocks, as well as data on the implementation of the sheep genetic resources protection programme from the database of the National Research Institute of Animal Production covering the period of the last 15 years. Analysing the population size over the last 15 years, significant changes were observed in the breed structure of the Merino sheep population. The implementation of conservation programmes and the opportunity to obtain subsidies for conservation breeds have had an impact on the breeding of these breeds in our country. Currently, the largest share of the merino sheep population is represented by the old-type Polish merino. Merino breeding has a regional and large-scale profile, concentrated in the historical areas of their maintenance, in Wielkopolska and Kujawy, usually in flocks of about 100 dams. Reproduction rates expressed by maternal prolificacy were found to be in line with the breed pattern. The Polish merino and the old-type Polish merino were distinguished by similar parameters of reproductive traits and higher fertility as well as rearing indices than those of the coloured merino. The coloured merino is the breed with the highest fertility and breeding performance. Body weight of lambs was higher for the white varieties. However, reproductive and meat performance indices show the potential of merino sheep in the context of lamb production, which is currently the main focus of sheep production in Poland.