Recent Advances in Disease Diagnosis for Sustainable Livestock and Poultry Production
Disease control, high production, product quality, and reasonable production costs have been the recent main goals of the poultry industry. Hence, meeting per capita consumption and welfare to humans necessitates continuous efficient and goal-oriented healthcare to control disease spread and decrease the application of antibiotics.
The livestock play a very important economic and socio-cultural roles for the wellbeing of rural households, such as food supply, source of income, asset saving, source of employment, soil fertility, livelihoods, transport, agricultural traction, agricultural diversification and sustainable agricultural production since the time of ancient civilization and domestication of animals. Livestock production is predominantly familiar being chickens, pigs, goats, cattle, horses, buffaloes and sheep the main species. Beyond the economic function, each livestock species also performs social and cultural functions. Sustainable livestock production means making livestock systems economically more efficient and striking balance between meeting the growing demand of animal origin products and reducing to the minimum the negative side effects and externalities from the livestock sector. In order to be optimal, livestock systems need to promote advancements in the technological and infrastructural aspects of the sector and, at the same time, institutions and experts should support the progression of knowledge with policies that define and shape sustainable livestock development from a social, economic and environmental perspective. A number of factors may adversely affect the stability and health of animal populations. Environmental stresses, poor nutrition and infectious agents play serious constraints on animal productivity, especially in the developing world, resulting in several disease condition and heavy economic losses. Infectious diseases, in specific, threaten the health and well being of wildlife, livestock, and human populations. The actual impact of any given infectious disease depends on morbidity and mortality patterns, susceptible host range and subsequent losses like death, loss of productivity, infertility etc. In addition infectious diseases of animal population carry global public health risks of sporadic human zoonotic infections or emergence of a pandemic strain. As a whole, animals are thought to be the source of more than 70% of all emerging infections .
SIGNIFICANCE AND CHALLENGES OF DISEASE DIAGNOSIS
Prompt and accurate detection of infectious agents is necessary, since many livestock diseases have severe economic consequences, yet local veterinary diagnosis can be confounded by diseases that share similar clinical signs. Therefore, the presence of notifiable diseases is usually confirmed in dedicated laboratories, using assays recommended by the World Organization for Animal Health (OIE). These tests are typically performed, analyzed and interpreted by trained personnel, according to the recommendations of the OIE Manual of Diagnostic Tests and Vaccines for Terrestrial Animals (Terrestrial Manual) (2). Although these laboratory-based tests can provide rapid results (3), samples must be transported to the laboratory, which can negatively affect the quality of the specimens and delay or even hinder immediate crucial decisionmaking and the process of disease control The pathogen detection is an important step for the accurate diagnostics, successful treatment of animal infection and control management in farms and field conditions. Serious efforts are focused on the early detection of the causative agents, considering that the timely recognition would prevent their spread to large animal populations in huge geographic areas. Thus, the development of novel, powerful diagnostic assays is a basic issue today in veterinary research and animal health care. Current techniques employed to diagnose bacterial pathogens in livestock and poultry include classical plate based methods and conventional serological methods as enzyme linked immunosorbent assays (ELISA). Isolation and propagation of virus is an effective method for diagnosis but it is time consuming. Although, molecular techniques such as polymerase chain reaction (PCR) and real time PCR (RT-PCR) have also been proposed to be used to diagnose and identify relevant infectious disease in animals, these DNA-based methodologies need isolated genetic materials and sophisticated instruments, being not suitable for field use. Consequently, there is strong interest for developing new swift point-of-care biosensing systems for early detection of animal diseases with high sensitivity and specificity .
Advances in Veterinary disease diagnosis
The development of simple, portable diagnostic devices is now considered a priority for animal diseases. The global veterinary diagnostics market is estimated to expand at a compound annual growth rate of 8.6% from 2016 to 2021, to reach US$ 6.71 billion by 2021 . Molecular biology offers a range of new methods, which are able to accelerate and improve the diagnosis of infectious diseases in animals and man. The new assays provide possibilities for rapid diagnosis, since the detection of pathogen can be completed within hours. Concerning direct detection, various molecular approaches are introduced, like classical PCR robotics, portable PCR machines, improved sample enrichment, amplification without thermo cycling, macro and microarrays are under development.
i) Nucleic acid hybridization and real-time polymerase chain reaction (qPCR) assays have been applied for routine diagnosis of a large number of diseases. Real-time PCR chemistry (qPCR) is now an established tool to detect and quantify nucleic acid in laboratory settings, offering superior analytical sensitivity for the detection of acute disease, in comparison to serologically based assays. As a result of this routine laboratory use, much progress has been made recently in transitioning qPCR. The realtime PCR allows estimation and quantification of pathogen load. Such estimation opens new paths not only for the diagnosis, but also for studying pathogenesis. The measurement of viral load is also important when estimating the effects of anti-viral treatments, especially in animal virology.
ii) Diagnostic serology: Antibodies have the capacity to actually bind to antigens which are unique to specific microorganisms. Because antibodies are only produced after an encounter with a foreign antigen, the presence of specific antibodies is indicative of exposure to, if not infection with, a certain micro-organism. Such a detection of specific antibodies in blood and other body fluids forms the basis of diagnostic serology. Serological techniques have been used for well over half a century for the presumptive diagnosis of infectious diseases.
iii) Microarrays: Microarray refer to the collection of microscopic spots containing picomoles (10-12 moles) of a specific sequences (DNA, cDNA, cRNA, oligonucleotides), known as probes, which hybridize with specific nucleic acid sequence called targets, labelled with a fluorescent dye. Use of microarrays during outbreaks and and/or disease surveillance would save time and help in early decisions to control the spread of disease. One main pathogenesis in terms of gene expression studies during host pathogen interactions.
iv) Genotyping by Pyrosequencing: This is a real-time de novo DNA sequencing method catalyzed by the cascading actions of four kinetically balanced enzymes:
i) DNA polymerase ii) ATP sulfurylase iii) firefly luciferase and iv) apyrase. The phylogenetic analysis by sequencing the 16srRNA gene or the advent of new microbial identification easier along with culture-independent studies (or metagenomics) for exploration of all microbial genomes. Pyrosequencing based diagnostic assays were developed for the detection of H5N1 viruses that are capable of rapidly determining an isolate’s clade, strain, receptor specificity, glycosylation status and HA0 cleavage site . As more is learned about the molecular basis for influenza virulence, pyrosequencing based assays may be developed subsequently, to rapidly screen for virus isolates that may pose a greater risk to animal and human populations. v) Biosensors: These are attractive solutions for fast and efficient infectious disease diagnostics due to their simplicity, possible miniaturization and potential ability for real-time analysis. Biosensor recognizes a target biomarker, characteristic for particular pathogen, via an immobilized sensing element called bioreceptor (monoclonal antibody, RNA, DNA, glycan, lectin, enzyme, tissue and whole cell). The bioreceptor is a crucial component as its biochemical properties assure high sensitivity and selectivity of the biomarker detection and permit to avoid interference from other microorganisms or molecules present in the tested sample. Biosensor methods has been widely used for the detection of various animal and poultry pathogens, by targeting various pathogen associated biomolecules like cell wall components, pathogen specific proteins/toxins, extracellular components like flagella etc.
CONCLUSIONS
In conclusion, the early identification of infectious diseases in domestic and wild animals is crucial to improve control program. A major thrust in the development of animal disease diagnostics has been toward rapid methods that can provide a definite answer in the earliest possible time period. To achieve such rapidity, the methods should fulfill the prerequisites of speed, simplicity, sensitivity, specificity, reproducibility and low cost. More rapid advances in biotechnology, such as nucleic acid probe techniques, will no doubt allow for rapid and economical identification in the future, but at present they are still considered as experimental techniques, will no doubt allow for rapid and economical identification in the future. Such a rapid, powerful and internationally standardized molecular diagnosis contributes to the reduction of losses caused by the pandemic/transboundary diseases among animal populations.
Compiled & Shared by- This paper is a compilation of groupwork provided by the
Team, LITD (Livestock Institute of Training & Development)
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