Animal vaccination is the immunisation of a domestic, livestock or wild animal. [1] The practice is connected to veterinary medicine. [1] The first animal vaccine invented was for chicken cholera in 1879 by Louis Pasteur. [2] The production of such vaccines encounter issues in relation to the economic difficulties of individuals, the government and companies. [3] Regulation of animal vaccinations is less compared to the regulations of human vaccinations. [3] [4] Vaccines are categorised into conventional and next generation vaccines. [5] [6] Animal vaccines have been found to be the most cost effective and sustainable methods of controlling infectious veterinary diseases. [6] In 2017, the veterinary vaccine industry was valued at US$7 billion and it is predicted to reach US$9 billion in 2024. [7]
Animals have been both the receiver and the source of vaccines. Through laboratory testing, the first animal vaccine created was for chicken cholera in 1879 by Louis Pasteur. [8] Pasteur also invented an anthrax vaccine for sheep and cattle in 1881, and the rabies vaccine in 1884. [8] Monkeys and rabbits were used to grow and attenuate the rabies virus. [9] Starting in 1881, dried spinal cord material from infected rabbits was given to dogs to inoculate them against rabies. [10] The infected nerve tissue was dried to weaken the virus. [11] Subsequently, in 1885, the vaccine was given to a 9-year-old boy infected with the rabies disease, Joseph Meister, who survived when no one had before. [10] The French National Academy of Medicine and the world saw this feat as a breakthrough, and thus many scientists started to collaborate and further Pasteur's work. [10] [9]
An indirect view of animal vaccinations is seen through smallpox. This is because the vaccine given to humans was animal based. Smallpox was a deadly disease most known for its rash and high death rate of 30% if contracted. [12]
Edward Jenner tested his theory in 1796, that if a human had already been infected with cowpox that they would be protected from smallpox. It proved to be true and thus started the pathway to the eradication of the disease. [13]
Through the World Health Organization's (WHO) eradication effort, at least 80% of people were vaccinated in every country. [10] Subsequently, case finding and then ring vaccination was used, resulting in smallpox becoming the first eradication of a disease through vaccination in 1980. [10]
The main issues in relation to the vaccination of animals is access and availability. [14] Vaccines are the most cost-effective measure in preventing disease in livestock populations, although the logistics of distributing vaccines to marginalised populations is still a challenge. [15] [16]
Most smallholder farmers' (SHFs) livestock in marginalised populations (MPs) die as a result of a disease, they do not reach their full potential, or they transmit a disease. [3] The root of this issue could be prevented or controlled by increasing the accessibility to animal vaccines. [3] Livestock are necessary to an estimated 600 to 900 million poor farmers in the developing world. [3] [17] This is because the animals provide food, income, financial reserve and status. [17]
The diseases have been characterised into diseases that cause economic losses, government-controlled diseases, and neglected diseases, which all link to availability. [3] The economic losses category entails necessary vaccines in developing countries normally produced by the private sector that make little to no profit, these companies require community support to continue producing. Whereas, government-controlled diseases are controlled by government policy, the main issue here is if the vaccine is expensive it therefore becomes less available to poor farmers. [3] Furthermore, there are some animal diseases which have been neglected as they mainly only affect poor communities, and thus will not be profitable. This is because producers target the largest markets first to ensure their return on investment (ROI). [14] For example, the reason why dog transmitted rabies is taking time to eradicate is because it only affects the developing world, thus it is not able to be produced on a large and profitable scale. [3]
Some other issues include but are not limited to: economic barriers, political barriers, technical and scientific barriers, regulatory barriers, field use barriers, and social and perception barriers. [7]
There are possible solutions in terms of the issues in the sector of animal vaccinations. These include innovations in both the scientific and the regulatory fields. It has been suggested that regulations are converged between regions and all animal vaccines can be standardised with the same RNA or DNA backbone. It has been found that there needs to be a better mutual understanding between regulators, academia and industry. [14]
Some other solutions include: free rabies vaccine programs, subsidies as needed, form partnerships across regions (mainly in terms of vaccine banks), a decrease in government taxes, providing positive incentives for disease recording, and building partnerships between global and local manufacturers.
The production of vaccines for animals and humans has always been linked, this relationship has been coined 'One Health', as at least 61% of all human pathogens originate from animals. Two main examples of this link are the rabies and smallpox vaccines. In many cases vaccinating animals is important not only to the animals' health but also to human health and prosperity. The term zoonotic disease defines a disease that can be transferred from animals to humans. [18]
A current and prominent example of a zoonotic disease is rabies. [19] It is spread from an animal to humans and other animals through saliva, bites and scratches. [19] Both domestic and wild animals can catch the rabies disease. Over 59,000 humans die of the disease each year, with 99% of cases occurring because of dog bites. [19] There has been less than 20 documented cases of rabies survival without treatment to date. [19] The majority of cases and deaths occur in Africa and Asia, as a result of limited healthcare. [20] The vaccine for rabies can be administered prior or post to being infected, as a result of the long incubation period of the disease. [20]
The proactive approach of vaccinating stray dogs, which helps to prevent the disease at its source, has been seen to be the most cost-effective prevention of rabies. In Bangladesh there was a mass dog vaccination campaign between 2010 and 2013, this resulted in a 50% decrease in rabies related deaths. [20]
WHO has created the campaign of 'Zero by 30', to reduce the number of humans that die from dog related rabies to zero by 2030.
During the last decade 75% of infectious diseases in humans had an animal origin. [21] Thus, the notion coined 'One Health' was created, where both human and animal health is seen as being equally important. An example of a 'One Health' vaccine, where it can be distributed to both humans and animals, that is currently going through clinical trials is Rift Valley Fever. Associate Professor Warimwe from the University of Oxford states that this approach accelerates the design and development of the vaccine, and it also saves time and money. [22]
The development of animal vaccines has less regulatory requirements than human vaccines. This has resulted in less time and money involved in the creation and production of animal vaccines. The human vaccine development process generally takes 10 to 15 years, whereas the animal vaccine process only takes an average 5 to 7 years to produce. [23] Albeit, the ability to prioritise potential vaccine targets and the use of studies to test safety is less in the animal vaccine production compared to human vaccines. [24]
Pets has grown at a fast rate over time as owners are concerned for their companion animals' health. [24] In contrast farmed animal vaccines generally only produced when there is a zoonotic disease or it had a significant effect on international trade. Rather than producing for the sole reason of caring for the animal such as with pets, farmed animals are vaccinated for human safety and economic means.
This clearly links to pharmacovigilance (monitoring the effects of licensed drugs). The largest database being the Veterinary Medicines Directorate (VMD) in the UK. Although, the vast majority reported were in terms of companion animals.
There is no standard metric for quantifying the global burden of animal diseases, no standard method for determining the cost effectiveness of a certain animal vaccine, and no cost-effectiveness thresholds in general. Thus, it can be difficult to prioritise animal vaccine development.
As a result of less regulation, some vaccines have been found to contain impurities. An example of this was the rabies vaccine containing a significant amount of Bovine serum albumin (BSA). [25] BSA can cause severe allergic reactions that can lead to death.
The main conventional vaccines are Live-attenuated and Inactivated. [6] Live-attenuated vaccines use a weakened form of the virus or bacteria that causes the disease. This form of inoculation is the closest to the actual infection, and thus it has been seen to have a stronger effect than the other types of conventional vaccines. [26] Albeit, there have been some safety issues related to live-attenuated vaccines. There is a potential for unintended outcomes if another being other than the target species takes the vaccine, and there have been instances where this type of vaccine creates false positives when animals are tested and therefore rids a country of their disease free status (as has been seen through Foot and Mouth Disease, FMD). [6] Furthermore, inactivated vaccines consist of bacterians of one or more bacterial species, or killed viral strains. The inactivation occurs through chemical or physical treatment which either denatures the protein or damages the nucleic acid. This type of vaccine is more stable and less expensive than live-attenuated vaccines, although it does not provide as effective long-term protection because the pathogen cannot replicate. [6]
Genomic analysis of pathogens and furthered understanding of the mechanisms of pathogens has resulted in the discovery of antigens and the development of recombinant veterinary vaccines. Currently the pathogens' genome is sequenced, the genes that cause the disease is identified, the genes of interest are cloned, a recombinant is constructed, and then one of three types of vaccines is produced (DNA vaccines, Subunit vaccines, Vectored vaccines). DNA vaccines induce antigen production in the host. It is a plasmid that contains a viral, bacterial or parasite gene. The animal's immune system recognises the expressed protein as foreign, and this can lead to a cellular or humeral response. DNA vaccines overcomes the safety concerns of live-attenuated vaccines. Furthermore, subunit vaccines are short, specific pathogens that cannot replicate. Even though this vaccine is termed as safe, it does not replicate and thus studies have shown issues in relation to yield. Vectored vaccines is another next generation vaccine. This type of vaccine uses a vector to deliver either one or multiple proteins to the immune system of the animal. Currently, there is research being undergone into plant vaccines, which come under the category of vector vaccines.
Domestic chickens have been vaccinated against Pasteurella anatis using bacterial outer membrane vesicles purified by hydrostatic filtration dialysis. Several such vaccines have successfully produced immunity. Antenucci et al. 2020 demonstrates the most consistent product and effective immune provocation among HFD OMV processes, but overall HFD has yet to prove itself against other vaccine production techniques. Nonetheless, it is a very promising line of research as of 2021 [update] . [27]
The Vaccinations Guidelines Group (VGG) of the World Small Animal Veterinary Association (WSAVA) have defined the core, non-core and not recommended vaccinations for dogs and cats. [28]
Core vaccines protect animals against severe global diseases. Where rabies is endemic the associated vaccine is treated as being in the core category. [28]
Core | Non-Core | Not Recommended | |
---|---|---|---|
Dogs | Canine distemper virus (CDV) Canine adenovirus (CAV) Canine Parvovirus (CPV-2) | Parainfluenza virus (PI) Bordetella bronchiseptica (Bb) Leptospira interrogans | Coronavirus |
Cats | Feline parvovirus (FPV) Feline calicivirus (FCV) Feline herpesvirus (FHV-1) | Feline leukaemia virus (FeLV) Chlamydia felis Feline immunodeficiency virus (FIV) |
Vaccination is the administration of a vaccine to help the immune system develop immunity from a disease. Vaccines contain a microorganism or virus in a weakened, live or killed state, or proteins or toxins from the organism. In stimulating the body's adaptive immunity, they help prevent sickness from an infectious disease. When a sufficiently large percentage of a population has been vaccinated, herd immunity results. Herd immunity protects those who may be immunocompromised and cannot get a vaccine because even a weakened version would harm them. The effectiveness of vaccination has been widely studied and verified. Vaccination is the most effective method of preventing infectious diseases; widespread immunity due to vaccination is largely responsible for the worldwide eradication of smallpox and the elimination of diseases such as polio and tetanus from much of the world. However, some diseases, such as measles outbreaks in America, have seen rising cases due to relatively low vaccination rates in the 2010s – attributed, in part, to vaccine hesitancy. According to the World Health Organization, vaccination prevents 3.5–5 million deaths per year.
A vaccine is a biological preparation that provides active acquired immunity to a particular infectious or malignant disease. The safety and effectiveness of vaccines has been widely studied and verified. A vaccine typically contains an agent that resembles a disease-causing microorganism and is often made from weakened or killed forms of the microbe, its toxins, or one of its surface proteins. The agent stimulates the body's immune system to recognize the agent as a threat, destroy it, and recognize further and destroy any of the microorganisms associated with that agent that it may encounter in the future.
A zoonosis or zoonotic disease is an infectious disease of humans caused by a pathogen that can jump from a non-human to a human and vice versa.
Q fever or query fever is a disease caused by infection with Coxiella burnetii, a bacterium that affects humans and other animals. This organism is uncommon, but may be found in cattle, sheep, goats, and other domestic mammals, including cats and dogs. The infection results from inhalation of a spore-like small-cell variant, and from contact with the milk, urine, feces, vaginal mucus, or semen of infected animals. Rarely, the disease is tick-borne. The incubation period can range from 9 to 40 days. Humans are vulnerable to Q fever, and infection can result from even a few organisms. The bacterium is an obligate intracellular pathogenic parasite.
The smallpox vaccine is the first vaccine to have been developed against a contagious disease. In 1796, British physician Edward Jenner demonstrated that an infection with the relatively mild cowpox virus conferred immunity against the deadly smallpox virus. Cowpox served as a natural vaccine until the modern smallpox vaccine emerged in the 20th century. From 1958 to 1977, the World Health Organization (WHO) conducted a global vaccination campaign that eradicated smallpox, making it the only human disease to be eradicated. Although routine smallpox vaccination is no longer performed on the general public, the vaccine is still being produced to guard against bioterrorism, biological warfare, and mpox.
Herd immunity is a form of indirect protection that applies only to contagious diseases. It occurs when a sufficient percentage of a population has become immune to an infection, whether through previous infections or vaccination, thereby reducing the likelihood of infection for individuals who lack immunity.
Immunization, or immunisation, is the process by which an individual's immune system becomes fortified against an infectious agent.
In biology, immunity is the state of being insusceptible or resistant to a noxious agent or process, especially a pathogen or infectious disease. Immunity may occur naturally or be produced by prior exposure or immunization.
Vaccinia virus is a large, complex, enveloped virus belonging to the poxvirus family. It has a linear, double-stranded DNA genome approximately 190 kbp in length, which encodes approximately 250 genes. The dimensions of the virion are roughly 360 × 270 × 250 nm, with a mass of approximately 5–10 fg. The vaccinia virus is the source of the modern smallpox vaccine, which the World Health Organization (WHO) used to eradicate smallpox in a global vaccination campaign in 1958–1977. Although smallpox no longer exists in the wild, vaccinia virus is still studied widely by scientists as a tool for gene therapy and genetic engineering.
Serial passage is the process of growing bacteria or a virus in iterations. For instance, a virus may be grown in one environment, and then a portion of that virus population can be removed and put into a new environment. This process is repeated with as many stages as desired, and then the final product is studied, often in comparison with the original virus.
Anthrax vaccines are vaccines to prevent the livestock and human disease anthrax, caused by the bacterium Bacillus anthracis.
Artificial induction of immunity is immunization achieved by human efforts in preventive healthcare, as opposed to natural immunity as produced by organisms' immune systems. It makes people immune to specific diseases by means other than waiting for them to catch the disease. The purpose is to reduce the risk of death and suffering, that is, the disease burden, even when eradication of the disease is not possible. Vaccination is the chief type of such immunization, greatly reducing the burden of vaccine-preventable diseases.
An attenuated vaccine is a vaccine created by reducing the virulence of a pathogen, but still keeping it viable. Attenuation takes an infectious agent and alters it so that it becomes harmless or less virulent. These vaccines contrast to those produced by "killing" the pathogen.
The eradication of infectious diseases is the reduction of the prevalence of an infectious disease in the global host population to zero.
The rabies vaccine is a vaccine used to prevent rabies. There are several rabies vaccines available that are both safe and effective. Vaccinations must be administered prior to rabies virus exposure or within the latent period after exposure to prevent the disease. Transmission of rabies virus to humans typically occurs through a bite or scratch from an infectious animal, but exposure can occur through indirect contact with the saliva from an infectious individual.
Rabies is a viral disease that causes encephalitis in humans and other mammals. It was historically referred to as hydrophobia due to the symptom of panic when presented with liquids to drink. Early symptoms can include fever and abnormal sensations at the site of exposure. These symptoms are followed by one or more of the following symptoms: nausea, vomiting, violent movements, uncontrolled excitement, fear of water, an inability to move parts of the body, confusion, and loss of consciousness. Once symptoms appear, the result is virtually always death. The time period between contracting the disease and the start of symptoms is usually one to three months but can vary from less than one week to more than one year. The time depends on the distance the virus must travel along peripheral nerves to reach the central nervous system.
The prevalence of rabies, a deadly viral disease affecting mammals, varies significantly across regions worldwide, posing a persistent public health problem.
In animals, rabies is a viral zoonotic neuro-invasive disease which causes inflammation in the brain and is usually fatal. Rabies, caused by the rabies virus, primarily infects mammals. In the laboratory it has been found that birds can be infected, as well as cell cultures from birds, reptiles and insects. The brains of animals with rabies deteriorate. As a result, they tend to behave bizarrely and often aggressively, increasing the chances that they will bite another animal or a person and transmit the disease.
The social history of viruses describes the influence of viruses and viral infections on human history. Epidemics caused by viruses began when human behaviour changed during the Neolithic period, around 12,000 years ago, when humans developed more densely populated agricultural communities. This allowed viruses to spread rapidly and subsequently to become endemic. Viruses of plants and livestock also increased, and as humans became dependent on agriculture and farming, diseases such as potyviruses of potatoes and rinderpest of cattle had devastating consequences.
Ring vaccination is a strategy to inhibit the spread of a disease by vaccinating those who are most likely to be infected.