Vaccines - yes or no?
Zsolt Talaber, DVM
Part 1
The use of vaccinations is intended to provide individual specimens and the whole flock with protection against the disease in question. Because of its importance, we will repeat again here that with the threat of circovirus infection, individual vaccinations must be administered at the youngest possible age.
Nowadays it is impossible to imagine economic and successful pigeon-breeding anywhere in the world without regular use of vaccinations. In addition, active protection against paramyxovirus is obligatory in most countries.
The vaccines used in pigeon-breeding usually protect against one particular pathogen, and so we refer to them as monovalent vaccines. Vaccines that are effective against two pathogens at once we call bivalent, and we can also find examples of this in pigeon care. Vaccines that contain more than two active ingredients are called polyvalent, but in pigeon-breeding these are not common.
Monovalent vaccines
Vaccines against paramyxovirus
It is with regard to vaccines used against diseases caused by paramyxovirus that demand is best satisfied. (Indeed, sometimes almost too well, leading to a competitive battle between pharmaceutical companies producing the various vaccines - which often try to influence even local pigeon associations.) There are products available specifically approved for pigeons, but many also use the vaccines produced against Newcastle disease (avian pneumoencephalitis) in chickens. The latter are usually injections, but are also distributed in a form that can be administered orally.
Vaccines containing the Newcastle disease (avian pneumoencephalitis) virus
These vaccines do not contain pigeon PMV, but its "parent" virus, the original Newcastle disease virus (most commonly the so-called La Sota strain). Their use is very widespread, despite the fact that products specifically made for pigeon PMV are also available. Their prevalence is partly thanks to their relatively low price, and partly to the fact that previously, before the appearance of specific pigeon PMV vaccines, these represented the only defence against the virus.
As the Newcastle disease (NCD) virus is only related (albeit closely) to pigeon PMV, in pigeons the capacity of such vaccines to provide immunity does not in principle reach that of PMV-specific vaccines. (This is particularly true of vaccines used in drinking water.) Still, the majority of these vaccines gives good protection, and thus their use with adequate regularity provides sufficient immunity against pigeon PMV. This can be stated with confidence, based on pigeon fanciers' experience over many years, all the more so because in recent years vaccines containing the original Newcastle disease virus (e.g. the La Sota strain) have appeared and gained approval for use with pigeons.
The earliest possible time for their use varies, but some can already be administered at the age of three weeks.
Vaccines containing pigeon-specific paramyxovirus
These vaccines actually contain the pigeon PMV that causes the illness in pigeons. So, assuming they are used professionally, it is from them that we can expect the highest level and longest duration of protection. According to their official description, the earliest they can usually be used is when birds are five weeks old.
Note
Protection against pigeon PMV is obligatory in many countries. Which vaccine is officially accepted, however, varies from country to country, and such regulations are known to change. Before applying the vaccination, we should ask about the current requirements, if we do not want to encounter unpleasant surprises at races and fairs.
Many fanciers follow the practice of alternating the virus strain of the vaccine used. First they administer the vaccine against Newcastle disease, often choosing one that is added to drinking water. Two or three weeks later they use the vaccine specific to pigeon PMV. Our experience suggests that this is a good technique which results in a high level of protection.
Vaccines used against pox virus
When using a vaccine against pox we should take great care to immunize every member of the flock at the same time. It can be given from the age of five weeks, and an annual booster injection is recommended. As the virus survives in the environment for a long time, specimens in a yard that has once been infected should be given systematic vaccinations for at least 8-10 years afterwards.
Some products should be used in a different way from the other vaccines, by rubbing them into the feather follicules. (This is described in detail in the section on pigeon pox).
Anti-paratyphoid vaccines
These vaccines generally contain the strain Salmonella typhimurium var. Copenhagen. Sadly, although demand for them would be high, in many countries anti-typhoid products are only accessible with great difficulty, if at all.
There are vaccines that contain killed or weakened salmonella bacteria, with their inherent benefits and disadvantages.
Vaccines containing killed pathogens
Advantages
Put less of a burden on the flock. If absolutely necessary, they can be used to vaccinate a flock already displaying symptoms, and their effect is not ruined by an antibiotic administered at the same time.
Disadvantages
Elicit a rather weaker immunization result, and the protection they offer is weaker and lasts for a shorter time. At least three vaccinations are required in the first year, which then have to be repeated every six months.
Vaccines containing live, attenuated pathogens
Advantages
Provide a higher level of protection. A single shot can provide adequate protection, and it is enough to repeat them every 9-12 months.
Disadvantages
They put a greater burden on the flock, and induce more unwanted reactions after the vaccination. Antibiotics must not be used within five days before and after the vaccination. If this does prove necessary, we can expect the vaccination to lose some of its effectiveness, so it is advisable to give a booster shot to such specimens a few weeks later.
In general, anti-paratyphoid vaccines can be given from the age of 4-6 weeks.
Note
It is worth noting - especially given the difficulty of acquiring them - that customized, so-called flock vaccines against paratyphoid can be ordered from veterinary laboratories specialising in this. After a sample is taken, the strains currently present in the flock are cultured artificially, and a vaccine is produced from this bacterial culture. One great advantage of such vaccines is that they defend precisely against the strain causing the problem in the given pigeon flock, and so allow us to achieve the highest possible level of effectiveness. Their disadvantage is that they are more expensive than mass-produced vaccines, and their preparation takes time.
Bivalent vaccines
By using bivalent vaccines we can save precious time, for two reasons. Firstly, we only have to perform one vaccination instead of two, which itself is time-saving, and also means that the flock is only burdened half as much. Secondly, we can save a week or two in developing protection against illnesses, which bearing in mind the circovirus threat to chicks is far from being an insignificant consideration.
In pigeon care we typically find bivalent vaccines that protect against paramyxovirus and pox virus. We can generally use these for the first time at around the age of 5-6 weeks.
Polyvalent vaccines
Polyvalent vaccines are widely available in dog and cat care, for example, but not yet common for pigeons. Polyvalent pigeon vaccines are at the testing stage in some countries, but research into their effectiveness and their official registration are tasks for the future.
Over a number of years I had the opportunity to try out a certain polyvalent vaccine, which contained five different agents (against paramyxovirus, paratyphoid, herpes, mycoplasma and chlamydia). Everyday experience showed that the vaccine provided adequate protection against all five diseases, if it was administered three times in the first year of life. (When the pigeon was three weeks old, then 6-8 weeks, then about six months.) Afterwards the birds vaccinated three times in their first year had to be vaccinated once a year. It was when we vaccinated older birds that had not received the same vaccine when young that we saw unquestionably negative reactions appear (languishment, dejection, possibly more severe symptoms, even death). These negative side-effects were not observed with specimens vaccinated from a young age, and these birds acquired a long-lasting high level of immunity against all five diseases.
When discussing polyvalent vaccines, we should add that in theory these vaccines have disadvantages. Firstly, the level of resistance that develops to each illness is lower, because after the multi-component vaccine is administered the energies and attention of the body's immune system are divided. This can be compensated for by using the polyvalent vaccines three or even four times in the first year of the pigeon's life.
Another disadvantage is that a polyvalent vaccine causes a larger burden for the body all at once than a monovalent one, and so can only be given to a flock in a fine state of health, and even then we can expect negative reactions in the days after the vaccination. This is particularly true if the polyvalent vaccine contains bacterial agents.
Note
It is generally true of all vaccines that if at all possible, we should immunize the entire flock, or at least all specimens in a particular loft, at once. Another golden rule is that the vaccinations should be completed at the very least 3-4 weeks before the pairing or racing season. If administered close to the breeding season, the vaccination can make eggs infertile, while during racing season it can lead to a decline in performance, or be dangerous because of the negative phase .
Negative phase
For 2-3 weeks after vaccination, we must be particularly careful that the vaccinated birds not be exposed to any kind of source of infection. For this is when they pass through the so-called negative phase , during which their system is highly sensitive to infection. The essence of the negative phase is that the inoculated virus or bacterium immediately neutralizes some of the antibodies present from maternal origin or from an earlier vaccination, and it is only 10-14 days later that the vaccine induces a level of immunity higher than the initial one. That is to say, for about two weeks after the vaccination is given, there will be less protective material in the system than there was previously!
Finally, it is very useful if we raise the active protection of our pigeons to the highest possible level in the first year of their lives with booster shots.
Vaccines - yes or no?
Zsolt Talaber, DVM
Part 2
The length of the effect of preventive vaccination is affected by a number of factors. It depends on the immune state of the vaccinated pigeon, on the vaccination taking place in satisfactory fashion, on the number of vaccinations, and not least on the vaccine itself, or rather on the strength of the antigen effect of the pathogen that the vaccine inserts into the body. The latter depends on the type of pathogen, and on whether the vaccine contains dead or live pathogens. Before we go into the details, the answer to the second question is that the protection given by paramyxo vaccines is relatively short - even the strongest products do not offer protection for much more than 12 months. Not in principle, and even less in practice. Therefore an annual booster injection is justified.
Of course, this does not mean that 13 months after a vaccination it is certain that a pigeon will fall ill if it succumbs to an infection. The protection that develops in response to the vaccination is strongest 2-3 weeks afterwards, then decreases over time, but even after a year and a half there will remain a certain amount of the antibodies in the pigeon's body. This low level of protection can be broken by a strong viral infection, however, leading to illness. Whether illness develops from infection, that is whether a pathogen can proliferate in the pigeon's body, depends on the virulence of the attacking pathogen and on the level of protection. The lower the level of antibodies, that is the longer it is since the vaccination took place, or the stronger the pathogen, the greater the likelihood of illness. It is possible that even after a year and half a weaker infection will not cause damage, and equally that after only 10 months a strong, "wild" strain of a virus can break through a relatively strong antibody level and cause illness. The chances of these are even greater if the circumstances of the vaccination happen to decrease its effectiveness.
The degree of artificial protection and the success (or lack of success) of vaccinations:
In general, pigeons that have been vaccinated, that is immunized, acquire protection against the disease targeted by the vaccination in question. It is highly important for us to know, however, that this artificially induced protection is never 100% guaranteed ! Not for one individual specimen, and certainly not for the flock as a whole.
Below we list the factors that can cause pigeons to develop a disease despite having been vaccinated against it. We will take injections against the disease caused by the paramyxovirus as an example, of course.
Reasons for vaccinated pigeons later developing the disease:
Errors in vaccination
- inadequate vaccine: use of vaccines containing the wrong strain of paramyxovirus
- inadequate vaccine: fault in manufacture
- vaccine past its expiry date
- vaccine that is in principle still valid, but that has been stored incorrectly
- injection in the wrong place (e.g. within skin, in the air)
- injection at the wrong time (when specimen is ill or exhausted)
- polluted syringe (active ingredient is ruined)
- specimen infected with parasites
- wrong vaccination dose (inadequate amount of vaccine administered)
- vaccine ruined (put in water that is too hot before being injected)
- specimen accidentally left out (specimens mixed up at time of vaccination)
- specimen left out for other reasons (e.g. pigeon not in yard at time of vaccination)
Errors unrelated to vaccination
Pathogen-related:
- overwhelming infection, attack of too great a mass of pathogens at once, which is capable of breaking through even the protection provided by the vaccination
- long-lasting, continuous infection, which exhausts the immune system
- attack of a particularly wild strain of the virus or bacterium, which is more virulent than the average
- a mutation, or transformation, of the virus
- attack of a bacterium of the same type as the vaccine but of a different subtype (e.g. a new strain of salmonella imported from abroad)
Because of inadequate operation of the immune system:
- metabolic causes (e.g. lack of selenium)
- presence of circovirus infection
- individual, congenital immune deficiency
From the above it is clear that innumerable errors can occur even during the vaccination. But even if there is no such negligence, it is almost impossible that every member of our flock acquire protection from the vaccination . (This raises our attention to the fact that while localized protection or vaccination is essential, on its own - without continuous prevention of epidemics and the necessary hygiene - it is not enough to protect the health of the whole of the flock.) Why is it so important to draw attention to this reality? Because it can make it seem as if the vaccination is unsuccessful , thereby undermining our faith in the necessity and effectiveness of vaccines, possibly causing some fanciers to stop using them. This would be a grave mistake, however, because even if an illness appears in a vaccinated flock, it causes immeasurably less damage than if the flock is unvaccinated and therefore unprotected.
In the light of the above, an annual booster injection is definitely warranted. The recommended vaccination programme against paramyxovirus illness is as follows: young birds should be vaccinated as early as possible, especially in places where circovirus infection poses a threat. Some paramyxovirus vaccines can be used from the age of 3 weeks. (Certain vaccines can be used from the age of 1 day!) Subsequent booster injections are required annually, but in endemic areas an extra reminder vaccination is strongly recommended in the first year of life, 3-6 weeks after the first injection.