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At this stage – after all the many trials and tribulations – one would have thought that all vaccination procedures should have been regular, safe and straightforward without any questions or controversies. However this is not so and knowing pigeon fanciers, I realize that it was rather naive on my part to think thus. Good old wishful thinking comes to mind. Pigeon fanciers as a group are a rather fluctuating group of people. This comes about because some leave the sport, other pass on to evergreen pastures and a few raw beginners start up. On top of that, in the effort to become top dog, most fanciers will try new ideas or procedures each new season. Everything is changed. Alterations are made to the loft, new pigeons are bought and brought in, new medicines or vitamin mixtures are tried, other exercise programs are followed and so on. Nothing wrong with that and some times these changes do have the desired effect but mostly they do not. Why that is so, is the theme for another debate on a different day.
Within all these alterations there are, however, a few fundamentals that must never change. One of these is correct vaccination.
It is understandable that fanciers will cease to vaccinate if they do not perceive signs of disease in their birds for a number of years. But even though the ordinary man-in-the-street lacks the precise knowledge explaining the epidemiology of virus diseases or any other diseases for that matter that it is not excusable. If he is a serious fancier it is his responsibility to read, phone or otherwise search till he finds out precisely what to do.
Fanciers generally rely on their own experiences, the well-meant but sometimes short-sighted advice of friends, the 'secrets' whispered in confidence, the pigeon shops who are, after all, in business to make money and occasionally they might even get their information from people that really know!
To clear the muddle, let's spend a little time discussing vaccinations. In order to make the process intelligible we have to take a few steps back and first return to basic biology.
Diseases are principally caused by three types of infective micro-organisms i.e. the viruses, bacteria and protozoa. There are other organisms that cause disease; such as fungi, or organisms whose size fall between those of viruses and bacteria, or even those that are smaller than viruses. But when a pigeon becomes ill it is usually as a result of infection by one of the three major groups. Vaccines are manufactured against some of these diseases.
A vaccine is a manmade product administered with the express intention of stimulating the pigeon's body to increase its immunity to a specific infective disease. Vaccination is purely the process of using such a product. Vaccines are usually made against bacteria and viruses. Very few vaccines are manufactured against protozoa because it is very difficult to do so and the success rate is extremely low. (Which is why for example, no successful vaccine has ever been made against human malaria). The manufacture of vaccines against viruses are usually the most successful (Herpes virus, Circovirus and HIV of humans are striking exceptions) with a result stronger immunity following their use than from bacterial vaccines. Most bacterial vaccines are made from dead or inactivated organisms, excite a weak immunity and the initial dose usually has to be repeated or boosted a few times. It should thus be evident why vaccine production against paratyphoid is so difficult and fraught with breakdowns.
Vaccine manufacture always employs either dead (inactivated) or attenuated (weakened) live micro-organisms. It might be expedient at this stage to say a few words about the making of a vaccine. It is not a straight-forward procedure and many steps have to be taken, not least of which is testing for safety, which as one can imagine, is extremely important. Attenuated means that the micro-organisms have been weakened in the sense, that they can no longer produce disease in their original host.
This is done by repeatedly growing them in other media, for example in embryonated eggs. Following that, prolonged testing has to be done to see that the vaccine is capable of stimulating immunity formation, that the vaccine organism will not revert back to its original pathogenic state, nor that it will spread to other animals once vaccinated. Only when all these conditions have been satisfactorily met, can the vaccine be released.
Live attenuated vaccines are usually better than killed (inactivated) vaccine. This is because the live vaccines multiply in their host's body and exist there for an extended period without causing disease. Exposure to the vaccine organisms triggers the immune system and gives the body a favourable opportunity to mount a strong immune reaction; so strong that many of the live vaccines only need to be administered once per year or even once per lifetime. The dead vaccines on the other hand do not stimulate the immune system to such an extent and require repeated boosting to affect a similar response.
Vaccines manufactured using live viruses usually excite the best immunity. Killed virus vaccines must be administered more than once, with a second shot usually given 4-6 weeks after the first. To induce a good immunity this is usually essential.
Live bacterial vaccines are difficult to make and are, as a rule not so effective. Dead bacterial vaccines very often have to be administered in a series of injections for maximal effect.
As coccidiosis, crop canker and pseudo-malaria are protozoal diseases no vaccines are made against them.
Let us consider the action of those few vaccines specifically made to fight the diseases of pigeons. These are against pigeon pox, paramyxovirus and paratyphoid. In addition, some fanciers are using the fowl adenovirus vaccines on their pigeons in an attempt to protect their birds from adenovirus infections types I and II and Young Bird Sickness. As far as I am aware no scientific studies have been done testing the efficacy of this procedure but anecdotal reports suggest that it has a beneficial effect. We have used the vaccine extensively and have seen no ill effects.
As a disease entity, pigeon's pox is well known and easily recognized by all experienced fanciers. Pigeon pox is almost universal and is found wherever the mosquitoes that spread the disease occur. The pox virus is very host specific meaning that the strain of pox virus that attacks pigeons will not attack chickens, turkeys, canaries or any other bird and the pigeon pox virus will affect only pigeons and doves. The reverse is also true in that the virus of other birds will not attack pigeons or doves. This species specificity goes even further. A few years ago the specific strain of pigeon pox virus in South Africa mutated, with the effect that the locally made vaccine was no longer able to protect pigeons from contracting the disease.
The vaccines imported from Europe were equally ineffective and a new vaccine had to be manufactured by a local laboratory. This was done and fanciers can once again protect their birds against pox with confidence.
The different names given to the pox lesions because of their locality difference – wet pox in the mouth area and dry pox elsewhere – are caused by the same virus.
There are a few different approaches to pox vaccination.
1. Some fanciers elect to do nothing. This approach hopes that the birds will not get the disease in the racing season but if they do, that will not be very serious and quickly over. I believe that this method is too fatalistic and cannot condone it. A serious disadvantage is that infected bird could be sent to a race before the classical symptoms become evident and those birds could then easily be lost. Another problem is that the course of the disease may run over an extended period as it spreads slowly from pigeon to pigeon, ruining one's chances of a competitive season. Many fanciers have pulled hair and gnashed their teeth when this has happened!
2. Certain fanciers believe that a natural infection is preferred to vaccination and in the resting season, will introduce an infected bird with active pox into the loft and allowing it to infect the others. Spread of the disease in these cases occurs mainly when pigeons fight, resulting in lesions particularly of the mouth, or by the action of biting insects such as mosquitoes when lesions occur on the head, particularly the eyelids and/or feet. The process has distinct disadvantages as the disease tends to spread very slowly leading to a drawn-out period when the birds are unwell.
At other times the infection can be too severe and ruin the pigeon permanently. An eye can be so inflamed and infected that it becomes discoloured or even lost or the beak can be so badly damaged that loss of one or both mandibles occur. This happens mainly to very young or stressed pigeons. (Of course this can occur as well when the first approach is adopted.) Note that mosquitoes are not necessary for spreading the virus within the loft. They are essential for introducing the disease into the loft but the pecking that occurs naturally will spread the disease once present in the loft.
These disadvantages can be prevented by vaccinating the pigeons from the pox lesion of an introduced bird. Using a stout needle which is first pressed into the lesion, a scratch is made ventrally on the breast, making sure that the skin is punctured. This should be sufficient and will allow growth of the pox lesion at a chosen site while a strong immunity develops.
As genus of Paramyxovirus (PMV) has been known for more than eighty years as the cause of Newcastle disease in poultry. When the virus mutated about twenty years ago and caused the first outbreaks of Para-myxovirus infection in pigeons (or paramyxo), no vaccine was available. But the chicken industry had been using various vaccines against Newcastle for many years and it was thought that chicken vaccine might protect pigeons against the mutated virus also.
Alexander in England and other scientists in Belgium did extensive trials with the vaccines and found that the dead oil based injectable vaccine was able to protect the pigeons. The live Lasota water based droplet vaccine was also found to be effective but the requirement of having to be repeatedly administered and the fear of using live vaccine in non-intended recipients has caused Lasota vaccine to fall out of favour and to be banned in some countries.
After some years vaccines, using the virus extracted from sick pigeons, were manufactured and released. These homo-logous vaccines were also made with dead virus antigens.
Certain rules must be followed to obtain a good immunity.
1. It is essential that the vaccine be given as soon as possible after weaning – to be repeated after 4-6 weeks. This holds true for all the injectable forms of dead virus vaccines. Some manufactures claim that only one injection is necessary but I have repeatedly seen immunity breakdowns following a single procedure. It is advisable to administer a third injection at the start of the race season.
2. Lasota vaccine must be administered via a droplet in the nostril and eye. Placing the vaccine in the drinking water – albeit with milk or any other substance – is not effective. A second Lasota vaccination needs to be administered 4-6 weeks after the first and thereafter every three months. This is essential to maintaining a strong localized immunity.
3. Annual vaccination is recommended but older birds need only one injection. Birds vaccinated with Lasota need to be kept on the routine as outlined above.
4. There is no advantage when the Lasota vaccine is followed by dead vaccine injection one month later. The two vaccines work in different ways and a Lasota vaccination cannot be boosted by a dead vaccine injection and vice versa. If one chooses to go the dead vaccine route two injections are still required.
Paratyphoid has, for many years, been the scourge of many lofts in Europe particularly. Should an outbreak of the disease occur, current advice is threefold? Where possible eradicate all carriers, medicate for ten days with Baytrill and vaccinate the remainder.
I do not believe that the disease is as prevalent as thought in South Africa and do not recommend routine vaccination. Whenever the disease has been shown to be present by culture results however, the routine as outlined above should be followed. At all other times the regular use of probiotics, apple cider vinegar or lemon juice will go far in keeping paratyphoid at bay.
In the past paratyphoid vaccine manufacture has met with many problems. For many years dead vaccine only was available but Chevita has recently introduced a live paratyphoid vaccine. An annual booster injection is recommended.
Young Bird Sickness (YBS) has a very disruptive effect on a loft of young pigeons. The disease syndrome appears to be caused by the effect that circovirus has on young pigeons, destroying or seriously damaging their immune systems. Following immune system damage the pigeons fall prey to various pathogens such as E.coli, canker, herpes virus, adenovirus, PMV, Salmonella and other. Many cases of YBS have been found to be infected with adenovirus.
Vaccines against circovirus do not at this stage exist. In chickens adenovirus infection causes Egg Drop Syndrome (EDS) and it was thought that cross-immunity to a heterologous species could possibly develop in pigeons following its use, in a similar way that the chicken vaccine against Newcastle protect pigeons against PMV. If that were so, many cases of YBS could be prevented or lessened.
With this in mind, killed virus vaccine for poultry adenoviruses has been advocated for a number of years and preliminary results suggest a definite favourable response. In those lofts where the EDS vaccine is used it seems that YBS has markedly declined. There are a few essentials to bear in mind. 1. It is imperative that the weanlings are vaccinated at the first opportunity. It is important that the young pigeons must be able to respond to the vaccine and form some immunity before the circovirus should attack their immune systems. 2. Because it is dead (inactivated) vaccine we recommend a second injection 4-6 weeks following the first. If combined with PMV vaccine a third shot at the commencement of the race season, is recommended.
By Dr Wim Peters