Newsletter February 2012

In my previous newsletters, i indicated that there are a number of pathogens threatening our pigeons. Viruses are in a sense problematic, because of the usually few curatives (healing) can be undertaken. In case of a virus infection we can only treat the secondary infection to minimalize the discomfort for the pigeon. The only way to prevent these attackers is vaccination. But this is only possible if there's a vaccine available. In a few cases there are still no vaccines, not yet anyway. An example is the Circovirus. There is today no vaccine available for this virus, with serious consequences. I will explain in the following newsletters the most common viruses.

In this newsletter I will address the smallpox virus. In the first part of this newsletter I will explain the scientific side of this virus.

Smallpox

1. Scientific information

2. Personal comments - practice

Scientific information

blood warts, which often occur under the wings.

The fact that variola is host specific means that pigeons cannot contract the smallpox virus from, for example, chicken, canaries or even sparrows.

Mode of infection

As said, pigeons can only be infected with the pigeon variola. An exception are chicken, they can have an immunological reaction to the pigeon variola. Smallpox occurs frequently among pigeons. Even with wild or city pigeons. Traditionally, this disease bursts out in the late summer or the fall. The cause of this lies within the fact that in that time of year the insects and bugs who spread the virus, are more common, like mosquitos. But even the red feather mite can spread the same virus.

Besides the insects which spread the virus, a large factor in the spreading of variola is the fights among pigeons. Basket infections can provide the outburst of the virus in program players. The outburst occurs after one week of the flight on which the pigeons were infected. The performances of the pigeons during that flight are not affected. The incubation, the time between the infection and the actual outburst of the virus, is usually seven to ten days, with an extension to 20 days.

Fights and bites of insects make sure that the virus can penetrate the body of the pigeon. Pigeons that are infected with variola excrete the virus through saliva, tears and sometimes through the manure. The virus is released after the destruction of the epithelial cells and spreads further.

Phenomena

We distinguish two manifestations of smallpox:

1.     The skin manifestation.

Usually the little smallpox occurs on the skin, with the preferred sites of the skin surrounding the eyes or the corners of the mouth of the beak. But even, although less frequent, around the ears, the cloaca and the paws. In short, on the little feathered skin areas.

It starts with little nodules the size of a matchstick button, or vesicles which can grow to the typical lesions, consisting of overgrowth of skin cells that can be dropped.

2.     The manifestation of diphtheria.

In which overgrowth of the mucous membrane in the beak happens, including the tongue and the pharynx. These so-called pseudomembranous, (yellow) lesions can be mistaken by pigeon lover for a canker contamination. It is to be said that when there's a variola infection, it is easy to contract a canker contamination. But the lesions in the beak are primarily caused by smallpox. Pigeons won't die from a smallpox infection itself, but if the overgrowth surrounding the beak and eyes grows too serious, the pigeons are not able to feed themselves an because of this, will die from starvation.

Whether the pigeons get a serious overgrowth, or just a single pox, it all depends on the resistance of the pigeon and the virulence (infection power) of the virus. Sometimes the infection stays limited to a single pox. This happens among the pigeon who were once vaccinated, but at the time of contamination had little resistance. Other (not vaccinated) pigeons in the dovecot can in the meantime, develop serious overgrowth of the eyes, nasal caps, beak and in the mouth and pharynx.

The diagnosis is easy to establish through the clinical manifestations. Differential diagnostic, this has to be considered, Trichominiasis, Candidiasis or a Herpes infection. Sometimes the inflammation lesions of a fight can mimic a starting pox. But usually the symptoms are obvious.

Treatment

The disease is, as said, a viral infection and antibiotic as a treatment does not help. Still, in a lot of cases, serious cases, antibiotics can be used to treat and contain the effects of secondary bacterial infections. For the virus itself, it's no cure.

In case of severe overgrowth, you can try to remove the overgrowth by using a sharp spoon. It should be noted that it is best to remove just the upper layer to prevent unnecessary bleeding. After this, you can smear some 2% iodine solution or a solution of iodine in glycerin on a swab, on the lesions. This has to be repeated several days consecutively. In case of just minor overgrowth, the best solution is smearing the iodine solution without removing the upper layer of the skin. The pox will dry out over time and drop off after four to six weeks. The pigeons will recuperate fair to good. Exceptions are the pigeons who suffer from overgrowth under the nasal capes.

Naturally you cannot treat the pox near the eyes with the iodine solution if there is a chance that the iodine reaches the eye.

Prevention

The only way to prevent the pigeons from an outbreak of the smallpox is vaccination. A pigeon that contracted the variola virus once will be protected for the rest of its life against this virus. This is not the case for vaccinated pigeons. It is recommended that the vaccination for smallpox is repeated every year. If the pigeons remain in a contaminated environment on a regular base, the vaccination will be stretched out on a ‘natural' way through exposure to the wild virus. If exposure to the wild virus is omitted, which is usually the case, the protection through the vaccination will weaken, which means that the pigeons are more or less susceptible for the variola virus.

The pigeons are required to be at least six weeks old to get a sufficient immune response from the vaccination. It is possible to vaccinate through the feather follicle method and the combination Colombovac PMV-pox vaccination. It is not wise to combine this vaccination with, for example, a paratyphoid vaccination because of the to be expected vaccination reaction.

When you use the feather follicle method, you have to be careful when you're pulling out a dozen feathers not to damage the skin and cause any bleeding. If this does happen, you have to change to the other leg because of the pigeon's safety. If you don't, there is a reasonable chance the vaccination is incomplete, because the vaccine washes away with the blood.

With a brush dipped in the vaccine, you have to brush the vaccine on the skin in the opposite direction of the feather growth. After the vaccination the pigeon can react on the vaccine after eight to ten days, which means that the pigeon can sit together. During this reaction, it is not recommended to let the pigeons fly in case of any losses.

It is recommended to vaccine well before the flight season.

Vaccinated pigeons can still be carriers of the virus, so it is advised to vaccine all birds.If you chose to vaccine trough the feather follicle method, the pigeons cannot be bathed for the week after the vaccination. Further, it is important to check for an actual vaccination reaction. This is really important to see if the vaccine is working. The follicles in the skin will thicken and color.

Additional measures

The smallpox virus is little sensitive for moisture, air, drought and the cold. So the virus can remain in the dovecot for a long time. A good and well functional disinfection comes in handy to fight off these viruses (like Virkon S, Halamid). Infected pigeons have to be separated from the rest to increase the infection pressure. Infected pigeons cannot be used to fly in the game. Mosquitos are lifelong carriers of the variola virus, so insect control is really wanted.

In the next part of the newsletter I will talk elaborate about the practical aspects of a smallpox infection.

Good luck,

Peter Boskamp