Friday, May 18, 2012

Mareks Disease – why Small Breeders are undecided over Inoculation

Mareks Disease – why Small Breeders are undecided over Inoculation

by:  Imogen Reed

An affiliate of the Herpes Virus family, Mareks is a voracious disease dispensed through the respiratory tract via microscopic airborne feather dander. Highly contagious; if unidentified in a stricken bird it has the capacity to decimate a flock. It manifests in several ways. Classical Mareks is signified by progressive asymmetrical paralysis of one or more limbs. Typically, it infiltrates the sciatic nerve and the affected bird is rendered immobile. This can lead to trampling from other members of the flock and wasting through the inability to source food and water. On a visceral level, it inflicts tumours on the skeletal muscle and organs, predominantly on the liver, kidneys, heart and lungs. The young are most susceptible, with most related deaths occurring between 8 and 20 weeks of age. There is no treatment for Mareks. Birds that contract the disease invariably die.

Mareks is endemic within the bird population. The nature of transference (inhalation) means no direct contact is required between victims. As it’s difficult to control a bird’s exposure to the disease, vaccination is widely recommended. A simple subcutaneous (under the skin) injection is all that’s necessary. Early immunisation is the key for heading off any problems in animals, just as an asbestos survey can prevent underlying issues further down the line in buildings. Guidelines suggest inoculation on the day of hatch or as soon as a new bird enters the flock. The vaccine is non-sterilising and consequently will not prevent transmission of the virus, only reduce the amount of disease shed in the dander. It is therefore important to rear young birds separately, until they develop a natural ‘age resistance.’ This usually occurs around five months. Hygienic standards must be optimal. Environmental conditions should be ideal, namely not overcrowded. If chicks are subjected to stress, it can have an abject effect on their response to the vaccine.

Small Breeders
There is still a great deal of indecision regarding vaccination. For large commercial enterprises it is essential, and many will argue the same applies to the small breeder. Considering the virulence and brutality of the disease, vaccination would seem the sensible option, yet many small scale and hobbyist breeders forgo inoculation. Across discussion forums and websites, an extensive strong belief in the safety of a closed flock is suggestive of why many dismiss vaccination. It is widely held assumption that by avoiding genetically susceptible breeds, and maintaining high standards of hygiene and husbandry, the flock will be spared. Although compelling, there are further dissuading factors.

The need to inject
The Marek vaccine is only available for purchase in minimum stocks of 1000 vials. This presents an uneconomical buy for a breeder with only fifty to sixty birds. The nature of the vaccine also requires a degree of pre-planning. The vaccine is freeze dried and delivered with an accompanying diluent for re-hydration. Once the two parts are mixed the vaccine must be administered within half an hour. After an hour the live virus element dies, rendering the vaccine ineffective. Apart from the pressure of limited time, the act of injecting is potentially daunting for the inexperienced. With such a delicate creature as a day old chick, a fear of not securing the correct technique and apportioning hurt is an effective discouragement.

For the small breeder, poultry can represent a low monetary value. When coupled with a high reproductive rate, owners may exhibit a more casual outlook, accepting a degree of loss as a common outcome. In addition, with a naturally strong genetic resistance occurring as the flock ages, inoculation could seem extraneous.

A matter of choice
Inoculate or not? It seems a matter of personal choice. Veterinary professionals ardently encourage vaccination for all chicks in an effort to control the spread of the disease on a much wider scale. Each breeder will invariably follow their own mind, a decision based on either personal viewpoint, or the strength of debate which continues to rage for each side of the argument. Those that have witnessed the ravages of the disease first hand will inevitably continue to vaccinate their flock. Those with commerce in mind will do the same to minimise financial losses. Perhaps, in the end, it will come down to how a breeder relates to the bird; whether it’s seen as a business commodity or something far more personal.