Veterinary Epidemiology and Zoonosis-vat : Strategies to control and eradication

Strategies to control and eradication

STRATEGIES OF DISEASE CONTROL AND ERADICATION

The deliberate killing of a minority of infected animals to protect the well majority of healthy population.
The selective slaughter of diseased animals or reactors is to be found at by immunodiagnostic screening test.

When there is difficulty in application of diagnostic techniques to diagnose the diseases in the population in order to carry out selective slaughter, complete depopulation of an affected restricted population carried out to protect the species at large.
- Example: FMD in deer population in Stanislans National Forest in California in 1924 there was no alternative, but to deer depopulation (22,214 deer killed)

Quarantine implies the enforced physical separation from the healthy population of infected or potentially infected individuals, their products or items, they may have contaminated. Such measures may be applied at national, regional or herd level and they may be voluntary or required by legislation.
It is applied at the international level to prevent transmission of infectious or vectors from one country to another.
The Office International Des Epizootics was established in Paris 1924 to standardize the Veterinary Quarantine procedures and regulations throughout the world.
- Example: Imported cattle are usually placed in quarantine stations for designed period (usually maximum incubation period) prior to being transferred to the property of the purchasers to ensure (by clinical and for serologic monitoring) that they are not infected with undesirable agent such as the virus of FMD.
Similarly, dogs are quarantined for a period to ensure they are free of rabies, before admitting them to rabies-free countries.

The mass treatment approach to disease control depends upon the availability of safe and cheap therapeutic agents.
Antibiotics, Anthelmintic and other drugs like hyper immune serum are used (therapeutically) to treat diseases, and are administered (prophylactically) at times of high risk to prevent disease and thus to increase productivity.
- Example: Sulfonamides in drinking water for coccidiosis in chickens.

Mass immunization has been one of the most effective forms of directed action against diseases undertaken in veterinary medicine.
The interesting areas for future development of mass immunization as a disease control tool are methods for mass administration of vaccines that dispense with problems of needle hygiene (such as use of jet injection guns) or that eliminate the need to handle animal individually.
- Example: Stable vaccines incorporated in water or feed and vaccines administered by mucosal route as aerosols.

Animals can be removed from high risk areas where infections are endemic.
This control strategy is implemented in tropical countries where hosts are seasonally migrated from areas in which biological vectors are active.

The mixed grazing of susceptible animals with stock that are genetically or immunologically resistant to helminths reduces pasture contamination to an acceptable level.
The alternative grazing of a pasture with different species of livestock again reduces pasture contamination.
The sequential grazing at different times of resistant and susceptible animals of the same species reduces pasture contamination.

Biological vectors: Infectious diseases transmitted by biological vectors can be controlled removing the vectors. Insect vectors can be killed with insecticides.
Control of mechanical vectors: Living organisms that mechanically transmit infectious agents can be controlled by destruction and disinfection.

Fomites can be disinfected to prevent the transmission of infectious agents.
Fomites include farm equipment, surgical instruments and sometimes drugs themselves.
Food is heat-treated (Example: Pasteurization of milk) to destroy microbes and their heat-sensitive toxins to prevent food borne infections.

The presence of one organism within a niche can prevent its occupation by another organism.
This is epidemiological interference, and has been investigated, experimentally in the poultry industry where suspensions of endogenous intestinal microbes have been fed to one-day-old chicks to prevent colonization of their digestive tract by virulent Salmonella spp., Campylobactor jejuni and E.coli.
This technique of control has the advantage over prophylactic antibiotic chemotherapy that antibiotic resistance is not encouraged.

The diseases of intensively produced animals, particularly cattle and pigs are major contemporary problems which can be controlled only when epidemiological investigations have identified the 'determinants associated with inadequate management.
Poor hygiene has been incrirninated as the most important environmental cause. All necessary steps should be taken to maintain and improve the environment and management, so as to reduce and eradicate the diseases.

Many diseases of both agricultural and companion animals have a variable heritable components.
The disease may be determined predominantly by genetic screening to identify disease animals by screening either the total population at risk or the part that is mainly responsible for the maintenance of a particular disease.
The latter techniques are commonly applied in veterinary medicine, because animals of superior germ plasm are concentrated in pedigree nuclei that are used for breeding.
The incidence of some infectious disease can be reduced by selective breeding.

Disease can be reduced in intensively reared livestock by disinfecting infected premises and by treating infected animals or removing them from the animal unit.
Uninfected animals can be produced by caesarean section and by hatching uninfected eggs from poultry.
These combined techniques are termed minimal disease methods.

Last modified: Wednesday, 16 May 2012, 5:14 AM