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Control of “Exotic” Newcastle Disease in Southern California

02/18/2019

The authorities involved in attempting to control the ongoing outbreak of velogenic viscerotropic Newcastle disease (vvND or "exotic" ND) have been less than effective in suppressing and eradicating the outbreak in three contiguous counties in Southern California. From late May 2018 through February 7th 2019 there have been 363 diagnoses of vvND involving "backyard flocks". This term is a euphemism for fighting cocks and the distinction must be recognized since it has implications for both control and the required approach to effectively limiting the danger of transmission to commercial poultry. To date, four relatively small commercial operations in Riverside County have been affected but it is only a matter time, given the mobility of fighting cocks and their owners that introduction of the virus into a larger and County has recorded 212 outbreaks and adjoining San Bernardino County has experienced 109 cases since May 2018. A total of 62 cases were identified in August compared with 20 in September, 18 in October and 17 in November suggesting a natural decline in incidence associated with the level of immunity or reduced movement. A surge in cases occurred in December with 43 cases followed by 86 in January. The reason for this increase has yet to be explained. In fairness to both APHIS and CDFA it is apparent that they are confronted with a lack of cooperation from the owners of fighting cocks since they are engaged in illegal activity.

Apart from keeping score and posting bilingual notices on various websites neither USDA-APHIS nor the California Department of Food and Agriculture have achieved any meaningful control on a practical level to effectively stabilize and then reduce the incidence rate. The State Veterinarian for California announced a pre-emptive depopulation of all "backyard poultry" in affected clusters in each of three counties at the end of 2018. This declaration in all probability led to dissemination of infection as fighting cocks, regarded by their owners of having high value, would have been transported from the pre-announced areas. It is understood that a single outbreak in Utah County, UT resulted from clandestine transport of fighting cocks from an affected area in Southern California.

The obvious solution to the problem of an alarming increase in incidence rate is to create a solidly immune status in the population of fighting cocks. Both live attenuated and inactivated vaccines with proven efficacy are available. The emphasis should now be on achieving immunity in this population of birds rather than after-the-effect diagnosis of outbreaks followed by depopulation of surviving birds.

When confronted with a disease situation in a discrete population associated with an illegal activity it is obviously necessary to accept realities and address the issue. An analogy might be made with distribution of needles to intravenous drug users to reduce the incidence rate of hepatitis and HIV. Clean needles distributed to users in urban areas will reduce the incidence rate of blood-borne infections albeit indirectly supporting an illegal activity.

Neither fighting cocks nor their Newcastle disease will simply evaporate over time. The authorities have wasted ten months and should by now recognize the endemic status of vvND in the fighting cock population of Southern California. There is nothing "exotic" in this situation and waiting for the infection to "burn out" places commercial flocks at risk. It is more a matter of luck and circumstance rather than intent that the infection has not emerged in a large complex or spread to commercial flocks beyond Southern California.

It is high time that authorities should engender the cooperation of owners of fighting cocks and encourage vaccination to be carried out by owners. It is noted that in the 1971 outbreak of vvND involved 1,340 flocks, including Goldman's Egg City in Moorpark, at that time holding two million hens door-to-door inspection and deployment of vaccination teams probably extended the outbreak through dissemination of virus. This lesson should be applied to the current outbreak. If more than 95 percent of breeding, rearing and fighting birds in the Southern California population can be solidly immunized, the incidence rate will fall sharply and the ongoing risk to commercial poultry and the export market will diminish. Now is the time for realism and concerted action.