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Newcastle Disease in Southern California

09/08/2018

With no sign of resolution, the extended outbreak of Newcastle disease in Southern California has reached approximately 130 cases.  Outbreaks have been confirmed in San Bernardino, Riverside, Los Angeles and Ventura Counties.

 

Since the initial outbreak in mid-May, authorities in California and the USDA-APHIS have had sufficient time to initiate and complete an epidemiologic evaluation to determine the source of infection, the rate of spread and to provide an indication of their intended action to firstly control and secondly eradicate the disease before commercial flocks are affected. The poultry industry in California would benefit from a detailed report in mid-2019 but appropriate epidemiologic information are needed now.

 

It is understood that about 9,000 backyard and exhibition birds have been euthanized and premises have been quarantined.  The incidence rate is increasing, confirming that there is effectively no control.  Without knowing the specific epidemiologic factors associated with the 2018 outbreak, resolution of the problem in the intermediate term is unlikely.

 

As a simple recommendation, owners should be urged to effectively vaccinate their backyard flocks as this will convert a presumably susceptible population to a level of immunity that will inhibit dissemination of virus by whatever means. It is emphasized that vaccination should be implemented by owners and not by state or federal workers since this will result in a repetition of the 1979 END outbreak when flocks broke with Newcastle disease approximately seven days after a mandatory visit to vaccinate birds.

 

The California Department of Food and Agriculture has issued an advisory to flock owners concerning quarantine of new birds for thirty days.  Appropriate action should be to cease acquiring or selling birds under any circumstances with strict quarantine of flocks.  The stated recommendation to “restrict contact with wild birds, rodents or insects which carry disease organisms” appears to be great on paper but impossible to implement given that many of the flocks are on pasture (or in reality, mud). The suggestion to purchase feed from “clean and dependable supplier” is also applicable although Newcastle disease is not generally regarded as being transmitted through feed despite individual cases in the U.K. during the 1980’s with pigeon paramyxovirus.  If feed were involved in transmission of Newcastle disease in the California outbreak, there would probably be more cases over a shorter time period.

 

Again, it is emphasized that epidemiologic investigations are required to determine both source of infection and mode of transmission in the specific Southern California END event. An understanding of the epidemiology is necessary to advise commercial farmers of the appropriate steps to take to prevent introduction over and above enhanced structural and operational biosecurity which in most cases are woefully inadequate.