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New approaches to detection: Canine surveillance of high risk pathogens

Tim Gottwald: USDA-ARS

<div>The underpinning for control of exotic diseases such as citrus Huanglongbing (HLB) caused by Candidatus <em>Liberibacter asiaticus</em> (CLas) and Plum Pox Virus (PPV) is early detection/response when incidence is low. Unfortunately, these pathogens can remain asymptomatic and subclinical to PCR detection for months yet can act as inoculum sources. Twenty canines were trained for early detection of HLB and two for PPV. Ten canines were each tested against 1000 trees in replicated randomized field trials with varying HLB-incidence, which resulted in 99.16% overall detection accuracy with very few false negatives or positives. Canines also detected infected trees exclusively from 5-gm feeder root samples. In a time-course experiment, canines detected infections within 2-3 weeks of vector transmission, whereas inoculated trees were not PCR-positive for CLas until at least 3-12 mos. post inoculation. In citrus and prunus field trials, canines trot along the rows with an average interrogation time of ~2-10 trees/s; faster than any other detection method. Canines were also effectively utilized for detection of infected trees in residential areas. This confirms that canines are a very early, accurate and sensitive detection methodology. Canines are able to detect the pathogen in trees with subclinical infection, i.e., before symptom expression and considerably prior to the ability of PCR detection.</div>

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