Location: Subtropical Plant Pathology ResearchTitle: Canine assisted early detection of HLB
|BARTELS, DAVID - Animal And Plant Health Inspection Service (APHIS)|
|LUO, WEIQI - North Carolina State University|
|LOUWES, FRANK - North Carolina State University|
|VIDALAKIS, GEORGIOS - University Of California|
|MAUK, PEGGY - University Of California|
Submitted to: Journal of Citrus Pathology
Publication Type: Abstract Only
Publication Acceptance Date: 12/23/2016
Publication Date: 5/18/2017
Citation: Gottwald, T.R., Poole, G.H., Taylor, E.L., Hall, D.G., Hartung, J.S., Bartels, D., McCollum, T.G., Hilf, M.E., Luo, W., Louwes, F., Polek, M., Vidalakis, G., Mauk, P. 2017. Canine assisted early detection of HLB. Journal of Citrus Pathology. 4(1):16/45.
Interpretive Summary: Dogs have been trained to detect HLB-infected trees and will be used as an early detection method for commercial and residential survey in all citrus producing states. When linked with a rapid response, canine detection will be a powerful tool which will help minimize disease spread and optimize planting longevity.
Technical Abstract: The underpinning for HLB control is early detection and early response, especially in Texas and California where incidence is low and Arizona where the disease has not been detected. Eventually Florida, which has been devastated by the disease, will likely replant large areas to reestablish the citrus industry. In all of these situations, the optimal control strategy is to inhibit HLB from entering and establishing in commercial plantings. Infected tree removal, to reduce inoculum in the early stage of the epidemic, remains the most effective deterrent to epidemic development. The earlier the detection of Candidatus Liberibacter asiaticus (CLas) infections, especially when asymptomatic or better yet subclinical, the more efficacious infected-tree removal can be. A number of early detection technologies are being explored among which canine detection of CLas infected trees, shows considerable promise. 20 dogs were trained for early detection via a USDA, APHIS HLB Mac grant. Using 10 dogs, each tested against 1000 trees in replicated randomized “field trials” in a gridded array with varying HLB-incidence, resulted in 99.17% overall detection accuracy. All dogs performed very well with statistically insignificant trends toward false negative or false positives. Each dog has its own personality and interacts slightly differently depending upon the trainer-handler. However, there was no statistical difference in CLas detection by trainer-dog combination. We also explored the use of multiple dogs for confirmation of CLas infections. When two or more dogs alert on the same tree, the tree statistically has a 100% probability of infection. Dogs were also capable of accurately detecting CLas-infected trees exclusively from 5-gm feeder root samples. Using 10 dogs in a time course experiment with ACP vectored trees, dogs began to detect CLas infections within 2-3 weeks of inoculation, whereas, inoculated trees were not PCR-positive for CLas until at least 3-month post inoculation, with the majority of trees taking 6 months or longer before becoming PCR-positive. This confirms that dogs are indeed a very early detection methodology; able to detect CLas in trees with subclinical infection, i.e., before symptom expression and considerably prior to the ability of PCR for detection/confirmation. In field trials of young and mature citrus plantations, canines trot along the rows with an average interrogation time of ~2 to 10 tree/sec, most rapid of all detection methodologies and greatly assists in narrowing the number of trees needed to be screened for CLas. Dogs were also effectively utilized for detection of CLas infected trees in residential areas. The dogs have alerted to multiple trees in four counties in California and were recently contracted by University of California Riverside (UCR) to examine plantings on UCR Citrus Research Center. Dogs are rewarded for detections by verbal praise and short duration play with handlers. Canines were tested for cross reaction with other citrus pathogens from the USDA International Pathogen Collection in Beltsville, MD and in the field at UCR and did not alert to other known viruses, viroids, Spiroplasma citri or Liberibacter solanacearum. Various deployment strategies and efficiencies will be discussed based on the known spatiotemporal distribution of CLas infected trees.