title: Mosquito-borne heartworm Dirofilaria immitis in dogs from Australia.
abstract: Heartworm (Dirofilaria immitis) in dogs is considered endemic in Australia, but the clinical heartworm disease caused by the heartworm is rare and prevalence is low. The mainstream prevention of the heartworm is based on macrocyclic lactone (ML) administration. The aim of this study was to confirm endemism of the heartworm under current Australian conditions using a cohort of recent microfilaria-positive dogs which were on variable heartworm prevention.
  
  
  
  A hotspot of canine heartworm antigen-positive and microfilaria-positive dogs has been detected recently in Queensland, Australia. Blood samples from 39 dogs from Queensland and two dogs from New South Wales were investigated for canine filarioids. Rapid antigen diagnostic tests capable of detection of D. immitis and real-time PCR for quantification and differentiation between D. immitis from Acanthocheilonema reconditum with quantification of microfilariae in canine blood samples, together with D. immitis specific real-time PCR assay, were applied to microfilaria-positive dogs. The P-glycoprotein genotype was determined to test whether Australian-sourced heartworm shared the same genetic markers as those suspected of ML-resistance in North America.
  
  
  
  Only D. immitis was detected in the samples from Queensland and New South Wales, Australia. Using high resolution melt real-time PCR and D. immitis specific real-time PCR, the calculated microfilaria concentration ranged from 1 to 44,957 microfilariae/ml and from 7 to 60,526 microfilariae/ml, respectively. DNA sequencing of the PCR products confirmed D. immitis. Fifteen of the examined dogs were on putative, rigorous ML prevention. For the remaining dogs, compliance with heartworm prevention was unknown or reported as inconsistent. Wild-type genotype AA-GG of the P-glycoprotein locus of D. immitis sequence has been obtained for three blood samples. Due to the incomplete history, any suggestion of a loss of efficacy of MLs must be treated as 'remotely possible'. In the immediate future, records of preventative administration and annual antigen testing would be required to determine any problems with the efficacy of preventatives.
  
  
  
  The prevalence of canine heartworm in Australia remains poorly understood. It is generally assumed to be low by veterinary practitioners. The localised increase in the study area confirms endemism of canine heartworm and a requirement for ongoing vigilance through annual heartworm testing to better understand the changing distribution of canine heartworm, client compliance, as well as to detect any change in ML-susceptibility.
authors.affiliation: Faculty of Veterinary Science, The University of Sydney, McMaster Building B14, Sydney, 2006, New South Wales, Australia.
authors.forename: Chloe
authors.initials: C
authors.lastname: Nguyen
authors.affiliation: Faculty of Veterinary Science, The University of Sydney, McMaster Building B14, Sydney, 2006, New South Wales, Australia.
authors.forename: Wei Ling
authors.initials: WL
authors.lastname: Koh
authors.affiliation: Faculty of Veterinary Science, The University of Sydney, McMaster Building B14, Sydney, 2006, New South Wales, Australia.
authors.forename: Andrea
authors.initials: A
authors.lastname: Casteriano
authors.affiliation: University Veterinary Teaching Hospital, Sydney (UVTHS), Faculty of Veterinary Science, The University of Sydney, Evelyn Williams Building B10, Sydney, 2006, New South Wales, Australia.
authors.forename: Niek
authors.initials: N
authors.lastname: Beijerink
authors.affiliation: University Veterinary Teaching Hospital, Sydney (UVTHS), Faculty of Veterinary Science, The University of Sydney, Evelyn Williams Building B10, Sydney, 2006, New South Wales, Australia.
authors.forename: Christopher
authors.initials: C
authors.lastname: Godfrey
authors.affiliation: School of Life and Environmental Sciences, Faculty of Veterinary Science, The University of Sydney, McMaster Building B14, Sydney, 2006, New South Wales, Australia.
authors.forename: Graeme
authors.initials: G
authors.lastname: Brown
authors.affiliation: School of Life and Environmental Sciences, Faculty of Veterinary Science, The University of Sydney, McMaster Building B14, Sydney, 2006, New South Wales, Australia.
authors.forename: David
authors.initials: D
authors.lastname: Emery
authors.affiliation: School of Life and Environmental Sciences, Faculty of Veterinary Science, The University of Sydney, McMaster Building B14, Sydney, 2006, New South Wales, Australia. jan.slapeta@sydney.edu.au.
authors.forename: Jan
authors.initials: J
authors.lastname: Šlapeta
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics; D063486:Acanthocheilonema / Q000235:genetics / Q000302:isolation & purification; D000818:Animals; D000947:Antigens, Helminth / Q000097:blood; D001315:Australia / Q000453:epidemiology; D009033:Culicidae / Q000469:parasitology*; D004183:Dirofilaria immitis / Q000235:genetics / Q000302:isolation & purification*; D004184:Dirofilariasis / Q000175:diagnosis / Q000453:epidemiology* / Q000469:parasitology; D004283:Dog Diseases / Q000175:diagnosis / Q000453:epidemiology* / Q000469:parasitology; D004285:Dogs; D019353:Endemic Diseases; D005838:Genotype; D008842:Microfilariae / Q000235:genetics / Q000302:isolation & purification*; D015995:Prevalence; D011793:Queensland / Q000453:epidemiology; D060888:Real-Time Polymerase Chain Reaction
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000947:Antigens, Helminth
keywords: Acanthocheilonema reconditum; Dirofilaria immitis; Drug resistance; High resolution melt qPCR; Knott’s test; PCR