title: Dirofilaria immitis and D. repens show circadian co-periodicity in naturally co-infected dogs.
abstract: Dirofilaria immitis and Dirofilaria repens are mosquito-borne zoonotic filarioids typically infecting dogs, causing a potentially fatal cardiopulmonary disease and dermatological conditions, respectively. The females are larviparous, releasing the larvae (microfilariae) into the bloodstream, which further develop in mosquito vectors. However, microfilaremia greatly fluctuates during a 24-h period. As the sampling time can greatly influence the accuracy of diagnosis, the aim of the present study was to assess the circadian periodicity of D. immitis and D. repens in naturally co-infected dogs in an endemic area of Romania and to investigate possible differences of periodicity between these two species.
  
  
  
  Overall, four dogs harbouring natural co-infection with D. immitis and D. repens were selected and sampled every two hours for two consecutive days: two dogs in July 2014 and two in July 2015. At each sampling time, a 0.7 ml blood sample was taken. Modified Knott's test was performed on 0.5 ml, and the remaining 0.2 ml were used for DNA extraction and molecular amplification, both in single and duplex PCR reactions. Microfilariae of both species were morphologically identified and counted in each collected sample, microfilaremia was calculated, and fluctuation was charted.
  
  
  
  The dynamics of microfilaremia showed similar patterns for both Dirofilaria species. In all four dogs, D. immitis was present at all sampling times, with several peak values of microfilaremia, of which one was common for all dogs (1 am), while minimum counts occurred between 5 and 9 am. Similarly, for D. repens, one of the peak values was recorded in all dogs at 1 am, while minimum counts (including zero) occurred at 9 and 11 am. Single species-specific PCR reactions were positive for both D. immitis and D. repens in all collected samples, while duplex PCR failed to amplify D. repens DNA in many cases.
  
  
  
  Both Dirofilaria immitis and D. repens microfilariae are subperiodic, following a similar variation pattern, with peak values of microfilaremia registered during the night in Romania. Duplex PCR fails to identify the infection with D. repens in co-infected dogs when the ratio of microfilaremia is in favour of D. immitis.
authors.affiliation: Department of Parasitology and Parasitic Diseases, University of Agricultural Sciences and Veterinary Medicine Cluj-Napoca, 335700, Cluj-Napoca, Romania.
authors.forename: Angela Monica
authors.initials: AM
authors.lastname: Ionică
authors.affiliation: Department of Parasitology and Parasitic Diseases, University of Agricultural Sciences and Veterinary Medicine Cluj-Napoca, 335700, Cluj-Napoca, Romania.
authors.forename: Ioana Adriana
authors.initials: IA
authors.lastname: Matei
authors.affiliation: Department of Parasitology and Parasitic Diseases, University of Agricultural Sciences and Veterinary Medicine Cluj-Napoca, 335700, Cluj-Napoca, Romania.
authors.forename: Gianluca
authors.initials: G
authors.lastname: D'Amico
authors.affiliation: Department of Anesthesiology and Surgical Techniques, University of Agricultural Sciences and Veterinary Medicine Cluj-Napoca, 335700, Cluj-Napoca, Romania.
authors.forename: Lucia Victoria
authors.initials: LV
authors.lastname: Bel
authors.affiliation: Department of Parasitology and Parasitic Diseases, University of Agricultural Sciences and Veterinary Medicine Cluj-Napoca, 335700, Cluj-Napoca, Romania. mirabela.dumitrache@usamvcluj.ro.
authors.forename: Mirabela Oana
authors.initials: MO
authors.lastname: Dumitrache
authors.affiliation: Department of Pathology and Parasitology, University of Veterinary and Pharmaceutical Sciences, Brno, Czech Republic.|CEITEC-VFU, University of Veterinary and Pharmaceutical Sciences, Brno, Czech Republic.|Institute of Parasitology, Biology Centre of the Czech Academy of Sciences, České Budĕjovice, Czech Republic.
authors.forename: David
authors.initials: D
authors.lastname: Modrý
authors.affiliation: Department of Parasitology and Parasitic Diseases, University of Agricultural Sciences and Veterinary Medicine Cluj-Napoca, 335700, Cluj-Napoca, Romania.
authors.forename: Andrei Daniel
authors.initials: AD
authors.lastname: Mihalca
mesh_terms: D000818:Animals; D002940:Circadian Rhythm; D060085:Coinfection / Q000469:parasitology / Q000662:veterinary; D004183:Dirofilaria immitis / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*; D060348:Dirofilaria repens / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*; D004184:Dirofilariasis / Q000175:diagnosis / Q000469:parasitology*; D004283:Dog Diseases / Q000453:epidemiology; D004285:Dogs; D018512:Parasitemia / Q000469:parasitology / Q000662:veterinary*; D016133:Polymerase Chain Reaction; D012383:Romania; D013045:Species Specificity
keywords: Co-infection; Dirofilaria immitis; Dirofilaria repens; Microfilariae; Periodicity