Microfilarial periodicity of Dirofilaria repens in naturally infested dogs

Abstract

In the past years, canine and human cases of infestation by Dirofilaria repens (Spirurida, Onchocercidae) have been increasingly reported in several European countries. Subcutaneous dirofilariosis by D. repens may either be asymptomatic in dogs or may be characterized by subcutaneous nodules and other symptoms. Information on the periodicity of D. repens microfilariae in naturally infested animals is scant, and this might impair the accurate diagnosis of subcutaneous dirofilariosis and appropriate control plans. In the present study, eight dogs infested with D. repens were sampled twice daily at 12-h intervals for ten consecutive days, and the dog with the highest mean value of microfilariaemia was further sampled every 4 h for four consecutive days. The blood was microscopically and molecularly examined for microfilariae, and, additionally, negative samples were also subjected to a real-time PCR to evaluate the level of circulating DNA. The results demonstrated significant variations in circadian rhythms of D. repens larvae, with higher values of microfilariae per milliliter in the evening samples. A significant variation was also found at the individual level for the dogs with the highest values of microfilariaemia. All samples which were negative at the light microscopy and positive at the real-time PCR displayed levels of circulating parasite DNA <1 microfilaria per milliliter. Biological and clinical implications have been here discussed.

The Complex Interplay of Parasites, Their Hosts, and Circadian Clocks

“…Daily oscillations of the number of microfilariae, an early stage in nematode blood parasite development, have been widely reported. For instance, high nightly counts of Dirofilaria repens microfilaria were observed in dogs (Di Cesare et al, 2013). A similar pattern was observed with Wuchereria bancrofti (Hawking, 1967), presumably an adaptation to the night-biting Anopheles and Culex insect vectors (Reece et al, 2017).…”

Vector-borne pathogens in dogs and red foxes from the federal state of Brandenburg, Germany

“…During this time, pathogens are not detectable in the blood. Moreover, there is a periodical rise of the microfilaria density in the peripheral blood in the evenings (Webber and Hawking, 1955) and an 80 -95% reduction during daytime (Di Cesare et al, 2013).…”

Periodicity of Dirofilaria immitis in Longterm Infections

“…This phenomenon is well-documented in related filarioid parasites Wuchereria bancrofti and Brugia malayi, and is noted to coincide with the peak feeding hours of key vector species (Hawking 1967, Abe et al 2003. Microfilarial periodicity has also been reported in Dirofilaria repens naturally infected dogs as well as numerous heartworm infections (Church et al 1976, Rhee et al 1998, Ranjbar-Bahadori et al 2011, Di Cesare et al 2013), but to our knowledge, no longitudinal studies have been conducted in the canine host. In this study, we measured the microfilaremia of four dogs experimentally infected with D. immitis with the aim of characterizing changes in mf periodicity over a two-year period.…”