Dirofilarial human cases in the Old World, attributed to Dirofilaria immitis : a critical analysis

Abstract

On the basis of these analyses we conclude that there is as yet no proof demonstrating with certainty that Old World D. immitis plays a pathogenic role in humans. It remains to be explained why D. immitis causes pulmonary infections in humans in the Americas while, in the Old World, this location appears, instead, to be always associated with D.repens, even though the former species is at times more frequent than the latter both in dogs and in the vectors. To explain this apparently different pathogenic power, two hypotheses are proposed: (i) there are perhaps twin populations with different genotypes on the two sides of the Atlantic, with different infective capacity for man and dog; (ii) the infective capacity to humans of the parasite could be modified, only in the Old World, by some unidentified factor, possibly inherent to the vector, that affects the complex mechanism of the vector-parasite relationship, affecting the survival of the larvae.

Human Ocular Infection with Dirofilaria repens (Railliet and Henry, 1911) in an Area Endemic for Canine Dirofilariasis

“…8 In spite of its reduced pathogenicity for dogs, D. repens is the species most frequently identified in human cases and it has been recently considered as an emerging metazoonosis in southern Europe. [4][5][6] Although the relationship between animal and human cases of dirofilariasis in a given area could be expected, the correlation between infection rate in dogs and in humans has not been clearly documented.…”

“…Since the first reported case of nematode infection in the human eye as Filaria conjunctivae , 14 D. repens has been implicated as the predominant causative agent of ocular dirofilariasis throughout the Old World. 6 Most of the 492 cases reported in Europe have been in Italy (n = 117) and, in particular, from Sicily. 4,11,13 However, these numbers are likely underestimated because of the lack of accurate etiologic diagnoses and because some cases are likely to go unreported in the literature.…”

“…repens was the prevalent species causing human infection. 6 The DNA barcoding of cox 1 and 12S mitochondrial markers has been shown to be useful for taxonomic identification of many filarioid species. 7 This approach, coupled with morphologic identification, enabled us to describe the first case of human intraocular infection with Onchocerca lupi in Turkey.…”

Human dirofilariosis: The report of subcutaneous Dirofilaria repens infection in the Slovak Republic

“…In the literature, there is trend to relate subcutaneous and ocular dirofilariosis to D. repens, while pulmonary disease is usually considered to be caused by D. immitis. However, a critical report by Pampiglione et al (2009) re-evaluated 28 cases of human pulmonary dirofilariosis in Europe attributed to D. immitis and corrected diagnoses that pulmonary dirofilariosis in Europe is associated with D. repens in contrast to pulmonary infection in the Americas caused by D. immitis. They proposed two hypotheses to explain this different pathogenic power of D. immitis: i) there are twin populations with different genotypes on two side of the Atlantic ii) the infective capacity to humans of the parasite could be modified in Europe by some factor (inherent to the vector) affecting the vector-parasite relationship decreasing the survival of the larvae.…”

Pseudo-tumor of the scrotum, a rare clinical presentation of dirofilariasis: a report of two autochtonous cases due to Dirofilaria repens

“…Dirofilaria repens is an endemic nematode in the Old World with a predominant localization along the Mediterranean coast while Dirofilaria tenuis, Dirofilaria ursi, and Dirofilaria lutrae are endemic in the New World and Dirofilaria immitis has been reported on all continents. 1,2 Their natural hosts include dogs, cats and foxes. The mosquito species Aedes, Culex, and Anopheles have been identified as vectors of these nematodes.…”