Subcutaneous dirofilariasis caused by Dirofilaria repens diagnosed by histopathologic and polymerase chain reaction analysis.

A 31-year-old man with a history of intravenous drug abuse presented with an inflamed subcutaneous nodule in his left thigh. The nodule measured up to 1.2 cm in largest diameter. Under the clinical impression of an inflamed epidermal cyst or a subcutaneous abscess, surgical excision was performed. Histopathologic examination of the nodule and subsequent polymerase chain reaction (PCR) analysis revealed the presence of the helminth Dirofilaria (D.) repens, a member of the family Filarioidea. Dirofilariasis is a parasitosis caused by D. repens and D. immitis that most frequently affects canines. It can rarely be found in humans, usually in the form of a subcutaneous nodule. In Europe, most cases of human dirofilariasis have been detected in the Mediterranean countries, Ukraine and Russia, but sporadic cases have also been reported in central and north European countries. Dirofilariasis must be distinguished from other forms of filarial disease such as onchocercosis and Wuchereria bancrofti filariasis. Diagnosing dirofilariasis purely by histopathology has its pitfalls, especially when the morphology of the nematode is altered due to inflammatory response or surgical artifacts. PCR analysis offers an opportunity to confirm dirofilariasis and identify the dirofilarial species as well. Briefly, we conclude that a diagnosis of subcutaneous dirofilariasis should be considered in cases of subcutaneous mass in an endemic area of animal dirofilariasis.

The epidemiological investigation of Trichinella infection in brown rats (Rattus norvegicus) and domestic pigs in Croatia suggests that rats are not a reservoir at the farm level.

Whether the brown rat (Rattus norvegicus) is a reservoir of Trichinella spp. infection or merely an accidental host, which may be vector of Trichinella spp., continues to be debated. We estimated the prevalence of Trichinella sp. infection in brown rat populations and in domestic pigs in 2 villages in Croatia, where Trichinella sp. infection in pigs has been endemic in the past 10 yr. Trichinella spiralis larvae, identified by a multiplex polymerase chain reaction analyses, were the only species detected in both rats and pigs. In 2001 and 2002, 2,287 rats were collected on 60 farms with different levels of sanitation and with, or without, T. spiralis-infected pigs. The prevalence of infection in rats ranged from 0.2 to 10.7%. Infected rats were detected only on farms with T. spiralis-positive pigs and low sanitation or formerly with low sanitation (P = 0.007, Fisher's exact test), yet no infected rat was detected on farms with T. spiralis-negative pigs. The finding that no infected rat was found on farms with T. spiralis-negative pigs suggests that, in the investigated area, the brown rat is not a reservoir but only a victim of improper pig slaughtering.