Morphological redescription of Dirofilaria immitis.

Morphological descriptions of Dirofilaria immitis are scarce. For this reason, we carried out morphological studies using both light and scanning electron microscopy for this filaroid species. Morphometric and morphological data were compatible with previous descriptions of D. immitis , but several anatomical structures are described by scanning electron microscopy for the first time, such as details of the cuticular striations, positioning of amphids, visualization of anal and vulvar opening, descriptions of deirids, lateral line, the pair of phasmids in the posterior end in females, and visualization of a small pair of latero-terminal papillae in the posterior end in males.

Kidney ultrastructural lesions in dogs experimentally infected with Dirofilaria immitis (Leidy, 1856).

Kidneys of 16 beagles with experimentally induced heartworm (Dirofilaria immitis) infections and 4 heartworm-nai;ve dogs were studied by light and electron microscopy. The infections were induced either by subcutaneous injection of infective larvae or by the transplantation of adult parasites, and infection periods varied from 111 to 818 days and 365 to 923 days, respectively. One control group of heartworm-naïve dogs and four groups of heartworm-infected dogs, which were divided according to the type and the length of infection, were used. In the infected dogs, thickening of the glomerular basement membrane (GBM), the presence of dense deposits in the GBM, and foot process effacement were the most frequent lesions observed. In some dogs, electron dense deposits were seen in the GBM and the mesangium and/or enlargement of the mesangial matrix could be characterized. The longer the infection period, the thicker the GBM and the more common the occurrence of foot process effacement. In general, these alterations were more evident in animals that had been infected for more than 1 year, had high microfilaremia, and had 14 or more parasites in the main pulmonary artery and its branches. The presence of dense deposits suggests that the pathogenesis of kidney disease in dirofilariasis is associated with deposits of immune complexes in the membrane. The finding of ultrastructural changes in dogs with early prepatent infections suggests that immature heartworms, as well as microfilariae and possibly adult worms, contribute to the glomerulonephropathy.

On the rugose area and caudal papillae distribution in Dirofilaria immitis (Leidy, 1856) Railliet & Henry, 1911, by scanning electron microscopy.

The objective of this study was to obtain a better characterization of Dirofilaria immitis (Leidy, 1856) Railliet & Henry, 1911, in Brazil, ratifying previous accounts and adding new data on the rugose area on the ventral surface of the spiralled posterior portion of males observed by scanning electron microscopy, which presents a different arrangement compared to other species of the genus, and differs also from the genera Litomosoides Chandler, 1931, and Wuchereria Silva Araújo, 1877, adding another taxonomic character to Dirofilariinae and Onchocercinae. Scanning electron microscopy studies also showed some aspects of the distribution of caudal papillae in D. immitis that have not been described before.