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Dirofilaria tenuis is a mosquito-transmitted filaria of raccoons in the American Southeast. Here, we report the case of subcutaneous D tenuis in a 72-year-old south Florida resident. A 1-cm nodule on the left forearm progressed to an extensive inflammation and radial neuritis with stiffness and weakness of the thumb, index, and middle fingers. His serum was positive for antifilarial IgG1. The determination was based on the history of exposure in Florida and on the characteristics of the degenerating body wall. Removal led promptly to resolution. Subcutaneous D tenuis is usually benign and may simulate lipomas or neoplasms almost anywhere on the body. It should be considered in middle-aged or older patients of either sex who present with a small nodule enveloping a slender coiled roundworm (females, 260Y360 Km 8Y13 cm). Florida has accounted for approximately 3 quarters of reported cases.

The mosquito-borne filarial worm, Dirofilaria immitis , causes heartworm disease in dogs. Detection of this parasite in its mosquito intermediate host currently involves dissection and microscopic examination for larval stages. Although this method is used commonly as a screening tool for epidemiological surveys, it lacks both sensitivity and specificity. In this study, a more efficient PCR- and probe-based diagnostic assay was developed. The target selected for this assay is a segment of the 16 S rRNA gene. The assay specifically detects as little as 10 pg of D. immitis genomic DNA, equivalent to DNA derived from one third stage larva (L 3 ), but does not detect 100 ng (10 000-fold excess) of the purified DNA from several other filarial nematodes, including Dirofilaria striata , Dirofilaria tenuis , Dipetalonema reconditum , Wuchereria bancroftii , Brugia pahangi , B. malayi , Onchocerca volvulus or Loa loa . This assay also detects one L 3 of D. immitis , the minimal biological unit of infection, in a pool of 200 mosquito heads. This assay can serve as a highly specific and sensitive tool for efficiently screening the large numbers of mosquitoes to determine, with statistical validity the seasonal transmission pattern of D. immitis in a locality prior to designing a rational preventive medication program for that parasite.

A 10-year review of the surgical pathology files of the Department of Pathology at Naples Community Hospital (Naples, FL, U.S.A.) revealed 10 cases of Dirofilaria tenuis and one of Dirofilaria ursi infection. The review consisted of only those lesions for which the pathologists had recorded the presence of a worm in the lesion. Therefore, an unknown number of subcutaneous lesions without parasites were not reviewed. Nine of the 11 cases of Dirofilaria were diagnosed as Dirofilaria or Dirofilaria tenuis originally. An additional case, previously diagnosed as Dirofilaria, was found to be a sparganum larva on review. This finding indicates that, because of the unfamiliarity of pathologists with the diagnostic characteristics of these nematode parasites, infections with Dirofilaria are underdiagnosed or misdiagnosed. If pathologists were more familiar with these parasites, their prevalence and the medical cost of this zoonosis in the southeastern United States could be determined more accurately.

We describe a case of subconjunctival dirofilariasis from South India. The worm was identified by detailed morphologic study. Electronic supplementary material The online version of this article (doi:10.1007/s12348-012-0078-6) contains supplementary material, which is available to authorized users.

A Dirofilaria tenuis subcutaneous nodule was found in the supraorbital area of a 77-year-old woman living in Miami Beach. Removal of this nodule revealed the worm and confirmed the diagnosis. Infection with Dirofilaria tenuis is most common in southern Florida because of the high incidence of these worms in their natural hosts--raccoons and opossums.

A 29-year-old man from east texas presented with a 3-month history of a large, isolated, painful subcutaneous nodule on his lower right leg. An excisional biopsy showed zones of necrosis in the epidermis, dermis, and subcutaneous adipose tissue with a neutrophilic infiltrate. The dermis showed a mixed infiltrate with necrotic debris and a non-gravid adult female filarial nematode with a thick, multi-layered cuticle, paired uteri, and an intestine. The histologic features were diagnostic for dirofilaria tenuis, the raccoon heartworm. Dirofilaria tenuis causes heartworm infection in raccoons and infrequently causes human disease. When humans do contract dirofilariasis, the mode of transmission is via a bite from a mosquito infected with dirofilaria larvae. Humans are a dead end host and dirofilaria cannot reproduce in humans, but they do cause various lesions at the site of the mosquito bites. We report a very rare case of human dirofilaria tenuis infection manifesting as a subcutaneous nodule. Dirofilaria tenuis infections are very rare in the U.S., and usually occur in the Southeastern U.S.

The prevalence of filariae in wild raccoons trapped in southeast Georgia was determined. Examination of blood samples revealed that 74 of 113 raccoons (66%) trapped in 6 southeastern Georgia counties were infected. Seventy-three of these raccoons (65%) were infected with Mansonella llewellyni and this parasite was observed in raccoons from every location examined. Dirofilaria tenuis was found in 22 raccoons (20%) and was observed in only 3 of the 6 counties surveyed. An adult specimen of Acanthocheilonema procyonis was found in the subcutaneous tissues of 1 of 5 necropsied raccoons. This is the first record of filariae in raccoons from Georgia. In addition, Dirofilaria-like larvae were found in Aedes taeniorhyncus mosquitoes collected in Liberty County.

Twenty-three species of helminths (4 trematodes, 2 cestodes, 14 nematodes, and 3 acanthocephalans) were found in the gastrointestinal tract, lungs, pancreas, tongue, urinary bladder, and subcutaneous tissues of 30 live-trapped or hunter-shot raccoons from north-central Arkansas between November 1989 and April 1990. Helminths were not detected in the brain, diaphragm, gallbladder, heart, liver, reproductive system, or trachea. Each raccoon examined was infected with 3 or more of the following helminths: Brachylaima virginiana, Eurytrema procyonis, Fibricola cratera, Pharyngostomoides procyonis, Atriotaenia procyonis, Mesocestoides spp., Arthrocephalus lotoris, Capillaria aerophila, Capillaria plica, Capillaria procyonis, Capillaria putorii, Crenosoma goblei, Cruzia americana, Dirofilaria tenuis, Dracunculus insignis, Enterobius sp., Gnathostoma procyonis, Molineus barbatus, Physaloptera rara, Trichinella spiralis, Centrorhynchus wardae, Macracanthorhynchus ingens, and Oligacanthorhynchus tortuosa. All helminths collected with the exception of D. insignis constitute new geographic distribution records. Occurrences of C. aerophila, C. wardae, and O. tortuosa are new host records. One nymphal pentastome, Porocephalus crotali, was found in the liver of 1 raccoon, constituting a new host record.

A patient who developed a self-limited acute migratory arthritis in association with subcutaneous infection with Dirofilaria tenuis is described. There have been several reports of parasitic rheumatism and the possible association between arthritis and parasitic infection. Parasitic rheumatism in a patient infected with D tenuis has not been previously reported, however.

In this third of a series of studies on experimental dirofilariasis in primate hosts, 3 Macaca cynomolgus, 6 M. speciosa, and 2 M. mulatta were inoculated with infective larvae of Dirofilaria tenuis, a parasite of the raccoon, and were killed at periods ranging from 2 weeks to 13 months of infection. One M. mulatta and one M. speciosa were treated daily with prednisolone beginning 2 months after inoculation; worms were recovered from these and 5 other monkeys (7 of 11). Microfilaremia was detected during the 28th week of infection in a monkey under prednisolone treatment. Microfilaremia was found to be aperiodic in that monkey and in a raccoon. Eosinophilia and antibodies to the microfilaria reached appreciable levels in three monkeys harboring gravid worms. Development of D. tenuis in M. speciosa appeared to be comparable to that observed in man.

Summary Adult and adolescent Dirofilaria tenuis Chandler, 1942, from subcutaneous tissues of raccoons (Procyon lotor) in Florida and Louisiana were described in detail and compared with 26 worms earlier identified as Dirofilaria conjunctivae (Addario, 1885) from subcutaneous tissues of man, mainly in Florida and other Southeastern States. Other subcutaneous Dirofilaria species from North American mammals were similarly studied. It was found that with the exception of D. tenuis, all of the species of Dirofilaria found in animals in southeastern United States can be distinguished from the D. conjunctivae reported from the same area. It is concluded that D. tenuis apparently is the Dirofilaria species most frequently found in the subcutaneous tissues of man in this country, although one other species (unidentified) has been reported and the discovery of still others can be anticipated.

Summary An attempt was made to study periodicity of D. tenuis through mosquito mortality, and determine the effect of the larvae of this filariid on mosquito mortality. Dirofilaria tenuis appears to be nocturnal in periodicity with the microfilariae being at their maximum in the peripheral blood at about midnight. Mosquitoes fed on a lightly infected raccoon reached a peak mortality on the third day. Mosquitoes fed on a heavily infected raccoon suffer greatest mortality on the second day, followed by a high ensuing mortality accented on the eighth and ninth day. As the number of microfilariae ingested by the mosquito increases, it appears that the time it takes the microfilariae to enter the tubules decreases. Generally mosquito mortality increased as the number of microfilariae ingested increased.

A case of Dirofilaria tenuis presenting as a breast nodule is reported in a patient who traveled to the southeast United States 6 months before the nodule was noted. It illustrates an unusual diagnostic problem, especially since it presented in a nonendemic area. The morphological criteria for diagnosis of D. tenuis in tissue sections are noted.

Summary An adult female Dirofilaria tenuis was removed by biopsy from the subcutaneous tissue of the right thigh of a 39-year-old white man of McComb, Mississippi. The diagnosis was made preoperatively on the basis of peripheral-blood eosinophilia, a history of a migrating lesion, and presence of anti-filarial antibodies. The worm was found to contain microfilariae. It is unknown whether the multiple lesions successively noted by the patient represented the effects of a single migrating worm or of two or more. There has been no recurrence since surgical removal of the single worm.

IN New England, physicians usually do not expect to discover that the underlying cause of a subcutaneous lump is a zoonotic filariasis, but their expectations may be enhanced by the following case ...

Dirofilaria cancrivori sp. n. is described from subcutaneous tissues of the crabdog, Procyon cancrivorus, in Guyana, South America. The filarid is morphologically distinct from Dirofilaria tenuis, parasite of a related host, the raccoon, in the southern United States, and all other species of Dirofilaria. The parasite can be distinguished from other dirofilarias based on a combination of morphological features including its size, number, and arrangement of caudal papillae on the male tail, size and shape of the spicules, the presence of longitudinal ridges and transverse striations on the cuticle, and the microfilaria.

A study was undertaken to determine the prevalence of Dirofilaria tenuis in raccoons from subtropical southern Florida as compared to the northern part of the state. The results indicate that D. tenuis is more prevalent in southern Florida and suggest that this might be why humans suffer from more D. tenuis infections in southern Florida than in other parts of the state.

Cuticular markings of five species of Dirofilaria were examined by SEM. Variations in the patterns on the en face view were observed among the species. Transverse striations were ob- served on the cuticles of all five species, but longitudinal ridges were lacking on Dirofilaria immitis, the type species of the subgenus Dirofilaria. They were present on the other four species, Dirofilaria repens, Dirofilaria tenuis, Dirofilaria corynodes, and Dirofilaria magnilarvatum, members of the subgenus Nochtiella. Longitudinal ridges and other cuticular structures and patterns were seen to vary among the species and with the portion and aspect of the worm examined. It is suggested that SEM would be a good tool for a detailed study of specific cuticular morphology of all species of Dirofilaria, thus contributing toward their differentiation and recognition. The difficulties of identifying species of the genus Dirofilaria because of their notoriously variable sizes, proportions, and details of spic- ules and caudal papillae are well known. Chandler (1942) suggested that the cuticular markings of these nematodes may provide re- liable specific characters in this genus. Ander- son (1952) noted differences in the cuticle of

punctipennis and Ae. sticticus appear to be among the most important vectors of dog heartworm in the area. In a previous Macon County study (Tolbert and Johnson, 1982, loc. cit.), mosquitoes were collected at urban as well as rural sites. The study revealed that 138 Ae. sticticus were collected; however, none were found positive for Dirofilaria immitis. Data presented in the presunctipennis and Ae. sticticus appear to b among e most important vectors of dog heartworm in e area. In a previous Macon County st dy (Tolent study reveal that Ae. sticticus may also be a potential vector of Dirofilaria in Macon County, Alabama. Also, new county isolations of Dirofilaria were recorded for Ae. trivittatus, and An. crucians. Additional study is needed to determine if these species are in fact major vectors of Dirofilaria in the area. Pinger (1982, loc. cit.) stated that Ae. trivittatus should be recognized as a potential vector of D. immitis wherever it is locally abundant. It is widely accepted that 6 species of Dirofilaria use mosquitoes as intermediate hosts; however, only 3 species, D. immitis, Dirofilaria striata, and Dirofilaria tenuis, are known to develop in the Malpighian tubles of their vector hosts. Because of morphologic similarities of their larvae in this location, it is difficult to distinguish the species in naturally infested mosquitoes. It is believed that the filaroids presented in this paper are probably D. immitis. This is supported by the high incidence of canine dirofilariasis in Macon County (42.5%), as confirmed by a previous study by Kirk (1977. The incidence of canine filariasis in Macon County, Alabama. M.S. Thesis, Tuskegee University, Tuskegee, Alaama), morphological characteristics of the parasites, and the site of the development of the parasite in the vector. This investigation was supported in part by the National Institutes of Health, MBRS Grant 2-506RR08091-10 and the George Washington Carver Agricultural Experiment Station, Carver Research Foundation of Tuskegee University.

Brugia beaveri sp. n., from the lymph nodes, skin, and carcass of the raccoon (Procyon lotor) in Louisiana is described. This is the first Brugia species to be reported from mammals in North America. It differs from the six other described species of the genus generally in the smaller body size of the female, the size and structure of the spicules, and the larger microfilaria which has a distinctively long cephalic space. A sheathed microfilaria of the Brugia type was first discovered in the United States in 1953 in a thick blood film from a raccoon (Procyon lotor) from Lafitte, Louisiana (Beaver, personal communication). A similar microfilaria was found in the blood of a bobcat (Lynx rufus) in Florida in 1960 (Orihel, personal communication). In neither case was the adult worm recovered. In February 1963, sheathed microfilariae were again found in raccoons in Louisiana. The adult worm was subsequently recovered and is here described as a new species of the genus Brugia Buckley, 1960. It is the first species of this genus to be described from the United States, the second reported from the Western Hemisphere (Orihel, 1963). MATERIALS AND METHODS Seven raccoons were collected from an area near Rosedale, Louisiana, approximately 90 miles northwest of New Orleans. As six of the animals had been captured alive, their blood could be examined repeatedly before they were necropsied. Microfilariae in blood samples were fixed in 2% formalin. A dilute Azur II solution was added to formalin-fixed microfilariae to bring out morphologic details. Microfilariae were also studied in thick and thin blood films. Thick films were air dried, dehemoglobinized in 0.85% saline, fixed in hot (60 C) 70% alcohol, and stained with dilute Delafield's hematoxylin. Thin blood films were Received for publication 8 August 1963. * This study was supported in part by grants 2E-2 and AI-04919-01 from the National Institutes of Health, Public Health Service. fixed in methyl alcohol and stained 1 hr with Giemsa (2% in pH 7.0 buffered water). Adult worms were recovered by soaking the skin, carcass, and lymphatic tissues in warm 0.85% saline solution as described by Dunn (1931). In the examination of one raccoon in which seven worms were recovered the soaking fluid was, in addition, filtered through coarse filter paper; the material on the surface of the filter paper was then washed into a large petri dish and examined with a dissecting microscope. Adult worms were fixed in glacial acetic acid (Berland, 1961), transferred to 70% alcohol containing 5% glycerine, and then gradually brought into pure glycerine, the medium in which they were studied. All drawings were made with the aid of a camera lucida. Brugia beaveri sp. n. Brugia microfilariae were found in five of the seven raccoons examined. Microfilariae of a Dipetalonema sp. were found in six and those of Dirofilaria tenuis in all of the animals. Adult worms of the new Brugia species were recovered from only two. However, one of the seven raccoons was dead when brought into the laboratory and, although it had Brugia microfilariae in the blood, it was not examined for adult worms. From one raccoon a single male was recovered from the saline in which the skin had soaked. From the other, two complete males, a broken male, three complete females, and a broken female were recovered. One male was recovered from an axillary lymph node and another from a popliteal node; all other specimens were found in the saline in which the skin and carcass had been immersed.