Thomas C. Orihel

Bio: Thomas C. Orihel is an academic researcher. The author has contributed to research in topics: Dirofilaria immitis & Brugia pahangi. The author has an hindex of 6, co-authored 7 publications receiving 133 citations.

Morphology of the larval stages of Dirofilaria immitis in the dog.

Abstract: filaria conjulnctivae (Addario, 1885). It is assumed that they are zoonotic forms. Little is known of the development of filarial species in the definitive host, the larval and adolescent stages having been described only for Conispiculum flavescens in lizards (Menon, Ramamurti, and Rao, 1944), Litomosoides carinii in cotton rats (Cross and Scott, 1945, 1947; Scott, 1945; Scott and Cross, 1946; Scott et al, 1951) and Dipetalonema blanci in rodents (Chabaud, 1954). Edeson and Buckley (1959) described the rate of growth and the migration of Wuchereria malayi in experimentally-infected cats.

Dirofilaria lutrae sp. n. (Nematoda:Filarioidea) from otters in the southeast United States.

Abstract: Dirofilaria lutrae sp. n. is described from the subcutaneous tissues of the American otter in Louisiana and Florida. The species is characterized by long and slender form, absence of longitudinal cuticular ridges (except on the tail of the male), extremely large left and relatively short right spicules, and an unusually large, unsheathed microfilaria. Morphologically, the species is most similar to Dirofilaria incrassata which parasitizes certain Central and South American sloths. In the course of a survey of filariae of animals in southern Louisiana in 1959 and 1960, a species of Dirofilaria producing a very large, unsheathed microfilaria was found in the subcutaneous tissues of the otter, Lutra canadensis texensis Goldman. Similar surveys were undertaken in south Florida in 1960-61 and the same species of Dirofilaria was recovered from the otter, Lutra canadensis vaga Bangs, in Dade and Collier counties. Preliminary studies indicated that the species was morphologically distinct from others of the genus. Additional specimens from the same host were obtained from Dr. J. F. Schacher who made collections at the Rockefeller Refuge in Louisiana and from Dr. W. H. Leigh whose material was collected in the Everglades region of Florida. Dirofilaria spp. have not previously been reported from the otter in North America. However, two species have been found in the South American otter, Pteronura brasiliensis. Vogelsang (1940) reported D. immitis in the heart and pulmonary vessels of an otter in Venezuela. Freitas and Lent (1949) described a new species, D. spectans, from the heart and pulmonary arteries of otters in Brazil. The species description presented in this report is based on the examination of specimens recovered from an otter captured in Terrebonne Parish, Louisiana. Measurements are in millimeters unless otherwise indicated. Range is followed by average in parentheses. Received for publication 29 May 1964. * Supported by Grant EF-10,217 from NIH, U. S. Public Health Service. t Present address: Delta Regional Primate Research Center, Covington, Louisiana. Dirofilaria lutrae sp. n. (Figs. 1-9) Description Onchocercidae (Leiper, 1911); Dirofilariinae (Sandground, 1921); Dirofilaria Railliet and Henry, 1911. Body long, slender, uniform in diameter except at the tapered extremities. Cuticle finely striated transversely; longitudinal ridges lacking except on ventral surface of male tail. Oral opening small, circular (Fig. 6), surrounded by four pairs of submedian papillae in addition to a pair of amphids. Esophagus distinctly divided into muscular and glandular portions (Figs. 1, 7, 8). Microfilariae circulate in peripheral blood. Male (15 specimens): Body length 49 to 73 (55); width 0.20 to 0.28 (0.23) at nerve ring, 0.20 to 0.31 (0.26) at mid-body, 0.07 to 0.10 (0.09) at level of cloaca. Esophagus length 0.87 to 1.00 (0.92). Nerve ring 0.26 to 0.29 (0.27) from anterior end. Cloaca 72 to 84 t from posterior end of body. Preanal papillae large, elongate, pedunculated, usually six or seven on left side, five to seven on right; posteriormost pair set inward toward midline (Fig. 2). Single pair of papillae immediately behind cloaca in midventral line. Paired postanal papillae on line with preanals, thre or four in number, usually four; first pair large, second, third, and fourth tall, slender, closely grouped (Fig. 2). Phasmids ventrolaterally placed near tip of tail. Spicules unequal and dissimilar; left 0.55 to 0.70 (0.60) long, right 0.15 to 0.20 (0.17); mean left : right spicular ratio, 3.5: 1. Left spicule with slender tubular shaft and lamina composed of two laterally oriented elements, one short, the other very long and filamentous (Fig. 3). Right spicule short, relatively narrow, boat-shaped (Fig. 3). Tail spirally coiled, usually in two turns. Caudal alae broad. Female (15 specimens): Body length 130 to 180 (151), width at nerve ring 0.33 to 0.36 (0.34), at vulva 0.32 to 0.40 (0.37), at mid-body 0.32 to 0.37 (0.36), at anus 0.09 to 0.11 (0.10). Esophagus 1.15 to 1.33 (1.28) long; nerve ring 0.31 to 0.37 (0.36) from anterior end. Vulva posterior to esophageal-intestinal junction, 1.7 to 2.9 (2.1) from anterior end. Vagina vera muscular, bulbous, ovejector-like; remainder of vagina, usually di-

Brugia guyanen-sis sp.n. (Nematoda: Filarioidea) from the coatimundi (Nasua nasua vittata) in British Guiana.

Abstract: A new species of filaria, Brugia guyanensis, is described from the lymphatic system of the coatimundi (Nasua nasua vittata) in the Rupununi District of British Guiana. This finding constitutes a new host, host family, and geographic locality for the genus Brugia. As compared with other Brugia species, B. guyanensis is relatively small, its left spicule long and hooked at the tip. In November 1962, a microfilaria of the Brugia type was found in a coatimundi (Nasua nasua vittata) from the Rupununi District of British Guiana. Subsequently, adult worms belonging to the genus Brugia were recovered from the lymphatic system of a coatimundi from the same area (Orihel, 1963). To date, 19 of these animals, including some very young ones 4 to 6 months old, have been examined for filarial infections, and in 17 of them the Brugia parasite was found; adult worms were recovered from the lymphatic system of nine. Although the genus Brugia is widely distributed in the Eastern Hemisphere, principally in Southeast Asia, and occurs in a wide range of hosts (Buckley, 1960; Laing, Edeson, and Wharton, 1960), it has not previously been reported from the Western Hemisphere, nor has it been reported in mammals of the family Procyonidae. The specific name selected for the new species is derived from the geographical area in which the parasite was first found. Brugia guyanensis sp. n.

Brugia tupaiae spn. n. (Nematoda: Filarioidea) in tree shrews (Tupaia glis) from Malaysia.

Abstract: Brugia tupaiae sp. n. from the lymphatic system of a Malaysian tree shrew (Tupaia glis) is described. This is the third species of Brugia reported from Malayan mammals and the first described from tupaioids. As compared with other species of Brugia, B. tupaiae is small and slender and has small copulatory spicules. The tail of the microfilaria lacks the constriction between the subterminal and terminal nuclei. Tree shrews are found in the forest areas of India, southeast Asia, and the Philippines. Although microfilariae, including sheathed forms, have been observed in these primitive primates, species of Brugia have not been reported (Laing et al., 1960; Dunn and Ramachandran, 1962; Ann. Rept. Inst. Med. Res. Fed. Malaya, 1964; Dunn, 1964). Recently 41 tree shrews collected in Malaya and identified as Tupaia glis were examined for blood parasites. In six of the animals sheathed microfilariae morphologically similar to those of Brugia pahangi and B. malayi were found. At necropsy of one with a moderate microfilaremia, six adult worms (three males, three females) of an undescribed species of Brugia were recovered from the lymphatic and associated tissues. The species description which follows is based on these six specimens.

Development of Brugia tupaiae in the intermediate and definitive hosts.

Abstract: The microfilariae of Brugia tupaiae develop to the third stage in the thoracic muscles of Aedes aegypti (Liverpool strain) in 8.5 to 9 days. Larvae molt twice in the mosquito in the course of their development. The first molt takes place on the 5th day, the second on the 7th or 8th days. Third-stage larvae have average length-width measurements of 1.05 mm by 21 ,u. Tree shrews which received 17 to 75 third-stage (infective) larvae by subcutaneous injection, developed patent infections in 62 to 80 days. The larval stages of Brugia tupaiae are compared with and differentiated from those of other species of Brugia and other filariae. Brugia tupaiae, a parasite of the lymphatic system of tree shrews (Tupaia glis), has been reported from Malaysia, an area in which two related species, B. malayi and B. pahangi, are enzootic. The adults and microfilariae of these three species have been differentiated on morphological grounds (Orihel, 1966), but no information is available regarding the development of B. tupaiae in the intermediate or

Heartworm disease in animals and humans.

Abstract: Heartworm disease due to Dirofilaria immitis continues to cause severe disease and even death in dogs and other animals in many parts of the world, even though safe, highly effective and convenient preventatives have been available for the past two decades. Moreover, the parasite and vector mosquitoes continue to spread into areas where they have not been reported previously. Heartworm societies have been established in the USA and Japan and the First European Dirofilaria Days (FEDD) Conference was held in Zagreb, Croatia, in February of 2007. These organizations promote awareness, encourage research and provide updated guidelines for the diagnosis, treatment and prevention of heartworm disease. The chapter begins with a review of the biology and life cycle of the parasite. It continues with the prevalence and distribution of the disease in domestic and wild animals, with emphasis on more recent data on the spreading of the disease and the use of molecular biology techniques in vector studies. The section on pathogenesis and immunology also includes a discussion of the current knowledge of the potential role of the Wolbachia endosymbiont in inflammatory and immune responses to D. immitis infection, diagnostic use of specific immune responses to the bacteria, immunomodulatory activity and antibiotic treatment of infected animals. Canine, feline and ferret heartworm disease are updated with regard to the clinical presentation, diagnosis, prevention, therapy and management of the disease, with special emphasis on the recently described Heartworm Associated Respiratory Disease (HARD) Syndrome in cats. The section devoted to heartworm infection in humans also includes notes on other epizootic filariae, particularly D. repens in humans in Europe. The chapter concludes with a discussion on emerging strategies in heartworm treatment and control, highlighting the potential role of tetracycline antibiotics in adulticidal therapy.

Heartworm biology, treatment, and control.

Abstract: This article is a review of the systematics, taxonomy, biology, prevention, control, and treatment of the canine heartworm, Dirofilaria immitus. This filarioid parasite remains one of the most important and dangerous diseases of the dog throughout the United States. The geographic range of the parasite is expanding, and in many parts of the country it has emerged as a threat to canine welfare only in the last 50 or so years. The article also discusses the pathophysiological mechanisms behind the disease induced, the means for diagnosing the disease, and the means of assessing the success of therapy. The treatment of potential complications of heartworm infection, such as post-adulticide thromboembolism, eosinophilic granulomatous pneumonitis, and caval syndrome, is also discussed.

Brugian filariasis: epidemiological and experimental studies.

Abstract: Publisher Summary Filarial nematodes are arthropod-borne parasites, which sometimes cause serious disease in man and animals. The most important filarial worms of man are Onchocerca volvulus, the cause of river-blindness and severe skin disease, and Wuchereria bancrofti, the cause of tropical elephantiasis and hydrocoel. Another serious pathogen of man is Brugia malayi (B. malayi), and its distribution is limited to Asia. There are two well-defined strains of B. malayi, which differ in their microfilarial periodicity patterns. The nocturnally subperiodic strain is found in the dense swamp forest where its mosquito vectors prefer to feed at night but also bite during the day. The nocturnally periodic strain of B. malayi is found in the open plains where the vectors feed only at night. The correlation between peak peripheral microfilaraemia and peak biting time suggests that filarial nematodes have adapted their periodicity patterns to vector periodicity patterns for facilitating their transmission by mosquitoes. Nocturnally subperiodic B. malayi is common in wild monkeys, and this led to the assumption that it is zoonotic. Mansonia mosquitoes, the vectors of subperiodic B. malayi, feed on a variety of animal hosts, including man. The chapter presents the vector-parasite and definitive host–parasite relationships.

Checklist of helminth parasites in wild carnivore mammals from Brazil

Abstract: Ninety-five helminth parasite species totaling 480 records (including 60 new host and geographical records) in 21 species of wild carnivore mammals from Brazil were listed. Nineteen undetermined helminth species and 4 undetermined host species were also included. Information about the site of infection of parasites, localities, references and a host-parasite list were included herein.