Loaina Gen. N. (Filarioidea: Onchocercidae) for the Filariae Parasitic in Rabbits in North America

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Proc. Helminthol. Soc. Wash. 51(1), 1984, pp. 49-53

Loaina gen. n. (Filarioidea: Onchocercidae) for the Filariae Parasitic in Rabbits in North America

MARK L. EBERHARD AND THOMAS C. ORIHEL Department of Parasitology, Delta Regional Primate Research Center, Covington, Louisiana 70433

ABSTRACT: A new genus, Loaina, is erected to accommodate the species of Dirofilaria parasitic in rabbits in North America. The genus is comprised of two species, Loaina scapiceps (Leidy, 1886) comb. n. and Loaina uniformis (Price, 1957) comb, n.; L. uniformis is designated as the type species. The genus Loaina is distinguished morphologically from Dirofilaria and other Dirofilariinae by a combination of characters, including an extremely short tail in both sexes, an undivided esophagus, a post-esophageal vulva, short, simple spicules, a small number of caudal papillae grouped at the posterior extremity of the body in the male, and a sheathed microfilaria. Two other species, D. timidi and D. roemeri are not regarded to be valid species of Dirofilaria. The genus Dirofilaria should be restricted strictly to those species having unsheathed microfilariae. Morphologically, the genus Loaina most closely resembles the genus Loa. The two genera are distinct, however, on the basis of host preference, size and cuticular ornamentation.

A review of the morphological features of the ments of anatomical features are from stained speci- dirofilarias that parasitize Louisiana mammals mens. revealed that there were marked morphological Description differences between those species of Dirofilaria Railliet and Henry, 1910 infecting rabbits in Loaina gen. n. North America, i.e., D. uniformis Price, 1957 Dirofilaria Railliet and Henry, and D. scapiceps (Leidy, 1886), and other mem- 1910, in part bers of the genus. These differences were ob- General served in both the adult worms and in the Onchocercidae (Leiper, 1911); Dirofilariinae microfilariae. The distinctiveness of these mor- Sandground, 1921. Anterior and posterior ends phological features warrants that a new genus, bluntly rounded in both sexes. Male one-half to Loaina, which will accommodate the species D. one-third length of female. Cuticle without boss- scapiceps and D. uniformis, be erected. es, lateral alae sometimes present. Tail of both The report that follows presents a description sexes extremely short, less than twice width of of the new genus, a discussion of its taxonomic body at anus. Male tail not spirally coiled. Esoph- relationships to other genera in the subfamily agus not divided, without long, sacculate, glan- Dirofilariinae Sandground, 1921, as well as re- dular part. Vulva postesophageal. Spicules short, marks on the above-mentioned species. simple. Caudal papillae large, paired, few in Materials and Methods number, grouped at end of body. Microfilaria Nematodes in the authors' collections identified as sheathed, nuclei to tip of tail; circulates in blood. D. uniformis were recovered at necropsy by skinning TYPE SPECIES: Loaina uniformis (Price, 1957) freshly killed rabbits and searching the subcutaneous comb. n. and muscle tissues for worms, or, more commonly, OTHER SPECIES: Loaina scapiceps (Leidy, 1886) worms were recovered after soaking the skin and car- comb. n. cass in physiological saline. Worms identified as D. scapiceps were recovered by blunt dissections of the tarsal bursae of the hind feet. Worms recovered in Diagnosis either manner were examined alive, then fixed in gla- The genus Loaina is separated on morpholog- cial acetic acid or hot (60°C) Bouin's solution, and stored in 70% alcohol to which 5% glycerine (by vol- ical bases from other genera in the subfamily ume) had been added. Worms were studied micro- Dirofilariinae as outlined by Anderson and Bain scopically after being cleared in glycerine. Specimens (1976). The new genus is distinguished from Bos- examined from other collections are listed under each trichodera Sandground, 1938 and Dirofilariae- species. Microfilariae, obtained in cardiac blood, were fixed formia Lubimov, 1935 on the basis of the short in 2% formalin. They were examined as wet prepara- male tail. Loaina lacks the long, sacculate, glan- tions and as hematoxylin-stained smears. Measure- dular esophagus, characteristic of Edesonfilaria

Figures 1-7. Loaina uniformis comb. n. and Loaina scapiceps comb. n. 1. L. uniformis male tail, lateral view. 2. L. uniformis male tail, ventral view. 3. L. uniformis, female tail, lateral view. 4. L. uniformis female, lateral view. 5. L. uniformis microfilaria from 2% formalin concentration stained with hematoxylin. 6. L. scapiceps male tail, ventral view. 7. L. scapiceps male tail, lateral view.

Yeh, 1960 and Macacanema Schad and Ander- tinguish Loaina from Skrjabinodera Gnedina and son, 1963. The short, simple spicules and small Ysevolodov, 1947, Tawila Khalil, 1932, and Di- number of large, pedunculated caudal papillae rofilaria Railliet and Henry, 1910. Also, the grouped near the end of the body serve to dis- sheathed microfilaria with a blunt tail in which

Copyright © 2011, The Helminthological Society of Washington OF WASHINGTON, VOLUME 51, NUMBER 1, JANUARY 1984 51 the nuclei extend to the tip contrasts markedly with those of the genus Dirofilaria in which the microfilariae characteristically are unsheathed and possess thin, attenuated tails devoid of nuclei. The postesophageal position of the vulva separates Loaina from Foleyella Seraut, 1917 and Pelicitus Railliet and Henry, 1910. Loaina can be distinguished from Loa Stiles, 1905 by its smaller size, the absence of cuticular bosses, and spicule morphology. The genus Loaina, on the basis of present knowledge, appears to be restricted to the order Lagomorpha in North America.

Loaina uniformis (Price, 1957) comb. n. Dirofilaria uniformis Price, 1957 (Figs. 1-5, 8, 10)

HOSTS: Sylvilagus floridanus, S. palustris, S. aquaticus. SPECIMENS EXAMINED: USNM Helm. Coll. No. 38160, 73652, numerous specimens in authors' collections from Cameron, Orleans, and St. Tammany Parishes, Louisiana, and Dade Coun- ty, Florida.

Diagnosis Price (1957) provided an accurate and complete description of this species. However, he Figure 8. Formalin fixed, hematoxylin-stained mi- failed to recognize, at the generic level, significant crofilaria of Loaina uniformis comb, n., note sheath (arrows) ( x 425). morphological differences between the genus Di- rofilaria and the specimens he described. Most there is a more complete and accurate descrip- notable among these are the short tail in both tion, including illustrations of L. uniformis. sexes (Figs. 1-4), the small number of large caudal papillae grouped at the end of the body and Loaina scapiceps (Leidy, 1886) comb. n. the short, simple spicules in the male (Figs. 1, Dirofilaria scapiceps (Leidy, 1886) 2), and the sheathed microfilaria. The illustration (Figs. 6-7) of the microfilaria furnished in the original species description is one of an unstained, wet-mount HOSTS: Sylvilagus floridanus, S. palustris, S. preparation. Consequently, the internal mor- aquaticus, Lepus americanus, L. campestris, L. phology and nuclear arrangement were not clear- washingtonii. ly evident. Because of the taxonomic signifi- SPECIMENS EXAMINED: USNM Helm. Coll. Nos. cance, the microfilaria of L. uniformis has been 28647, 32016, 32621, 38066, 45326, 73651, and illustrated by both a line drawing and a photomi- specimens in authors' collections from St. Tam- crograph (Figs. 5, 8). many Parish, Lousiana. Loaina uniformis has been reported from subcutaneous tissues of rabbits in Maryland, South Diagnosis Carolina, Georgia, Florida, and Louisiana. The Leidy (1886) described in very cursory fashion distribution may be more extensive than indi- Filaria scapiceps, noting the features of size, gen- cated by these reports. eral body shape, and nature of the caudal papillae Loaina uniformis is designated as the type in the male. In 1916, Hall provided a more de- species for several reasons, the most important tailed and accurate description of the adult par- being the availability of type specimens. Also, asite, including measurements. However, the il-

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*•> > : Figures 9-10. Cross sections of female Loa loa and Loaina uniformis comb. n. at comparable levels. 9. L. loa, note various levels of uterus in same section and cuticular bosses (xllO). 10. L. uniformis, note ovary and various levels of uterus in same section of worm (xllO). lustration of the male tail is misleading as it bursa of the hind feet, whereas adult L. uniformis depicts the caudal papillae as being small and are found in subcutaneous tissues. slender rather than large and bulbous (Figs. 6- Loaina scapiceps apparently has widespread 7). Neither Leidy (1886) nor Hall (1916) provid- geographical distribution, which includes: New ed a description of the microfilaria. Only Highby Brunswick, Ontario, and British Columbia, Can- (1943), working on the life history of the parasite, ada, and the northwestern, northeastern, eastern has provided a substantial description of the mi- seaboard, and gulf coast regions of the United crofilaria. He noted the size, internal anatomy, States. and the presence of a sheath. We have been able, Specimens deposited as USNM Helm. Coll. in the present study, to examine microfilariae of No. 32016 (three female worms), and identified L. scapiceps. We confirmed what was observed as D. scapiceps, were recognized not to be that by Price (1957), that the microfilariae of L. sca- species. The specimens, although filaria, could piceps and L. uniformis are virtually identical in not be identified to species. Likewise, specimens morphology. The only remarkable diiference is identified as D. scapiceps and deposited as USNM in length; L. scapiceps averages 240 yum in length, Helm. Coll. Nos. 42790 and 75430, are, in fact, whereas L. uniformis has a mean length of 270 specimens of L. uniformis. /nm. Price (1957) noted also the close morpholog- Discussion ical similarity of the adults of L. uniformis and Taxonomically, Loaina appears to be most L. scapiceps; the two are distinguished most eas- closely related to Loa. This is evidenced in sev- ily on body shape. L. scapiceps is coiled helically eral morphological features. The microfilariae, along the entire body length and the ends in both other than differences in size (L. loa 320 /j.m long, sexes are tapered, whereas the body of L. uni- L. uniformis 270 /um long, L. scapiceps 240 /urn formis is not coiled and the ends are not tapered long) are similar in morphological features, in- appreciably. Moreover, L. scapiceps has lateral cluding arrangement of somatic nuclei in the tail. alae, which are lacking in D. uniformis. The dis- The shape and number of caudal papillae and tal end of the right spicule in L. scapiceps is small size of the spicules of the males are features barbed, whereas in L. uniformis the distal end is common to both genera. It was noted in the pres- smooth and pointed. There is also an additional ent study that in female worms of both L. sca- pair of ventral, subterminal papillae near the tip piceps and L. uniformis, one reproductive tube, of the male tail in L. scapiceps. In addition to including uterus, oviduct, and ovary, typically the morphological features mentioned, adult L. occupied the anterior half of the body and the scapiceps are characteristically found in the tarsal second tube occupied the posterior half (Fig. 4).

This was noted by Eberhard and Orihel (1981) in several features, among which the placement to be the case in Loa as well. of the vulva and the number and distribution of In general features, the shapes of the body in caudal papillae are distinct. For these reasons, it L. loa and L. uniformis are very similar. They is not possible at this time to accurately place D. both have bluntly rounded extremities, are more- roemeri in a proper generic group. However, we or-less uniform in diameter throughout the body feel that the genus Dirofilaria should be restricted length, and the tail of the male is not coiled (the to those species that have unsheathed microfi- last feature is also shared by L. scapiceps). The lariae. two are remarkably similar at the microanatom- ical level, particularly in the structure of the body Acknowledgments wall. Both possess a thick cuticle and prominent The authors thank Dr. Ralph Lichtenfels, An- hypodermal tissue underlying the muscle cells. imal Parasitology Institute, for loan of speci- The muscle cells are few per quadrant, broad, mens. Dr. John Crites, Department of Zoology, and have a large cytoplasmic portion (Figs. 9- Ohio State University, kindly supplied addition- 10). The feature of the muscles in L. scapiceps al specimens of L. scapiceps. This study was sup- is similar except the cytoplasmic portion is less ported by grant RR-00164 from the National conspicuous. The character of the muscle cells Institute of Allergy and Infectious Diseases, NIH. further distinguishes Loaina from Dirofilaria, in which the muscle cells typically are many per Literature Cited quadrant, tall, and slender. Anderson, R. C. 1959. The taxonomy of Dipetalo- The two genera differ morphologically in size, nema spirocauda (Leidy, 1858) n. comb. (=Skrja- Loa being considerably larger and by the absence binaria spirocauda) and Dirofilaria roemeri (Lin- stow, 1905) n. comb. (=Dipetalonema roemeri). of cuticular bosses in Loaina. The host prefer- Can. J. Zool. 37:481-493. ences of the two genera also contrast markedly; , and O. Bain. 1976. No. 3 Keys to genera of Loa is a parasite of primates and Loaina par- the order Spirurida. Part 3. Diplotriaenoidea, asitizes lagomorphs. Further, the arthropod vec- Aproctoidea and Filarioidea. In CIH Keys to the Nematode Parasites of Vertebrates. Common- tors of L. scapiceps and L. uniformis have been wealth Agricultural Bureaux, Farnham Royal, En- demonstrated to be various species of mosqui- gland. 58 pp. toes (Highby, 1943; Price et al., 1963), whereas Eberhard, M. L., and T. C. Orihel. 1981. Develop- it is well documented that deerflies are the vec- ment and larval morphology of Loa loa in exper- tors of Loa. imental primate hosts. J. Parasitol. 67:556-564. Gubanov, N. M., and K. P. Fedorov. 1966. Dirofilaria A review of the genus Dirofilaria revealed two timidi n. sp. from Lepus timidus. Trudy Gelmint. additional species which, based on morpholog- Lab. 17:47-48. ical features, do not belong in this genus. Diro- Hall, M. C. 1916. Nematode parasites of mammals filaria timidi has been described from rabbits in ' of the order Rodentia, Lagomorpha, and Ffyra- coidea. Proc. U.S. Nat. Mus. 50:1-258. Russia (Gubanov and Fedorov, 1966), but study Highby, P. R. 1943. Vectors, transmission, devel- of the description of this species clearly indicates opment and incidence of Dirofilaria scapiceps that it is not a Dirofilaria, nor is it related to (Leidy, 1886) (Nematoda) from the snowshoe hare either L. uniformis or L. scapiceps. Its morpho- in Minnesota. J. Parasitol. 29:253-259. logical features suggest it is Brugia-like. Like- Leidy, J. 1886. Notices of nematoid worms. Proc. Acad. Nat. Sci. Phila. 38:308-313. wise, certain biological and morphological fea- Price, D. L. 1957. Dirofilaria uniformis sp. n. (Nem- tures of Dirofilaria roemeri have been noted to atoda: Filarioidea) from Sylvilagus floridanus be unusual, including prominent lateral alae, a mallurus (Thomas) in Maryland. Proc. Helmin- sheathed microfilaria and a tabanid intermediate thol. Soc. Wash. 24:15-19. , H. Sprinz, R. E. Duxbory, and R. W. Smith. host (Schacher, 1973; Spratt and Varughese, 1963. Development of Dirofilaria uniformis Price 1975). Anderson (1959) commented, when he in Anopheles quadrimaculatus Say. J. Parasitol. placed it in the genus Dirofilaria, that D. roemeri 49(5, sec. 2):48. was so distinct that it could be separated readily Schacher, J. F. 1973. Laboratory models in filariasis: a review of filarial life-cycle patterns. S.E. Asian from other species in the genus. The features J. Trop. Med. Publ. Hlth. 4:336-349. noted above, plus the small size of the spicules, Spratt, D. M., and G. Varughese. 1975. A taxonomic are more characteristic of other genera, including revision of filarioid nematodes from Australian the genus Loaina, than of Dirofilaria. However, marsupials. Aust. J. Zool., Suppl. Ser. No. 35:1- it differs from Loaina and other Dirofilariinae 99.