Prevalence, Lesions, and Differential Diagnosis of Ollulanus tricuspis Infection in Cats

Vet. Pathol. 20: 71-79(1983) Prevalence, Lesions, and Differential Diagnosis of Ollulanus tricuspis Infection in Cats A.M. HARGIS. D.J. PRIEUR, and J.L. BLANCHARD Department of Veterinary Microbiology and Pathology, and Washington Animal Disease Diagnostic Laboratory. Washington State University, Pullman, Wash. Abstract. Ollulanus tricuspis were found in the stomachs of 26 of 20I cats which were mainly from Washington and Idaho. Twenty-fourof the cats were from research or commercial breeding colonies (catteries) and two were pets. Twenty-seven percent of colony cats were infected with O. tricuspis, whereas only 2% of the pet cats were infected. No consistent clinical signs were seen. Histologically there was a significant increase in fibrous connective tissue in the lamina propria and in the number of lymphoid follicles and globule leukocytes in the gastric mucosa ofinfected cats. Histologic examination revealed no parasites in 13 of the 26 infected cats. The 26 infected cats were identified by examination of stomach washings. An additional 21 cats had larvae of other nematodes in their stomachs. These nematode larvae need to be differentiated from O. tricuspis. O/lulanus tricuspis, a gastric nematode in cats, has worldwide distribution; however, it only recently has been reported in cats in the United States [8].Areas in the United States with confirmed cases of O. tricuspis infection include the Pacific Northwest [8], Wisconsin, and Illinois [5]. O. tricuspis frequently is overlooked due to its minute size, I mm or less in length, and its unusual life cycle in which neither adult nor larval parasites usually are passed in feces [I, 9]. In some parts of the world, the nematode has been found more commonly in feral cats rather than pet cats [9, II]. The nematode also has been found in colony cats [8]. O. tricuspis infection has been associated with anorexia, vomiting, and chronic gastritis [5-7]. The purposes ofthis study were to determine the prevalence ofo. tricuspis infection in colony versus pet cats in the Pacific Northwest, to determine if consistent clinical signs or lesions were associated with infection, and to compare the reliability of histologic examination of the stomach with the examination of stomach washings for definitive postmortem diagnosis of O. tricuspis infection. An attempt also was made to determine how frequently other minute parasites that could be confused with O. tricuspis were found in the stomachs of cats. 71

72 Hargis, Prieur, and Blanchard Table I. Background of cats WADDL 166 3.4 Research project ~ 1.8 Total 201 Ollulanus tricuspis in- 26 2.2 fected Background Number of Average age cats (years) -------------- Colony Pet Unknown Washington Animal Disease Diagnostic Laboratory 60 28 88 24 97 9 -.1.2 99 14 2 0 Materials and Methods Two hundred one cats were included in this study (table I). Thirty-five of these cats were necropsied as part of a research project. The remaining 166 cats were submitted to the Washington Animal Disease Diagnostic Laboratory between July, 1980 and July, 1981 for necropsy. During this time, 57 additional cats were submitted to the Washington Animal Disease Diagnostic Laboratory for necropsy; however, those cats were excluded from this study because the stomachs were not collected. Of the 201 cats, 88 came from 18 different research or breeding colonies. The other 113 were comprised of 99 pet cats and 14 cats for which cohort information was unknown. The 201 cats were necropsied and stomachs were collected in 10% neutral buffered formalin. Three sections of stomach from each cat were processed in an automatic tissue processor, embedded in paraffin, sectioned at 6 p.m, and stained with hematoxylin and eosin (HE). The three sections of each cat stomach were approximately the same size, and they were taken from the cardia, body, and pyloric areas of the stomach. The sections were examined microscopically for lesions including the quantity of fibrous connective tissue in the lamina propria, and the number of mucosal lymphoid follicles and globule leukocytes. The amount of fibrous connective tissue and the number of lymphoid follicles were quantified on a scale of one to five. The number of globule leukocytes varied too much to be quantified on a scale of one to five; therefore, globule leukocytes were quantified by averaging the number of globule leukocytes per five high power (40X) fields of superficial gastric mucosa. Stomach washings were done for each cat by manually agitating the jar containing the stomach and 10% neutral buffered formalin and then pouring the contents through a kitchen strainer with l-mm apertures. The filtrate then was poured through a vacuum ftltering apparatus fitted with a brass grid with O.064-mm apertures. The material retained by the filter was rinsed into a petri dish and examined with a dissecting microscope in an effort to find and identify the stomach parasite O. tricuspis. Individual parasites were pipetted onto a glass slide and examined. Baermann sedimentation was done on the stomach contents and feces of eight of the 201 cats to evaluate this procedure in the diagnosis of O. tricuspis infection. These eight cats were euthanatized control cats from one colony. Because they were the largest group of potentially positive colony cats necropsied in one day, they were selected for Baermann sedimentation. For scanning electron microscopy, portions of gastric mucosa that previously had been fixed in 10% neutral buffered formalin were rinsed with phosphate buffer and post fixed in 2% osmium. The specimens were dehydrated in ethanol, dried in carbon dioxide, and examined with a scanning electron microscope. Data on the quantity of fibrous tissue in the lamina propria and the number of mucosal lymphoid follicles were analyzed using the chi-square method of analysis. Globule leukocyte

Ollulanus in Cat Stomachs 73 ~ata were analyzed by setting confidence intervals on the mean numbers of globule leukocytes In the gastric mucosa of cats with and without O. tricuspis. Results O. tricuspis were found in 26 of the 201 cats by the examination of the stomach washings. Detailed descriptions ofthe morphology ofo. tricuspis have been published [2, 8]. Briefly, the adult or larval O. tricuspisfree in cats' stomachs are I mm or less in length. Adult females and larvae have three major and occasionally additional minor tail cusps (fig. I). Adult males have a bursa and no tail cusps (fig. I). Fourth stage male larvae have a bursa and may also have a tricuspid tail [I]. Baermann sedimentation of the stomach contents and feces from eight cats was negative for parasites even though five ofthe eight cats were positive for O. tricuspis by examination of stomach washings. Of the 26 cats that had gastric infection, 24 of 88 (27%) were colony cats and two of 99 (2%) were pets. The fourteen cats for which cohort information was unknown were not infected. The 24 colony cats originated from nine different colonies in Washington, Idaho, and Missouri. One of the household pets was from Washington and one was from Idaho. Three of the colonies had permanently donated one or more cats to a fourth colony (table II). The fifth and sixth colonies had cats that occasionally were housed in the same room, but the cats never had direct contact with each other. The fifth colony also supplied breeding stock to the seventh colony. There was no known contact of cats in the eighth and ninth colonies with each other or with cats in the other seven infected colonies. There was no known contact between the two pet cats. The average age of cats infected with O. tricuspis was 2.2 years, whereas the average age of the survey population of 201 cats was 3.2 years. Nine infected cats were male, 16 were female, and the sex of one was not recorded. Clinical signs varied greatly in cats that had O. tricuspis (table III). Eleven cats were euthanatized research control cats and in colony conditions no clinical signs were noted. Eight additional cats were culled from commercial breeding colonies because the cats were feline leukemia virus positive. These cats had a variety of clinical signs including weight loss, depression, and anemia. Postmortem findings also varied greatly in cats with O. tricuspis (table III). Only one of the 26 infected cats had grossly visible, severe gastric lesions. This cat had chronic fibrosing gastritis which was judged to be associated with O. tricuspis [7]. This cat also had a high duodenal obstruction, but no clinical signs, including vomiting, were noted by the colony owner. Histologically, O. tricuspis parasites were found in only 13 of the 26 infected cats. All cats found to be infected with O. tricuspis histologically also were found to be positive by examination of stomach washings. In cross section, O. tricuspis had numerous cuticular projections representing longitudinal ridges (fig. 2, 3). These projections help to differentiate O. tricuspis adults from larvae of other nematodes that may be found in cat stomachs. O. tricuspis were present under a layer of mucus

74 Hargis, Prieur, and Blanchard 1 2 3 4 Fig. 1: Adult male and female O. tricuspis; tricuspid tail (arrow) on female and bursa on male. Fig. 2: Cross section of O. tricuspis with numerous cuticular projections (arrow). HE. Fig.3: Scanning electron micrograph of O. tricuspis male in gastric mucosa; cuticular ridges and embedded head. Fig. 4: Scanning electron micrograph of O. tricuspis parasites in gastric mucosa. Some parasites partially embedded (large arrows); others coiled on surface under mucus (small arrows).

Ollulanus in Cat Stomachs 75 Table II. Association between 9 colonies with 24 cats infected with O. tricuspis. Numbers of cats within colonies are infected with O. tricuspis COLONY I COLONY 2 COLONY 3 COLONY 5 COLONY 6 4 cats I cat I cat 3 cats 8 cats 1 COLONY 4 COLONY 7 3 cats 2 cats COLONY 8 COLONY 9 I cat I cat or were partially embedded head-first in gastric glands. The orientation of the parasites in the stomach was visualized best by scanning electron microscopy (fig. 3, 4). There were three major histologic changes in the stomachs of the 26 infected cats. There was a significant increase in mucosal fibrous tissue (p ~.05) and a significant increase in the number of mucosal lymphoid aggregates (p ~.005). In many of the infected cats, the lymphoid aggregates had large germinal centers (fig. 5). The third major microscopic change was a significant increase in globule leukocytes in the gastric mucosa (p <.05) (fig. 6). In some cats, there were over 100globule leukocytes per high power (40X) field. In addition to adult and larval O. tricuspis, there were minute larvae of other nematodes found in the stomachs of 21 cats. None of the 21 cats had concurrent infection with O. tricuspis. A few ofthe other larvae were seen in histologic sections, but most were seen in stomach washings. Histologically, cross sections of these other larvae did not have the numerous cuticular projections found on O. tricuspis adults but had instead two lateral alae. In stomach washings, these other larvae did not have a tricuspid tailor a bursa; however, several had a thin tail appendix. These other larvae probably were ascarid and Aelurostrongylus abstrusus larvae. Discussion There have been few reports of O. tricuspis infection in cats in the United States [5, 8, 10]. The infrequency of reports probably is due to the minute size of the parasite, approximately I mm in length, and the unusual life cycle. The parasites live in the stomach of cats and are expelled in vomitus. If the vomitus is eaten by another cat, the infection is transmitted. Most reports indicate that O. tricuspis is not passed in feces [I, 9]. Routine parasitologic procedures and routine necropsy examination, therefore, usually fail to detect the parasite. Another reason infection by O. tricuspis often is undiagnosed may be due to the unreliability of histologic examination. In this study, 13 of 26 cats with O. tricuspis infection did not have parasites in three histologic sections. The infected cats in which no parasites were seen in sections had

76 Hargis, Prieur, and Blanchard Table III. Clinical signs and lesions in cats infected with O. tricuspis Cat Colony Clinical sign(s) Postmortem fmding(s) number" I 5 none euthanatized control 2 5 weight loss, small size CHS, peritonitis 3 6 none euthanatized control 4 7 none euthanatized control 5 7 ocular discharge conjunctivitis, euthanatized control 6 6 none euthanatized control 7 6 none euthanatized control 8 5 straining feline urologic syndrome 9 6 none euthanatized control 10 6 none euthanatized control II 6 none euthanatized control 12 6 none euthanatized control 13 6 none euthanatized control 14 I FeLV + cull pulmonary hemorrhages, edema 15 I FeLV + cull bone-marrow dysplasia 16 I FeLV + cull lymphosarcoma 17 2 FeLV + cull central nervous system reticulosis 18 I FeLV + cull necrotizing rhinitis 19 4 ascites, anorexia, lethargy feline infectious peritonitis 20 8 none chronic gastritis, duodenal obstruction 21 Pet chronic weight loss lymphosarcoma 22 Pet glossitis glossitis 23 4 FeLV + cull feline infectious peritonitis 24 3 FeLV + cull aortic dilation 25 4 FeLV + cull septicemia 26 9 uterine hemorrhage, abortion hemorrhage See Table II. CHS = Chediak-Higashi syndrome; FeLV = Feline leukemia virus. increased mucosal fibrous connective tissue, mucosal lymphoid follicles, and/or mucosal globule leukocytes. These changes in the gastric mucosa of cats, even if no O. tricuspis are seen histologically, should be considered suggestive of O. tricuspis infection. The cats most likely to be infected are feral cats and colony-raised cats [8, 9, IIJ. Feral cats may have a poor diet and more often may eat vomited material from other cats. Also, since domestic dogs, foxes, wild cats, and pigs also have had O. tricuspis infection [4J, these animals, or possibly other unidentified hosts, may harbor and may be involved in the transmission of the parasite to cats. The high prevalence of infection in colony cats most likely is due to the concentration of numerous cats in a small area. The potential for one cat to infect many other cats is high. Pet cats have infrequent contact with many other cats and are, therefore, less likely to contract and transmit O. tricuspis infection. No vomiting was observed in cats living in colony conditions, possibly because the

Ollulanus in Cat Stomachs 77 Fig. 5: Histologic section of stomach of cat infected with O. tricuspis. Large lymphoid follicles with germinal centers. HE. Fig. 6: Histologic section of stomach of cal infected with O. tricuspis; many globule leukocytes (arrows). HE.

78 Hargis, Prieur, and Blanchard cats were observed only periodically during the day and because penmates may have eaten vomited material before it was seen by caretakers. No chronic vomiting was recorded on the histories of the two infected pet cats in this study. Cats with O. tricuspis generally have been reported to have a history of chronic vomiting [3, 5, 12]. There have been few reports on postmortem findings in cats with O. tricuspis. Mild catarrhal gastritis and, rarely, severe fibrosing gastritis have been reported [3, 5, 6]. One of the 26 infected cats had a severe gastritis associated with O. tricuspis. A few cats had no O. tricuspis infection detected by histologic examination and examination of stomach washings, but they had increased fibrous tissue, lymphoid follicles, and globule leukocytes. These cats may have been infected with O. tricuspis at the time of necropsy, but infection may not have been detected; or possibly, they may have been infected previously, but the infection had resolved. No other gastric parasites were seen in these cats. The other larvae found in 21 cats were not associated with significant gastric lesions. This probably is because these other parasites were in the gastric lumen and not under the mucus layer or embedded in gastric glands. Acknowledgements Supported in part by Grants RROO515, RR05465, and K04RROOOO3 from the U.S. Public Health Service, National Institutes of Health. Dr. Blanchard is a postdoctoral fellow at the University of Idaho, Moscow, Idaho 83843. The authors thank Drs. Richard Ott, Gerald Hegreberg, and Linda Collier, and Mrs. Lee Andra Froseth for their generous contribution of cats for this study, and thank Dr. Anthony Gallina for providingaccess to the tissues ofcats submitted to the Washington Animal Disease Diagnostic Laboratory. References CAMERON, T.W.M.: Observations on the life history of Ol/ulanus tricuspis Leuck., the stomach worm of the cat. J HelminthoI5:67-80, 1927 2 CAMERON, T.W.M.: The lung worm and the stomach worm in the cat. Vet J 85:97-112, 1929 3 CAMERON, T.W.M.: On the pathogenicity of the stomach and lung worms of the cat. J Helmintholl0:231-234, 1932 4 DUNN, A.M.: Veterinary Helminthology, p. 34. Heinemann Medical Books, Ltd., London, 1978 5 GREVE, J.H.: A nematode causing vomiting in cats. Fel Pract 11:17-19, 1981 6 HANICHEN, T.; HASSLINGER, M.A.: Chronische gastritis durch Ol/ulanus tricuspis (Leuckart 1865) bei einer Katze. Berl Muench Tieraerztl Wochenschr 90:59-62, 1977 7 HARGIS, A.M.; PRIEUR, D.J.; BLANCHARD, J.L.; TRIGO, F.J.: Chronic fibrosing gastritis associated with Ol/ulanus tricuspis in a cat. Vet Patholl9:32Q-323, 1982 8 HARGIS, A.M.; PRIEUR, D.J.; WESCOTT, R.B.: A gastric nematode (Ol/ulanus tricuspis) in cats in the Pacific Northwest. J Am Vet Med Assoc 178:475-478, 1981 9 HASSLINGER, M.A.: Zum vorkommen von Ol/ulanus tricuspis (Leukart, 1865) bei hauskatzen. Berl Muench Tieraerztl Wochenschr92:316-318, 1979

Ollulanus in Cat Stomachs 79 10 LILLIS, W.O.: Helminth survey of dogs and cats in New Jersey. J Parasitol53: 1082-1084, 1967 II PAVLOV. P.M.; HOWELL, M.J.: Helminth parasites of Canberra cats. Aust Vet J 53:599 600, 1977 12 SCHUTZE, H.R.; KRAFT, W.: Endo-und ektoparasiten von Hund und Katze, diagnose und therapie. Praktische Tierarzt 60: 56-64, 1979 Request reprints from Dr. Ann M. Hargis. Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, WA 99164 (USA).