First Clinical Cases of Spirometrosis in Two Cats in Korea.

This study reports the first two clinical cases of spirometrosis caused by Spirometra sp. in cats in Korea. In these two cases, the cats vomited, and long proglottids of tapeworm were recovered. The sick cats presented with anorexia and lethargy. However, they unexpectedly showed no diarrhea, which is the main symptom of spirometrosis. Based on a fecal floatation test as well as morphological and molecular analyses, the parasite was diagnosed as Spirometra sp. The 2 cases were treated with praziquantel. This study suggests regular monitoring of health and deworming in companion animals, even when animals are well cared for, with regular preventive medication. Additionally, spirometrosis should be considered in the differential diagnosis in cases of gastrointestinal symptoms in Spirometra endemic areas.

INTRODUCTION

Spirometra (Cestoda: Diphyllobothridae) is a small-to-medium-sized tapeworm that is found globally [1]. Unlike other cestodes that infect cats, Spirometra has a distinctive life cycle requiring two intermediate hosts [1,2]. Crustaceans, such as cyclops, act as the first intermediate host. The second intermediate hosts, including amphibians and reptiles, play a role in hosting the plerocercoid form. In definitive hosts, Spirometra becomes an adult worm and resides in the small intestine of carnivores and in domestic cats and dogs.

The plerocercoid larvae of Spirometra have a zoonotic characteristic. The plerocercoid larvae, which are called spargana, can invade various human tissues, such as the brain, eyes, breast, spinal cord, and subcutaneous tissue [3]. Sparganosis, caused by infection of spargana, occurs due to the ingestion of contaminated water or undercooked meat; on the other hand, infection by adult Spirometra is called spirometrosis [1,4]. In Korea, more than 200 human cases of sparganosis have been reported due to infection by the plerocercoid of S. decipiens and S. erinaceieuropaei [4-6]. Animals can also be infected by spargana, and their symptoms are similar to those of humans [7-10].

There has been a debate on the species classification of Spirometra spp. [3,11-13]. Traditionally, species classification is achieved by evaluating the shape and number of uterine coils of adult worms. However, some studies have suggested that this method is insufficient to clearly differentiate various species [11,12]. Additionally, without significant consideration of morphological or molecular analysis, many Spirometra species have been recorded as S. erinaceieuropaei, which makes it difficult to determine the regional distribution of Spirometra spp. [8,9,13,15,16]. Owing to advances in molecular techniques, recent studies have attempted to identify Spirometra spp. based on the mitochondrial genome, especially based on the cytochrome c oxidase subunit 1 (cox1) gene [1-4,12,14]. However, morphological features that correspond to molecular data are required from the population of worms worldwide. Because the taxonomical debate on Spirometra spp. is far from the objective of this study, we described the Spirometra obtained in this study as Spirometra sp., and the species names originating from other studies are described as in their original study.

Although there are different studies on Spirometra in humans in Korea, studies in animals are insufficient. Most previous studies on cats in Korea have focused on identifying Spirometra at the genus level using coproscopic examination [15-17]. To the best of our knowledge, there are no reports on clinical cases on spirometrosis or sparganosis occurring in cats in Korea [15-18]. Therefore, this study reports the first clinical cases of spirometrosis in cats in Korea and the treatment regimen implemented.

CASE DESCRIPTION

Case 1

A 3-year-old, 4.5 kg spayed female cat (domestic shorthair), living in Yangsan, Korea, had been vomiting irregularly for several days with anorexia and lethargy, without showing any signs of diarrhea. The cat was a stray cat, and after being adopted by the current owner, the cat was reared indoors for more than half a year. Additionally, the cat was regularly treated with preventive medicine (Advocate for cat; Bayer, Seoul, Korea) to prevent endo- and ecto-parasites. Initially, the sick cat was diagnosed with inflammatory bowel disease based on the history, clinical symptoms, and ultrasonography (data not shown). For the treatment, peroral prednisolone (Solondo Tab. 5 mg; Yuhan, Seoul, Korea) (1 mg/kg) was prescribed twice a day for three months. Although the symptoms improved with treatment, the cat did not appear to be completely cured. One day after the treatment, the cat vomited, and two long proglottids of tapeworms, approximately 30 cm each, were recovered without a scolex (Fig. 1A).

Fig. 1

Macroscopical and microscopical characteristics of Spirometra sp. recovered from cats in Korea. (A) Adult Spirometra recovered from vomiting. (B) Eggs of Spirometra. (C) Whole mounted specimens of proglottids (acetocarmine stained). TV, testes and vitelline follicles; Ci, cirrus; Ut, uterus; GP, genital pore; Ov, ovary.

For the diagnosis, fecal floatation tests were performed using a saturated sodium nitrate solution (specific gravity 1.33). Based on the fecal examination and gross morphological characteristics of the worms, the parasite was identified as Spirometra sp. (Fig. 1A–C). In the fecal floatation test, no other parasite eggs were identified. For exact species identification, based on morphological and molecular methods, the recovered proglottids of worms were kept in 70% ethyl alcohol and were submitted to the College of Veterinary Medicine, Chungbuk National University, Cheongju, Korea.

Broadline spot-on solution (Boehringer Ingelheim; Seoul, Korea) containing praziquantel was applied twice a month according to the manufacturer’s instructions. One month after the last application, a fecal examination was performed; however, Spirometra eggs were still observed. Before additional treatment, complete blood count was evaluated using Exigo eos (Boule Diagnostics AB, Spånga, Sweden), and certain hematological values, including mean corpuscular volume, mean corpuscular hemoglobin, and platelets, showed abnormalities (Supplementary Table S1). Thereafter, praziquantel (Distocide® Tab.; Shinpoong Pharm, Seoul, Korea) was administered orally at 35 mg/kg twice, once every two weeks. One month after the last administration, no eggs were observed from the feces and additional fecal examination was performed more than two months later, verifying the completion of treatment.

Case 2

A 3-year-old, 3 kg female cat (domestic shorthair), living in Daegu, Korea, had been vomiting, and proglottids of a tapeworm, approximately 15 cm long, were recovered. Before vomiting, the cat showed symptoms such as anorexia and lethargy without diarrhea. This cat was a stray cat and had been adopted by the current owner and was reared indoors. After adoption, vaccination was not administered. For the diagnosis, a fecal floatation test was performed, and Spirometra eggs were identified. Praziquantel (DS Anthelmine Puppy Tab.; Daesung Microbiological Labs., Uiwang, Korea) (12.5 mg) was administered four times daily. Following the treatment, no additional proglottids of Spirometra were recovered either through vomiting or feces. Subsequently, anorexia and lethargy disappeared. However, an additional fecal flotation test was not performed owing to the owner’s refusal.

For exact species identification, proglottids of adult worms were kept in 70% ethyl alcohol and were submitted to the College of Veterinary Medicine, Chungbuk National University, Cheongju, Korea.

Morphological and molecular identification of Spirometra

Species identification was performed using both morphological and molecular examinations. The size of the proglottid from Case 1 was 5.69 mm (width, standard deviation 0.30) ×0.68 mm (length, standard deviation 0.05) and the proglottid from Case 2 was sized 5.88 mm (width, standard deviation 0.21)×1.26 mm (length, standard deviation 0.13). For each sample, at least 10 gravid proglottids were measured. For morphological analysis, the proglottids of adult worms were stained with acetocarmine, and the morphological characteristics confirmed the parasite belonging to Spirometra sp. Additionally, molecular techniques were applied to target cox1 gene analysis. In brief, genomic DNA of adult worms was extracted from the proglottids using the QIAamp® DNA Mini Kit (Qiagen, Hilden, Germany) according to the manufacturer’s instructions. The complete sequence of the Spirometra cox1 gene was amplified by PCR using the AccuPower HotStart PCR Premix kit (Bioneer, Daejeon, Korea), as previously described [12]. The amplified PCR products were sent to Macrogen (Daejeon, Korea) for sequencing, and two additional internal primers were used (forward: GTT TAC CTC GGC GTG TTT GT; reverse: ATC ACC ACC ACC CAA AGG AT).

Using direct sequencing, two complete Spirometra sp. cox1 sequences (1,566-bp) were obtained. Based on the phylogenetic analysis, both Spirometra sp. belonged to Type I (Fig. 2), as suggested by Yamasaki et al. [11]. The phylogenetic tree was constructed using MEGA based on the Maximum Likelihood method with 500 bootstrap replications. Nucleotide analysis showed that the sequences in this study shared 99.7% identity with each other, and BLASTn revealed a high genetic identity of 99.7% and 99.4%, respectively, to S. decipiens (MT122766) from the USA. The sequences identified in this study were submitted to the GenBank database MW031094-MW031095.

Fig. 2

Phylogenetic relationship of Spirometra sp. recovered from cats in Korea based on the complete cytochrome c oxidase subunit 1 gene (1,566 bp). The trees were constructed using MEGA 7.0 using the Maximum Likelihood method with 500 replications. Diphyllobothrium was used as outgroups. The sequences identified in this study are indicated by arrows. Bootstrap values of <70 were omitted. Note that the species names in the analysis are as described in the original papers and the clades are designated as described by Yamasaki et al. [11].

DISCUSSION

The nationwide distribution of Spirometra spp. in humans and animals in Korea is well known [2,4]. In cats, previous studies have investigated the epidemiological status of Spirometra in restricted regions of Korea, e.g., 41.3% (181/438) of S. erinacei in feral cats in Busan [17], 15.8% (34/215) of S. erinacei in feral cats in other regions [16], and 41.5% (17/41) of S. erinacei in stray cats in Seoul [15]. However, these studies assessed Spirometra spp. based on microscopic examination and did not obtain corresponding molecular data. Therefore, additional data on the morphology of adult worms and molecular information are required for clear species identification. [2]. Additionally, to the best of our knowledge, none of the previous studies have reported clinical spirometrosis or sparganosis in animals in Korea.

Previous studies conducted in various countries have reported sparganosis in cats [7,10,19]. However, there are limited reports on the clinical cases of spirometrosis in cats [13]. Spirometrosis is known to cause gastrointestinal symptoms, including vomiting, diarrhea, and weight loss. However, not all infected cats show clinical symptoms [10,11,13]. In our cases, the cat in Case 1 was initially diagnosed as having intestinal bowel disease, which has clinical symptoms similar to those of spirometrosis. The cat had been regularly treated with preventive medicine (Advocate for cat, Bayer). However, it does not contain effective components against cestodes.

In this report, both cats were strays, who are highly potential carriers of different pathogens. However, the cats were reared indoors after they were adopted by their owners. Therefore, we suspect that the cats had been infected by the plerocercoid of Spirometra before adoption. Spirometrosis can be treated with praziquantel and mebendazole [20]. In Case 1, the initial treatment was attempted with a spot-on solution type; however, it was unsuccessful. After oral treatment with praziquantel, the cat was successfully cured. In Case 2, unfortunately, after the oral treatment with praziquantel, the owner refused permission to re-examine; therefore, we failed to perform a follow-up of the case.

Stray cats are important reservoir hosts for helminth, and cestodes infecting felids include Echinococcus, Taenia, Dipylidium, Mesocestoides, Diphyllobothrium, and Spirometra [17,21]. The diagnosis of these parasites at the genus level can be achieved by coproscopic examination. Diphyllobothrium has a similar shaped egg as Spirometra; however, Spirometra eggs have more pointed poles. Exact species identification requires morphological analysis of adult worms or molecular analysis.

In conclusion, this study is the first to report clinical spirometrosis in 2 cats in Korea. Considering the low pathogenicity of spirometrosis in cats, it is uncommon for cats to show clinical symptoms. This report suggests that regular monitoring of health and deworming in companion animals is needed, even when animals are well cared for with regular preventive medical treatment. Additionally, spirometrosis should be considered for differential diagnosis in cases of gastrointestinal symptoms in Spirometra endemic areas.