Nine-year seroepidemiological study of severe fever with thrombocytopenia syndrome virus infection in feral horses in Cape Toi, Japan.

Severe fever with thrombocytopenia syndrome (SFTS) is a fatal zoonosis caused by ticks in East Asia. As SFTS virus (SFTSV) is maintained between wildlife and ticks, seroepidemiological studies in wildlife are important to understand the behavior of SFTSV in the environment. Miyazaki Prefecture, Japan, is an SFTS-endemic area, and approximately 100 feral horses, called Misaki horses (Equus caballus), inhabit Cape Toi in Miyazaki Prefecture. While these animals are managed in a wild-like manner, their ages are ascertainable due to individual identification. In the present study, we conducted a seroepidemiological survey of SFTSV in Misaki horses between 2015 and 2023. This study aimed to understand SFTSV infection in horses and its transmission to wildlife. A total of 707 samples from 180 feral horses were used to determine the seroprevalence of SFTSV using enzyme-linked immunosorbent assay (ELISA). Neutralization testing was performed on 118 samples. In addition, SFTS viral RNA was detected in ticks from Cape Toi and feral horses. The overall seroprevalence between 2015 and 2023 was 78.5% (555/707). The lowest seroprevalence was 55% (44/80) in 2016 and the highest was 92% (76/83) in 2018. Seroprevalence was significantly affected by age, with 11% (8/71) in those less than one year of age and 96.7% (435/450) in those four years of age and older (p < 0.0001). The concordance between ELISA and neutralization test results was 88.9% (105/118). SFTS viral RNA was not detected in ticks (n = 516) or feral horses. This study demonstrated that horses can be infected with SFTSV and that age is a significant factor in seroprevalence in wildlife. This study provides insights into SFTSV infection not only in horses but also in wildlife in SFTS-endemic areas.

Human granulocytic anaplasmosis with rash and rhabdomyolysis: A case report.

Human granulocytic anaplasmosis (HGA) is a tick-borne infection caused by Anaplasma phagocytophilum. Only seven cases of HGA have been reported in Japan to date. We report the case of a 61-year-old female farmer who developed HGA with rash and rhabdomyolysis. The patient had fever and erythema covering the entire body, including the palms. An induration with an eschar was observed on the right leg, indicating that the patient had been bitten by a tick. Elevated serum creatinine and creatinine kinase levels and hematuria indicated rhabdomyolysis. We suspected Japanese spotted fever, a tick-borne illness caused by Rickettsia Japonica, and administered minocycline and ciprofloxacin for a week. Transient neutropenia and thrombocytopenia were observed, but the symptoms improved. Polymerase chain reaction (PCR) and antibody tests for R. japonica and Orientia tsutsugamushi, which causes scrub typhus, were both negative. The PCR test for severe fever with thrombocytopenia syndrome virus was also negative. Antibodies against A. phagocytophilum-related proteins were detected by western blotting, indicating seroconversion of IgG with paired serum samples, and the patient was diagnosed with HGA. HGA should be suspected in acute febrile patients with a history of outdoor activity and cytopenia, with or without a rash. A testing system and the accumulation of cases in Japan are necessary for the early diagnosis and appropriate treatment of HGA.

Purification Method of Extracellular Vesicles Derived from Human T-Cell Leukemia Virus Type 1-Infected Cells without Virions.

To mediate intercellular communication, cells produce extracellular vesicles (EVs). These EVs transport many biomolecules such as proteins, nucleic acids, and lipids between cells and regulate pathophysiological actions in the recipient cell. However, EVs and virus particles produced from virus-infected cells are of similar size and specific gravity; therefore, the separation and purification of these two particles is often controversial. When analyzing the physiological functions of EVs from virus-infected cells, the presence or absence of virus particle contamination must always be verified. The human T-cell leukemia virus type 1 (HTLV-1)-infected cell line, MT-2, produces EVs and virus particles. Here, we validated a method for purifying EVs from MT-2 cell culture supernatants while avoiding HTLV-1 viral particle contamination. EV fractions were collected using a combination of immunoprecipitation with Tim-4, which binds to phosphatidylserine, and polymer precipitation. The HTLV-1 viral envelope protein, gp46, was not detected in the EV fraction. Proteomic analysis revealed that EV-constituted proteins were predominant in this EV fraction. Furthermore, the EVs were found to contain the HTLV-1 viral genome. The proposed method can purify EVs while avoiding virus particle contamination and is expected to contribute to future research on EVs derived from HTLV-1-infected cells.

Differences in muscle magnetic resonance imaging findings between anti-signal recognition particle antibody-positive myopathy and anti-aminoacyl-tRNA synthetase antibody-positive myositis.

OBJECTIVES: To compare the findings of muscle magnetic resonance imaging (MRI) between anti-signal recognition particle antibody-positive myopathy (anti-SRP myopathy) and anti-aminoacyl-tRNA synthetase antibody-positive myositis (anti-ARS myositis). METHODS: Of the patients newly diagnosed with polymyositis (PM)/dermatomyositis (DM) and immune-mediated necrotising myopathy (IMNM) admitted to our Department between April 2012 and December 2021, those who met the eligibility criteria of positive for anti-SRP or anti-ARS antibodies and thigh MRI at the time of diagnosis were included. We compared the lesion sites and MRI findings of the thigh muscles that were classified into oedema, fascial oedema, fatty replacement, and muscle atrophy between the three groups of anti-SRP myopathy, anti-Jo-1 antibody-positive myositis, and non-Jo-1 antibody-positive myositis. RESULTS: Of the 98 PM/DM and IMNM patients, five anti-SRP myopathy patients and 11 anti-Jo-1-positive and 22 non-Jo-1 antibody-positive patients with myositis were included. The SRP group showed significantly higher blood levels of myogenic enzymes such as serum creatinine kinase (CK) than the other groups (p=0.01). In thigh MRI findings, despite oedema in most cases in anti-SRP and anti-ARS groups, fascial oedema was identified only in the ARS group, frequently in Jo-1 positive patients in particular. Moreover, gluteus maximus muscle lesions occurred more frequently in the SRP group than in the ARS group (p=0.008). CONCLUSIONS: A comparison of thigh MRI between anti-SRP myopathy and anti-ARS myositis showed different findings and lesion sites reflecting the different pathophysiology that may contribute to their diagnosis.

Coronavirus disease 2019 in a patient with pulmonary fibrosis and emphysema: An autopsy report.

Various diseases (e.g., hypertension and diabetes) are risk factors for the exacerbation of coronavirus 2019 (COVID-19). Patients with chronic obstructive pulmonary disease (COPD) and interstitial lung disease (ILD) tend to develop severe COVID-19. Patients with severe COVID-19 present with acute respiratory distress syndrome (ARDS), and many COVID-19-related ARDS survivors eventually develop fibrosis. However, the appropriate management of patients with COVID-19 and ILD and post-COVID-19 ILD remains unclear. Thus, a better understanding of the pathology that exacerbates COVID-19 in patients with ILD is needed. We report the autopsy results of a patient with COVID-19 and combined pulmonary fibrosis and emphysema, whose lung organization and fibrosis progressed after the acute phase of infection. Histopathological findings suggest that fatal pulmonary fibrosis persists after the negative conversion of SARS-CoV-2. Elucidating the cause of death by autopsy may help determine therapeutic strategies in patients with COVID-19 and ILD. Vaccination and early administration of anti-inflammatory drugs or antifibrotic agents may be crucial for preventing disease progression and fatal lung fibrosis. This report aims to clarify the histopathological features of COVID-19 in patients with ILD via autopsy and discuss treatment strategies.

Luteibacter jiangsuensis blood stream infection: a first case report.

BACKGROUND: Luteibacter jiangsuensis is a gram-negative aerobic bacillus that was first isolated from soil samples at a pesticide factory in China and reported in 2011. Here, we describe the first case of L. jiangsuensis infection in human. CASE PRESENTATION: A 59-year-old Japanese woman undergoing treatment for Crohn's disease was admitted to our hospital with fever. Clinical examination indicated catheter-related bloodstream infection. The catheter was removed and meropenem was initiated. Morphologically identical glucose non-fermentative gram-negative bacilli were detected from two sets of aerobic blood culture and catheter-tip cultures. MALDI-TOF mass spectrometry failed to identify the bacterium, which was later identified as L. jiangsuensis by 16 S rRNA gene sequencing. Antimicrobial susceptibility test revealed that the isolate was resistant to carbapenem, therefore meropenem was switched to intravenous levofloxacin (500 mg/day). After 14 days of treatment with levofloxacin, the patient was discharged. CONCLUSIONS: This is the first case of L. jiangsuensis infection in human. The strain was identified by 16 S rRNA gene sequence analysis.

Performance evaluation of Espline HTLV-I/II, a newly developed rapid immunochromatographic antibody test for different diagnostic situations.

IMPORTANCE: The World Health Organization estimated that 5-10 million people are infected with human T-cell leukemia virus type 1 (HTLV-1). This number is likely to be underestimated because reliable endemic data are available for only approximately 1.5 billion people worldwide. The point-of-care test is a powerful tool for the easy and quick detection of infections without the requirement for expensive instruments and laboratory equipment. Espline HTLV-I/II, a newly developed rapid immunochromatographic antibody test that was evaluated in this study, might significantly advance our understanding of the global epidemiology of HTLV-1 infection.

HAS-Flow May Be an Adequate Method for Evaluating Human T-Cell Leukemia Virus Type 1 Infected Cells in Human T-Cell Leukemia Virus Type 1-Positive Rheumatoid Arthritis Patients Receiving Antirheumatic Therapies: A Retrospective Cross-Sectional Observation Study.

The study aims to assess the usefulness of human T-cell leukemia virus type 1 (HTLV-1)-infected cell analysis using flow cytometry (HAS-Flow) as a monitoring method for adult T-cell leukemia (ATL) development in HTLV-1-positive patients with rheumatoid arthritis (RA) under treatment with antirheumatic therapies. A total of 13 HTLV-1-negative and 57 HTLV-1-positive RA patients participated in this study, which was used to collect clinical and laboratory data, including HAS-Flow and HTLV-1 proviral load (PVL), which were then compared between the two groups. CADM1 expression on CD4+ cells in peripheral blood (PB) was used to identify HTLV-1-infected cells. The population of CADM1+ CD4+ cells was significantly higher in HTLV-1-positive RA patients compared to HTLV-1-negative RA patients. The population of CADM1+ CD4+ cells was correlated with HTLV-1 PVL values. There were no antirheumatic therapies affecting both the expression of CADM1 on CD4+ cells and PVLs. Six HTLV-1-positive RA patients who indicated both high HTLV-1 PVL and a predominant pattern of CADM1+ CD7neg CD4+ cells in HAS-Flow can be classified as high-risk for ATL progression. HAS-Flow could be a useful method for monitoring high-risk HTLV-1-positive RA patients who are at risk of developing ATL during antirheumatic therapies.

Possible Transmission of Severe Fever with the Thrombocytopenia Syndrome Virus to an Individual Who Buried an Infected Cat.

Severe fever with thrombocytopenia syndrome (SFTS) is caused by the severe fever with thrombocytopenia syndrome virus (SFTSV). Although SFTS is a fatal tick-borne zoonosis, it can infect humans without tick bite exposure. Recently, direct transmission of SFTSV from companion pets to humans has become a major problem. We present a case of SFTSV transmission from a dead community cat to a woman who buried the cat in Miyazaki Prefecture, Japan. The community cat died without a diagnosis of SFTS, and the woman buried it without taking any precautions. She developed symptoms of SFTS 9 days later. The woman tested positive for SFTS viral RNA and anti-SFTSV antibodies. The cat's carcass was exhumed, and tissue samples were collected to confirm the viral infection. Numerous copies of viral RNA were detected. The SFTSV M segment sequences in the cat and the woman were 100% homologous. The woman claimed that she had touched blood that had leaked from the cat's body while burying it. However, she could have been infected while transporting the cat to the animal hospital. This study highlights the risk of SFTSV infection from contact with sick or dead community cats.

Nosocomial Severe Fever with Thrombocytopenia Syndrome in Companion Animals, Japan, 2022.

In Japan, 2 cats that underwent surgery in a room where a sick dog had been euthanized became ill within 9 days of surgery. Severe fever with thrombocytopenia syndrome virus was detected in all 3 animals; nucleotide sequence identity was 100%. Suspected cause was an uncleaned pulse oximeter probe used for all patients.

Seroprevalence of severe fever with thrombocytopenia syndrome virus in medium-sized wild mammals in Miyazaki, Japan.

Severe fever with thrombocytopenia syndrome (SFTS) is a fatal emerging tick-borne zoonotic disease caused by the SFTS virus (SFTSV). SFTSV infection in humans and companion animals is a matter of concern in endemic areas. Various wild animals are involved in the transmission cycle of SFTSV with vector ticks. Because the home range of medium-sized wild mammals commonly overlaps with humans' living spheres, this study aimed to reveal the endemicity of SFTSV in such mammals. This study investigated the prevalence of antibodies against SFTSV and viral RNA in medium-sized wild mammals in Miyazaki Prefecture, Japan where human cases have been most frequently reported in Japan and performed a phylogenetic analysis to compare the detected SFTSV with those previously reported. Forty-three of 63 (68%) Japanese badgers (Meles anakuma) and 12 of 53 (23%) Japanese raccoon dogs (Nyctereutes procyonoides viverrinus) had antibodies against SFTSV. Japanese marten (n = 1), weasels (n = 4), and Japanese red fox (n = 1) were negative. Two of 63 (3%) badgers tested positive for SFTSV RNA, whereas the other species were negative. Phylogenetic analysis of the partial nucleotide sequence of SFTSV revealed that viral RNA detected from badgers exhibited 99.8% to 100% similarity to SFTSV, as previously reported in humans, cat, and ticks in the study area. This study demonstrated high seropositivity of antibodies in medium-sized wild mammals and suggested that SFTSV could be shared among these mammals, humans, and companion animals in endemic areas.

Neutralizing mAbs against SFTS Virus Gn Protein Show Strong Therapeutic Effects in an SFTS Animal Model.

Severe fever with thrombocytopenia syndrome (SFTS) is an infectious disease with a high case fatality rate caused by the SFTS virus, and currently there are no approved specific treatments. Neutralizing monoclonal antibodies (mAbs) against the virus could be a therapeutic agent in SFTS treatment, but their development has not sufficiently been carried out. In the present study, mouse and human mAbs exposed to the viral envelope proteins Gn and Gc (16 clones each) were characterized in vitro and in vivo by using recombinant proteins, cell culture with viruses, and an SFTS animal model with IFNAR-/- mice. Neutralization activities against the recombinant vesicular stomatitis virus bearing SFTS virus Gn/Gc as envelope proteins were observed with three anti-Gn and six anti-Gc mAbs. Therapeutic activities were observed among anti-Gn, but not anti-Gc mAbs with neutralizing activities. These results propose an effective strategy to obtain promising therapeutic mAb candidates for SFTS treatment, and a necessity to reveal precise roles of the SFTS virus Gn/Gc proteins.

Effect of HTLV-1 Infection on the Clinical Course of Patients with Rheumatoid Arthritis.

Human T-cell leukemia virus type 1 (HTLV-1) is the causative agent of adult T-cell leukemia/lymphoma (ATL) and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). The effects of HTLV-1 on health are not fully elucidated. Epidemiological studies have shown that the prevalence of HTLV-1 infection is high in patients with rheumatic diseases. The prevalence of comorbidities, such as Sjögren's syndrome and rheumatoid arthritis (RA), is higher in patients with HAM/TSP than the in general population. Studies have shown the effects of HTLV-1-infection on the clinical course of RA. Major questions on the association between HTLV-1 infection and RA: (1) Is it possible that HTLV-1 infection causes RA? (2) Do patients with RA who are infected with HTLV-1 have different clinical features? (3) Are immunosuppressants associated with an increased prevalence of HAM/TSP or ATL in RA patients with HTLV-1 infection? Is ATL an immunosuppressive therapy-associated lymphoproliferative disorder? No large-scale studies have investigated the incidence of ATL in patients with RA. However, several studies have reported the development of ATL in patients with RA who have HTLV-1 infection. This review aimed to shed light on the association between HTLV-1 infection and RA and summarize the unmet medical needs of RA patients with HTLV-1 infection.

Neuropsychiatric Systemic Lupus Erythematosus with Cerebral Vasculitis and Lupus Nephritis Successfully Treated with High-dose Glucocorticoids and Mycophenolate Mofetil.

Neuropsychiatric systemic lupus erythematosus (NPSLE) with cerebral vasculitis is rare, and its prognosis is unfavorable. High-dose glucocorticoids and cyclophosphamide are widely used for the treatment of NPSLE, but cyclophosphamide has a risk of cervical intraepithelial neoplasia and ovarian insufficiency, which may discourage its use in young women. We experienced a case of NPSLE with cerebral vasculitis and lupus nephritis that responded successfully to glucocorticoids and mycophenolate mofetil (MMF). MMF might be a treatment option for NPSLE without concern for reproductive toxicity. However, there are only a few reports on the efficacy of MMF in NPSLE, and further investigations are needed.

High incidence of serious infections requiring hospitalisation in human T-cell leukaemia virus type 1-positive rheumatoid arthritis: A case-controlled observational study.

OBJECTIVES: We aimed to assess the clinical features of human T-cell leukaemia virus type 1 (HTLV-1)-positive rheumatoid arthritis (RA) patients. Furthermore, we investigated the impact of HTLV-1 infection on incidences of serious infections requiring hospitalisation (SIH) and malignancies. METHODS: A total of 150 sex- and age-matched HTLV-1-negative and 50 HTLV-1-positive RA patients were enrolled from the HTLV-1 RA Miyazaki Cohort Study. Clinical and laboratory data were collected from this cohort database. The incidence rate (IR) for SIH and malignancies from 2015 to 2020 was analysed. RESULTS: The median age and female ratio in the study population were 70 years old and 80%, respectively. Although no differences were found in inflammatory marker values between the two groups, the patient global assessment and Health Assessment Questionnaire scores were higher in HTLV-1-positive RA patients. In HTLV-1-negative RA patients, the IR for SIH was 6.37/100 person-years (PY) and 1.32/100 PY for malignancies. In HTLV-1-positive RA patients, SIH occurred in 11.1/100 PY and malignancies in 2.46/100 PY. The crude IR ratio comparing SIH between two groups was 1.74 (95% confidence interval, 1.04-2.84), which was a significant increase. CONCLUSIONS: HTLV-1-positive RA patients may worsen RA symptoms. HTLV-1 may be a risk factor for SIH.

Severe Fever with Thrombocytopenia Syndrome Accompanied by Invasive Pulmonary Aspergillosis: An Autopsy Case.

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging tickborne infectious disease in China, Korea, and Japan caused by the SFTS virus (SFTSV). SFTS has a high mortality rate due to multiorgan failure. Recently, there are several reports on SFTS patients with mycosis. Here, we report a middle-aged Japanese SFTS patient with invasive pulmonary aspergillosis (IPA) revealed by an autopsy. A 61-year-old man with hypertension working in forestry was bitten by a tick and developed fever, diarrhea, and anorexia in 2 days. On day 4, consciousness disorder was appearing, and the patient was transferred to the University of Miyazaki Hospital. A blood test showed leukocytopenia, thrombocytopenia, as well as elevated levels of alanine aminotransferase, aspartate aminotransferase, lactate dehydrogenase, and creatine kinase. The SFTSV gene was detected in serum using a reverse-transcription polymerase chain reaction. On day 5, respiratory failure appeared and progressed rapidly, and on day 7, the patient died. An autopsy was performed that revealed hemophagocytosis in the bone marrow and bleeding of several organs. IPA was observed in lung specimens. SFTSV infection may be a risk factor for developing IPA. Early diagnosis and treatment of IPA may be important in patients with SFTS.

Corticosteroids May Have Negative Effects on the Management of Patients with Severe Fever with Thrombocytopenia Syndrome: A Case-Control Study.

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging viral hemorrhagic fever in China, Korea, and Japan. To date, no standardized treatment protocol for SFTS has been established. Corticosteroids (CS) may be administered to patients with SFTS and hemophagocytic syndrome, but its effectiveness and safety are still debatable. We conducted a retrospective case series review at four medical facilities in Miyazaki, Japan. Based on the medical records, clinical data, including the patients background, symptoms, physical findings, laboratory data at initial presentation, treatment, and outcome, were compared between the CS-treated and the non-CS-treated group. A total of 47 patients with confirmed SFTS in each hospital were enrolled in this study; there were 14 fatal cases and 33 nonfatal cases. The case fatality ratio was 29.8%. After adjusting patients' background by propensity score matching, the case fatality ratio was higher (p = 0.04) and complications of secondary infections, including invasive pulmonary aspergillosis, tended to be more frequent (p = 0.07) in the CS-treated group than in the non-CS-treated group. These data suggested that administration of CS to patients with SFTS should be carefully considered.

Survey of actual conditions of erythema marginatum as a prodromal symptom in Japanese patients with hereditary angioedema.

BACKGROUND: Hereditary angioedema (HAE) is a rare but life-threatening condition. HAE types I and II (HAE-1/2) result from C1-inhibitor (C1-INH) deficiency. However, recent genetic analysis has established a new type of HAE with normal C1-INH (HAEnC1-INH). The mutations of factor XII, plasminogen, angiopoietin 1, and kininogen 1 genes may be the cause of HAEnC1-INH. Nevertheless, other causative molecules (HAE-unknown) may be involved. The Japanese therapeutic environment for HAE has been improving owing to the self-subcutaneous injection of icatibant, which was approved for the treatment of acute attack and enables early therapy. Erythema marginatum (EM) is a visible prodromal symptom which occasionally occurs prior to an angioedema attack; hence, recognizing the risk of an acute attack is important for early treatment. However, the detailed characteristics of EM remain unclear. In this study, we first investigated the clinical manifestations of EM in Japanese patients with HAE. METHODS: A 20-point survey was developed and distributed to 40 physicians to gather clinical data on EM from patients with HAE. RESULTS: Data on 68 patients with HAE (58 patients with HAE-1/2 and 10 patients with HAE-unknown) were collected. Of the patients with HAE-1/2, 53.4% experienced EM, whereas 43.1% did not. The forearm was the most frequent area of EM (64.5%), followed by the abdomen (29.0%) and upper arm and precordium (19.3%). Of the HAE-1/2 patients with EM, 41.9% always had angioedema following EM, while 29.0% always had colocalization of EM with angioedema. Moreover, 3.2% showed a correlation between the awareness of EM and severity of an angioedema attack. In 60.9% of HAE-1/2 patients with EM, the interval between the awareness of EM and appearance of angioedema was <3 h. Of the patients with HAE-unknown, 30.0% also experienced EM. CONCLUSION: We confirmed that more than one-half of Japanese patients with HAE-1/2 and one-third of those with HAE-unknown develop EM as the prodromal symptom of an angioedema attack. Physicians should communicate the significance of EM to patients with HAE to prepare them for possible imminent attacks.

Effectiveness and safety of non-tumor necrosis factor inhibitor therapy for anti-human T-cell leukemia virus type 1 antibody-positive rheumatoid arthritis.

OBJECTIVES: Our previous study showed that the effectiveness of tumor necrosis factor (TNF) inhibitors was attenuated in anti-human T-cell leukemia virus type 1 (HTLV-1) antibody-positive patients with rheumatoid arthritis (RA). We aimed to evaluate the effectiveness and safety of non-TNF inhibitors in anti-HTLV-1 antibody-positive patients with RA. METHODS: We reviewed patients with RA who received abatacept or tocilizumab as the first biologic agent. We used the data of patients treated with TNF inhibitors from our previous study to compare the effectiveness between the anti-HTLV-1 antibody-positive patients treated with TNF inhibitors and non-TNF inhibitors using the inverse probability of treatment weights (IPTW) method. RESULTS: A total of 359 patients were divided into anti-HTLV-1 antibody-negative and -positive patients of 332 and 27, respectively. No statistically significant difference was observed in the change in the clinical disease activity index between the anti-HTLV-1 antibody-positive and -negative patients. The results using the IPTW method showed a significant association between the non-TNF inhibitors treatment and a better response. None of the patients developed adult T-cell leukemia/lymphoma or HTLV-1-associated myelopathy/tropical spastic paraparesis during the 24 weeks. CONCLUSION: Our results indicate that non-TNF inhibitors treatment is safety, and the effectiveness is not attenuated also in anti-HTLV-1 antibody-positive patients.

Strongyloides stercoralis colitis in a patient positive for human T-cell leukaemia virus with rheumatoid arthritis during an anti-rheumatic therapy: a case report.

An elderly woman with rheumatoid arthritis (RA) presented with a chief complaint of abdominal pain and diarrhoea while undergoing treatment with low-dose corticosteroids and abatacept. Endoscopic and histopathological findings revealed manifestations of ulcerative colitis (UC). An intermediate dose of corticosteroids and 5-aminosalicylic acid were administered. Abatacept was discontinued; the anti-TNF biologic, golimumab, was administered for treatment of both RA and UC. However, colitis worsened in response to this therapeutic regimen. Colonoscopy revealed severe mucosal lesions; larvae were detected in samples taken from multiple shallow mucosal ulcers. The patient was diagnosed with Strongyloides stercoralis colitis based on the results of an anti-parasite antibody test and examination of the larval DNA. Furthermore, serology revealed a positive test for antibodies against human T-cell leukaemia virus type 1 (HTLV-1). Immunosuppressive treatment was terminated; ivermectin was administered, which resulted in improvements in colitis symptoms within a few weeks. There are several published reports describing S. stercoralis colitis as a lethal mimic of UC. Corticosteroid and anti-TNF therapies have been reported as among the major risk factors associated with strongyloidiasis in patients with HTLV-1 infection. Therefore, HTLV-1 and Strongyloides infections may be considered in cases of new-onset gastrointestinal symptoms during immunosuppressive therapy, particularly in HTLV-1-endemic regions.